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Antimicrobial Agents and Chemotherapy, October 1999, p. 2484-2492, Vol. 43, No. 10
0066-4804/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Development of a New Experimental Model of Penicillin-Resistant
Streptococcus pneumoniae Pneumonia and Amoxicillin
Treatment by Reproducing Human Pharmacokinetics
Lionel
Piroth,1
Laurent
Martin,2
Alexis
Coulon,1
Catherine
Lequeu,1
Michel
Duong,1
Marielle
Buisson,1
Henri
Portier,1 and
Pascal
Chavanet1,*
Service des Maladies Infectieuses et
Tropicales, Microbiologie Médicale et Moléculaire (EA562),
Hôpital du Bocage,1 and Service
d'Anatomie Pathologique, Centre Hospitalier Universitaire de
Dijon,2 Dijon Cedex, France
Received 25 September 1998/Returned for modification 20 February
1999/Accepted 16 June 1999
 |
ABSTRACT |
The increase of penicillin-resistant Streptococcus
pneumoniae (PRSP) pneumonia results in a greater risk of
antibiotic treatment failure. In vitro data are not sufficient
predictors of clinical efficacy, and animal models may be
insufficiently contributive, since they often use immunocompromised
animals and do not always respect the human pharmacokinetics of
antibiotics. We developed an experimental PRSP pneumonia model in
immunocompetent rabbits, by using intrabronchial instillation of PRSP
(MIC = 4 mg/liter), without any adjuvant. This reproducible model
was used to assess amoxicillin efficacy by reproducing human serum
pharmacokinetics following 1-g oral or intravenous administrations of
amoxicillin every 8 h. Evaluation was performed by using clinical,
CT scan, macroscopic, histopathologic, and microbiological criteria.
Experimental pneumonia in untreated rabbits was similar to untreated
severe human bacteremic untreated pneumonia; in both rabbits and
humans, (i) cumulative survival was close to 50%, (ii) red or gray
lung congestion and pleuritis were observed, and (iii) lung and spleen concentrations reached 5 and 4 log10 CFU/g. A 48-h
treatment resulted in a significant bacterial clearance in the lungs
(1.53 versus 5.07 log10 CFU/ml, P < 0.001) and spleen (1.00 versus 4.40 log10 CFU/ml,
P < 10
6) and a significant decrease in
mortality (0% versus 50%, P = 0.02) in treated
versus untreated rabbits. No difference was observed on macroscopic and
histopathologic lesions between treated and untreated rabbits
(P = 0.36 and 0.78, respectively). Similar results were obtained by using a fully penicillin-susceptible S. pneumoniae strain (MIC = 0.01 mg/liter). Our findings
suggest that (i) this new model can be contributive in the evaluation
of antibacterial agents and (ii) 1 g of amoxicillin three times a
day may be sufficient to treat PRSP pneumonia in immunocompetent humans.
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INTRODUCTION |
Invasive Streptococcus
pneumoniae infection is a worldwide problem. S. pneumoniae is the most common cause of bacterial pneumonia, leading to significant morbidity and mortality rates which vary around
25% (5, 37, 51). Since the first reports three decades ago
of strains of S. pneumoniae with a decreased susceptibility to penicillin, there have been increasing reports of pneumococcal infections caused by strains with high levels of resistance to penicillin and to multiple antibiotics (5, 25, 36, 37, 51).
Clinical treatment failures in patients with infections caused by
penicillin-resistant S. pneumoniae point out the interest for more evaluation of therapeutic efficacy. Indeed, in vitro data are
only mildly helpful because of their incapacity to predict clinical
therapeutic success (5). Furthermore, human therapeutic trials are very difficult to conduct, because of the impossibility of
clinically evaluating the situation, due to penicillin-resistant pneumococcal infection, and the great prevalence of precessive antibiotherapy, which reduces the probability of isolating
penicillin-resistant S. pneumoniae, even after treatment
failure. Consequently, animal models could contribute to predicting
antibiotic treatment efficacy in such infections.
Several penicillin-resistant S. pneumoniae animal models
exist (1-3, 6, 9, 14, 17, 18, 33, 34, 39, 41-43, 45, 46).
However, the greatest difficulty for these models was the inability to
infect healthy animals with penicillin-resistant S. pneumoniae strains. Consequently most of the available models were
developed in immunocompromised mice (1-3, 6, 9, 14, 17, 33, 34,
42, 43) and young rodents (9, 41, 45, 46) or used
adjuvant to enhance bacterial virulence (9, 18, 39, 41).
Moreover, differences between animal and human pharmacokinetics constituted another important limit.
In the present study, we developed a model of experimental
penicillin-resistant S. pneumoniae pneumonia using
nonimmunosuppressed animals (adult New Zealand rabbits), reproducing
human pathology with an inoculum free of any adjuvant. We also
reproduced human serum pharmacokinetics following amoxicillin
administration. In a third phase, we conducted an experimental
therapeutic study in order to evaluate the amoxicillin (3 g/day)
efficacy on bacterial clearance in penicillin-resistant S. pneumoniae pneumonia, corresponding to the dose recommended in
France for pneumonia treatment (44).
(This work was presented in part at the 38th Interscience Conference on
Antimicrobial Agents and Chemotherapy, San Diego, Calif., 1998.)
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MATERIALS AND METHODS |
Microorganisms.
Two S. pneumoniae strains
isolated from the blood of patients with pneumonia were used (kindly
provided by Geslin of the Centre National de Référence des
Pneumocoques, Créteil, France). The first strain (strain 195, serotype 19) was fully susceptible to penicillin (MIC = 0.01 mg/liter). The second strain (strain 16089, serotype 9V) was highly
resistant to penicillin (MIC = 4 mg/liter) and less susceptible to
amoxicillin (MIC = 2 mg/liter) and ceftriaxone (MIC = 1 mg/liter). Purity was confirmed throughout the study by Gram staining
and colony morphology. Working stock cultures were kept frozen at
70°C in a 15% glycerol supplemented brain heart infusion
(BioMérieux Laboratories, Marcy l'Etoile, France). In order to
maintain virulence, stock cultures were changed every month by using
the colonies isolated from rabbits with untreated S. pneumoniae pneumonia.
Before each experiment, several S. pneumoniae strains from
one aliquot (per strain) were inoculated into brain heart infusion, cultured on agar plates, and incubated for 24 h at 37°C in 5% CO2. Twenty-five to 30 colonies were taken and inoculated
into 9 ml of brain heart infusion, incubated for 6 h at 37°C,
and then cultured on agar plates for 18 h at 37°C in 5%
CO2. This culture was diluted in physiologic saline in
order to obtain final concentrations of 7, 8.5, and 10 log10 CFU/ml. No adjuvant was used. These concentrations were first determined by using optic density measure, in reference to a
standard curve, and confirmed by using successive dilution cultures.
Animals.
Male New Zealand White rabbits (body weight, 2.7 to
3.0 kg) were obtained from Elevage Scientifique des Dombes (Romans,
France). These animals were not immunosuppressed and had a sanitary
status of virus antibody free and specific pathogen free. They were
placed in individual cages and were nourished ad libitum with drinkable water and feed, according to current recommendations.
Experimental pneumococcal pneumonia in rabbits.
