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The introduction of diagnosis of new bacterial pathogens Ralstonia a Achromobacter isolated from patients with cystic fibrosis and determining their sensitivity to antibiotics
Michálková, Alice ; Melter, Oto (advisor) ; Bébrová, Eliška (referee)
Cystic fibrosis (mucoviscidosis) is an incurable genetic disease caused by mutations in the CFTR (Cystic Fibrosis Transmembrane Conductance Regulator Gene). The most common causes of increased mortality and morbidity of patients include bacterial respiratory infections which may occur even due to less frequent pathogens. Bacterial species of the Ralstonia and Achromobacter genera are not considered pathogenic for healthy people, but they have been established as pathogens in the sputum of patients with CF. However, due to their phenotypic similarity to other bacterial pathogens encountered in patients with CF, microbiologists often do not pay attention to them. The aim of this thesis was to propose some methods of identification of the genus Ralstonia, to determine both quantitative and qualitative susceptibility towards antibiotics, and to make a bibliographical search focused on the issue of the Achromobacter genus. Strains of Ralstonia spp. were identified using phenotypic and genotypic methods and were tested for the susceptibility towards antibiotics. The thesis also proposes a new method of genotypic indentification of R. respiraculi.
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Critical sites determining the resistance phenotype of ABC proteins from the ARE subfamily and the molecular mechanism of their function
Lenart, Jakub ; Balíková Novotná, Gabriela (advisor) ; Melter, Oto (referee) ; Branny, Pavel (referee)
Vga(A) and Msr(A) are resistance proteins belonging to the ARE subfamily of ABC -F proteins. They confer resistance to inhibitors of the peptidyltransferase center. It has been proposed that the mechanism of resistance is based on interaction with a transmembrane partner that forms the functional transporter. Their ribosomal function has been described by cryoelectron microscopy of ribosome complexes with ABCF mutants unable to hydrolyze ATP. However, the exact mechanism of resistance is not yet known. We have produced the mutant proteins combining the four amino acid residues in Vga(A) and Vga(A)LC at the linker tip, and we were the first to describe the effects of substrate specificity of the single mutants. Amino acid positions 212 and 220 are important for resistance to lincosamides and pleuromutilins, respectively, while position 219 is responsible for resistance to streptogramin A. Each amino acid property plays a critical role in conferring antibiotic specificity, as confirmed by the fact that amino acid substitution at position K218T in the Vga(A) protein causes the shift in resistance from streptogramins to lincosamides and pleuromutilins. The mechanism of resistance conferred by Vga(A) is ribosomal protection. This is supported by the fact that the rate of [3H]-lincomycin accumulation in...
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Occurrence of LA-MRSA and CA-MRSA in a Population at Higher Carriage Risk
Neradová, Kateřina ; Žemličková, Helena (advisor) ; Karpíšková, Renáta (referee) ; Melter, Oto (referee)
Occurrence of LA-MRSA and CA-MRSA in a population at higher carriage risk Bacterial resistance is one of the most serious phenomenon of modern medicine. Staphylococcus aureus is one of the bacteria in which the incidence of antibiotic resistance is a serious complication in the effective treatment of infectious diseases. Typically, methicillin- resistant Staphylococcus aureus (MRSA) occurs in a hospital settings where infectious complications appear in hospitalized patients. Community strains can be distinguished from typical nosocomial strains, which affect young people without anamnestic link to health care facilities and have different genetic characteristics. In livestock, a third distinct group of MRSA has been identified and now represents an epidemiological risk to humans. Cases of colonization or infection caused by MRSA are frequently reported in people who work with animals, including veterinary personnel. The aim of this study was to determine the prevalence of MRSA colonization among veterinary professionals. A total of 134 nasal swabs from healthy attendees of a veterinary conference held in Hradec Kralove in the Czech Republic were tested for presence of MRSA. The strains were further genotypically and phenotypically characterized. Nine isolated MRSA strains were characterized with sequence...
