Prevalence of Vibrio spp. in raw shrimps (Parapenaeus longirostris) and performance of a chromogenic medium for the isolation of Vibrio strains.

UNLABELLED: Vibrios are natural inhabitants of estuarine ecosystems and some species may pose public health problem as agents of sporadic or collective food-borne infections associated with the consumption of fish or shellfish. Samples of raw shrimp (n = 299), fished in coastal areas of the city of Agadir, Morocco, and collected from its fish marketplace, were examined for the presence of pathogenic vibrios. Microbiological analysis was carried out according to a protocol using thiosulphate citrate bile sucrose (TCBS) agar and CHROMagar Vibrio (CV) as selective media. Presumptive-positive colonies were identified by biochemical and species-specific PCR systems, and further tested by PCR for the presence of pathogenicity factors. The overall prevalence of Vibrio spp. in shrimps was 55·8%. Vibrio parahaemolyticus was recovered from 25 of 299 samples (8·4%), Vibrio cholerae from six samples (2%) and Vibrio alginolyticus from 161 samples (53·8%). No virulence genes were found among V. parahaemolyticus and V. cholerae isolates. The CHROMagar Vibrio plating medium was found to be more efficient than the Thiosulphate Citrate Bile salt Sucrose (TCBS) Agar in the isolation of Vibrio organisms. SIGNIFICANCE AND IMPACT OF THE STUDY: A significant proportion of shrimps marketed and consumed in Morocco are caught in the coastal region of the city of Agadir. This study provides interesting data of prevalence of Vibrio spp. in raw shrimps as well as better understanding of their potential virulence. It is apparent from this study that genes and primers used in multiplex PCR for identification and detection of virulence factors, can be used to monitor shrimps for the presence of potentially pathogenic strains of Vibrio cholerae and Vibrio parahaemolyticus. The results highlight the added value of using a chromogenic medium for research and isolation of pathogenic Vibrio in seafood, more specific and accurate than TCBS.

Performance of a new chromogenic plating medium for the isolation of Listeria monocytogenes from marine environments.

AIMS: This study investigated the performance of a new chromogenic plating medium for the detection of Listeria monocytogenes from naturally contaminated samples obtained from marine environments in Morocco in comparison with the conventional plating media PALCAM and Oxford. METHODS: A total of 479 marine samples (sea water, sediment and mussels) were collected from 16 littoral sites in the region of Agadir (western centre of Morocco). They were examined for the presence of L. monocytogenes using a slight modification of the standardized French method (AFNOR V 08-055) for the detection of L. monocytogenes from food and three different isolation media: PALCAM, Oxford and a new chromogenic plating medium. RESULTS AND SIGNIFICANCE OF THE STUDY: The Oxford and the new chromogenic plating media were found relatively more efficient than the PALCAM medium for the isolation of L. monocytogenes (chi-square test, P < 0.05) from marine samples. However, the new chromogenic plating medium was significantly more selective for L. monocytogenes (P < 0.005) than the two other isolation media as 87.5% of the suspect colonies on this medium were indeed confirmed through identification of the isolates vs 12.7% for Oxford and only 3.8% for the PALCAM medium.

Occurrence of Yersinia enterocolitica in milk and dairy products in Morocco.

A total of 227 samples of milk and dairy products were examined for the presence of Yersinia enterocolitica. Yersinia spp. were recovered from 11 of 30 raw milks (36.6%), one of 20 pasteurized milks (5%), 15 of 63 traditional fermented milks (23.8%), seven of 94 cheeses and one of 20 cream samples (5%). The overall incidence of Y. enterocolitica in milk and dairy products was 6.6%. The other Yersinia species were Y. intermedia, Y. kristensenii, Y. frederiksenii and Y. pseudotuberculosis. Y. enterocolitica was detected only in raw milk (30% of the samples), in traditional fermented milks (6.3%) and in raw milk-made cheese (4%). The majority of the Y. enterocolitica isolates were of biotype 1 (environmental strains). The Celfulodin-Irgasan-Novobiocin (CIN) Agar was found to be more efficient than the Mac Conkey Agar in the isolation of Yersinia organisms.

A bacteriological survey of an oyster-growing area: The Oualidia Lagoon, Morocco.

A 3-year bacteriological survey of an oyster-growing area in Morocco, where the Japanese oyster (Crassostrea gigas) is grown, showed that the contamination of this lagunar ecosystem was not continuous but intermittent and that animal manure and human recreational activities were important sources of pollution. The major source of contamination was of animal origin, except during the summer, when human contamination prevailed.