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Previous issue date: 2018-03-06 / Klebsiella pneumoniae is one of the main bacterial agents that may cause
infections related to health care assistance. K. pneumoniae frequently carries
the resistance gene K. pneumoniae carbapenemase (KPC). Currently,
tigecycline can be considered one of the last therapeutic options for KPC, but
reports of tigecycline-resistant KPC isolates are on the rise, being indicated as
most common mechanism the increased AcrAB-TolC efflux pump system
expression. However, molecular tigecycline resistance mechanisms associated
to AcrAB-TolC still remains obscure. Thus, the main goal of this study was to
verify if tigecycline resistance can be related to the presence of mutations in the
regulatory genes of AcrAB-TolC, AcrR and RamR. Therefore, 32 K.
pneumoniae isolates were used, identification and antibiogram performed using
Vitek 2 systems. The minimum inhibitory concentrations were confirmed using
E-test. Primers were designed in order to verify mutations within AcrR and
RamR genes. PCR analysis showed that the mutations found within these
genes were transversions (94% for AcrR and 90% for RamR) and transitions
(6% for AcrR and 10% for RamR). Nevertheless among the mutations, no
distinction between tigecycline susceptible and resistant isolates was found.
Some of the transversions caused change in the amino acid encoding 6 in AcrR
and 15 in RamR. Presence of these types of mutations evaluation can be seen
as the first bacterial resistance study step, as it may be caused by oxidative
damage for bacterial DNA, frequently caused by antibiotic selective pressure.
Tigecycline resistance found in this study`s clinical isolates may be associated
to alterations in another genes that can trigger mechanisms associated to this
antibiotic. / Klebsiella pneumoniae consiste em um dos principais agentes bacterianos
causadores de infec????es relacionadas ?? assist??ncia ?? sa??de (IRAS). K.
pneumoniae carrega frequentemente o gene de resist??ncia K. pneumoniae
carbapenemase (KPC). Atualmente, a tigeciclina pode ser considerada uma
das ??ltimas op????es terap??uticas para KPC, mas os relatos de isolados de KPC
resistentes a tigecilina est??o em ascens??o, sendo a hiperexpress??o da bomba
de efluxo AcrAB-TolC indicado como mecanismo mais comum. No entanto, os
mecanismos moleculares de resist??ncia ?? tigeciclina associada ao AcrAB-TolC
permanecem obscuros. Desta forma o objetivo deste trabalho foi verificar se a
resist??ncia a tigeciclina pode estar relacionada ?? presen??a de muta????es nos
genes ArcR e RamR, reguladores de AcrAB-TolC. Para tanto, 32 isolados de K.
pneumoniae foram utilizados, sendo a identifica????o e o antibiograma feitos
utilizando o sistema Vitek 2. A confirma????o das concentra????es inibit??rias
m??nimas (CIMs) foram realizadas por E-test. Iniciadores foram desenhados
para verifica????o de muta????es nos genes (AcrR e RamR). As an??lises por PCR
mostraram que as muta????es encontradas nos genes AcrR e RamR foram
substitui????es por transvers??o (94% e 90% para AcrR e RamR respectivamente)
e transi????o (6% e 10% para AcrR e RamR respectivamente), por??m n??o foi
identificada distin????o da presen??a de muta????es entre isolados sens??veis e
resistentes a tigeciclina. Algumas tranvers??es ocasionaram mudan??a na
codifica????o do amino??cido, sendo 6 em AcrR e 15 em RamR. A avalia????o da
presen??a desses tipos de muta????es consiste em um primeiro passo para o
estudo da resist??ncia bacteriana, j?? que pode ser causada por dano oxidativo
ao DNA bacteriano, frequentemente ocasionado por press??o seletiva dos
antibi??ticos. A resist??ncia a tigeciclina encontrada nos isolados cl??nicos do
presente estudo, provavelmente pode estar associada a altera????es em outros
genes desencadeadores de mecanismos de resist??ncia a tigeciclina.
| Identifer | oai:union.ndltd.org:IBICT/oai:bdtd.ucb.br:tede/2389 |
| Date | 06 March 2018 |
| Creators | Figueiredo, Fernanda Nomiyama |
| Contributors | Franco, Oct??vio Luiz, Silva, Osmar Nascimento |
| Publisher | Universidade Cat??lica de Bras??lia, Programa Strictu Sensu em Ci??ncias Gen??micas e Biotecnologia, UCB, Brasil, Escola de Sa??de e Medicina |
| Source Sets | IBICT Brazilian ETDs |
| Language | Portuguese |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, info:eu-repo/semantics/masterThesis |
| Format | application/pdf |
| Source | reponame:Biblioteca Digital de Teses e Dissertações da UCB, instname:Universidade Católica de Brasília, instacron:UCB |
| Rights | info:eu-repo/semantics/openAccess |
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