Molecular typing of Salmonella enterica serotype Worthington isolates from infantile diarrhoea

Background & objectives: Salmonella Worthington has been known to be a causative agent for childhood diarrhoea. There is a paucity of information on the molecular relatedness of the strains isolated in various hospitals in India. The present study was carried out to attempt molecular typing of a cluster of Salmonella Worthington isolates obtained from cases of infantile diarrhoea during a six month period, from a tertiary care paediatric hospital in Delhi, India. Methods: Nine isolates of S. Worthington obtained from faecal samples of infants suffering from diarrhoea during October 2001 to March 2002, were identified by the conventional biochemical methods and by serotyping. The antimicrobial susceptibility was determined by the disk diffusion method. Molecular typing was done by ribotyping. Results: Eight patients were admitted to 3 different wards of the hospital and one was an outpatient. Four patients including the first patient visited the hospital with diarrhoea as the presenting symptom while five developed diarrhoea after admission. Stool microscopy showed no specific findings. Salmonella Worthington was isolated from stool cultures of these patients. Repeated cultures of the common drinking water source of the hospital and the milk supplied to children from central kitchen were negative for known pathogens. All S. Worthington isolates were resistant to all the beta-lactams tested including third generation cephalosporins. Eight isolates were sensitive to furazolidone and 6 to ciprofloxacin. Molecular characterization by ribotyping revealed four different clones. Interpretation & conclusion: As four different ribotypes of the isolated Salmonella Worthington isolates were identified, it was clear that there was no single source of infection.