Mercury released from dental "silver" fillings provokes an increase in mercury- and antibiotic-resistant bacteria in oral and intestinal floras of primates

Abstract

In a survey of 640 human subjects, a subgroup of 356 persons without recent exposure to antibiotics demonstrated that those with a high prevalence of Hg resistance in their intestinal floras were significantly more likely to also have resistance to two or more antibiotics. This observation led us to consider the possibility that mercury released from amalgam ("silver") dental restorations might be a selective agent for both mercuryand antibiotic-resistant bacteria in the oral and intestinal floras of primates. Resistances to mercury and to several antibiotics were examined in the oral and intestinal floras of six adult monkeys prior to the installation of amalgam fillings, during the time they were in place, and after replacement of the amalgam fillings with glass ionomer fillings (in four of the monkeys). The monkeys were fed an antibiotic-free diet, and fecal mercury concentrations were monitored. There was a statistically significant increase in the incidence of mercuryresistant bacteria during the 5 weeks following installation of the amalgam fillings and during the 5 weeks immediately following their replacement with glass ionomer fillings. These peaks in incidence of mercuryresistant bacteria correlated with peaks of Hg elimination (as high as 1 mM in the feces) immediately following amalgam placement and immediately after replacement of the amalgam fillings. Representative mercuryresistant isolates of three selected bacterial families (oral streptococci, members of the family Enterobacteriaceae, and enterococci) were also resistant to one or more antibiotics, including ampicillin, tetracycline, streptomycin, kanamycin, and chloramphenicol. While such mercury-and antibiotic-resistant isolates among the staphylococci, the enterococci, and members of the family Enterobacteriaceae have been described, this is the first report of mercury resistance in the oral streptococci. Many of the enterobacterial strains were able to transfer mercury and antibiotic resistances together to laboratory bacterial recipients, suggesting that the loci for these resistances are genetically linked. Our findings indicate that mercury released from amalgam fillings can cause an enrichment of mercury resistance plasmids in the normal bacterial floras of primates. Many of these plasmids also carry antibiotic resistance, implicating the exposure to mercury from dental amalgams in an increased incidence of multiple antibiotic resistance plasmids in the normal floras of nonmedicated subjects.

Origin and Proliferation of Multiple-Drug Resistance in Bacterial Pathogens

“…The selective agent need not be even an antimicrobial used for treatment but may be another selective agent that favors a trait linked to drug resistance in commensals. For example, exposure of commensal gut flora to mercury during installation and removal of dental fillings selected for drug-resistant strains that were also mercury resistant (82). Genes conferring resistance to environmental hazards such as heavy metals are often transferred between lineages together with antibiotic resistance genes on plasmids (83).…”

Immunological effects of mercury (IUPAC Technical Report)

“…It was observed that bacteria in the oral cavity developed a mercury resistance which is transferred on the same plasmids as some antibiotic-resistances. Therefore, it was postulated that continuous mercury exposure might cause a continuous selection pressure toward an antibiotic-resistant state [145]. Mouth flora of some children also contain bacteria resistant to mercury and to antibiotics [146].…”

Integrated Defense System Overlaps as a Disease Model: With Examples for Multiple Chemical Sensitivity

“…(Whether those not genetically susceptible could also be directly toxically affected by mercury is unknown; many widely divergent opinions and research reports have been published over the last few decades (247,248,(251)(252)(253)(254)(255)(256). Recent reports connect amalgams with oral cavity ill-health (248,257), increase in antibioticresistant bacteria in oral and intestinal cavities (258), multiple sclerosis (259,260), psychological complaints such as depression, excessive anger, and anxiety (261), and cardiovascular symptoms such as fatigue and high blood pressure (262).…”