Stability and infectivity of cytolethal distending toxin type V gene-carrying bacteriophages in a water mesocosm and under different inactivation conditions.
Two cytolethal distending toxin (Cdt) type V-encoding bacteriophages (Φ62 and Φ125) were induced spontaneously from their wild-type Escherichia coli strains and from the lysogens generated in Shigella sonnei. The stability of Cdt phages was determined at various temperatures and pH values after 1 month of storage by means of infectivity tests using a plaque blot assay and analysis of phage genomes using real-time quantitative PCR (qPCR): both were highly stable. We assessed the inactivation of Cdt phages by thermal treatment, chlorination, UV radiation, and in a mesocosm in both summer and winter. The results for the two Cdt phages showed similar trends and were also similar to the phage SOM23 used for reference, but they showed a much higher persistence than Cdt-producing E. coli. Cdt phages showed maximal inactivation after 1 h at 70°C, 30 min of UV radiation, and 30 min of contact with a 10-ppm chlorine treatment. Inactivation in a mesocosm was higher in summer than in winter, probably because of solar radiation. The treatments reduced the number of infectious phages but did not have a significant effect on the Cdt phage particles detected by qPCR. Cdt phages were quantified by qPCR in 73% of river samples, and these results suggest that Cdt phages are a genetic vehicle and the natural reservoir for cdt in the environment.
Department of Microbiology, University of Barcelona, Barcelona, Spain.
Anna
A
Allué-Guardia
Juan
J
Jofre
Maite
M
Muniesa
D001427:Bacterial Toxins / Q000235:genetics*; D001435:Bacteriophages / Q000187:drug effects / Q000235:genetics* / Q000502:physiology* / Q000528:radiation effects; D002713:Chlorine / Q000494:pharmacology; D004202:Disinfectants / Q000494:pharmacology; D004926:Escherichia coli / Q000821:virology; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D008242:Lysogeny; D060888:Real-Time Polymerase Chain Reaction; D012764:Shigella sonnei / Q000821:virology; D013997:Time Factors; D014466:Ultraviolet Rays; D010948:Viral Plaque Assay; D038301:Virus Inactivation; D014867:Water / Q000737:chemistry; D014871:Water Microbiology
D001427:Bacterial Toxins; D004202:Disinfectants; C067044:cytolethal distending toxin; D014867:Water; D002713:Chlorine