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NOORA AL ZAROONI
Department of Microbiology
College of Medicine and Health Sciences
Title
Virulence Factors, Clonality, Antibiotic And Disinfectant Resistance Of Enterobacteriaceae Isolated in the
Arabian Peninsula
Faculty Advisor
Prof. Tibor Pál
Defense Date
04 April 2016
Abstract
The emergence and rapid spread of multi-drug resistant (MDR) Enterobacteriaceae is one of the most challenging
problem currently we face. Locally, no details on the strains causing outbreaks are available and we still do not
understand what makes certain clones capable of spreading widely while others are confined to sporadic cases,
only. Our aim was to characterize the virulence factors, antibiotic and disinfectant susceptibilities of local clonal and
sporadic Escherichia coli and Klebsiella pneumoniae strains and to reveal which particular feature might be responsible
for the outbreak potential of clonal isolates. E. coli and K. pneumoniae strains collected from countries of the Arabian
Peninsula were subjected to genotyping by PCR targeting a broad spectrum of virulence and antibiotic resistance
genes, to antibiotic susceptibility tests, serum resistance and biofilm formation assays and to molecular typing by
macro-restriction analysis and by multilocus sequence typing. We established that among E. coli blood stream
isolates the rate of strains expressing R4 core type is currently much higher than seen before and it was due to a few
multi-resistant clones recently emerged. We have also shown that the majority of local K. pneumoniae clones did not
possess considerably more virulent-related features than sporadic isolates. Rather, they were clearly distinguished
from the latter group by their broader spectrum of resistance to non-ß-lactam antibiotics well substantiated by the
increased carriage of the respective resistance genes. Resistance to disinfectants were more common among K.
pneumoniae strains non-susceptible to carbapenems than among the antibiotic sensitive isolates. We speculate
that this may also increase the outbreak potential of the strains. Finally, we have shown that a considerable part of
local carbapenem resistant K. pneumoniae strains are still susceptible to fosfomycin, although the rate of resistance,
particularly among blood stream isolates, is already alarming. Our data show that it is particularly the increased
resistance rather than any specific virulence-related feature that makes strains spread as clones. A well-organized
surveillance system based on molecular typing is needed in the country, to follow the characteristics of the spread of
multidrug resistance organisms in the region.
Dissertation