Antimicrobial Susceptibility Trends in Salmonella enterica Isolates - A 6 Year Study from a Tertiary Care Hospital in North India

BACKGROUNDEnteric fever is a major cause of morbidity and mortality in tropical areas worldwide.The Indian subcontinent bears the major burden of the disease, both in terms of absolute case numbers and drug-resistant strains.In this study, we aimed to investigate the incidence of enteric fever associated with Salmonella enterica and determine its antimicrobial susceptibilities to therapeutic antimicrobials in a tertiary care teaching hospital of Punjab. METHODSThis retrospective and prospective study was conducted at the Department of Microbiology, CMC and Hospital, Ludhiana.All the culture-positive enteric fever cases from June 2013 to June 2019 presenting to our hospital were included in the study.Antimicrobial susceptibility was done as per corresponding CLSI guidelines. RESULTSA total of 944 strains of Salmonella species-Salmonella Typhi 772 (81.78%) and Salmonella Paratyphi A 172(18.22%) were isolated from the blood cultures.Antimicrobial susceptibility for chloramphenicol, ampicillin and co-trimoxazole was found to be 91.97%,98.58% and 100% respectively for S. Typhi strains, whereas it was 94.19%, 97.09% and 100%, respectively for S. Paratyphi A isolates.Ciprofloxacin and ofloxacin susceptibility were 92.23% and 97.67% for S. Typhi, 86.63% and 98.84% for S. Paratyphi A respectively.There is a continuous increase in ciprofloxacin minimum inhibitory concentration values over the time.Majority (98.51%) of Salmonella isolates were nalidixic acid resistant.Although the rate of multi-drug resistant (MDR) Salmonella strains was nil but their reduced susceptibility to fluoroquinolones has restricted their routine empirical use. CONCLUSIONSEnteric fever continues to cause significant morbidity due to delayed diagnosis, inadequate treatment and worsening drug resistance in India and beyond.There has been a reported decline in MDR with a parallel increase in decreased ciprofloxacin susceptibility among S. Typhi.Third generation cephalosporins are the safest choice for empirical use as ampicillin, chloramphenicol or cotrimoxazole are less likely to be preferred because of longer duration of therapy, threat of reemergence of resistance, side effects and higher relapse rates.Judicious use of these antibiotics is mandatory to prevent emergence of resistant strains.