Enterohemorrhagic Escherichia coli O157 in Libya

We have read with interest the Letter to the Editor by Ahmed and Abouzeed reporting on the important issue of enterohemorrhagic Escherichia coli O157 (EHEC O157) in dairy cattle in Libya (1). Based on two cited references, the authors state that: “Surveys of diarrheal stools from children in African nations, including Libya, have detected EHEC O157 in 8–15% of the samples”. One of the cited studies is not related to Africa, and the other, on the characterization of diarrheagenic E. coli from diarrheic Libyan children, clearly stated that EHEC was not detected in the stool specimens examined. However, a study from Tunisia examined 212 stool samples from diarrheic and non-diarrheic children and adults for EHEC using PCR-based techniques (2). They observed 11 isolates (10 non-typeable, one O157:H7) carrying the stx gene coding for EHEC. Another study, also from Tunisia, found EHEC in 10.4% of diarrheagenic and 11.1% of asymptomatic children (3). In the 1990s we examined stool specimens from 157 children with diarrhea and 157 controls for O157:H7 (4). Sorbitol non-fermenting E. coli isolates were subjected to agglutination with E. coli O157:H7 antiserum. In the specimens examined, E. coli O157:H7 was found in 7.0% and 4.4% of diarrheic and control children, respectively. Although cattle and their products are the main source of E. coli O157, asymptomatic carriers may play a role in the spread of this organism in the community. In addition, serotyping assays with specific antiserum may not be reliable for identification of E. coli O157:H7 strains (5). Rapid and reliable PCR-based methods designed to detect toxin-encoding genes for identification of EHEC O157:H7 and non-E. coli O157 are available. These methods should be used to provide reliable data on the role of EHEC O157 and non-O157 in causation of foodborne outbreaks and associated hemolytic uremic syndrome in the community and to determine the sources of such outbreaks.