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New antibiotic molecules: bypassing the membrane barrier of gram negative bacteria increases the activity of peptide deformylase inhibitors.

Mamelli L, Petit S, Chevalier J, Giglione C, Lieutaud A, Meinnel T, Artaud I, Pagès JM - PLoS ONE (2009)

Bottom Line: Our results clearly show that the bacterial membrane plays a key role in modulating the antibacterial activity of PDF-Is.The bacterial susceptibility for these new antibacterial molecules can be improved by two unrelated ways in MDR strains: by collapsing the Acr efflux activity or by increasing the uptake rate through the bacterial membrane.The efficiency of the second method is associated with the nature of the compound.

View Article: PubMed Central - PubMed

Affiliation: UMR-MD1, Transporteurs Membranaires, Chimiorésistance et Drug-Design, Facultés de Médecine et de Pharmacie, IFR 88, Université de la Méditerranée, Marseille, France.

ABSTRACT

Background: Multi-drug resistant (MDR) bacteria have become a major concern in hospitals worldwide and urgently require the development of new antibacterial molecules. Peptide deformylase is an intracellular target now well-recognized for the design of new antibiotics. The bacterial susceptibility to such a cytoplasmic target primarily depends on the capacity of the compound to reach and accumulate in the cytosol.

Methodology/principal findings: To determine the respective involvement of penetration (influx) and pumping out (efflux) mechanisms to peptide deformylase inhibitors (PDF-I) activity, the potency of various series was determined using various genetic contexts (efflux overproducers or efflux-deleted strains) and membrane permeabilizers. Depending on the structure of the tested molecules, two behaviors could be observed: (i) for actinonin the first PDF-I characterized, the AcrAB efflux system was the main parameter involved in the bacterial susceptibility, and (ii), for the latest PDF-Is such as the derivatives of 2-(5-bromo-1H-indol-3-yl)-N-hydroxyacetamide, the penetration through the membrane was a important limiting step.

Conclusions/significance: Our results clearly show that the bacterial membrane plays a key role in modulating the antibacterial activity of PDF-Is. The bacterial susceptibility for these new antibacterial molecules can be improved by two unrelated ways in MDR strains: by collapsing the Acr efflux activity or by increasing the uptake rate through the bacterial membrane. The efficiency of the second method is associated with the nature of the compound.

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Related in: MedlinePlus

Activity of PDF-Is on Salmonella wild-type strain SL696 and its LPS-deficient mutants.Various isogenic strains, WT (intact LPS), Rc (truncated LPS: lipidA-KDO-hep-hep-Glc) and Re (truncated LPS: lipidA-KDO) previously described [31] were used. Act-Control, actinonin alone; Act-PMBN, actinonin + PMBN; AB47-Control, AB47 alone; AB47-PMBN, AB47 + PMBN; SM1-Control, SM1 alone; SM1-PMBN, SM1 + PMBN; SM2-Control, SM2 alone; SM2-PMBN, SM2 + PMBN. PMBN was used at 1/5 MIC. MIC values are in µg/ml.
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pone-0006443-g002: Activity of PDF-Is on Salmonella wild-type strain SL696 and its LPS-deficient mutants.Various isogenic strains, WT (intact LPS), Rc (truncated LPS: lipidA-KDO-hep-hep-Glc) and Re (truncated LPS: lipidA-KDO) previously described [31] were used. Act-Control, actinonin alone; Act-PMBN, actinonin + PMBN; AB47-Control, AB47 alone; AB47-PMBN, AB47 + PMBN; SM1-Control, SM1 alone; SM1-PMBN, SM1 + PMBN; SM2-Control, SM2 alone; SM2-PMBN, SM2 + PMBN. PMBN was used at 1/5 MIC. MIC values are in µg/ml.

Mentions: In Gram negative bacteria, the LPS constitutes the outer leaflet of outer membrane and may impair the penetration of antibacterial agents [6]. Since we have observed that the addition of membrane permeabilizer such as Pol B or PMBN, are capable to induce a serious decrease of MICs, we tested a series of Salmonella typhimurium LT2 mutants producing truncated LPS [31] to assess a putative role of LPS structure in the PDF-Is activity. These strains have been previously used as standard strains to assess the role of LPS on the level of diffusion through the outer membrane [31]. As shown in Figure 2, the actinonin activity was increased by 8 fold in LPS truncated mutants while only 2.5 fold activity increased was observed with other compounds. By contrast, in the presence of PMBN, we observed an effective restoration of susceptibility and a quite similar MIC was obtained for actinonin, AB47 and SM1. This suggests that the truncated LPS increased the bacterial susceptibility to actinonin probably by facilitating the diffusion through the LPS layer of outer membrane. Regarding the activity of the other molecules, the presence of LPS barrier is not the limiting step since PMBN addition was required to reach the same level of antibacterial activity.


