Carbapenem-resistant non-fermenting Gram-negative bacteria

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ΠΜΣ Μικροβιακή Βιοτεχνολογία
Library of the School of Science
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Λιακόπουλος Απόστολος
Supervisors info:
Καθηγήτρια Αμαλία Δ. Καραγκούνη-Κύρτσου (επιβλέπουσα), Αναπλ. Καθηγητής Γεώργιος Διαλλινάς, Επίκ. Καθηγητής Δημήτριος Χατζηνικολάου
Original Title:
Αρνητικά στις καρβαπενέμες αζυμωτικά Gram αρνητικά βακτήρια
Translated title:
Carbapenem-resistant non-fermenting Gram-negative bacteria
Over the past decade, non-fermenting Gram-negative bacteria have emerged as
important opportunistic pathogens in the increasing population of patients who
are immunocompromised by their disease or medical treatment. These bacteria are
assisted by their ubiquitous distribution in the environment and have a
propensity for multiple, intrinsic or acquired drug resistance. The infections
that they cause now pose significant problems in terms of treatment and
infection control, whilst the commonly observed rapid emergence of bacterial
resistance to new antimicrobial compounds,such as carbapenems, raises concerns
regarding the clinical lifespan of these agents. Two-hundred and twenty-seven
carbapenem-resistantnon-fermenting Gram-negative bacteria isolates were
collected consecutively in2011 from inpatients treated in hospitals in the
Thessaly region (1,000,000 habitants) of Greece. The aforementioned isolates
were characterized by antimicrobial susceptibility testing and carbapenemase
content, andtheir genetic relatedness was assessed by multilocus sequence
typingand eBURST analysis. Mapping of the genetic environment of the genes
encoding for carbapenemasewas performed. Finally, the chromosomal or plasmidic
localization of carbapenemase genes and the transferabilityof carbapenem
resistance in E. coli isolates were assessed. All carbapenem-resistantP.
aeruginosa isolates (n=80) recovered from clinical specimens were VIM
producers.Multilocus sequence typing revealed high prevalence of the
international clones ST111 and ST235 among blaVIM-2-and blaVIM-4-positive
isolates, respectively. blaVIM-17was identified in an isolate of a novel
sequence type (ST1457).blaVIM gene cassettes were carried by five distinct
class I integrons, including two novel ones and were chromosomally located.All
carbapenem-resistantA. baumannii isolates (n=127) recovered from clinical
specimens were OXA producers. Multilocus sequence typing revealed high
prevalence of the international clones ST1 and ST2 among both chromosomally
encoding blaOXA-23- and plasmidic encoding blaOXA-58 isolates.Both blaOXA-23and
blaOXA-58genes occurred as part of previously characterized mobile genetic
elements bracketed by two insertion sequences in opposite orientation.Finally,
even after numerous attempts of conjugative transfer no transconjugant was
Since the first report of carbapenem-resistant non-fermenting Gram-negative
bacteria, those microorganisms still remain among themost prevalent multidrug
resistant pathogens in Greece. The spread of carbapenemase-producers belonging
to the most common international clones and the spread of mobile genetic
elements of divergent structures, underscore their ongoing evolution. Hospital
personnel have been informed about ourfindings and infection control measures
have beenreinforced.
Resistance, Carbapenemases, Molecular epidemiology, Non-fermenting Gram negative bacteria, Bacteria
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