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Extensively resistant Acinetobacter baumannii in the Czech Republic: population genetic structure and mechanisms of resistance to carbapenems and aminoglycosides
Švandová, Ladislava ; Nemec, Alexandr (advisor) ; Melter, Oto (referee)
This study focuses on the question of the epidemiology of resistance to antibiotics in Acinetobacter baumannii, which is nowadays one of the most problematic bacterial patho- gens associated with failing antimicrobial therapy. Its aim was to define population-genetic properties, epidemiology and the nature of multidrug resistance for a sample of the current population of A. baumannii from Czechia. A total of 55 isolates were collected in eight medi- cal facilities in central Bohemia from October 2016 to May 2018. The isolates were assessed for their identity at the species, clonal and strain levels as well as resistance phenotype and genotype; they were classified into five clonal groups, each of which encompassed isolates that were likely to be epidemiologically related. The 55 isolates studied belonged, nearly exclusively, to global clone ECII, with 53 % of them forming a genetically relatively homoge- neous group characterized by extensive resistance to antibiotics (susceptible only to col- istin), the presence of genes encoding ArmA a OXA-23 (resistance to all aminoglycosides and carbapenems) and spread in all locations. The in-depth epidemiological analysis of isolates from the city of Příbram and its vicinity indicated the regional spread of two strains, one of which belonged to the...
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Molecular interactions of Staphylococcus aureus with the host
Cabrnochová, Marie ; Melter, Oto (advisor) ; Vopálenský, Václav (referee)
The aim of this thesis is to summarize S. aureus interactions with selected mechanisms of innate host immunity especially interactions with neutrophils and processes on the cell level which lead to host colonization. S. aureus surface proteins MSCRAMM interact with host cell surface proteins such as fibrinogen, keratin and thereby mediate adhesion to the host cell, which is an essential point for colonization of the host cell. The central mechanism of innate immunity against any S. aureus infection is the interaction of the pathogen with neutrophils, which produce neutrophil extracellular traps and phagocytes S. aureus cells. A crucial role in the elimination of bacterial cells in the phagosome of neutrophils is lysis by the antimicrobial peptides and degradation of bacterial biomolecules by the oxygen radicals. S. aureus defence mechanisms against action of immune system are considered to be virulence factors, due to its contribution to the establishment of the infection. These mechanisms are based on cell wall modification, inhibition of neutrophil chemotaxis, and production of enzymes that inhibit the effect of antimicrobial peptides, lysozyme, oxygen and nitrogen radicals. Expression of virulence factors of a particular S. aureus strain and host-specific risk factors can lead through successful...
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Mechanisms of bacterial persistence and clinical significance
Smělíková, Eva ; Melter, Oto (advisor) ; Pinkas, Dominik (referee)
Persistent bacteria, shortly persisters, are cells that are characterized by their tolerance to antibiotics without containing resistance genes. These are not resistant bacteria, because resistant bacteria are determined by genetic code. Persisters are indistinguishable from other antibiotic sensitive bacteria, and they are rather transient phenotypic subpopulations. Probably all types of bacteria can create a persistent stage, the ability is not species-bound and persistence has been described in a number of bacterial species. The reason for the formation of persistence may be sudden stress, then it is induced formation, or the reason may be an insurance for the future, then we call it stochastic phenotypic variability. Then a variety of phenotypes of different subpopulations within a genetically uniform population can be distinguished. They differ in growth properties and tolerance to antibiotics. Bet-hedging strategy is a hypothesis that describes persistence as insurance against the risk of external fluctuations. During stress an alarmon guanosine tetraphosphate or guanosine pentaphosphate is accumulated to alert the cell to unfavorable conditions and it initiates transition to a more tolerant state. The existence of these tolerant subpopulations is important in recurrent diseases because small...
