Influence des facteurs environnementaux sur le niveau de contamination microbiologique des zones de production des mollusques bivalves

Abstract

The present work was carried out in order to evaluate the effect of fluctuations in physico-chemical parameters such as temperature, pH, conductivity and salinity on the temporal distribution of different viable bacterial populations in water and mussels from two different sites on the Mostaganem coast: the mussel farm of Stidia and the beach of Sidi Medjdoub. Bacteriological analyzes of water and bivalve molluscs (Mytilus galloprovincialis) were carried out over a period of three months for Stidia (April-June 2022) and two months for Sidi Medjdoub (May-June 2022). on the search for Total Mesophilic Aerobic Germs, faecal pollution indicator bacteria (coliforms total and faecal, faecal E.coli and Streptococcus), and strict pathogenic bacteria (Vibrios, Salmonella, Staphylococci). The results of bacteriological analyzes of the water show sporadic faecal contamination which varies from one month to another and from one site to another. Total, faecal coliforms, E.coli, and faecal Streptococci have been reported in Sidi Medjdoub, and total coliforms in the Stidia mussel farm, and for both sites, the number of bacteria recorded exceeds the guide values and this during the two months of May and June, With regard to mussels, the results showed the presence of Aerococcus viridans in the sample taken in June from the Stidia production site and a total absence of all the other germs sought, whereas a very high number of faecal germs was noted in Sidi Medjdoub throughout the study period with a revealed of pathogenic bacteria such as: Salmonella choleraesuis spp arizonae, Klebsiella oxytoca, Aerococcusviridans, Staphylococus epidermidis, Staphylococcus capitis, vibrio.marinus, and Serratia fonticola. These bacterial loads were quite high during the hottest sampling period in May and June, which shows a correlation of bacterial distribution with water temperature. However, the results of this study remain sporadic and inconclusive. as to the effects of other environmental parameters (pH, salinity and conductivity) on the variation in bacterial loads in all the sites surveyed. These results reveal the anthropogenic effect of continental discharges and the rise of autochthonous bacteria in the summer period which have a considerable influence on the mussels at the Sidi Medjdoub site, and the healthiness of the mussels produced in the Stidia mussel site.