Background: Low and middle income countries are still facing cholera as a major public health threat. During the seventies cholera appeared in the DRC and became endemic. Rehydration treatment and improvement of sanitation are essential for controlling cholera. Antibiotics used to be helpful, but in times of increasing worldwide resistances and in the absence of an efficient vaccine bacteriophages could be of additional help.
We aimed to isolate and select bacteriophages that are virulent against Vibrio cholerae to develop a phage cocktail to control outbreaks and help (prophylactic) patient treatment.
Methods and materials: Bacterial strains (n = 56) originating from the DRC were isolated during 2014-2017 from geographically diverse and distant locations (Kinshasa, Lubumbashi, Uvira, and Bukavu). As reference strain O395 (O1/classical) was used. Bacterial species identification was confirmed by MALDI-TOF (Brüker). Bacterial diversity was determined with rep-PCR geno-fingerprinting (DiversiLab TM, BioMérieux). Bacteriophages obtained from different sources in Haiti (2016) and Georgia (2007–2009) were isolated by classical plaque purification protocol and spotted against Vibrio strains; their titer was normalized to log8 and clearings were scored on appearance. Efficiency of plating of the selected phages was also determined.
Results: Out of the 56 field isolates 44 were shown to be genuine V. cholerae (78%). Their serotype was O1; mostly (>90%) Inaba, a few Ogawa. Genotypically their similarity was >97%. Five phages from Haiti and 11 from Georgia (Black Sea, Lisi and Kumisi lake, Mtkvari river) showed clear lytic activity against the V. cholera isolates. One phage VchXKL had a virulence host-range of 71%.
Conclusion: Sixteen virulent phages, 5 from Haiti and 11 from Georgia, two regions that are at great distances from the DRC (10500 km and 5600 km respectively), were isolated at different time points and could be considered as potential therapeutic and control agents against cholera. Interestingly these virulent phages which were isolated at different geographical locations and time points were shown to lyse a geographical diverse but genotypical similar batch of V. cholerae strains. This observation is promising for the development of phage cocktails to be used as additional tool in cholera preventive measures and outbreak management.
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