Primer aislamiento de enterobacteria productora de carbapenemasa tipo-NDM en un hospital público de Rosario, Argentina PDF / First isolation of a NDM-like carbapenemase-producing Enterobacteriaceae in a public hospital in Rosario, Argentina

Introducción: La emergencia de enterobacterias productoras de carbapenemasas en el ámbito hospitalario representa un verdadero problema de salud pública mundial. Las carbapenemasas son enzimas que producen resistencia a los antibióticos carbapenémicos, teniendo un directo impacto en la disponibilidad de alternativas terapéuticas. En Argentina, a partir de 2013 han emergido carbapenemasas tipo-NDM (Nueva Delhi Metalo-ß-lactamasa, MßL), que constituyen una resistencia emergente a nivel global. Objetivo: Reportar el primer aislamiento clínico de enterobacteria portadora de NDM en nuestra institución. Materiales y métodos: El aislamiento estudiado fue recuperado de una muestra ósea de un paciente adulto. La identificación bacteriana y los ensayos de susceptibilidad antibiótica se realizaron mediante metodología manual y sistema automatizado Vitek 2C (Biomérieux). La detección y caracterización de carbapenemasas se efectuó por ensayos fenotípicos y moleculares. Resultados: Los ensayos revelaron que el aislamiento, tipificado como Citrobacter freundii, es productor de carbapenemasa tipo NDM. Resultó sensible a aztreonam, colistina y fosfomicina. No se detectó fenotípicamente la presencia de beta lactamasas de espectro extendido. Discusión: Se reporta el primer aislamiento de enterobacteria productor de MßL tipo-NDM en nuestro nosocomio, siendo multirresistente, con escasas alternativas terapéuticas. Dado que la presencia de este tipo de aislamiento es considerado de alto riesgo, se requiere un monitoreo activo de este mecanismo de resistencia y la instauración de medidas de control adecuadas para hacer frente a la amenaza que suponen

Introduction: the emergence of carbapenemase-producing Enterobaceriaceae in the hospital environment represents a major challenge for health care worldwide. Carbapene-mases are carbapenem-hydrolysing enzymes that confer resistance to these "last-line" antibiotics having a direct im-pact on the limited treatment options available. In Argentina, carbapenemases NDM-like (New DelhiMetallo-ß-lactamase, MßL) have emerged in 2013. This resistance has increased in frequency and it has disseminated around the world at unprecedented levels.Objective:report the first isolation of a NDM-producing En-terobacteriaceae in our hospital.Materials and methods: the isolate analysed in this study was recovered from a bone biopsy belonging to an adult patient. The bacterial identification and antimicrobial sus-ceptibility testings were performed using conventional methods and the automated system Vitek 2C (Biomérieux). Phenotypic and molecular techniques were carried out for the detection and characterization of carbapenemases.Results: it was confirmed that the isolate, identified as Citro-bacter freundii, produces the NDM enzyme. It showed sensi-bility to aztreonam, colistin and fosfomicyn. Extended-spec-trum beta-lactamases were not detected.Discussion: in this study we report the first isolation of NDM-like MßL in our institution, a multirresistant pathogen associ-ated with a lack of effective antimicrobial treatment options. Given the high risk of these infections, an active search of mechanisms of resistance is mandatory. In addition, the establishment of accurate control measures is a must to attempt to overcome this formidable threat

More Than Just Light: Clinical Relevance of Light Perception in the Nosocomial Pathogen Acinetobacter baumannii and Other Members of the Genus Acinetobacter.

A summary of the major findings concerning light modulation in Acinetobacter baumannii, which governs aspects related to the success of this microorganism as a nosocomial pathogen, is presented. Particularly, the evidence shows that light modulates the ability of the bacteria to persist in the environment, its virulence against eukaryotic hosts and even susceptibility to certain antibiotics. The light signal is sensed through different mechanisms, in some cases involving specialized photoreceptors of the BLUF-type, whereas in others, directly by a photosensitizer molecule. We also provide new data concerning the genomic context of BLUF-domain containing proteins within the genus Acinetobacter, as well as further insights into the mechanism of light-mediated reduction in susceptibility to antibiotics. The overall information points toward light being a crucial stimulus in the lifestyle of members of the genus Acinetobacter as well as in other clinically relevant species, such as members of the ESKAPE group, playing therefore an important role in the clinical settings.

