Previous Article | Next Article 
Antimicrobial Agents and Chemotherapy, June 1999, p. 1387-1392, Vol. 43, No. 6
0066-4804/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Activities of 
-Lactams and Macrolides against
Helicobacter pylori
Ibrahim J.
Hassan,1,*
Roger M.
Stark,1
John
Greenman,2 and
Michael
R.
Millar1
Pathology and Microbiology Department,
University of Bristol, Bristol BS2 8HW,1 and
Faculty of Applied Sciences, University of the West of England,
Frenchay, Bristol BS16 1QY,2 United Kingdom
Received 17 August 1998/Returned for modification 10 December
1998/Accepted 24 March 1999
 |
ABSTRACT |
A continuous-culture system (chemostat) was used to study the
activities of 
-lactam antimicrobial agents, clarithromycin, and
14-OH-clarithromycin against slowly growing Helicobacter
pylori NCTC 11637. H. pylori was grown to steady
state before exposure to these antimicrobial agents at ×8 the MIC. The
bactericidal actions of combinations of amoxicillin and clarithromycin
were also studied. Viable counts (numbers of CFU per milliliter) were determined at 2-h intervals for 12 h and at 20 h after the
addition of antibiotics. The effects of pH changes (6.5 to 7.4) on the activities of amoxicillin, clarithromycin, and the combination of these
against H. pylori NCTC 11637 were also studied. Viable counts following exposure to ampicillin, cefixime, ceftazidime, cefuroxime, cefotaxime, azlocillin, and piperacillin at 20 h
showed bacteriostatic activity. Imipenem, meropenem, amoxicillin,
clarithromycin, and 14-OH-clarithromycin reduced the viable counts by 3 log10 CFU/ml (
99.9% killing). Imipenem was the most
rapidly bactericidal against H. pylori NCTC 11637. Results
of the pH experiments showed that amoxicillin was bactericidal at pHs
6.5 to 7.4. Clarithromycin was bactericidal at pH 7.0 to 7.4 but was
bacteriostatic at pH 6.5. The combination of amoxicillin and
clarithromycin was bactericidal at pHs 6.5 and 7.0. A batch culture
(flask system) was also used to investigate 12 strains of H. pylori for their susceptibilities to -lactams, clarithromycin,
and/or 14-OH-clarithromycin in order to determine whether results from
the chemostat model can be reproduced with batch cultures. Results of
the chemostat time-kill kinetic study were reproducible in our batch
culture flask system. The role of carbapenems in the eradication of
H. pylori should be investigated.
| |
INTRODUCTION |
Over the past 15 years
Helicobacter pylori has emerged as an important human
pathogen associated with gastroduodenal pathology (9, 10,
38). It is the principal cause of type B antral gastritis and
contributes to the etiology of peptic ulcer disease. Eradication of the
organism from the gut of patients reduces the relapse rate of peptic
ulcer disease (35). It has also recently been
epidemiologically linked to the development of gastric malignancies (7, 11, 43) and has been classified as a category 1 carcinogen by the World Health Organization (25, 36).
Although H. pylori is susceptible to a wide range of
antimicrobial agents in vitro (29), this does not translate
into in vivo efficacy, and eradication requires the use of combinations
of antimicrobial agents (5, 16, 23).
We report on a comparison of the activities of -lactam antibiotics
and macrolides against slowly growing H. pylori strains in
continuous and batch cultures. The effect of pH on the activities of
amoxicillin and clarithromycin alone and in combination against H. pylori NCTC 11637 in the chemostat was also studied. The
investigations of bactericidal agents active against H. pylori in vitro may contribute to better strategies for
eradication therapy. These may also help to determine if the in vivo
success of clinical treatment regimens can be predicted by a chemostat model.
| |
MATERIALS AND METHODS |
Bacterial strains.
H. pylori NCTC 11637 was used in
all the chemostat experiments and, together with 11 other strains (NCTC
11916 and 10 clinical isolates) obtained at endoscopy from patients at
the Bristol Royal Infirmary, Bristol, United Kingdom, between 1993 and
1996, was used for the batch culture kinetic study.
Media.
