الفهرس 
ACKNOWLEDGEMENTSOnly 14 pages are availabe for public view
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Abstract
The study was conducted with 482 food of bovine origin samples, where 362 of them were of dairy sources (200 milk, 42 butter and 120 ice cream samples) and the rest 120 were of meat sources (90 different sources of minced meat and 30 ready to eat - shawerma samples). from apparently healthy food workers corresponding to the former collected samples, throat and finger nails samples (180 of each) were collected as well as throat and finger nails samples from ICU nosocomial patients (45 of each). All collected samples were subjected to S. aureus isolation and identification phenotypically, rather than searching for its carrying methicillin resistance and biofilm factors. The study concluded 99 (10.62%) S. aureus strains out of 932 samples of different sources all over the study. S. aureus from dairy sources showed 12.98% with highly significantdifference (P<0.001) than those from meat sources (6.66%). Moreover, S. auerus from apparently healthy showed highly significant difference (P<0.001) than those from nosocomial patients either from Finger nails (9.44%) or throat (13.33%) samples. About dairy samples, subclinical mastitic (farm) milk samples revealed 41.86 % infected showing highly significant difference (P<0.001) than other milk sources, however total milk samples showed 14.5%. Butter samples showed 16.66%, while total ice cream samples revealed only 9.2% S. aureus. Regarding to meat food samples, total investigation showed 8S. aureus (6.66%) positive strains, where shawerma and minced meat revealed (10 & 5.55% respectively. Concerning dairy workers; ice cream workers showed the highest prevalence of S. aureus carriage either from throat (20%) or finger nails samples (16.66%) than those isolated from milkers (7.50%) and (10%) or butter workers either from their throat (9.37%) or finger nails (3.12%)respectively. For meat workers or food handlers throat samples, 15.38% of them were S. aureus carriage; restaurant workers throat had the highest prevalence (24%) more than shawerma workers (13.04%) and butchers(10%), while for finger nails of food handlers showed 8.97% S. aureuscarriage; butchers had the highest prevalence (13.33%) more than restaurant(8%) and shawerma workers(4.34%). 57.9 % of S. aureus isolated from meat workers were biofilm production.All (100%) tested – antimicrobial resistance - dairy food S. aureus strains (no = 33) were methicillin resistant (MRSA), while only 83.3 % of the tested S. aureus strains from meat and its products (n = 8) were MRSA.
Apparently healthy food worker S. aureus carriage showed biofilm production as 37.5 & 58.8 % in both throat and finger nails respectively. For nosocomial patient samples (throat and finger nails, 45 of each) showed only three S. aureus strains originated from throat where two of them (66.6 %) were biofilmproduction. MRSA resembled 90.9 & 90 % of S. aureus isolated from throat and finger nails respectively.
Antimicrobial resistance study of 60 S. aureus strains revealed that 95 % were MRSA, where bovine sources resembled 97.4 %, (100 & 83.3 % for dairy and meat respectively) and human sources resembled 90.1 % (90.9 & 90% for throat and finger nails respectively). Multi antimicrobial resistance index (MAR)indicated that the overall mean was 0.44 ± 0.14, where meat and its products showed the highest index (0.61 ± 0.80).
Forty S. aureus strains resembling all studied categories were subjected to molecular investigation and PCR testing resulted 100, 67.5 and90.3 % for 16SrRNA, mec A and ica A respectively. Virulence genes mecA andicaA were detected in S. aureus strains from dairy sources as 68.42 & 73.68 %, where butter showed the highest percentage as 100 & 75 %, followed by ice cream strains (66.66 & 83.33 %) and raw milk strains (55.55 & 66.66 %). In dairy workers throat S. aureus strains, the referred virulence genes were determined as 50 & 100%, where ice cream workers showed 100 % for both genes. But those from their finger nails, mecA andicaA were achieved in 40 & 80 %, where milkers showed 100 & 100 % respectively. S. aureus strains from total meat samples,mecA and icaA were detected in 60 & 80 %, where inminced meat were 75 & 100 % respectively. About throat samples of meat workers, both genes were detected in 100 % of tested strains which were belonged to restaurant workers (food handlers). All tested S. aureus strains(no = 4) from finger nails of meat workers revealed 100 % for both virulence genes. For S.aureus strains isolated from throat pateints, mecA and icaAwere in the percentage of66.66&33.33 respectively.
Phylogenetic study and molecular characterization of mecA gene was done using seven S. aureus strains isolated from different studied sources ; human (Throat of restaurant worker, throat of a nosocomial patient and finger nail of an ice cream worker) and food (butter, ice cream, cow subclinical mastitic milk and minced meat samples). It was resulted that all strains appeared into two clusters, each of them showed 100% identity concluding that S. aureus is highly zoonotic pathogen transmitted from livestock animals or their products (dairy and meat) to human and vice versa.