الكشف عن جينات السموم المعوية وبعض العوامل المؤثرة على السموم المعوية لعزلات المكورات العنقودية الذهبية في مدينة كربلاء

Detection of Enterotoxin genes and some of Enterotoxin influencing factors of Staphylococcus aureus isolates in kerbala city

Nasal swab samples were collected from 332 food handlers working in Kerbala. The largest group of food handlers included in this study was the

servants in restaurants (n= 95). In addition, there were three additional large groups of food handlers: Chiefs (n=68), Bakery workers (n=66), and Water plant workers (n=59).

The samples were processed according to the standard microbiological procedure. Cultural characteristics, biochemical assays and API staph were used for phenotypic identification of the isolates. Polymerase chain reaction (PCR) targeting femA gene fragment was used for the molecular confirmation of the identification. A total of 100 Staphylococcus aureus isolates were recovered from the food handlers, representing a prevalence of 30.1%. Asignificantly high prevalence of nasal swab carriage of S.aureus were found among the workers of school foods shops (100%), cafes workers, (85.7%), and sweet shop workers (71%).

Multiplex PCR was used to study the prevalence of staphylococcal enterotoxins gene type a, b, c, d and e , the prevalence of enterotoxin genes were 38% among 100 isolates . 16 (16%) were positive for sea, 18(18 %) were positive for seb, 8(8%) were positive for sec and see, 6(6%) were positive for sed.

In addition, many strains were found to possess multiple enterotoxin genes. 27% positive for one gene, 6% Positive for two genes 4% positive for three genes, 1% positive for five genes. These results indicate that a significant numbers of food handlers carry enterotoxigenic strains and thus imposing a risk of transmitting those strain to food during food processing or preparing, packaging etc.

Therefore, a specific measure must be put in place in order to prevent food poisoning which would be the result of transmission of Staphylococcus aureus to food products.

To study the effect of culture conditions on the toxin production series of experiments were done , the experiments include three factors (salt,pH,glucose) . For this purpose, 2 strains were selected. The first one was a possessing multiple enterotoxin genes, whereas the second one did n’t have any of the studied enterotoxin genes.

High Nacl concentration (12%, 14%) were found to induce toxin production but reduce growth rate , whereas near-neutral pH was found to increase both growth rate and toxin production , and glucose concentration (2.5%) were found to induce toxin production but also reduce growth rate.

According to the results, the conditions that are not supportive for toxin productions include low (pH , glucose concentration and Nacl concentration).