The growth medium was a modified brucella broth
(0495-17-3; Difco Laboratories, Detroit, Mich.) containing the
following (per liter): Bacto Tryptone, 10 g; Bacto Peptamin,
10 g; Bacto Dextrose, 1 g; Bacto Yeast Extract, 2 g;
NaCl, 5 g; and NaHSO3, 0.1 g. This mixture was
supplemented with 1% fetal calf serum (Gibco BRL, Uxbridge, United Kingdom).
MIC determination.
The MICs of the antimicrobial agents used
for the experiments were determined by a standard agar dilution method
(24) with Columbia agar base (Oxoid CM 331; Unipath Ltd.,
Basingstoke, United Kingdom) supplemented with 5% horse blood. The
plates were inoculated with a multipoint replicator (Mast, Liverpool,
United Kingdom) with an inoculum of 104 CFU/spot. The
plates were incubated at 37°C under microaerophilic conditions for
72 h before reading of the results. The MIC was defined as the
lowest antibiotic concentration which prevented visible growth of
bacteria. Repeat determinations were done by a broth macrodilution
method as described previously (24). The interassay
variation was no more than ±1 dilution step (except for clarithromycin
at pH 6.5, for which a twofold dilution was observed). The results
obtained by both methods were comparable to those reported previously
(18).
Antimicrobial agents.
The antimicrobial agents used in this
study were ampicillin and amoxicillin (Beecham Laboratories,
Betchworth, United Kingdom), imipenem (MSD Ltd., Hoddesdon, Herts,
England), meropenem (ICI plc Macclesfield, Cheshire, England),
piperacillin and cefixime (Lederle Laboratories, Gosport, Hants,
England), azlocillin (Bayer Ltd., Berkshire, United Kingdom),
ceftazidime and cefuroxime (Glaxo, Middlesex, England), cefotaxime
(Roussel Laboratories Ltd., Uxbridge, England), and clarithromycin
(Abbott Laboratories, Queenborough, United Kingdom). Each antimicrobial
agent was prepared prior to use in accordance with the manufacturer's
instructions, with a stock solution of known potency being produced.
Establishment of cultures in the chemostat.
The chemostat
used for the experiments was an LH 500 series direct-drive fermentor
with control modules for temperature, pH, gas flow, and stir rate
(Inceltech UK Ltd., Reading, Berks, United Kingdom). It consists of a
culture vessel fitted with an overflow device to maintain a constant
volume (15, 41). The method used in the present study for
establishment of a stable continuous culture of slowly growing H. pylori was a modification of that described previously
(32); namely, H. pylori was harvested from Columbia agar plates, suspended in 7 ml of sterile brucella broth that
had been prewarmed to 37°C, and inoculated aseptically into 700 ml of
modified brucella broth in the growth vessel of the chemostat. A
microaerophilic gas mixture consisting of O2,
CO2, and N2 at 5:10:85 (in percent
[vol/vol]), respectively, was filtered through a 0.2-µm-pore-size
filter and was sparged at a rate of 300 ml/min through the chemostat
vessel. The stir rate was maintained at 700 rpm, while the pot volume
at this stir rate was 700 ml. Sterile growth medium from the medium
reservoir was fed by a peristaltic pump into the culture vessel at a
rate of 700 ml/24 h to give a dilution rate of 0.04 h
1.
The maximum specific growth rate (µmax) of H. pylori NCTC 11637 under these conditions was 0.052 at pH 6.5, 0.132 at pH 7.0, 0.212 at pH 7.2, and 0.180 at pH 7.4. The incubation
temperature was 37°C. The medium flow was started when the broth
became visibly turbid and the chemostat culture was then allowed to
stabilize over the next 5 to 6 days, permitting the establishment of a
steady state between bacterial growth and bacterial washout, at which point the killing-kinetic experiments were started. Once the pH for the
experiment was set, it was maintained by the automatic addition of acid
(1 M HNO3) or alkali (1 M NaOH) from the pH control unit.
When the bacterial viable count became stable the oxygen saturation was
approximately 5%. The purity of the chemostat culture during the
experiments was monitored by daily Gram staining and culturing of
samples at 37°C under aerobic, anaerobic, and microaerophilic conditions.
Establishment of batch cultures (flask system).
