Department of Medical Microbiology, Leiden University Medical Center, Leiden, The Netherlands
Sir,
Septicaemias caused by coagulase-negative staphylococci (CoNS), including Staphylococcus haemolyticus, are common in neutropenic patients. Since these bacteria are often resistant to both ß-lactam antibiotics and aminoglycosides, the empirical therapy of choice is a glycopeptide, either vancomycin or teicoplanin. Teicoplanin is less active in vitro against isolates of S. haemolyticus compared with other CoNS and there have been reports of treatment failures in neutropenic patients who had received the antibiotic for septicaemias caused by bacteria belonging to this species.1,2 In a recent study we compared the MICs of vancomycin and teicoplanin for 201 clinical isolates of CoNS recovered at the Leiden University Medical Center in 1985 and in 1994.3 In 1994 we identified eight isolates of S. haemolyticus, three of which exhibited intermediate susceptibility to teicoplanin (MICs 9, 9 and 10 mg/L, respectively) according to MIC breakpoints recommended by the National Committee for Clinical Laboratory Standards.4 The three isolates, all of which were susceptible to vancomycin, were recovered during a 1 month period from blood cultures obtained from three patients in the intensive care unit. All three patients suffered septicaemia according to CDC criteria.5 The remaining five isolates were recovered from patients in various other wards and were temporally unrelated.
In order to determine whether the three strains exhibiting intermediate susceptibility to teicoplanin were clonally related, DNA extracted from these bacteria was analysed by pulsed-field gel electrophoresis (PFGE) according to a method described previously.6 The Figure demonstrates the PFGE patterns for the eight S. haemolyticus isolates collected during 1994. The pattern of each of the five teicoplanin-susceptible isolates was unique, whereas those of the three intermediately susceptible isolates were indistinguishable, suggesting that the latter isolates belonged to a single clone.
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Notes
J Antimicrob Chemother 2000; 45: 410411
* Correspondence address. Laboratory for Clinical Microbiology, Medical Center Alkmaar, PO Box 501, 1800 AM Alkmaar, The Netherlands. Tel: +31-72-5483671; Fax: +31-72-5482186; E-mail: j.h.sloos{at}mca.alkmaar.nl
References
1 . Spanik, S., Trupl, J., Studena, M. & Krcmery, V. (1997). Breakthrough nosocomial bacteraemia due to teicoplanin-resistant Staphylococcus haemolyticus in five patients with acute leukaemia. Journal of Hospital Infection 35, 1559.[ISI][Medline]
2
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Cunningham, R., Gurnell, M., Bayston, R., Cockayne, A. & Shelton, A. (1997). Teicoplanin resistance in Staphylococcus haemolyticus, developing during treatment. Journal of Antimicrobial Chemotherapy 39, 4389.
3 . Sloos, J. H., van de Klundert, J. A. M., Dijkshoorn, L. & van Boven, C. P. A. (1998). Changing susceptibilities of coagulasenegative staphylococci to teicoplanin in a teaching hospital. Journal of Antimicrobial Chemotherapy 42, 78791.[Abstract]
4 . National Committee for Clinical Laboratory Standards. (1995). Performance Standards for Antimicrobial Susceptibility TestingSixth Informational Supplement: Approved Standard M100-S6. NCCLS, Wayne, PA.
5 . Garner, J. S., Jarvis, W. R., Emori, T. G., Horan, T. C. & Hughes, J. M. (1988). CDC definitions for nosocomial infections. American Journal of Infection Control 16, 12840.[ISI][Medline]
6 . Sloos, J. H., Horrevorts, A. M., van Boven, C. P. A. & Dijkshoorn, L. (1998). Identification of multiresistant Staphylococcus epidermidis in neonates of a secondary care hospital using pulsed field gel electrophoresis and quantitative antibiogram typing. Journal of Clinical Pathology 51, 627.[Abstract]