Alam et al (2022): Emergence and Evolutionary Response of Vibrio cholerae to Novel Bacteriophage, Democratic Republic of the Congo

I have been reading the paper by Alam et al (2022): "Emergence and Evolutionary Response of Vibrio cholerae to Novel Bacteriophage, Democratic Republic of the Congo".

Epidemiology

In this paper, the authors sequenced the whole genomes of 24 toxigenic V. cholerae O1 strains belonging to the current pandemic lineage (7PET lineage), and isolated in 2015-2017 from patients in the Democratic Republic of the Congo (DRC). They found that the DRC isolates belonged to two clades, which they denoted as I and II.

Bacteriophages

The authors were interested in figuring out how bacteriophages affect evolution of V. cholerae in DRC, since they may contribute to persistance of some strains and demise of other strains.

An interesting finding in this paper was that in 41% of faecal samples from cholera patients, the authors identified a novel ICP1 (Bangladesh cholera phage 1) bacteriophage. This was genetically distinct from ICP1 isolates previously found in Bangaldesh and India. Some of the DRC strains were found from lab. experiments to be resistant to the novel ICP1 phage, but the mechanism for this resistance is not yet clear.

Curiously, V. cholerae clones that were sensitive to the novel ICP1 phage seem to be propagating more successfully in DRC, while clones that were phage-resistant appeared to have died out. The authors suggested that this may reflect a fitness cost of phage resistance, for example, if phage resistance results in lower virulence.