BACKGROUND/AIMS: We examined the prevalence of extended-spectrum beta-lactamase (ESBL) production and the impact of ESBL on clinical outcomes in cancer patients with Enterobacter spp. bacteremia. METHODS: Using prospective cohort data on Enterobacter bacteremia obtained between January 2005 and November 2008 from a tertiary care center, the prevalence and clinical impact of ESBL production were evaluated. RESULTS: Two-hundred and three episodes of Enterobacter spp. bacteremia were identified. Thirty-one blood isolates (15.3%, 31/203) scored positive by the double-disk synergy test. Among 17 isolates in which ESBL genes were detected by polymerase chain reaction and sequencing, CTX-M (n = 12), SHV-12 (n = 11), and TEM (n = 4) were the most prevalent ESBL types. Prior usage of antimicrobial agents (77.4% vs. 54.0%, p = 0.02) and inappropriate empirical antimicrobial therapy (22.6% vs. 3.0%, p < 0.001) were more commonly encountered in the ESBL-positive group than in the extended-spectrum cephalosporin-susceptible ESBL-negative group, respectively. Clinical outcomes did not differ significantly between the two groups (30-day mortality rate, 19.4% vs. 17.0%, p = 0.76; median length of hospital stay, 24.0 days vs. 30.5 days, p = 0.97). Initial presentation of severe sepsis/septic shock, pneumonia, and intra-abdominal infection were independently associated with 30-day mortality. CONCLUSIONS: The prevalence of ESBL-producing isolates was 15.3% in cancer patients with Enterobacter bacteremia. Although inappropriate empirical therapy was more common in the ESBL-positive group, ESBL production was not associated with poorer outcomes.
Adult ; Aged ; Anti-Bacterial Agents/therapeutic use ; Bacteremia/*complications/drug therapy/microbiology ; Child ; Cohort Studies ; Enterobacter/*enzymology/genetics ; Enterobacteriaceae Infections/*complications/drug therapy/microbiology ; Female ; Humans ; Infant ; Male ; Middle Aged ; Neoplasms/*complications ; Prospective Studies ; Treatment Outcome ; beta-Lactamases/*biosynthesis/genetics

OBJECTIVETo investigate the status of the drug resistance and the ampC gene expression of Enterobacter cloacae.

METHODSDisk diffusion tests were made for detecting the susceptibility of antimicrobial agents against Enterobacter cloacae. AmpC gene was amplified by polymerase chain reaction (PCR) and verified by DNA sequencing. AmpC gene expression was analyzed according to antimicrobial agent sensitive phenotype.

RESULTSThe sensitivity rates of 144 strains to imipenam, cefepime and cefoperazone/sulbactam were 98.61%, 65.97% and 63.89%, respectively. The sensitivity rates of 144 strains to other antimicrobial agents were lower. Among the 144 strains 120 were found to be positive by PCR for ampC. The PCR product showed high homology to the GenBank ampC sequence. Stably derepressed strains, hyperinducible strains and unexpressing or lower level expressing strains accounted for 30.0% (36/120), 37.5% (45/120), and 32.5% (39/120), respectively. Fifty-six out of 120 strains (46.67%) also produced extended spectrum beta-lactamases (ESBLs). The hyperinducible strains were highly sensitive to all the antimicrobial agents except amoxicillin/clavulanic acid and cefuroxime, while the stably derepressed strains were only sensitive to imipenam and cefepime. However, sensitivity to cefepime decreased if the strains also produced ESBLs.

CONCLUSIONSThe drug resistant status of Enterobacter cloacae is severe. Clearing out the expressive status of ampC gene will be helpful in selection of antimicrobial agents in the treatment of clinical infection.

Cefoperazone ; pharmacology ; Drug Resistance, Bacterial ; Enterobacter cloacae ; drug effects ; enzymology ; genetics ; Gene Expression ; Genes, Bacterial ; genetics ; Imipenem ; pharmacology ; Microbial Sensitivity Tests ; Polymerase Chain Reaction ; Sulbactam ; pharmacology ; beta-Lactamases ; analysis