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Antibacterial Characterization of Novel Synthetic Thiazole Compounds against Methicillin-Resistant Staphylococcus pseudintermedius.

Mohammad H, Reddy PV, Monteleone D, Mayhoub AS, Cushman M, Hammac GK, Seleem MN - PLoS ONE (2015)

Bottom Line: Metabolic stability analysis with dog liver microsomes revealed compound 3 exhibited an improved physicochemical profile compared to the lead compound.In addition to this, all six thiazole compounds possessed a long post-antibiotic effect (at least 8 hours) against MRSP.Collectively the present study demonstrates these synthetic thiazole compounds possess potent antibacterial activity against both MSSP and MRSP and warrant further investigation into their use as novel antimicrobial agents.

View Article: PubMed Central - PubMed

Affiliation: Department of Comparative Pathobiology, Purdue University College of Veterinary Medicine, West Lafayette, Indiana, United States of America.

ABSTRACT
Staphylococcus pseudintermedius is a commensal organism of companion animals that is a significant source of opportunistic infections in dogs. With the emergence of clinical isolates of S. pseudintermedius (chiefly methicillin-resistant S. pseudintermedius (MRSP)) exhibiting increased resistance to nearly all antibiotic classes, new antimicrobials and therapeutic strategies are urgently needed. Thiazole compounds have been previously shown to possess potent antibacterial activity against multidrug-resistant strains of Staphylococcus aureus of human and animal concern. Given the genetic similarity between S. aureus and S. pseudintermedius, this study explores the potential use of thiazole compounds as novel antibacterial agents against methicillin-sensitive S. pseudintermedius (MSSP) and MRSP. A broth microdilution assay confirmed these compounds exhibit potent bactericidal activity (at sub-microgram/mL concentrations) against both MSSA and MRSP clinical isolates while the MTS assay confirmed three compounds (at 10 μg/mL) were not toxic to mammalian cells. A time-kill assay revealed two derivatives rapidly kill MRSP within two hours. However, this rapid bactericidal activity was not due to disruption of the bacterial cell membrane indicating an alternative mechanism of action for these compounds against MRSP. A multi-step resistance selection analysis revealed compounds 4 and 5 exhibited a modest (two-fold) shift in activity over ten passages. Furthermore, all six compounds (at a subinihibitory concentration) demonstrated the ability to re-sensitize MRSP to oxacillin, indicating these compounds have potential use for extending the therapeutic utility of β-lactam antibiotics against MRSP. Metabolic stability analysis with dog liver microsomes revealed compound 3 exhibited an improved physicochemical profile compared to the lead compound. In addition to this, all six thiazole compounds possessed a long post-antibiotic effect (at least 8 hours) against MRSP. Collectively the present study demonstrates these synthetic thiazole compounds possess potent antibacterial activity against both MSSP and MRSP and warrant further investigation into their use as novel antimicrobial agents.

No MeSH data available.


Related in: MedlinePlus

Cell leakage analysis of compound 2, vancomycin, and lysostaphin against methicillin-resistant Staphylococcus pseudintermedius SP3.Untreated cells represent the negative control while lysostaphin (in 50 mM Tris-HCl, pH 8.00) served as the positive control. The figure represents the ratio of the average absorbance value obtained for each treatment against the average absorbance value obtained for the positive control (at both 260 and 280 nm). The error bars represent standard deviation values of two experiments where triplicate samples were used for each treatment option. A one-way ANOVA, with post hoc Tukey's multiple comparisons test, P ≤ 0.05, demonstrated no statistical difference between the values obtained for compound 2 and vancomycin relative to the untreated cells but significant difference (denoted by the asterisks) in the absorbance values obtained for lysostaphin as compared to both untreated cells and compound 2.
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pone.0130385.g003: Cell leakage analysis of compound 2, vancomycin, and lysostaphin against methicillin-resistant Staphylococcus pseudintermedius SP3.Untreated cells represent the negative control while lysostaphin (in 50 mM Tris-HCl, pH 8.00) served as the positive control. The figure represents the ratio of the average absorbance value obtained for each treatment against the average absorbance value obtained for the positive control (at both 260 and 280 nm). The error bars represent standard deviation values of two experiments where triplicate samples were used for each treatment option. A one-way ANOVA, with post hoc Tukey's multiple comparisons test, P ≤ 0.05, demonstrated no statistical difference between the values obtained for compound 2 and vancomycin relative to the untreated cells but significant difference (denoted by the asterisks) in the absorbance values obtained for lysostaphin as compared to both untreated cells and compound 2.

Mentions: Disruption of the physical integrity of the bacterial cell membrane (such as formation of pores in the membrane) has been associated with antimicrobials that exhibit rapid bactericidal activity. To assess if the thiazole compounds’ mode of action is disruption of the integrity of the MRSP cell membrane, the leakage of intracellular contents at 260 and 280 nm was analyzed after exposure of bacterial cells to a high concentration of compound 2 (4 × MIC) for 30 minutes. Fig 3 demonstrates that the thiazole compounds do not match the action of lysostaphin (a known membrane-disrupting agent). Less than 20% of the intracellular content (at 260 nm) is released after treatment with the thiazole compound as compared to cells treated with lysostaphin. This result confirms that the thiazole compounds do not act in a manner that involves disruption of the physical integrity of the MRSP cell membrane.


