CHARACTERIZATION OF A LARGE PLASMID IN SHIGA TOXIN-PRODUCING Escherichia coli O157 AND NON-O157 STRAINS ISOLATED FROM CATTLE

CÁCERES, MARÍA EMILIA; FERNÁNDEZ, DANIEL; SANZ, MARCELO, E; ETCHEVERRÍA, ANALÍA I.; PADOLA, NORA L.

Mar del Plata

Congreso; X Congreso de Microbiología General, SAMIGE; 2014

SAMIGE

.Shiga toxin-producing Escherichia coli (STEC) is an important cause of disease in humans such as haemorrhagic colitis (HC) and haemolytic-uremic syndrome (HUS), the leading cause of acute renal failure in children (Siegler, 2003). The most common STEC serotype asociated with sporadic cases and large outbreaks of diseases is E. coli O157:H7. However, other STEC serotypes, especially O26:H11/NM, O91:H21, O103:H2, O111:H8/NM, O113:H21, O104:H4, O145:NM, and O157:NM have been isolated from human disease (Paton et al. 1999; Center for Disease Control and Prevention 2007; Karama et al. 2008; Frank et al. 2011) Cattle are the main reservoir and can transmit STEC strains to human through contaminated food and direct contact.E. coli O157:H7 possess/has a putative virulence plasmid carrying genetic information for the enterohemorragichaemolysin -ehxA-(Schmidt et al. 1995b, 1996) and others virulence factors such as a periplasmic catalase-peroxidase -katP- (Brunder et al, 1996), an extracellular serine protease -espP- that is able to cleave pepsin and coagulation factor V in humans (Brunder et al, 1997); a zinc-metalloprotease -stcE-, (Grys TE. et al, 2005), and a subtilase-cytotoxin (subAB, which can produce an extensive microvascular damage, thrombosis, and necrosis in multiple organs, including the brain, kidneys, and liver (Paton & Paton, 2005).In this study, 255 enterohaemolysinpositive STEC strains (O157 and non-O157), isolated from different categories of cattle and different production systems (dairy farms and feedlot) in Buenos Aires province were analized by PCR for subtype the megaplasmid genes. The most prevalent detected gene was espP in 250/255 isolates (98,04%) followed by subAB 48,63% (124/255), katP 19,22% (49/255) and stcE in 5% (14/255).We found differences in the distribution of genes between the different categories of cattle, except for espP that was kept at a high prevalence. katP was found in similar percentages in newborn, weaning and rearing calves (38,89%, 31,37 and 33,33% respectively), but it showed a significative decrease in the adult group (6,06%). Moreover, the presence of subA showed a rising trend, with increasing age of the animals. So we found similar percentages of subA in newborn and weaning calves (11,11% and 15,69% respectively), 37,04% in rearing calves and the biggest percentage was found in the adult group (71,21%). stcE was the least prevalent gene of all, with an overall average of 5,49%.These results show the potential risk of the VTEC strains analyzed to generate infections in humans. It is also important to note the high percentage of espP-positive strains and the high levels found of subtilase-cytotoxin gene. That is relevant because many people work in direct contact with cattle so they are exposed to their feces and the environment where VTEC could be present, with the risk of developing a serious illness.