JAC Advance Access originally published online on July 19, 2006
Journal of Antimicrobial Chemotherapy 2006 58(4):898-899; doi:10.1093/jac/dkl271
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Correspondence |
Linezolid resistance in coagulase-negative staphylococci1
1 Department of Clinical Microbiology, The Adelaide and Meath Hospitals, Dublin incorporating the National Children's Hospital Tallaght, Dublin 24, Ireland 2 Department of Clinical Microbiology, Trinity College, University of Dublin Dublin, Ireland 3 Department of Infection Control, The Adelaide and Meath Hospitals, Dublin incorporating the National Children's Hospital Tallaght, Dublin 24, Ireland 4 Department of Pharmacy, The Adelaide and Meath Hospitals, Dublin incorporating the National Children's Hospital Tallaght, Dublin 24, Ireland
*Corresponding author. Tel: +353-1414-3919; Fax: +353-1414-3352; E-mail: philip.murphy{at}amnch.ie
Keywords: oxazolidinones , ITU , Gram-positive bacteria
Sir,
We feel it is time to comment on the recent report from Jones et al.1 of minimal resistance to linezolid among an international and broad range of Gram-positive pathogens (n = 4098) and zero resistance among coagulase-negative staphylococci (n = 652). The previous SENTRY2,3 study of Gram-positive bacteria (n 
40 000) reported a single linezolid-resistant isolate of Staphylococcus epidermidis from the USA only.
In our hospital between September and December 2005 we identified three separate patient blood culture isolates of S. epidermidis for which MICs of linezolid determined by Etests were 16 mg/L (two isolates) and >32 mg/L. As there are some reports4 of false resistance detected in strains referred to reference laboratories, we referred our isolates to the UK Reference Laboratory (Centre for Infections, Health Protection Agency, UK), who confirmed MICs of >4 mg/L using an agar dilution method.5
Two patients had complicated clinical courses involving admission to ITU, insertion of central venous catheters and prolonged courses of linezolid. One patient (Patient 1) had received linezolid for an MRSA bloodstream infection. The second patient (Patient 2) had received linezolid for a VRE bloodstream infection. This patient had also undergone haemodialysis. However, of note was one isolate from a patient (Patient 3) who had never been exposed to linezolid but had overlapped for 12 days on the same ward as one of the other patients, although the other patient had been nursed in isolation suggesting possible cross-infection despite isolation. The three patients in our unit were co-infected with linezolid-susceptible coagulase-negative staphylococci in blood cultures and two of them with linezolid-susceptible Staphylococcus aureus in blood cultures (Patients 1 and 2) and one with linezolid-susceptible Enterococcus faecium in blood cultures (Patient 2).
We have reviewed our local linezolid usage data which show a small (13%) increase in linezolid usage in our hospital in 2004 but a 67% increase in 2005 corresponding to this emergence of resistance. Our hospital policy restricts linezolid use to approval by senior clinical microbiology staff and we hope that infection control and further restricted linezolid use will limit the further development of this new problem. Further resistance characterization and clonal analysis are ongoing but the implication for both the emergence and spread of resistance is of note, certainly within this institution if not this part of the world.
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Conflict of interest: none.
Acknowledgements
J. C. received a grant from the Cystic Fibrosis Association of Ireland and P. G. M. received a grant in 2003 from Pharmacia for a study proposal of linezolid use in cystic fibrosis.
References
1
Jones RN, Ross JE, Fritsche TR, et al. (2006) Oxazolidinone susceptibility patterns in 2004: report from the Zyvox Annual Appraisal of Potency and Spectrum (ZAAPS) Program assessing isolates from 16 nations. J Antimicrob Chemother 57:279–87.
2
Mutnick AH, Enne V, Jones RN. (2003) Linezolid resistance since 2001: SENTRY Antimicrobial Surveillance Program. Ann Pharmacother 37:769–74.
3 Ross JE, Anderegg TR, Sader HS, et al. (2005) Trends in linezolid susceptibility patterns in 2002: report from the worldwide Zyvox Annual Appraisal of Potency and Spectrum Program. Diagn Microbiol Infect Dis 52:53–8.[CrossRef][Web of Science][Medline]
4
Bell JM, Turnidge JD, Ballow CH, et al. (2003) Multicentre evaluation of the in vitro activity of linezolid in the Western Pacific. J Antimicrob Chemother 51:339–45.
5 Andrews JM. (2001) Determination of minimum inhibitory concentrations. J Antimicrob Chemother 48:Suppl 1, 5–16.[Abstract]
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