Research summary
Elucidating the intrinsic resistance mechanisms that K.pneumoniae employs, and their importance in generating an AMR phenotype, is essential to developing a comprehensive and effective antimicrobial strategy. Furthermore, identifying the pathways of specific resistance mechanisms contributing to AMR, presents potential targets for inhibitory drugs in combination with existing antimicrobial giving rise to novel treatment regimes.
Current research interests
To survive in changing environments, bacteria have evolved mechanisms to adapt through the expression of appropeiate gene. Antimicrobial agent and stressor exposure of Enterobavteriacea causes the activation of the AraC/XylS type of transcriptional regulators , including RamA, RarA, MarA and SoxS. These act as global regulators to alter gene expression allowing for favourable fitness in the presence of bacteriocidal substances. Increased expression of marA, rarA, ramA, and soxS up-regulates efflux channel expression to allow detoxification of the cell. Moreover, this expression has been linked to clinically significant strains of K.pneumoniae.
Past research interests
Lay summary of thesis on CrrAB TCS in Klebsiella pneumoniae-
Bacterial infections have been a major threat to humanity for centuries. Upon the introduction of
antibiotic treatment regimes in the 20th century the threat was alleviated. In the past decade, the
extensive use of antibiotics resulted in the emergence of resistance to virtually all of them, the effect
of which will result to an exponential rise in mortality and morbidity. It is essential to characterize
the underlying mechanism of resistance to counter its effect through the development of novel
treatments. In the present research, the pathway of resistant, and secondary effects arising from its
activation, to the last resort antibiotic (colistin) were analyzed. One of the most clinically significant
bacteria, namely Klebsiella pneumoniae was used as the vector to analyze the interplay between
colistin resistant and secondary effects. It is known that regulatory proteins harboring mutations can
extensively decorate a molecule (LPS) located in the outer membrane of K.pneumoniae resulting in
colistin resistance. The major altered proteins are PhoPQ and PmrAB and the recently identified
CrrAB which is now believed to play a major role. The understudied CrrAB protein is of the same
nature as PhoPQ and PmrAB, but in a previous publication there where faint evidence for the cooccurrence of other effects arising in combination with colistin resistance in the presence of CrrAB
mutations. To investigate the nature of these effects, five distinct mutations in CrrAB were
recreated. Three of these mutations exhibited a novel effect in K.pneumoniae, the formation of an
external layer of sugars in combination with colistin resistance. This external layer, namely capsule,
is important in the protection of bacteria from multiple external stressors. These stressors include
antibiotics and functions of the immune system of humans. The formation of capsule in
K.pneumoniae expressing a mutated CrrAB protein was then attributed to the upregulation of three
proteins participating in the carbon cycle. It is not yet known if these proteins are directly or
indirectly controlled by the mutated CrrAB. Moreover, the major PhoPQ protein appears to play no
part in the formation of the outer layer but is crucial in the rise of colistin resistance. Since,
alterations in the PhoPQ pathway are the leading cause for colistin resistance it is essential to
describe its interaction with the CrrAB protein. Through deletion of the PhoPQ protein and
overproduction of the altered CrrAB protein known to cause capsule production it was found that
capsule production is solely an effect of CrrAB. On the other hand, colistin resistance was abolished
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