Abstract
Bloodstream infection (BSI) due to carbapenem-resistant Enterobacteriaceae (CRE) has a high mortality rate and is a serious threat worldwide. Ten CRE strains (eight Enterobacter cloacae, one Klebsiella pneumoniae and one Citrobacter freundii) were isolated from the blood of nine patients, a percentage of whom had been treated with indwelling devices. The steps taken to establish cause included minimum inhibitory concentration (MIC) tests, a pulsed-field gel electrophoresis (PFGE), biofilm study, a multiplex PCR for resistant genes of carbapenemases and extended-spectrum beta-lactamases (ESBLs), and plasmid incompatibility typing. All strains showed a tendency toward resistance to multiple antibiotics, including carbapenems. Frequently isolated genes of ESBLs and carbapenemases include blaTEM-1 (four strains), blaSHV-12 (four strains) and blaIMP-1 (six strains). A molecular analysis by PFGE was used to divide the XbaI-digested genomic DNAs of 10 CRE strains into eight patterns, and the analysis showed that three E. cloacae strains detected from two patients were either identical or closely related. The biofilm production of all CRE strains was examined using a microtiter biofilm assay, and biofilm growth in continuous flow chambers was observed via the use of a confocal laser scanning microscope. Our study indicates that biofilm formation on indwelling devices may pose a risk of BSI due to CRE.
Highlights
Hospital-acquired infection caused by carbapenem-resistant Enterobacteriaceae (CRE) is a serious threat for poor clinical outcomes, and CRE outbreaks have already been reported worldwide [1,2,3]
Between September 2014 and February 2016, there were 10 CRE strains (8 Enterobacter cloacae, one K. pneumoniae, and one Citrobacter freundii) that were isolated from blood samples of 9 hospitalized patients in Kurume University Hospital, which is a 1025-bed tertiary care medical center
The minimum inhibitory concentration (MIC) of cefepime, cefmetazole, imipenem, meropenem, piperacillin/tazobactam, amikacin and levofloxacin were determined in reference to WalkAway96plus (Beckman Coulter, Inc., Brea, CA, USA) via the broth microdilution method in accordance with the guidelines of the Clinical and Laboratory Standards Institute [14]
Summary
Hospital-acquired infection caused by carbapenem-resistant Enterobacteriaceae (CRE) is a serious threat for poor clinical outcomes, and CRE outbreaks have already been reported worldwide [1,2,3]. There are numerous different types of carbapenemase enzymes, such as the KPC, OXA-48-like, VIM, NDM, and IMP enzymes. The distributions of these enzymes differ by geographical location. The bloodstream infection (BSI) is a serious clinical problem due to multiple forms of the existence of antibiotic resistance and high mortality rates [6,7,8]. Microorganisms that cause BSI often produce biofilms. Bacterial biofilms are recognized as important causes of a variety of human infections, including infections of prosthetic devices, endocarditis, dental caries, pneumonia in cystic fibrosis, and others [10]
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