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Beta-Lactamase Repressor BlaI Modulates Staphylococcus aureus Cathelicidin Antimicrobial Peptide Resistance and Virulence.

Pence MA, Haste NM, Meharena HS, Olson J, Gallo RL, Nizet V, Kristian SA - PLoS ONE (2015)

Bottom Line: Through screening a transposon library in S. aureus Newman for susceptibility to cathelicidin antimicrobial peptide, we discovered BlaI as a novel cathelicidin resistance factor.Additionally, through integrational mutagenesis in S. aureus Newman and MRSA Sanger 252 strains, we confirmed the role of BlaI in resistance to human and murine cathelidicin and showed that it contributes to virulence in human whole blood and murine infection models.We further demonstrated that BlaI could be a target for innate immune-based antimicrobial therapies; by removing BlaI through subinhibitory concentrations of 6-aminopenicillanic acid, we were able to sensitize S. aureus to LL-37 killing.

View Article: PubMed Central - PubMed

Affiliation: Biomedical Sciences Graduate Program, University of California San Diego, La Jolla, CA, United States of America; Department of Pediatrics, School of Medicine, University of California San Diego, La Jolla, CA, United States of America.

ABSTRACT
BlaI is a repressor of BlaZ, the beta-lactamase responsible for penicillin resistance in Staphylococcus aureus. Through screening a transposon library in S. aureus Newman for susceptibility to cathelicidin antimicrobial peptide, we discovered BlaI as a novel cathelicidin resistance factor. Additionally, through integrational mutagenesis in S. aureus Newman and MRSA Sanger 252 strains, we confirmed the role of BlaI in resistance to human and murine cathelidicin and showed that it contributes to virulence in human whole blood and murine infection models. We further demonstrated that BlaI could be a target for innate immune-based antimicrobial therapies; by removing BlaI through subinhibitory concentrations of 6-aminopenicillanic acid, we were able to sensitize S. aureus to LL-37 killing.

No MeSH data available.


Related in: MedlinePlus

BlaI contributes to survival in human whole blood and virulence in vivo.(A) S. aureus Newman WT with empty complementation vector pDC123, the blaI mutant with pDC123, and the complemented blaI mutant strain were incubated for 1 h in human whole blood and CFU numbers enumerated. Samples were run in triplicate and data were plotted as the average percentage ± SD for each strain as compared to the initial inocula. A representative experiment of three performed is shown. **, p<0.01. (B) CD-1 mice (n = 8) were injected subcutaneously on one flank with S. aureus Newman WT and on the opposite flank with blaI mutant bacteria, and lesion sizes were monitored for 7 days. The lesions for each individual mouse at Day 7 are plotted and the average value indicated. Overall, the blaI mutant lesions were significantly smaller compared to the WT (p<0.04; paired t-test). (C-D) Survival of CD-1 mice (n = 10) after intraperitoneal infection with (C) 1 x 106 CFU of S. aureus Newman WT or Newman blaI mutant or (D) 6 x 108 CFU of MRSA252 or MRSA252 blaI mutant. Survival was monitored for 3 days. The survival for Newman or MRSA252 blaI mutant strain infected mice was significantly higher than for the WT infected strains as assessed by log-rank (Mantel Cox) test; the p values are shown in the respective graphs.
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pone.0136605.g003: BlaI contributes to survival in human whole blood and virulence in vivo.(A) S. aureus Newman WT with empty complementation vector pDC123, the blaI mutant with pDC123, and the complemented blaI mutant strain were incubated for 1 h in human whole blood and CFU numbers enumerated. Samples were run in triplicate and data were plotted as the average percentage ± SD for each strain as compared to the initial inocula. A representative experiment of three performed is shown. **, p<0.01. (B) CD-1 mice (n = 8) were injected subcutaneously on one flank with S. aureus Newman WT and on the opposite flank with blaI mutant bacteria, and lesion sizes were monitored for 7 days. The lesions for each individual mouse at Day 7 are plotted and the average value indicated. Overall, the blaI mutant lesions were significantly smaller compared to the WT (p<0.04; paired t-test). (C-D) Survival of CD-1 mice (n = 10) after intraperitoneal infection with (C) 1 x 106 CFU of S. aureus Newman WT or Newman blaI mutant or (D) 6 x 108 CFU of MRSA252 or MRSA252 blaI mutant. Survival was monitored for 3 days. The survival for Newman or MRSA252 blaI mutant strain infected mice was significantly higher than for the WT infected strains as assessed by log-rank (Mantel Cox) test; the p values are shown in the respective graphs.

Mentions: To establish whether the blaI-mediated cathelicidin resistance could lead to increased survival of S. aureus in the host, we performed killing assays in human whole blood and compared the virulence of WT and blaI mutant bacteria in murine abscess and septicemia models. As shown in Fig 3A, the S. aureus Newman blaI mutant was killed significantly better by human whole blood than the WT and complemented strains. In a murine skin abscess model, lesions formed by WT S. aureus Newman were significantly larger than those created by the blaI mutant (Fig 3B), and in murine sepsis models, virulence of the blaI mutant was found strongly attenuated in S. aureus Newman (Fig 3C) and moderately impaired in MRSA252 (Fig 3D). Taken together, the human whole blood ex vivo and the mouse in vivo data suggested that BlaI contributes to the pathogenic potential of S. aureus.


