Characterization of toxigenic Corynebacterium diphtheriae strains isolated in Russia

Abstract

The aim of the study was to characterize toxigenic strains of Corynebacterium diphtheriae by examining 12 toxigenic strains of C.diphtheriae isolated in Russia between January, 2017 to June, 2019. The morphological, toxigenic and biochemical properties of C.diphtheriae was studied. Genotyping of C.diphtheriae strains was performed by using MLST and dtxR gene sequencing with subsequent phylogenetic analysis. Results. Toxigenic strains of C.diphtheriae were isolated in the Novosibirsk, Samara and Chelyabinsk regions, the Khanty-Mansi autonomous okrug - Yugra as well as the republic Northern Ossetia - Alania. Among these strains, 5 of them were isolated from diphtheria patients (moderate disease found in one case, mild course – remaining patients) and 7 strains were isolated from bacterial carriers. In two cases C.diphtheriae from diphtheria patients were identified as ST25 sequence type, gravis variant; in one case – ST8 type, gravis variant; two cases – ST67 sequence type, mitis variant. In asymptomatic carriers of tox-positive C.diphtheriae strains they belonged to ST25 sequence type, gravis variant – in two cases, ST67 type, mitis variant – in four cases. A sequencing type was not identified in one case. All sequence types were widespread globally being presented by a large number of isolates in the PubMLST and characterized by a substantial amount of derivative sequence types. At the same time, they belonged to different clonal complexes and differed markedly from each other contributing to their reliable difference as assessed by MLST. Study of gene dtxR sequence diversity showed that all allelic variants were typical for the representatives of these a sequence types. New alleles of gene dtxR were not revealed in strains examined. It was shown that non-synonymous substitution C440T leading to A147V amino acid substitution was found solely in one allele distributed in ST8, ST185, ST195 and ST451 types suggesting at late mutation. In contrast, the polymorphism C640A resulting in the amino acid substitution L214I was found not only in the same allele, but also in the basal tree branches indicating that isoleucine was in the ancestral sequence of the protein.

Genomic Epidemiology and Strain Taxonomy of Corynebacterium diphtheriae

“…Sublineage SL5 comprised 39 tox-negative genomes belonging to ST5 (all except 6), ST728, ST741 and 4 genomes for which the ST cannot be defined because they lack a leuA allele call (Figure 4A). ST5 contributed to infections in Belarus from the mid-1990s until at least 2013 [16] and was also recovered from Italy, Australia (Table S1) and Russia [14,53]. As noted above, whereas a majority of ST5 genomes were spuA negative, a distinct subbranch within SL5 possessed the biovar Gravis marker spuA.…”

Effectiveness of Using Liquid Transport Media in Bacteriological Diagnostics of Diphtheria Infection

“…Габричевского Роспотребнадзора, для взятия биологического материала в ряде регионов России используются коммерческие транспортные агаризованные среды Стюарта и Эймса, предназначенные для изучения микрофлоры ротоглотки [9][10][11][12]. Нами ранее проведены исследования [12,13], которые показали, что при помещении биологического материала в агаризованные транспортные среды Эймса и Стюарта и их хранении в условиях комнатной температуры и холодильника в течение 6 ч рост единичных колоний токсигенного штамма C.diphtheriae получен только из большой концентрации микробной взвеси (5х10 4 м.к. ); выдерживание материала при комнатной температуре и в холодильнике в течение 20 ч вело к полной потере патологического материала; подращивание материала в термостате в течение 6 ч не даёт положительных результатов и не позволяет увеличить высеваемость возбудителя дифтерии.…”