الفهرس | Only 14 pages are availabe for public view |
Abstract A total of 450 samples ( including 200 milk samples, 100 icecream and 100 kariesh cheese samples and 50 nasal swabs from human food handlers) were collected from different localities in Assiut governorate, Egypt. The samples were examined bacteriologically for the enumeration, isolation and identification of S. aureus, detection of protein profiles of staphylococcal enterotoxins by SDS-PAGE and detection of S. aureus enterotoxins genes (A, B, C, D, G and H) by PCR. Using Baird-Parker medium (directly without enrichement on broth), S. aureus could be detected in 44%, 80%, 60%, 54%, 50%, 30%, 80%, 60% and 80% of the examined samples of milk obtained directly from animals, dairy farms, dairy shops and street distributers, street vendors’ ice-cream and small scale producers’ ice-cream, street distributers’ kariesh cheese and grocery shops’ kariesh cheese and nasal swabs from human food handlers, respectively. The maximum counts in milk and dairy products were 2x105, 2.8x105, 2x104, 1.7x104, 4x103, 2x102, 5x105 and 2x105 cfu/ ml or gm, respectively. So, the highest percentage of S. aureus was observed in milk samples taken from dairy farms and in kariesh cheese from street distributers (80%) and the highest maximum count was observed in kariesh cheese from street distributers (5x 105 cfu/gm). After enrichement on Staphylococcus broth media, the percentages of S. aureus on Baird- Parker agar were 36%, 72%, 56%, 48%, 40%, 30%, 76%, 56% and 70 % , respectively, while on Mannitol salt agar the percentages of S. aureus were 40%, 70%, 56%, 50%, 26%, 22%, 58%, 44% and 80%, respectively. There was a significant difference between the percentage of S. aureus isolated on B-PA and MSA in ice-cream and cheese samples. After confirmation of suspected S. aureus isolates by coagulase test and latex agglutination test for clumping factor, protein A and capsular polysaccharides, CPS was detected in 220 out of 450 total examined samples (48.9%). It was detected in 100 out of 200 raw milk samples (50%), 35 out of 100 samples of ice-cream (35%), 65 out of 100 samples of kariesh cheese (65%) and 20 out of 50 nasal swabs from human handlers of milk and its products (40%). So, the highest percentage of CPS in different samples was observed in kariesh cheese. SDS-PAGE was used to detect the toxigenic isolates out of the 220 coagulase positive S. aureus isolates (200 CPS isolates from milk and dairy products+20 CPS isolates from human food handlers’ nasal swabs) . Out of the 200 CPS isolates from milk and its products, 99 isolates (49.5%) were toxigenic and out of the 20 nasal swabs, 10 isolates (50 %) were toxigenic. The percentage of enterotoxigenic isolates were 68.8%, 57.1%, 32%, 41.7%, 40.9%, 46.2%, 65.8%, 37% and 50% of the examined samples of milk obtained directly from animals, dairy farms, dairy shops and street distributers, street vendors’ ice-cream and small scale producers’ icecream, street distributers’ kariesh cheese and grocery shops’ kariesh cheese and nasal swabs from human food handlers, respectively. So, the highest percentages of toxigenic isolates were observed in milk samples taken directly from the animals (68.8%) and in kariesh cheese from street distributers (65.8%). PCR technique was applied to all toxigenic isolates ( 99 isolates from milk and dairy products and 10 isolates from nasal swabs). All of them were positive for one or more enterotoxin genes (A, B, C, D, G and H) In milk and dairy products, the major classical enterotoxin genotype was SEA which was detected in 29/99 isolates ( 29.3%) followed by SEC that was detected in 16/99 isolates (16.1%) and SED that was detected in 10/99 isolates (10.1%) . Enterotoxin B gene was not detected in any sample. For the newly described genes, SEG was detected in 10 isolates (10.1%) followed by SE H which was detected in 7 isolates (7.1%). The mixed forms were found in eight isolates (8.1%) for SE(A+C) genes another eight isolates (8.1%) for SE(A+C+D) genes , five isolates (5.04%) for SE (A+G+H) genes and two isolates only (2.02%) for SE(G+H) genes . In the 10 toxigenic isolates of nasal swabs, the major classical enterotoxin genotype was SEA that was detected in four isolates (40%) . SEC and SED were detected in one isolate (10%). However, SEB could not be detected. For the newly described genes one isolate (10%) showed SEG and another one showed SEH gene (10%). In the mixed forms, only one isolate (10%) showed SE(A+C) and another one showed SE ( A+G+H). The public health significance of the organism and the precautions, which should be taken to control this organism in dairy industry as well as the recommended sanitary measures, were also discussed |