Previous Article | Next Article 
Antimicrobial Agents and Chemotherapy, February 2000, p. 456-457, Vol. 44, No. 2
National Public Health Institute,
Antimicrobial Research Laboratory,1 and
Department of Physical Medicine and Rehabilitation, Turku
University Hospital,3 FIN-20521 Turku, and
Institute of Dentistry, Turku University, FIN-20520
Turku,2 Finland
Received 7 May 1999/Returned for modification 10 August
1999/Accepted 13 November 1999
Resistance to cefuroxime, penicillin, tetracycline, and mercury is
reported for 839 Streptococcus mutans isolates from 209 human study subjects. The MICs of these drugs did not differ for isolates from one dental amalgam group and two nonamalgam subsets: a
group with no known exposure to amalgam and a group whose members had
their amalgam fillings removed.
Amalgam fillings contain
approximately 50% mercury (19). Mainly due to the mercury,
dental amalgam has antibacterial properties (14, 15).
Different genes for antimicrobial resistance are often genetically
linked and spread together; selection pressure from a single agent can
promote multiple resistance. Heavy-metal ion resistance (for
example, against mercury [Hg], cadmium, and silver) has been
found together with antimicrobial resistance determinants (2, 6,
13, 21, 24). It has been suggested that the environmental
load of mercury, including that released from amalgam fillings, may
promote and maintain antimicrobial resistance together with mercury
resistance in human normal flora (20). The threat of
pathogens acquiring this resistance is always present; one example is
the transfer of penicillin resistance genes from oral streptococci to
Streptococcus pneumoniae (3).
The oral streptococcus Streptococcus mutans is considered
one of the most important cariogenic species of the human microbial flora (12). The suppression of S. mutans by
antimicrobial agents, especially by locally administrated
chlorhexidine, is consequently of clinical importance (11, 17,
23). Chlorhexidine reduces the rate of caries significantly
(11).
Oral bacteria might respond to mercury from dental amalgam by
developing resistance. If they simultaneously develop resistance to
other antimicrobial agents, then the use of mercury-containing dental
amalgam would have to be reconsidered. The effect of dental amalgam on
antimicrobial resistance has not been sufficiently studied in human populations.
In the present study, we have examined S. mutans to find the
possible differences in mercury and antimicrobial resistance in oral
flora among three adult human groups: a group whose members had had all
amalgam fillings removed (designated the NAR group; n = 62, mean age 50 years, range 31 to 72 years), a group that had never
been exposed to dental amalgam fillings (the NA group; n = 48, mean age 23 years, range 18 to 65 years), and a
group having various numbers of amalgam fillings (the A group;
n = 99, mean age 48 years, range 19 to 83 years).
We collected paraffin-stimulated whole saliva samples (5 ml) from 209 human study subjects. The fresh saliva samples were cultured within
1 h of arrival at the laboratory. The samples were diluted 1:100
in physiological saline, and 20 µl of this dilution was plated onto
mitis salivarius agar, composed of mitis salivarius agar base (Difco
Laboratories, Detroit, Mich.), 1% potassium tellurite (Merck OY,
Espoo, Finland), 15% sucrose, and 0.1 U of bacitracin (Sigma
Chemical Co., St. Louis, Mo.) per ml.
Plates were incubated for 3 days at 35°C in a 5%
CO2 atmosphere to facilitate identification. Judging
by colony appearance, approximately four colonies were picked. Dark,
rough S. mutans-like colonies (5, 8) were
identified as mutans streptococci (7).
Susceptibility to the following agents was tested:
HgCl2 (MIC, 2 to 128 µg/ml; Merck Oy),
chlorhexidine diacetate (MIC, 0.25 to 16 µg/ml; Fluka BioChemica,
Bushs, Switzerland), cefuroxime (MIC, 0.063 to 16 µg/ml; Sigma),
benzylpenicillin (MIC, 0.008 to 2 µg/ml; Sigma), and tetracycline
(MIC, 0.063 to 32 µg/ml; Sigma).
The guidelines of the National Committee for Clinical Laboratory
Standards were used for the agar dilution as described earlier (8), with the exceptions mentioned below. Preliminary tests showed that mitis salivarius agar without any supplements had to be
used when testing mercury; Mueller-Hinton II agar (Becton Dickinson and Company, Cockeysville, Md.) supplemented
with blood could not be used, since mercury reacts with the blood.
Bacteria were cultured on mitis salivarius agar with doubling
concentrations of mercury chloride and on Mueller-Hinton agar supplemented with 5% sheep blood and doubling concentrations of the
other antimicrobial agents. The plates were incubated at 35°C in
a 5% CO2 atmosphere and read after 24 h.