The animals
were anesthetized intramuscularly with 1.5 ml of a mixture of ketamine
(500 mg/ml) and xylazine (2.75 mg/ml). A silicone catheter was
introduced into the jugular vein, through a lateral incision of the
neck, and then subcutaneously tunneled through the interscapular area
(50). This catheter was introduced in order to subsequently
infuse antibiotics at human pharmacokinetic rates.
Twenty-four hours later, the rabbits were anesthetized intravenously by
using 0.8 ml of the ketamine-plus-xylazine mixture and then by a few
milliliters of propofol as needed. Under view control, a silicone
catheter (Sigma Medical, Nanterre, France) was introduced through the
vocal cords into the trachea and pulled till it reached the bronchia.
Freshly prepared pneumococcal inoculum (0.5 ml) was then gently flushed
through this catheter. The endobronchial catheter was then immediately
removed after the inoculum instillation, and the animals were placed
upright for 15 s to facilitate distal alveolar migration by
gravity. Using the same experimental conditions, some rabbits were
inoculated with heat-killed penicillin-resistant S. pneumoniae as negative controls.
Experimental pneumonia examination.
For each strain and
inoculum, experimental pneumonia was evaluated by using invasive and
noninvasive criteria. For a few animals, a thoracic evaluation CT scan
was also performed. For each rabbit, the main evaluation took into
account pulmonary injury levels and microbiological findings in each
lobe of the lungs and the spleen. These organs were taken either after
sacrifice or after pneumonia-related death. Animal sacrifice was
performed after anesthesia by using overdoses of thiopental. For each
dead rabbit (sacrificed or pneumonia related), an exsanguination by
heart puncture was performed. The thorax was opened, and the existence of pleural effusion was noted. The lungs were then dissected, free from
the trachea and other structures, in sterile fashion and put on a
sterile gauze for at least 5 min, to allow residual pulmonary blood
absorption. A laparotomy was then performed, and the spleen was
aseptically removed.
For each pulmonary lobe, the macroscopic aspect was noted by using a
scoring grid based upon human morphologic findings (Table
1) (
32). An overall
macroscopic score was calculated as the
sum of all lobar macroscopic
scores, plus 2 points in the case
of pleural effusion (range, 0 to 39 points).
Two parts of each lobe were taken, fixed in 10% neutral buffered
formalin, and thereafter embedded in paraffin.
Hematoxylin-eosin-safranin
staining was applied to 5-µm-thick
sections. Light microscopy
examination was performed by a pathologist
who was not in possession
of the experimental, macroscopic, and
microbiological data. A
scoring grid system was also used, based upon
human histopathologic
data (
31,
40) (Table
2). An overall histopathologic score
was
calculated for each rabbit as the sum of each lobar histopathologic
score (range, 0 to 35 points).
Each pulmonary lobe was weighed and homogenized in sterile water. The
spleen was prepared under the same conditions. Bacteria
were counted in
a sample of this crude homogenate by plating 10-fold
dilutions on sheep
blood agar and incubating the plates for 24
to 48 h at 37°C.
Samples of pleural effusions were directly plated
and cultured in the
same conditions. Bacterial concentrations
in each lobe or in the spleen
were determined after adjusting
for weight. The threshold value was 1 log
10 CFU/ml. For each rabbit,
the mean pneumococcal
pulmonary concentration was calculated according
to each lobar
bacterial concentration with lobar weight (e.g.,
mean
concentration =
[lobar concentration × lobar
weight]/
lobar
weights).
Simulation of human amoxicillin pharmacokinetics in rabbits.
Amoxicillin (Clamoxyl; SmithKline Beecham Laboratories, Nanterre,
France) was reconstituted from laboratory powder of known potency,
according to the manufacturer's instructions, just before each
experiment. A 20-mg/kg of body weight bolus was infused intravenously in four rabbits. Arterial blood punctures were performed at 0, 5, 10, 15, 20, 30, 45, 60, 90, and 120 min after injection. Sera from these
blood samples were stored at 70°C till assay. Amoxicillin concentrations in the blood and lungs were determined by the disk plate
bioassay method (10). The bioassay microorganism was
Micrococcus luteus ATCC 9341, and the growth medium was
antibiotic medium no. 11 (Difco Laboratories, Detroit, Mich.). Standard
curves were established with solutions of amoxicillin (progression from
0.5 to 8 mg/liter) in sterile water. The linearity of the standard curves used for the disk plate bioassays was at least 0.98 (r2). The amoxicillin concentrations in the
serum and lungs were derived from the standard curves. The serum and
lung samples were diluted in sterile water, as their concentrations
would be within range of those on the standard curve. Results were
expressed as micrograms per milliliter of blood or per gram of lung.
New batches of standard samples were assayed for each experiment, and
concentrations were assayed in duplicate. The between-day and
within-day coefficients of variation for replicates were equal to 3.8 and 7.0%, respectively.
For each rabbit, a logarithmic regression of measured concentrations
versus time during the elimination phase (on the basis
of an open
bicompartmental model) was performed by using the least-squares
method.
Such a regression led to the determination of the
slope
and the B
constant of the elimination phase. The same method was
used to
determine the
slope and the A constant of the distribution
phase,
with the exception that values calculated according to
the elimination
phase equation were withdrawn from measured concentrations
(
30). The correlation coefficient (
r) and the
observed versus
expected area under the curve ratio (calculated by
using the trapezoidal
rule) were used to validate the obtained model
(
30). Concentrations
in serum following an intravenous
injection of amoxicillin could
be calculated from the following
equation: concentration in serum
= A.e
t + B.e
t, where
t corresponded to
the time elapsed since the bolus was
injected. From these data, the
following constants were deduced:
apparent volumes of distribution
(vascular and extravascular),
elimination constant, and
intercompartmental rate constants (
22,
27).
The objectives were to simulate human pharmacokinetics following the
administration of 1 g of amoxicillin, either orally (oral
simulation) (
13) or intravenously (intravenous simulation)
(
12,
24). Because of faster amoxicillin elimination in
rabbits than
in humans, a variable flow rate infusion with successive
levels
was used. Briefly, by using the amoxicillin pharmacokinetics
constants
in rabbits, determined as described above, it was possible to
calculate both vascular and extravascular concentrations following
each
constant rate infusion, given any initial condition (i.e.,
with an
empty model or not), by using the model developed by Hull
(
27). Indeed, intercepts A and B from the plasmatic
concentration
equation depend in part on the antibiotic dose given
either in
bolus or by continuous infusion. Thus, it was possible, by
reversing
the formulas, to calculate the infusion rate necessary to
yield
a specific plasmatic concentration. This method has already been
successfully used in humans (
26). We developed a computer
program
to facilitate and to automate
calculations.
For each experiment, a computer-controlled pump containing amoxicillin
was connected to the central venous catheter. This
protected connection
allowed free circulation and free food access
to the rabbits. Infusion
rates were controlled by programmable
computer software (Softpump;
World Precision Instruments, Sarasota,
Fla.). Infusion rates were
modified every 30 min (oral simulation)
and every 5 min (intravenous
simulation).
