الفهرس 
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Abstract
Abstract
One objective of this study was to provide a thorough understanding of the sanitary status and safety of 40 raw milk and 40 kareish cheese samples collected from Menofia governorate by isolating Enterobacteriaceae, E. coli, and Shigella spp. using antibiotic- free media. Surprisingly, all samples of raw milk and kareish cheese were contaminated with Enterobacteriaceae, and E. coli was isolated from 10 raw milk and 36 kareish cheese samples. It’s worth noting that none of the samples tested positive for Shigella spp. Another food safety issue is the emergence of antimicrobial resistance as a result of overuse and misuse of antibiotics such as ceftiofur in food-producing animals, constituting a global public health threat. Therefore, in lack of information on the occurrence of ceftiofur-resistant Enterobacteriaceae isolates from food, the second important goal of this study was to assess the prevalence, population structure, and antibiotic resistance patterns of ceftiofur resistant Enterobacteriaceae and E. coli in raw milk and kareish cheese samples by introducing ceftiofur into the isolation media. Ceftiofur resistant Enterobacteriaceae were detected in 90% of raw milk and 95% of kareish cheese samples. The most frequently isolated members of Enterobacteriaceae from raw milk were Citrobacter youngae, Klebsiella pneumoniae, and Enterobacter gergoviae, while Citrobacter braakii, Klebsiella pneumoniae, and Citrobacter amalonaticus were the most frequently isolated members from kareish cheese. Antimicrobial susceptibility testing showed that Enterobacteriaceae strains isolated
from raw milk samples exhibited high resistance rates to ceftiofur, cefepime, cefotaxime, and ceftriaxone. On the other hand, Enterobacteriaceae strains isolated from kareish cheese samples exhibited high resistance rates to ceftiofur, cefepime, ceftriaxone, cefotaxime, oxytetracycline, and ciprofloxacin. Interestingly, no resistance was observed to meropenem and colistin among all Enterobacteriaceae strains isolated from kareish cheese samples. A total of eighteen ceftiofur-resistant E. coli isolates were obtained, all of which were from kareish cheese samples. The MIC values of ceftiofur- resistant E. coli for cefotaxime, ceftriaxone, ceftiofur, and cefepime were ≤128 µg/ml. Most of the E. coli isolates showed MIC values for ciprofloxacin in the range of 0.25-
0.5 µg/ml. Molecular analysis of all 18 ceftiofur-resistant E. coli revealed that the most prevalent ESBL-associated gene was blaCTX-M, followed by blaTEM and blaCMY. qnrS gene was present in 38.89% of the ceftiofur-resistant E. coli isolates. In conclusion, the high incidence of Enterobacteriaceae and E. coli in analyzed raw milk and kariesh cheese samples indicated that these products were prepared under unsanitary conditions and were likely subjected to fecal contamination. This study also revealed that raw milk and kariesh cheese may serve as potential reservoirs for the transmission of ceftiofur- resistant Enterobacteriaceae and E. coli to humans. It is critical to monitor the frequency of ceftiofur-resistant bacteria in food items and modify the legislation controlling the use of ceftiofur in food animals.
Keywords:
Enterobacteriaceae, E. coli, antimicrobial resistance, raw milk, kareish cheese, ceftiofur, Egypt.