Copper-resistant enteric bacteria from United Kingdom and Australian piggeries

Abstract

Thirty-three enteric isolates from Australian (Escherichia coli only) and United Kingdom (U.K.) (Salmonella sp., Citrobacter spp., and E. coli) piggeries were characterized with respect to their copper resistance. The copper resistance phenotypes of four new Australian E. coli isolates were comparable with that of the previously studied E. coli K-12 strain ED8739(pRJ1004), in that the resistance level in rich media was high (up to 18 mM CuS04) and resistance was inducible. Copper resistance was transferable by conjugation from the new Australian isolates to E. coli K-12 recipients. DNA similarity between the new Australian isolates and the pco copper resistance determinant located on plasmid pRJ1004 was strong as measured by DNA-DNA hybridization; however, the copper resistance plasmids were nonidentical as indicated by the presence of restriction fragment length polymorphisms between the plasmids. DNA-DNA hybridization and polymerase chain reaction analysis demonstrated DNA homology between the pco determinant and DNA from the U.K. E. coli, SalmoneUa sp., and Citrobacter freundii isolates. However, the copper resistance level and inducibility were variable among the U.K. strains. Of the U.K. E. coli isolates, 1 demonstrated a high level of copper resistance, 4 exhibited intermediate resistance, and 16 showed a low level of copper resistance; all of these resistances were expressed constitutively. A single U.K. C.freundii isolate had a high level of copper resistance, inducible by subtoxic levels of copper. Transconjugants from one E. coli and one C.freundii donor, with E. coli K-12 strain UB1637 as a recipient, showed copper resistance levels and inducibility of resistance which differed from that expressed from plasmid pRJ1004. We conclude that closely related resistance determinants in nonidentical plasmids are responsible for copper resistance in enteric bacteria isolated at separate geographic locations.

Effect of copper hydroxide sprays for citrus canker control on wild-type Escherichia coli

“…While there are many debates on the existence of viable but nonculturable E. coli in natural systems (Bogosian et al 1996;Winfield and Groisman 2003) and on specific strains of E. coli that can adapt to be able to grow in the presence of copper (Williams et al 1993), typically E. coli is sensitive to copper and does not survive long upon exposure (Noyce et al 2006;Santo et al 2008Santo et al , 2011. Added to the stress of copper toxicity under field conditions are the hostile environs of the leaf and fruit surfaces (McCambridge and McMeekin 1981;Winfield and Groisman 2003;Sunder 2004).…”

“…In studies, when compared to contact with other metals, such as stainless steel, copper had a much higher incidence of E. coli eradication even when abundant moisture and nutrients were available (Noyce et al 2006;Santo et al 2008Santo et al , 2011. Studies that demonstrate the ability of E. coli to achieve homeostasis with copper also show that the resistance level to copper toxicity occurs most often in a rich media, and even in this enriched environment, the ability to become impervious to copper cannot be induced in many strains (Williams et al 1993). The capability of E. coli to adapt to an environment high in copper is extremely variable and unpredictable.…”

Efflux-mediated heavy metal resistance in prokaryotes

“…A plasmid‐encoded copper resistance determinant for E. coli has been known for a long time [9,59,78–86]. However, copper resistance factors encoded by the chromosome of this bacterium were described only recently.…”

Molecular genetics and transport analysis of the copper‐resistance determinant (pco) from Escherichia coli plasmid pRJ1004

“…Copper resistance has been reported in several bacterial species, including Escherichia coil (Tetaz and Luke, 1983;Williams et aL, 1993;Brown et aL, 1994), Pseudomonas syringae (Cooksey, 1987;Cooksey et aL, 1990;Cooksey, 1993), Xanthomonas campestris (Bender et aL, 1990;Voloudakis et aL, 1993;Lee et aL, 1994) Alcaligenes eutrophus (Dressier et aL, 1991) and Streptococcus lactis (Efstathiou and Mackay, 1977) as well as in the cyanobacterium Synechococcus (Gupta et aL, 1992). Resistance to copper in the first three cases may have been selected because of the use of copper in agriculture.…”

“…Resistance to copper in the first three cases may have been selected because of the use of copper in agriculture. Copper is used as a growth promoter in pigs, and a number of copper-resistance determinants with homology to that in E. coli have been identified (Williams et al, 1993). Similarly, the use of copper fungicides may have selected the determinants identified in a variety of Pseudomonas and Xanthomonas plant pathovars (Bender et aL, 1990;Cooksey et aL, 1990;Voloudakis et aL, 1993;Lee et aL, 1994).…”