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Background: Indonesia is one of the five countries with the highest number of diphtheria cases worldwide. Diphtheria is caused by the toxigenic strains Corynebacterium diphtheriae, C. ulcerans, and C. pseudotuberculosis. The diphtheria-causing bacteria can be identified using conventional and molecular methods, including polymerase chain reaction (PCR) assay. We used the PCR assay as additional testing, because in island countries like Indonesia, specimen transport is a serious challenge to maintaining bacterial survival. Objectives: This study aimed to evaluate the PCR assay as additional testing to identify diphtheria-causing bacteria in the diphtheria laboratory. Methods: In this cross-sectional study, a total of 178 pairs of the throat and nasal swabs from diphtheria suspected cases and close contacts were collected from seven provinces in Indonesia in 2016. All samples were directly identified by the conventional method and multiplex PCR assay. Statistical analysis was conducted using the 2 × 2 tables to determine the sensitivity and specificity of both methods, while the χ2 test was used to examine the correlation between specimen examination delay and the differentiation of results. A P-value < 0.05 was considered as statistically significant. Results: Out of 178 examined samples, eight samples were identified as diphtheria-positive by both the conventional method and PCR assay, while nine samples were only detected by the PCR assay. All diphtheria-causing bacteria found in the positive samples were toxigenic C. diphtheriae. The diphtheria-causing bacteria were found in 27.6% of cases and 6.0% of close contacts using the PCR assay versus 13.8% of cases and 2.7% of close contacts using the conventional method. Statistical analysis showed that the PCR assay is about twice more sensitive than the conventional method. There was a significant correlation between the differentiation of results and > 72 hours’ specimen examination delay with a P-value of 0.04 (< 0.05). Conclusions: The PCR assay is more sensitive than the conventional method to identify diphtheria-causing bacteria and may be applied as additional testing to increase the positivity rate of diphtheria-confirmed cases in Indonesia as an archipelago country where geographical factors and specimen transport are real obstacles.

Background: The World Health Organization reported Indonesia as one of the countries with the most prevalent cases of diphtheria worldwide. The microbiological aspects of diphtheria-inducing bacteria are of great significance in tracing disease transmission and case management. However, clinical aspects are critical for updating clinical features and case management in the field, which may sometimes differ from theoretical foundations. Objectives: This study aimed to identify the microbiological and clinical aspects, including molecular typing and case fatality rates, in diphtheria-confirmed cases from the capital city of Indonesia, Jakarta, and surrounding areas in 2017. Methods: The microbiological aspect of 40 diphtheria-confirmed cases were obtained by re-identify diphtheria-inducing bacteria isolated from the samples, while the clinical aspects of the cases were obtained from the medical records and epidemiological data. The chi-square test was used to examine the correlation between fatal cases and myocarditis and diphtheria antitoxin administration delay. In this study, P ≤ 0.05 was set as the significance level. Results: All 40 diphtheria confirmed cases were induced by toxigenic Corynebacterium diphtheriae with two biotypes, namely intermedius (60.0%) and mitis (40.0%). There are six sequence types of bacteria with two main sequence types, ie, ST534 (46.4%) and ST377 (35.7%). The proportions of cases that had a fever and sore throat were 72.5% and 77.5%, respectively; however, the prevalence rates of the cases with pseudomembrane and bull neck were 100% and 47%, respectively. Most cases were administered a combination of penicillin or erythromycin with other antibiotics (40%), and 22.5% of the cases only received penicillin. Myocarditis was noticed in three fatal cases, and their relationship was statistically significant (P = 0.000). All five fatal cases (12.5% of cases) received diphtheria antitoxin (DAT) lately or had not received it yet. Conclusions: Toxigenic C. diphtheriae with two biotypes (namely mitis and intermedius) and two main sequence types (ie, ST534 and ST377) was the causative agent of diphtheria-confirmed cases from Jakarta and surrounding areas in 2017. It was also concluded that those fatal cases were correlated with myocarditis complications.