Incidence of Diphtheria among Clinically Probable Cases in a Tertiary Care Centre- A Prospective Study

Diphtheria is a vaccine preventable communicable acute infectious disease of upper respiratory tract caused by Corynebacterium diphtheriae (C. diphtheria) which is endemic in India. Delayed diagnosis of the disease leads to spread of infection in the community and causes increased morbidity and mortality in the affected individuals. To reduce the delay, an early attempt for microbiological diagnosis of diphtheria should be done as it is crucial and complimentary to clinical diagnosis. Aim: To know the prevalent toxin producing biotypes of Corynebacterium among the clinically probable cases of diphtheria. Materials and Methods: Throat swab samples from 300 clinical cases of diphtheria were processed by direct microscopy and culture. Microscopic examination was done by direct throat swab and samples were inoculated in Loeffler’s Serum Slope (LSS). Antimicrobial susceptibility testing was done by Kirby-Bauer disc diffusion method. Results were analysed using MS Excel. Results: Out of 300 samples, presumptive diagnosis of diphtheria by microscopic examination of direct throat swab was 3% and swab inoculated in LSS was 10%. Confirmed cases of diphtheria by culture were 48 (16%). A 100% sensitivity was seen for all antibiotics tested for all 48 isolates in antimicrobial susceptibility testing. Conclusion: A shift in the age wise incidence of the disease from pre-school to school age has been observed with more cases reported. C. diphtheriae gravis was the highly prevalent strain isolated. Culture should be considered as confirmatory method for diagnosis.