Cultures of
H. pylori were established with a set of 250-ml conical
flasks each containing 98 ml of sterile brucella broth and 1 ml of
fetal calf serum into which 1 ml of a standardized H. pylori
(106 CFU/ml) culture was inoculated. The flasks were placed
inside an orbital incubator at 37°C and were agitated at 150 rpm, and a filtered microaerophilic gas mixture was bubbled through the cultures
at a rate of 150 ml/min. During the deceleration phase of growth (i.e.,
after about 16 h of incubation), when the cells were growing at a
reduced rate compared to the rate at which they grew while they were in
the midexponential phase, the test antibiotics were added at a
concentration of 8× the MIC. Sixteen hours was chosen after
calculation of the physiologic "growth cycle" showed deceleration
of the growth rate at this time point under these experimental conditions.
Determination of bactericidal activity.
Each antimicrobial
agent was added in a pulse directly into the broth within the culture
vessel to give a final concentration of 8× the MIC at the start of the
experiments. After incubation of the organism-antibiotic mixture, a
sample of 500 µl was removed from the chemostat vessel (or flasks)
for determination of viable counts (numbers of CFU per milliliter) as
described previously (31). The sample was serially diluted
(1:10) in warm phosphate-buffered saline, and 20-µl volumes from each
dilution were spread in triplicate onto Columbia blood agar plates. The
inoculated plates were incubated at 37°C under microaerophilic
conditions for 72 h before the colonies were counted. Only the
organisms on plates yielding mean viable counts of at least 500 CFU/ml
were counted, and the results were recorded. Samples were collected for
viable count determinations immediately preceding the addition of
antimicrobial agents to the chemostat vessel (or flasks) and at 2, 4, 6, 8, 10, 12, and 20 h. The presence of antimicrobial agents in
the flasks (or chemostat) was monitored by a microbiological agar well
diffusion assay as described previously (2). From the mean
viable counts, killing and viability curves were determined, and from
these curves the bactericidal activity of each agent was calculated.
The bacterial inoculum at the start of the experiments was 8.0 ± 0.2 log10 CFU/ml. Each experiment was repeated three times.
| |
RESULTS |
MICs.
The MICs of the antimicrobial agents for all the
H. pylori isolates tested are presented in Table
1.
Chemostat.
Figure 1 is a graphic
representation of the chemostat killing curves for H. pylori
NCTC 11637 and shows the activities of those agents that produce a fall
in bacterial count of at least 3 log10 CFU/ml (99.9%
killing) relative to that expected by washout of nondividing cells at
20 h. These bactericidal agents include amoxicillin, meropenem,
imipenem, clarithromycin, and 14-OH-clarithromycin. Imipenem was the
most rapidly bactericidal, with a decrease in the bacterial count of 4 log10 CFU/ml at 8 h. From 10 h onward after the
addition of imipenem it was not possible to detect H. pylori
by determination of viable counts from the chemostat broth, which
became markedly less turbid. The bacteriostatic agents included ampicillin, cefixime, cefuroxime, cefotaxime, and ceftazidime, which
gave decreases in bacterial count of <1.5 log10 CFU/ml, while azlocillin and piperacillin produced decreases of 2.5 log10 CFU/ml (data not shown).
View larger version (23K):
[in this window]
[in a new window]
|
FIG. 1.
Killing kinetics of antimicrobial agents (at 8× MIC) at
pH 7.0 in chemostat cultures for H. pylori NCTC 11637.  ,
imipenem;  , meropenem;  ,
Amoxicillin;  , clarithromycin;  , 14-OH-clarithromycin; ×,
washout;  , time of antibiotic addition.
|
|
Effect of pH on activities of antimicrobial agents. (i)
Amoxicillin.
Figure 2 shows the
results of the effect of pH 6.5, 7.0, 7.2, and 7.4 on the activity of
amoxicillin against H. pylori NCTC 11637. Amoxicillin was
bactericidal at all pH values (99.9% killing). It was most rapidly
cidal at pHs 7.4 and 7.2 with a decrease of >3 log10
CFU/ml at 10 h compared with a decrease of 3 log10 at pHs 7.0 and 6.5 at 20 h. The pH optima for killing by amoxicillin were 7.2 and 7.4.
View larger version (21K):
[in this window]
[in a new window]
|
FIG. 2.