Twenty-two rabbits were used for the simulation of amoxicillin human
pharmacokinetics, most of them being infected with
S. pneumoniae. To control the quality of simulations, arterial blood
samples were regularly taken during simulation at 5, 10, 15, 20,
30, 40, 50, 60, 75, 90, 120, 150, and 180 min for intravenous
simulation
and at 30, 60, 90, 120, 150, 180, 210, 240, 270, 300,
330, and 360 min
for oral simulation. Rabbits were sacrificed
at variable times, and
lung samples were taken for amoxicillin
assay. Serum and lung
homogenates were stored at
70°C until assay.
Comparison between
observed and expected values was performed
by using both a correlation
coefficient and the expected versus
observed area under curve
ratios.
Human-simulated amoxicillin treatment.
Eighteen rabbits were
randomly assigned just before inoculation with 0.5 ml of 10 log10 CFU of penicillin-resistant S. pneumoniae (strain 16089) per ml to three arms: (i) untreated (n = 8), (ii) oral amoxicillin treated (n = 5), and
(iii) intravenous amoxicillin treated (n = 5). The same
procedure was used in a second group inoculated with 0.5 ml of 10 log10 CFU of penicillin-susceptible S. pneumoniae (strain 195) per ml. Human-like amoxicillin treatment was started 4 h after inoculation. Four doses of 1 g of
amoxicillin (every 8 h) were simulated in the oral-treated arms,
while five doses of 1 g of amoxicillin (every 8 h) were
simulated in the intravenous-treated arm. Blood samples were taken in
treated rabbits to assess the quality of the human pharmacokinetics
simulation. All treated rabbits still alive were sacrificed 10 h
(intravenous simulation, five cycles) to 14 h (oral simulation,
four cycles) after the last computer-controlled amoxicillin infusion,
i.e., around 48 h after inoculation. Untreated rabbits still alive
were also sacrificed 48 h after inoculation. Amoxicillin
concentrations in the serum and lungs were systematically assayed at
death time in treated rabbits. Evaluation criteria were survival,
macroscopic, and histopathologic scores and pneumococcal concentrations
in lungs and spleen at death time for all the rabbits (sacrificed or
dead from pneumonia).
Statistics.
The results were expressed as the mean or
percentage ± standard deviation (SD). Differences between
quantitative values were analyzed by using the Mann-Whitney
nonparametric test. To compare relationships between quantitative
values, the r and r2 values were
calculated by the linear regression model.
Survival analysis was performed using the Kaplan-Meier method.
Significant events were pneumonia-related deaths, and sacrifices
were
considered as censored events. Comparisons between curves
were made by
using the log-rank test or Peto's Khi2 test as
needed.
In the experimental pneumonia treatment phase, proportions were
analyzed as quantitative values by using angular transformation.
After
verification of variance homogeneity by using Hartley's
table,
continuous variables were analyzed with one-way analysis
of variance.
In case of a significant test, post hoc analysis
comparing results for
each treated arm versus the untreated arm
was conducted by using
Dunnett's test. For all the tests, a
P value of <0.05 was
considered
significant.
| |
RESULTS |
Experimental pneumococcal pneumonia in rabbits.
Cumulative
survival rates of rabbits with experimental pneumonia produced by
inoculation of penicillin-resistant S. pneumoniae (strain
16089) at 7, 8.5, and 10 log10 CFU/ml, compared with
penicillin-susceptible S. pneumoniae (strain 195) at 10 log10 CFU/ml, are shown in Fig. 1. With the inoculum of 10 log10 CFU/ml, the first pneumonia-related deaths occurred
6 h after inoculation, most of them during the first 72 h,
with very few events after this time. With the inocula of 7 and 8.5 log10 CFU/ml, no pneumonia-related deaths were observed. So
there was a significant difference between the cumulative survival observed after inoculation of 7 or 8.5 log10 CFU/ml and
that observed with 10 log10 CFU of penicillin-resistant
S. pneumoniae per ml (7 versus 10 log10 CFU/ml,
P < 0.05, log-rank test, and 8.5 versus 10 log10 CFU/ml, P < 0.05, log-rank test).
There was no difference between cumulative survival observed
after inoculation with 10 log10 CFU of
penicillin-resistant S. pneumoniae per ml and 10 log10 CFU of penicillin-susceptible S. pneumoniae per ml (P = 0.46, Peto's Khi2 test).
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FIG. 1.
Cumulative survival of rabbits with penicillin-resistant
(strain 16089) and penicillin-susceptible (strain 195) S. pneumoniae experimental pneumonia, according to inoculum
concentration (10 log10 versus 7 or 8.5 log10
CFU/ml, P < 0.05, log-rank test). Symbols:
-----, strain 16089 (inoculum, 10 log10);  , strain 195 (inoculum, 10 log10);
----, strain 16089 (inoculums, 7 and
8.5 log10).
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Inoculation of 7 and 8.5 log
10 CFU of penicillin-resistant
S. pneumoniae per ml induced few to moderate
macroscopic and histopathologic
lesions and mild bacterial
concentrations (data not shown). Evolutions
of macroscopic,
histopathologic, and bacterial concentrations
observed with 10 log
10 CFU of penicillin-resistant
S. pneumoniae per ml inocula are shown in Fig.
2. Four
hours after inoculation,
a significant bacteremic pneumonia was already
observed, with
pneumococcal concentrations reaching 5 log
10
CFU/g in lungs and
3 log
10 CFU/g in the spleen.
Histopathologic and macroscopic scores
were close to 10 at this time.
Bacteremia (as spleen pneumococcal
culture) then reached a peak
concentration around 24 h. Lung pneumococcal
concentrations
followed the same pattern. CT scan examinations
showed a lobar
condensation first in a lower lobe (Fig.
3), with
rapid extension to the other
lobes within 72 h (Fig.
4A to C).
These CT scan aspects are very close to those observed in humans.
The
main macroscopic aspects were red congestion at 12 h and gray
congestion at 24 h. Lung histopathologic examination at 24 h
showed
a slight increase of leukocytes and a few erythrocytes within
the alveoli and bronchiolar lumen (Fig.
5A). At 48 h, the alveolar
spaces
were filled up with a large number of polymorphonuclear
leukocytes and
fibrinous exudate (Fig.
5B). Pneumococcal pleural
effusion was
constantly seen at 36 h. Major pathological lesions
and
bacterial concentrations occurred between 24 and 48 h
and
progressively evolved to fibrosis in 2 weeks.
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FIG. 2.
Pulmonary lesion scores and pneumococcal concentration
evolution in rabbits with penicillin-resistant S. pneumoniae
(strain 16089) experimental pneumonia by using 10 log10
CFU/ml inoculum. Symbols:
 ,
macroscopic score;
 ,
histopathologic score; --- ---, lung pneumococcal concentrations;
--- ---, spleen pneumococcal concentrations.
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FIG. 3.
CT scan examination of penicillin-resistant S. pneumoniae (strain 16089) experimental pneumonia at 24 h. The
alveolar condensation of the entire left lower lobe (*) is due to
active pneumonia, in contrast with normal aspects of the right lower
and median lobes.
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FIG. 4.
CT bidimensional coronal reconstruction of transaxial
sections. Shown is the evolution of penicillin-resistant S. pneumoniae (strain 16089) experimental pneumonia at 12 h (A),
36 h (B), and 60 h (C). Also shown is alveolar condensation
of the left lower lobe (*) 12 h after inoculation, with a
progressive extension to the entire left lung at 60 h. In this
case, the right lung does not present radiographic signs of
pneumonia.
