http://localhost:8080/handle/123456789/4985 Sat, 18 Apr 2026 19:26:16 GMT 2026-04-18T19:26:16Z http://localhost:8080/handle/123456789/5263 STUDY ON ISOLATION, CHARACTERIZATION AND IDENTIFICATION OF LACTIC ACID BACTERIA DERIVED FROM FERMENTED DAIRY PRODUCTS RAHMAN, ABDUR Lactic acid bacteria (LAB) are important in dairy food fermentation which have beneficial health properties. The research was conducted to isolate, characterize and identify the LAB derived from fermented dairy products like dahi, borhani, matha, lassi, cheese and to assess their antibiotic susceptibility patterns. The bacteria were isolated based on their colony morphology on de Man, Rogosa, and Sharpe (MRS) agar and selected based on gram-staining properties, biochemical properties and molecular tests. Salt tolerance, sugar fermentation and growth at different temperatures and salt concentrations were observed for all isolates. PCR followed by 16S rDNA sequencing was done to identify the bacteria. All isolates survived at low (≤5%) NaCl concentration, but could not tolerate high (≥6%) NaCl concentration. All isolates can ferment glucose, sucrose, and lactose. All the tested isolates were sensitive to antibiotics like gentamicin, ciprofloxacin, tetracycline and ceftriaxone. Finally, the identified bacterial species were Lactobacillus rhamnosus from dahi, lassi and matha samples and Lactobacillus fermentum was identified from the cheese sample which are known as probiotic species. Ultimately, the research revealed two antibiotic-sensitive LAB species suitable for incorporation into fermented dairy product formulations. A thesis Submitted to the Department of Dairy Science Faculty of Animal Science and Veterinary Medicine Sher-e-Bangla Agricultural University, Dhaka in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE IN DAIRY SCIENCE Sat, 01 Jan 2022 00:00:00 GMT http://localhost:8080/handle/123456789/5263 2022-01-01T00:00:00Z http://localhost:8080/handle/123456789/5262 CHARACTERIZATION AND ANTIBIOGRAM STUDY OF SOME PATHOGENIC BACTERIA ISOLATED FROM FERMENTED DAIRY PRODUCTS IN DHAKA CITY SULTANA, MST. TASMIM 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, A Thesis Submitted to the Department of Dairy Science Sher-e-Bangla Agricultural University, Dhaka in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE IN DAIRY SCIENCE Sat, 01 Jan 2022 00:00:00 GMT http://localhost:8080/handle/123456789/5262 2022-01-01T00:00:00Z http://localhost:8080/handle/123456789/4987 MICROBIAL ASSESSMENT OF RAW AND PROCESSED MILK ALONG WITH ANTIBIOGRAM PROFILING OF SELECTED ISOLATED BACTERIAL SPECIES BISWAS, LITA Milk and dairy products are essential reservoirs for many foodborne pathogens. The most common pathogenic bacterial species in contaminated milk are Escherichia coli and Staphylococcus aureus, which are major public health concerns. Therefore, the objective of the current study was to determine the total bacterial count and identify E. coli and S. aureus along with their antibiotic sensitivity pattern from bovine milk. 41 milk samples consisting raw (n=29) and pasteurized (n=12) were collected from several dairy farms and retail outlets in some selected regions of Dhaka and analyzed for cultural, staining, and biochemical characteristics, followed by polymerase chain reaction (PCR) targeting the 16S rRNA of E. coli and the nuc gene of S. aureus. In addition, the antimicrobial susceptibility profile of the isolates was determined by the disc diffusion method. The highest Total Viable Count (TVC) for raw milk was recorded at 7.0 log cfu/ml for retail outlets, while the lowest TVC was 6.72 log cfu/ml for dairy farms. Also, the highest coliform count (CC) (was 5.87 log cfu/ml in retail outlets compared to 5.57 log cfu/ml in dairy farms for raw milk and 3.4 log cfu/ml for pasteurized milk. Overall, 44.83% of E. coli (n=13) and 60.71% (n=17) of S. aureus were found to be positive in raw milk by PCR test, of which the prevalence was 36.36% (n=4) in dairy farms and 50% (n=9) in retail outlets for E. coli, and 54.54% (n=6) and 61.11% (n=11) for dairy farms and retail outlets respectively for S. aureus. However, this study did not detect pathogenic E. coli and S. aureus in pasteurized milk. A large number of E. coli were resistant to ampicillin (84.61%), amoxicillin (76.92%), cotrimoxazole, erythromycin, and tetracycline (61.53%); however sensitive to gentamycin (92.3%), and levofloxacin (69.23%). Though several isolates of S. aureus showed sensitivity to gentamycin (76.47%), levofloxacin (70.59%), and azithromycin (58.82%), but highly resistant to amoxicillin (88.23%), ceftriaxone (82.35%), ampicillin (76.47%), and erythromycin (52.94%). This study showed that E. coli and S. aureus are widespread in raw milk samples and may develop antibiotic resistance, which might be a public health concern. A Thesis Submitted to the Department of Dairy Science Sher-e-Bangla Agricultural University, Dhaka, in partial fulfilment of the requirements for the degree of MASTER OF SCIENCE (MS) IN DAIRY SCIENCE Sat, 01 Jan 2022 00:00:00 GMT http://localhost:8080/handle/123456789/4987 2022-01-01T00:00:00Z