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Chapter 17 : Vibrio cholerae Populations and Their Role in South America
The spread of pandemic cholera to South America in the 19th century was probably the consequence of the uncontrolled transport of infected people from regions in Europe where the disease was epidemic. Isolates from the early cholera cases were characterized using a number of phenotypic and molecular typing methods, including multilocus enzyme electrophoresis (MLEE) and ribotyping. These isolates could be distinguished from the seventh pandemic clone by MLEE at just a single locus, leucine aminopeptidase. Epidemic cholera normally occurs in coastal areas and is associated with travelers’ movement worldwide. Several theories were proposed to explain the reemergence of cholera in South America. Two populations of Vibrio cholerae O1 were defined among isolates from 1992 to 1998 in Argentina, based on analysis by randomly amplified polymorphic DNA (RAPD) and pulsed-field gel electrophoresis (PFGE). Isolates carrying the major virulence genes from the CTX phage and tcpA were linked to the Latin American epidemic clone, whereas isolates lacking these pathogenicity-associated factors and showing distinct RAPD and PFGE profiles characterized the other clone named Tucumán. Growth conditions were optimized for hemolysin production, and the fact that Hcp was also found in this study corroborates the hypothesis of coregulation of both proteins and is evidence of a similar mechanism for the Amazonia strain. Research on cholera and V. cholerae is at a very exciting point. New tools are at hand for a more prompt global genetic analysis of strains, allowing a better description of strains and populations of vibrios.