Background: Coagulase-negative staphylococci (CoNS) represent one of the major resistant nosocomial pathogens where its biofilmrelated infections often fail to respond to antibiotic chemotherapy. Here, we studied the resistance profiles and biofilm formation in CoNS isolates from clinical specimens at Al Shifa hospital in Gaza, Palestine.
Methods:This study was carried out from March to July 2013 and included 81 clinical isolates. Identification and antibiotic susceptibility testing were performed using VITEK-2 system. The presence of nuc and mecA genes was performed using multiplex PCR. Qualitative and quantitative biofilm assays were performed using standard methods.
Results:Of the 81 clinical CoNS isolates, S. haemolyticus was the most common species (34, 42%), followed by S. epidermidis (26, 32.1%) and S. saprophyticus (13, 16%). The majority of isolates (83.9%) were from surgery, ICUs, pediatrics and medicine wards and the most common source was pus (28, 34.6%). Antibiotic resistance was highest against aminoglycosides, β-lactams, carbapenems, cephalosporins, fluoroquinolones, fosfomycin and macrolides. Though, no resistance was detected against rifampicin, vancomycin, teicoplanin, nitrofurantoin, linezolid and mupirocin. The antibiotic resistance among MR-CoNS was significantly higher than that among MS-CoNS. Nearly 88.9% of isolates were multidrug resistant with higher percentage among MRCoNS. Most S. epidermidis (76.9%) isolates were biofilm producer, with statistically significant association between methicillin resistance and biofilm production.
IntroductionCoagulase-negative staphylococci (CoNS) are now representing one of the major nosocomial pathogens and among the most frequently isolated bacteria in the clinical microbiology laboratories [1][2][3][4][5]. They are responsible for bacteremia, endocarditis, mediastinitis, meningitis and progressive joint destruction mainly in patients with neutropenia, indwelling foreign devices, intravascular catheters or other foreign bodies [1,3,4]. The clinical most relevant CoNS are Staphylococcus epidermidis, S. lugdunensis, S. saprophyticus , and S. capitis [6,7].Biofilm production by CoNS, specially S. epidermidis , is considered as an important factor in the pathogenesis of implanted medical devices associated infections [1,2,8,9]. Biofilm formation takes place in four successive phases: the attachment of the bacteria to biotic or abiotic surface; the proliferation and accumulation of bacteria in multilayered cell clusters; the growth of biofilm into a thick and structured layer, and finally the detachment and circulation of single cells or cell agglomerates via the bloodstream [1,2].Many literature surveys revealed that CoNS showed high resistance against most of the commonly used therapeutic antibacterial agents including methicillin. Irrespective of geographical locations, a worldwide SENTRY study showed that, about 70-75% of CoNS are resistant to methicillin [10]. There is a significant increase in the methicillin-resistant coagulase negative st...
