Isolation and Characterisation of Bacteriophages with Lytic Activity Against Virulent <em>Escherichia coli</em> O157:H7: Potential Bio-Control Agents

Abstract

Bacteriophages can provide alternative measures for the control of E. coli O157:H7 that is currently an emerging food-borne pathogen of severe public health concern. This study was aimed at characterising E. coli O157:H7 specific phages as potential biocontrol agents for these pathogens. Fifteen phages were isolated and screened against 69 environmental E. coli O157:H7. Only 3 phages displayed broad lytic spectra against environmental shiga toxin-producing E. coli O157:H7 strains. These 3 lytic phages were designated V3, V7 and V8. Subsequent characterization indicated that they displayed very high degree of similarities despite isolation from different locations. Transmission Electron microscopy (TEM) of the phages revealed that they all had isometric heads of about 73 &amp;ndash; 77 nm in diameter and short tails ranging from 20 - 25 nm in diameter. Phages V3, V7 and V8 were assigned to the family Podoviridae based on their morphology. Pulsed field gel electrophoresis (PFGE) genome estimation of the 3 phages demonstrated identical genome sizes of ~ 69 nm. The latent periods of these phages were 20 min, 15 min, and 20 min for V3, V7 and V8 respectively while the burst sizes were 374, 349 and 419 PFU/ infected cell respectively. While all the phages were relatively stable over a wide range of salinity, temperatures and pH values, their range of infectivity or lytic profile was rather narrow on environmental E. coli O157:H7 strains isolated from cattle faeces. This study showed that the Podoviridae bacteriophages are the dominant E. coli O57:H7-infecting phages harboured in cattle faeces in the North-West Province of South Africa and due to their favourable characteristics can be exploited in the formulation of phage cocktails for the bio-control of E. coli O157:H7 in meat and other meat products.

Characterization of Lytic Phages Isolated from Effluent Water and Soil against E. coli O157:H7

“…With studies conducted by some researchers where high levels of salt, in some cases up to 5M did not affect the phage titer, this agrees with the observed saline stability (Lu and Breidt, 2015;Smolarska et al, 2018). The adverse effect of increasing salt concentration can be due to osmotic pressure exerted on phage capsids preventing the ejection of phage DNA (Evilevitch et al, 2003) or aggregating effect of high salt concentration on phage particles with concomitant reduction in bacterial binding sites (Ateba, and Akindolire, 2019).…”

“…The results obtained in this study indicates that the bacteriophages isolated from e uent water and soil has a lytic activity against E. coli O157:H7 and a large community of bacteria. A motivation for this study was the numerous reports about the occurrence of E. coli O157:H7 which has predominantly emerged in recent years as the causative agent of hemorrhagic colitis in humans (Ateba and Akindolire, 2019). This illness, with characteristic symptoms of bloody diarrhea and abdominal cramps, can progress into a more severe, life-threatening complication known as hemolytic uremic syndrome (HUS) (Sibanyoni et al, 2017).…”

Profile of the Spatial Distribution Patterns of the Human and Bacteriophage Virome in a Wastewater Treatment Plant Located in the South of Spain

“…This result was not surprising since E. coli phages are one of the most common viruses in WWTP [41], and coliphages have been widely employed as indicators and source tracking markers of fecal pollution of water [42]. Particularly, E. coli O157 phage 7 has been used as a biocontrol agent in several food industries, due to the frequent contamination of foods with E. coli O157:H7 [43]. Actually, the great diversity of E. coli phage had been reported widely [41,42].…”

Characterization of Non-O157 STEC Infecting Bacteriophages Isolated from Cattle Faeces in North-West South Africa

“…The characterization of phages for potential use either as alternative treatment or in combination with antimicrobials against foodborne pathogens such as STEC, is an on-going process [21,22]. Additionally, studies have characterized E. coli O157 phages from cattle in the North-West Province, South Africa [23], but this study did not attempt to isolate phages with activity against other serogroups. At the same time, much attention has focused on the big six non-O157-infecting phages globally [24][25][26].…”