ABSTRACT
CoNS and specifically, the dominant species Staph epidermidis have emerged in recent years as pathogens of serious nosocomial infections in neonatal intensive care. Methicillin resistant strains are particularly important because they show narrow therapeutic options. Detection of methicillin resistance among CoNS is often difficult, because these microorganisms present a hetero-resistant pattern. This work aimed to isolate the aerobic and facultative anaerobic organisms causing bacteremia in PICU of Ain Shams University hospital, assess the antibiotic-sensitivity for these organisms and to study the molecular detection of methicillin resistant "mecA" gene in CoNS in comparison with the phenotypic disk diffusion method. The study included 100 patients admitted to the PICU, from March 2003 to August 2003, for whom blood cultures were performed. Bacterial isolates including CoNS isolates were subjected to antibiotic sensitivity testing and PCR for detection of mecA gene. This study showed that 42% of patients had positive blood culture. Gram-positive organisms accounted for 47.7% of cases of which 42.9% were CoNS. Gram-negative organisms represented 38.1% and Candida spp accounted for 14.2%. The antibiotic sensitivity for CoNS isolates ranged from 22.2% [for both oxacillin and methicillin] to 66.7% [ampicillin + sulbactam]. Out of the 18 CoNS isolates, 11 isolates were mecA positive while the rest 7 isolates were mecA negative. Comparing the PCR with disk diffusion results showed that from 11 mecA positive isolates, 9 isolates were detected by disk diffusion as methicillin resistant [MR] and this include only Staph. epidermidis isolates. The other two mecA positive isolates were found to be methicillin sensitive [MS] by disk diffusion. From the 7 mecA negative isolates, 2 isolates were MS by disk diffusion. CoNS were the main blood stream infection [BSI] pathogen in Ain Shams University hospital PICU. MRCoNS were resistant to many antibiotics used. Disk diffusion test was significantly correlated with the PCR in case of Staph epidermidis but PCR was more rapid method for detection of MRCoNS