Vol.55 No.3 May 2007
Prevalence and antimicrobial susceptibility of metallo-β-lactamase-producing gram-negative bacilli from clinical specimens
1)Clinical Laboratory, Juntendo University Hospital, 3-1-3 Hongo, Bunkyo-ku, Tokyo, Japan
2)Clinical Laboratory, Juntendo University Nerima Hospital
3)Department of Laboratory Medicine, Juntendo University School of Medicine
4)Transfusion Medicine and Stem Cell Regulation, Juntendo University School of Medicine
Abstract
We studied the prevalence, antimicrobial susceptibility, and performance in the screening of metallo-β-lactamase (MBL) -producing gram-negative bacilli from clinical specimens at Juntendo University Hospital from 2001 to 2005. A total of 352 nonduplicate strains were screened for MBL production by the routine antimicrobial susceptibility test and disk approximation test using the sodium mercaptoacetic acid (SMA) test. Of these, 247 MBL-positive strains were detected in genes for the IMP-1 group (blaIMP-1) by PCR in 79 (32.0%) for Pseudomonas aeruginosa, 38 (15.4%) for Pseudomonas putida/fluorescens, 37 (15.0%) for Acinetobacter spp., 11 (4.5%) for Achromobacter spp., 6 (2.4%) for Alcaligenes spp., 50 (20.2%) for Enterobacter cloacae, 12 (4.9%) for Citrobacter freundii, 7 (2.8%) for Providencia rettgeri, 3 (1.2%) for Serratia marcescens, 3 (1.2%) for Klebsiella spp., and 1 (0.4%) for Escherichia coli. No strains were detected in genes for the IMP-2 group (blaIMP-2) or VIM-2 group (blaVIM-2). There was no significant increase in number of IMP-1 group positive strains in the last 5 years except P. aeruginosa and E. cloacae. IMP-1 group positive P. aeruginosa and E. cloacae represented slightly increase in 2005 and 2003 to 2005, respectively. Susceptibility to the 10 antimicrobial agents of IMP-1 group-positive strains was species-dependent. Most strains of Pseudomonas spp., Acinetobacter baumannii, Achromobacter spp., and S. marcescens were highly and multiresistant to antimicrobials, including carbapenems and broad-spectrum β-lactams, aminoglycosides, and fluoroquinolones. Among the family Enterobacteriaceae other than S. marcescens, Acinetobacter lwoffii and Alcaligenes spp. were frequently susceptible to carbapenems. IMP-1 group-positive strains have been detected most frequently in P. aeruginosa and disseminated to other glucose-nonfermenters and Enterobacteriaceae at our hospital and nationwide. The incidence of MBL-producing P. aeruginosa was ranged from 0.3 to 1.5% in the last 5 years. In contrast, the incidence of multidrug-resistant P. aeruginosa characterizing as following two combinations: resistant to imipenem, gentamicin, and levofloxacin; resistant to imipenem, levofloxacin, and intermediate or resistant to amikacin have annually increased 3.7% and 3.9%, respectively in 2005. These results emphasize the need for daily surveillance of MBL-producing bacteria with both routine antimicrobial susceptibility tests and SMA tests in the microbiology laboratory.
Key word
metallo-β-lactamase, IMP-1, sodium mercaptoacetic acid, multidrug-resistant, Pseudomonas aeruginosa
Received
September 13, 2006
Accepted
January 30, 2007
Jpn. J. Chemother. 55 (3): 211-219, 2007
