RT Journal Article SR Electronic(1) A1 Navarro, Armando A1 Eslava, Carlos A1 Perea, Luis Manuel A1 Inzunza, Alma A1 Delgado, Gabriela A1 Morales-Espinosa, Rosario A1 Cheasty, Thomas A1 Cravioto, AlejandroYR 2010 T1 New enterovirulent Escherichia coli serogroup 64474 showingantigenic and genotypic relationships to Shigella boydii 16 JF Journal of Medical Microbiology, VO 59 IS 4 SP 453 OP 461 DO https://doi.org/10.1099/jmm.0.015602-0 PB Microbiology Society, SN 1473-5644, AB Studies based on the analysis of housekeeping genes indicate that Escherichia coli and all Shigella species, except for Shigellaboydii type 13, belong to a single species. This study analysed the phenotypicand genotypic characteristics of 23 E. coli strains isolatedin different countries from faecal specimens taken from children with diarrhoea.Strains were identified using the VITEK system and typed with rabbit seraobtained against 186 somatic and 53 flagellar E. coli antigens andagainst 45 Shigella somatic antigens. Biochemical analysis of thesestrains showed a typical E. coli profile with a defined reactionagainst both E. coli O179 and S. boydii16 somatic antisera. Agglutination assays for flagellar antigens showed aresponse against H2 in 7 (30 %) strains, H10 in 2 (9 %)strains, H32 in 12 (52 %) strains and H34 in 2 (9 %)strains, demonstrating 4 serotypes associated with this new somatic antigen64474. A serum against one of these E. coli strains (64474)was prepared. Absorption assays of S. boydii 16 and E. coli 64474 antisera with E. coli O179 antigen removedthe agglutination response against this O179 antigen completely, while theagglutination titres against both S. boydii 16 and E. coli 64474 remained the same. Four (17 %) E. coli strains showed antimicrobial resistance to piperacillinonly, one (4 %) to piperacillin and trimethoprim/sulfamethoxazole,one (4 %) to ciprofloxacin, nitrofurantoin and piperacillin,and two (9 %) strains were resistant to ciprofloxacin,norfloxacin, ofloxacin, piperacillin and trimethoprim/sulfamethoxazole.With regards to PCR assays, one (4 %) of the strainswas positive for Shigella gene ipaH, one (4 %)for ipaA, two (9 %) for ipaB, one (4 %)for ipaD, two (9 %) for sepA andthree (13 %) for ospF. The rfb genecluster in the E. coli strains was analysed by RFLP and comparedwith the gene cluster obtained from S. boydii 16. The rfb-RFLPpatterns for all 23 E. coli strains were similar to thoseobtained for S. boydii 16. The results from PCR tests todetect rfb genes wzx (encoding O unit flippase)and wzy (encoding polymerase) belonging to a cluster relatedto the biosynthesis of the S. boydii 16-specific O antigen were positivein 21 (91 %) and 22 (96 %)of the strains, respectively. PCR assays to detect E. colivirulence genes were also performed. These assays detected enterotoxigenic E. coli genes ltA1 in 12 of the strains (52 %), st1a in 4 (17 %), cfa1 in 6 (26 %), cs1 in 1 (4 %), cs3 in 3 (13 %), cs13 in 9 (39 %) and cs14 in 5 (22 %)of the strains. Results from the PFGE analyses confirmed the wide geographicaldistribution of these strains suggesting that 64474 : H2, 64474 : H10,64474 : H32 and 64474 : H34 are new serotypesof E. coli strains with a defined virulence capacity, andshare a common O antigen with S. boydii 16., UL https://www.microbiologyresearch.org/content/journal/jmm/10.1099/jmm.0.015602-0