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FIG. 5.
Lung histopathologic examination of penicillin-resistant
S. pneumoniae (strain 16089) experimental pneumonia at
24 h (A) and 48 h (B). Pneumonia with polymorphonuclear
leukocytes and fibrinous exudate fill up the alveoli.
Hematoxylin-eosin-safranin stain was applied to the sections. Original
magnification, ×250.
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As a comparison, pulmonary lesions and bacterial evolution observed
after instillation of 10 log
10 CFU of
penicillin-susceptible
S. pneumoniae per ml are shown in
Fig.
6. A similar evolution
was observed,
even if lung lesions seemed to be less important
than with the
penicillin-resistant
S. pneumoniae strain. Thus,
this
inoculum of 10 log
10 CFU/ml was used for the experiments
for both penicillin-resistant
S. pneumoniae and
penicillin-susceptible
S. pneumoniae pneumonia.
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FIG. 6.
Pulmonary lesions and pneumococcal concentration
evolution in rabbits with penicillin-susceptible S. pneumoniae (strain 195) experimental pneumonia by using 10 log10 CFU/ml. Symbols:
,
macroscopic score;
,
histopathologic score; ------, lung pneumococcal concentrations;
------, spleen pneumococcal concentrations.
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Differences observed between sacrificed rabbits and rabbits killed by
pneumonia at 24 and 48 h are summarized in Table
3.
Lung and spleen pneumococcal
concentrations were significantly
different at 24 h, according to
cause of death, whereas no difference
was observed at 48 h. On the
other hand, macroscopic and histopathologic
lesions were not different
at 24 h, but a significant difference
existed at 48 h.
Thoracic CT scan examination at 12 h did not
show any difference
between rabbits which survived pneumonia and
those which died of it at
24 h.
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TABLE 3.
Pulmonary lesions and pneumococcal concentrations in
rabbits with penicillin-resistant S. pneumoniae (strain
16089) experimental pneumonia, according to death circumstances
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There was a clear and significant correlation between macroscopic and
histopathologic scores (
r = 0.57,
P < 10
6), as well as between bacterial contents in lungs
and spleen (
r = 0.67,
P < 10
6).
There was also a weak but significant correlation between pneumococcal
pulmonary concentrations and macroscopic or histopathologic scores
(
r = 0.21,
P < 10
6, and
r = 0.12,
P < 10
4,
respectively).
As expected, neither deaths nor pulmonary lesions (either macroscopic
or histopathologic) were induced by inoculation of heat-killed
penicillin-resistant
S. pneumoniae (negative
controls).
Simulation of human amoxicillin pharmacokinetics in rabbits.
Amoxicillin concentrations in serum following the infusion of a
20-mg/kg bolus in four rabbits fitted into a bicompartmental model, as
shown in Fig. 7. Constants were as
follows: A, 155 mg/liter; B, 12 mg/liter; , 15 h1; and
, 1.5 h1. The observed area under the curve was equal
to 15.55 mg · h1 · liter1.
The correlation coefficient between observed and calculated values was
0.996. The time above MIC in serum was 45 and 150 min for
penicillin-resistant S. pneumoniae and
penicillin-susceptible S. pneumoniae, respectively.
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FIG. 7.
Pharmacokinetics of amoxicillin in rabbits and open
bicompartmental modelization. Symbols: --- ---, calculated
concentrations;
, measured
concentrations.
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Simulations of human pharmacokinetics following oral (
n = 14 rabbits) or intravenous (
n = 8 rabbits)
amoxicillin (1 g) administration
are shown in Fig.
8A and B. Cumulative daily doses of
amoxicillin
used to reproduce both intravenous and oral human profiles
in
rabbits were close to 170 mg/kg. Mean areas under curves were
equal
to 60.36 for oral and 63.58 mg · h
1 · liter
1 for intravenous administration, and times above
MIC for the penicillin-resistant
S. pneumoniae strain were
360 and 190 min, respectively. Correlation
coefficients and area under
the curve ratios, between observed
and expected values, were 0.988 and
1.08 for oral simulation and
0.998 and 1.15 for intravenous simulation,
respectively. The mean
measured pulmonary amoxicillin concentration
1 h after intravenous
simulation initiation was 22.3 mg/liter.
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FIG. 8.
Human amoxicillin pharmacokinetics simulation in
rabbits, reproducing human serum profiles following 1-g dose
administered intravenously (A) or orally (B). Symbols:
 ,
obtained concentrations under the human pharmacokinetics simulation;
--- ---, native concentrations without the controlled infusions;
--- ---, expected human concentrations.
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Human-simulated amoxicillin treatment of experimental
penicillin-resistant pneumococcal pneumonia in rabbits.
For
the penicillin-resistant S. pneumoniae pneumonia model
(strain 16089), observed peak amoxicillin concentrations in serum were 14.21 mg/liter for oral simulation and 92.85 mg/liter for intravenous simulation, with expected values of 19.7 and 101 mg/liter, respectively. Correlation coefficients and area under the curve ratios
between observed and expected values were 0.917 and 0.66 (oral
simulation) and 0.997 and 0.89 (intravenous simulation), respectively.
In all the treated rabbits, measured amoxicillin pulmonary
concentrations were always below 1 mg/liter at the time of the
sacrifice (around 48 h after inoculation). Pneumococcal concentrations in lungs and spleen were significantly lower in treated
arms than in untreated arms (orally treated versus untreated, P = 0.005 and P < 106,
and intravenously treated versus untreated, P = 0.004
and P < 106, respectively; Dunnett's
test) (Table 4). There was no difference between the two treated arms. On the other hand, macroscopic and histopathologic evaluations were not different within the three arms.
Results observed for the three arms 48 h after inoculation of the
penicillin-resistant S. pneumoniae (strain 16089) group are
summarized in Table 4.
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TABLE 4.
Effects of treatment by amoxicillin (oral and intravenous
simulation) on penicillin-resistant (strain 16089) and
penicillin-susceptible (strain 195) S. pneumoniae
experimental pneumonia
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In the penicillin-susceptible
S. pneumoniae pneumonia
model (strain 195), observed concentrations in serum at peak were
19.93
mg/liter in oral simulation and 126.36 mg/liter in intravenous
simulation, with expected values of 19.7 and 101 mg/liter,
respectively.
Correlation coefficients and area under the curve ratios
between
observed and expected values were 0.953 and 0.80 (oral
simulation)
and 0.992 and 1.46 (intravenous simulation), respectively.
As
for the penicillin-resistant
S. pneumoniae
pneumonia model, in
all the treated rabbits measured amoxicillin
pulmonary concentrations
were always below 1 mg/liter at the time of
the sacrifice. Pneumococcal
concentrations in lungs and spleen were
also significantly different
between treated and untreated arms (orally
or intravenously treated
versus untreated; macroscopic or
histopathologic score,
P < 10
6;
Dunnett's test). There was no difference between the two treated
arms.
On the other hand, macroscopic and histopathologic evaluations
were not
different within the three arms. Results observed for
the three arms
48 h after inoculation in the penicillin-susceptible
S. pneumoniae (strain 195) group are summarized in Table
4.
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DISCUSSION |
Experimental penicillin-resistant S. pneumoniae
pneumonia in rabbits.
