Phylogenetic investigations indicate that multiple monophyletic clades (separate or distinct groups in a phylogenetic sense) exist within
Vibrio
, which has led to the reclassification of some species into different genera. The genera covered in this chapter are ubiquitous in aquatic environments, primarily marine waters. Pertinent clinical histories (when known) should accompany specimens to alert the laboratory to include appropriate isolation media for the
Vibrionaceae
in their stool workup; this is especially important in areas where the isolation of
Vibrio
is infrequent. Direct microscopic detection of vibrios in stool is not routinely recommended, since it may not be possible to distinguish pathogenic vibrios from other members of the enteric microbiota. Reagents for the serodiagnosis of cholera are available only in specialized reference laboratories, but titration of acute‐ and convalescent‐phase sera in agglutination, vibriocidal, or antitoxin tests is considered reliable.