Effect of pH on killing kinetics of amoxicillin (at 8×
the MIC) in chemostat cultures for H. pylori NCTC 11637. , pH 6.5; , pH 7;  , pH 7.2;
, pH 7.4; , washout; , time of antibiotic addition.
|
|
(ii) Clarithromycin.
Figure 3
shows the results of the effect of pHs 6.5 to 7.4 on the activity of
clarithromycin against H. pylori NCTC 11637. Clarithromycin was bactericidal at pHs 7.0 to 7.4 and achieved killing
of at least 3 log10 CFU/ml at 20 h (99.9% killing).
It was, however, only bacteriostatic at pH 6.5 and caused a decrease in
the bacterial count of 1 log10 CFU/ml at 20 h.
View larger version (20K):
[in this window]
[in a new window]
|
FIG. 3.
Effect of pH on killing kinetics of clarithromycin (at
8× the MIC) in chemostat cultures for H. pylori NCTC 11637. , pH 6.5; , pH 7; , pH 7.2;
, pH 7.4; , washout; , time of antibiotic addition.
|
|
(iii) Combination of amoxicillin and clarithromycin.
Figure
4 shows the killing curves for the
combined activity of clarithromycin and amoxicillin against H. pylori NCTC 11637 at pHs 6.5 and 7.0. At both pHs the combination
was bactericidal from 8 h onward. There was also greater cidal
activity for the combination compared to the activities of the
antibiotics individually at the same pHs. The cidal activity of
amoxicillin at pH 6.5 was comparable to that at pH 7.0 (Fig. 4).
View larger version (23K):
[in this window]
[in a new window]
|
FIG. 4.
Effect of pH on killing kinetics of clarithromycin,
amoxicillin, and combinations (at 8× the MIC) in chemostat cultures
for H. pylori NCTC 11637. , clarithromycin at pH 6.5; ,
clarithromycin at pH 7.0; , amoxicillin at pH 6.5; ×,
clarithromycin and amoxicillin at pH 6.5; , clarithromycin and
amoxicillin at pH 7.0;  , washout; , time of antibiotic addition.
|
|
Batch culture (flask system).
Figure
5 shows the killing curves for H. pylori NCTC 11637 in a batch-culture system. Amoxicillin,
meropenem, imipenem, and clarithromycin were all bactericidal. Imipenem
was still the most bactericidal agent, with a decrease of 3.5 log10 CFU/ml at 12 h, followed by meropenem,
amoxicillin, and clarithromycin, with a decrease of 3 log10
CFU/ml at 20 h. 14-OH-clarithromycin was only bacteriostatic and
gave a fall of 2.5 log10 CFU/ml. The other -lactams were
as bacteriostatic with the batch-culture system as with the chemostat
(data not shown).
View larger version (20K):
[in this window]
[in a new window]
|
FIG. 5.
Killing kinetics of antimicrobial agents (at 8× the
MIC) at pH 7.0 in batch cultures for H. pylori NCTC 11637. , imipenem; , meropenem; ,
amoxicillin; , clarithromycin; , 14-OH-clarithromycin; ×,
control; , time of antibiotic addition.
|
|
Other strains.
For H. pylori NCTC 11916 and five
clinical strains, imipenem was the most rapidly bactericidal agent,
with a killing of at least 3 log10 CFU/ml at 20 h, and
was the only agent that was bactericidal for two of the strains. For a
further two strains (strains 3266 and AMMI) only imipenem and
meropenem were bactericidal. For strain 18868 imipenem,
amoxicillin, and clarithromycin were equally bactericidal at 20 h,
while strain 2985 was equally killed at 20 h by imipenem,
meropenem, and clarithromycin. For one strain (TIYO) clarithromycin was
the only bactericidal agent, with the rest of the agents, including
imipenem, remaining only bacteriostatic (Table
2).
| |
DISCUSSION |
We have compared the activities of 10 -lactams,
clarithromycin, and 14-OH-clarithromycin against slowly growing
H. pylori NCTC 11637 in both the chemostat and batch
cultures (flask system). The chemostat, which can grow bacteria at the
rate set by the experimenter, is a good model for killing-kinetic
studies. It may provide results which are more predictive of the in
vivo situation in which bacteria have a more prolonged doubling time
compared to that under in vitro conditions (28). The
chemostat has been used previously for killing-kinetic studies (8,
32). However, we are unaware of any comparison of this system for
killing-kinetic studies with cheaper traditional batch-culture methods.
