Studies on the antibiotic susceptibility of Escherichia coli
Date
2012-04-04
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
Antibiootikumid on ühendid, mis tugevalt pärsivad mikroobide kasvu või surmavad neid ning on seetõttu leidnud meditsiinis laialdast kasutust. Samal ajal muutub mikroobide seas järjest tavalisemaks ravimi-resistentsus, mis paljudel juhtudel piirab antibiootikumide kasutusvõimalusi ning oluliselt raskendab erinevate nakkuste ravimist. Uute antibiootikumide välja töötamine ei pruugi olla lahenduseks, kuna ajalugu on näidanud, et alati on resistentsus üsna kiiresti tekkinud. Seetõttu on otsitud alternatiivseid viise suurendamaks praeguste antibiootikumide efektiivsust. Kahte neist olen mina lähemalt käsitlenud oma doktoritöös.
Üheks võimaluseks on lisaks antibiootikumi otsesele sihtmärgile mõjutada ka mõnda muud protsessi. Selline lähenemine võib olla efektiivne, kuna antibiootikumidele reageerimisega on bakteris seotud mitmed erinevad protsessid. Üheks selliseks on osutunud trans-translatsioon, mida viib läbi tmRNA ning mis seisneb mRNA-le kinnijäänud ribosoomide vabastamises. Varem on tmRNA-d kodeeriva geeni eemaldamise mõju vaadeldud ja nähtud ainult valgusünteesi inhibeerivate antibiootikumide korral. Oma töös näitasin, et tmRNA ja trans-translatsioon võiksid olla sihtmärk, et võimendada ka mitmete rakukesta sünteesi inhibiitorite bakterite kasvu pärssivat toimet ning tugevdada valgusünteesi inhibiitorite aminoglükosiidide baktereid tapvat mõju.
Teine võimalus oleks hävitada persistoreid, väikest hulka antibiootikumidele tundetuid baktereid, mida peetakse krooniliste ning mõningate pikaajalist antibiootikumiravi vajavate infektsioonide põhjuseks. Persistorid on geneetiliselt identsed ülejäänud rakkudega, mis tähendab, et tegu ei ole resistentsusega. Persistorite olemus on siiani üsna segane ning seetõttu keskendus teine osa minu doktoritööst persistorite täpsemale kirjeldamisele. Esiteks arendasin ma koostöös kolleegidega välja uudse metoodika persistorite tekke paremaks jälgimiseks ning järgnevalt leidsin, et persistorite hulk ja nende teke sõltub väga oluliselt eksperimentaalsetest tingimustest, millele ei ole varem olulist tähelepanu pööratud. Saadud tulemused võiksid kiirendada edasisi peristoreid, kui meditsiiniliselt olulist nähtust, käsitlevaid uuringuid.
Antibiotics are compounds which inhibit microbial growth or kill them and therefore are actively used in medicine. At the same time the widespread antibiotic resistance is decreasing the effectiveness of current drugs and raises the rate of treatment failure. Development of new drugs has not been proved to be successful solution as the resistance has eventually emerged in all cases. Therefore also alternative approaches how to increase the efficiency of existing drugs have been looked for. Two of them have gained attention in my thesis. As various physiological processes are involved in responses to antibiotics, one strategy to potentiate existing drugs is to co-inhibit some other process leading to higher sensitivity to the drugs. One such target is tmRNA that is conducting process called trans-translation which releases ribosomes stalled on mRNAs. Previously it has been demonstrated that tmRNA deletion results higher sensitivity to inhibitors for protein synthesis as compared to wild-type strains. I showed that tmRNA is also a potential target to potentiate the ability of some cell wall synthesis inhibitors to inhibit growth of E. coli and to enhance the killing activity of protein synthesis inhibiting aminoglycosides. Another approach to increase the efficiency of existing drugs could be eradication of persisters, which are a small subpopulation of cells insensitive to most of antibiotics. Persisters are thought to be responsible for chronic and long-term infections. It is important to note that persisters are not an indication of resistance as they are genetically identical to the rest of the cells. As the essence of persisters is not clear, the second part of my thesis concentrates on describing of persisters in more detail. In cooperation with colleagues we developed a novel methodology to follow the formation of persisters. Subsequently, I found that the formation of persisters is highly dependent of experimental setup, which is has not gained previously significant attention. The results obtained might help to speed up the medically important field of persistence.
Antibiotics are compounds which inhibit microbial growth or kill them and therefore are actively used in medicine. At the same time the widespread antibiotic resistance is decreasing the effectiveness of current drugs and raises the rate of treatment failure. Development of new drugs has not been proved to be successful solution as the resistance has eventually emerged in all cases. Therefore also alternative approaches how to increase the efficiency of existing drugs have been looked for. Two of them have gained attention in my thesis. As various physiological processes are involved in responses to antibiotics, one strategy to potentiate existing drugs is to co-inhibit some other process leading to higher sensitivity to the drugs. One such target is tmRNA that is conducting process called trans-translation which releases ribosomes stalled on mRNAs. Previously it has been demonstrated that tmRNA deletion results higher sensitivity to inhibitors for protein synthesis as compared to wild-type strains. I showed that tmRNA is also a potential target to potentiate the ability of some cell wall synthesis inhibitors to inhibit growth of E. coli and to enhance the killing activity of protein synthesis inhibiting aminoglycosides. Another approach to increase the efficiency of existing drugs could be eradication of persisters, which are a small subpopulation of cells insensitive to most of antibiotics. Persisters are thought to be responsible for chronic and long-term infections. It is important to note that persisters are not an indication of resistance as they are genetically identical to the rest of the cells. As the essence of persisters is not clear, the second part of my thesis concentrates on describing of persisters in more detail. In cooperation with colleagues we developed a novel methodology to follow the formation of persisters. Subsequently, I found that the formation of persisters is highly dependent of experimental setup, which is has not gained previously significant attention. The results obtained might help to speed up the medically important field of persistence.
Description
Väitekirja elektrooniline versioon ei sisalda publikatsioone.
Keywords
Escherichia coli, antibiootikumid, ravimiresistentsus, valgusüntees, inhibiitorid, Escherichia coli, antibiotics, drug resistance, protein synthesis, inhibitors