Identification and antimicrobial susceptibility of Staphylococcus from home-treated peritoneal dialysis patients

Staphylococcus aureus is the main agent of infections during peritoneal dialysis (PD). The presence of S. aureus in the nasal cavity has been extensively studied and suggested as a risk factor of dialysis-related infections, whereas coagulase-negative Staphylococcus (CNS) species are frequently considered part of the normal human microbiota. The aim of this study was to identify Staphylococcus in the nasal cavity, pericatheter skin and peritoneal effluent from PD patients, as well as to evaluate the antimicrobial activity evolution in vitro. Thirty-two chronic PD patients were observed during 12 months and had nasal and pericatheter skin samples collected for culture. When peritonitis was detected, samples were also collected from the peritoneal effluent for culture. The activity of several antimicrobial drugs (penicillin G, oxacillin, cephalothin, ofloxacin, netilmicin and vancomycin) against different Staphylococcus species was measured by using the agar drug diffusion assay (Kirby-Bauer method). Staphylococcus was separated into S. aureus, S. epidermidis and other CNS species in order to determine the in vitro resistance level. S. epidermidis resistance to oxacillin progressively increased during the study period (p < 0.05). Resistance to ofloxacin was inexpressive, whereas resistance to netilmicin and vancomycin was not detected. Of the oxacillin-resistant species (n = 74), 83 percent were S. epidermidis, 13 percent other CNS and 4 percent S. aureus (p < 0.05). Regarding multi-drug resistant strains (n = 45), 82 percent were S. epidermidis, 13 percent other CNS, and 5 percent S. aureus (p < 0.05). This study shows the relevance of resistance to oxacillin and CNS multi-drug resistance, particularly concerning S. epidermidis, in PD patients.

Nosocomial Infections Caused by Coagulase Negative Staphylococcus and Drug-resistance / 中华医院感染学杂志

OBJECTIVE To study drug-resistance status of nosocomial infections caused by coagulase negative staphylococcus(CNS)to offer scientific basis for reasonable usage of antibiotics.METHODS CNS were all identified by VITEK32 system.The drug suspectivity was tested by K-B method.The results were judged according to NCCLS/CLSI2004.RESULTS Among 258 strains of CNS,111 strains of Staphylococcus haemolyticus ranked the top,accounting for 43.0% and followed by 98 strains of S.epidermidis(38.0%).The isolating rate of meticillin-resistant coagulase-negative staphylococcus(MRCNS)was 51.9%(134/258).The drug-resistance rate of MRCNS was higher obviously than that of methicillin-susceptible coagulase-negative staphylococcus(MSCNS).CONCLUSIONS CNS has been one of the important pathogens of nosocomial infections.MRCNS with higher isolating rate showed multi-drug resistance.The glycopeptide antibiotics are the first choice to cure MRCNS infections.