Diphtheria resurgence in India: A case study from south Karnataka

Case Report: Pharyngeal Diphtheria in a Pregnant Woman from South India

Diphtheria is a vaccine-preventable disease and is caused by toxigenic strains of Corynebacterium diphtheriae. Several case reports have been published in the recent years, and this resurgence of cases has occurred mainly in adolescent and adult populations. Also, several research articles have reported waning immunity against diphtheria in adults who have completed childhood immunization. Thus, it is an important need to conduct larger sero-surveillance studies to understand the cause of rising diphtheria cases. Here, we report a case of a 23-year-old pregnant women of 8 weeks' gestation who presented to the outpatient department with fever, severe throat pain, odynophagia, dysphagia, neck pain, and neck swelling of 3 days' duration. On clinical examination, a gray, leathery membrane was noted on the soft palate. An Albert's stain from the membrane revealed organisms resembling Corynebacterium diphtheriae. Appropriate treatment was initiated immediately, and follow-up examination at 2 weeks from date of discharge was uneventful. The gray membrane had completely resolved. Contact tracing was done and the appropriate antimicrobial agent was administered. This case study indicates the importance of timely clinical and microbiological diagnosis and reinforces the previously reported resurgence of diphtheria infection.

Divergent evolution of Corynebacterium diphtheriae in India: An update from National Diphtheria Surveillance network

Diphtheria is caused by a toxigenic bacterium Corynebacterium diphtheria which is being an emerging pathogen in India. Since diphtheria morbidity and mortality continues to be high in the country, the present study aimed to study the molecular epidemiology of C. diphtheriae strains from India. A total of 441 diphtheria suspected specimens collected as part of the surveillance programme between 2015 and 2020 were studied. All the isolates were confirmed as C. diphtheriae with standard biochemical tests, ELEK's test, and real-time PCR. Antimicrobial susceptibility testing for the subset of isolates showed intermediate susceptibility to penicillin and complete susceptible to erythromycin and cefotaxime. Isolates were characterized using multi locus sequence typing method. MLST analysis for the 216 C. diphtheriae isolates revealed major diversity among the sequence types. A total of 34 STs were assigned with majority of the isolates belonged to ST466 (30%). The second most common ST identified was ST405 that was present in 14% of the isolates. The international clone ST50 was also seen. The identified STs were grouped into 8 different clonal complexes (CC). The majority belongs to CC5 followed by CC466, CC574 and CC209, however a single non-toxigenic strain belongs to CC42. This epidemiological analysis revealed the emergence of novel STs and the clones with better dissemination properties. This study has also provided information on the circulating strains of C. diphtheriae among the different regions of India. The molecular data generated through surveillance system can be utilized for further actions in concern.