Abstract
Purpose
The rates of vancomycin resistance among enterococci (VRE) have been increasing worldwide. However, reports on vancomycin-resistant enterococci (VRE) are easily biased and meta-data reporting is insufficient. Additionally, no standardised protocol for VRE testing currently exists. The aim of our study was to investigate, for the first time, the impact of introduced bias in VRE reports. We also analysed the sensitivity of our in-house screening test for VRE, namely, a broth-enriched PCR assay.
Methods
Retrospective review of microbial and clinical data on all patients tested for VRE who had been admitted to a large university hospital over a 5-year period and an analysis of the possible impact of introduced bias. Our screening test was also evaluated using clinical isolates.
Results
A total of 27,636 screening tests were carried out over the 5-year study period, of which 2,459 were VRE-positive. The number of screening tests increased dramatically over the study period, with 1,053 tests carried out on 435 patients in 2006 and 9,444 tests carried out on 5,104 patients in 2010. VRE prevalence was 8.1 % over the 5-year period. The introduction of measurement bias caused a clear overestimation of absolute VRE numbers. The sensitivity of our screening test was 95.5 % with a positive predictive value of 39 %.
Conclusion
Biased reports lead to the implementation of high-cost containment measures that may be both unnecessary and detrimental to the patient. Our data show that systematic errors in VRE reports caused a clear overestimation of absolute VRE numbers, thereby indicating an outbreak situation even though the actual prevalence of VRE was decreasing. We suggest that reports of VRE must take measurement and analysis biases into account, otherwise any conclusion drawn is unreliable and inconclusive.
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References
Werner G, Coque TM, Hammerum AM, Hope R, Hryniewicz W, Johnson A et al. Emergence and spread of vancomycin resistance among enterococci in Europe. Euro Surveill. 2008;13(47):1–11. pii: 19046.
Murray BE. Diversity among multidrug-resistant enterococci. Emerg Infect Dis. 1998;4(1):37–47.
Biedenbach DJ, Moet GJ, Jones RN. Occurrence and antimicrobial resistance pattern comparisons among bloodstream infection isolates from the SENTRY antimicrobial surveillance program (1997–2002). Diagn Microbiol Infect Dis. 2004;50(1):59–69. doi:10.1016/j.diagmicrobio.2004.05.003.
Haas EJ, Zaoutis TE, Prasad P, Li M, Coffin SE. Risk factors and outcomes for vancomycin-resistant enterococcus bloodstream infection in children. Infect Control Hosp Epidemiol. 2010;. doi:10.1086/655464.
Song JY, Cheong HJ, Jo YM, Choi WS, Noh JY, Heo JY, et al. Vancomycin-resistant Enterococcus colonization before admission to the intensive care unit: a clinico-epidemiologic analysis. Am J Infect Control. 2009;37(9):734–40. doi:10.1016/j.ajic.2008.09.025.
Theilacker C, Jonas D, Huebner J, Bertz H, Kern WV. Outcomes of invasive infection due to vancomycin-resistant Enterococcus faecium during a recent outbreak. Infection. 2009;37(6):540–3. doi:10.1007/s15010-009-9023-5.
Blot S, Depuydt P, Vandewoude K, De Bacquer D. Measuring the impact of multidrug resistance in nosocomial infection. Curr Opin Infect Dis. 2007;20(4):391–6. doi:10.1097/QCO.0b013e32818be6f7.
Weinstein JW, Tallapragada S, Farrel P, Dembry LM. Comparison of rectal and perirectal swabs for detection of colonization with vancomycin-resistant enterococci. J Clin Microbiol. 1996;34(1):210–2.
Milstone AM, Maragakis LL, Carroll KC, Perl TM. Targeted surveillance to identify children colonized with vancomycin-resistant Enterococcus in the pediatric intensive care unit. Infect Control Hosp Epidemiol. 2010;31(1):95–8. doi:10.1086/649221.
Yoonchang SW, Peck KR, Kim OS, Lee JH, Lee NY, Oh WS, et al. Efficacy of infection control strategies to reduce transmission of vancomycin-resistant enterococci in a tertiary care hospital in Korea: a 4-year follow-up study. Infect Control Hosp Epidemiol. 2007;28(4):493–5. doi:10.1086/513024.
Dutka-Malen S, Evers S, Courvalin P. Detection of glycopeptide resistance genotypes and identification to the species level of clinically relevant enterococci by PCR. J Clin Microbiol. 1995;33(5):1434.
Eigner U, Holfelder M, Oberdorfer K, Betz-Wild U, Bertsch D, Fahr AM. Performance of a matrix-assisted laser desorption ionization-time-of-flight mass spectrometry system for the identification of bacterial isolates in the clinical routine laboratory. Clin Lab. 2009;55(7–8):289–96.
Kobayashi I, Muraoka H, Iyoda T, Nishida M, Hasegawa M, Yamaguchi K. Antimicrobial susceptibility testing of vancomycin-resistant Enterococcus by the VITEK 2 system, and comparison with two NCCLS reference methods. J Med Microbiol. 2004;53(Pt 12):1229–32. doi:10.1099/jmm.0.45765-0.
Dombradi Z, Bihari Z, Horvath KI, Szabo J. Comparison of the VITEK 2 system with the E-test for the determination of glycopeptide susceptibility of vanA and vanC positive enterococci. Acta Microbiol Immunol Hung. 2010;57(3):157–63. doi:10.1556/AMicr.57.2010.3.1.
van Den Braak N, Goessens W, van Belkum A, Verbrugh HA, Endtz HP. Accuracy of the VITEK 2 system to detect glycopeptide resistance in enterococci. J Clin Microbiol. 2001;39(1):351–3. doi:10.1128/JCM.39.1.351-353.2001.
Schouten MA, Hoogkamp-Korstanje JA, Meis JF, Voss A. Prevalence of vancomycin-resistant enterococci in Europe. Eur J Clin Microbiol Infect Dis. 2000;19(11):816–22.
Goossens H, Jabes D, Rossi R, Lammens C, Privitera G, Courvalin P. European survey of vancomycin-resistant enterococci in at-risk hospital wards and in vitro susceptibility testing of ramoplanin against these isolates. J Antimicrob Chemother. 2003;51[Suppl 3]:iii5–12. doi:10.1093/jac/dkg271.
Sagel U, Schulte B, Heeg P, Borgmann S. Vancomycin-resistant enterococci outbreak, Germany, and calculation of outbreak start. Emerg Infect Dis. 2008;14(2):317–9.
Hartman JM, Forsen JW Jr, Wallace MS, Neely JG. Tutorials in clinical research: part IV: recognizing and controlling bias. Laryngoscope. 2002;112(1):23–31. doi:10.1097/00005537-200201000-00005.
Sackett DL. Bias in analytic research. J Chronic Dis. 1979;32(1–2):51–63.
Ibrahim EH, Sherman G, Ward S, Fraser VJ, Kollef MH. The influence of inadequate antimicrobial treatment of bloodstream infections on patient outcomes in the ICU setting. Chest. 2000;118(1):146–55.
Vergis EN, Hayden MK, Chow JW, Snydman DR, Zervos MJ, Linden PK, et al. Determinants of vancomycin resistance and mortality rates in enterococcal bacteremia. a prospective multicenter study. Ann Intern Med. 2001;135(7):484–92.
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Mutters, N.T., Frank, U. Sources of systematic errors in the epidemiology of vancomycin-resistant enterococci. Infection 41, 305–310 (2013). https://doi.org/10.1007/s15010-013-0410-6
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DOI: https://doi.org/10.1007/s15010-013-0410-6