We have compared the two systems for killing-kinetic studies and have shown similar trends in the activities of -lactam antibiotics and
clarithromycin against slowly growing H. pylori NCTC 11637. In both systems, imipenem, meropenem, amoxicillin, and clarithromycin were bactericidal, while the remaining antimicrobial agents were bacteriostatic. Imipenem was the most rapidly bactericidal agent, although it was bactericidal to a lesser degree in the batch culture than in the chemostat. Also, 14-OH-clarithromycin, which was
bactericidal in the chemostat, was bacteriostatic only in the batch
culture (flask system).
The current search for agents with improved anti-H. pylori
activities continues. No single agent give adequate eradication, and
compliance is a problem with current multidrug regimens for the
treatment of H. pylori infection (42).
Clarithromycin has achieved the highest reported eradication rates of
any monotherapy (34) and, like amoxicillin, has become an
established part of combination therapy for H. pylori
infection (33). The fact that imipenem and meropenem were
bactericidal against most strains may be of interest in view of the
current development of novel oral carbapenems (3, 40). Our
results suggest that carbapenems may have a role in the therapy of
H. pylori-associated disease. In vitro and gut
pharmacokinetic studies of the newer oral carbapenems would need to be
performed. Imipenem, for example, is widely distributed in body fluids
and secretions including gastric juice, in which suprainhibitory
concentrations have been found following intravenous administration
(14, 39). A recent pilot study of imipenem monotherapy for
48 h has achieved good clearance but has failed to eradicate
H. pylori from the gut (39). The short duration of therapy in this study makes comparison with longer-course regimens difficult. There is current interest in the use of intravenous antibiotics for the management of bleeding peptic ulcers in patients who are H. pylori positive. There is evidence to support the
view that eradication of H. pylori from this group of
patients prevents recurrence of the bleeding episode (1, 19,
26).
The study of the effect of pH changes on the activities of
antimicrobial agents against microorganisms had been reported
previously for batch cultures (4, 17, 20). Changes in pH can
affect the activities of antimicrobial agents as well as the expression of bacterial target sites. Our chemostat data showed that amoxicillin had pH optima for killing of H. pylori NCTC 11637 at 7.2 and
7.4. This is in agreement with previous reports (6, 37).
This was not surprising since amoxicillin is an amphoteric agent which is less ionized at acidic pH. Clarithromycin was bactericidal at all
pHs except pH 6.5. The activities of macrolides have been known to be
decreased at acidic pH, but the degree to which they are affected
varies between members of this group of agents (12). Clarithromycin has been reported to be bactericidal at acidic pH
(13, 22), while others have reported a loss of activity of
clarithromycin at acidic pH (6), a result similar to that of
the present study.
The omeprazole-based combination therapy with clarithromycin and
amoxicillin is now a regimen of choice for the treatment of H. pylori infection in Europe (27). The results of the
present combination study show that at both pH 6.5 and pH 7.0, there
was bactericidal activity which was greater than the activities of the
individual agents at the same pH. Omeprazole facilitates secretion of
antibiotics into the mucosa and increases tissue bioavailability (21). Previous studies have not demonstrated synergy between various combinations of omeprazole, amoxicillin, and clarithromycin in
vitro (6, 30, 37).
In conclusion, the greater activity of imipenem compared with
those of other -lactams and clarithromycin should prompt
further studies and the search for oral carbapenems with potential
anti-H. pylori activity.
| |
FOOTNOTES |
*
Corresponding author. Mailing address: Pathology and
Microbiology Department, University of Bristol, BRI Level 8, Bristol BS2 8HW, United Kingdom. Phone: 44-117-9282514. Fax: 44-117-929 9162. E-mail: I.J.Hassan{at}bristol.ac.uk.
| |
REFERENCES |
| 1.
|
Adamek, R. J.,
M. Freitag,
W. Opferkuch,
G. H. Ruhl, and M. Wegener.
1994.
