Diphtheria in Metro Manila, the Philippines 2006-2017: A Clinical, Molecular, and Spatial Characterization

Assessing the impact of booster vaccination on diphtheria transmission: Mathematical modeling and risk zone mapping

The COVID-19 pandemic caused significant disruptions in the healthcare system, affecting vaccinations and the management of diphtheria cases. As a consequence of these disruptions, numerous countries have experienced a resurgence or an increase in diphtheria cases. West Java province in Indonesia is identified as one of the high-risk areas for diphtheria, experiencing an upward trend in cases from 2021 to 2023. To analyze the situation, we developed an SIR model, which integrated DPT and booster vaccinations to determine the basic reproduction number, an essential parameter for infectious diseases. Through spatial analysis of geo-referenced data, we identified hotspots and explained diffusion in diphtheria case clusters. The calculation of R0 resulted in an R0 = 1.17, indicating the potential for a diphtheria outbreak in West Java. To control the increasing cases, one possible approach is to raise the booster vaccination coverage from the current 64.84% to 75.15%, as suggested by simulation results. Furthermore, the spatial analysis revealed that hot spot clusters were present in the western, central, and southern regions, posing a high risk not only in densely populated areas but also in rural regions. The diffusion pattern of diphtheria clusters displayed an expansion-contagious pattern. Understanding the rising trend of diphtheria cases and their geographic distribution can offer crucial insights for government and health authorities to manage the number of diphtheria cases and make informed decisions regarding the best prevention and intervention strategies.

Endemic erythromycin resistant Corynebacterium diphtheriae in Vietnam in the 1990s

Diphtheria is a potentially fatal respiratory disease caused by toxigenic forms of the Gram-positive bacterium Corynebacterium diphtheriae. Despite the availability of treatments (antitoxin and antimicrobials) and effective vaccines, the disease still occurs sporadically in low-income countries and in higher income where use of diphtheria vaccine is inconsistent. Diphtheria was highly endemic in Vietnam in the 1990s; here, we aimed to provide some historical context to the circulation of erythromycin resistant organisms in Vietnam during this period. After recovering 54 C. diphtheriae isolated from clinical cases of diphtheria in Ho Chi Minh City between 1992 and 1998 we conducted whole genome sequencing and analysis. Our data outlined substantial genetic diversity among the isolates, illustrated by seven distinct Sequence Types (STs), but punctuated by the sustained circulation of ST67 and ST209. With the exception of one isolate, all sequences contained the tox gene, which was classically located on a corynebacteriophage. All erythromycin resistant isolates, accounting for 13 % of organisms in this study, harboured a novel 18 kb erm(X)-carrying plasmid, which exhibited limited sequence homology to previously described resistance plasmids in C. diphtheriae. Our study provides historic context for the circulation of antimicrobial resistant C. diphtheriae in Vietnam; these data provide a framework for the current trajectory in global antimicrobial resistance trends.

Microbiological and Clinical Aspects of Diphtheria-Confirmed Cases from Capital City of Indonesia, Jakarta, and Surrounding Areas in 2017

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.