ena-STUDY-ISTITUTO SUPERIORE DI SANITA-09-02-2017-15:09:43:703-40
Molecular characterization of human verocytotoxigenic Escherichia coli O26 strains: results of an outbreak investigation in Romania, February to August 2016
At the beginning of 2016, an increase in pediatric haemolytic-uremic syndrome (HUS) cases was observed in Romania. The microbiological investigations allowed to isolate VTEC O26 as the causative agent from most of the HUS cases. An enhanced national surveillance of HUS and severe diarrhoea established all over the country following the identification of the first cases until August 2016 allowed to obtain a total of fifteen strains from the cases. The strains were characterized in terms of virulence markers (i.e. vtx type/subtype, eae, ehxA genes), phylogroup, genetic relatedness, and clonality using PCR-based assays, pulsed-field gel electrophoresis (PFGE), and multilocus sequence typing (MLST). Some of the strains were further characterised through whole-genome sequencing (WGS). Five PCR-defined genotypes were distinguished: vtx1a+vtx2a+eae+ehxA (4 strains), vtx1a+vtx2a+eae (1 strain), vtx2a+eae+ehxA (5 strains), vtx1a+eae+ehxA  (4 strains), and vtx1a+eae (1 strain). All HUS strains harboured vtx2a with or without vtx1a and eae while strains from diarrhoea cases carried exclusively vtx1a and eae genes. The strains were assigned to phylogroup B1 and ST21 as sequence type. PFGE resolved the strains into multiple pulsotypes, indicating a certain geographic segregation of four pulsotypes including multiple-strains. WGS confirmed the results obtained with conventional molecular methods, brought evidence of O26:H11 serotype, and complemented the virulence profiles. This is the first description of VTEC O26 strains from cases of infections in Romania. The bacterial isolates belonged to a rather diverse population suggesting a multi-aetiology outbreak. The virulence content of most strains highlighted a high-risk for severe outcome in the infected patients. An improved national surveillance strategy for VTEC infections need to be further considered.
At the beginning of 2016, an increase in pediatric haemolytic-uremic syndrome (HUS) cases was observed in Romania. The microbiological investigations allowed to isolate VTEC O26 as the causative agent from most of the HUS cases. An enhanced national surveillance of HUS and severe diarrhoea established all over the country following the identification of the first cases until August 2016 allowed to obtain a total of fifteen strains from the cases. The strains were characterized in terms of virulence markers (i.e. vtx type/subtype, eae, ehxA genes), phylogroup, genetic relatedness, and clonality using PCR-based assays, pulsed-field gel electrophoresis (PFGE), and multilocus sequence typing (MLST). Some of the strains were further characterised through whole-genome sequencing (WGS). Five PCR-defined genotypes were distinguished: vtx1a+vtx2a+eae+ehxA (4 strains), vtx1a+vtx2a+eae (1 strain), vtx2a+eae+ehxA (5 strains), vtx1a+eae+ehxA  (4 strains), and vtx1a+eae (1 strain). All HUS strains harboured vtx2a with or without vtx1a and eae while strains from diarrhoea cases carried exclusively vtx1a and eae genes. The strains were assigned to phylogroup B1 and ST21 as sequence type. PFGE resolved the strains into multiple pulsotypes, indicating a certain geographic segregation of four pulsotypes including multiple-strains. WGS confirmed the results obtained with conventional molecular methods, brought evidence of O26:H11 serotype, and complemented the virulence profiles. This is the first description of VTEC O26 strains from cases of infections in Romania. The bacterial isolates belonged to a rather diverse population suggesting a multi-aetiology outbreak. The virulence content of most strains highlighted a high-risk for severe outcome in the infected patients. An improved national surveillance strategy for VTEC infections need to be further considered.