Abstract
The main objectives of the present study were to assess the incidence of E .coli O157:H7 serotype in both raw milk and locally produced soft cheese samples and to evaluate the efficacy of new immunomagnetic separation (IMS) technique for the first time in Iraq for isolation of the same serotype from such products compared to the conventional cultural method .A total of 50 raw milk and soft cheese samples (25 samples of each) were collected randomly at weekly intervals from different retail markets in Baghdad province and its surroundings during the period of six months (from October 2011 March 2012). Each sample was divided into two equal parts where the first part was analyzed for the conventional cultural method and the second part was analyzed for the immunomagnetic separation technique. Five isolates (20%) and seven (28%) were identified as E.coli O157:H7 from the same raw milk samples by both the conventional cultural method and (IMS) technique respectively. Two (8%) and four isolates (16%) were identified as E.coli O157:H7 the same soft cheese samples using the same above methods. The detection limits by the conventional cultural method were 4x103 cfu/ml and 7x102 cfu/gm of raw milk and soft cheese samples respectively, while the detection limits by the (IMS) technique were 1x102 cfu/ml and 12x10 cfu/gm of raw milk and soft cheese sample respectively .Results obtained in this study revealed that the IMS technique has been recognized to be significantly (P<0.05) more efficient in its sensitivity for the detection of low numbers of E.coli O157:H7 than the direct plating conventional method for both raw milk and soft cheese samples.
Highlights
Introduction that11 out of 24 (45.84%) of soft cheeseDairy cattle are known to be the most samples that were made from raw milk in important reservoirs of E.coli O157: H7and Baghdad province has Enterohaemorrhagic E.can potentially enter milk during milking coli O157: H7.A wide variety of methods are process through fecal contamination(1).Raw currently available to detect and isolate E. coli milk has long been recognized as a vehicle for O157: H7 and since such serotype is often the transmission variety of microbial found in low numbers in food,sensitive pathogens potential contamination enrichment culture methods are required for levels could be reduced by improving detection (7)
Can potentially enter milk during milking coli O157: H7.A wide variety of methods are process through fecal contamination(1).Raw currently available to detect and isolate E. coli milk has long been recognized as a vehicle for O157: H7 and since such serotype is often the transmission variety of microbial found in low numbers in food,sensitive pathogens potential contamination enrichment culture methods are required for levels could be reduced by improving detection (7)
Twelve grams portion from the surface and the core of each soft cheese sample (25 samples) were extracted aseptically and added to 99 ml of sterile pepton water versus aqueous 2% Sodium citrate (Dual purpose medium) enrichment medium which pre warmed to 40°C (10 and 11) and homogenized for 5 min in a stomacher.The homogenates were incubated at 37 °C for 24hrs, 1 ml of pre-enriched sample was added to 20 μl of anti-E. coliO157:H7 (Dynal) in 1.5 ml micro-centrifuge tube, and the tubes were incubated for 30 min at room temperature with constant mixing
Summary
Can potentially enter milk during milking coli O157: H7.A wide variety of methods are process through fecal contamination(1).Raw currently available to detect and isolate E. coli milk has long been recognized as a vehicle for O157: H7 and since such serotype is often the transmission variety of microbial found in low numbers in food ,sensitive pathogens potential contamination enrichment culture methods are required for levels could be reduced by improving detection (7) This enrichment step can be sanitation and hygiene during milking (2) followed by immunomagnatic separation.
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