Clonal relatedness of methicillin-resistant coagulase-negative staphylococci in the haemodialysis unit of a single university centre in Greece

Background. Coagulase-negative staphylococci (CoNS) are frequently encountered pathogens in hospital environment. Dialysis patients, often carrying central venous catheters, are prone to CoNS infections. Methicillin-resistant (MR) staphylococci in hospitals are resistant to multiple antibiotics and may cause an overall increase in the incidence of staphylococcal infections rather than simply replacing the more susceptible strains. The aim of this study was to evaluate the antimicrobial resistance and the clonal relatedness of all clinically significant CoNS isolates recovered from haemodialysis patient infections treated in a tertiary care centre, the University Hospital of Larissa, in central Greece. In addition, the CoNS isolates from carriers among health-care workers of the local haemodialysis unit were tested. Methods. All staphylococci recovered from chronic haemodialysis patients who developed CoNS infections according to Herwaldt criteria in the University Hospital of Larissa, from October 2002 to October 2005, were included. In addition, isolates from the palms and the nasal mucosa of the nursing and medical personnel in the haemodialysis unit were also collected. Isolates were identified and tested for antimicrobial resistance by conventional microbiological methods. The clonal relationship of both patients' and carriers' isolates was tested by pulsed-field gel electrophoresis (PFGE) analysis. Results. Forty-two CoNS isolates were recovered from clinical culture specimens of patients hospitalized for various reasons. In 37 out of 42 CoNS isolates, methicillin resistance was determined. The majority of the MR Staphylococcus epidermidis isolates from patients belonged to one main clone (27 out of 32), arbitrarily named clone z. Clone z was also found to colonize 40% of the haemodialysis unit personnel. Conclusions. The high prevalence of clone z emphasizes the great capacity of CoNS to colonize patients with central venous catheters such as haemodialysis patients and personnel. This emphasizes the need for the establishment of control and prevention measures.