ملخص
Abstract
: This study was carried out to detect different coliforms members with special reference to the occurrence of the pathogenic Escherichia coli existing in raw cow`s milk and some dairy products. 105 samples (35 raw milk, 35 fermented milk, and 35 ricotta cheeses) were randomly collected from different markets in Tripoli-city /Libya. In this study, two methods for coliform counting were used. The first one was the most probable number technique MPN using liquid Lauryl Sulphate Tryptone broth (LST) with a three-tube series and the second method was the plate count method using violet red bile lactose agar VRBA. Also different techniques were used to find comparative results by using the BD phoenix system, the VITEK® 2 Compact system and KB003Hi25™ Enterobacteriaceae Identification Kit methods for coliform counts in raw milk, fermented milk and ricotta chesses. The coliform bacteria were positive in all 35 (100%) samples of both raw milk and fermented milk, while 33 (94.3%) samples out of 35of ricotta cheese by using MPN-technique. Whereas, Coliform bacteria were positive in 25 (71.4%) samples of raw milk, 34 (97.1%) samples of fermented milk and in 22 (62.9%) samples of ricotta cheese by using VRBA-technique. However, the fecal Coliform bacteria were recorded in 30 (85.7%) samples of raw milk, 32 (91.4%) samples of fermented milk and in 24 (68.6%) samples of ricotta by the used MPN-technique. Whereas, fecal Coliform bacteria were detected in 11 (31.4%) samples of raw milk, 19 (54.3%) samples of fermented milk and in only 9 (25.7%) samples of ricotta cheese by the VRBA-technique. Moreover, the most commonly identified important pathogenic bacteria Gram-negative isolated the highest overall incidence rate was for Escherichia coli 117(58.5%) and Klebsiella pneumonia spp pneumonia 47(23.5%) out of 200 randomly selected from 900 isolates. These findings results revealed that a high number of bacteria, which provide an evidence for the lack of milk hygiene either during milking or transporting and storages Statistical analyses revealed significant T-test at level P<0.05 as well as with a higher correlation (r=0.713, and r=0.617, p<001) was observed in coliforms and fecal coliforms counts by using both MPN-technique and VRBA-technique in raw milk. And with a higher correlation of (r=0.593, p<0.001) was observed in the coliform counts of fermented milk by using MPN-technique. As well as a higher correlation (r =0.728, p<0.001) was observed in coliforms counts in ricotta cheese.Furthermore a lower correlation(r=0.276, r=0.186, P<0.001) was observed in fecal coliforms counts in fermented milk and ricotta cheese by using both techniques. Therefore, this observationof significant or non significant T-test and higher or lower correlation cofficients may suggest and explain that both techniques were more or less have equivalent. From the Comparative analysis between the BD phoenix system, the VITEK® 2 Compact system and KB003 Hi25™ Enterobacteriaceae Identification Kit of10 isolates. There was a slight difference between the results from both the BD phoenix system and the VITEK® 2 Compact system in two isolates(20%), While the results of the VITEK® 2 Compact system were similar to the results of KB003 Hi25™ Enterobacteriaceae Identification Kit in 10 isolates(100%). Keywords: BD Phoenix system, VITEK® 2 Compact system, KB003Hi25™, coliforms bacteria, fecal Coliform bacteria, MPN-technique, Plate count.