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

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 and July 4, 2018 in Tiruchirappalli, Tamil Nadu. We interviewed cases using a semi-structured questionnaire to identify common exposures to food, water and places visited.

Results: We identified 7 cases (5 men) during March 25-June 8, 2018, median age 23 years (range: 12-42); all were hospitalized, none died. Eating at Restaurant A (odds ratio [OR]=22) and chicken gravy (OR=16) was associated with illness. Of the 10 workers at Restaurant A, stool culture from 8 did not detect S. Typhi; 2 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.