Salt-starch xylose lysine deoxycholate agar. A single medium for the isolation of sodium and non-sodium dependent enteric gram-negative bacilli

Issues for Microbial Regulation:Aeromonasas a Model

The decision by public health agencies to regulate specific microorganisms that may be found in drinking water can only be made if specific criteria find that a microorganism poses a health risk. These criteria should include: (1) there is a clinical history of an organism causing disease from the ingestion of drinking water; (2) there is epidemiological evidence that drinking water rather than food or other vectors is a major source of disease; (3) there is sufficient evidence that the target organism, if found in water, possesses virulence factors capable of causing disease in humans; (4) there is sufficient evidence that the target organism is not readily removed or inactivated by multi-barrier conventional water treatment process (e.g., coagulation-filtration-disinfection); (5) there is sufficient evidence that the target organism, if surviving conventional treatment, will be viable, virulent, and present in sufficient numbers to cause disease; (6) there are robust analytical methods for the target organism which have acceptable sensitivity, specificity, and reproducibility to measure accurately the presence of the target organism in treated water; and (7) the performance criteria of analytical method(s) for the target organism have been certified by the appropriate public health agency, and there is intra-laboratory field-test performance data to base this certification.

Media for Aeromonas spp., Plesiomonas shigelloides and Pseudomonas spp. from food and environment

Several media are proposed particularly for the detection of Aeromonas spp. but also for Plesiomonas shigelloides and Pseudomonas spp. Some are for general purposes and others specifically for the examination of clinical, environmental or food samples. All media are selective, due to antibiotics, bile salts, dyes and other selective agents, as well as differential, primarily based on the ability of the microorganisms to ferment/not ferment carbohydrates. As with all selective media, the recovery of stressed cells is sometimes prevented and the competing flora is not always completely inhibited so that confirmatory tests need to be made on presumptive positive colonies. The choice of a specific medium for isolation of Aeromonas spp. will always depend on the type of sample to be examined and whether the investigator needs qualitative detection or quantitative recovery. The best medium for quantitative estimation of Aeromonas spp. from food and environmental samples seems to be starch ampicillin agar (SAA), though others might be recommended. There is a need for a comparative study including Rippey Cabelli agar (mA), ampicillin bile salts inositol xylose (MIX) agar, ampicillin dextrin agar (ADA), dextrin fuchsin sulphite agar (DFS) and starch glutamate ampicillin penicillin C-glucose agar (SGAP-10C) in addition to SAA. For routine analysis of environmental and food samples for P. shigelloides, spread plating on inositol brilliant green bile salts (IBB) and plesiomonas (PL) agars is recommended. For Pseudomonas spp., CFC agar permits quantitative recovery of both pigmented and non-pigmented strains from food and environmental samples, whilst at the same time inhibiting most other organisms.

Vibrio parahaemolyticus and related halophilic Vibrios

Approximately 30 years have elapsed since Dr. Fujino's original discovery that Vibrio parahaemolyticus (then termed Pasteurella parahemolytica) was the cause of "summer diarrhea" in Japan. Since that finding, V. parahaemolyticus has been established as a cause of gastroenteritis in numbers and places approaching global proportions. It has been isolated in marine and estuarine areas almost worldwide and despite its halophilic nature, V. parahaemolyticus has been isolated from saline-free waters. The relationship of this organism to the environment reveals a close association with other marine organisms especially copepods on which the Vibrios depend for survival in winter months and growth in summer months. There is a uniquely provocative disparity between human strains of V. parahaemolyticus which are Kanagawa phenomenon (KP) positive and the environmental strains which to a large extent are KP negative, the significance being that pathogenicity is measured according to the Kanagawa phenomenon (hemolytic activity) reaction. The hemolysin of the pathogenic strains is a thermostable, cardiotoxic protein, which thus far has not been implicated in the mechanism(s) which causes human gastroenteritis. The interest in this organism has been widened in recent years by the finding that similar organisms, V. alginolyticus, lactose positive vibrios and group F vibrios also cause serious disease in humans.