الفهرس 
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Abstract
The importance of studying S. aureus microbes was attributed to the
opportunistic nature of this bacterium, it also represent one of the most dangerous
bacteria that causes nosocomial infection, as well as the high capability of this
microorganism to acquire resistance against the different classes of antimicrobial
chemotherapeutic agents and disinfectants.
The current study was carried out to investigate MRSA phenotypically and
genotypically, detect the antimicrobial resistance in local MRSA isolates to
different classes of antimicrobial chemotherapeutic agents and disinfectants and to
detect types of integrons in these MDR isolates.
Two hundred specimens were collected from patients with various clinical
cases including burn, sputum, blood, peritoneal fluid, urine, ear discharge of otitis
media and diabetic foot lesions from Zagazig University Hospitals and burn unit of
El-Ahrar Educational Hospital in Sharkia, Zagazig, Egypt. In addition to collection
of 8 environmental isolates from the medium from which samples were collected.
The specimens were processed and yielded 117 non duplicate isolates that
were identified as S. aureus based mainly on Gram staining, colony morphology
on nutrient agar medium, fermentation on mannitol salt agar medium, β- hemolysis
on blood agar and being catalase and coagulase positive.
The susceptibility of S. aureus clinical and environmental isolates to different
members of antistaphylococcal drugs were determined by agar disk diffusion
method.
The isolates showed high sensitivity to vancomycin (100%), linezolid
(98.3%) and sulfamethoxazole- trimethoprim (90.59%). Meanwhile, these isolatesshowed high resistance to methicillin (100%), cefotaxime (76.07%) and
cefotriaxone (71.8%).
Out of 117 clinical and 8 environmental isolates, 72 and 6 were classified as
MDR, respectively, being resistant to 3 groups or more of antimicrobial
chemotherapeutic agents.
The susceptibility of MDR isolates to 7 selected groups of disinfectants and
antiseptics was tested by determination of the MIC by agar dilution method. The
MDR isolates showed high sensitivity to gluatraldhyde, cetrimide, chlorocresol and
chlorhexidine. However the same isolates showed low sensitivity to hydrogen
peroxide, povidone iodine and ethanol.
The MIC for gluatraldhyde ranged between 0.3 mg/ml and 1.6 mg/ml. The
MIC for cetrimide ranged between 0.002 mg/ml and 0.01 mg/ml. The MIC for
chlorocresol ranged between 0.1 mg/ml and 0.5 mg/ml. The MIC for each of
chlorhexidine (0.02 mg/ml and 0.06 mg/ml), hydrogen peroxide ( 0.03 mg/ml and
0.1 mg/ml) , ethanol ( 80 mg/ml and 200 mg/ml) and for povidone iodine (2 mg/ml
and 10 mg/ml).
The MDR of S. aureus clinical and environmental isolates were screened for
the prescence of two classes of integrons , and the prescence of qacE gene by PCR
technology.
The study showed that Integron І was the most predominant among the
MDR–MRSA isolates. It was detected using PCR technology and found in 48
(66.67%) of total 72 cllinical isolates; include 14 in gDNA and 34 in plasmid
DNA. It was detected by PCR technology and gel electrophoresis at bands matched
to 932 bp. Meanwhile, integron Ι was not detected in any of the environmental
isolates.