CHARACTERIZATION AND ANTIBIOGRAM STUDY OF SOME PATHOGENIC BACTERIA ISOLATED FROM FERMENTED DAIRY PRODUCTS IN DHAKA CITY

Abstract

This study aimed to investigate the microbiological quality of various fermented dairy products by isolating different pathogenic bacteria and antibiogram study. A total of 50 samples consisting packaged (n=30) and non-packaged (n=20) were aseptically collected and subjected to microbiological analysis. The samples were cultured on selective media to isolate and identify pathogenic bacteria based on morphological, biochemical, microscopic and molecular characteristics and finally antibiogram study was done for the isolated bacteria. From the study, it was found that the dahi had the highest titratable acidity, with mean values of 1.003%, while lassi, matha, and burhani had lower mean values of 0.51%, 0.63%, and 0.65%, respectively. The Total Viable Count (TVC) of all fermented dairy products ranged from 6 to 8 log CFU/ml, with the mean Total Coliform Count (TCC) being lowest in packaged dahi and highest in nonpackaged burhani.

Furthermore, the Total Salmonella-Shigella Count (TSS) and Total Staphylococcal Count (TSC) is remarkable in non-packaged burhani and non-packaged dahi. Out of the 50 samples in total, 52% contained Escherichia coli, 10% had Staphylococcus, and 4% showed the presence of Salmonella species. In the current research, it was discovered that 52% of the samples contained at least one type of bacteria from three different genera: Staphylococcus, Escherichia coli, and Salmonella. The overall prevalence rate was lower in packaged products (30%) than non-packaged (85%) products. Almost all of the isolated bacteria were resistant to amoxicillin, tetracycline and erythromycin exhibiting less resistance pattern to ciprofloxacin, gentamicin and neomycin. This study revealed that in spite of having high acidity, fermented dairy products sold at different markets in Dhaka city were contaminated with multiple species of antibiotic resistant bacteria.

Keywords: Characterization, pathogenic bacteria, fermentation, antibiogram, dairy products,