Primera comunicación en Chile de la detección del gen mcr-1 en un aislado clínico de Escherichia coli resistente a colistín / First report in Chile of a clinical isolate of Escherichia coli resistant to colistin harbouring the mcr-1 gene

Recently it was described the plasmidial gene mcr-1 associated with colistin resistance. We screened by PCR and sequencing for gene mcr-1 in thirteen clinical isolates resistant to colistin. We observed amplification in one E. coli. To our knowledge, this is the first report of the presence of mcr-1 gene in Chile.

Plasmid-mediated mcr-1 in carbapenem-susceptible Escherichia coli ST156 causing a blood infection: an unnoticeable spread of colistin resistance in Brazil?

OBJECTIVE: We describe an IncX4 pHC891/16mcr plasmid carrying mcr-1 in a colistin-resistant and carbapenem-susceptible E. coli isolate (HC891/16), ST156, which caused a blood infection in a Brazilian patient with gallbladder adenocarcinoma. METHODS: Strain HC891/16 was subjected to whole genome sequencing using the MiSeq Platform (Illumina, Inc., USA). Assembly was performed using Mira and ABACAS. RESULTS: The isolates showed resistance only to ciprofloxacin, ampicillin and cefoxitin, and whole-genome sequencing revealed the presence of aac(6')Ib-cr and blaTEM1. CONCLUSION: Our findings warn of the possible silent dissemination of colistin resistance by carbapenem-susceptible mcr-1 producers, as colistin susceptibility is commonly tested only among carbapenem-resistant isolates.

ß-lactamases produced by amoxicillin-clavulanate-resistant enterobacteria isolated in Buenos Aires, Argentina: A new blaTEMgene / ß-lactamasas producidas por enterobacterias resistentes a amoxicilina-ácido clavulánico aisladas en Buenos Aires, Argentina: un nuevo gen blaTEM

La resistencia a la combinación de ß-lactámico/inhibidor de ß-lactamasa en enterobacterias es un problema creciente que no ha sido estudiado intensamente en Argentina. En el presente trabajo, 54/843 enterobacterias recolectadas en un hospital universitario de la ciudad de Buenos Aires fueron resistentes a ampicilina-sulbactama, pero se mantuvieron sensibles a las cefalosporinas de segunda y tercera generación. Se analizaron los mecanismos enzimáticos presentes en los aislamientos que también fueron resistentes a amoxicilina-ácido clavulánico (AMC) (18/54). La secuenciación reveló dos variantes diferentes de blaTEM-1, donde blaTEM-1b es el alelo más frecuentemente detectado (10 Escherichia coli, 3 Klebsiella pneumoniae, 2 Proteus mirabilis y 1 Raoultella terrigena), seguidos por blaTEM-1a(1 K. pneumoniae). La resistencia a AMC parece estar asociada principalmente con la hiperproducción de TEM-1 (sobre todo en E. coli) o con la coexpresión con ß-lactamasas tipo OXA-2 y/o SHV (K. pneumoniae y P. mirabilis). Se describió una nueva variante de blaTEM(TEM-163) en un aislamiento de E. coli que presentó una CIM frente a AMC de 16/8 µg/ml. La enzima TEM-163 contiene dos sustituciones de aminoácidos respecto de TEM-1, Arg275Gln y His289Leu. Teniendo en cuenta la alta actividad específica observada y la baja IC50 para el ácido clavulánico, el patrón de resistencia de este aislamiento parece obedecer a la hiperproducción de la nueva variante de la ß-lactamasa de amplio espectro, en lugar de vincularse con un comportamiento similar al de una TEM resistente a inhibidores (IRT).

Resistance to ß-lactam/ß-lactamase inhibitors in enterobacteria is a growing problem that has not been intensively studied in Argentina. In the present work, 54/843 enterobacteria collected in a teaching hospital of Buenos Aires city were ampicillin-sulbactam-resistant isolates remaining susceptible to second-and third-generation cephalosporins. The enzymatic mechanisms present in the isolates, which were also amoxicillin-clavulanic acid (AMC)-resistant (18/54) were herein analyzed. Sequencing revealed two different variants of blaTEM-1, being blaTEM-1b the most frequently detected allelle (10 Escherichia coli, 3 Klebsiella pneumoniae, 2 Proteus mirabilis and 1 Raoultella terrigena) followed by blaTEM-1a(1 K. pneumoniae). Amoxicillin-clavulanate resistance seems to be mainly associated with TEM-1 overproduction (mostly in E. coli) or co-expressed with OXA-2-like and/or SHV ß-lactamases (K. pneumoniae and P. mirabilis). A new blaTEMvariant (TEM-163) was described in an E. coli strain having an AMC MIC value of 16/8 µg/ml. TEM-163 contains Arg275Gln and His289Leu amino acid substitutions. On the basis of the high specific activity and low IC50 for clavulanic acid observed, the resistance pattern seems to be due to overproduction of the new variant of broad spectrumß-lactamase rather than to an inhibitor-resistant TEM (IRT)-like behavior.