I/V omeprazole/amoxycillin and omeprazole pre-treatment in Helicobacter pylori positive acute peptic ulcer bleeding. A pilot study.
Scand. J. Gastroenterol.
29:880-883[Medline].
|
| 2.
|
Anhalt, J. P.
1985.
Assays of antimicrobial agents in body fluid, p. 1009-1014.
In
E. H. Lennette, A. Balows, W. J. Hausler, Jr., and H. J. Shadomy (ed.), Manual of clinical microbiology, 4th ed. American Society for Microbiology, Washington, D.C.
|
| 3.
|
Aoki, H.,
M. Sekiguchi,
K. Akahane,
Y. Tsutomi,
H. Korenaga,
T. Hayano, and I. Hayakawa.
1995.
A new oral carbapenem antibiotic. 3. Pharmacokinetics and safety in laboratory animals, abstr. F135, p. 136.
In
Program and abstracts of the 35th Interscience Conference on Antimicrobial Agents and Chemotherapy. American Society for Microbiology, Washington, D.C.
|
| 4.
|
Barry, A. L.,
R. N. Jones, and C. Thornsberry.
1988.
In vitro activities of azithromycin (CP 62,993), clarithromycin (A-56268; TE-031), erythromycin, roxythromycin, and clindamycin.
Antimicrob. Agents Chemother.
32:752-754[Abstract/Free Full Text].
|
| 5.
|
Borsch, G.,
U. Mai, and K. M. Muller.
1988.
Monotherapy or polychemotherapy in the treatment of Campylobacter pylori-related gastroduodenal disease.
Scand. J. Gastroenter.
23(Suppl. 142):101-106.
|
| 6.
|
Cederbrant, G.,
G. Kahlmeter,
C. Schalen, and C. Kamme.
1994.
Additive effect of clarithromycin combined with 14-hydroxy-clarithromycin, erythromycin, amoxycillin, metronidazole, or omeprazole against H. pylori.
J. Antimicrob. Chemother.
34:1025-1029[Abstract/Free Full Text].
|
| 7.
|
Correa, P.
1992.
Human gastric carcinogenesis: a multistep and a multifactorial process. First American Cancer Society Award lecture on cancer epidemiology and prevention.
Cancer Res.
52:6735-6740[Abstract/Free Full Text].
|
| 8.
|
Cozens, R. M.,
E. Tuomanen,
W. Tosch,
O. Zak,
J. Suter, and A. Tomasz.
1986.
Evaluation of the bactericidal activity of -lactam antibiotics on slowly growing bacteria cultured in the chemostat.
Antimicrob. Agents Chemother.
29:797-802[Abstract/Free Full Text].
|
| 9.
|
DeCross, A. J., and B. J. Marshall.
1993.
The role of Helicobacter pylori in acid-peptic disease.
Am. J. Med. Sci.
306:381-392[Medline].
|
| 10.
|
Dooley, C. P.
1993.
Background and historical considerations of Helicobacter pylori.
Gastroenterol. Clin. N. Am.
22:1-4[Medline].
|
| 11.
|
Eurogast Study Group.
1993.
An international association between Helicobacter pylori infection & gastric cancer.
Lancet
341:1359-1362[Medline].
|
| 12.
|
Fiese, E. F., and S. H. Steffan.
1990.
Comparison of the acid stability of azithromycin and clarithromycin-A.
J. Antimicrob. Chemother.
25(Suppl. A):39-47[Abstract/Free Full Text].
|
| 13.
|
Flamm, R. K.,
J. Beyer,
S. K. Tanaka, and J. Clement.
1996.
Kill kinetics of antimicrobial agents against H. pylori.
J. Antimicrob. Chemother.
38:719-725[Abstract/Free Full Text].
|
| 14.
|
Geddes, A. M., and W. Stilles.
1985.
Imipenem: the first thienamycin antibiotic.
Rev. Infect. Dis.
7(Suppl. 3):S353-S536.
|
| 15.
|
Gilbert, P.
1985.
The theory and relevance of continuous culture.
J. Antimicrob. Chemother.
15(Suppl. A):1-6[Free Full Text].
|
| 16.
|
Glupczynski, Y.
1990.
