The Major Cold Inducible Gene of S. aureus, cspB, modulates susceptibility to antimicrobials Open Access

Abstract

The Major Cold Inducible Gene of S. aureus, cspB,
Modulates Susceptibility to Antimicrobials
By Brea Duval
Staphylococcus aureus is a major human pathogen causing a varied group of
diseases ranging in severity from mild skin to invasive, often deadly infections that can
impact the function of multiple organs and systems. While part of the normal human
flora, problems with antibiotic resistant strains have been ever increasing and the arsenal
of effective drugs available for treatment has been steadily dwindling. S. aureus is able to
cause such diverse diseases because of its ability to survive a variety of environments,
which would subject the bacteria to changes in temperature, pH, ionic strength and
mediators of innate immunity. Previous work from our laboratory defined the role of the
major cold shock protein of S. aureus, CspA, in the bacteria's response to cold stress as
well as its role in resistance to antimicrobial peptides. Two other members of the cspA
family cold shock protein-encoding genes, cspB and cspC, were found in the genome of
strain COL, a methicillin resistant clinical isolate.
Previous microarray analysis identified cspB as the major cold-inducible gene in
S. aureus. Therefore, the aim of this work was to define the role of cspB found in strain
COL in antibiotic resistance and cold stress. In addition to having an important role under
cold-shock conditions, CspB seems to have important functions under normal (37 °C)
growth conditions. We found that insertional inactivation of cspB resulted in dramatic
phenotypic changes that resembled those previously ascribed to staphylococcal small
colony variants (SCVs). These changes include loss of pigment, slow growth, and an
increase in resistance to several clinically relevant antimicrobials. Interestingly, while
complementation of a cspB insertional mutant showed restoration of all of these
phenotypic changes to wild type levels, the two notable exceptions were lack of complete
complementation of biofilm forming capacity and loss of resistance to methicillin. This
loss of methicillin resistance was shown to be due to loss of the type I SCC mec cassette.
Taken together, this data suggests that cspB plays important role in many aspects of
staphylococcal pathogenesis including suggesting a novel role for this stress response
protein in involvement in the SCV phenotype.

Table of Contents

Table of Contents

Abstract

Dedication

Acknowledgements

List of Tables and Figures

Chapter 1: Introduction………………………………………………………………1

Chapter 2: Altered Growth, Pigmentation and Antimicrobial Susceptibility Properties
of Staphylococcus aureus Due to Loss of the Major Cold Shock Gene cspB……….100

Chapter 3: Unpublished Observations……………………………………………….137

Chapter 4: Final Discussion…...……………………………………………………..155

List of Figures and Tables

Chapter 1
Figure 1: Evasion of Host Innate Defenses by S. aureus
Figure 2: Diagram of the Five Major Scc mec Types

Chapter 2
Table 1: Bacterial Strains and Plasmids
Table 2: Oligonucleotides used
Table 3: MIC Data Summary
Table 4: Influence of growth and assay temperature on the antibiotic
of S. aureus
Figure 1: Comparative Densitometry of Selected Transcripts
Figure 2: Pigment Production by Staphylococcal Strains
Figure 3: Growth Differences Between Staphylococcal Strains
Figure 4: Disk Diffusion Analysis of Selected Antimicrobials
Figure 5: Loss of the Type I SCC mec cassette in Strains BD1 and BD2

Chapter 3
Figure 1: SEM Analysis of Staphylococcal Strains
Figure 2: Microarray Analysis of Strain BD1 vs. Strain COL
Figure 3: Proposed model for CspB dependent regulation of the ica locus by TcaR

About this Dissertation

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School	Laney Graduate School
Department	Biological and Biomedical Sciences
Subfield / Discipline	Microbiology & Molecular Genetics
Degree	PhD
Submission	Dissertation
Language	English
Research Field	Biology, Microbiology
Keyword	Antibiotic Resistance MRSA
Committee Chair / Thesis Advisor	Shafer, William M, Emory University
Committee Members	Weiss, David S, Emory University Rather, Phil N, Emory University Moran Jr., Charles, Emory University Tzeng, Yih-Ling, Emory University

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