Outbreak of ceftriaxone-resistant Salmonella enterica serotype Typhi –Tiruchirappalli, Tamil Nadu, India, June-2018

Abstract Objectives In May 2018, a laboratory network for antimicrobial resistance (AMR) surveillance in Tamil Nadu, India, detected a cluster of Salmonella enterica serotype Typhi (S. Typhi) isolates resistant to ceftriaxone. We investigated to describe the epidemiology and identify risk factors for the outbreak. Methods We conducted unmatched case-control studies. We defined a case as illness (fever with abdominal pain, diarrhea, or vomiting) in a person with blood culture-confirmed ceftriaxone-resistant S. Typhi isolated between January 1–July 4, 2018, in Tiruchirappalli, Tamil Nadu. We interviewed cases using a semi-structured questionnaire for common exposures to food, water, and places visited. Results We identified seven cases (five males) during March 25–June 8, 2018, with a median age of 23 years (range: 12–42 years); all were hospitalized, and none died. Eating at Restaurant A (odds ratio [OR]=22) and chicken gravy (OR=16) was associated with illness. Of the ten workers at Restaurant A, stool culture from eight did not detect S. Typhi; two did not consent to provide samples. Five water samples around the restaurant showed low or no residual chlorine content. Conclusions The investigation highlights the value of AMR surveillance in detecting emerging pathogens and the need for timely investigations, along with strengthening food safety.