Effect of colicins on diarrheic Escherichia coli

摘要

Shirazi Z. Tahamtan Y., Effect of colicins on diarrheic Escherichia coli, Onl J Vet Res., 19 (10): 653-662, 2015. Colicinogenic E. coli (CEC) strains were tested on verotoxin serotypes O157:H7 (clone 1), five Non-O157:H7 (clone 2) and eight K99 (clone3) strains. DEC and test strains were inoculated onto Luria bertani (LB) broth (O/N). O/N culture of CEC strains was spotted onto LA and LA supplemented mitomycin C (LAM) dry plates previously lawn with DEC. Plates were incubated O/N at 37°C and inhibitory activity against DEC strains was defined as a clear zone around colicin-producing strains. PCR was used to isolate positive and negative virulence factors among DEC strains and colicin gene in CEC strains. Inhibition of DEC strains occurred for 33.3to 94.4% of clones with most and least inhibition related to Col IaIb, E-mix and Col M respectively. The presence of mitomycin C in the LAM medium increased inhibition of colicins and those not inhibited on LA. Sensitivity of DEC strains to colicins wasDEC clone 1 >2 >3 on LA and DEC clone 2 >1 >3 on LAM. Inhibition on LAM medium may have been induced by injury to DEC strains by mitomycin C sensitivity. Insensitivities to colicins on LA and LAM could be due to wild-type DEC strains, immunity genes, loss of genes coding for outer membrane protein receptors, inherent genetic differences in genes regulating production of colicins, host cell SOS system or unknown mechanisms.