Distribution of Coliphages Against Four E. Coli Virotypes in Hospital Originated Sewage Sample and a Sewage Treatment Plant in Bangladesh

Abstract

The distribution of coliphages infecting different Escherichia coli virotypes (EHEC, EIEC, EPEC, ETEC) and an avirulent strain (K-12) in sewage system of a hospital and a sewage treatment plant (STP) was investigated by culture-based agar overlay methods. Coliphages were found in all the samples except stool dumping site in the sewage system of the hospital and lagoon of the STP. Bacteriophage count (pfu/ml) infecting E. coli strains showed the following ascending pattern (EHEC \ EIE-C \ EPEC \ ETEC \ E coli K-12) in all the collected samples except one. Phages capable of infecting avirulent E. coli K-12 strains were present in the highest number among all the examined locations. Phages specific for E. coli K-12 presented high diversity in plaque size on the bacterial lawn. Virulent E. coli specific coliphages rarely produced plaques with diameter of 1-2 mm or over. Conventional agar overlay method was found to be not satisfactory for phage community analysis from primary stool dumping site of the hospital, probably due to the presence of high concentration of antimicrobial substances. The gradual decrease seen in the five groups of coliphage quantity with the ongoing treatment process and then the absolute absence of coliphages in the outlet of the examined treatment plant is indicative of the usefulness of the treatment processes practiced there.

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“…In this study, E. coli O157:H7 (clinical strain) obtained from ICDDR, B (International Center for Diarrheal Disease Research) was used. The bacteriophage PAH6 and P2BH2, isolated from hospital sewage and infectious to E. coli O157:H7 strains with high specificity and lytic activity Alam et al 2011, was employed as the predator for E.coli O157:H7. The infectivity of bacteriophages PAH6 and P2BH2 against E.coli O157:H7 was re-confirmed by following method of Griffith et al2003.…”

“…Intimin is the only potential E. coli O157 adherence factor that has been demonstrated to play a role in intestinal colonization in vivo in an animal model (McKee et al 1996 andKaper et al 1998). Regrettably E. coli O157:H7 infections through natural source do not confer immunity and no vaccine is available yet to provide protection against this pathogen explained by Alam et al 2011, but a number of experimental approaches are being investigated in animals. The concept of phage therapy to treat bacterial infections was born with the discovery of the bacteriophage almost a century ago.…”

The viable but non-culturable state in pathogenic <i>Escherichia coli</i>: A general review

“…5 , 6 E. coli is a non-sporulating, facultative anaerobe 7 that typically colonises the infant gastrointestinal tract within hours of life, from which time on the host and E. coli derive mutual benefit. 8 In the digestive tract, commensal strains are situated in the large intestine, particularly in the caecum and colon. 7 …”