From August till November 1998, the Paediatric and Anaesthetic Units of Hospital Kuala Terengganu managed three patients from Kuala Terengganu District who were ventilated for respiratory diphtheria. Their ages were 5, 4 and 7 years old and their immunisation for diphtheria were not complete. All three patients presented with respiratory distress and were ventilated for upper airway obstruction. Their treatment included intravenous penicillin and diphtheria antitoxin. One patient died of cardiogenic shock with secondary pneumonia. Pharyngeal and tonsillar swabs of all three patients grew toxigenic Corynebacterium diphtheriae biotype mitis. There were 765 throat cultures taken from contacts. The confirmed positive cultures grew 2 toxigenic and 3 non-toxigenic Corynebacterium diphtheriae biotype mitis and surprisingly, 10 non-toxigenic biotype gravis. A prevalence study is needed to document the endemicity of diphtheria in Kuala Terengganu and to determine the carrier rate of both biotypes. Steps have been taken to increase the immunisation coverage in children. The giving of regular booster doses of diphtheria toxoid to the adult population should be considered.
Sporadic diphtheria cases in Malaysia have remained low in number since the 1990s. However, in 2016 a total of 31 cases were reported nationwide and to investigate this we performed molecular characterization of 30 Corynebacterium diphtheriae isolates collected from 1981 to 2016 using multilocus sequence typing (MLST). C. diphtheriae isolates were identified and biotyped using the API Coryne kit, while the toxigenicity was determined by PCR and the Elek test. All of the 2016 isolates belonged to biotype mitis, caused respiratory diphtheria and were toxigenic strains. MLST analysis identified 17 sequence types (STs), including 11 new ones. ST453 was the most common clone (7/30, 23.3 %), followed by ST141 (5/30, 16.7 %), ST451 (3/30, 10.0 %) and ST248 (2/30, 6.7 %). The clones identified in 2016 had not been detected in previous isolations and they were phylogenetically distinct. Our results suggest that the diphtheria cases in 2016 were caused by the emergence and spread of new clones in Malaysia.
A throat swab from a 9 year old girl with pharyngitis yielded a non-toxigenic strain of Corynebacterium diphtheriae var mitis and Streptococcus group G. C pseudodiphtheriticum was isolated from the throats of two of her four brothers. In each case the isolate was sent to the reference laboratory before full identification. The growth was found to be mixed for one brother; the other isolate being a toxin producing C diphtheriae var gravis. The child was asymptomatic and the case proves that all colonial types on the Hoyles plate should be identified.
In this study, we report the comparative genomics and phylogenetic analysis of Corynebacterium diphtheriae strain B-D-16-78 that was isolated from a clinical specimen in 2016. The complete genome of C. diphtheriae strain B-D-16-78 was sequenced using PacBio Single Molecule, Real-Time sequencing technology and consists of a 2,474,151-bp circular chromosome with an average GC content of 53.56%. The core genome of C. diphtheriae was also deduced from a total of 74 strains with complete or draft genome sequences and the core genome-based phylogenetic analysis revealed close genetic relationship among strains that shared the same MLST allelic profile. In the context of CRISPR-Cas system, which confers adaptive immunity against re-invading DNA, 73 out of 86 spacer sequences were found to be unique to Malaysian strains which harboured only type-II-C and/or type-I-E-a systems. A total of 48 tox genes which code for the diphtheria toxin were retrieved from the 74 genomes and with the exception of one truncated gene, only nucleotide substitutions were detected when compared to the tox gene sequence of PW8. More than half were synonymous substitution and only two were nonsynonymous substitutions whereby H24Y was predicted to have a damaging effect on the protein function whilst T262V was predicted to be tolerated. Both toxigenic and non-toxigenic toxin-gene bearing strains have been isolated in Malaysia but the repeated isolation of toxigenic strains with the same MLST profile suggests the possibility of some of these strains may be circulating in the population. Hence, efforts to increase herd immunity should be continued and supported by an effective monitoring and surveillance system to track, manage and control outbreak of cases.
A 6-year-old boy presented to a university hospital in Malaysia with infective endocarditis complicating cyanotic congenital heart disease. Blood cultures showed a gram-positive, aerobic, coryneform-like bacillus identified by the hospital laboratory as Corynebacterium xerosis, but a reference laboratory identified the organism as a toxigenic strain of Corynebacterium diphtheriae. The two laboratories concurred on all biochemical test results except for sucrose fermentation.