Plasmid and chromosomal basis of tolerance to cadmium and resistance to antibiotics in normal bovine duodenal bacterial flora

• Published in: Veterinary and human toxicology Vol. 43; no. 3; p. 129
• Main Authors: Bruins, M R, Kapil, S, Oehme, F W
• Format: Journal Article
• Language: English
• Published: United States 01.06.2001
• Subjects: Animals; Anti-Bacterial Agents - pharmacology; Bacterial Proteins - genetics; Blotting, Southern; Cadmium - pharmacology; Cattle; Chromosomes - drug effects; Chromosomes - genetics; DNA, Bacterial - analysis; Drug Resistance, Microbial - genetics; Duodenum - microbiology; Female; Genes, Bacterial; Gram-Positive Bacteria - classification; Gram-Positive Bacteria - drug effects; Gram-Positive Bacteria - genetics; Microbial Sensitivity Tests; Plasmids - drug effects; Plasmids - genetics; Transcription Factors - genetics
• ISSN: 0145-6296

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.