RESUMO
Intestinal flora contains a reservoir of Gram-negative bacilli (GNB) resistant to cephalosporins, which are potentially pathogenic for intensive care unit (ICU) patients; this has led to increasing use of carbapenems. The emergence of carbapenem resistance is a major concern for ICUs. Therefore, in this study, we aimed to assess the intestinal carriage of imipenem-resistant GNB (IR-GNB) in intensive care patients. For 6 months, 523 consecutive ICU patients were screened for rectal IR-GNB colonization upon admission and weekly thereafter. The phenotypes and genotypes of all isolates were determined, and a case control study was performed to identify risk factors for colonization. The IR-GNB colonization rate increased regularly from 5.6% after 1 week to 58.6% after 6 weeks in the ICU. In all, 56 IR-GNB strains were collected from 50 patients: 36 Pseudomonas aeruginosa strains, 12 Stenotrophomonas maltophilia strains, 6 Enterobacteriaceae strains, and 2 Acinetobacter baumannii strains. In P. aeruginosa, imipenem resistance was due to chromosomally encoded resistance (32 strains) or carbapenemase production (4 strains). In the Enterobacteriaceae strains, resistance was due to AmpC cephalosporinase and/or extended-spectrum ß-lactamase production with porin loss. Genomic comparison showed that the strains were highly diverse, with 8 exceptions (4 VIM-2 carbapenemase-producing P. aeruginosa strains, 2 Klebsiella pneumoniae strains, and 2 S. maltophilia strains). The main risk factor for IR-GNB colonization was prior imipenem exposure. The odds ratio for colonization was already as high as 5.9 (95% confidence interval [95% CI], 1.5 to 25.7) after 1 to 3 days of exposure and increased to 7.8 (95% CI, 2.4 to 29.8) thereafter. In conclusion, even brief exposure to imipenem is a major risk factor for IR-GNB carriage.
Assuntos
Acinetobacter baumannii/efeitos dos fármacos , Antibacterianos/efeitos adversos , Enterobacteriaceae/efeitos dos fármacos , Infecções por Bactérias Gram-Negativas/tratamento farmacológico , Imipenem/efeitos adversos , Pseudomonas aeruginosa/efeitos dos fármacos , Stenotrophomonas maltophilia/efeitos dos fármacos , Resistência beta-Lactâmica/efeitos dos fármacos , Acinetobacter baumannii/enzimologia , Acinetobacter baumannii/crescimento & desenvolvimento , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Antibacterianos/administração & dosagem , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Técnicas de Tipagem Bacteriana , Estudos de Casos e Controles , Colo/microbiologia , Enterobacteriaceae/enzimologia , Enterobacteriaceae/crescimento & desenvolvimento , Feminino , Expressão Gênica/efeitos dos fármacos , Infecções por Bactérias Gram-Negativas/microbiologia , Humanos , Imipenem/administração & dosagem , Unidades de Terapia Intensiva , Masculino , Pessoa de Meia-Idade , Pseudomonas aeruginosa/enzimologia , Pseudomonas aeruginosa/crescimento & desenvolvimento , Stenotrophomonas maltophilia/enzimologia , Stenotrophomonas maltophilia/crescimento & desenvolvimento , beta-Lactamases/genética , beta-Lactamases/metabolismoRESUMO
Time-to-positivity (TTP) of first positive blood cultures growing Gram-negative bacilli (GNB) was investigated. When anaerobic vials were positive first, TTP ≤ 18 h differentiated Enterobacteriaceae from strict anaerobic Gram-negative bacilli (PPV 98.8%). When the aerobic ones were first, TTP ≤ 13 h differentiated Enterobacteriaceae from Pseudomonas aeruginosa and other GNB (PPV 80.8%).