Plasmid and chromosomal basis of tolerance to cadmium and resistance to antibiotics in normal bovine duodenal bacterial flora.
Cadmium (Cd) tolerance and antibiotic resistance was studied in duodenal flora of 20 normal bovine samples. Twelve bacterial isolates (5 Staphylococcus spp, 4 Enterococcus faecalis, 2 Bacillus spp, and a Pseudomonas sp) were grown in Luria broth containing 0.05 to 0.8 mM of cadmium chloride (CdCl). All isolates displayed multiple antibiotic resistance, with 2 Enterococcus strains and Pseudomonas pickettii demonstrating resistance to 12/17 antibiotics tested. With the exception of Staphylococcus sp, all contained plasmid DNA. Curing to remove plasmid DNA determined if Cd tolerance and/or antibiotic resistance was plasmid or chromosomally mediated. None of the bacteria became sensitive to CdCl after curing, suggesting that tolerance was not plasmid-mediated. Six bacteria became sensitive to antibiotics after curing indicating that antibiotic2 resistance was plasmid mediated. Two of these bacteria became sensitive to multiple antibiotics; a Staphylococcus sp became sensitive to ampicillin, ceftiofur and cephalothin, and a Enterococcus strain became sensitive to neomycin, oxacillin, and tiamulin. All of the isolates were probed for the presence of known Cd-resistance genes (cadA, cadC, and cadD). DNA-DNA hybridization revealed cadA- and cadC-related sequences in chromosomal DNA of a Staphylococcus sp, an Enterococcus strain, and in plasmid DNA of another Staphylococcus sp. No cadD-related sequences were detected in any of the 12 isolates even under reduced stringency of hybridization.
Bruins
M R
MR
Department of Diagnostic Medicine-Pathobiology, College of Veterinary Medicine, Manhattan, KS 66506, USA.
Kapil
S
S
Oehme
F W
FW
D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics; D015139:Blotting, Southern; D002104:Cadmium / Q000494:pharmacology*; D002417:Cattle; D002875:Chromosomes / Q000187:drug effects* / Q000235:genetics; D004269:DNA, Bacterial / Q000032:analysis; D004352:Drug Resistance, Microbial / Q000235:genetics; D004386:Duodenum / Q000382:microbiology*; D005260:Female; D005798:Genes, Bacterial; D006094:Gram-Positive Bacteria / Q000145:classification / Q000187:drug effects* / Q000235:genetics; D008826:Microbial Sensitivity Tests; D010957:Plasmids / Q000187:drug effects* / Q000235:genetics; D014157:Transcription Factors / Q000235:genetics
D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; C432939:CadR protein, Pseudomonas; D004269:DNA, Bacterial; D014157:Transcription Factors; D002104:Cadmium