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Lyme borreliosis diagnostics using in vitro cellular immune response testing
Prokopová, Tereza ; Drbal, Karel (advisor) ; Melter, Oto (referee)
Lyme borreliosis is a multisystemic disease affecting skin, joints, heart and central nervous system. The disease is caused by spirochetes of Borrelia burgdorferi sensu lato complex. These bacteria are spread by ticks of Ixodes genus. In 2016 there were almost 4,000 newly infected individuals reported in the Czech Republic. Contemporary serological diagnostics of Lyme borreliosis is not sensitive nor specific enough and does not even correlate with the pathology of the disease in the early or late phases. For the correct diagnosis of the disease it is necessary to detect the pathogen and its genotype. For this reason we had aimed at two goals. Through the digital droplet PCR (ddPCR) method we detected Borrelia-specific DNA and its genotype. The detection limit of borrelial DNA was set on gDNA samples isolated from the tick. Detection threshold for the initial amount of 1 ng of tick gDNA is at the range of 10-17 g of specific borrelial DNA. Borrelia spp. coinfection was detected in 5 out of 12 tested samples. The most frequent type was B. garinii which was detected in 5 samples. On the basis of published sequences for virulent factors we have designed specific primers in conserved regions of the genes flanking their variable segments to be PCR amplified. Gene variability will be monitored through...
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Molecular characterization of resistance to MLSb antibiotics in Staphylococcus aureus and SCV Staphylococcus aureus strains of cystic fibrosis patients
Vařeková, Eva ; Melter, Oto (advisor) ; Zikánová, Blanka (referee)
Cystic fibrosis (CF) is the most common autosomal recessive genetic disorder in Caucasians. Lower respiratory tract of CF patients is colonized by specific bacteria, often leading to chronic infection and lung tissue damage. In this thesis we characterized 338 isolates of S. aureus from 92 Czech CF patients isolated in 2011-2013. Using spa typing and PFGE we detected high clonal heterogenity of this collection with the exception of MRSA strains (resistant to oxacillin; 5% prevalence) which were clonally related. The prevalence of S. aureus MLSB resistance in our collection was high (69 %), which is a serious problem due to common usage of these antimicrobials in clinical practice. A half of the MLSB resistant strains lacked any known determinant of this resistance (ermA, ermC, ermT, msrA). Sequencing of the ribosomal genes revealed a high number of S. aureus strains carrying target site mutations resulting in MLSB resistance (37 %). This is new important information about the staphylococcal strains associated with chronic infections in Czech Republic. Focusing on mutability of analysed strains, we also detected several strains with point mutations or deletions in their mutator genes mutS a mutL. Hypermutability could be responsible for the high rate of ribosomal mutations and for the presence of...
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Molecular epidemiology and characteristics of bacterial pathogens on lung infection in patients with cystic fibrosis
Vošahlíková, Šárka ; Nemec, Alexandr (advisor) ; Melter, Oto (referee) ; Osička, Radim (referee)
Cystic fibrosis is the most abundant inherited autosomal recessive disease in Caucasian population. Cystic fibrosis is caused by a dysfunction of a transport channel which is responsible for the transport of chloride ions on the apical side of the plasma membrane. Despite the fact that the dysfunction of the transport channel is present in several organs, the most severely affected one is the respiratory system. Because of the ion imbalance, thick sticky mucus is produced on the surface of the airways which then prevents the removal of dust particles and bacteria. The main complications of cystic fibrosis are the bacterial infections of the respiratory system which become chronic during the patient's life and thus are the most common causes of the respiratory failure and premature death. The most important agents causing these infections are Pseudomonas aeruginosa and Burkholderia cepacia (Bcc). Infections caused by those bacteria are practically untreatable and serious complications arise from the existence of epidemic strains which can be transfered from patient to patient. Precise and fast diagnostics of pathogenic strains is a critical step to avoid spreading bacterial infections as well as strictly followed anti- epidemic strategies mainly based on isolation of cystic fibrosis patients according to...
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