Perhaps surprisingly, we found no differences in the MICs of the
studied antimicrobial agents between the samples of the three subject
groups (Table 1). The antimicrobial
resistance profiles for chlorhexidine, cefuroxime, penicillin,
and tetracycline are in line with the results of our previous study
(8). Similar levels of resistance have also been found by
Baker and Thornsberry (1) and Teng et al. (22)
(1998) for penicillin and by Liebana et al. (10) for
penicillin, cefuroxime, and tetracycline.
0066-4804/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Resistance to Mercury and Antimicrobial Agents in
Streptococcus mutans Isolates from Human Subjects in
Relation to Exposure to Dental Amalgam Fillings
ABSTRACT
Top
Abstract
Text
References
TEXT
Top
Abstract
Text
References
TABLE 1.
In vitro susceptibilities of 839 clinical isolates of
mutans streptococci to mercury and 279 consecutive isolates of
these to four other antimicrobial agents
In conclusion, mercury derived from dental amalgam fillings did not
select resistant S. mutans strains. Based on these
results, we can speculate on at least three topics. First, the
amounts of mercury found in saliva might not be high enough to
cause any selection pressure on S. mutans. Second, certain
protective factors
which exist also in human salivahave been found
that are able to influence mercury resistance, especially in
gram-negative bacteria. It seems that Ca2+ and
Mg2+ ions can directly protect at least gram-negative cells
from the toxic effects of Hg (4). Third, it is also known
that the tripeptide glutathione (
-glutamyl-cysteinyl-glycine), which
is widely present in cells, can increase cellular resistance to
mercury ions in the gram-negative Escherichia coli
(9). We are not aware of any corresponding studies of
gram-positive bacteria, but S. mutans is known to import
glutathione (18). Thus, it may be speculated that the agents
mentioned can also protect gram-positive bacteria against mercury.
Although exposure to mercury from dental amalgam did not select for
resistant strains of S. mutans, the situation may be
different in other streptococci and gram-positive oral genera. In
gram-negative bacteria, the results are contradictory (16,
20). Further systematic studies of multifactorial causal complexes of mercury and antimicrobial resistance in bacteria are needed.
| |
ACKNOWLEDGMENTS |
|---|
This study was supported by the Finnish Dental Association and the Finnish Dental Society.
| |
FOOTNOTES |
|---|
* Corresponding author. Mailing address: National Public Health Institute, Antimicrobial Research Laboratory, P.O. Box 57, FIN-20521 Turku, Finland. Phone: 358-2-2519-255. Fax: 358-2-2519-254.
| |
REFERENCES |
|---|
|
Top
Abstract
Text
References
|
|---|
| 1. |
Baker, C. N., and C. Thornsberry.
1974.
Antimicrobial susceptibility of Streptococcus mutans isolated from patients with endocarditis.
Antimicrob. Agents Chemother.
5:268-271 |
| 2. |
De La Cruz, F., and J. Grinsted.
1982.
Genetic and molecular characterization of Tn21, a multiple resistance transposon from R100.1.
J. Bacteriol.
151:222-228 |
| 3. | Dowson, C. G., T. J. Coffey, C. Kell, and R. A. Whiley. 1993. Evolution of penicillin resistance in Streptococcus pneumoniae; the role of Streptococcus mitis in the formation of a low affinity PBP2B in S. pneumoniae. Mol. Microbiol. 9:635-643[Medline]. |
| 4. |
Farrel, R. E.,
J. J. Germida, and P. Ming Huang.
1993.
Effects of chemical speciation in growth media on the toxicity of mercury(II).
Appl. Environ. Microbiol.
59:1507-1514 |
| 5. | Fujiwara, T., E. Sasada, N. Mima, and T. Ooshima. 1991. Caries prevalence and salivary mutans streptococci in 0-2-year-old children of Japan. Community Dent. Oral Epidemiol. 19:151-154[CrossRef][Medline]. |
| 6. |
Heikkilä, E.,
M. Skurnik,
L. Sundström, and P. Huovinen.
1993.
A novel dihydrofolate reductase cassette inserted in an integron borne on a Tn21-like element.
Antimicrob. Agents Chemother.
37:1297-1304 |
| 7. | Järvinen, H., K. Pienihäkkinen, P. Huovinen, and J. Tenovuo. 1995. Susceptibility of Streptococcus mutans and Streptococcus sobrinus to antimicrobial agents after short-term oral chlorhexidine treatments. Eur. J. Oral Sci. 103:32-35[Medline]. |
| 8. |
Järvinen, H.,
J. Tenovuo, and P. Huovinen.
1993.
In vitro susceptibility of Streptococcus mutans to chlorhexidine and six other antimicrobial agents.
Antimicrob. Agents Chemother.
