Trends in Epidemiology, Susceptibility Pattern and Serotypes of Salmonellae at a Tertiary Care Hospital, India: An Eight-Year Study (2011 – 2018)

Background: Enteric fever is a global disease. In India, Enteric fever is endemic with Salmonella enterica serovar typhi being the predominant etiological agent. Due to changing antimicrobial resistance patterns, knowledge of local epidemiology, antimicrobial resistance pattern helps in the initiation of appropriate empiric therapy.

Methodology: A prospective study on Salmonellae isolated from blood and stool specimens over an 8 year period was conducted. Antimicrobial susceptibility was done as per The Clinical & Laboratory Standards Institute (CLSI) guidelines. Serotyping was done by using commercial antisera and later confirmed at Central Research Institute, Kasauli.

Results: Out of 52 salmonellae, 43 (82.6%) were from blood and 8 (15.3%) from stool and 1 (1.9%) from pus specimen. We observed a change in spectrum and susceptibility pattern of salmonellae the 8 year study period. In 2011, 2013, 2016 and 2018, Salmonella typhi (serotype-9,12,vi:d:-) was the predominant etiological agent accounting for 81.8% , 66.6%, 51% and 80% of the total cases of salmonella respectively. Salmonella Paratyphi B (4,12:b:1,2) was predominant in 2012 (100% of cases). Salmonella Serotype Typhimurium (4,12;i:1,2) was predominant in 2014 (50%) while Salmonella typhi and S. paratyphi B contributed equally to infections in 2015 (40% each). From 2011, Non-typhoidal salmonellae (NTS) steadily increased. 19 (36.6%).The most effective antimicrobials against typhoidal salmonellae were chloramphenicol, ceftriaxone and co-trimoxazole with all most 100% sensitivity from 2011 to 2018. Ciprofloxacin maintained good sensitivity in 2013, 2014 and 2015, 2016 and 2018 but ampicillin was ineffective in our set-up.

Conclusions: Due to changing trends in spectrum and sensitivity of salmonellae, continuous monitoring is essential.