Improving the assessment of vancomycin-resistant enterococci by routine screening.
BACKGROUND
As infection with vancomycin-resistant enterococci (VRE) increases in hospitals, knowledge about VRE reservoirs and improved accuracy of epidemiologic measures are needed. Many assessments underestimate incidence by including prevalent carriers in at-risk populations. Routine surveillance cultures can substantially improve prevalence and incidence estimates, and assessing the range of improvement across diverse units is important.


METHODS
We performed a retrospective cohort study using accurate at-risk populations to evaluate the range of benefit of admission and weekly surveillance cultures in detecting unrecognized VRE in 14 patient-care units.


RESULTS
We assessed 165 unit-months. The admission prevalence of VRE was 2.2%-27.2%, with admission surveillance providing 2.2-17-fold increased detection. Medical units were significantly more likely to admit VRE carriers than were surgical units. Monthly incidence was 0.8%-9.7%, with weekly surveillance providing 3.3-15.4-fold increased detection. The common practice of reporting incidence using the total number of patients, rather than patients at risk, underestimated incidence by one-third. Overall, routine surveillance prevented the misclassification of 43.0% (unit range, 0%-85.7%) of "incident" carriers on the basis of clinical cultures alone and increased VRE precaution days by 2.4-fold (unit range, 2.0-2.6-fold).


CONCLUSIONS
Routine surveillance markedly increases the detection of VRE, despite variability across patient-care units. Correct denominators prevent the substantial underestimation of incidence.
Huang
Susan S
SS
Brigham and Women's Hospital, Channing Laboratory and Department of Infection Control, Harvard Medical School, and Harvard Pilgrim Health Care, Boston, MA 02115, USA. sshuang@partners.org
Rifas-Shiman
Sheryl L
SL
Pottinger
Jean M
JM
Herwaldt
Loreen A
LA
Zembower
Teresa R
TR
Noskin
Gary A
GA
Cosgrove
Sara E
SE
Perl
Trish M
TM
Curtis
Amy B
AB
Tokars
Jerome L
JL
Diekema
Daniel J
DJ
Jernigan
John A
JA
Hinrichsen
Virginia L
VL
Yokoe
Deborah S
DS
Platt
Richard
R
D000046:Academic Medical Centers; D000328:Adult; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002353:Carrier State / Q000175:diagnosis / Q000517:prevention & control*; D015331:Cohort Studies; D003955:Diagnostic Tests, Routine / Q000592:standards*; D018563:Disease Notification / Q000592:standards; D016983:Enterococcus / Q000187:drug effects* / Q000302:isolation & purification*; D016908:Gram-Positive Bacterial Infections / Q000175:diagnosis / Q000517:prevention & control*; D006801:Humans; D015994:Incidence; D018802:Patient-Centered Care; D012189:Retrospective Studies; D014481:United States / Q000453:epidemiology; D014640:Vancomycin / Q000494:pharmacology*; D020713:Vancomycin Resistance
D000900:Anti-Bacterial Agents; D014640:Vancomycin