التوصيف الجزيئي للمكورات العنقودية الذهبية المعزولة من الحليب ومشتقاته

Molecular Characterization Of Staphylococcus aureus Isolated From Milk and Milk products

Summary
Staphylococcus aureus is a pathogenic bacterium-contaminating milk and milk products causing food poisoning primarily due to its enterotoxins Production, it possessed a repertoire of virulence factors, multiple antibiotic resistance and its capability to biofilm formation , in addition to its capacity to gain new resistance genes via integron, which could lead to difficult treatment. For these reasons, the aim of study to determine the prevalence rate ,accurant some virulence pattern and biofilm formation in S,aureus isolated from milk and milk product (mecA ,femA, Icaa and Icad) genes .
Study was conducted to collect a total of 300 samples divided into six groups 50 Samples for each (cow raw milk ,imported milk ,imported dairy products ,locally dairy products (factory) ,farm dairy product and buffalo raw milk),the study was beginning from October 2022 to February 2023. The samples were collected randomly from different locations in Karbala city .The samples were manipulated using bacteriological and biochemical methods for isolation and identification of S. aureus, then biofilm production and antimicrobial susceptibility tests were done. Molecular tools were used to study the prevalence some virulence genes (mecA,femA,Icaa and Icad) and the ability of S.aureus to produce β-lactamase enzyme was examined by rapid iodiometric method.
The result of our study revealed of 300 samples cultured and identified,121 (40,3%), isolates were characterized as S. aureus,it was distributed as cow raw milk 17 (34%),imported milk13 (26%),imported dairy products 18 (36%),locally dairy products (factory) 23 (46%),farm dairy products 30 (60%)and buffalo raw milk 20 (40%). Regarding resistance rates of S. aureus, the isolates were most frequently resistant to penicillin G 61 (50.77%) and oxacillin 49 (40.49%) but more susceptible to ciprofloxacin (100%) gentamycin(100%), Azythromycine 89 (73.66%), Erythromycin 77 (63.24%) ,Tetracycline 52 (42.9%) . Furthermore, the molecular prevalence and percentage of Methacillin resistance antibiotic depending on the detection of the mecA genes was 49 (40,49 %) and remaining 72 (59,50). the molecular prevalence of MRSA among different groups was recorded as, cow raw milk 7(41,17%),imported milk 6 (46,15%),imported dairy products 7 (38,88%),locally dairy products (factory) 9 (39,13%),farm dairy products 12 (40%) and buffalo raw milk 8 (40%) .
The rate of biofilm production in overall S. aureus was 100% this result was divided into three phases (strong, moderate and weak)formation the percentage of these phases among different milk and milk products was ,strong formation 74 (62,5%) moderate formation 28 (22,08%) and weak formation 19 (15,42%)
On the other hand the number and percentage of Icaa gene in all sample of S.aureus was 81 (67.86%) distributed among the study groups it as ; Cow raw milk 12 (70.59%), imported milk 10 (76.92%),imported dairy products.14 (77.87%) , Locally dairy products(factory) 15 (65,22%),farm dairy product 20 ( 66.67%)and buffalo raw milk 10 (50%) while the result was form Icad was 77 (64.24%) among the groups of milk and milk products; cow raw milk 11 (64.71%),imported milk 8 (61.54%),imported dairy products 15 (83.33%),locally dairy products (factory)14 (60.87%),farm dairy products18 (60%)and buffalo raw milk 11 (55%).
All Staphylococcus aureus have ability to produce the beta-lactamase enzyme by a rapid direct iodine method by useing starch-iodine complex and most of strain are strong biofilm formation