Molecular epidemiology and antimicrobial susceptibility of outbreak-associated Corynebacterium diphtheriae in Thailand, 2012.

Infections caused by Corynebacterium diphtheriae remain endemic in many countries. Since the implementation of the DTP (Diphtheria-Tetanus-Pertussis) vaccination program in 1977, only sporadic diphtheria cases have been reported in Thailand. In 2012, a diphtheria outbreak occurred in rural Thailand and 38 cases were reported, with the majority being adults (mean 22.1 years, range 5-72 years). The current study determined the genetic diversity of C. diphtheriae isolated from 83 individuals associated with either sporadic (n = 34) from 1994, 1996, 1997, 1998, 1999, 2000, 2012, and 2018, or 2012 outbreak (n = 49) diphtheria occurrences in Thailand. Antimicrobial susceptibility testing was performed on 41/83 isolates using broth microdilution. All sporadic (n = 27) and epidemic (n = 14) C. diphtheriae isolates (41/41; 100%) were susceptible to erythromycin (≤0.5 µg/ml), clindamycin (≤0.5 µg/ml), gentamicin (≤ 4 µg/ml), ciprofloxacin (≤1 µg/ml), and vancomycin (2 µg/ml), except tetracycline with a resistance rate of 34.1% (14/41 isolates). All isolates were intermediately resistant to penicillin (MIC range, 0.25-2 µg/ml). Multilocus sequence typing (MLST) revealed 17 sequence types (STs) among 83C. diphtheriae isolates. For the 2012 outbreak isolates, the predominant ST was ST243 (n = 34/49; 69.4%), followed by ST245 (n = 5/49; 10.2%) and ST244 (n = 4/49; 8.1%), whereas the main STs among the sporadic isolates were ST248 (n = 15/34; 44.1%), followed by ST209 (n = 7/34; 20.6%) and ST258 (n = 3/34; 8.8%). The ST243 outbreak strain was a single-locus variant of sporadic ST258. Phylogenetic analysis using concatenated sequences of 7 MLST genes from 17 STs revealed that ST243, ST248, and ST258 were located in the same cluster and ST243 appeared to have evolved from ST258, an endemic strain. This study highlights the importance of epidemiological surveillance together with characterization of C. diphtheriae strains to help inform the future control and prevention of diphtheria.

Geographically Diverse Clusters of Nontoxigenic Corynebacterium diphtheriae Infection, Germany, 2016-2017.

From 2016 through the middle of 2017, the German Consiliary Laboratory on Diphtheria noted an increase in nontoxigenic Corynebacterium diphtheriae isolates submitted from cities in northern Germany. Many patients for whom epidemiologic data were available were homeless, alcohol or drug abusers, or both. After performing routine diagnostics and multilocus sequence typing (MLST), we analyzed isolates of sequence type (ST) 8 and previously submitted isolates by whole-genome sequencing. Results were analyzed for phylogenetic relationship by core genome MLST (cg-MLST) and whole-genome single-nucleotide polymorphism profiles. Next-generation sequencing-based cg-MLST revealed several outbreak clusters caused by ST8; the geographic focus was in the metropolitan areas of Hamburg and Berlin. To achieve enhanced analytical depth, we used additional cg-MLST target genes and genome-wide single-nucleotide polymorphisms. We identified patient characteristics and detected transmission events, providing evidence that nontoxigenic C. diphtheriae infection is a potential public health threat in industrialized countries.

Corynebacterium urealyticum: trascendencia histórica de su descubrimiento / Corynebacterium urealyticum: the historical importance of its discovery

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[Diphtheria in Denmark 1956-1989. Occurrence of Corynebacterium diphtheriae and other diphtheria toxigenic bacteria]. / Difteri i Danmark 1956-1989. Forekomsten af Corynebacterium diphtheriae og andre difteritoksigene bakterier.

The public immunization program against diphtheria, established in 1941, has almost eradicated the disease in Denmark, and 1956 became the first year without any notified cases. Since then, toxigenic strains have only been isolated five times--three cases of clinical diphtheria due to Corynebacterium diphtheriae biovar. mitis and two cases of tonsillitis/pharyngitis due to Corynebacterium ulcerans. The source of the infection was not identified in any of the cases. The first case of diphtheria in 1968 was imported from abroad. The following two cases in 1983 and 1985 were due to strains of the same phage type and peptide profile as the strains isolated during the epidemic in Sweden in 1984-1986. This indicates that the Danish cases and the Swedish epidemic derived from the same source. The diphtheria immunity of the Danish population is decreasing, and the level of protection is approaching the Swedish level. The impact is that a situation like that in Sweden may be anticipated with diphtheria epidemic in the lowest socio-economical groups--the skid row dwellers, alcoholics and drug abusers--if the immunization program against diphtheria is not intensified.