The primary purpose of our study was to
develop a penicillin-resistant S. pneumoniae pneumonia model
in parallel with a penicillin-susceptible S. pneumoniae
pneumonia model. Several animal models have been published (1-3,
6, 9, 14, 17, 18, 33, 34, 39, 41-43, 45, 46). However, although
these models are contributive, our model exhibits several advantages.
The strains used in our study were clinical isolates with common
serotypes. The use of conventional adult male New Zealand White rabbits
offered the following two advantages. (i) They were not naturally
susceptible to S. pneumoniae infections (4),
which guarantees that the observed pathologies were induced by
experiments. (ii) They were not immunosuppressed, in contrast to most
of the animals used in other penicillin-resistant S. pneumoniae pneumonia models (1-3, 6, 9, 14, 17, 33, 34, 42,
43). Inoculation through natural airways into bronchia was more
reproducible than aerosols or intratracheal instillation
(38) and less aggressive than pertracheal or transthoracic
inoculation (9, 18, 33, 39, 41). However, the final inoculum
concentration used for the experiments (10 log10 CFU/ml)
was higher than those used in most other experimental models (6 to 9.3 log10 CFU/ml) (9, 18, 33, 39, 41, 45). Several
parameters may explain such a difference. First, a different virulence
may already exist according to animals and serotypes of strains
(7, 8). Second, the penicillin-resistant S. pneumoniae strains used in our model were diluted in physiologic
serum, without any adjuvant, and inoculated to nonimmunosuppressed
animals. Third, the inoculum concentration was determined to reproduce
findings observed in severe pneumococcal pneumonia in humans.
The different and numerous evaluation criteria used in this model
constitute another interesting advantage. Indeed, survival,
radiological, anatomic, and microbiological data allowed a precise
evaluation of pneumonia and precise comparison with human pathology.
The correlation between these criteria was quite good, but differences
observed in some cases underline their individual
importance.
The most important interest of this model is its ability to closely
reproduce severe human pneumococcal pneumonia, with the
exception that
intrabronchial inoculation of a highly concentrated
S. pneumoniae suspension resulted in the absence of a true incubation
phase. Illness began directly with an invasion phase, quickly
followed
by bacteremic pneumonia, possibly evolving in 2 to 3
weeks to a cure
(data not shown). Cumulative mortality of rabbits
inoculated with 10 log
10 CFU of penicillin-resistant
S. pneumoniae per ml (around 50%) was slightly higher than the 38% observed
in
penicillin-resistant
S. pneumoniae pneumonia in humans
(
37)
and close to the 45 to 85% observed in untreated
bacteremic pneumococcal
pneumonia (
47,
48). In humans, the
severity of pneumococcal
pneumonia is correlated with the existence of
bacteremia, which
was constantly observed in our experimental model.
The macroscopic
and histopathological evolution observed in both
penicillin-resistant
and penicillin-susceptible
S. pneumoniae pneumonia models was
very similar to human pneumonia
(
31,
32,
40). Experimental
infection begins with unilobar
lesions. A rapid extension to the
other lobes occurs within a few
hours, accompanied by pleural
effusion and bacteremia. Finally, the
lesions evolve to fibrosis.
Pneumococcal lung concentrations in dead
rabbits (5 to 8 log
10 CFU/ml) were very similar to these
observed in human postmortem
lung cultures (
29). There was a
weak correlation between bacterial
concentrations and pulmonary
lesions, as described in nosocomial
pneumonia (
28,
40,
49),
even taking into account the possible
lack of reproducibility by
pathologists (
11).
Another point of interest was that comparisons between sacrificed and
pneumonia-related dead rabbits pointed out that in the
first 24 h
the main predictive factor of ulterior evolution was
the bacterial
concentration (and bacteremia); after this delay,
pulmonary injuries
were the most important factor. So, it is tempting
to speculate that
inflammatory phenomena induced by either penicillin-resistant
or
penicillin-susceptible
S. pneumoniae evolve in an autonomous
fashion, without strict correlation with in situ residual bacterial
inoculum. Furthermore, the absence of macroscopic and histopathological
differences observed between treated and untreated rabbits, while
bacterial clearance was obtained, seems to reinforce this
hypothesis.
Simulation of human amoxicillin pharmacokinetics in rabbits.
Considering that the experimental pneumonia in our model closely
reproduced human pathology, the humanization of antibiotic treatment
appeared interesting and important. So, the second purpose of our study
was to reproduce human serum pharmacokinetics of amoxicillin in
rabbits. To do so, we chose an adaptation of antibiotic administration
rather than a modification of the antibiotic elimination. Most of the
studies simulating human pharmacokinetics by adaptation of antibiotic
administration reproduced plasmatic kinetics following intravenous
administration alone and/or for only a few hours (15, 16, 19, 20,
52, 53). In our study, a total of 25 simulations of human
amoxicillin pharmacokinetics were performed. Results obtained after
simulation were very close to the expected (human) concentrations,
which were themselves far from (native) concentrations observed in
rabbits after a single bolus without subsequent infusion (23). So, by developing the Hull mathematical model
(27), we were able to reproduce human pharmacokinetics
fitting into an open bicompartmental model and, moreover, to mimic
human serum profiles following not only intravenous but also oral
administration of amoxicillin. Another theoretical advantage of this
mathematical model was to calculate the extravascular antibiotic
concentrations, thus allowing comparisons with measured intrapulmonary
concentrations. Indeed, it was of particular interest that the measured
amoxicillin pulmonary concentrations were close to the
extravascular concentrations calculated from the model. Moreover,
these pulmonary concentrations were near those observed in humans, even
if these latter are infrequently evaluated and variable (20.8 to 43.1 mg/liter 1 h after intravenous injection of amoxicillin [1 g])
(12, 21).
Human-simulated amoxicillin treatment of experimental
penicillin-resistant pneumococcal pneumonia in rabbits.
The third
purpose of our study was to evaluate antibiotic efficacy in our
penicillin-resistant S. pneumoniae pneumonia model by
simulating human pharmacokinetics of amoxicillin.
Time between inoculation and treatment initiation is an important
prognostic factor, even if it cannot really be appreciated
in
humans. It seems overall relatively short in severe pneumonia
(
35). In our experimental therapeutic study, we chose a
brief
but sufficient delay (4 h after inoculation) to observe
consolidated
pulmonary pathological lesions and high pneumococcal
concentrations
and to start the treatment before the first untreated
pneumonia-related
deaths occurred (8 h after inoculation). Lung lesions
and spleen
pneumococcal concentrations observed 4 h after
inoculation in
our pneumonia model ensure that amoxicillin had a
therapeutic
and not a prophylactic effect. Treatment duration (between
32
and 34 h) allowed an evaluation 48 h after inoculation,
without
any carryover effect, at a time when bacterial concentrations
are important in untreated
rabbits.
Our experimental therapeutic study has shown that amoxicillin treatment
(either four oral or five intravenous administrations
of 1 g every
8 h) resulted in a very significant and similar pneumococcal
clearance in lungs and spleen, for both penicillin-susceptible
S. pneumoniae and penicillin-resistant
S. pneumoniae
pneumonia.