In vitro susceptibility of Helicobacter pylori to antibiotics & bismuth salts & the importance of acquired resistance to antibiotics in treatment failures of Helicobacter pylori infection, p. 49-58.
In
P. Malfertheiner, and H. Ditschuneit (ed.), Helicobacter pylori, gastritis & peptic ulcer. Springer-Verlag, Berlin, Germany.
|
| 17.
|
Glupczynski, Y.
1993.
In vitro susceptibility testing of H. pylori to antimicrobial agents: basis for treatment of microbiologists' obsession?
Zentbl. Bakteriol. Parasitenkd. Infektionskr. Hyg. Abt. 1 Orig.
280:227-238.
|
| 18.
|
Goodwin, C. S.,
P. Blake, and E. Blincow.
1986.
The MIC & MBC of antimicrobial agents and anti-ulcer agents against Campylobacter pyloridis.
J. Antimicrob. Chemother.
17:309-314[Abstract/Free Full Text].
|
| 19.
|
Graham, D. Y.,
K. S. Hepps,
F. C. Ramirez,
G. M. Lew, and Z. A. Saeed.
1993.
Treatment of Helicobacter pylori reduces the rate of rebleeding in peptic ulcer disease.
Scand. J. Gastroenterol.
28:939-942[Medline].
|
| 20.
|
Grayson, M. L.,
G. M. Eliopoulos,
M. J. Ferraro, and R. C. Moellering.
1989.
Effect of varying pH on the susceptibility of C. pylori to antimicrobial agents.
Eur. J. Clin. Microbiol. Infect. Dis.
8:888-889[Medline].
|
| 21.
|
Gustavson, L. E.,
J. F. Kaiser,
A. L. Edmonds,
C. S. Locke,
M. L. DeBartolo, and D. W. Schneck.
1995.
Effect of omeprazole on concentrations of clarithromycin in plasma and gastric tissue at steady state.
Antimicrob. Agents Chemother.
39:2078-2083[Abstract].
|
| 22.
|
Hardy, D. J.,
C. W. Hanson,
D. M. Hensey,
J. M. Beyer, and P. B. Fernandes.
1988.
Susceptibility of Campylobacter pylori to macrolides and fluoroquinolones.
J. Antimicrob. Chemother.
22:631-636[Abstract/Free Full Text].
|
| 23.
|
Harris, A., and J. J. Misiewicz.
1995.
Hitting Helicobacter pylori for four.
Lancet
345:806-807[Medline].
|
| 24.
|
Holt, A., and D. Brown.
1989.
Antimicrobial susceptibility testing, p. 167-193.
In
P. M. Hawkey, and D. A. Lewis (ed.), Medical bacteriology: a practical approach. IRL Press, Oxford, United Kingdom.
|
| 25.
|
International Agency for Research on Cancer Working Group on the Evaluation of Carcinogenic Risks to Humans.
1994.
Helicobacter pylori, p. 177-240.
In
Schistosomes, liver flukes & Helicobacter pylori: views & expert opinions of an IARC working group on the evaluation of carcinogenic risks to humans. International Agency for Research on Cancer, Lyon, France.
|
| 26.
|
Labenz, J., and G. Borsch.
1994.
Role of Helicobacter pylori eradication in the prevention of peptic ulcer bleeding relapse.
Digestion
55:19-23[Medline].
|
| 27.
|
Maastricht Consensus Report.
1997.
Current European concepts in the management of Helicobacter pylori.
Gut
41:8-13[Abstract/Free Full Text].
|
| 28.
|
Maw, J., and G. G. Meynell.
1968.
The true division and death rate of Salmonella typhimurium in the mouse spleen determined with superinfecting phage P22.
Br. J. Exp. Pathol.
49:597-613[Medline].
|
| 29.
|
McNulty, C. A. M.
1989.
Bacteriological and pharmacological basis for the treatment of Campylobacter pylori infection.
Gastroenterol. Clin. Biol.
13:96B-100B[Medline].
|
| 30.
|
Meyer, J. M.,
S. Ryu,
S. L. Pendland, and L. H. Danziger.
1997.
In vitro synergy testing of clarithromycin and 14-hydroxyclarithromycin with amoxicillin or bismuth subsalicylate against Helicobacter pylori.
Antimicrob. Agents Chemother.
