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    ABSTRACT: Although antibiotic resistance has become a major threat to human health worldwide, this phenomenon has been largely overlooked in studies in environmental settings. Aquatic environments may provide an ideal setting for the acquisition and dissemination of antibiotic resistance, because they are frequently impacted by anthropogenic activities. This review focuses primarily on the emergence and dissemination of antibiotic resistance in the aquatic environment, with a special emphasis on the role of antibiotic resistance genes.
    Trends in Microbiology 01/2014; 22(1):36-41. DOI:10.1016/j.tim.2013.11.001 · 9.81 Impact Factor
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    ABSTRACT: Early after the introduction of the first (narrow spectrum) penicillins into clinical use, penicillinase-producing staphylococci replaced (worldwide) the previously susceptible microorganisms. Similarly, the extensive use of broad-spectrum, orally administered β-lactams (like ampicillin, amoxicillin or cefalexin) provided a favorable scenario for the selection of gram-negative microorganisms producing broad spectrum β-lactamases almost 45 years ago. These microorganisms could be controlled by the introduction of the so called "extended spectrum cephalosporins". However, overuse of these drugs resulted, after a few years, in the emergence of extended-spectrum β-lactamases (ESBLs) through point mutations in the existing broad-spectrum β-lactamases, such as TEM and SHV enzymes. Overuse of extended-spectrum β-lactams also gave rise to chromosomal mutations in regulatory genes which resulted in the overproduction of chromosomal AmpC genes, and, in other regions of the world, in the explosive emergence of other ESBL families, like the CTX-Ms. Carbapenems remained active on microorganisms harboring these extended-spectrum β-lactamases, while both carbapenems and fourth generation cephalosporins remained active towards those with derepressed (or the more recent plasmidic) AmpCs. However, microorganisms countered this assault by the emergence of the so called carbapenemases (both serine- and metallo- enzymes) which, in some cases, are actually capable of hydrolyzing almost all β-lactams including the carbapenems. Although all these enzyme families (some of them represented by hundreds of members) are for sure pre-dating the antibiotic era in environmental and clinically significant microorganisms, it was the misuse of these antibiotics that drove their evolution. This paper describes in detail each major class of β-lactamase including epidemiology, genetic, and biochemical evaluations.
    Current pharmaceutical design 08/2012; 19(2). DOI:10.2174/13816128130202 · 4.41 Impact Factor
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    ABSTRACT: Introduction: Insertion sequences such as IS CR1 promote capture, transposition and expression of bla CTX-M genes. Thus, gene dissemination in bacterial populations occurs rapidly. Objective: To determine the presence of IS CR1 sequence genes and their association with bla CTX-M-1 and bla CTX-M-2 on plasmids IncN and IncFIIA from K. pneumoniae of nosocomial origin, was determined. Materials and methods: Three strains of K. pneumoniae with reduced susceptibility to extendedspectrum cephalosporins were isolated from neonatal sepsis cases of nosocomial origin. Phenotypic tests showed the presence of ESBLs. Plasmids were isolated and classified according to incompatibility groups by PCR replicon typing. Detection and association of IS CR1 with bla CTX-M genes were determined by PCR and direct sequencing through the use of several sets of PCR primers. Results: All strains showed phenotypic profile consistent with ESBL-producing transferred by conjugation. PCR amplification assay for CTX-M together with sequencing analysis revealed that strains carrying bla CTX-M-1 y bla CTX-M-2 genes were localized in plasmids of approximately 150 kb related to IncN and IncFIIA groups, respectively. IS CR1 was found upstream and associated with bla CTX-M-1 y bla CTX-M-2 genes. Conclusion. Thus far, this is the first Venezuelan report, in which IS CR1 presence is closely related to bla CTX-M-1 y bla CTX-M-2 gene mobilization in IncN and IncFIIA conjugative plasmids located in K. pneumonaiae strains circulating at a neonatal high risk unit.
    Biomédica: revista del Instituto Nacional de Salud 06/2013; 33(2):269-75. DOI:10.7705/biomedica.v33i2.774 · 0.62 Impact Factor