Phage Types of Vibrio cholerae O1 Biotype E1 Tor Isolated from Patients and Family Contacts in Bangladesh: Epidemiologic Implications

Abstract

The epidemiology of Vibrio cholerae O1 El Tor in rural Bangladesh was examined with a new phage-typing system for characterization of individual strains. During a two-year period, 537 strains were typed with a set of standard and experimental phages. Four major and many minor patterns were identified, some associated with discrete outbreaks of disease and others persisting for the entire period. One outbreak-related phage type was associated with a C plasmid bearing multiple drug resistance. The yearly cholera seasons began with the emergence of strains of many different phage types in many different locations; this pattern is consistent with an environmental reservoir for V cholerae. Each patient with cholera excreted only one phage type over time, whereas some family members were infected with strains of different phage types. Phage typing can be a useful marker with which the spread of cholera strains can be traced in endemic settings.