scholarly journals Multidrug Resistance of a Porin Deletion Mutant of Mycobacterium smegmatis

2004 ◽  
Vol 48 (11) ◽  
pp. 4163-4170 ◽  
Author(s):  
Joachim Stephan ◽  
Claudia Mailaender ◽  
Gilles Etienne ◽  
Mamadou Daffé ◽  
Michael Niederweis
Keyword(s):  
Multidrug Resistance ◽  
Outer Membrane ◽  
Mycobacterium Smegmatis ◽  
Antibiotic Sensitivity ◽  
Chemotherapeutic Agents ◽  
Intrinsic Resistance ◽  
Successful Design ◽  
High Level ◽  
Outer Membrane Permeability

ABSTRACT Mycobacteria contain an outer membrane of unusually low permeability which contributes to their intrinsic resistance to many agents. It is assumed that small and hydrophilic antibiotics cross the outer membrane via porins, whereas hydrophobic antibiotics may diffuse through the membrane directly. A mutant of Mycobacterium smegmatis lacking the major porin MspA was used to examine the role of the porin pathway in antibiotic sensitivity. Deletion of the mspA gene caused high-level resistance of M. smegmatis to 256 μg of ampicillin/ml by increasing the MIC 16-fold. The permeation of cephaloridine in the mspA mutant was reduced ninefold, and the resistance increased eightfold. This established a clear relationship between the activity and the outer membrane permeation of cephaloridine. Surprisingly, the MICs of the large and/or hydrophobic antibiotics vancomycin, erythromycin, and rifampin for the mspA mutant were increased 2- to 10-fold. This is in contrast to those for Escherichia coli, whose sensitivity to these agents was not affected by deletion of porin genes. Uptake of the very hydrophobic steroid chenodeoxycholate by the mspA mutant was retarded threefold, which supports the hypothesis that loss of MspA indirectly reduces the permeability by the lipid pathway. The multidrug resistance of the mspA mutant highlights the prominent role of outer membrane permeability for the sensitivity of M. smegmatis to antibiotics. An understanding of the pathways across the outer membrane is essential to the successful design of chemotherapeutic agents with activities against mycobacteria.

Limited contribution of the outer-membrane penetration barrier towards intrinsic antibiotic resistance in Pseudomonas aeruginosa

1982 ◽  
Vol 28 (2) ◽  
pp. 169-175 ◽  
Author(s):  
R. Allan Scudamore ◽  
Morris Goldner
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Antibiotic Resistance ◽  
Outer Membrane ◽  
Cell Envelope ◽  
Growth Curves ◽  
Beta Lactam ◽  
Intrinsic Resistance ◽  
Beta Lactam Antibiotics ◽  
High Level

The role of the outer membrane (OM) was investigated in relation to the high level of intrinsic antibiotic resistance of Pseudomonas aeruginosa ATCC 9027. OM penetration barriers were measured by comparing turbidimetric growth curves of EDTA-treated and normal cells exposed to carbenicillin, moxalactam (LY 127935), gentamicin, tobramycin, rifampin, novobiocin, and vancomycin. OM barriers were also measured for carbenicillin and moxalactam in P. aeruginosa strain K 799/61, a hypersusceptible mutant presumed to have lost its penetration barrier in the cell envelope. Most antibiotics penetrated the OM efficiently and there was little difference between the two strains. The evidence therefore suggests that intrinsic resistance of P. aeruginosa, especially to the beta-lactam antibiotics, is not mainly due to the OM. A penetration barrier situated deeper within the cell envelope is hypothesized, the size of which in relation to any antibiotic may be estimated by comparing the IC50 values of EDTA-treated cells of the two strains.

scholarly journals Role of Porins for Uptake of Antibiotics by Mycobacterium smegmatis

2008 ◽  
Vol 52 (9) ◽  
pp. 3127-3134 ◽  
Author(s):  
Olga Danilchanka ◽  
Mikhail Pavlenok ◽  
Michael Niederweis
Keyword(s):  
Outer Membrane ◽  
Mycobacterium Smegmatis ◽  
Lipid Membrane ◽  
Model Organism ◽  
Permeability Barrier ◽  
Opportunistic Pathogens ◽  
Transport Pathways ◽  
Antibiotics Use ◽  
Outer Membrane Permeability

