RESUMEN
Pulsed-field gel electrophoretic (PFGE) analysis of Helicobacter pylori isolates is not commonly employed because of the inability to compare the typing with other typing systems. We adapted the PFGE analysis for H. pylori by using EcoRI and slightly modified our laboratory methods to improve the typing of isolates (typeability was 97%).
Asunto(s)
Técnicas de Tipificación Bacteriana , Desoxirribonucleasa EcoRI/metabolismo , Helicobacter pylori/clasificación , ADN Bacteriano/análisis , Electroforesis en Gel de Campo Pulsado , Infecciones por Helicobacter/microbiología , Helicobacter pylori/genética , Helicobacter pylori/aislamiento & purificación , Humanos , Mapeo RestrictivoRESUMEN
The influence of the pretreatment of Pseudomonas aeruginosa strain O1 (PAO-1) with a sub-minimum inhibitory concentration (MIC) of imipenem on bactericidal activity, phagocytosis, the production of oxygen radical intermediates, and the induction of apoptosis in murine peritoneal neutrophils, as well as the catalase activity in the bacteria in comparison with that of ceftazidime-treated bacteria were studied. Bacteria treated with imipenem at (1/4) MIC were killed at significantly higher rates by neutrophils than ceftazidime-treated and nontreated bacteria. However, antibiotic-treated bacteria showed similar numbers of bacteria-phagocytized neutrophils to those in untreated bacteria. Imipenem pretreatment of bacteria led to an increase in the production of oxygen radical intermediates by neutrophils and the inhibition of neutrophilic apoptosis following incubation, whereas these features did not occur in neutrophils incubated with nontreated and ceftazidime-treated bacteria. The catalase activity of bacteria was not suppressed by pretreatment with either antibiotic at (1/4) MIC. These findings suggest that the exposure of P. aeruginosa to a sub-MIC of imipenem enhances the susceptibility of the bacteria to neutrophilic killing and effectively modifies the physiological activities of neutrophils, but does not decrease bacterial catalase activity. These actions may account for the postantibiotic leukocyte enhancement (PALE) effect of a sub-MIC of imipenem in the host.
Asunto(s)
Antibacterianos/farmacología , Imipenem/farmacología , Neutrófilos/inmunología , Fagocitosis/efectos de los fármacos , Pseudomonas aeruginosa/efectos de los fármacos , Animales , Actividad Bactericida de la Sangre/efectos de los fármacos , Catalasa/efectos de los fármacos , Catalasa/metabolismo , Ratones , Pruebas de Sensibilidad Microbiana , Neutrófilos/efectos de los fármacos , Pseudomonas aeruginosa/enzimologíaRESUMEN
A patient with infective endocarditis (IE) caused by methicillin-resistant Staphylococcus aureus (MRSA) was treated with vancomycin (VAN). VAN was ineffective, although therapeutic drug monitoring (TDM) indicated that the recommended trough level was maintained. Five MRSA isolates obtained at various times were analyzed to determine the minimum inhibitory concentration (MIC) and were subjected to population analysis, simulation analysis pulsed-field gel electrophoresis (PFGE). MRSA susceptible to VAN was isolated before and during the early stage of treatment, while an MRSA strain showing reduced VAN MIC was isolated during treatment. Simulation analysis indicated that the viable bacterial count only decreased to 10(-3) to 10(-4) cells after 72 h of incubation. The five MRSA strains isolated at various times were identical by PFGE.
Asunto(s)
Endocarditis Bacteriana/tratamiento farmacológico , Endocarditis Bacteriana/microbiología , Resistencia a la Meticilina , Infecciones Estafilocócicas/tratamiento farmacológico , Infecciones Estafilocócicas/microbiología , Staphylococcus aureus/efectos de los fármacos , Staphylococcus aureus/aislamiento & purificación , Resistencia a la Vancomicina , Recuento de Colonia Microbiana , ADN Bacteriano/genética , ADN Bacteriano/aislamiento & purificación , Farmacorresistencia Bacteriana Múltiple , Electroforesis en Gel de Campo Pulsado , Genotipo , Humanos , Técnicas In Vitro , Masculino , Pruebas de Sensibilidad Microbiana/instrumentación , Pruebas de Sensibilidad Microbiana/métodos , Persona de Mediana Edad , Staphylococcus aureus/genéticaRESUMEN
Linezolid (ZYVOX), a novel synthesized antibacterial drug, was first approved in April 2001, as an antibacterial against vancomycin (VCM)--resistant enterococci in Japan. LZD has a wide spectrum of antibacterial activity against gram-positive bacteria with MIC90 of 0.5-4 mcg/mL. These antibacterial activities of LZD are similar to those of vancomycin (VCM). LZD also has similar antibacterial activities against drug-resistant bacteria including VRE and MRSA. Protein-synthesis inhibitors, e.g., macrolides, tetracycline, aminoglycosides, and chloramphenicol, are known to bind the 30S and 50S subunits of ribosomes and inhibit the elongation cycle of protein synthesis. In contrast, LZD was found to inhibit the process of formation of the 50S, 30S-mRNA, and fMet-tRNA complex in the ribosome cycle, but not the elongation cycle. Due to this novel mechanism of action, LZD does not have a cross-resistance to drug-resistant bacteria and development of its resistance is quite slow. The antibacterial activity of LZD against VRE is bacteriostatic. In vivo antibacterial activity of orally administered LZD was demonstrated in a mouse model of systemic infection by VRE. When administered orally prior to the abscess formation in a mouse model of soft tissue infection by VRE, LZD showed similar antibacterial activity against VRE infection to that against VCM-susceptible enterococci. LZD is rapidly absorbed following oral administration and bioavailability when compared with intravenous administration is almost 100%. LZD administered orally twice-daily showed excellent efficacy in clinical trials with VRE-infected patients.
