ABSTRACT
Enterobacter aerogenes is an agent of hospital-acquired infection that exhibits a remarkable resistance to beta-lactam antibiotics during therapy. Five successive isolates of E. aerogenes infecting a patient and exhibiting a multiresistance phenotype to beta-lactam antibiotics and fluoroquinolones were investigated. Among these clinical strains, four presented resistant phenotypes during successive imipenem and colistin treatments. The involved resistance mechanisms exhibited by the successive isolates were associated with alterations of the outer membrane that caused a porin decrease and lipopolysaccharide modifications.
Subject(s)
Anti-Bacterial Agents/pharmacology , Colistin/pharmacology , Drug Resistance, Multiple, Bacterial , Enterobacter aerogenes/drug effects , Evolution, Molecular , Imipenem/pharmacology , Anti-Bacterial Agents/therapeutic use , Colistin/therapeutic use , Drug Resistance, Multiple, Bacterial/genetics , Drug Therapy, Combination , Enterobacter aerogenes/classification , Enterobacter aerogenes/genetics , Enterobacter aerogenes/isolation & purification , Enterobacteriaceae Infections/drug therapy , Enterobacteriaceae Infections/microbiology , Female , Humans , Imipenem/therapeutic use , Microbial Sensitivity Tests , Middle Aged , Porins/metabolismABSTRACT
Enterobacter aerogenes develops increased multidrug resistance via a functional alteration of outer-membrane permeability associated with a decrease in porin function. We have sequenced the gene coding the major porin of Enterobacter aerogenes, omp36. The sequence shows a high similarity with the Klebsiella pneumoniae ompK36 gene and is closely related to the enterobacterial OmpC family. Sequence analysis of several Omp36 issued from clinical strains indicated variability in putative cell-surface exposed domains. Interestingly, substitution Gly112Asp was observed in the conserved eyelet L3 region of the porin produced by two strains, C and 3. This substitution is associated with a high general beta-lactam resistance observed in these isolates and with alteration of pore properties previously described in strain 3 porin [Mol. Microbiol. 41 (2001) 189]. This is the first genetic identification of impermeability-mediated resistance to beta-lactams in various clinical E. aerogenes strains.
Subject(s)
Bacterial Outer Membrane Proteins/genetics , Cephalosporins/pharmacology , Drug Resistance, Microbial/genetics , Enterobacter aerogenes/drug effects , Imipenem/pharmacology , Mutation , Bacterial Outer Membrane Proteins/physiology , Base Sequence , Cefepime , DNA Primers , Enterobacter aerogenes/genetics , CefpiromeABSTRACT
Eubacterium callanderi is an environmental anaerobic rod-shaped bacterium first isolated in 1998 from an industrial anaerobic digester. We report on the first clinical isolate of E. callanderi, which was recovered from the blood of a patient with a bladder carcinoma. Identification of the organism was made by cell fatty acid chromatographic analysis and 16S rRNA gene sequencing.
