Extensively Drug-Resistant Typhoid: Antibiotic Susceptibility Pattern of an Emerging Menace in Karachi

Abstract

Background: Salmonella typhi, a rod-shaped Gram-negative bacterium that stands responsible for causing typhoid fever, in places with poor sanitation and polluted water. Injudicious antibiotic practices have significantly added to the rise of multidrug-resistant (MDR) and extensively drug-resistant (XDR) Salmonella typhi. This study aimed to determine the frequency and antibiotic susceptibility pattern of Salmonella typhi in blood cultures of patients with fever.

Methods: This cross-sectional retrospective study was conducted from November 2018 to November 2019 at Tahir Laboratory, Karachi. All clinically suspected typhoid fever cases were cultured and Salmonella typhi was identified by traditional methods using standard microbiological procedures. Antibiotic susceptibility testing was done by the Kirby-Bauer disk diffusion method and a combined disc test was done to detect Extended Spectrum β-Lactamase production in XDR cases.

Results: Out of 394 samples received for blood culture, 99(25.12%) were gram-positive, 158(40.10%) were gram-negative and 137 (34.7%) showed no growth. In 158 gram-negative samples, 92(58.22%) were of Salmonella typhi, consisting of 40(43.47%) cases of children aged 0-10 years. MDR and  XDR Salmonella typhi isolates were 25(27.2%) and 8(8.7%) respectively,  showing a male preponderance of 20 (60.60%). Both the MDR and XDR strains were sensitive to Meropenem and Azithromycin. Extended Spectrum β-Lactamase production was confirmed by combined disc test in all the XDR cases.

Conclusion: The emergence of multidrug-resistant and extensively drug-resistant Salmonella typhi requires surveillance to see antibiogram trends for empirical therapy and to facilitate the prevention of the spread of the disease.

Keywords: Salmonella typhi; Antibiotic Susceptibility Test; Extensively Drug-Resistant; Multidrug-Resistant.