Se
transcribe el Resumen del Proyecto FONDECYT obtenido por el Dr. Gerardo González Rocha, luego que 9
grupos de investigación de la Facultad de Ciencias Biológicas se adjudicaron
proyectos presentados al Concurso de Proyectos Regular Fondecyt 2013.
En
este trabajo de investigación participan además: Universidad
de Concepción: Dras.: Helia Bello Toledo y Mariana Domínguez Yévenes. Instituto de Salud Pública de Chile:
Dres.: Juan Carlos Hormazábal Opazo, Jorge Fernández Órdenes, Pamela Araya
Rodríguez y Soledad Prat Miranda.
Título del Proyecto
.
“Microbiological and molecular characterization of
carbapenemase-producing Enterobacteriaceae and geneticplatforms of this
important and emerging beta-lactamase in Chileanhospitals”.
Soon after the beginning of
antibiotic usage, the antimicrobial resistance (AR) has been increasing in many
bacterial species, especially during last 10 years. Thus, on April 7th,
2011 the WHO established during the World Health Day celebration the lemma “Antimicrobial resistance: no action today,
no cure tomorrow”,introducing a six-point policy package to combat the
spread of AR. In general, costs of infections are high-priced, by increaseof
length of stay and morbi-mortality. Additional problem is the loss of low-cost
and old antibiotics to treat it, considering the limited development of new
antibiotics. This situation reveals the importance of improving the infection
control actions and developing antimicrobial surveillance programs to allow the
detection of: resistant bacteria, emergence and spread of new resistance
mechanisms, and identification of the population structure of resistant
bacteria, especially the so-called high-risk clones. These actions and
knowledge will help to diminish the emergence and dissemination of antibiotic
resistant bacteria, mainly inside hospitals. Carbapenems (CBP) are the main
antibiotics choice to treat multidrug-resistantenterobacteria, particularly
ESBL producers. However, the vast consumption of CBP has led to the emergence
of clinical isolates with resistance or reduced susceptibility, mainly among Klebsiella
pneumoniae and Escherichia coli. Therefore, the emergence of these
strains constitutes a worldwide serious threat, since the therapeutic options
are extremely limited, forcing the clinicians to use old and discharged
antibiotics, such as colistin, which has a significant toxicity, and also, to
which some resistant strains have been reported. The resistance to CBP in
enterobacteria is due to several mechanisms: production of CBP-hydrolysingβ-lactamases (carbapenemases, [CBPase]);alteration in porin, and up-regulation of
efflux pump system, associated with ESBL or high levels AmpCenzymes production.
In Chile,enterobacteria showing resistance or decreased susceptibility to CBP
have increased importantly during the last years, and worse yet, the first
strain of K. pneumoniae producing KPC
CBPase was reported in March2012, and at time of submission this proposal had
already informed other 6 cases byInstituto de SaludPública de Chile (ISP).
However, this situation could be worse, due to difficulties in the phenotypic
detection of these resistant isolates. There are some strains harboringblaKPC
gene, but the minimal inhibitory concentration (MIC) of CBP, although elevated,
is still within the susceptible category. For this reason, in 2010 CLSI
published new breakpointsfor CBP for enterobacteria. According to these the
strains will be categorized as susceptible to imipenem and meropenem with MIC ≤1μg/ml and ertapenem with
MIC ≤0.5μg/ml, allowing an early detection of CBP-resistant enterobacteria
(CBPRE). It is therefore very important to know which enzymes are responsible
for CBP resistance in Chilean strains of enterobacterias, which are the genetic
platforms whereblagenes are located,
how these genes are mobilized among Gram-negative bacteria in hospitals and
community, and to know clonalityof clinical CBPase-producer strains.
Consequently, the aims of this proposal is to determine the prevalence of
CBPaseamongCBPRE isolated in Chilean hospitals, the molecular clonality, and
the genetic platforms where the CBPase-encoding genes are located, andtheir
dissemination to other susceptible Gram-negative bacilli.The strains included
in this study will be those collected by ISP in the National Surveillance
Program of CBPRE, and will be evaluated for: 1) antibiotic profiles and levels
of resistance following the CLSI guidelines; 2) clonality by analysis of
chromosomal DNA restriction patterns by PFGE and MLST; 3) CBPaseproduction by
the boronic acid- or oxacillin-based modified Hodge test for class A CBPase,
and by imipenem/imipenem+EDTA disk method for metalloβ-lactamases; 4)
CBPase-encoding blagenes by PCR and sequencing; 5) localization of blagenes
studying plasmid content, plasmid curing, and transference capability by mating
experiments, and 6) detection of blagenes coding for CBP resistance as
gene cassettes in integrons by PCR and DNA sequencing of the variable regions
of these structures. The results of this study will allow knowing the genetic
diversity of CBPRE CBPase-producer and the epidemiological relatedness between
these isolates. This knowledge will contribute to set up or reinforce
epidemiologic control measures improving the control of nosocomial infections
in the Chilean hospitals, and also to transfer the experience and knowledge to
other professional. On the other hand, understanding the genetic surrounding of
the genes encoding this resistance, will allow us to know the feasibility of
dissemination of CBPase. Additionally this knowledge is a desirable
pre-requisite to the design and development of intervention strategies intended
to minimize the threat poses by infections produced by CBPRE.
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