Beta-Lactamase Repressor BlaI Modulates Staphylococcus aureus Cathelicidin Antimicrobial Peptide Resistance and Virulence.

Pence MA, Haste NM, Meharena HS, Olson J, Gallo RL, Nizet V, Kristian SA - PLoS ONE (2015)

BlaI contributes to survival in human whole blood and virulence in vivo.(A) S. aureus Newman WT with empty complementation vector pDC123, the blaI mutant with pDC123, and the complemented blaI mutant strain were incubated for 1 h in human whole blood and CFU numbers enumerated. Samples were run in triplicate and data were plotted as the average percentage ± SD for each strain as compared to the initial inocula. A representative experiment of three performed is shown. **, p<0.01. (B) CD-1 mice (n = 8) were injected subcutaneously on one flank with S. aureus Newman WT and on the opposite flank with blaI mutant bacteria, and lesion sizes were monitored for 7 days. The lesions for each individual mouse at Day 7 are plotted and the average value indicated. Overall, the blaI mutant lesions were significantly smaller compared to the WT (p<0.04; paired t-test). (C-D) Survival of CD-1 mice (n = 10) after intraperitoneal infection with (C) 1 x 106 CFU of S. aureus Newman WT or Newman blaI mutant or (D) 6 x 108 CFU of MRSA252 or MRSA252 blaI mutant. Survival was monitored for 3 days. The survival for Newman or MRSA252 blaI mutant strain infected mice was significantly higher than for the WT infected strains as assessed by log-rank (Mantel Cox) test; the p values are shown in the respective graphs.
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Related In: Results  -  Collection

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pone.0136605.g003: BlaI contributes to survival in human whole blood and virulence in vivo.(A) S. aureus Newman WT with empty complementation vector pDC123, the blaI mutant with pDC123, and the complemented blaI mutant strain were incubated for 1 h in human whole blood and CFU numbers enumerated. Samples were run in triplicate and data were plotted as the average percentage ± SD for each strain as compared to the initial inocula. A representative experiment of three performed is shown. **, p<0.01. (B) CD-1 mice (n = 8) were injected subcutaneously on one flank with S. aureus Newman WT and on the opposite flank with blaI mutant bacteria, and lesion sizes were monitored for 7 days. The lesions for each individual mouse at Day 7 are plotted and the average value indicated. Overall, the blaI mutant lesions were significantly smaller compared to the WT (p<0.04; paired t-test). (C-D) Survival of CD-1 mice (n = 10) after intraperitoneal infection with (C) 1 x 106 CFU of S. aureus Newman WT or Newman blaI mutant or (D) 6 x 108 CFU of MRSA252 or MRSA252 blaI mutant. Survival was monitored for 3 days. The survival for Newman or MRSA252 blaI mutant strain infected mice was significantly higher than for the WT infected strains as assessed by log-rank (Mantel Cox) test; the p values are shown in the respective graphs.
Mentions: To establish whether the blaI-mediated cathelicidin resistance could lead to increased survival of S. aureus in the host, we performed killing assays in human whole blood and compared the virulence of WT and blaI mutant bacteria in murine abscess and septicemia models. As shown in Fig 3A, the S. aureus Newman blaI mutant was killed significantly better by human whole blood than the WT and complemented strains. In a murine skin abscess model, lesions formed by WT S. aureus Newman were significantly larger than those created by the blaI mutant (Fig 3B), and in murine sepsis models, virulence of the blaI mutant was found strongly attenuated in S. aureus Newman (Fig 3C) and moderately impaired in MRSA252 (Fig 3D). Taken together, the human whole blood ex vivo and the mouse in vivo data suggested that BlaI contributes to the pathogenic potential of S. aureus.

Bottom Line: Through screening a transposon library in S. aureus Newman for susceptibility to cathelicidin antimicrobial peptide, we discovered BlaI as a novel cathelicidin resistance factor.Additionally, through integrational mutagenesis in S. aureus Newman and MRSA Sanger 252 strains, we confirmed the role of BlaI in resistance to human and murine cathelidicin and showed that it contributes to virulence in human whole blood and murine infection models.We further demonstrated that BlaI could be a target for innate immune-based antimicrobial therapies; by removing BlaI through subinhibitory concentrations of 6-aminopenicillanic acid, we were able to sensitize S. aureus to LL-37 killing.

View Article: PubMed Central - PubMed

Affiliation: Biomedical Sciences Graduate Program, University of California San Diego, La Jolla, CA, United States of America; Department of Pediatrics, School of Medicine, University of California San Diego, La Jolla, CA, United States of America.

ABSTRACT
BlaI is a repressor of BlaZ, the beta-lactamase responsible for penicillin resistance in Staphylococcus aureus. Through screening a transposon library in S. aureus Newman for susceptibility to cathelicidin antimicrobial peptide, we discovered BlaI as a novel cathelicidin resistance factor. Additionally, through integrational mutagenesis in S. aureus Newman and MRSA Sanger 252 strains, we confirmed the role of BlaI in resistance to human and murine cathelidicin and showed that it contributes to virulence in human whole blood and murine infection models. We further demonstrated that BlaI could be a target for innate immune-based antimicrobial therapies; by removing BlaI through subinhibitory concentrations of 6-aminopenicillanic acid, we were able to sensitize S. aureus to LL-37 killing.

No MeSH data available.


Related in: MedlinePlus