الفهرس 
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Abstract
Staphyloccus aureus is one of the most common community and nosocomial pathogens and it mainly causes skin and soft tissue infections. The stains of S. aureus are always changing over the years, thus it becomes resistant to many drugs. Vancomycin has been the cornerstone of MRSA therapy for the past five decades, yet in the last 20 years it has exerted considerable selection pressure on S. aureus stains causing the emergence of vancomycin-resistant S. aureus (VRSA) stains. Increased VRSA stains has been reported all over the world during the last two decades.
In the current study we aimed to study the prevalence of VRSA strains in Zagazig University Hospitals, study their antibiotic susceptibility profile and suggest antibiotic combination therapy to control and present the transmission of VRSA strains among the health care settings.
Results obtained in this study can be summarized as follows :-
1- One hundred pus samples were collected from post operation wounds of a study group of inpatients in Zagazig University-Hospital. Bacteria colonizing the wounds were isolated on specific culture media thereafter purified and divided into 4 groups depending on their morphological characters and Grams stain reaction. Isolated bacteria were divided into 4 groups. Bacterial isolates related to the 4 groups were further on identified using conventional methods according to the key described in Bergeeys manual. group (I) represented 38% of total isolates; while group (II) & (III) represented 20% group (IV) 22%. Isolated bacteria related to groups I, II, III & IV were preliminary identified as S. aureus. E coli, K. pneumonia and P. aeruginosa, respectively.
2- Antibiotic susceptibility of the 4 groups of isolated bacteria against 15 different antibiotics revealed that imipenem and vancomycin are the most effective antibiotics against S.aureus groups with sensitivity 86.9% and 84.2%, respectively; meanwhile, Imipenem showed highest activity (100%)against E. coli and K. pneumonia 86.3% in case of P. aeruginosa.
3- Depending on antibiotic susceptibility pattern some strain were selected as multi-resistant isolates. Strains encoded S. aureus 6 & 16 were resistant to 11 antibiotics out of 15 (73.3%) and 10 antibiotics out of 15 (66.7%), respectively. The two mentioned strains are methicillin and vacomycin resistant, thus suspected as MRAS and VRSR strains. E. coli 5 resisted 13 antibiotics out of 15 (86.7%). K. pneumonia 22&81 showed multi resistance toward 66.7% of tested antibiotics (10 out of 15). Also P.aeruginosa 54 was recorded as a multi-resistant strain resistant to 86.7% of tested antibiotics and P.aeruginosa 39 showing 73-3% resistance including imipenem).
Conclusion
The control of emergence and spread of antimicrobial resistance among the most common human bacterial pathogens is probably one of the most important challenges for the scientific and medical communty. This emergence was significantly marked in hospitals that had been endemic with (MRSA) strains and followed the policy of empirical use of glycopeptides.
Vancomycin being the cornerstone of treatment of patient with serious MRSA infections for some decades has exerted considerable selection pressure on S. aureus strains in the healthcare setting.
Extensive use of glycopeptides (vacomycin or teicoplanin )allowed selection of resistant strains of . aureus that have been experimentally selected by gradually increasing the levels of vancomycin during in –vitro groth.