1792 • CID 2005:40 (15 June) • Pop-Vicas and D’Agata
M A J O R A R T I C L E
The Rising Influx of Multidrug-Resistant
Gram-Negative Bacilli into a Tertiary Care Hospital
Aurora E. Pop-Vicas and Erika M. C. D’Agata
Division of Infectious Diseases, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts
Quantification of the prevalence and the common antimicrobial coresistance patterns ofMDR gram-negativebacilli
(MDR-GNB) isolates recovered from patients at hospital admission, as well as identification of patients with a
high risk of harboring MDR-GNB, would have important implications for patient care.
Over a 6-year period, patients who harbored MDR-GNB (i.e., patients who had MDR-GNB isolates
recovered from clinical cultures within the first 48 h after hospital admission) were identified.“MDR-GNBisolates”
were defined as Pseudomonas aeruginosa, Escherichia coli, Enterobacter cloacae, and Klebsiella species isolates with
resistance to at least 3 antimicrobial groups. A case-control study was performed to determine the independent
risk factors for harboring MDR-GNB at hospital admission.
Between 1998 and 2003, the prevalence of MDR-GNB isolates recovered from patients at hospital
admission increased significantly for all isolate species (P ! .001
Of 464 MDR-GNB isolates, 12%, 35%, and 53% of isolates were coresistant to 5, 4, and 3 antimicrobial groups,
respectively. Multivariable analysis identified age ?65 years (odds ratio [OR], 2.8; 95% confidence interval [CI],
1.1–7.4;), prior exposure to antibiotics for ?14 days (OR, 8.7; 95% CI, 2.5 –30;P ! .04
residence in a long-term care facility (OR, 3.5; 95% CI, 1.3–9.4;
MDR-GNB at hospital admission.
A substantial number of patients harbor MDR-GNB at hospital admission. Identification of
common coresistance patterns among MDR-GNB isolates may assist in the selection of empirical antimicrobial
therapy for patients with a high risk of harboring MDR-GNB.
The prevalence of multidrug resistance (MDR) among gram-negative bacilli is rapidlyincreasing.
), with the exception of P. aeruginosa ( ).
P p .09
), and prior
P ! .001
) as independent risk factors for harboringP ! .01
The prevalence of multidrug resistance (MDR) among
gram-negative bacilli is increasing substantially [1–4].
Compared with infections due to antimicrobial-sus-
ceptible gram-negative bacilli, infections due to MDR
gram-negative bacilli (MDR-GNB) lead to worse out-
comes, including longer hospital stays, increased mor-
tality, and greater costs of hospitalization [5–7].
Although antimicrobial-resistant pathogens histori-
cally have been considered to be primarily nosoco-
mial pathogens, it has now become evident that these
pathogens have spread to other health care settings and
into the community, resulting in an influx of patients
who have antimicrobial-resistant pathogens isolated at
Received 8 December 2004; accepted 8 February 2005; electronically published
6 May 2005.
Reprints or correspondence: Dr. Aurora E. Pop-Vicas, Beth Israel Deaconess
Medical Ctr., Div. of Infectious Diseases, 330 Brookline Ave., E. Campus Mailstop
SL-435, Boston, MA 02215 (email@example.com).
Clinical Infectious Diseases2005;40:1792–8
? 2005 by the Infectious Diseases Society of America. All rights reserved.
hospital admission [8, 9]. The temporal trends in the
prevalence of MDR-GNB isolates recovered at hospital
admission are not known. Quantification of the pro-
portion of patients who harbor MDR-GNB at hospital
admission and identification of common coresistance
patterns are important to delineate, because findings
would assist in the selection of empirical antimicrobial
therapy. Although previous studies have identified risk
factors for harboring MDR-GNBduringhospitalization
[10–12], risk factors for harboring MDR-GNB at hos-
pital admission have not been elucidated.Identification
of a subgroup of patients who have a high risk of har-
boring MDR-GNB at hospital admission would have
important implications for patient care. A 6-year study
was therefore performed at a tertiary care center, to
further the understanding of the epidemiology of MDR-
GNB at hospital admission.
The Beth Israel Deaconess Medical Center(Boston,MA)
is a 530-bed tertiary-care teaching hospital with 7 in-
by guest on December 25, 2015
1798 • CID 2005:40 (15 June) • Pop-Vicas and D’Agata
the judicious use of antimicrobials is required. Although there
has been an abundance of studies focusing on the mechanisms
of dissemination and the prevention of infections due toMRSA
or VRE, the present study and other studies emphasize the
urgent need to expand these investigations toincludeinfections
due to MDR-GNB.
Potential conflicts of interest.
from Merck. A.E.P.-V.: no conflicts.
E.M.C.D. has received research funding
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