In vitro and in situ conjugal transfer of an R-plasmid among enterobacteriaceae species isolated from meat samples

Abstract

An R‐plasmid donor strain of Escherichia coli isolated from a meat sample was mated with potential bacterial recipients belonging to the family Enterobacteriaceae isolated from ground beef and chicken samples. Nine different strains having different plasmid profiles were used as recipients in broth conjugation experiments. The recipients were identified as Enterobacter cloacae, Hafnia alvei, E. coli, Klebsiella pneumoniae and K. oxytoca. Of 1250 ampicillin resistant, tetracycline sensitive colonies tested, the incidence of recipients was estimated to be 3% (in ground beef) and 11% (in chicken) of the bacteria population. Two of the recipients, E. coli and K. Oxytoca also behaved as donors and transferred their R‐plasmids to a laboratory recipient strain of E. coli K12‐711. In vitro R‐plasmid transfer frequencies varied within a wide range, from 10−2 to 10−7 among recipients. Generally, frequencies of plasmid transfer were highest at 30°C and declined with decreasing temperature. Three of the recipient isolates, E. cloacae, H. alvei and E. coli displayed transfer of R‐plasmids at 10°C in broth matings. Similar trends in R‐plasmid transfer frequencies also were observed under in situ mating conditions in raw ground beef and pasteurized milk samples.

Occurrence of aminoglycoside phosphotransferase subclass I and II structural genes among Enterobacteriaceae spp. isolated from meat samples

“…The E. coli ECT24 harbouring pRPJ24 (Km R, Nm R, Tc R) strain was isolated from a turkey meat sample (Jayarathe et al 1989). The Enterobacter cloacae 94R recipient was isolated from a ground beef sample (Jayaratne et al 1989). Reference bacterial strains, E. coli PS1323 and E. coli PRC321 harbouring plasmids pGH54 and pSAY16, respectively, were provided by Dr. F. C. Tenover, Veterans Administration, Medical Center, Seattle, Wash, USA.…”

“…Kanamycin-resistant isolates were isolated by surface plating 100 ixl aliquots of serial dilutions of blended meat samples on VRBA supplemented with 1% (w/v) glucose and 25 ~tg/ml kanamycin sulphate as described previously (Jayaratne et aL 1989). One hundred randomly selected colonies were obtained from each sample source and maintained in LB broth containing 15% (v/v) sterile glycerol at -2 0 ° C.…”

Progress towards understanding the fate of plasmids in bacterial communities

“…Successful horizontal transfer of sequences that confer adaptive traits can significantly alter the ecology of the recipient bacterium, allowing colonization of otherwise hostile niches. An important example of this is the acquisition of antibiotic resistance as a result of plasmid transfer, which has been demonstrated for numerous bacterial genera in diverse habitats, such as wastewater (Mach & Grimes, 1982), animal products (Jayaratne et al, 1989), and the guts of mice (Mus musculus) (Doucet-Populaire et al, 1992) and house flies (Musca domestica L.) (Petridis et al, 2006). Horizontal transfer is also responsible for dissemination of other potentially ecologically significant traits, such as virulence.…”