Vol.60 No.5 September 2012
Isolation conditions for extended-spectrum β -lactamase-producing bacteria: Analysis of differing characteristics and causes of isolation conditions at two facilities
1)Infection Control Office, Department of Medical Safety Administration, Iwate Medical University Hospital, 19-1 Uchimaru, Morioka, Iwate, Japan
2)Division of Central Clinical Laboratory, Iwate Medical University Hospital
3)Department of Laboratory Medicine, Iwate Medical University School of Medicine
Abstract
Among drug-resistant bacteria, extended-spectrum β-lactamase(ESBL)-producing bacteria have become a major issue in nosocomial infection control. In this study, we examined ESBL-producing bacteria isolated at Iwate Medical University Hospital (University Hospital) and its affiliate, the Hanamaki Onsen Hospital (Hanamaki), during an 8-year period from April 2003 to March 2011. We then compared the isolation frequency, the types of resistance genes, and the associated incidences of infection as determined by assessing the nosocomial transmission rates.
At University Hospital, the numbers of patients from whom ESBL-producing bacteria were isolated increased sharply from 3 cases in 2003 to 40 cases in 2010. Among a total of 169 patients, 37 cases (>20%) were outpatients. At Hanamaki, however, the numbers did not increase, and the ratio of outpatients was much lower, with only 2 outpatients among a total of 88 patients treated during the study period. The resistance genes in ESBL-producing Escherichia coli were derived from the CTX-M-1 group, the CTX-M-9 group, SHV type, and TEM type in the isolates obtained from University Hospital. On the other hand, those obtained from Hanamaki were mostly from the CTX-M-9 group (90.5%), suggesting the spread of a single resistance genotype. The associated incidence rate of ESBL-producing bacteria was 27.9% at Hanamaki, which was significantly higher than the rate of 6.1% observed at University Hospital.
The characteristics of the ESBL-producing bacteria in isolates obtained from University Hospital differed from those obtained in isolates from Hanamaki. The reasons for these differences may include the fact that University Hospital is an acute-care facility that is susceptible to the spread of community-acquired infections caused by ESBL-producing bacteria, whereas Hanamaki mainly cares for elderly and long-term hospitalized patients, resulting in exposure to a high risk of nosocomial spread. To minimize the spread of nosocomial infections, appropriate monitoring should be continued at each facility, the infection-control policies of each facility should be followed precisely, and antibiotics should be used correctly.
Key word
extended-spectrum β-lactamase, infection control, factorial analysis, Escherichia coli
Received
May 25, 2012
Accepted
July 18, 2012
Jpn. J. Chemother. 60 (5): 553-559, 2012
