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Influence of Staphylococcus aureus Quorum sensing system to antibiotic tolerance
Šaňková, Michaela ; Lichá, Irena (advisor) ; Buriánková, Karolina (referee)
Staphylococcus aureus is a gram-positive opportunistic pathogenic bacterium that causes a range of chronic infections especially to weakened individuals. Recently, the most serious problem in clinical medicine has been infections caused by so-called persisters. They form a subpopulation of cells that, thanks to adaptations to stressful conditions, are able to withstand lethal doses of antibiotics and then cause an infection again. Agr system, which is responsible for the mechanism of quorum-sensing, plays the main role in switching between the active virulent form and the persistent form associated with biofilm formation. During chronic infections, adaptive mutations accumulate in this Agr system and affect the ability to persist. For the purpose of this thesis, clinical isolates were obtained from patients diagnosed with cystic fibrosis in chronological order within the first three years of their lives. The aim of this thesis was to confirm the influence of adaptive mutations on the persistence ability of clinical isolates and also to observe how the membrane potential and metabolic activity change depending on the on the action of selected antibiotics. Additional aim was to create a deletion of the response regulator AgrA gene using the CRISPR/Cas9 system. In order to characterize the persistence...
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Study of persistence mechanisms to antibiotics in Staphylococcus aureus
Balgová, Tamara ; Lichá, Irena (advisor) ; Ulrych, Aleš (referee)
In clinical practice, infections caused by persistent bacteria have become a worldwide problem. We are talking about a subpopulation of cells that are able to withstand lethal doses of antibiotics and after their elimination are capable of resuscitation and re-induction of the disease. The opportunistic pathogen Staphylococcus aureus is one of this bacteria and causes various serious chronic infections. During the long-term persistence in patients, persistent bacteria acquire adaptive mutations. The aim of this diploma thesis was to monitor the degree of persistence in selected clinical isolates, and at the same time to demonstrate the effect of adaptive mutations on the degree of persistence as well as to molecularly characterize the persistent state by gene expression. I had chronological isolates of S. aureus at my disposal, the initial one being the primoisolate, an isolate taken at the diagnostics of cystic fibrosis before the start of antibiotic treatment. Another was taken at a distance of one year and the last with a half-year interval from the previous one. Following whole genome sequencing, genes in which adaptive mutations occurred were identified. The first method determines the degree of persistence by calculating CFU (Colony Forming Units) after antibiotic treatment. I found that this...
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Changes in the ability to form persisters in chronological isolates of Staphylococcus aureus
Kotková, Hana ; Lichá, Irena (advisor) ; Tkadlec, Jan (referee)
In immunodeficient patients, for example with cystic fibrosis (CF), the opportunistic pathogen Staphylococcus aureus causes chronic infections of respiratory tract that are treated with antibiotics (ATB) in the long term. However, exposure to antibiotics can lead to persistence, thereby result a recurrence of infection. The aim of this work was to examine in selected pairs of S. aureus chronological isolates from the respiratory tract of CF patients how their ability to form persisters is changing in time. I have found that the ability to persist within the clonal pair does not change significantly after two years of survival in the host, and that the ability to persist depends on the adaptative mutations of the isolates. Persister formation may depend on mutations in operon of the alternative sigma B factor (sigB) and the major virulence gene regulator (agr). By dual staining with DioC2(3) and To-pro-3, I was able to determine the changes in membrane potential and membrane permeability during the killing curve with ATBs. The distribution into subpopulations according to these parameters depends primarily on the antibiotic used. I conclude that various antibiotics can induce different mechanisms causing a persistent state. Futhermore, I have constructed plasmids with a labeled promoter to determine...
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Regulation of virulence factors of Staphylococcus aureus
Šaňková, Michaela ; Lichá, Irena (advisor) ; Černý, Ondřej (referee)
Staphylococcus aureus is a gram-positive pathogenic bacterium that regulates virulence factors production in response to changing environmental conditions. S. aureus cells evolved a complex regulatory network, including a number of regulatory proteins, transcriptional factors and two- component systems. One of the most important S. aureus regulatory systems is the Agr system (Accessory gene regulator) that perceives its own population density by sensing a "quorum-sensing" signal in a form of autoinducing peptid (AIP). Agr system encodes a global regulatory RNAIII that regulates the expression of target virulence factors, which includes surface proteins as well as extracellular toxins and enzymes. The family of global protein regulators SarA and transcriptional sigma factor B also play a significant role in the regulation of S. aureus virulence. The production of virulence factors is also regulated in response to specific signals from extracellular environment by two- component-systems, which includes the regulator of exoprotein production SaeRS, the regulator of autolysis ArlRS and the regulator of respiratory response SrrAB. Key words: Staphylococcus aureus, virulence factors, Agr, quorum-sensing, RNAIII, SarA, SigB
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Changes in the ability to form persisters in chronological isolates of Staphylococcus aureus
Kotková, Hana ; Lichá, Irena (advisor) ; Tkadlec, Jan (referee)
In immunodeficient patients, for example with cystic fibrosis (CF), the opportunistic pathogen Staphylococcus aureus causes chronic infections of respiratory tract that are treated with antibiotics (ATB) in the long term. However, exposure to antibiotics can lead to persistence, thereby result a recurrence of infection. The aim of this work was to examine in selected pairs of S. aureus chronological isolates from the respiratory tract of CF patients how their ability to form persisters is changing in time. I have found that the ability to persist within the clonal pair does not change significantly after two years of survival in the host, and that the ability to persist depends on the adaptative mutations of the isolates. Persister formation may depend on mutations in operon of the alternative sigma B factor (sigB) and the major virulence gene regulator (agr). By dual staining with DioC2(3) and To-pro-3, I was able to determine the changes in membrane potential and membrane permeability during the killing curve with ATBs. The distribution into subpopulations according to these parameters depends primarily on the antibiotic used. I conclude that various antibiotics can induce different mechanisms causing a persistent state. Futhermore, I have constructed plasmids with a labeled promoter to determine...
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Study of persistence phenomenon at Staphylococcus aureus
Kubištová, Lucie ; Lichá, Irena (advisor) ; Melter, Oto (referee)
Staphylococcus aureus is human pathogen and is causative factor of many diseases with different character, from light infections of the skin to life-threatening sepsis. S. aureus often colonizes cystic fibrosis patient's lungs and causes long-standing pneumonia, which can cause death in these patients. Infection caused by S. aureus are, as most of the infections, treated with antibiotics. Failure in treatment is caused because of presence of resistant strains. It was shown, that treatment failure can be caused by different type of the antibiotic tolerance - by the persistence. Persisters are phenotypic variants of isogenic bacterial population, that is unaffected by antibiotic treatment even though they don't have genetics determinants of the resistance. The phenomenon of the persistence in bacteria is still relatively poorly understood. The aim of my thesis was to contribute to the characterization of the persistence in S. aureus. We have optimized a method for rapid identification of persisters' amount in the bacterial population after treatment with antibiotics using the method of measuring the killing curves. We have found out, that exposure to osmotic stress causes increase in number of persistence in the bacterial population by 1 - 2,5 order. Using quantitative PCR method we have analyzed the...
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