Conjugation potential and class 1 integron carriage of resident plasmids in river water copiotrophs.
Plasmid content was investigated in hundred copiotrophic Gram-negative river water isolates that exhibited resistance to four or more antibiotics. A total of seventy-seven isolates were found to carry plasmids of varying sizes. These isolates were primarily grouped as Pseudomonads and members of Enterobacteriaceae on the basis of physiological and biochemical tests. Fifty-six isolates that were rifampicin-sensitive and belonged to Enterobacteriaceae family were chosen as donors for the conjugal transfer assay. Eighteen of the isolates successfully transferred conjugable plasmids to the E. coli DH5alpha recipient. Countable multiple antibiotic resistant transconjugants arose readily and conjugal transfer frequency was in the range of 3.75 x 10(-6) to 1.0 x 10(-1). The most common carriage of resistances conferred by transmissible R plasmids was against ampicillin, cefotaxim and cephalexin. The residence of class 1 integrons on conjugative R plasmids was confirmed in only six transconjugants. Gene cassettes borne on the integrons were identified to be dihydrofolate reductases (dhfrs). The major concern of this study was about the copiotrophs containing self-transmissible R plasmids which may be potential reservoirs of antibiotic-resistance genes and instrumental in dissemination of the same in the environment.
Mukherjee
Shriparna
S
Department of Biotechnology, Microbial Biotechnology Laboratory, University of North Bengal, Raja Rammohunpur, Siliguri-734013, West Bengal, India.
Chakraborty
Ranadhir
R
D001419:Bacteria / Q000235:genetics*; D003227:Conjugation, Genetic; D024881:Drug Resistance, Bacterial / Q000235:genetics; D032023:Integrons; D010957:Plasmids; D011815:R Factors; D045483:Rivers / Q000382:microbiology*