Asunto(s)
Acetamidas/farmacología , Acetamidas/uso terapéutico , Antibacterianos/farmacología , Antibacterianos/uso terapéutico , Oxazolidinonas/farmacología , Oxazolidinonas/uso terapéutico , Animales , Bacterias/efectos de los fármacos , Infecciones Bacterianas/tratamiento farmacológico , Farmacorresistencia Bacteriana , Humanos , Linezolid , RatonesRESUMEN
A cryptic plasmid of Helicobacter pylori, pKU701 (accession number AB078638), was isolated and the complete nucleotide sequence was determined. No drug resistance properties were mediated by pKU701. The 2454b pKU701 sequence, which had a 38% content of G-C residues, generated one polypeptide from a single open reading frame (ORF1). Extensive sequence homology was evident between pKU701 and ORF1 of H. pylori plasmid pHPO100 (repA, 88.8% identity) as well as ORF3 of plasmid pHPS1 (repB, 80.2% identity), but pKU701 showed only 46.3% homology with ORF1 of plasmid pHPK255 (repA). Tandem direct repeats of a 33-bp segment were found in pKU701 outside ORF1, but there were no inverted repeat ends such as those found in typical insertion sequences. The ability of drug resistance plasmids to replicate in H. pylori is probably limited, so chromosomal mutation may be a more likely cause of resistance.
Asunto(s)
Helicobacter pylori/genética , Plásmidos/genética , Secuencia de Aminoácidos , Antibacterianos/farmacología , Proteínas Bacterianas/química , Secuencia de Bases , Segregación Cromosómica , Clonación Molecular , Replicación del ADN , Farmacorresistencia Bacteriana Múltiple , Helicobacter pylori/efectos de los fármacos , Humanos , Japón , Datos de Secuencia Molecular , Análisis de Secuencia de ADN , Homología de Secuencia de AminoácidoRESUMEN
Helicobacter pylori (H. pylori) is a Gram-negative curved rod-like or spiral bacterium that chronically infects the human gastric mucosa, and is a major risk factor for gastritis, gastric and duodenal ulcer and adenocarcinoma of the stomach. After partial gastrectomy, some patients may have persistent H. pylori infection for five years or more. In this study, we detected three bacteria, i.e., Klebsiella pneumoniae, Enterobacter aerogenes, and Escherichia coli, in the gastric juice of patients with a remnant stomach. Some of these bacteria produced beta-lactamase. These findings are potentially important since such bacteria could provide H. pylori with the chance to acquire drug resistance and to transfer drug resistance genes. This could be one reason why H. pylori is difficult to eradicate in the remnant stomach.
Asunto(s)
Ampicilina/farmacología , Jugo Gástrico/microbiología , Muñón Gástrico , Helicobacter pylori/efectos de los fármacos , Helicobacter pylori/crecimiento & desarrollo , Lactamas/farmacología , Medios de Cultivo , Enterobacter aerogenes/enzimología , Enterobacter aerogenes/aislamiento & purificación , Infecciones por Enterobacteriaceae/microbiología , Escherichia coli/enzimología , Escherichia coli/crecimiento & desarrollo , Escherichia coli/aislamiento & purificación , Gastrectomía , Helicobacter pylori/enzimología , Humanos , Klebsiella pneumoniae/enzimología , Klebsiella pneumoniae/aislamiento & purificación , Pruebas de Sensibilidad Microbiana , Resistencia betalactámicaRESUMEN
We encountered three clinical isolates of methicillin-resistant Staphylococcus aureus which were susceptible to netilmicin and arbekacin in the absence of beta-lactam antibiotics but which were resistant to them in the presence of beta-lactam antibiotics. One of these strains, KU5801, was used to further investigate the antagonism between aminoglycosides and beta-lactam antibiotics. beta-Lactam antibiotics induced bacterial synthesis of aminoglycoside-6'-N-acetyltransferase and 2"-O-phosphotransferase [AAC(6')-APH(2")] in association with decreased antimicrobial activities of aminoglycosides. A 14.4-kb EcoRI fragment that included the genes that control for beta-lactam-inducible aminoglycoside resistance was cloned from a 31-kb conjugative plasmid present in KU5801. Restriction fragment mapping and PCR analysis suggested that a Tn4001-like element containing a gene encoding AAC(6')-APH(2") was located downstream from a truncated blaZ gene. The DNA sequence between blaR1 and a Tn4001-like element was determined. The Tn4001-IS257 hybrid structure was cointegrated into the blaZ gene, and the typical sequences for the termination of transcription were not found between these regions. We deduced that antagonism of aminoglycosides by beta-lactam antibiotics in isolate KU5801 involved transcription of the aac(6')-Ie-aph(2")-Ia gene under the influence of the system regulating penicillinase production.