The 2002 Chandigarh cholera outbreak revisited: utility of MALDI-TOF as a molecular epidemiology tool

In July 2002, an outbreak of cholera occurred in north India with two separate geographical foci. Pulsed field gel electrophoresis (PFGE) was previously used in typing a representative sample of these isolates. This study evaluates the usefulness of MALDI-TOF as an epidemiological tool for typing Vibrio cholerae isolates in comparison with PFGE and Amplified fragment length polymorphisms (AFLP). Forty-six isolates of V. cholerae isolated from stool of patients affected in the July 2002 outbreak were typed using MALDI-TOF. To validate its utility, clinical and environmental isolates previously characterized by PFGE and AFLP were included for dendrogram analysis. All 46 isolates were correctly identified by MALDI-TOF to species level. Two distinct clades appeared on dendrogram using MALDI-TOF corresponding to the two geographical foci of the outbreak. For the study of evolution of organisms from environment, AFLP was superior as it clearly demarcated clinical and environmental isolates. The outbreak was not due to a single clone but due to multiple clones circulating simultaneously, as was seen with PFGE also.

MALDI-TOF appears to be a highly discriminatory, cost-effective and rapid epidemiological typing technique that can be used in the investigation of cholera outbreaks.