Risk factors of community-onset urinary tract infections caused by plasmid-mediated AmpC β-lactamase-producing Enterobacteriaceae.
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 bla(CIT), followed by bla(DHA)/bla(EBC), and bla(MOx).


CONCLUSIONS
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.
Division of Infectious Diseases, Taipei Veterans General Hospital, Taipei, Taiwan; Department of Medicine, National Yang-Ming University Hospital, Yilan, Taiwan.
Chi-Hung
CH
Lee
Division of Infectious Diseases, Taipei Veterans General Hospital, Taipei, Taiwan; Institute of Clinical Medicine, National Yang-Ming University, School of Medicine, Taipei, Taiwan; Department of Emergency Medicine, Taipei Veterans General Hospital, Taipei, Taiwan.
Yi-Tzu
YT
Lee
Division of Infectious Diseases, Taipei Veterans General Hospital, Taipei, Taiwan; Department of Internal Medicine, Taipei City Hospital, Zhongxing Branch, Taipei, Taiwan.
Che-Hsuan
CH
Kung
Division of Infectious Diseases, Taipei Veterans General Hospital, Taipei, Taiwan.
Wen-Wei
WW
Ku
Division of Infectious Diseases, Taipei Veterans General Hospital, Taipei, Taiwan; Institute of Clinical Medicine, National Yang-Ming University, School of Medicine, Taipei, Taiwan; National Institute of Infectious Diseases and Vaccinology, National Health Research Institutes, Miaoli County, Taiwan. Electronic address: ludwigvantw@gmail.com.
Shu-Chen
SC
Kuo
Institute of Clinical Medicine, National Yang-Ming University, School of Medicine, Taipei, Taiwan.
Te-Li
TL
Chen
Division of Infectious Diseases, Taipei Veterans General Hospital, Taipei, Taiwan; Institute of Clinical Medicine, National Yang-Ming University, School of Medicine, Taipei, Taiwan.
Chang-Phone
CP
Fung
D000368:Aged; D000369:Aged, 80 and over; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D017714:Community-Acquired Infections / Q000453:epidemiology*; D004755:Enterobacteriaceae / Q000201:enzymology* / Q000235:genetics / Q000302:isolation & purification; D004756:Enterobacteriaceae Infections / Q000453:epidemiology*; D005260:Female; D006784:Hospitals, Teaching; D006801:Humans; D008297:Male; D008826:Microbial Sensitivity Tests; D010957:Plasmids / Q000032:analysis*; D016133:Polymerase Chain Reaction; D011446:Prospective Studies; D012307:Risk Factors; D013624:Taiwan / Q000453:epidemiology; D062606:Tertiary Care Centers; D014552:Urinary Tract Infections / Q000453:epidemiology*; D001618:beta-Lactamases / Q000235:genetics / Q000378:metabolism*
D001426:Bacterial Proteins; C048795:AmpC beta-lactamases; D001618:beta-Lactamases
AmpC β-lactamase; Community-onset; Plasmid-mediated; Risk factors; Urinary tract infections