الفهرس 
The genus StaphylococcusOnly 14 pages are availabe for public view
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Abstract
Characterization of disease-causing bacteria helps in understanding the infection map it follow and make its dissemination criteria clearer, what make it easier to combat and prevent infection.
This study was conducted to characterize S. epidermidis isolates recovered from various biological samples phenotypically and genotypically and investigate the genetic relatedness between the isolates as well as investigating factors that may be related to its ability to cause disease. Also, the study aimed to compere between the clinical isolates recovered from various locations.
In this study a total of 256 S. epidermidis isolates were studied, where the 256 isolates are grouped into two main groups, the clinical isolates which recovered from clinical samples and the nasal isolates collected from right nasal nares of healthy volunteers (128 isolates in each group).
Antibiogram, methicillin resistance, biofilm producing ability, hemolysins production and ACME were investigated among the isolates where all except antibiogram were investigated phenotypically and genotypically, antibiogram was studied by disc diffusion method and the genetic relatedness was investigated by RAPD-PCR.
Results reflect clear significant differences in several parameters. Clinical isolates were significantly resistant for 8 out of the 12 tested antibiotic including the cefoxitin and significantly more in the number of antibiotics they resist as well as for the frequency of MDR. No differences in the distribution of mecA gene between the two groups, but significance seen in the ability to resist methicillin despite the presence of the mecA gene. Between isolates from different locations, ASH isolates were significantly resistant to clindamycin and in the relatedness between methicillin resistance and the presence of the mecA gene.
Also, clinical isolates were significantly more able to produce biofilm by the two phenotypic methods and were significantly higher in harboring icaA gene and no difference was recorded between the two groups in response to the aap gene. Between isolates from different locations, ASH isolates were significantly unable to produce biofilm on CRA comparing to the other isolates, and no differences were recorded in the distribution of the biofilm related genes between the isolates from different locations.
Significant difference between clinical and nasal isolates was recorded in response to its ability to produce hemolysins, where non hemolysins producers were significantly higher among nasal isolates and no significant differences recorded between the two groups in response to the frequencies of each toxin production except that seen among hla gene where clinical isolates were highly harboring the gene. Also, no significant differences were recorded in response to the patterns of hemolysin production. Both - and -toxins were significantly absence among isolates from APH and some significant differences seen between the production patterns. hla gene found to be harbored significantly more by the clinical isolates and hlb and hld gene significantly harbored by ASH isolates. Also, some differences seen between clinical and nasal isolates and between isolates from different locations in the hemolysins genes combinations.
Distribution of ACME related genes between clinical and nasal isolates and between isolates from different locations shows no significant differences. ACME III seen more among clinical isolates and some differences seen in the distribution of the ACME types among isolates from different locations.
RAPD-PCR reflects a clonal distancing between clinical and nasal isolates as well as a clonal distance between clinical isolates from different location where isolates from the north were closer together than they to the southern isolates. Also, genotyping reflects a limited number of clones circulate in each hospital indicating the possibility of nosocomial infections.
Methicillin resistance, biofilm production and hemolysins production were investigated by both, phenotypic and genotypic methods. No agreement seen between methicillin resistance detection methods, while in biofilm production methods, an agreement recorded between CRA and MtP methods, and when the phenotypic methods were compared to the genotypic methods, agreement seen between CRA method and PCR results, while it was absent with MtP method reflecting the specificity of the CRA method and the sensitivity of MtP method. For hemolysins, agreement seen between the phenotypic detection of the three toxins and the detection of the responsible gene by PCR