Sensitivity to Polymyxin B in El Tor Vibrio cholerae O1 Strain, Kolkata, India.

Abstract

To the Editor: The epidemiology of cholera, especially in Africa and Asia, has periodically changed in subtle ways (1). The recent cholera epidemic in Haiti, a Caribbean country with no cholera cases in decades, affected >500,000 persons, caused ≈8,000 deaths, and brought this illness to the forefront of Haitian public health concerns (2,3). This life-threatening disease is caused by Vibrio cholerae, a waterborne bacterium with >200 serogroups, 2 of which, O1 and O139, cause epidemic or pandemic cholera. V. cholerae O1 is categorized as classical and El Tor biotypes, which differ biochemically and have different levels of virulence. Classical strains typically cause more severe illness than El Tor strains, which result in mild or moderate and sometimes asymptomatic cases. However, El Tor strains have replaced classical strains as the cause of cholera; the classical biotype is believed to be extinct, and El Tor strains currently prevail. However, the genetic traits specific to classical strains are still present in environmental and clinical V. cholerae isolates. Currently, all clinical strains of V. cholerae in Kolkata produce classical cholera toxin. Such phenotypic and genetic changes in V. cholerae are being monitored worldwide.