Multidrug Resistance of Salmonella Isolated from Shellfish Samples, Morocco

Aims: This study aims to determine prevalence of Salmonella in shellfish and to study their resistance to antibiotics.
Samples: Three species of shellfish consisted of cockles, clams and mussels were sampled monthly in six sites during two years 2008 and 2012.
Methodology: As many as 272 samples of shellfish were examined for presence of Salmonella. Positives strains were confirmed for presence of invA gene, serotyping and tested for drug susceptibility.
Results: Up to 7.7% of samples were positive for Salmonella and a total of 90 Salmonella isolates belonging to 4 serovars (S. Kentucky, S. Glostrup, S. Newport and S. Reading) were tested for their susceptibility to a panel of 12 antimicrobial agents. Many resistant isolates were detected with 75.8% of isolates resistant to at least one antimicrobial agent. Isolates demonstrated resistant to streptomicin, chloramphenicol, nalidixic acid, ciprofloxacin, amoxicillin, respectively with (90.6%; 51.6%; 31.6%; 30.5% and 19%). The most common pattern of multiple drug resistance included resistance to chloramphenicol, ciprofloxacin, nalidixic acid.
Conclusion: It seemed that strains isolated of Salmonella were multidrug resistant and almost one third of strains were resistant to quinolone.
The results emphasize the need of a monitoring programme of bacterial pathogenes Salmonella on shellfish to protect human health.