37:1158-1159 |
| 9. | Latinwo, L. M., C. Donald, C. Ikediobi, and S. Silver. 1998. Effects of intracellular glutathione on sensitivity of Escherichia coli to mercury and arsenite. Biochem. Biophys. Res. Commun. 242:67-70[CrossRef][Medline]. |
| 10. | Liebana, J., A. Castillo, J. Peis, P. Baca, and G. Piedrola. 1991. Antimicrobial susceptibility of 1042 strains of Streptococcus mutans and Streptococcus sobrinus: comparison from 1985 to 1989. Oral Microbiol. Immunol. 6:146-150[Medline]. |
| 11. | Lindqvist, B., S. Edward, P. Torell, and B. Krasse. 1989. Effect of different caries preventive measures in children highly infected with mutans streptococci. Scand. J. Dent. Res. 97:330-337[Medline]. |
| 12. |
Loesche, W. J.
1986.
Role of Streptococcus mutans in human dental decay.
Microbiol. Rev.
50:353-380 |
| 13. |
Nakahara, H.,
T. Ishikawa,
Y. Sarai,
I. Kondo,
H. Kozukue, and S. Silver.
1977.
Linkage of mercury, cadmium, and arsenate and drug resistance in clinical isolates of Pseudomonas aeruginosa.
Appl. Environ. Microbiol.
33:975-976 |
| 14. |
Nunez, L. J.,
G. Schmalz,
J. Hembree, and L. D. Hulett.
1976.
Influence of amalgam, alloy, and mercury on the in vitro growth of Streptococcus mutans. II. Comparison of amalgams and alloys.
J. Dent. Res.
55:893-899 |
| 15. | Ørstavik, D. 1985. Antibacterial properties of and element release from some dental amalgams. Acta Odontol. Scand. 43:231-239[Medline]. |
| 16. | Österblad, M., J. Leistevuo, T. Leistevuo, H. Järvinen, L. Pyy, J. Tenovuo, and P. Huovinen. 1995. Antimicrobial and mercury resistance in aerobic gram-negative bacilli in fecal flora among persons with and without dental amalgam fillings. Antimicrob. Agents Chemother. 39:2499-2502[Abstract]. |
| 17. | Rask, P.-I., C. G. Emilson, B. Krasse, and H. Sundberg. 1988. Effect of preventive measures in 50-60-year-olds with a high risk of dental caries. Scand. J. Dent. Res. 96:500-504[Medline]. |
| 18. |
Sherrill, C., and R. C. Fahey.
1998.
Import and metabolism of glutathione by Streptococcus mutans.
J. Bacteriol.
180:1454-1459 |
| 19. | Skinner, E. W., and R. W. Phillips. 1969. The science of dental materials, 6th ed., p. 303. and 332. W. B. Saunders Co., Philadelphia, Pa. |
| 20. |
Summers, A. O.,
J. Wireman,
M. J. Vimy,
F. L. Lorscheider,
B. Marshall,
S. B. Levy,
S. Bennett, and L. Billard.
1993.
Mercury released from dental "silver" fillings provokes an increase in mercury- and antibiotic-resistant bacteria in oral and intestinal floras of primates.
Antimicrob. Agents Chemother.
37:825-834 |
| 21. |
Tanaka, M.,
T. Jamamoto, and T. Sawai.
1983.
Evolution of complex resistance transposons from an ancestral mercury transposon.
J. Bacteriol.
153:1432-1438 |
| 22. |
Teng, L.-J.,
P.-R. Hsueh,
Y.-C. Chen,
S.-W. Ho, and K.-T. Luh.
1998.
Antimicrobial susceptibility of viridans group streptococci in Taiwan with emphasis on the high rates of resistance to penicillin and macrolides in Streptococcus oralis.
J. Antimicrob. Chemother.
41:621-627 |
| 23. | Tenovuo, J., P. Häkkinen, P. Paunio, and C. G. Emilson. 1992. Effects of chlorhexidine-fluoride gel treatments in mothers on the establishment of mutans streptococci in primary teeth and development of dental caries in children. Caries Res. 88:236-243. |
| 24. | Wireman, J., C. A. Liebert, T. Smith, and A. O. Summers. 1997. Association of mercury resistance with antibiotic resistance in gram-negative fecal bacteria of primates. Appl. Environ. Microbiol. 63:4494-4503[Abstract]. |
Antimicrobial Agents and Chemotherapy, February 2000, p. 456-457, Vol. 44, No. 2
0066-4804/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
This article has been cited by other articles:
-
Sweeney, L. C., Dave, J., Chambers, P. A., Heritage, J.
(2004). Antibiotic resistance in general dental practice--a cause for concern?. J Antimicrob Chemother
53: 567-576
[Abstract] [Full Text] -
Pike, R., Lucas, V., Stapleton, P., Gilthorpe, M. S., Roberts, G., Rowbury, R., Richards, H., Mullany, P., Wilson, M.
(2002). Prevalence and antibiotic resistance profile of mercury-resistant oral bacteria from children with and without mercury amalgam fillings. J Antimicrob Chemother
49: 777-783
[Abstract] [Full Text]
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Copyright © 2009 by the American Society for Microbiology. For an alternate route to Journals.ASM.org, visit: http://intl-journals.asm.org | More Info»