Characterization of toxigenic Corynebacterium diphtheriae strains isolated in Russia

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 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 of Northern Ossetia — Alania. Among these strains, 5 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 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

Определение противококлюшных антител у школьников с длительным кашлем

Objective: to assess anti-pertussis immunity in schoolchildren aged 7–17 who complained of a prolonged cough during the 11-year follow-up period.  Materials and methods. The study included 1046 patients aged 7 to 17 years who applied to the Consultative and Diagnostic Center of the G.N. Gabrichevsky Research Institute of Epidemiology and Microbiology with complaints of prolonged cough in the period from 2010 to 2020. Blood serums were examined in ELISA with the determination of IgM, IgG, IgA antibodies using RIDASCREEN test system (Germany).  Results. An active infection with the detection of IgM and/ or IgA, IgG antibodies above threshold levels was detected in 51,3% of children with prolonged cough, while annually in a fairly high percentage throughout the follow-up period. Active pertussis infection, established based on the detection of IgM, IgG, IgA antibodies above thresholds in blood serum samples, prevailed in children 12–15 years old, accounting for more than 60% in children with prolonged cough. Antipertussis immunity as a result of childhood vaccination or previous disease was detected in 16.1-20.2% of people in the period 2010–2014 and in 12,8-20,9% in 2015–2020.  Conclusion. The results obtained by us on the study of anti-pertussis immunity in schoolchildren confirm the presence of active latent circulation of the pathogen whooping cough among children of this age cohort and, therefore, the presence of unaccounted for cases of the disease. This confirms the importance of timely diagnosis of pertussis, isolation of children for the period of active infection and justifies the need for the widespread introduction of a second revaccination against pertussis. Цель: оценка противококлюшного иммунитета у школьников 7–17 лет, обратившихся с жалобами на длительный кашель, в течение 11-летнего периода наблюдения.  Материалы и методы. В исследование включено 1046 пациентов в возрасте от 7 до 17 лет, обратившихся в консультативно-диагностический центр Московского научно-исследовательского института эпидемиологии и микробиологии им. Г.Н. Габричевского с жалобами на длительный кашель в период с 2010 по 2020 г. Сыворотки крови исследовали в ИФА с определением IgM, IgG, IgA антител с помощью тест-системы «RIDASCRЕЕN» (Германия). Результаты. Активная инфекция с выявлением антител классов IgM и (или) IgA, IgG выше пороговых уровней выявлена у 51,3% детей с длительным кашлем, при этом ежегодно в достаточно высоком проценте на протяжении всего периода наблюдения. Активная коклюшная инфекция, установленная на основании выявления в образцах сывороток крови антител IgM, IgG, IgA выше пороговых значений, преобладала у детей 12–15 лет, составляя выше 60% у детей с длительным кашлем. Противококлюшный иммунитет в результате проведенной в детстве вакцинации или перенесенного заболевания выявили у 16,1–20,2% лиц в период 2010–2014 гг. и у 12,8–20,9% – в 2015–2020 гг.  Заключение. Полученные нами результаты по изучению противококлюшного иммунитета у школьников подтверждают наличие активной скрытой циркуляции возбудителя коклюша среди школьников и, следовательно, наличие недоучтенных случаев заболевания. Это подтверждает важность своевременной диагностики коклюша, изоляции детей на период активной инфекции и обосновывает необходимость повсеместного введения второй ревакцинации против коклюша.