by Bryant Furlow
EPI NEWS
June 3, 2007—Bacterial species exchange genes for
resistance against both antibiotics and heavy metals
on the same mobile bits of DNA, so it stands to
reason that bacteria that evolve resistance to the
mercury in dental fillings may become antibiotic
resistant as well. That is precisely what researchers
at the Eastman Dental Hospital in London discovered
when they compared antibiotic resistance among
bacteria from plaques growing on normal enamel with
that of bacteria on a mercury amalgam.
Within days, the authors report, bacteria on the
mercury almalgam had evolved resistance to both
mercury and antibiotics. The majority (98 percent) of
the mercury-resistant isolates were streptococci.
"Most of the mercury-resistant bacteria were also
resistant to at least one of the six antibiotics
tested, with tetracycline resistance detected most
frequently," reports lead author Derren Ready.
Over 66 percent of mercury-resistant bacteria in the
study were tetracycline resistant.
"It is well established that the primary selective factor
for the promotion of antibiotic resistance is the use of
antibiotics," Ready says. "However, other environ-
mental factors such as exposure to mercury from
[dental] amalgam restorations may still have a role to
play in the spread of antibiotic resistance."
Hospitals have reported fewer strains of mercury-
resistant bacteria since phenylmercury and
thimerosal were abandoned as ingredients for
hospital detergents and disinfectants. Despite
controversy about its safety, mercury amalgam
continues to be used in dentistry.
The authors did not indicate sources of funding for
the research.
EPI NEWS
June 3, 2007—Bacterial species exchange genes for
resistance against both antibiotics and heavy metals
on the same mobile bits of DNA, so it stands to
reason that bacteria that evolve resistance to the
mercury in dental fillings may become antibiotic
resistant as well. That is precisely what researchers
at the Eastman Dental Hospital in London discovered
when they compared antibiotic resistance among
bacteria from plaques growing on normal enamel with
that of bacteria on a mercury amalgam.
Within days, the authors report, bacteria on the
mercury almalgam had evolved resistance to both
mercury and antibiotics. The majority (98 percent) of
the mercury-resistant isolates were streptococci.
"Most of the mercury-resistant bacteria were also
resistant to at least one of the six antibiotics
tested, with tetracycline resistance detected most
frequently," reports lead author Derren Ready.
Over 66 percent of mercury-resistant bacteria in the
study were tetracycline resistant.
"It is well established that the primary selective factor
for the promotion of antibiotic resistance is the use of
antibiotics," Ready says. "However, other environ-
mental factors such as exposure to mercury from
[dental] amalgam restorations may still have a role to
play in the spread of antibiotic resistance."
Hospitals have reported fewer strains of mercury-
resistant bacteria since phenylmercury and
thimerosal were abandoned as ingredients for
hospital detergents and disinfectants. Despite
controversy about its safety, mercury amalgam
continues to be used in dentistry.
The authors did not indicate sources of funding for
the research.
Further reading Ready D, et al. 2007. The effect of amalgam exposure on mercury- and antibiotic-resistant bacteria. International Journal of Antimicrobial Agents (in press), doi:10.1016/j.ijantimicag.2007.02.009. Porter FD, et al. 1982. Selection for mercurial resistance in hospital settings. Antimicrobial Agents and Chemotherapy, 22:852–858. |
Mercury amalgam in fillings helps oral bacteria evolve tetracycline resistance, a new study finds
Antibiotic Resistance
Dental mercury may promote antibiotic resistance