ABSTRACT The outer membrane of mycobacteria presents an effective permeability barrier for many antibiotics. Transport pathways across this membrane are unknown for most drugs. Here, we examined which antibiotics utilize the porin pathway across the outer membrane of the model organism Mycobacterium smegmatis. Deletion of the porins MspA and MspC drastically increased the resistance of M. smegmatis ML10 to β-lactam antibiotics, while its β-lactamase activity remained unchanged. These results are consistent with the ninefold-reduced outer membrane permeability of the M. smegmatis porin mutants for cephaloridine and strongly indicate that β-lactam antibiotics rely on the porin pathway. The porin mutant ML10 accumulated less chloramphenicol and norfloxacin and was less susceptible to these antibiotics than wild-type M. smegmatis. These results demonstrated that small and hydrophilic antibiotics use the Msp porins for entering the cell. In contrast to norfloxacin, the hydrophobic moxifloxacin was 32-fold more effective in inhibiting the growth of M. smegmatis, presumably because it was able to diffuse through the lipid membrane. Structural models indicated that erythromycin, kanamycin, and vancomycin are too large to move through the MspA channel. This study presents the first experimental evidence that hydrophilic fluoroquinolones and chloramphenicol diffuse through porins in mycobacteria. Thus, mutations resulting in less efficient porins or lower porin expression levels are likely to represent a mechanism for the opportunistic pathogens M. avium, M. chelonae, and M. fortuitum, which have Msp-like porins, to acquire resistance to fluoroquinolones.

scholarly journals Role of embB in natural and acquired resistance to ethambutol in mycobacteria.

1997 ◽  
Vol 41 (10) ◽  
pp. 2270-2273 ◽  
Author(s):  
F Alcaide ◽  
G E Pfyffer ◽  
A Telenti
Keyword(s):  
Nontuberculous Mycobacteria ◽  
Practical Implication ◽  
Acquired Resistance ◽  
Fold Increase ◽  
Drug Susceptibility ◽  
Natural Resistance ◽  
Intrinsic Resistance ◽  
Resistant Strains ◽  
High Level

The mycobacterial embCAB operon encodes arabinosyl transferases, putative targets of the antimycobacterial agent ethambutol (EMB). Mutations in embB lead to resistance to EMB in Mycobacterium tuberculosis. The basis for natural, intrinsic resistance to EMB in nontuberculous mycobacteria (NTM) is not known; neither is the practical implication of resistance to EMB in the absence of embB mutations in M. tuberculosis well understood. The conserved embB resistance-determining region (ERDR) of a collection of 13 strains of NTM and 12 EMB-resistant strains of M. tuberculosis was investigated. Genotypes were correlated with drug susceptibility phenotypes. High-level natural resistance to EMB (MIC, . or =64 microg/ml) was associated with a variant amino acid motif in the ERDR of M. abscessus, M. chelonae, and M. leprae. Transfer of the M. abscessus emb allele to M. smegmatis resulted in a 500-fold increase in the MICs. In M. tuberculosis, embB mutations were associated with MICs of > or =20 microg/ml while resistance not associated with an ERDR mutation generally resulted in MICs of < or =10 microg/ml. These data further support the notion that the emb region determines intrinsic and acquired resistance to EMB and might help in the reassessment of the current recommendations for the screening and treatment of infections with EMB-resistant M. tuberculosis and NTM.

The role of microvesicles in cancer progression and drug resistance

2013 ◽  
Vol 41 (1) ◽  
pp. 293-298 ◽  
Author(s):  
Samireh Jorfi ◽  
Jameel M. Inal
Keyword(s):  
Drug Resistance ◽  
Multidrug Resistance ◽  
Cancer Progression ◽  
Chemotherapeutic Agents ◽  
Malignant Cells ◽  
Intercellular Transport ◽  
Wide Range ◽  
Anti Cancer ◽  
Mdr Multidrug Resistance

Microvesicles are shed constitutively, or upon activation, from both normal and malignant cells. The process is dependent on an increase in cytosolic Ca2+, which activates different enzymes, resulting in depolymerization of the actin cytoskeleton and release of the vesicles. Drug resistance can be defined as the ability of cancer cells to survive exposure to a wide range of anti-cancer drugs, and anti-tumour chemotherapeutic treatments are often impaired by innate or acquired MDR (multidrug resistance). Microvesicles released upon chemotherapeutic agents prevent the drugs from reaching their targets and also mediate intercellular transport of MDR proteins.

scholarly journals Essential Role of the ESX-5 Secretion System in Outer Membrane Permeability of Pathogenic Mycobacteria