These results were obtained reproducing current
recommendations
for
S. pneumoniae pneumonia treatment in
France (
44). Similar
findings have already been reported by
other studies, in immunosuppressed
mice or guinea pigs, by using
amoxicillin doses theoretically
higher than that in our work (150, 600, and 1,200 mg/kg/day),
without human pharmacokinetics simulation, on
penicillin-resistant
S. pneumoniae pneumonia
(penicillin MIC = 1 to 4 mg/liter) (
33,
39,
42). In
fact, pharmacokinetic data in these studies were
close to those
observed in humans after a 1.5-to-2-g amoxicillin
treatment three times
a day, i.e., approximately twice the dose
we evaluated with our
procedure in rabbits. Lung lesions were
not significantly different
between arms, probably because inflammatory
responses when
triggered continued in spite of pneumococcal
clearance.
The lack of difference in efficacy observed between oral and
intravenous simulated treatments was correlated to the global
pharmacokinetic equivalence between them. The time above MIC was
always
greater than 40%, although it was longer in the oral arm
than in the
intravenous one (87.5% versus 50% for the penicillin-resistant
strain
and 95% versus 66% for the penicillin-susceptible strain),
whereas
the total area under the curve was greater in intravenous
than in oral
arms (320 versus 240 mg · h
1 · liter
1).
In conclusion, we developed a penicillin-resistant
S. pneumoniae experimental pneumonia in immunocompetent rabbits,
which
is easy to reproduce and very close to bacteremic pneumococcal
pneumonia in humans. Human amoxicillin serum profile simulation
in
rabbits, corresponding to an open bicompartmental model, was
realized
in an easy and reproducible fashion. This experimental
therapeutic
study permitted the assessment of the efficacy of
amoxicillin
(reproducing a 3-g/day dose) to obtain pneumococcal
clearance and
survival improvement at 48 h, even with penicillin-resistant
S. pneumoniae (MIC = 4 mg/liter). This work may permit
a better
understanding of pneumonia physiopathology, including
inflammatory
response study, and an evaluation of different therapeutic
approaches
to penicillin-resistant
S. pneumoniae pneumonia.
| |
ACKNOWLEDGMENT |
This study was supported by a grant from MEDEX Society.
| |
FOOTNOTES |
*
Corresponding author. Mailing address: Service des
Maladies Infectieuses et Tropicales, Hôpital du Bocage, BP 1542, 21034 Dijon Cedex, France. Phone: (33) 3 80 29 36 37. Fax: (33) 3 80 29 36 38. E-mail: p.chavanet{at}planetb.fr.
| |
REFERENCES |
| 1.
|
Azoulay-Dupuis, E.,
J. Bedos,
E. Vallée,
D. J. Hardy,
R. N. Swanson, and J. Pocidalo.
1991.
Antipneumococcal activity of ciprofloxacin, ofloxacin, and temafloxacin in an experimental mouse pneumonia model at various stages of the disease.
J. Infect. Dis.
163:319-324[Medline].
|
| 2.
|
Azoulay-Dupuis, E.,
P. Moine,
J. Bedos,
V. Rieux, and E. Vallée.
1996.
Amoxicillin dose-effect relationship with Streptococcus pneumoniae in a mouse pneumonia model and roles of in vitro penicillin susceptibilities, autolysis, and tolerance properties of the strains.
Antimicrob. Agents Chemother.
40:941-946[Abstract].
|
| 3.
|
Azoulay-Dupuis, E.,
E. Vallée,
B. Veber,
J. Bedos,
J. Bauchet, and J. Pocidalo.
1992.
In vivo efficacy of a new fluoroquinolone, sparfloxacin, against penicillin-susceptible and -resistant and multiresistant strains of Streptococcus pneumoniae in a mouse model of pneumonia.
Antimicrob. Agents Chemother.
36:2698-2703[Abstract/Free Full Text].
|
| 4.
|
Baker, D.
1998.
Natural pathogens of laboratory mice, rats, and rabbits and their effects on research.
Clin. Microbiol. Rev.
11:231-266[Abstract/Free Full Text].
|
| 5.
|
Bartlett, J.,
R. Breiman,
L. Mandell, and T. File.
1998.
Community-acquired pneumonia in adults: guidelines for management.
Clin. Infect. Dis.
26:811-838[Medline].
|
| 6.
|
Bédos, J.,
V. Rieux,
J. Bauchet,
M. Muffat-Joly,
C. Carbon, and E. Azoulay-Dupuis.
1996.
Efficacy of trovafloxacin against penicillin-susceptible and multiresistant strains of Streptococcus pneumoniae in a mouse pneumonia model.
Antimicrob. Agents Chemother.
40:2829-2834[Abstract].
|
| 7.
|
Bédos, J.,
O. Rolin,
D. Bouanchaud, and J. Pocidalo.
1991.
Relation entre virulence et résistance aux antibiotiques des pneumocoques. Apport des données expérimentales sur un modèle animal.
Pathol. Biol.
39:984-990[Medline].
|
| 8.
|
Briles, D.
1992.
Strong association between capsular type and virulence for mice among human isolates of Streptococcus pneumoniae.
Infect. Immun.
60:111-116[Abstract/Free Full Text].
|
| 9.
|
Candiani, G.,
M. Abbondi,
M. Borgonovi, and R. Williams.
1997.
Experimental lobar pneumonia due to penicillin-susceptible and penicillin-resistant Streptococcus pneumoniae in immunocompetent and neutropenic rats: efficacy of penicillin and teicoplanin treatment.
J. Antimicrob. Chemother.
39:199-207[Abstract/Free Full Text].
|
| 10.
|
Chapin-Robertson, K., and S. Edberg.
1991.
Measurement of antibiotics in human body fluids: techniques and significance, p. 295-366.
In
V. Lorian (ed.), Antibiotics in laboratory medicine. Williams and Wilkins, Baltimore, Md.
|
| 11.
|
Corley, D.,
S. Kirtland,
R. Winterbauer,
S. Hammar,
D. Dail,
D. Bauermeister, and J. Bolen.
1997.
Reproducibility of the histologic diagnosis of pneumonia among a panel of four pathologistsanalysis of a gold standard.
Chest
112:458-465[Abstract/Free Full Text].
|
| 12.
|
Cox, A.,
J. Meewis, and R. Horton.
1989.
Penetration into lung tissue after intravenous administration of amoxycillin/clavulanate.
J. Antimicrob. Chemother.
24:S87-S91.
|
| 13.
|
Croydon, E. A. P., and R. Sutherland.
1971.
-Amino-p-hydroxybenzylpenicillin (BRL 2333), a new semisynthetic penicillin: absorption and excretion in man, p. 427-430.
. Antimicrob. Agents Chemother. 1970.
|
| 14.
|
Darras-Joly, C.,
J. Bédos,
C. Sauve,
P. Moine,
E. Vallee,
C. Carbon, and E. Azoulay-Dupuis.
1996.
Synergy between amoxicillin and gentamicin in combination against a highly penicillin-resistant and -tolerant strain of Streptococcus pneumoniae in a mouse pneumonia model.
Antimicrob. Agents Chemother.
40:2147-2151[Abstract].
|
| 15.
|
Flückiger, U.,
P. Moreillon,
J. Blaser,
M. Bickle,
M. Glauser, and P. Francioli.
1994.
Simulation of amoxicillin pharmacokinetics in humans for the prevention of streptococcal endocarditis in rats.
Antimicrob. Agents Chemother.
