Isolation and selection of coliphages as potential biocontrol agents of enterohemorrhagic and Shiga toxin-producing E. coli (EHEC and STEC) in cattle

DINI, CECILIA; DE URRAZA, PATRICIO J.

JOURNAL OF APPLIED MICROBIOLOGY

WILEY-BLACKWELL PUBLISHING, INC

Año: 2010

1364-5072

Aims: To isolate, characterize and select phages as potential biocontrol agentsof enterohemorrhagic and Shiga toxin-producing Escherichia coli (EHEC andSTEC) in cattle.Methods and Results: Sixteen STEC and EHEC coliphages were isolated frombovine minced meat and stool samples and characterized with respect to theirhost range against STEC, EHEC and other Gram-negative pathogens; theirmorphology by electron microscopy; the presence of the stx1, stx2 and cI genesby means of PCR; RAPD and rep-PCR profiles; plaque formation; and acidresistance. Six isolates belonged to the Myoviridae and 10 to the Podoviridaefamilies. The phages negative for stx and cI that formed large, well-definedplaques were all isolated using EHEC O157:H7 as host. Among them, onlyCA911 was a myophage and, together with CA933P, had the broadest hostrange for STEC and EHEC; the latter phage also infected Shigella andPseudomonas. Isolates CA911, MFA933P and MFA45D differed in particlemorphology and amplification patterns by RAPD and rep-PCR and showed thehighest acidity tolerance.Conclusions: Myophage CA911 and podophages CA933P, MFA933P andMFA45D were chosen as the best candidates for biocontrol of STEC and EHECin cattle.Significance and Impact of the Study: This work employs steps for a rationalselection and characterization of bacteriophages as therapeutic agents. Thisreport constitutes the first documentation of STEC and EHEC phages isolatedin Argentina and proposes for the first time the use of rep-PCR as a complementof RAPD on DNA fingerprinting of phages.