Intracellular accumulation of linezolid in Escherichia coli, Citrobacter freundii and Enterobacter aerogenes: role of enhanced efflux pump activity and inactivation

Schumacher, Anja; Trittler, Rainer; Bohnert, Jürgen A.; Kümmerer, Klaus; Pagès, Jean‐Marie; Kern, Winfried V.

doi:10.1093/jac/dkl380

Cited by 84 publications

(70 citation statements)

References 18 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…In this regard, it has been demonstrated that the intracellular concentration of linezolid in strains of E. coli, E. aerogenes, and Citrobacter freundii is comparatively low due to the efficient efflux of the drug by the resistance-nodulationdivision-type efflux pump (25).…”

Section: Resultsmentioning

confidence: 99%

Cloning, Nucleotide Sequencing, and Analysis of the AcrAB-TolC Efflux Pump of Enterobacter cloacae and Determination of Its Involvement in Antibiotic Resistance in a Clinical Isolate

Pérez

Canle

Latasa

et al. 2007

Antimicrob Agents Chemother

View full text Add to dashboard Cite

Enterobacter cloacae is an emerging clinical pathogen that may be responsible for nosocomial infections. Management of these infections is often difficult, owing to the high frequency of strains that are resistant to disinfectants and antimicrobial agents in the clinical setting. Multidrug efflux pumps, especially those belonging to the resistance-nodulation-division family, play a major role as a mechanism of antimicrobial resistance in gram-negative pathogens. In the present study, we cloned and sequenced the genes encoding an AcrAcBTolC-like efflux pump from an E. cloacae clinical isolate (isolate EcDC64) showing a broad antibiotic resistance profile. Sequence analysis showed that the acrR, acrA, acrB, and tolC genes encode proteins that display 79.8%, 84%, 88%, and 82% amino acid identities with the respective homologues of Enterobacter aerogenes and are arranged in a similar pattern. Deletion of the acrA gene to yield an AcrA-deficient EcDC64 mutant (Ec⌬acrA) showed the involvement of AcrAB-TolC in multidrug resistance in E. cloacae. However, experiments with an efflux pump inhibitor suggested that additional efflux systems also play a role in antibiotic resistance. Investigation of several unrelated isolates of E. cloacae by PCR analysis revealed that the AcrAB system is apparently ubiquitous in this species.Multidrug efflux pumps, especially those belonging to the resistance-nodulation-division family, play a major role in establishing the "intrinsic or acquired" resistance of gram-negative bacteria to a wide range of toxic compounds, including antibiotics (20).A well-studied example is the AcrAB-TolC multidrug resistance (MDR) tripartite pump system of Escherichia coli, which confers resistance to a wide variety of lipophilic and amphiphilic compounds, including dyes, detergents, and antimicrobial agents such as ethidium bromide, crystal violet, sodium dodecyl sulfate, bile acids, tetracycline, chloramphenicol, fluoroquinolones, ␤-lactams, erythromycin, and fusidic acid (17, 18). The presence of similar systems has been reported for other members of Enterobacteriaceae (2,9,11,12,14,15,16,21,28).The species of Enterobacter that most commonly cause nosocomial infections are E. cloacae and E. aerogenes (24). The existence of an acrB-like gene (11) has previously been identified in E. cloacae, although none of the components of the efflux pump have been cloned.The objectives of the present study were (i) to characterize the genes encoding the AcrAB-TolC-like efflux pump of E. cloacae and (ii) to determine the involvement of this efflux pump in MDR in E. cloacae. The clinical strain used in the study was an MDR strain of E. cloacae (EcDC64) which overexpressed the AcrAB system and also overexpressed the chromosomal ampC gene and exhibited a drastic reduction of ompC gene expression.(These results were presented in part at the 45th Interscience Conference on Antimicrobial Agents and Chemotherapy [2a].) MATERIALS AND METHODSBacterial strains and growth media. The bacterial strains used in the study are listed i...

show abstract

Section: Resultsmentioning

confidence: 99%

Cloning, Nucleotide Sequencing, and Analysis of the AcrAB-TolC Efflux Pump of Enterobacter cloacae and Determination of Its Involvement in Antibiotic Resistance in a Clinical Isolate

Pérez

Canle

Latasa

et al. 2007

Antimicrob Agents Chemother

View full text Add to dashboard Cite

show abstract

“…In vitro selection of fluoroquinolone-resistant mutants showed the importance of increased efflux in practically all cases (241). Intrinsic resistance to linezolid is mediated by AcrB in this species as well as others (242). A C. freundii isolate containing the plasmid-encoded RND pump was reported recently (243) (see Drug Efflux Genes on Plasmids, below).…”

