Rising Trend of Multidrug Resistant and Extensively Drug Resistant Strains of Salmonella Typhi: A Retrospective Study in a Tertiary Care Hospital of Peshawar

Abstract

Background: Typhoid fever is an infectious disease caused by the Typhi and Paratyphi serovars of Salmonella enterica. Twenty-one million individuals contract enteric fever annually, with the highest number recorded in Pakistan among Asian countries where typhoid is still prevalent. Over the years, there has been a surge in antibiotic-resistant strains of S. typhi, namely extensive (XDR) and multidrug-resistant (MDR), that have received significant amounts of public health concern in the developing world. Despite the efforts made at a local and national level to prevent, timely diagnose, and treat enteric fever, the outbreak of resistant strains of S. typhi with its rising trend is a major setback for controlling enteric fever in developing countries.

Objective: To determine the frequency of extensive and multidrug-resistant strains of Salmonella typhi obtained from positive blood cultures in a tertiary care hospital, MTI-LRH, Peshawar. The findings can help us create awareness with educational campaigns, improve public health measures, and promote mass immunisation.

Methods: A retrospective, cross-sectional study was conducted that involved collecting positive Salmonella Typhi blood culture reports from January 2021 to December 2021 at Lady Reading Hospital (LRH)-MTI, Peshawar. Positive blood cultures of all inpatients and visitors were included of all ages. The data was provided through online medical reports using HMIS (health management information system) by the microbiology laboratory at LRH-MTI and analysed by Statistical Package of Social Sciences (SPSS) version 23. The laboratory used the BacT/ALERT 3D system to test the antibiotic sensitivities of S. typhi. The culture reports were classified into three categories using the WHO criteria: non-drug-resistant group, multidrug-resistant (MDR) that is resistant to chloramphenicol, ampicillin, and trimethoprim-sulfamethoxazole, and extensive drug-resistant (XDR) that is resistant to five kinds of antibiotics (i.e., chloramphenicol, ampicillin, co-trimoxazole, fluoroquinolones, and third-generation cephalosporins).

Results: Of the 279 positive cultures for S. typhi, 201 (72%) were XDR, 78 (28%) were MDR, and none were found sensitive to all drugs (NDR). Males were predominant at 63.1%, and 45% were between 6 and 10 years of age. The majority of cultures were obtained in July, 54 (19.4%), followed by September, 45 (16.1%), with the least in January, 5 (1.8%). In this study, 279 cultures were resistant to chloramphenicol, 278 to ampicillin, 274 to ciprofloxacin, 249 to cefiximen, 248 to ceftriaxone, and 231 to co-trimaxole. Among carbapenems, meropenem was found to have 100% sensitivity, followed by imepenem at 99.6%. Macrolides had a good sensitivity for 79.2% (221) strains.

Conclusion: The extensively drug-resistant species of Salmonella typhi are rising in number, with carbapenems showing the highest response. This would limit the use of oral antibiotics, necessitating the use of intravenous antibiotics.