Population-based epidemiological study of infections caused by carbapenem-resistant Pseudomonas aeruginosa in the Calgary Health Region: importance of metallo-beta-lactamase (MBL)-producing strains.
BACKGROUND
A study was conducted in the Calgary Health Region between May 2002 and April 2004 to define the population-based epidemiological characteristics of infections caused by imipenem-resistant Pseudomonas aeruginosa and to explore the clinical outcomes due to metallo- beta -lactamase (MBL)-producing and non-MBL-producing strains.


METHODS
Detailed clinical information was obtained by chart review, and phenotypic and molecular characterizations were performed using the MBL E-test, polymerase chain reaction with sequencing, and pulsed-field gel electrophoresis.


RESULTS
A total of 228 patients with infections caused by imipenem-resistant P. aeruginosa were identified (annual incidence, 10.5 cases/100,000 population), with the highest incidence rate in those >or=75 years old. MBL-producing strains (98/228) were associated with higher rates of multidrug resistance and bacteremia. Ninety MBL-producing strains also produced VIM-2, 4 produced IMP-7, and 4 were unclassified. A cluster of VIM-2-producing strains was responsible for a nosocomial outbreak during 2003. The case-fatality rate was significantly higher for infections caused by MBL-producing strains than for those caused by non-MBL-producing strains (25% vs. 13%; relative risk, 1.98 [95% confidence interval, 1.00-3.90]; P=.05).


CONCLUSIONS
MBL-producing P. aeruginosa strains were associated with a higher case-fatality rate and invasive disease. Our study highlights the potential importance of molecular laboratory techniques in infection control and patient care.
Laupland
Kevin B
KB
Department of Medicine, University of Calgary, Centre for Anti-microbial Resistance, and Calgary Health Region, Calgary, Alberta, Canada.
Parkins
Michael D
MD
Church
Deirdre L
DL
Gregson
Daniel B
DB
Louie
Thomas J
TJ
Conly
John M
JM
Elsayed
Sameer
S
Pitout
Johann D D
JD
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001426:Bacterial Proteins / Q000096:biosynthesis*; D002170:Canada / Q000453:epidemiology; D015780:Carbapenems / Q000494:pharmacology*; D002648:Child; D002675:Child, Preschool; D003428:Cross Infection / Q000453:epidemiology*; D004196:Disease Outbreaks; D024881:Drug Resistance, Bacterial; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D008875:Middle Aged; D011552:Pseudomonas Infections / Q000175:diagnosis* / Q000453:epidemiology*; D011550:Pseudomonas aeruginosa / Q000187:drug effects* / Q000302:isolation & purification / Q000378:metabolism*; D001618:beta-Lactamases / Q000096:biosynthesis*
D001426:Bacterial Proteins; D015780:Carbapenems; C425108:beta-lactamase bla(vim-2); D001618:beta-Lactamases