Trying the long drop

These 12 species are significant contributors to gastrointestinal and extra-intestinal diseases in man. Disease is spread through the medium of contaminated water and food. Consumption of raw, improperly cooked or cooked and recontaminated shellfish is a particular problem (lovers of oysters beware!). OxoidÆs new Alkaline Peptone Water (CM1028) is a liquid medium recommended for the enrichment of Vibrio species from clinical samples or for use in the 'hanging drop' method of identification. Some samples may contain low levels of the bacterium. Pre-enrichment in CM1028 allows Vibrio species to grow to detectable levels prior to presumptive identification and plating on a suitable culture medium, such as TCBS (CM0333) or blood agar. The 0.5% (w/v) sodium chloride in CM1028 promotes the growth of V. cholerae, while its alkalinity inhibits most unwanted background flora. Alkaline Peptone Water can also be used for the direct microscopical exam- ination of samples using the 'hanging drop' method, by which the suspended samples are examined for the darting motility characteristic of Vibrio species. Immobilisation of the cells on addition of V. cholerae antiserum then provides a presumptive identification.