الفهرس 
COAGULASE NEGATIVESTAPHYLOCOCCIOnly 14 pages are availabe for public view
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Abstract
Coagulase negative Staphylococci have long been dismissed as culture contaminants. However, since the 1970s, CoNS have become increasingly recognized as important agents of nosocomial infection. Staphylococcus lugdunensis is a newly described species of coagulase-negative Staphylococci named for Lyon (Latin adjective of Lugdunum), the French city where the organism was first isolated. It was first described by Ferney and his colleagues in (1988). Staph.lugdunensis is a member of CoNS species but with notable clinical and microbiological characteristics that stand out among them. Staph.lugdunensis is frequently misidentified as Staph. aureus because of their morphologic appearance with yellow pigmentation and complete hemolysis when cultured on blood agar. Moreover, although Staph. lugdunensis does not possess secreted coagulase, some isolates produce a membrane-bound form of the enzyme (clumping factor) that yields a positive result in slide coagulase and/or rapid latex agglutination tests so it cannot be considered a“typical” CoNS species.
Similar to other CoNS strains, Staph. lugdunensis is considered part of the resident flora of the human skin and mucous membranes. The organism preferentially colonizes the perineal region and has been rarely found in the anterior nares or nasal cavities of healthy subjects.
Staphylococcus lugdunensis infections were mainly found to be associated with indwelling medical devices and immunesuppresion. Clinical manifestations of infections with this organism include mainly skin and soft tissue infections and abscesses. It can cause prosthetic and native valve endocarditis with poor prognosis resembling that of Staph.aureus catheter-related bacteremia, meningitis, endophthalmitis, prosthetic joint infection, ventriculo-peritoneal shunt infection and other foreign body related infections.
The aim of the present work was to determine the prevalence of Staph. lugdunensis among coagulase-negative Staphylococci isolated from different clinical samples, submitted to our microbiology laboratory, and to describe its antimicrobial susceptibility pattern.
In the present study, 227 CoNS isolates recovered from different clinical samples submitted to the Microbiology Laboratory for routine culture and susceptibility testing were analyzed for the presence of Staph. lugdunensis using the PYR and ODC tests.
The prevalence rate of Staph. lugdunensis among CoNS species isolated from the different clinical samples, was found to be 2.2% (5/227) since five isolates only gave positive reactions with the PYR and ODC tests.
Three out of the five identified Staph. lugdunensis isolates (60%) were recovered from blood cultures, one isolate (20%) was recovered from a urine culture and the last one (20%) was recovered from culture of a pus sample. The five isolates belonged to five different patients. All of the patients were immunocompromised and with indwelling medical devices.
In the present work, Staph. lugdunensis represented 3.3% (3/90) of CoNS causing bacteremia, 2.5% (1/40) of CoNS causing urinary tract infection, and 1.6% (1/61) of CoNS causing wound infection.
Using the API Staph identification kit (bioMérieux), only three isolates were identified as Staph. lugdunensis (3/5, 60%) whereas the remaining two isolates were identified as Staph. hemolyticus and Staph. lentus.
Using the MicroScan PBPC 20 panel, none of the five isolates were identified as Staph. lugdunensis. Four out of the five isolates (80%) were identified as Staph. hemolyticus and the remaining one (20%) was identified as Staph. auricularis.
Using the disk diffusion method, all of the five Staph. lugdunensis isolates were resistant to penicillin (100%) due to beta-lactamase production. Sixty percent of the isolates (3/5) were resistant to cefoxitin. The sensitivity to erythromycin, clindamycin, ciprofloxacin and sulfamethoxazole/trimethoprim was only 40%, respectively, whereas the sensitivity to tetracycline was 60% and the sensitivity to vancomycin was 100%.
Using the MicroScan PBPC 20 panel, all isolates were found to be beta-lactamase producers and oxacillin resistant (oxacillin breakpoint >2). Isolates were sensitive to vancomycin, synercid, linezolid, rifampicin, oxytetracycline. However, they were reported resistant to penicillins, cephalosporins, imipenem, gentamicin, trimethoprim/ sulfamethoxazole, and quinolones.
When the oxacillin resistant isolates identified by the MicroScan were tested for the presence of the PBP2a, only three isolates (60%) were positive. The same three isolates were cefoxitin (30μg) resistant by the disk diffusion method.