Retrospective Observational Study of Salmonella Typhi and their Antimicrobial Susceptibility Pattern in a Tertiary Care Hospital

Background: Salmonella enterica subspecies enterica serotype Typhi (S. Typhi) is mainly responsible for enteric fever. it poses a serious threat to public health in underdeveloped nations like Bangladesh. The growing antibiotic resistance observed in their management necessitates periodic monitoring of susceptibility trends to support therapeutic care at both the national and local levels. Furthermore, this will enable the planning of antibiotic recycling whenever feasible. Objective: To provide a comprehensive understanding of how antibiotic susceptibility has evolved over time, this study aimed to identify Salmonella Typhi and to determine their demographics, seasonal fluctuations, and antibiotic susceptibility. Methods: This retrospective study was conducted in the Department of Microbiology and Immunology, Bangladesh Medical University, Dhaka, Bangladesh, between July 2023 and June 2024. A total of 6572 blood samples were collected in an automated blood culture bottle, and the bacterial profile was retrieved using an automated BACT/ALERT 3D System and BD BACTEC FX continuous monitoring system. The collected blood sample was processed, and full identification of the organism and antimicrobial susceptibility was conducted by using the VITEK 2 Compact Lab automated system and Kirby Bauer disk diffusion methods per the National Committee for Clinical Laboratory Standards guidelines. Results: A total of 6572 blood samples were collected, of which 530(8.06%) showed bacterial growth. Among them, number of total isolated Salmonella Typhi was 105(19.8%). The majority were between the age group 21-30 years old with female predominance and the highest prevalence occurred from November to the month of June. S. Typhi showed highest resistance to azithromycin (75.2%), maximum sensitivity to ceftriaxone and cefixime (100%; MIC £1 µg/ml and £ 0.25 µg/ml respectively) followed by chloramphenicol (88.57%; MIC £ 8 µg/ml) cotrimoxazole (81.90%; MIC £ 20 µg/ml) and ampicillin (64.76%; MIC £ 8 µg/ml). However, the fluoroquinolone class of antibiotics, nalidixic acid (74.4%; MIC £ 32 µg/ml) and ciprofloxacin (72.4%; MIC £1µg/ml) showed higher resistance. Conclusion: The results of this investigation highlighted that the cephalosporin class of antibiotics is still 100% effective, and first-line antibiotics are becoming less resistant suggesting that it may be reintroduced as an empirical treatment for enteric fever. Prescription practices should be changed, and the usage of antibiotics without prescription should be reduced. These findings highlight the need for antimicrobial stewardship programs and the prudent use of antibiotics in Bangladesh's tertiary care hospitals.