Risk factors of community-onset urinary tract infections caused by plasmid-mediated AmpC β-lactamase-producing Enterobacteriaceae - Abstract

BACKGROUND: The AmpC β-lactamase (AmpC)-producing Enterobacteriaceae emerged worldwide.

This study was conducted to determine the risk factors of community-onset urinary tract infections (UTIs) caused by plasmid-mediated AmpC-producing Enterobacteriaceae.

METHODS: Patients who were diagnosed as community-onset UTIs caused by Enterobacteriaceae in a tertiary-care teaching hospital from December 2010 to January 2012 were included. Extended-spectrum β-lactamase (ESBL)-producing isolates were excluded. We identified plasmid-mediated AmpC-producing Enterobacteriaceae both phenotypically (by disk potentiation test and double-disk synergy test) and genotypically (by Multiplex polymerase chain reaction (PCR) assay). The demographic data, clinical characteristics, and risk factors of acquisition were described.

RESULTS: Among the 323 non-ESBL-producing Enterobacteriaceae identified in community-onset UTIs, 50 isolates were phenotypically positive for AmpC. Escherichia coli was the most common AmpC-producing organism (60%), followed by Klebsiella pneumonia (8%), and Enterobacter cloacae and Proteus mirabilis (6% for each species). The independent risk factors for acquisition of AmpC-producing Enterobacteriaceae included prior history of cerebral vascular accident (odds ratio (OR) = 2.014; 95% confidence interval (CI) = 1.007-4.031; p = 0.0048), and prior use of fluoroquinolones (OR = 4.049; 95% CI = 1.759-9.319; p = 0.001) and cephamycin (OR = 9.683; 95% CI = 2.007-45.135; p = 0.004). AmpC-producing isolates were multidrug resistant. Carbapenems, cefepime, and piperacillin/tazobactam had the best in vitro efficacy. The most commonly identified plasmid-mediated AmpC gene was blaCIT, followed by blaDHA/blaEBC, and blaMOx.

CONCLUSION: For community-onset UTIs, AmpC-producing Enterobacteriaceae should be suspected in those with prior history of cerebral vascular accident and prior use of antimicrobials. To treat these multiple-resistant isolates, carbapenems, cefepime, and piperacillin/tazobactam may be considered.

Written by:
Lee CH, Lee YT, Kung CH, Ku WW, Kuo SC, Chen TL, Fung CP.   Are you the author?
Division of Infectious Diseases, Taipei Veterans General Hospital, Taipei, Taiwan; Department of Medicine, National Yang-Ming University Hospital, Yilan, Taiwan.

Reference: J Microbiol Immunol Infect. 2013 Nov 12. pii: S1684-1182(13)00155-2.
doi: 10.1016/j.jmii.2013.08.010

PubMed Abstract
PMID: 24239065

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