JMM Editor's Choice: The changing face of diphtheria in Malaysia

Posted on January 7, 2019   by Microbiology Society

The Journal of Medical Microbiology (JMM) is a journal published by the Microbiology Society, focused on providing a comprehensive coverage of medical, dental and veterinary microbiology and infectious diseases, including bacteriology, virology, mycology and parasitology. This month, Norman Fry, Co-Editor-in-Chief of JMM, has selected an outstanding paper from the January issue to highlight as Editor’s Choice. The paper, titled ‘Molecular characterisation of Corynebacterium diphtheriae isolates in Malaysia between 1981 and 2016’, discusses the changes in the microbial populations that cause diphtheria in Malaysia.

Below, you can see Norman Fry’s synopsis of the paper along with a brief lay summary from the first author. The full paper is free to read for one month on the Journal of Medical Microbiology website here.

Norman Fry - Many countries are seeing a resurgence of potentially life-threatening vaccine-preventable diseases, including diphtheria, due to suboptimal levels of childhood immunisation, waning immunity, increased population movement, political instability and breakdown of healthcare and public health systems. Microbiological characterisation of isolates together with key epidemiological data informs our understanding of microbial populations and disease over time. In their article, Mohd Khalid et al. describe the characterisation of Corynebacterium diphtheriae from Malaysia to investigate a rise in cases, from an average of less than three per year since 1990 to 31 in 2016. Reports collated by the World Health Organization show that this increase in cases in Malaysia was sustained in 2017 with 32 cases. Selected isolates were characterised using phenotypic and genotypic methods including whole-genome sequencing from which multi-locus sequence typing (MLST) data were derived.

Their analyses show that the 2016 cases were caused by new clonal lineages in Malaysia. A number of novel sequence types were identified, one of which (ST453) appeared responsible for an outbreak in the state of Kedah. This article also highlights the utility of existing MLST schemes. Such schemes, together with newer core genome MLST schemes, their accompanying curated databases and bioinformatic tools such as those hosted by the PubMLST.org website, are becoming increasingly important in order to increase our understanding of the spread and transmission of these organisms.

Molecular characterization of Corynebacterium diphtheriae isolates in Malaysia between 1981 and 2016

The number of cases of diphtheria in Malaysia has remained low for nearly three decades, but this changed in 2016 when 31 cases were confirmed by the World Health Organization. To investigate this, we collected, characterised, and performed whole genome sequencing of 15 isolates from the 2016 cases and compared the results with isolates from previous isolations (1981–2010).

We showed that the 2016 cases were caused by emergence and spread of new clonal lineages in Malaysia. We also identified two clonal lineages that has persisted for more than 25 years and could potentially become an important source of diphtheria infection in the country.

Mohd Khairul Nizam Mohd Khalid