title: The relationship between antecedent antibiotic use and resistance to extended-spectrum cephalosporins in group I beta-lactamase-producing organisms.
abstract: Gram-negative pathogens are increasingly resistant to extended-spectrum cephalosporins (ESCs). Using a prospective, case-controlled observational study, we examined the prevalence and the risk factors for development of resistance to ESCs in group I beta-lactamase-producing organisms. Of the 386 isolates of Enterobacter species, Pseudomonas aeruginosa, Citrobacter species, and Serratia marsescens from 340 consecutive patients, 70 (18.1%) were resistant to ESCs; the highest rates of resistance were found among Citrobacter freundii (40.9%), Enterobacter cloacae (31.1%), and Enterobacter aerogenes isolates (18.9%). Patients' prior antibiotic use and the mean number of antibiotics used were significantly greater in association with resistant vs. susceptible isolates. Resistance was associated with prior use of ceftizoxime or cefotaxime (P = .008), ceftazidime (P = .004), and piperacillin (P = .001). Other antibiotics were not associated with resistance. Resistance was less frequent in patients receiving ESCs and an aminoglycoside. We conclude that prior use of ESCs is associated with the isolation of resistant group I beta-lactamase-producing organisms. Concomitant use of an aminoglycoside may decrease this risk.
authors.affiliation: University of California-Davis School of Medicine, Medical Center, Sacramento 95817, USA.
authors.forename: K L
authors.initials: KL
authors.lastname: Jacobson
authors.forename: S H
authors.initials: SH
authors.lastname: Cohen
authors.forename: J F
authors.initials: JF
authors.lastname: Inciardi
authors.forename: J H
authors.initials: JH
authors.lastname: King
authors.forename: W E
authors.initials: WE
authors.lastname: Lippert
authors.forename: T
authors.initials: T
authors.lastname: Iglesias
authors.forename: C J
authors.initials: CJ
authors.lastname: VanCouwenberghe
mesh_terms: D000328:Adult; D016022:Case-Control Studies; D002511:Cephalosporins / Q000494:pharmacology*; D002954:Citrobacter / Q000187:drug effects; D003428:Cross Infection / Q000188:drug therapy / Q000382:microbiology; D004352:Drug Resistance, Microbial; D004754:Enterobacter / Q000187:drug effects; D004755:Enterobacteriaceae / Q000187:drug effects* / Q000201:enzymology* / Q000302:isolation & purification; D004756:Enterobacteriaceae Infections / Q000188:drug therapy / Q000382:microbiology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D011550:Pseudomonas aeruginosa / Q000187:drug effects; D012307:Risk Factors; D012706:Serratia marcescens / Q000187:drug effects; D001618:beta-Lactamases / Q000096:biosynthesis*
chemical_list: D002511:Cephalosporins; D001618:beta-Lactamases