Abstract
This study was carried out on 426 samples of raw meats collected from butcheries and supermarkets in Casablanca, Morocco. The samples were examined for the occurrence of Listeria species. Strains of Listeria monocytogenes were characterized by several biochemical tests and confirmed by polymerase chain reaction (PCR). β-hemolytic cultures and nonhemolytic isolates were tested for biochemical properties with the Listeria API test. Among the 43 Listeria species isolates; we identified 10 strains for L. monocytogenes (23.3%), 31 strains for L. innocua (72.1%) and 2 strains for L. welshimeri (4.6%). Strains of L. monocytogenes were separated by multiplex PCR; two serogroups IIb and IVb were thus differentiated. Antibiotic susceptibility of L. monocytogenes to 21 antibiotics was determined by the disk diffusion method. All isolates were susceptible to a wide range of the tested antibiotics with the exception of nalidixic acid, colistine and cephalosporins second and third generation for which they were all resistant.
Acknowledgements
The authors are grateful to Dr Alban Le Monnier and Dr Alexandre LeClercq from Centre National de Référence des Listeria, Institut Pasteur Paris for their collaboration of the molecular serotyping. We also would like to thank the Casablanca authorities for their help.