White and blue light induce reduction in susceptibility to minocycline and tigecycline in Acinetobacter spp. and other bacteria of clinical importance.

Minocycline (MIN) and tigecycline (TIG) are antibiotics currently used for treatment of multidrug-resistant nosocomial pathogens. In this work, we show that blue light, as well as white light, modulates susceptibility to these antibiotics in a temperature-dependent manner. The modulation of susceptibility by light depends on the content of iron; an increase in iron results in a reduction in antibiotic susceptibility both under light and in the dark, though the effect is more pronounced in the latter condition. We further provide insights into the mechanism by showing that reduction in susceptibility to MIN and TIG induced by light is likely triggered by the generation of (1)O2, which, by a yet unknown mechanism, would ultimately lead to the activation of resistance genes such as those coding for the efflux pump AdeABC. The clinical relevance of these results may lie in surface-exposed wound infections, given the exposure to light in addition to the relatively low temperatures recorded in this type of lesion. We further show that the modulation of antibiotic susceptibility occurs not only in Acinetobacter baumannii but also in other micro-organisms of clinical relevance such as Escherichia coli and Staphylococcus aureus. Overall, our findings allow us to suggest that MIN and TIG antibiotic treatments may be improved by the inclusion of an iron chelator, in addition to keeping the wounds in the dark, a condition that would increase the effectiveness in the control of infections involving these micro-organisms.

Diversidad de ß-lactamasas en aislamientos clínicos de enterobacterias / ß-lactamases diversity in clinical isolates of enterobacterias / Diversidade de ß-lactamases em isolamentos clinicos de enterobactérias

La rápida emergencia de resistencia a antimicrobianos debida a la presencia de b-lactamasas de espectro extendido (BLEE) tiene un impacto significativo en la salud pública. Las BLEEs son enzimas producidas por bacilos gramnegativos y confieren resistencia a las penicilinas, a todas las cefalosporinas y al aztreonam, pero no a los carbapenemes ni a las cefamicinas y la mayoría son inhibidas por el ácido clavulánico. El objetivo de este trabajo fue evaluar la resistencia a antibióticos b-lactámicos en aislamientos de Klebsiella pneumoniae, Escherichia coli y Proteus mirabilis y caracterizar las b-lactamasas responsables de dicha resistencia. Se analizaron 2.030 aislamientos (362 Klebsiella pneumoniae, 1.250 Escherichia coli y 175 Proteus mirabilis) provenientes de diferentes materiales clínicos de pacientes que concurrieron al Hospital Provincial del Centenario de la ciudad de Rosario (Santa Fe) durante el período 2008-2009. Los ensayos de sensibilidad antibiótica se realizaron de acuerdo con las recomendaciones del Clinical and Laboratory Standard Institute. Se confirmó la presencia de los genes codificantes de BLEE blaTEM, blaSHV, blaCTX-M y blaPER mediante la reacción en cadena de la polimerasa (PCR) utilizando cebadores específicos. Los aislados fueron caracterizados fenotípicamente como productores de BLEE y demostraron poseer varios genes bla. Se detectaron tres diferentes b-lactamasas BLEE derivadas de SHV, TEM y CTX-M y se demostró que pueden coexistir dos o más de estos genes en una misma bacteria.

