1 Department of Medical Microbiology, Atrium Medical Centre, P.O. Box 4446, 6401 CX Heerlen; 2 Animal Clinic Strijthagen, Stenen Brug 2, 6372 AP Landgraaf, Parkstad Limburg, The Netherlands
Keywords: veterinary, prevalence, avoparcin, glycopeptide resistance
Sir,
As the epidemic occurrence of vancomycin-resistant enterococci (VRE) has been recently noted in patients in The Netherlands, vigilance for this kind of antibiotic resistance is clearly indicated.1 VRE have already been demonstrated in poultry farmers in our region in The Netherlands.2 The presence of VRE in 16% of companion dogs has been noted in a Dutch urban veterinary practice in the city of Rotterdam.3 How these dogs became colonized by VRE is still unknown. Culture of various dog foods revealed no VRE (Dr H. Ph. Endtz, Erasmus MC, University Medical Center, Rotterdam, personal communication). The occurrence of VRE in companion dogs can have implications for transfer of these VRE (frequently Enterococcus faecium) to humans.4 Therefore, in 2002, we initiated a study into the occurrence of VRE in companion dogs in a comparable setting in the conurbation of Parkstad (Parkcity) Limburg, The Netherlands.
The test procedure was as follows: after informed consent of the dogs owners, a rectal swab was taken from 100 dogs, visiting the animal clinic for various clinical reasons. The swab was placed in a non-selective enrichment tryptone broth, incubated aerobically for 48 h at 37°C and subcultured on an agar blood plate with selective antibiotics (ceftazidime 8 mg/L and gentamicin 10 mg/L) to prevent the overgrowth by other bowel bacteria and favouring the overgrowth of enterococci. On the primary inoculation streak, a 30 µg vancomycin disc was placed as an initial screening. Suspected colonies were further processed for identification and susceptibility testing according to standard procedures.
No VRE were detected in any of these 100 companion urban dogs contrary to our initial expectation in view of the marked prevalence in urban dogs from the same sort of city environment 6 years earlier.3 If one or more dogs had been detected as a carrier of VRE, it would have been of interest to investigate the eating habits of the dogs implicated. With no VRE found, this topic was not pursued further. The current absence of VRE in these companion animals can possibly be explained by the fact that nearly 5 years had passed since the introduction of the ban on avoparcin for animal feeding by order of the European Commission in 1997. This action has already caused a significant downward trend in the prevalence rates of VRE in other previously, frequently identified groups of VRE-colonized farm animals.5 This communication may contrast with the usual pessimistic reports of increasing prevalences of bacterial resistance.
Footnotes
* Corresponding author. Tel: +31-45-5767803; Fax: +31-45-5767098; E-mail: h.wagenvoort{at}atriummc.nl
References
1
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Ridwan, B., Mascini, E., van der Reijden, N. et al. (2002). What action should be taken to prevent spread of vancomycin-resistant enterococci in European hospitals? British Medical Journal 324, 6668.
2
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Stobberingh, E. E., van den Bogaard, A., London, N. et al. (1999). Enterococci with glycopeptide resistance in turkeys, turkey farmers, turkey slaughterers, and (sub)urban residents in the south of The Netherlands: evidence for transmission of vancomycin resistance from animals to humans? Antimicrobial Agents and Chemotherapy 43, 221521.
3 . van Belkum, A., van den Braak, N., Thomassen, R. et al. (1996). Vancomycin-resistant enterococci in cats and dogs. Lancet 348, 10389.
4
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Simjee, S., White, D. G., McDermott, P. F. et al. (2002). Characterization of Tn1546 in vancomycin-resistant Enterococcus faecium isolated from canine urinary tract infections: evidence of gene exchange between human and animal enterococci. Journal of Clinical Microbiology 40, 465965.
5
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van den Bogaard, A. E., Bruinsma, N. & Stobberingh, E. E. (2000). The effect of banning avoparcin on VRE carriage in The Netherlands. Journal of Antimicrobial Chemotherapy 46, 1468.
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