Evaluation de la contamination microbienne des produits de la mer

Abstract

One hundred and fifty samples of sardines (n = 100) and shrimp (n = 50) were collected from ten fish markets located in three regions in the wilaya of Constantine. These products were provided from fish harbors of Stora, Marsa, Collo, Annaba, El Taref and Jijel, and nine (n = 9) samples of sepia was taken from the same batch (segmented) of the fishing industry (harbor, transportation, displayed products) to search Vibrio, Clostridium sp, Staphylococcus aureus, total and fecal coliforms, Salmonella, and total aerobic mesophilic flora. Detection methods were based on international standards (ISO). Twenty antibiotics (20) were used by the method of agar diffusion Mueller-Hinton to assess the sensitivity of the identified bacteria (n = 21). Strains with multiresistance (MRA) were tested for the presence of plasmids on electrophoresis. E. coli (n = 14) were the subject of research of virulence genes (Stx and eae) on PCR. The bactericidal efficiency of sodium hypochlorite has been tested according to the standard AFNOR NF T72_150, 1995., Three reference strains E. coli CIP (55.30), Pseudomonas aeruginosa (CIP A22) and Staphylococcus aureus (CECT 59) and three others strains isolated from seafood were selected randomly. The results of conventional microbiological analyzes showed a contamination rate of 77.33 %. The dominant pathogenic bacteria in this study are total coliforms isolatd in 80.66 % of samples, fecal coliforms in 80 % of samples and Clostridium sp; in 12% of samples. The results of analyzes of the ice of storage showed the presence of total aerobic mesophilic flora, total and fecal coliforms in 100% of samples, Clostridium sp; in 70 % of samples and E. coli in 50 %. The results of the segmentation of the fishing industry indicate the presence of total aerobic mesophilic flora, total coliforms, faecal coliforms and Clostridium sp; in sepia samples at different rates depending on bacterial sampling points (port, transportation, displayed products) . One strain of E . Coli was identified in samples at the displayed products Serotyping of the isolated strains showed the presence of three enteropathogenic strains of E. coli and Salmonella infantis. The results of sensitivity tests showed that all the Gram-negative bacteria isolated are resistant at 100% to amoxicillin, ampicillin, kanamycin , neomycin , tobramycin, carbenicillin, oxacillin, penicillin, streptomycin, cloxacillin; 95.23% to amoxicillin-clavulanic acid, amikacin, cephalothin, gentamicin ; 90.47% to the tetracycline resistant ; 23.80% to trimethoprim-sulfamethoxazole and cefoperazone ; 28.53% to cefoxitin; 19.04% resistant chloranfénicol and only 4.76% resistant fosfomicyne . Eleven (11) species (52.38%) were found to carry plasmids. The number of these laters is from 1 to 7 according to the bacteria analyzed. The PCR results showed the presence of virulence genes (Stx and eae) in 12 E. coli strains (85.71%). 5 (35.71%) are Stx2; 3 (21.42%) Stx1, Stx2; 3 (21.42%) eae and 1 (7.14%) eae, Stx1. No virulence gene has been detected in 2 (14.28%) of E. Coli strains. The results of the evaluation of the bactericidal efficiency of sodium hypochlorite have shown that the action of this disinfectant depend on bacterial species, as well as the dilutions used. E.Coli (CIP 55.30) and Pseudomonas aeruginosa (CIP A22) are the most sensitives strains, whereas Staphylococcus aureus, is the least sensitive one to the disinfectant activity. The bactericidal activity of this disinfectant when tested on two bacterial strains isolated from seafood (E.coli O125 and Salmonella infantis) is the same.The Growth of the bacteria is observed from the dilution 1/8. Moreover, Hafnia alvei is the most sensitive strain to the activity of the disinfectant. The overall results obtained in this study has informed us with comprehensive information on microbial contamination of seafood, and the potential hazard to the consumer. Thus, the application of good hygiene practices in the field of fisheries could contribute to improve the quality of these products.