38:2846-2849[Abstract/Free Full Text].
|
| 16.
|
Flückiger, U.,
C. Segessenmann, and A. Gerber.
1991.
Integration of pharmacokinetics and pharmacodynamics of imipenem in a human-adapted mouse model.
Antimicrob. Agents Chemother.
35:1905-1910[Abstract/Free Full Text].
|
| 17.
|
Fukuoka, T.,
H. Kawada,
A. Kitayama,
T. Koga,
M. Kubota,
T. Harasaki,
Y. Kamai,
S. Ohya,
H. Yasuda,
M. Iwata, and S. Kuwahara.
1998.
Efficacy of CS-834 against experimental pneumonia caused by penicillin-susceptible and -resistant Streptococcus pneumoniae in mice.
Antimicrob. Agents Chemother.
42:23-27[Abstract/Free Full Text].
|
| 18.
|
Gavalda, J.,
J. A. Capdevila,
B. Almirante,
J. Otero,
I. Ruiz,
M. Laguarda,
H. Allende,
E. Crespo,
C. Pigrau, and A. Pahissa.
1997.
Treatment of experimental pneumonia due to penicillin-resistant Streptococcus pneumoniae in immunocompetent rats.
Antimicrob. Agents Chemother.
41:795-801[Abstract].
|
| 19.
|
Gerber, A.,
H. Brugger,
C. Feller,
T. Stritzko, and B. Stadler.
1986.
Antibiotic therapy of infections due to Pseudomonas aeruginosa in normal and granulocytopenic mice: comparison of murine and human pharmacokinetics.
J. Infect. Dis.
153:90-97[Medline].
|
| 20.
|
Gerber, A.,
T. Stritzko,
C. Segessenmann, and B. Stalder.
1991.
Simulation of human pharmacokinetic profiles in mice, and impact on antimicrobial efficacy of netilmicin, ticarcillin and ceftazidime in the peritonitis-septicemia model.
Scand. J. Infect. Dis.
74:195-203.
|
| 21.
|
Gould, I. M.,
G. Harvey,
D. Golder,
T. M. Reid,
S. J. Watt,
J. A. Friend,
J. S. Legge, and J. G. Douglas.
1994.
Penetration of amoxycillin/clavulanic acid into bronchial mucosa with different dosing regimens.
Thorax
49:999-1001[Abstract/Free Full Text].
|
| 22.
|
Greenblatt, D., and J. Koch-Weser.
1975.
Clinical pharmacokinetics.
N. Engl. J. Med.
297:702-705.
|
| 23.
|
Hekster, Y.,
A. Baars,
T. Vree,
B. van Klingeren, and A. Rutgers.
1979.
Comparison of the determination of -lactam antibiotic drugs in plasma of rabbits by means of HPLC and of a microbiological assay.
Pharm. Wbl. (Sci. Ed.)
1:695-700.
|
| 24.
|
Hill, S., and K. Jones.
1980.
Pharmacokinetics of parenterally administered amoxycillin.
J. Infect.
2:320-332[Medline].
|
| 25.
|
Hofmann, J.,
M. Cetron,
M. Farley,
W. Baughman,
R. Facklam,
J. Elliott,
K. Deaver, and R. Breiman.
1995.
The prevalence of drug-resistant Streptococcus pneumoniae in Atlanta.
N. Engl. J. Med.
333:481-486[Abstract/Free Full Text].
|
| 26.
|
Hull, C., and K. McLeod.
1976.
Pharmacokinetic analysis using an electrical analogue.
Br. J. Anaesth.
48:677-686[Abstract/Free Full Text].
|
| 27.
|
Hull, C. J.
1984.
General principles of pharmacokinetics, p. 1-24.
In
C. Prys-Roberts, and C. Hug (ed.), Pharmacokinetics of anesthesia. Blackwell, Oxford, England.
|
| 28.
|
Kirtland, S.,
D. Corley,
R. Winterbauer,
S. Springmeyer,
K. Casey,
N. Hampson, and D. Dreis.
1997.
The diagnosis of ventilator-associated pneumoniaa comparison of histologic, microbiologic, and clinical criteria.
Chest
112:445-457[Abstract/Free Full Text].
|
| 29.
|
Knapp, B., and T. Kent.
1968.
Postmortem lung cultures.
Arch. Pathol.
85:200-203[Medline].
|
| 30.
|
Labaune, J.
1988.
Pharmacocinétique, 2nd ed.
Masson, Paris, France.
|
| 31.
|
Marquette, C.,
F. Wallet,
M. Copin,
D. Wermet,
A. Desmidt,
P. Ramon,
R. Courcol, and A. Tonnel.
1996.
Relationship between microbiologic and histologic features in bacterial pneumonia.
Am. J. Respir. Crit. Care Med.
154:1784-1787[Abstract].
|
| 32.
|
Menten, M.,
S. Bailey, and F. DeBone.
1932.
Pneumonia in children.
J. Infect. Dis.
51:254-267.
|
| 33.
|
Moine, P.,
C. Sauve,
E. Vallee,
J. Bedos, and E. Azoulay-Dupuis.
1997.
In vivo efficacy of cefotaxime and amoxicillin against penicillin-susceptible, penicillin-resistant and penicillin-cephalosporin-resistant strains of Streptococcus pneumoniae in a mouse pneumonia model.
Clin. Microbiol. Infect.
3:608-615.
[Medline] |
| 34.
|
Moine, P.,
E. Vallée,
E. Azoulay-Dupuis,
P. Bourget,
J. P. Bédos,
J. Bauchet, and J. J. Pocidalo.
1994.
In vivo efficacy of a broad-spectrum cephalosporin, ceftriaxone, against penicillin-susceptible and -resistant strains of Streptococcus pneumoniae in a mouse pneumonia model.
Antimicrob. Agents Chemother.
38:1953-1958[Abstract/Free Full Text].
|
| 35.
|
Moine, P.,
J. Vercken,
S. Chevret, and P. Gajdos.
1995.
Severe community-acquired pneumococcal pneumonia.
Scand. J. Infect. Dis.
27:201-206[Medline].
|
| 36.
|
Nava, J. M.,
F. Bella,
J. Garau,
J. Lite,
M. Morera,
C. Marti,
D. Fontanals,
B. Font,
V. Pineda,
S. Uriz,
F. Deulofeu,
A. Calderon,
P. Duran,
M. Grau, and A. Agudo.
1994.
Predictive factors for invasive disease due to penicillin-resistant Streptococcus pneumoniae: a population-based study.
J. Infect. Dis.
19:884-890.
|
| 37.
|
Pallares, R.,
J. Lineares,
M. Vadillo,
C. Cabellos,
F. Manresa,
P. F. Viladrich,
R. Martin, and F. Gudiol.
1995.
Resistance to penicillin and cephalosporin and mortality from severe pneumococcal pneumonia in Barcelona, Spain.
N. Engl. J. Med.
333:474-480[Abstract/Free Full Text].
|
| 38.
|
Percy, D. H.,
J. L. Bhasin, and S. Rosendal.
1986.
Experimental pneumonia in rabbits inoculated with strains of Pasteurella multocida.
Can. J. Vet. Res.
50:36-41[Medline].
|
| 39.
|
Ponte, C.,
A. Parra,
E. Nieto, and F. Soriano.
1996.
