Report of relapse typhoid fever cases from Kolkata, India: Recrudescence or Reinfection?

Three relapse cases out of 107 hospital attending typhoid cases within a period of 2 years (2014-2016) from Apollo Geneagles hospital, Kolkata, India were reported. Of three cases, two were treated with ceftriaxone for 7 days and one was for 14 days in the first episode of typhoid fever. Six Salmonella Typhi (S. Typhi) isolates, obtained from three patients in both the episodes, were subjected to antimicrobial susceptibility test (AST), detection of QRDR mutation and molecular subtyping by PFGE, MLVA, MLST, CRISPR and H58 haplotyping. Pairs of the S. Typhi strains isolated from each of the two patients during 1^st and 2^nd episodes were similar with respect to the antimicrobial resistance (AMR) profiles, QRDR mutations and molecular subtypes, whereas S. Typhi strain pairs isolated from third patient during the two episodes were different in their AMR profiles, QRDR mutations and MLVA profiles. From the observation, it may be concluded that in spite of treatment of typhoid cases with ceftriaxone for 7-14 days, relapse of typhoid fever might occur. The article also showed the advantage of MLVA typing over PFGE, MLST and CRISPR typing for discrimination of strains isolated from the same patient in case of relapse of typhoid fever.