Masters Thesis

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Browsing Masters Thesis by Author "NFH2305MS107F"

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    Molecular and Phenotypic Characterization of Virulent, Multidrug- Resistant, and Biofilm-Forming Salmonella spp. in Retail Fish
    (2025-12-15) NFH2305MS107F
    Fish is a widely consumed protein source in Bangladesh, yet retail markets often operate without adequate microbiological monitoring, increasing the risk of foodborne infections. Salmonella spp., a major zoonotic pathogen, is frequently associated with aquatic environments and poses a significant public health threat, particularly when antimicrobial resistance (AMR) and virulence factors converge. A total of 100 fish samples from six major retail markets in Noakhali, Bangladesh, were examined for the presence of Salmonella. Presumptive isolates were identified based on cultural and biochemical characteristics, followed by molecular confirmation using PCR targeting invA. Virulence genes (hilA, fimA), antimicrobial susceptibility against 14 antibiotics, AMR genes (blaTEM-1, blaCTX-M-1, tetA, sul1), and biofilm-forming ability were also assessed to evaluate pathogenic and resistance profiles. Among 145 presumptive isolates, 24 (16.55%) were confirmed as Salmonella spp. All 24 isolates carried the invA gene, while 95.8% and 79.2% possessed hilA and fimA, respectively, indicating substantial virulence potential. Antibiogram profiling revealed multidrug resistance, including complete resistance to ceftazidime (100%) and high resistance to ampicillin (75%) and levofloxacin (50%). PCR detection showed universal carriage of blaTEM-1 (100%), along with blaCTX-M-1 (50%), tetA (29.2%), and sul1 (29.2%). Biofilm assays demonstrated diverse adherence capacities, with several isolates classified as strong biofilm formers, suggesting enhanced environmental persistence and increased risk of cross-contamination. The identification of virulent, multidrug-resistant, and biofilm-forming Salmonella spp. in retail fish markets highlights significant risks to public health and food safety in Bangladesh. The coexistence of virulence genes, AMR determinants, and biofilm-forming capacity underscores the urgent need for improved hygiene practices, regulated antibiotic use in aquaculture, and enhanced surveillance of foodborne pathogens. Although serotyping and whole genome sequencing (WGS) could not be performed due to limited funding and time constraints, these advanced analyses are planned for future work to better understand the genetic diversity and epidemiology of circulating strains.