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Open Access Highly Accessed Research article

Characterization of coagulase-negative staphylococcal isolates from blood with reduced susceptibility to glycopeptides and therapeutic options

Silvia Natoli15*, Carla Fontana2, Marco Favaro2, Alberto Bergamini3, Gian Piero Testore3, Silvia Minelli2, Maria Cristina Bossa2, Mauro Casapulla1, Giorgia Broglio1, Angela Beltrame3, Laura Cudillo4, Raffaella Cerretti4 and Francesca Leonardis1

Author Affiliations

1 Intensive Care Unit, Department of Surgery, "Tor Vergata" University of Rome, Via Montpellier 1, 00133 Rome, Italy

2 Clinical Microbiology Laboratories, Polyclinic of Tor Vergata, Viale Oxford 81, 00133 Rome, Italy

3 Infectious Diseases, Department of Public Health, "Tor Vergata" University of Rome, Via Montpellier 1, 00133 Rome, Italy

4 Haematology, Department of Biopathology, Polyclinic of Tor Vergata, Viale Oxford 81, 00133 Rome, Italy

5 Dipartimento delle Emergenze e di Accettazione, di Medicina Critica del Dolore e delle Scienze Anestesiologiche -UOSD Terapia Intensiva, Policlinico Tor Vergata, Vale Oxford 81, 00133 Roma, Italy

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BMC Infectious Diseases 2009, 9:83  doi:10.1186/1471-2334-9-83

Published: 4 June 2009

Abstract

Background

Coagulase-negative staphylococci (CoNS) are a major cause of nosocomial blood stream infection, especially in critically ill and haematology patients. CoNS are usually multidrug-resistant and glycopeptide antibiotics have been to date considered the drugs of choice for treatment. The aim of this study was to characterize CoNS with reduced susceptibility to glycopeptides causing blood stream infection (BSI) in critically ill and haematology patients at the University Hospital Tor Vergata, Rome, Italy, in 2007.

Methods

Hospital microbiology records for transplant haematology and ICU were reviewed to identify CoNS with elevated MICs for glycopeptides, and isolates were matched to clinical records to determine whether the isolates caused a BSI. The isolates were tested for susceptibility to new drugs daptomicin and tigecycline and the genetic relationship was assessed using f-AFLP.

Results

Of a total of 17,418 blood cultures, 1,609 were positive for CoNS and of these, 87 (5.4%) displayed reduced susceptibility to glycopeptides. Clinical review revealed that in 13 cases (7 in haematology and 6 in ICU), CoNS with reduced susceptibility to glycopeptides were responsible for a BSI. Staphylococcus epidermidis was the causative organism in 11 instances and Staphylococcus haemolyticus in 2. The incidence of oxacillin resistance was high (77%), although all isolates remained susceptible to linezolid, daptomycin and tigecycline. Fingerprinting of CoNS identified one clonal relationship between two isolates.

Conclusion

Multi-resistant CoNS with reduced susceptibility to glycopeptides, although still relatively infrequent in our hospital, are emerging pathogens of clinical concern. Surveillance by antibiotyping with attention to multi-resistant profile, and warning to clinicians, is necessary.