Abstract
BackgroundShiga toxin-producing Escherichia coli (STEC) is one of the most common and widely distributed foodborne pathogens that has been frequently implicated in gastrointestinal and urinary tract infections. Moreover, high rates of multiple antibiotic-resistant E. coli strains have been reported worldwide. Due to the emergence of antibiotic-resistant strains, bacteriophages are considered an attractive alternative to biocontrol pathogenic bacteria. Characterization is a preliminary step towards designing a phage for biocontrol.MethodsIn this study, we describe the characterization of a bacteriophage designated phiC119, which can infect and lyse several multidrug-resistant STEC strains and some Salmonella strains. The phage genome was screened to detect the stx-genes using PCR, morphological analysis, host range was determined, and genome sequencing were carried out, as well as an analysis of the cohesive ends and identification of the type of genetic material through enzymatic digestion of the genome.ResultsAnalysis of the bacteriophage particles by transmission electron microscopy showed that it had an icosahedral head and a long tail, characteristic of the family Siphoviridae. The phage exhibits broad host range against multidrug-resistant and highly virulent E. coli isolates. One-step growth experiments revealed that the phiC119 phage presented a large burst size (210 PFU/cell) and a latent period of 20 min. Based on genomic analysis, the phage contains a linear double-stranded DNA genome with a size of 47,319 bp. The phage encodes 75 putative proteins, but lysogeny and virulence genes were not found in the phiC119 genome.ConclusionThese results suggest that phage phiC119 may be a good biological control agent. However, further studies are required to ensure its control of STEC and to confirm the safety of phage use.
Highlights
Escherichia coli is an innocuous commensal of the gastrointestinal tract; pathogenic E. coli, including Shiga toxin-producing E. coli (STEC), serotype O157:H7, has been identified as one of the major pathogens causing foodborne diseases (Farfan & Torres, 2012)
Bacteriophage, bacterial strain and culture conditions Electron microscopic analysis revealed that phage phiC119 was non-enveloped with an icosahedral capsid of approximately 43–45 nm in diameter and a tail of 168–172 nm in length and 7–9 nm in width
Host range The bacteriophage phiC119 was recently isolated by our lab from horse feces and to determine the susceptibility of bacterial strains to lysis by phage, thirty-three environmental isolates of E. coli, previously isolated at the CIAD, were used for determine the host range of phage phiC119 (Table 1)
Summary
Escherichia coli is an innocuous commensal of the gastrointestinal tract; pathogenic E. coli, including Shiga toxin-producing E. coli (STEC), serotype O157:H7, has been identified as one of the major pathogens causing foodborne diseases (Farfan & Torres, 2012). Implementing strategies to control pathogenic E. coli and other foodborne pathogens is a critical step to strengthen food safety in the region. In this regard, among the potential antimicrobial agents, bacteriophages ( called phages) are promising and sustainable agents that can be used against pathogenic bacteria (Mahony et al, 2011; Guenther et al, 2012; Hungaro et al, 2013). Further studies are required to ensure its control of STEC and to confirm the safety of phage use
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