A Case Series of Diphtheria in Western India: Time to Revisit Vaccination Coverage and Policy?

INTRODUCTION: Diphtheria is a significant child health problem in countries with low immunization coverage. Reports of diphtheria in the adult population are also increasing. Here we describe case series of diphtheria in western India for 6 months. OBJECTIVE: To identify and isolate Corynebacterium species, demonstrate the isolates for toxigenicity and examine the immune status of the patients by estimating antibody titers in sera (anti-diphtheria toxoid IgG). METHODS: Twelve patients admitted with clinical suspicion of oropharyngeal diphtheria for six months. In each case, two throat swabs were collected and primary identification of Corynebacterium diphtheriae was done by direct microscopy (Gram's and Albert's stains), bacteriological culture and biochemical tests as per the standard procedure. Culture isolates were tested for toxigenicity by Elek's gel precipitation and were sent to a reference laboratory for tox A gene detection by polymerase chain reaction. Anti-diphtheria toxoid IgG antibody levels were determined in patient’s sera using a commercial Anti-Diphtheria Toxoid IgG Enzyme-Linked Immunosorbent Assay (EUROIMMUN, Germany) at a reference laboratory. RESULTS: All 12 patients presented with oropharyngeal diphtheria with the formation of pseudomembrane in the oropharynx. Eleven patients were of the pediatric age group and one was an adult. The microbiological diagnosis was achieved for 11 patients and one was diagnosed clinically. Based on vaccination history, microbiological findings and distribution of anti-diphtheria toxoid IgG antibodies titers, the results showed persistence of toxigenic strain of Corynebacterium diphtheriae circulating in our region. CONCLUSIONS: The present study demonstrated that toxigenic strains of C. diphtheriae are circulating in this geographical location which indicates the need for constant epidemiological surveillance ensuring early detection of diphtheria and review the efficacy of the immunization programme.