From Escherichia coli heat-stable enterotoxin to mammalian endogenous guanylin hormones

The isolation of heat-stable enterotoxin (STa) from Escherichia coli and cholera toxin from Vibrio cholerae has increased our knowledge of specific mechanisms of action that could be used as pharmacological tools to understand the guanylyl cyclase-C and the adenylyl cyclase enzymatic systems. These discoveries have also been instrumental in increasing our understanding of the basic mechanisms that control the electrolyte and water balance in the gut, kidney, and urinary tracts under normal conditions and in disease. Herein, we review the evolution of genes of the guanylin family and STa genes from bacteria to fish and mammals. We also describe new developments and perspectives regarding these novel bacterial compounds and peptide hormones that act in electrolyte and water balance. The available data point toward new therapeutic perspectives for pathological features such as functional gastrointestinal disorders associated with constipation, colorectal cancer, cystic fibrosis, asthma, hypertension, gastrointestinal barrier function damage associated with enteropathy, enteric infection, malnutrition, satiety, food preferences, obesity, metabolic syndrome, and effects on behavior and brain disorders such as attention deficit, hyperactivity disorder, and schizophrenia.

Detection of bla SHV and bla CTX-M genes in ESBL producing Klebsiella pneumoniae isolated from Egyptian patients with suspected nosocomial infections

The correct identification of the genes involved in ESBL mediated resistance is necessary for the surveillance and epidemiological studies of their transmission in hospitals. The aim of the present study was to find the prevalence of ESBL producing Klebsiella pneumonia among K. pneumonia isolates separated from Egyptian patients with suspected nosocomial infections, to detect their drug resistance pattern and to look for bla SHV and bla CTX-M genes in such organisms. 138 K. pneumonia isolates from Egyptian patients with suspected nosocomial infections were screened for ESBL production by the pattern of antimicrobial susceptibilities. Phenotypic identification for ESBL production was confirmed by double disc synergy test, phenotypic confirmatory double disc test and by MicroScan panel system. bla SHV and bla CTX-M genes in ESBL producing K. pneumonia were detected using multiplex PCR. The prevalence of ESBL producing K. pneumonia was 21% [30/138]. Their pattern of antimicrobial susceptibility showed that 90% was resistant to [Sulphamethoxazole / Trimethoprim], 70% was resistant to [Amoxicillin / Clavulanate], 63.3% was resistant to Cefotaxime and Ceftazidime, 60% was resistant to Amikacin, 46.7% was resistant to Doxycycline, Cefoxitin, Ceftriaxone and Levofloxacin, 40% was resistant to Cefepime, 20% was resistant to Ertapenem and [Sulbactam / Cefoperazone], 13.3% was resistant to [Piperacillin / Tazobactam], 10% was resistant to [Imipenem/Cilastatin] and Gentamycin and 6.7% was resistant to Meropenem and Ciprofloxacin. Among the ESBL producing K. pneumoniae, three out of 30 [10%] and 16 out of 30 [53.3%] were positive for bla SHV and bla CTX-M genes respectively. It could be concluded that ESBL producing isolates of K. pneumonia have been increasingly recognized in the hospital settings in Egypt and are associated with multiple drug resistance. Thus, molecular identification of the genes encoding beta lactamases would be essential for a reliable epidemiological investigation of their transmission in hospitals and antimicrobial resistance

SHV-type extended-spectrum beta-lactamase (ESBL) are encoded in related plasmids from enterobacteria clinical isolates from Mexico

OBJECTIVE: In this work we report the molecular characterization of beta-lactam antibiotics resistance conferred by genes contained in plasmids from enterobacteria producing extended-spectrum beta-lactamases (ESBL). MATERIAL AND METHODS: Fourteen enterobacterial clinical isolates selected from a group of strains obtained from seven different hospitals in Mexico during 1990-1992 and 1996-1998 were analyzed at the Bacterial Resistance Laboratory (National Institute Public Health, Cuernavaca). Molecular characterization included PFGE, IEF of beta-lactamases, bacterial conjugation, PCR amplification and DNA sequencing, plasmid extraction and restriction. RESULTS: Isolates were genetically unrelated. ESBL identified were SHV-2 (5/14) and SHV-5 (9/14) type. Cephalosporin-resistance was transferable in 9 of 14 (64 percent) clinical isolates with only one conjugative plasmid, DNA finger printing showed a similar band pattern in plasmids. CONCLUSIONS: The dissemination of cephalosporin resistance was due to related plasmids carrying the ESBL genes.

OBJETIVO: En este trabajo se reporta la caracterización molecular de la resistencia a antibiótico beta-lactámicos conferida por genes contenidos en plásmidos de enterobacterias productoras de beta-lactamasas de espectro extendido (BLEEs). MATERIAL Y MÉTODOS: Catorce aislamientos clínicos de enterobacterias fueron seleccionados por conveniencia de un banco de cepas obtenidas de siete diferentes hospitales de México durante los periodos 1990-1992 y 1996-1998 y fueron procesados en el Laboratorio de Resistencia Bacteriana (Instituto Nacional de Salud Pública, Cuernavaca). En la caracterización se empleó PFGE, IEF para beta-lactamasas, conjugación bacteriana, amplificación por PCR y secuenciación de DNA, extracción y restricción de plásmidos. RESULTADOS: Las 14 cepas fueron no relacionadas genéticamente. Se identificaron BLEEs tipo SHV-2 (5/14) y SHV-5 (9/14). La resistencia a cefalosporinas fue transferida por conjugación en 9 de 14 (64 por ciento) aislamientos clínicos mediante un plásmido que mostró un patrón de restricción similar entre ellos. CONCLUSIÓN: Se sugiere que la diseminación de la resistencia a cefalosporinas fue debida a plásmidos relacionados que contienen los genes que codifican BLEEs.