PLoS Genetics ◽  
2015 ◽  
Vol 11 (5) ◽  
pp. e1005190 ◽  
Author(s):  
Louis S. Ates ◽  
Roy Ummels ◽  
Susanna Commandeur ◽  
Robert van der Weerd ◽  
Marion Sparrius ◽  
...  
Keyword(s):  
Membrane Permeability ◽  
Outer Membrane ◽  
Essential Role ◽  
Secretion System ◽  
Outer Membrane Permeability

scholarly journals Role of β-Lactamases and Porins in Resistance to Ertapenem and Other β-Lactams in Klebsiella pneumoniae

2004 ◽  
Vol 48 (8) ◽  
pp. 3203-3206 ◽  
Author(s):  
George A. Jacoby ◽  
Debra M. Mills ◽  
Nancy Chow
Keyword(s):  
Klebsiella Pneumoniae ◽  
Outer Membrane ◽  
Type Strain ◽  
Wild Type Strain ◽  
Outer Membrane Proteins ◽  
Wild Type ◽  
Resistant Mutants ◽  
High Level ◽  
Level Resistance

ABSTRACT High-level resistance to ertapenem was produced by β-lactamases of groups 1, 2f, and 3 in a strain of Klebsiella pneumoniae deficient in Omp35 and Omp36. From a wild-type strain producing ACT-1 β-lactamase, ertapenem-resistant mutants for which the ertapenem MICs were up to 128 μg/ml and expression of outer membrane proteins was diminished could be selected.

scholarly journals Role of the AheABC Efflux Pump in Aeromonas hydrophila Intrinsic Multidrug Resistance

2008 ◽  
Vol 52 (4) ◽  
pp. 1559-1563 ◽  
Author(s):  
Mathieu Hernould ◽  
Séverine Gagné ◽  
Michel Fournier ◽  
Claudine Quentin ◽  
Corinne Arpin
Keyword(s):  
Multidrug Resistance ◽  
Aeromonas Hydrophila ◽  
Efflux Pump ◽  
Gene Inactivation ◽  
Multidrug Efflux ◽  
Intrinsic Resistance

ABSTRACT Gene inactivation and complementation experiments showed that the tripartite AheABC efflux pump of Aeromonas hydrophila extruded at least 13 substrates, including nine antibiotics. The use of phenylalanine-arginine-β-naphthylamide (PAβN) revealed an additional system(s) contributing to intrinsic resistance. This is the first analysis of the role of multidrug efflux systems in Aeromonas spp.

The MspA porin promotes growth and increases antibiotic susceptibility of both Mycobacterium bovis BCG and Mycobacterium tuberculosis

Microbiology ◽  
2004 ◽  
Vol 150 (4) ◽  
pp. 853-864 ◽  
Author(s):  
Claudia Mailaender ◽  
Norbert Reiling ◽  
Harald Engelhardt ◽  
Stefan Bossmann ◽  
Stefan Ehlers ◽  
...  
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Outer Membrane ◽  
Mycobacterium Bovis ◽  
Mycobacterium Smegmatis ◽  
Drug Susceptibility ◽  
Nucleic Acid Binding ◽  
Outer Membrane Permeability ◽  
Syto 9 ◽  
Slow Growing ◽  
Hydrophilic Solutes

Porins mediate the diffusion of hydrophilic solutes across the outer membrane of mycobacteria, but the efficiency of this pathway is very low compared to Gram-negative bacteria. To examine the importance of porins in slow-growing mycobacteria, the major porin MspA of Mycobacterium smegmatis was expressed in Mycobacterium tuberculosis and Mycobacterium bovis. Approximately 20 and 35 MspA molecules per μm2 cell wall were observed in M. tuberculosis and M. bovis BCG, respectively, by electron microscopy and quantitative immunoblot experiments. Surface accessibility of MspA in M. tuberculosis was demonstrated by flow cytometry. Glucose uptake was twofold faster, indicating that the outer membrane permeability of M. bovis BCG to small and hydrophilic solutes was increased by MspA. This significantly accelerated the growth of M. bovis BCG, identifying very slow nutrient uptake as one of the determinants of slow growth in mycobacteria. The susceptibility of both M. bovis BCG and M. tuberculosis to zwitterionic β-lactam antibiotics was substantially enhanced by MspA, decreasing the minimal inhibitory concentration up to 16-fold. Furthermore, M. tuberculosis became significantly more susceptible to isoniazid, ethambutol and streptomycin. Fluorescence with the nucleic acid binding dye SYTO 9 was 10-fold increased upon expression of mspA. These results indicated that MspA not only enhanced the efficiency of the porin pathway, but also that of pathways mediating access to large and/or hydrophobic agents. This study provides the first experimental evidence that porins are important for drug susceptibility of M. tuberculosis.

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