Argentinean human co-infection cases with two or more serotypes of Shiga toxin-producing Escherichia coli

GALLI L RIVAS, M.; DEZA N; BASCHKIER A; CARBONARI CC; MILIWEBSKY E; CHINEN I; MANFREDI E; D´ASTEK BA; ZOLEZZI G; RIVAS M

Amsterdam

Simposio; 8th International Symposium on Shiga Toxin (Verocytotoxin) - Producing Escherichia coli Infections; 2012

Shiga toxin-producing Escherichia coli (STEC) are important foodborne pathogens which can cause non-bloody diarrhea (NBD), bloody diarrhea (BD), and hemolytic uremic syndrome (HUS). Although some STEC human co-infection cases have been previously reported, the occurrence of non-O157 STEC in co-infections, particularly in presence of E. coli O157:H7, is probably underestimated because laboratory methods to detect these organisms are not commonly used. The objective of the present study was to reveal the serotypes associated with Argentinean STEC co-infection cases received at the National Reference Laboratory in the 2002-2010 period. A conventional multiplex PCR targeting the stx1, stx2 and rfbO157 genes was used to identify STEC in direct and enriched stool samples plated onto sorbitol-MacConkey agar. Isolates with stx genes were identified by standard biochemical tests, serotyped, and characterized by phenotypic and genotypic techniques. For STEC typing, stx and eae genotypes were determined by PCR-restriction fragment length polymorphism. In the 2002-2010 period, multiple STEC serotypes were isolated from fecal samples of fifteen human cases of HUS (n=10), NBD (n=3), and BD (n=2). These infections included the following E. coli associations: O111:NM/O145:NM (n=2), O157:H7/O145:NM (n=2), O26:H11/O157:H7 (n=2), O26:H11/O145:NM (n=1), O103:H2/O157:H7  (n=1), O26:H11/O145:NM/O157:H7 (n=1), O157:H7/ONT:H19 (n=1), O157:H7/ONT:H21 (n=1), O157:H7/ONT:HNT (n=1), O145:NM/ONT:HNT (n=1), O26:H11/non-toxigenic O157:NT  (n=1), and O103:H2/non-toxigenic O157:NT  (n=1). The STEC strains isolated harbored the following genotypes: O157:H7, stx2/stx2c(vh-a)/eae-gama/ehxA; O145:NM, stx2/eae-gama/ehxA; O26:H11, stx1/eae-beta/ehxA; O103:H2, stx1/eae-epsilon/ehxA; O103:H2, stx1/stx2/eae-epsilon/ehxA; ONT:H21, stx2(vh-b), ONT:H19, stx2c(vh-a), and ONT:HNT, stx2(vh-b). Interestingly, O157:H7 was present in most of the cases (10/15, 66.7%), followed by O145:NM (7/15, 46.7%), and O26:H11 (5/15, 33,3%). Further, O157:H7, O26:H11 and O145:NM STEC strains were isolated from one HUS patient and another HUS patient with a O157:H7/ONT:H21 co-infection died. This is the first time that well-documented O157 and non-O157 co-infections are described, and the first time that eae-negative STEC strains (ONT:H19, ONT:H21, ONT:HNT) are described as part of co-infections. Although the significance of non-O157 in co-infections is underestimated, our study revealed that more investigation is granted to determine their real contribution during disease. Further, detection techniques to identify non-toxigenic O157 are required, particularly if these isolates are considered the prototype serotype in the co-infection.