title: Emergence of imipenem-resistant gram-negative bacilli in intestinal flora of intensive care patients.
abstract: 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 β-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.
authors: French National Reference Center for Bacterial Resistance in Commensal Flora, Laboratory of Bacteriology, Bichat-Claude Bernard Hospital, Assistance Publique-Hôpitaux de Paris, Paris, France.
authors: Laurence
authors: L
authors: Armand-Lefèvre
authors: Cécile
authors: C
authors: Angebault
authors: François
authors: F
authors: Barbier
authors: Emilie
authors: E
authors: Hamelet
authors: Gilles
authors: G
authors: Defrance
authors: Etienne
authors: E
authors: Ruppé
authors: Régis
authors: R
authors: Bronchard
authors: Raphaël
authors: R
authors: Lepeule
authors: Jean-Christophe
authors: JC
authors: Lucet
authors: Assiya
authors: A
authors: El Mniai
authors: Michel
authors: M
authors: Wolff
authors: Philippe
authors: P
authors: Montravers
authors: Patrick
authors: P
authors: Plésiat
authors: Antoine
authors: A
authors: Andremont
mesh_terms: D040981:Acinetobacter baumannii / Q000187:drug effects* / Q000201:enzymology / Q000254:growth & development; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000900:Anti-Bacterial Agents / Q000008:administration & dosage / Q000009:adverse effects*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D015373:Bacterial Typing Techniques; D016022:Case-Control Studies; D003106:Colon / Q000382:microbiology; D004755:Enterobacteriaceae / Q000187:drug effects* / Q000201:enzymology / Q000254:growth & development; D005260:Female; D015870:Gene Expression / Q000187:drug effects; D016905:Gram-Negative Bacterial Infections / Q000188:drug therapy* / Q000382:microbiology; D006801:Humans; D015378:Imipenem / Q000008:administration & dosage / Q000009:adverse effects*; D007362:Intensive Care Units; D008297:Male; D008875:Middle Aged; D011550:Pseudomonas aeruginosa / Q000187:drug effects* / Q000201:enzymology / Q000254:growth & development; D020615:Stenotrophomonas maltophilia / Q000187:drug effects* / Q000201:enzymology / Q000254:growth & development; D018440:beta-Lactam Resistance / Q000187:drug effects*; D001618:beta-Lactamases / Q000235:genetics / Q000378:metabolism
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D015378:Imipenem; D001618:beta-Lactamases; C063912:carbapenemase