الفهرس 
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Abstract
S.aureus has the ability to form biofilms, and causes significant mortality and morbidity in the patients with wounds. Our aim was to study the in vitro biofilm-forming ability of isolated S. aureus and its antibiotic sensitivity pattern.
One hundred clinical isolates of S. aureus were obtained from 350 pus samples using standard microbiological techniques. Antimicrobial susceptibility test was performed using the modified Kirby–Bauer disk diffusion method and confirmed by VITEK 2 automated microbiology system. S. aureus (MRSA) detection was also confirmed by detection of mec A gene by PCR.
Biofilm formation in these isolates was detected phenotypically by tissue culture plate (TCP) method and congo red agar (CRA) and genotypically by detection of ica ABCD genes by PCR.
S.aureus isolates were totally resistant to Penicillin G and highly resistant to Cefoxitin and Oxacillin. They were moderately resistant to Gentamycin, Tetracycline, Erythromycin, Clindamycin, Doxycycline and Chloramphenicol.
They showed low resistance to Ciprofloxacin, Levofloxacin Trimethoprim/ Sulfamethoxazole, Moxifloxacin and Azithromycin. All isolates were sensitive to Qunipristin/Dalfopristin, Linezolid, Vancomycin ,Tigecycline, Nitrofurantoin, Rifampicin and Teicoplanin. Among the 100 isolated S.aureus isolates, 89(89%) were identified as MRSA.
The clinical isolates of S. aureus recovered from infected wounds exhibit a high degree of biofilm formation .Biofilm formation was observed in (76 %), (74%) and (70%) isolates of S. aureus via TCP method CRA and genotypically, respectively.
Evaluation of risk factors associated with biofilm formation of S.aureus in infected wounds in the present study concluded that sex ,bed sores, previous hospital admission, using of broad spectrum antibiotics and presence of chronic diseases (other than DM) were important risk factors for biofilm formation by S.aureus in infected wounds .
S. aureus isolates were tested for detection of biofilm formation by congo red method , tissue culture method and PCR for detection of (ica A,B,C,D) genes. 70 isolates (70% ) were found to contain one or more of these genes and 30 isolates (30%) were negative for all genes. Ica A was present in 23% of isolates, Ica B was present in 11% of isolates, Ica C was present in 9% of isolates and Ica D was present in 70% of isolates. 89% of the S.aureus were MRSA and showed higher capacity to produce biofilm than MSSA.
Congo red and TCP methods, had statistically significant relation with the concomitant presence of ica A,B,C,D genes but TCP had higher sensitivity and specificity. CRA, although easier and faster to perform, still TCP remains a better tool for screening of biofilm formation.
On the other hand, the biofilm-forming ability of some strains in the absence of ica A,B,C,D genes highlights the importance of further genetic investigations of ica independent biofilm formation mechanisms.
The biofilm forming isolates have a higher tendency to exhibit antibiotic resistance compared to non biofilm forming strains. This may lead to the high risk of impairment in the wound healing and dissemination of the infection enhancing morbidity and mortality.