Journal of Antimicrobial Chemotherapy (2002) 49, 215-217
© 2002 The British Society for Antimicrobial Chemotherapy
Correspondence |
First characterization of vancomycin-resistant enterococci from a Portuguese hospital
a Laboratory of Microbiology, Pharmacy School, Porto University, Porto; b Laboratory of Microbiology, Coimbra University Hospital, Coimbra, Portugal; c Department of Microbiology, Ramón y Cajal Hospital, Madrid, Spain
Sir,
Enterococci have been recognized as one of the leading causes of nosocomial infections, including urinary tract and bloodstream infections. One of the major reasons why these organisms survive in the hospital environment is their intrinsic resistance to several commonly used antibiotics and their ability to acquire resistance to most available antimicrobial agents. Resistance to glycopeptides, first described in 1986 in Europe, has increasingly been reported worldwide and it makes the treatment of enterococcal infections a challenge. Portuguese information about vancomycin-resistant enterococci (VRE) is scarce and the last data are from 1996/1997.1 Moreover, characterization of genes conferring resistance to glycopeptides as well as clonal relatedness among isolates have never been carried out in Portugal. Our objectives were: (i) to characterize the glycopeptide resistance at genetic level; (ii) to know the epidemiological pattern; and (iii) to determine the multiresistance profile of VRE isolated between 1996 and 2001 in a central teaching hospital of 1600 beds in one of the largest Portuguese cities (Coimbra).
Twenty-eight VRE isolates were recovered from different patients during the study period. MICs of 12 antibiotics (Table
) were determined by an agar dilution method following NCCLS guidelines. The presence of ß-lactamase was investigated using the nitrocefin test. Species identification and characterization of glycopeptide resistance genotype was carried out by PCR, using ddl (Enterococcus faecium), ddl (Enterococcus faecalis), vanA and vanB, oligonucleotide primer sets described by Dukta-Malen et al.,2 and the vanC1 and vanC2 primer sets reported by Clark et al.3 and Satake et al.,4 respectively. Clonal related-ness of VRE isolates was studied by PFGE as previously described by Murray et al.,5 using SmaI as restriction endonuclease.
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Resistance to several antibiotics commonly used in enterococcal infections was observed. High level of resistance (HLR) to aminoglycosides was common. Twelve isolates (11 E. faecium and one E. faecalis) showed HLR to gentamicin, streptomycin and kanamycin, and 10 isolates (six E. faecium and four E. faecalis) exhibited HLR to gentamicin and kanamycin. HLR to kanamycin plus streptomycin, HLR to kanamycin or HLR to streptomycin was found in one isolate each. All 28 isolates studied were resistant to erythromycin and only two of them were susceptible to ciprofloxacin. Of the antimicrobial agents studied, chloramphenicol demonstrated the greatest activity, although 16 isolates had reduced susceptibility to this antibiotic. It is important to note that linezolid showed good activity against all enterococcal isolates (MIC50 = 2 mg/L and MIC90 = 4 mg/L). Although 27 isolates exhibited the VanA phenotype and one E. faecium isolate the VanB phenotype, the vanA gene was detected in all 28 VRE. None of the ampicillin-resistant isolates showed ß-lactamase activity. By PFGE, we observed 22 different clonal types corresponding to the 28 isolates studied. Only two of them (clones A and B) were found in more than one patient (Table). Clone A (E. faecium) was detected in five different patients on the liver transplant ward from August 1999 to November 2000. Liver transplant patients are one of the specific populations in which VRE cause serious and often fatal disease. These E. faecium isolates were multiresistant, showing decreased susceptibility to at least eight antibiotics (Table
). Clone B (E. faecalis) was found in three patients on the nephrology ward between 1999 and June 2000. These E. faecalis isolates were also resistant to macrolides and ciprofloxacin and highly resistant to aminoglycosides. The dissemination of vanA E. faecium and E. faecalis strains within restricted wards might be easily explained by cross-transmission. Multidrug-resistant enterococci continue to pose problems in hospital environments worldwide. The best available evidence indicates that the emergence and spread of these pathogens are favoured by poor infection control techniques and by antibiotic selective pressure. Therapeutic alternatives for multiresistant isolates are currently scarce and linezolid may be an answer. The clonal diversity found in this hospital is similar to that observed in other European countries, where dissemination of transferable genetic elements (i.e. transposons) among strains is more frequently described than the spread of endemic strains.6
Notes
* Corresponding author. Tel +351-2-22078946; Fax: +351-2-2003977; E-mail: lpeixe{at}ff.up.pt 
References
1 . Melo-Cristino, J. (1998). Antimicrobial resistance in Staphylococci and Enterococci in 10 Portuguese hospitals in 1996 and 1997. Microbial Drug Resistance 4, 319–24.
2 . Dukta-Malen, S., Evers, S. & Courvalin P. (1995). Detection of glycopeptide resistance genotypes and identification to the species level of clinically relevant enterococci by PCR. [Erratum, Journal of Clinical Microbiology (1995) 33, 1434] Journal of Clinical Microbiology 33, 24–7. [Abstract]
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Clark, N., Teixeira, L., Facklam, R. & Tenover, F. (1998). Detection and differentiation of vanC-1, vanC-2, and vanC-3 glycopeptide resistance genes in enterococci. Journal of Clinical Microbiology 36, 2294–7.
4 . Satake, S., Clark, N., Rimland, D., Nolte, F. & Tenover, F. (1997). Detection of vancomycin-resistant enterococci in fecal samples by PCR. Journal of Clinical Microbiology 35, 2325–30. [Abstract]
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Murray, B. E., Singh, K. V., Heath, J. D., Sharma, B. R. & Weinstock, G. M. (1990). Comparison of genomic DNAs of different enterococcal isolates using restriction endonucleases with infrequent recognition sites. Journal of Clinical Microbiology 28, 2059–63.
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Kawalec, M., Gniadkowski, M. & Hryniewicz, W. (2000). Outbreak of vancomycin-resistant enterococci in a hospital in Gdansk, Poland, due to horizontal transfer of different Tn1546-like transposon variants and clonal spread of several strains. Journal of Clinical Microbiology 38, 3317–22.
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