Antibacterial Characterization of Novel Synthetic Thiazole Compounds against Methicillin-Resistant Staphylococcus pseudintermedius.

Mohammad H, Reddy PV, Monteleone D, Mayhoub AS, Cushman M, Hammac GK, Seleem MN - PLoS ONE (2015)

Cell leakage analysis of compound 2, vancomycin, and lysostaphin against methicillin-resistant Staphylococcus pseudintermedius SP3.Untreated cells represent the negative control while lysostaphin (in 50 mM Tris-HCl, pH 8.00) served as the positive control. The figure represents the ratio of the average absorbance value obtained for each treatment against the average absorbance value obtained for the positive control (at both 260 and 280 nm). The error bars represent standard deviation values of two experiments where triplicate samples were used for each treatment option. A one-way ANOVA, with post hoc Tukey's multiple comparisons test, P ≤ 0.05, demonstrated no statistical difference between the values obtained for compound 2 and vancomycin relative to the untreated cells but significant difference (denoted by the asterisks) in the absorbance values obtained for lysostaphin as compared to both untreated cells and compound 2.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4472782&req=5

pone.0130385.g003: Cell leakage analysis of compound 2, vancomycin, and lysostaphin against methicillin-resistant Staphylococcus pseudintermedius SP3.Untreated cells represent the negative control while lysostaphin (in 50 mM Tris-HCl, pH 8.00) served as the positive control. The figure represents the ratio of the average absorbance value obtained for each treatment against the average absorbance value obtained for the positive control (at both 260 and 280 nm). The error bars represent standard deviation values of two experiments where triplicate samples were used for each treatment option. A one-way ANOVA, with post hoc Tukey's multiple comparisons test, P ≤ 0.05, demonstrated no statistical difference between the values obtained for compound 2 and vancomycin relative to the untreated cells but significant difference (denoted by the asterisks) in the absorbance values obtained for lysostaphin as compared to both untreated cells and compound 2.
Mentions: Disruption of the physical integrity of the bacterial cell membrane (such as formation of pores in the membrane) has been associated with antimicrobials that exhibit rapid bactericidal activity. To assess if the thiazole compounds’ mode of action is disruption of the integrity of the MRSP cell membrane, the leakage of intracellular contents at 260 and 280 nm was analyzed after exposure of bacterial cells to a high concentration of compound 2 (4 × MIC) for 30 minutes. Fig 3 demonstrates that the thiazole compounds do not match the action of lysostaphin (a known membrane-disrupting agent). Less than 20% of the intracellular content (at 260 nm) is released after treatment with the thiazole compound as compared to cells treated with lysostaphin. This result confirms that the thiazole compounds do not act in a manner that involves disruption of the physical integrity of the MRSP cell membrane.

Bottom Line: Metabolic stability analysis with dog liver microsomes revealed compound 3 exhibited an improved physicochemical profile compared to the lead compound.In addition to this, all six thiazole compounds possessed a long post-antibiotic effect (at least 8 hours) against MRSP.Collectively the present study demonstrates these synthetic thiazole compounds possess potent antibacterial activity against both MSSP and MRSP and warrant further investigation into their use as novel antimicrobial agents.

View Article: PubMed Central - PubMed

Affiliation: Department of Comparative Pathobiology, Purdue University College of Veterinary Medicine, West Lafayette, Indiana, United States of America.

ABSTRACT
Staphylococcus pseudintermedius is a commensal organism of companion animals that is a significant source of opportunistic infections in dogs. With the emergence of clinical isolates of S. pseudintermedius (chiefly methicillin-resistant S. pseudintermedius (MRSP)) exhibiting increased resistance to nearly all antibiotic classes, new antimicrobials and therapeutic strategies are urgently needed. Thiazole compounds have been previously shown to possess potent antibacterial activity against multidrug-resistant strains of Staphylococcus aureus of human and animal concern. Given the genetic similarity between S. aureus and S. pseudintermedius, this study explores the potential use of thiazole compounds as novel antibacterial agents against methicillin-sensitive S. pseudintermedius (MSSP) and MRSP. A broth microdilution assay confirmed these compounds exhibit potent bactericidal activity (at sub-microgram/mL concentrations) against both MSSA and MRSP clinical isolates while the MTS assay confirmed three compounds (at 10 μg/mL) were not toxic to mammalian cells. A time-kill assay revealed two derivatives rapidly kill MRSP within two hours. However, this rapid bactericidal activity was not due to disruption of the bacterial cell membrane indicating an alternative mechanism of action for these compounds against MRSP. A multi-step resistance selection analysis revealed compounds 4 and 5 exhibited a modest (two-fold) shift in activity over ten passages. Furthermore, all six compounds (at a subinihibitory concentration) demonstrated the ability to re-sensitize MRSP to oxacillin, indicating these compounds have potential use for extending the therapeutic utility of β-lactam antibiotics against MRSP. Metabolic stability analysis with dog liver microsomes revealed compound 3 exhibited an improved physicochemical profile compared to the lead compound. In addition to this, all six thiazole compounds possessed a long post-antibiotic effect (at least 8 hours) against MRSP. Collectively the present study demonstrates these synthetic thiazole compounds possess potent antibacterial activity against both MSSP and MRSP and warrant further investigation into their use as novel antimicrobial agents.

No MeSH data available.


Related in: MedlinePlus