The rapid emergence of antimicrobial resistance due to extended spectrum b-lactamases (ESBL) has a significant impact on public health. ESBL, produced by gram-negative bacilli, are enzymes that confer resistance to penicillins, cephalosporins and aztreonam, but not to carbapenems or cephamycins, and are usually inhibited by clavulanic acid. The aim of this study was to evaluate b-lactam resistance within isolates of Klebsiella pneumoniae, Escherichia coli, and Proteus mirabilis and to characterize the b-lactamases responsible for this resistance. A total of 2,030 strains (362 Klebsiella pneumoniae, 1,250 Escherichia coli, and 175 Proteus mirabilis) isolated from patients at Hospital Provincial del Centenario in Rosario-Santa Fe were analyzed from 2008 to 2009. Antibiotic sensitivity tests were performed according to Clinical and Laboratory Standard Institute recommendations. Molecular detection of ESBL-related bla genes, including blaTEM, blaSHV, blaCTX-M and blaPER was performed by polymerase chain reaction (PCR) using specific primers. The strains were phenotipically confirmed as ESBL producers and the isolates carried several bla genes. Three different b-lactamases were detected: SHV-related, TEM-related and CTX-M-related, showing that two or more genes may coexist in the same bacterium.

A rápida emergência de resistência a antimicrobianos devida à presença de b lactamases de espectro estendido (BLEE) tem um impacto significativo na saúde pública. As BLEEs são enzimas produzidas por bacilos gram-negativos e conferem resistência às penicilinas, a todas as cefalosporinas e ao aztreonam, mas não aos carbapenêmicos nem às cefamicinas e a maioria são inibidas pelo ácido clavulânico. O objetivo deste trabalho foi avaliar a resistência a antibióticos b-lactâmicos em isolamentos de Klebsiella pneumoniae, Escherichia coli e Proteus mirabilis e caracterizar as b-lactamases responsáveis por tal resistência. Foram analisados 2.030 isolamentos (362 Klebsiella pneumoniae, 1.250 Escherichia coli e 175 Proteus mirabilis) provenientes de diferentes materiais clínicos de pacientes que foram ao Hospital Provincial do Centenário da cidade de Rosario (Santa Fe) durante o período 2008-2009. Os ensaios de sensibilidade antibiótica foram realizados de acordo com as recomendações do Clinical and Laboratory Standard Institute. Confirmou-se a presença dos genes codificantes de BLEE blaTEM, blaSHV, blaCTX-M e blaPER mediante a reação em cadeia da polimerase (PCR) utilizando cevadores específicos. Os isolados foram caracterizados fenotipicamente como produtores de BLEE e demonstraram possuir vários genes bla. Foram detectadas três diferentes b-lactamases derivadas de SHV, TEM e CTX-M e se demonstrou que podem coexistir dois ou mais destes genes numa mesma bactéria.

Inhibition of the adhesion to catheters of uropathogenic Escherichia coli by sub-inhibitory concentrations of cefotaxime.

OBJECTIVE: To investigate the effect of sub-inhibitory concentrations of cefotaxime on adherence to siliconized latex urinary catheters of uropathogenic Escherichia coli strains from pregnant and non pregnant patients. STUDY DESIGN: Using random sampling, 30 E. coli strains were selected from hospitalized patients with catheter associated urinary tract infection, 12 from pregnant women and 18 from men and non-pregnant women. The strains were categorized on the basis of cefotaxime susceptibility, adhesion and biofilm production capacity, cell surface hydrophobicity and expression of adhesins and fimbriae in vitro. RESULTS: The overall results indicated that sub-inhibitory concentrations of cefotaxime could reduce the adhesiveness, the biofilm production and hence, potentially, the infection rate associated with indwelling urinary catheters. CONCLUSION: Based on our results, we propose that this reduction is due to decreasing exopolysaccharide production and increasing cell surface hydrophobicity of E.coli strains.

Effect of ciprofloxacin on adhesive properties of non-P mannose-resistant uropathogenic Escherichia coli isolates.

The influence of sub-MIC of ciprofloxacin on the surface properties of 25 non-P mannose-resistant uropathogenic Escherichia coli (UPEC) strains was studied. Thirteen isolates responded to antibiotic treatment with an increase in haemagglutination titre and/or surface hydrophobicity, which correlated with a higher expression of surface proteins. Only UPEC strains with ciprofloxacin-enhanced hydrophobicity increased their adhesiveness to urinary catheters that correlated, in one analysed case, with a dramatic increase in the number of fimbriae peripherally located. The overall results indicate that sub-MICs of ciprofloxacin could increase the adhesiveness, and hence the risk of colonization by UPEC strains expressing mannose-resistant adhesins different from type P.