New antibiotic molecules: bypassing the membrane barrier of gram negative bacteria increases the activity of peptide deformylase inhibitors.

Mamelli L, Petit S, Chevalier J, Giglione C, Lieutaud A, Meinnel T, Artaud I, Pagès JM - PLoS ONE (2009)

Activity of PDF-Is on Salmonella wild-type strain SL696 and its LPS-deficient mutants.Various isogenic strains, WT (intact LPS), Rc (truncated LPS: lipidA-KDO-hep-hep-Glc) and Re (truncated LPS: lipidA-KDO) previously described [31] were used. Act-Control, actinonin alone; Act-PMBN, actinonin + PMBN; AB47-Control, AB47 alone; AB47-PMBN, AB47 + PMBN; SM1-Control, SM1 alone; SM1-PMBN, SM1 + PMBN; SM2-Control, SM2 alone; SM2-PMBN, SM2 + PMBN. PMBN was used at 1/5 MIC. MIC values are in µg/ml.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2713832&req=5

pone-0006443-g002: Activity of PDF-Is on Salmonella wild-type strain SL696 and its LPS-deficient mutants.Various isogenic strains, WT (intact LPS), Rc (truncated LPS: lipidA-KDO-hep-hep-Glc) and Re (truncated LPS: lipidA-KDO) previously described [31] were used. Act-Control, actinonin alone; Act-PMBN, actinonin + PMBN; AB47-Control, AB47 alone; AB47-PMBN, AB47 + PMBN; SM1-Control, SM1 alone; SM1-PMBN, SM1 + PMBN; SM2-Control, SM2 alone; SM2-PMBN, SM2 + PMBN. PMBN was used at 1/5 MIC. MIC values are in µg/ml.
Mentions: In Gram negative bacteria, the LPS constitutes the outer leaflet of outer membrane and may impair the penetration of antibacterial agents [6]. Since we have observed that the addition of membrane permeabilizer such as Pol B or PMBN, are capable to induce a serious decrease of MICs, we tested a series of Salmonella typhimurium LT2 mutants producing truncated LPS [31] to assess a putative role of LPS structure in the PDF-Is activity. These strains have been previously used as standard strains to assess the role of LPS on the level of diffusion through the outer membrane [31]. As shown in Figure 2, the actinonin activity was increased by 8 fold in LPS truncated mutants while only 2.5 fold activity increased was observed with other compounds. By contrast, in the presence of PMBN, we observed an effective restoration of susceptibility and a quite similar MIC was obtained for actinonin, AB47 and SM1. This suggests that the truncated LPS increased the bacterial susceptibility to actinonin probably by facilitating the diffusion through the LPS layer of outer membrane. Regarding the activity of the other molecules, the presence of LPS barrier is not the limiting step since PMBN addition was required to reach the same level of antibacterial activity.

Bottom Line: Our results clearly show that the bacterial membrane plays a key role in modulating the antibacterial activity of PDF-Is.The bacterial susceptibility for these new antibacterial molecules can be improved by two unrelated ways in MDR strains: by collapsing the Acr efflux activity or by increasing the uptake rate through the bacterial membrane.The efficiency of the second method is associated with the nature of the compound.

View Article: PubMed Central - PubMed

Affiliation: UMR-MD1, Transporteurs Membranaires, Chimiorésistance et Drug-Design, Facultés de Médecine et de Pharmacie, IFR 88, Université de la Méditerranée, Marseille, France.

ABSTRACT

Background: Multi-drug resistant (MDR) bacteria have become a major concern in hospitals worldwide and urgently require the development of new antibacterial molecules. Peptide deformylase is an intracellular target now well-recognized for the design of new antibiotics. The bacterial susceptibility to such a cytoplasmic target primarily depends on the capacity of the compound to reach and accumulate in the cytosol.

Methodology/principal findings: To determine the respective involvement of penetration (influx) and pumping out (efflux) mechanisms to peptide deformylase inhibitors (PDF-I) activity, the potency of various series was determined using various genetic contexts (efflux overproducers or efflux-deleted strains) and membrane permeabilizers. Depending on the structure of the tested molecules, two behaviors could be observed: (i) for actinonin the first PDF-I characterized, the AcrAB efflux system was the main parameter involved in the bacterial susceptibility, and (ii), for the latest PDF-Is such as the derivatives of 2-(5-bromo-1H-indol-3-yl)-N-hydroxyacetamide, the penetration through the membrane was a important limiting step.

Conclusions/significance: Our results clearly show that the bacterial membrane plays a key role in modulating the antibacterial activity of PDF-Is. The bacterial susceptibility for these new antibacterial molecules can be improved by two unrelated ways in MDR strains: by collapsing the Acr efflux activity or by increasing the uptake rate through the bacterial membrane. The efficiency of the second method is associated with the nature of the compound.

Show MeSH
Related in: MedlinePlus