Development of experimental pneumonia by infection with penicillin-insensitive Streptococcus pneumoniae in guinea pigs and their treatment with amoxicillin, cefotaxime, and meropenem.
Antimicrob. Agents Chemother.
40:2698-2702[Abstract].
|
| 40.
|
Rouby, J.,
E. Martin de Lassale,
P. Poete,
M. Nicolas,
L. Bodin,
V. Jarlier,
Y. Le Charpentier,
J. Grosset, and P. Viars.
1992.
Nosocomial bronchopneumonia in the critically ill.
Am. Rev. Respir. Dis.
146:1059-1066[Medline].
|
| 41.
|
Saladino, R.,
A. Stack,
G. Fleisher,
C. Thompson,
D. Briles,
L. Kobzik, and G. Siber.
1997.
Development of a model of low-inoculum Streptococcus pneumoniae intrapulmonary infection in infant rats.
Infect. Immun.
65:4701-4704[Abstract].
|
| 42.
|
Sauve, C.,
E. Azoulay-Dupuis,
P. Moine,
V. Darras-Joly,
V. Rieux,
C. Carbon, and J. Bédos.
1996.
Efficacies of cefotaxime and ceftriaxone in a mouse model of pneumonia induced by two penicillin- and cephalosporin-resistant strains of Streptococcus pneumoniae.
Antimicrob. Agents Chemother.
40:2147-2151.
|
| 43.
|
Smith, G. M., and K. H. Abbott.
1994.
Development of experimental respiratory infections in neutropenic rats with either penicillin-resistant Streptococcus pneumoniae or -lactamase-producing Haemophilus influenzae.
Antimicrob. Agents Chemother.
38:608-610[Abstract/Free Full Text].
|
| 44.
|
Société de Pathologie Infectieuse de Langue Française (SPILF).
1992.
Quatrième conférence de consensus sur le traitement des infections respiratoires.
Med. Mal. Infect.
22:44-47.
|
| 45.
|
Takashima, K.,
K. Tateda,
T. Matsumoto,
T. Ito,
Y. Iizawa,
M. Nakao, and K. Yamaguchi.
1996.
Establishment of a model of penicillin-resistant Streptococcus pneumoniae pneumonia in healthy CBA/J mice.
J. Med.
45:319-322.
|
| 46.
|
Tateda, K.,
K. Takashima,
H. Miyazaki,
T. Matsumoto,
T. Hatori, and K. Yamaguchi.
1996.
Noncompromised penicillin-resistant pneumococcal pneumonia CBA/J mouse model and comparative efficacies of antibiotics in this model.
Antimicrob. Agents Chemother.
40:1520-1525[Abstract].
|
| 47.
|
Thompson, R.,
J. Ruegsegger,
M. Blankenhorm, and M. Hamburger.
1951.
Primary pneumococcic pneumonia in the Cincinnati General Hospital, 1936-1950.
J. Lab. Clin. Med.
37:73-87.
|
| 48.
|
Tilghman, R., and M. Finland.
1937.
Clinical significance of bacteremia in pneumococcic pneumonia.
Arch. Intern. Med.
59:602-619[Abstract/Free Full Text].
|
| 49.
|
Torres, A.,
M. El-Ebiary,
L. Padro,
J. Gonzales,
J. Puig de la Belcasa,
J. Ramirez,
A. Xaubet,
M. Ferrer, and R. Rodriguez-Roisin.
1994.
Validation of different techniques for the diagnosis of ventilator-associated pneumonia: comparison with immediate postmortem pulmonary biopsy.
Am. J. Respir. Crit. Care Med.
149:324-331[Abstract].
|
| 50.
|
Walsh, T.,
J. Bacher, and P. A. Pizzo.
1988.
Chronic silastic central venous catheterization for induction, maintenance and support of persistent granulocytopenia in rabbits.
Lab. Anim. Sci.
38:467-471[Medline].
|
| 51.
|
Watanakunakorn, C., and T. Bailey.
1997.
Adult bacteremic pneumococcal pneumonia in a community hospital, 1992-1996.
Arch. Intern. Med.
157:1965-1971[Abstract/Free Full Text].
|
| 52.
|
Woodnutt, G.,
V. Berry, and L. Mizen.
1992.
Simulation of human serum pharmacokinetics of cefazolin, piperacillin, and BRL 42715 in rats and efficacy against experimental intraperitoneal infections.
Antimicrob. Agents Chemother.
36:1427-1431[Abstract/Free Full Text].
|
| 53.
|
Woodnutt, G.,
E. Catherall,
I. Kernutt, and L. Mizen.
1988.
Temocillin efficacy in experimental Klebsiella pneumoniae meningitis after infusion into rabbit plasma to simulate antibiotic concentrations in human serum.
Antimicrob. Agents Chemother.
32:1705-1709[Abstract/Free Full Text].
|
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[Abstract]
[Full Text]
-
Pelton, S. I., Hammerschlag, M. R.
(2005). Overcoming Current Obstacles in the Management of Bacterial Community-Acquired Pneumonia in Ambulatory Children. CLIN PEDIATR
44: 1-17
-
Croisier, D., Etienne, M., Piroth, L., Bergoin, E., Lequeu, C., Portier, H., Chavanet, P.
(2004). In vivo pharmacodynamic efficacy of gatifloxacin against Streptococcus pneumoniae in an experimental model of pneumonia: impact of the low levels of fluoroquinolone resistance on the enrichment of resistant mutants. J Antimicrob Chemother
54: 640-647
[Abstract]
[Full Text]
-
Croisier, D., Etienne, M., Bergoin, E., Charles, P.-E., Lequeu, C., Piroth, L., Portier, H., Chavanet, P.
(2004). Mutant Selection Window in Levofloxacin and Moxifloxacin Treatments of Experimental Pneumococcal Pneumonia in a Rabbit Model of Human Therapy. Antimicrob. Agents Chemother.
48: 1699-1707
[Abstract]
[Full Text]
-
Rubinstein, E.
(2003). Reply to: Efficacy and pharmacodynamics of simulated human-like treatment with levofloxacin on experimental pneumonia induced with penicillin-resistant pneumococci with various susceptibilities to fluoroquinolones. J Antimicrob Chemother
51: 1307-1308
[Full Text]
-
Croisier, D., Etienne, M., Chavanet, P.
(2003). Reply. J Antimicrob Chemother
51: 1308-1309
[Full Text]
-
Croisier, D., Chavanet, P., Lequeu, C., Ahanou, A., Nierlich, A., Neuwirth, C., Piroth, L., Duong, M., Buisson, M., Portier, H.
(2002). Efficacy and pharmacodynamics of simulated human-like treatment with levofloxacin on experimental pneumonia induced with penicillin-resistant pneumococci with various susceptibilities to fluoroquinolones. J Antimicrob Chemother
50: 349-360
[Abstract]
[Full Text]
-
Piroth, L., Desbiolles, N., Mateo-Ponce, V., Martin, L., Lequeu, C., Charles, P.-E., Portier, H., Chavanet, P.
(2001). HMR 3647 human-like treatment of experimental pneumonia due to penicillin-resistant and erythromycin-resistant Streptococcus pneumoniae. J Antimicrob Chemother
47: 33-42
[Abstract]
[Full Text]
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Abstract
Introduction