41:1607-1608[Abstract].
|
| 31.
|
Miles, A. A., and S. S. Misra.
1938.
The estimation of the bactericidal power of the blood.
J. Hyg. Camb.
38:732-749.
|
| 32.
|
Millar, R. M., and J. Pike.
1992.
Bactericidal activity of antimicrobial agents against slowly growing Helicobacter pylori.
Antimicrob. Agents Chemother.
36:185-187[Abstract/Free Full Text].
|
| 33.
|
National Institutes of Health Consensus Development Panel on Helicobacter pylori in Peptic Ulcer Disease.
1994.
Helicobacter pylori in peptic ulcer disease.
JAMA
272:65-69[Abstract/Free Full Text].
|
| 34.
|
Peterson, W. L.,
D. Y. Graham,
B. Marshall,
M. J. Blaser,
R. M. Genta,
P. D. Klein,
C. W. Stratton,
J. Drnec,
P. Prokocimer, and N. Siepman.
1993.
Clarithromycin as monotherapy for eradication of Helicobacter pylori: a randomized double blind trial.
Am. J. Gastroenterol.
88:1860-1864[Medline].
|
| 35.
|
Rauws, E. A. J., and G. N. J. Tytgat.
1990.
Cure of duodenal ulcer associated with eradication of Helicobacter pylori.
Lancet
335:1233-1235[Medline].
|
| 36.
|
Sharp, D.
1995.
Worms, spirals, flukes as carcinogens.
Lancet
345:403-404[Medline]. (Commentary.)
|
| 37.
|
Sjostrom, J. E., and H. Larsson.
1996.
Factors affecting growth and antibiotic susceptibility of Helicobacter pylori: effect of pH and urea on the survival of a wild-type strain and a urease-deficient mutant.
J. Med. Microbiol.
44:425-433[Abstract/Free Full Text].
|
| 38.
|
Sung, J. J. Y.,
S. C. S. Chung,
T. K. W. Ling,
M. Y. Yung,
V. K. S. Leung,
K. W. Enders,
K. K. Michael,
A. F. B. Cheng, and K. C. Arthur.
1995.
Antibacterial treatment of gastric ulcers associated with Helicobacter pylori.
N. Engl. J. Med.
332:139-142[Abstract/Free Full Text].
|
| 39.
|
Sung, J. J. Y.,
S. C. S. Chung,
S. W. Hosking,
R. C. Y. Chan,
T. K. W. Ling,
M. Y. Yung,
A. F. B. Cheng, and A. K. C. Li.
1995.
Mucosal pharmacokinetics and pilot study of short course of parenteral imipenem in the eradication of Helicobacter pylori.
J. Gastroenterol. Hepatol.
10:66-69[Medline].
|
| 40.
|
Tanaka, M.,
M. Hohmura,
T. Nishi,
K. Sato, and I. Hayakawa.
1997.
Antimicrobial activity of DU-6681a, a parent compound of novel oral carbapenem DZ-2640.
Antimicrob. Agents Chemother.
41:1260-1268[Abstract].
|
| 41.
|
Tempest, D. W.
1970.
The continuous cultivation of microorganisms. Theory of the chemostat.
Methods Microbiol.
2:259-276.
|
| 42.
|
Walsh, J. H., and W. L. Peterson.
1995.
The treatment of H. pylori infection in the management of peptic ulcer disease.
N. Engl. J. Med.
333:984-991[Free Full Text].
|
| 43.
|
Wotherspoon, A. C.,
C. Doglioni,
T. C. Diss,
L. Pan,
A. Moschini,
M. Boni, and P. G. Isaacson.
1993.
Regression of primary low-grade B-cell gastric lymphoma of mucosa-associated lymphoid tissue type after eradication of Helicobacter pylori.
Lancet
342:575-577[Medline].
|
Antimicrobial Agents and Chemotherapy, June 1999, p. 1387-1392, Vol. 43, No. 6
0066-4804/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
This article has been cited by other articles:
-
Simala-Grant, J. L., Zopf, D., Taylor, D. E.
(2001). Antibiotic susceptibility of attached and free-floating Helicobacter pylori. J Antimicrob Chemother
47: 555-563
[Abstract]
[Full Text]
Top
Abstract
Introduction
