Distribution and diversity of a cadmium resistance (cadA) determinant and occurrence of IS257 insertion sequences in Staphylococcal bacteria isolated from a contaminated estuary (Seine, France)

Abstract

Water and sediments of the Seine estuary are contaminated by chemicals, especially cadmium, which favors survival and growth of cadmium-resistant bacteria. We investigated the diversity of the cadA gene, which encodes a Cd(2+)/ATPase protein transporter, in the microbial community of the Seine estuary. The cadA gene first isolated from S. aureus (pI258) was prevalent, with a conservation better than 98% identity, despite its presence in host bacteria of diverse species and genera. We report for the first time, eleven distinct Staphylococcus species, and also bacteria belonging to the Micrococcus and Halobacillus genera carrying the cadA gene. This cadA determinant was mostly plasmid-borne in the Staphylococcus genus, and IS257 sequences, which are known to participate in antibiotic resistance gene dissemination in S. aureus, were found to be located near to the cadA gene in 16/31 cadmium-resistant Staphylococcus strains and one Micrococcus strain. This suggests that IS257 has also contributed to the dissemination of the cadA resistance gene among staphylococci. These findings also emphasize on the existence of Staphylococcal bacteria in contaminated natural niches outside hospital environments.

Staphylococcus saprophyticus Causing Infections in Humans Is Associated with High Resistance to Heavy Metals

“…This system had been described in S. aureus and E. coli, among others, to mediate resistance to arsenic (8). Like for arsenic, for cadmium, there was a strong association between resistance present in 20% of the population and the presence of a specific cad gene system (cadA or cadC and cadD-cadX) that encodes resistance to cadmium in S. aureus (27,45,46). For these reasons, we proposed that the ECV of $1,600 mg/liter for arsenic and $200 mg/liter for cadmium should be considered in S. saprophyticus.…”

Geochemical and metagenomics study of a metal-rich, green-turquoise-coloured stream in the southern Swiss Alps

“…Several components of other transport systems related to metals or chemical species measured in the environmental chemical analysis were found in the metagenomic data. Transporting ATPases for copper (ActP) [68], silver (SilP) [69,70], cadmium/zinc/cobalt (CadA) [71,72], zinc (ZiaA) [73,74], calcium (PacL, YloB) [75,76], magnesium (MgtA and MgtB) [77] and potassium (KdpA-C) [78], as well as other transporters were found for iron (FieF) [63,79], ammonium (NrgA) [80,81], magnesium (MgtE) [82], manganese (MntB,H,R) [83], nitrate/nitrite (NrtA and NrtP) [84], sodium (SdcS) [85], Zinc (ZitB) [86], cobalt/magnesium (CorA) [87,88]. Import systems were found for phosphate (PstB, PhnD) [66,89] and an antiporter for cadmium/cobalt/zinc vs. proton/potassium (CzcD) [62,90,91], as well as for sodium (NhaA,C,D, GerN, NhaS3) [92], molybdenum (ModA,B), nickel (LarO) or potassium (NhaP2) [93]vs.…”

Bioremediation of Heavy Metals

“…The plasmid-encoded cad system in S. aureus is the best characterized Cd(II) resistance efflux system. CadA functions as an efflux pump that exports Cd(II) from the cell interior [44][45][46]. The gene product of cadC binds Cd(II) as it proposed inside the organism since cadC can bind two Cd(II) ions via a pair of cysteine residues.…”