المستخلص:
The study aimed to investigating the role of coagulase - negative staphylococci in human infections, and determining the predominance genes of the virulence factors. Three hundred clinical specimens were collected from out and inpatients undergoing catheter related infections and twenty specimens were collected from healthy hospital staff as a control from January 2013 to July 2013 of Al - Zahraa Teaching Hospital, Al - Sader Teaching Hospital and Al - Hakeem Hospital in Al - Najaf Al - Ashraf province. The specimens were included urine, blood, vaginal swabs, seminal fluid and wound swabs. The specimens were cultured on mannitol salt agar and the primary identification was depended on Gram stained and biochemical tests. Then finally identification with Vitek 2 system is done.One hundred isolates were identified as coagulase - negative staphylococci (CoNS), Staphylococcus haemolyticus was identified as the most frequently isolated species in (53%), followed by Staphylococcus epidermidis (26%) and Staphylococcus hominis were recorded in (21%). Most of CoNS isolates were highly resistance to penicillin G (benzylpenicillin), oxacillin, cefoxitin and erythromycin; and low resistance to rifampicin, levofloxacin and others. While, control isolates results showed moderate resistance to penicillin G and erythromycin; low - level of resistance to cefoxitin, oxacillin and other antibiotics.The investigation of virulence factors revealed that 93% of coagulase - negative staphylococci isolates were production of slime layer, DNase 58%, protease 29% and hemolysin 88%. But the results gave negative result for TNase and lipase enzymes.Monoplex and multiplex PCR were used to explore the MecA, aap, icaA, icaD, atlE, sea, seb, sec, sed, hla, hlb, sspA, sspB, geh, nuc genes. The results showed that all CoNS isolates (100%) had mecA and atlEgenes, but 98% of isolates had aap, 93% icaA and icaD genes. PCR revealed that only (14%) of isolates had genes for enterotoxins expression. (92.86%) and (7.14%), sea and seb respectively, in contrast, the sec and sed genes were not be recorded.The result showed that 47% of CoNS isolates had hla gene and 41% contain hlb gene, 29% were positive for the sspA gene whereas the sspB gene and geh and nuc2 genes not found in any of staphylococcal isolates. Finally, the result indicated that 58% of CoNS isolates were expressed the nuc1 gene.Plasmid curing was carried out in order to determine the origin of resistance and some virulence factor genes (chromosomal or plasmid - borne gene). The curing (elimination) of the plasmids of coagulase - negative staphylococci isolated was catalyzed using ethidium bromide in different concentration and high temperature (44?C). The results showed that the oxacillin resistant coagulase - negative staphylococci were plasmid mediated since 93% of the isolates showed negative result on oxacillin resistance screening agar, and absence of mecA gene from all isolates. Also, 41 of coagulase - negative staphylococci isolates that showed ? - hemolysin became non - hemolysin after manipulated with ethidium bromide.Finelly, taking into consideration the etiological importance of CoNS has often been neglected, the present investigation confirmed that these microorganisms should not be ignored or classified as mere contaminant.
اسم المشرف:
عباس شاكر جواد المحنة
اسم المؤلف:
سعاد عبد الهادي عبد الرزاق الحلو
