Antimicrobial resistance and pathogenicity of Escherichia coli isolated from common dairy products in the Lebanon I. SALEH * , O. ZOUHAIRI { , N. ALWAN { , A. HAWI 1 , E. BARBOUR " and S. HARAKEH { * Dubai International School, P.O. Box 15495, Dubai, United Arab Emirates { Biology Department, American University of Beirut, P.O. Box 11-0236, Beirut, Lebanon { Forschungsinstitut Senckenberg, Sektion Ichthyologie, Senckenberganlage 25, D-60325 Frankfurt am Main, Germany 1 Dubai Chamber of Commerce and Industry, P.O. Box 1457, Dubai, United Arab Emirates " Animal and Veterinary Sciences Department, American University of Beirut, P.O. Box 11-0236, Beirut, Lebanon Received 28 May 2008, Revised 25 September 2008, Accepted 29 September 2008 In a recent study, bacteria have been isolated from popular Lebanese dairy products, which had been collected in the Beqaa Valley, in north–eastern Lebanon. The foods investigated were two cheeses (shankleesh and baladi) and a dried fermented mixture of yogurt and wheat grains (kishk). Bacterial colonies on McConkey and sorbitol– McConkey agar that showed the morphology of Escherichia coli were biochemically tested and then classified, using PCR-based assays, into the various strains of pathogenic and non-pathogenic E. coli. Some of the confirmed E. coli isolates were proven to be pathogenic, including two identified as E. coli O157:H7. When the pathogenic isolates were tested for their susceptibility to 10 different antibiotics (all commonly used, by clinicians and veterinarians, for the treatment of infections with Gram-negative bacteria), each tested isolate was found to be highly resistant to at least one antibiotic. It therefore appears that, in Lebanon, some popular dairy products pose a public-health hazard, acting as vehicles for the transmission of drug-resistant pathogens. Each year, bacterial contamination causes millions of cases of food-borne illness world- wide (Prier and Solnick, 2000; Lamps, 2003). Milk and dairy products are highly susceptible to microbial contamination because their composition provides a favor- able medium for the growth of a wide variety of micro-organisms (De Buyser et al., 2001; Van Kessel et al., 2004). Virulent strains of Escherichia coli, which are usually classified into five main groups according to their molecular characteristics, are the most common cause of diarrhoeal infections and outbreaks (O’Ryan et al., 2005). Enterotoxigenic E. coli (ETEC) are characterised by the expression of genes coding for heat-stable and heat-labile enter- otoxins (Steinsland et al., 2003). The bacteria that carry the E. coli attachment and effacement gene eaeA are known as enteropathogenic E. coli or EPEC (Evans and Evans, 1996). Carriage of the gene (ipaH) coding for the invasion plasmid antigen, which enables the pathogens to invade epithelial cells, distinguishes entero- invasive E. coli (EIEC) from the other groups of E. coli (Matar et al., 2002). Among the pathogenic varieties of E. coli, only entero-aggregative E. coli (EAEC) carry a pAA plasmid. This plasmid codes for the aggregative adherence fimbrae that facilitate the pathogens’ adherence to intestinal mucosa (Wanke, 1995; Henderson et al., Reprint requests to: S. Harakeh. E-mail: sharakeh@gmail.com; fax: z961 5468476. Annals of Tropical Medicine & Parasitology, Vol. 103, No. 1, 39–52 (2009) # The Liverpool School of Tropical Medicine 2009 DOI: 10.1179/136485909X384965