Association of mercury resistance with antibiotic resistance in the gram-negative fecal bacteria of primates

Abstract

Gram-negative fecal bacteria from three longitudinal Hg exposure experiments and from two independent survey collections were examined for their carriage of the mercury resistance (mer) locus. The occurrence of antibiotic resistance was also assessed in both mercury-resistant (Hg r) and mercury-susceptible (Hg s) isolates from the same collections. The longitudinal studies involved exposure of the intestinal flora to Hg released from amalgam "silver" dental restorations in six monkeys. Hg r strains were recovered before the installation of amalgams, and frequently these became the dominant strains while amalgams were installed. Such persistent Hg r strains always carried the same mer locus throughout the experiments. In both the longitudinal and survey collections, certain mer loci were preferentially associated with one genus, whereas other mer loci were recovered from many genera. In general, strains with any mer locus were more likely to be multiresistant than were strains without mer loci; this clustering tendency was also seen for antibiotic resistance genes. However, the association of antibiotic multiresistance with mer loci was not random; regardless of source, certain mer loci occurred in highly multiresistant strains (with as many as seven antibiotic resistances), whereas other mer loci were found in strains without any antibiotic resistance. The majority of highly multiresistant Hg r strains also carried genes characteristic of an integron, a novel genetic element which enables the formation of tandem arrays of antibiotic resistance genes. Hg r strains lacking antibiotic resistance showed no evidence of integron components.

Antimicrobial resistance patterns in Enterobacteriaceae isolated from an urban wastewater treatment plant

“…Although mercury is present at lower concentrations than the other metals tested, it may be responsible for a selective effect. Indeed, the genetic linkage of antibiotic resistance to mercury salts has been described previously in Gram-negative bacteria (Wireman et al, 1997), namely in IncP plasmids isolated from the activated sludge of a wastewater treatment plant (Dröge et al, 2000). These results support the observations of McArthur & Tuckfield (2000) in stream bacteria, who reported that, in areas in which no antibiotic-resistant bacteria were discharged, a positive correlation between antibiotic resistance prevalence and mercury concentration was observed.…”

Oral bacteria resistant to mercury and to antibiotics are present in children with no previous exposure to amalgam restorative materials

“…However, this was not the case and it may be that mercury resistance genes are linked to tetracycline resistance genes. This association with tetracycline resistance was previously shown in Gram-negative bacteria isolated from primate and human faeces, tetracycline resistance was found in 44% of Hg-resistant strains and in only 27% of Hg-susceptible strains [2].…”

Quantitative, longitudinal profiling of the primate fecal microbiota reveals idiosyncratic, dynamic communities

“…A gap in specimen collection from these two animals occurred between weeks 6 and 8 due to mid-winter holidays. Microbial cultivation, fecal mercury concentrations, and molecular phylogeny work on oral and fecal bacterial isolates from F78 and F79 have been described (Summers et al, 1993;Liebert et al, 1997;Wireman et al, 1997). Specimens were collected (Fig.…”