Survival in acidic and alcoholic medium of Shiga toxin-producing <it>Escherichia coli </it>O157:H7 and non-O157:H7 isolated in Argentina

• Main Authors: Sanz Marcelo E, Parma Alberto E, Molina Pablo M
• Format: Article
• Language: English
• Published: BMC 2003-08-01
• Series: BMC Microbiology
• Subjects: STEC; <it>E. coli </it>O157:H7; <it>E. coli </it>O91:H21; acid stress; ethanol; HUS; food
• Online Access: http://www.biomedcentral.com/1471-2180/3/17

<p>Abstract</p> <p>Background</p> <p>In spite of Argentina having one of the highest frequencies of haemolytic uraemic syndrome (HUS), the incidence of <it>Escherichia coli </it>O157:H7 is low in comparison to rates registered in the US. Isolation of several non-O157 shiga toxin-producing <it>Escherichia coli </it>(STEC) strains from cattle and foods suggests that <it>E. coli </it>O157:H7 is an uncommon serotype in Argentina. The present study was undertaken to compare the survival rates of selected non-O157 STEC strains under acidic and alcoholic stress conditions, using an <it>E. coli </it>O157:H7 strain as reference.</p> <p>Results</p> <p>Growth at 37°C of <it>E. coli </it>O26:H11, O88:H21, O91:H21, O111:H^-, O113:H21, O116:H21, O117:H7, O157:H7, O171:H2 and OX3:H21, was found to occur at pH higher than 4.0. When the strains were challenged to acid tolerance at pH as low as 2.5, viability extended beyond 8 h, but none of the bacteria, except <it>E. coli </it>O91:H21, could survive longer than 24 h, the autochthonous <it>E. coli </it>O91:H21 being the more resistant serotype. No survival was found after 24 h in Luria Bertani broth supplemented with 12% ethanol, but all these serotypes were shown to be very resistant to 6% ethanol. <it>E. coli </it>O91:H21 showed the highest resistance among serotypes tested.</p> <p>Conclusions</p> <p>This information is relevant in food industry, which strongly relies on the acid or alcoholic conditions to inactivate pathogens. This study revealed that stress resistance of some STEC serotypes isolated in Argentina is higher than that for <it>E. coli </it>O157:H7.</p>