Section: Citrobacter Sppmentioning

confidence: 88%

“…Newer ketolides (e.g., cethromycin and solithromycin) and oxazolidinones (posizolid, radezolid, and tedizolid) are still the agents mainly against Gram-positive bacteria (944), and the lack of potency for Gram-negative bacilli is likely attributable to drug efflux and the OM permeability barrier, as shown with earlier members of their classes (85,242,266,971). For example, solithromycin is clearly a strong substrate for three pumps, MtrCDE, MacAB, and NorM, of different transporter families (647).…”

Section: Multidrug Efflux Pumps As a Challenge In Drug Developmentmentioning

confidence: 99%

The Challenge of Efflux-Mediated Antibiotic Resistance in Gram-Negative Bacteria

2015

View full text Add to dashboard Cite

SUMMARY The global emergence of multidrug-resistant Gram-negative bacteria is a growing threat to antibiotic therapy. The chromosomally encoded drug efflux mechanisms that are ubiquitous in these bacteria greatly contribute to antibiotic resistance and present a major challenge for antibiotic development. Multidrug pumps, particularly those represented by the clinically relevant AcrAB-TolC and Mex pumps of the resistance-nodulation-division (RND) superfamily, not only mediate intrinsic and acquired multidrug resistance (MDR) but also are involved in other functions, including the bacterial stress response and pathogenicity. Additionally, efflux pumps interact synergistically with other resistance mechanisms (e.g., with the outer membrane permeability barrier) to increase resistance levels. Since the discovery of RND pumps in the early 1990s, remarkable scientific and technological advances have allowed for an in-depth understanding of the structural and biochemical basis, substrate profiles, molecular regulation, and inhibition of MDR pumps. However, the development of clinically useful efflux pump inhibitors and/or new antibiotics that can bypass pump effects continues to be a challenge. Plasmid-borne efflux pump genes (including those for RND pumps) have increasingly been identified. This article highlights the recent progress obtained for organisms of clinical significance, together with methodological considerations for the characterization of MDR pumps.

show abstract

“…Linezolid appeared on the market in 2000 for treatment of serious infections caused by Gram-positive bacteria resistant to other antibiotics, including streptococci, vancomycin-resistant enterococci (VRE), and methicillin-resistant Staphylococcus aureus (MRSA) (9). It is not well suited for fighting Gram-negative pathogenic bacteria that are intrinsically resistant due to efflux pumps that force linezolid out of the cell faster than it can accumulate (1,74). Linezolid is one of the few truly new antibiotics that have been introduced in many years, as most newcomers are derivatives of existing drugs.…”

Section: Linezolidmentioning

confidence: 99%

Resistance to Linezolid Caused by Modifications at Its Binding Site on the Ribosome

Long

Vester

2012

Antimicrob Agents Chemother

306

204

View full text Add to dashboard Cite

Linezolid is an oxazolidinone antibiotic in clinical use for the treatment of serious infections of resistant Gram-positive bacteria. It inhibits protein synthesis by binding to the peptidyl transferase center on the ribosome. Almost all known resistance mechanisms involve small alterations to the linezolid binding site, so this review will therefore focus on the various changes that can adversely affect drug binding and confer resistance. High-resolution structures of linezolid bound to the 50S ribosomal subunit show that it binds in a deep cleft that is surrounded by 23S rRNA nucleotides. Mutation of 23S rRNA has for some time been established as a linezolid resistance mechanism. Although ribosomal proteins L3 and L4 are located further away from the bound drug, mutations in specific regions of these proteins are increasingly being associated with linezolid resistance. However, very little evidence has been presented to confirm this. Furthermore, recent findings on the Cfr methyltransferase underscore the modification of 23S rRNA as a highly effective and transferable form of linezolid resistance. On a positive note, detailed knowledge of the linezolid binding site has facilitated the design of a new generation of oxazolidinones that show improved properties against the known resistance mechanisms. LINEZOLID

show abstract

Intracellular accumulation of linezolid in Escherichia coli, Citrobacter freundii and Enterobacter aerogenes: role of enhanced efflux pump activity and inactivation

Abstract: The intracellular concentration of linezolid is comparatively low owing to efficient efflux of the drug and could be increased substantially by inhibition of RND-type efflux pumps.

Cited by 84 publications

References 18 publications

Cloning, Nucleotide Sequencing, and Analysis of the AcrAB-TolC Efflux Pump of Enterobacter cloacae and Determination of Its Involvement in Antibiotic Resistance in a Clinical Isolate

Cloning, Nucleotide Sequencing, and Analysis of the AcrAB-TolC Efflux Pump of Enterobacter cloacae and Determination of Its Involvement in Antibiotic Resistance in a Clinical Isolate

The Challenge of Efflux-Mediated Antibiotic Resistance in Gram-Negative Bacteria

Resistance to Linezolid Caused by Modifications at Its Binding Site on the Ribosome

Contact Info

Product

Resources

About