Consideraciones generales sobre el uso de agentes antimicrobianos en pacientes hepáticos / General remarks: antimicrobial agents use in hepatic patients

El hígado juega un papel fundamental en el metabolismo de las drogas, incluyendo los antimicrobianos. En los pacientes con enfermedad hepática, se deben monitorizar cuidadosamente los efectos adversos y toxicidad de estos medicamentos. En este artículo se analizan los aspectos del metabolismo de los antimicrobianos, particularmente relacionados a los cambios farmacocinéticos en los pacientes hepáticos. Además, se dan algunas recomendaciones prácticas sobre su uso en estos pacientes

Características de la resistencia antimicrobiana de una colección clínica de Streptococcus pyogenes / Antimicrobial resistance of Streptococcus pyogenes clinical strains

Objetivo. Determinar la susceptibilidad antimicrobiana de Streptococcus pyogenes con el fin de estimar la prevalencia de los fenotipos de resistencia a los macrólidos. Material y métodos. Se realizó un estudio de tipo transversal, en 1999, en el que se evaluaron 100 cepas de S. pyogenes, aislados en el Hospital Infantil de México Federico Gómez, en el lapso comprendido entre 1992 y 1998, procedentes de niños con faringoamigdalitis, conservadas en congelación en el laboratorio de bacteriología hasta su procesamiento. Se determinó la susceptibilidad antimicrobiana a algunos blactámicos, macrólidos y clindamicina. La resistencia a eritromicina se probó por medio de la prueba de difusión de doble disco. Se calcularon medidas de tendencia central. Resultados. Todas las cepas fueron sensibles a los blactámicos y clindamicina; 16 por ciento fueron resistentes a los macrólidos, y todas correspondieron al fenotipo M. Conclusiones. Es conveniente realizar periódicamente pruebas de escrutinio para conocer los posibles cambios en los patrones de sensibilidad estreptocócica.

Evaluation in an animal model and in vitro of the combination clavulanic acid and cephalosporins against ß-lactamase producing and nonproducing staphylococcus aureus strains

ß-lactamase enzymes are the most common case of bacterial reistance to ß-lactam antibiotics. They hydrolyse the amide bound in the ß-lactam ring and produce acidic derivatives that have no antibacterial properties. The aim of this study was to evaluate a combination of clavulanic acid with cephalosporins against ß-lactamase-producing and nonproducing stains of Staphylococcus aureus using in vitro tests and a rat animal model. In vitro test (MIC) of the drug combination were done using standard methods. In an animal model, rats were submitted to surgical implantation of polyurethane sponges in their backs to induce granulomatous tissue. After seven days, the animals received cephalexin, cephalexin with clavulanic acid, ceftriaxone, ceftriaxone with clavulanic acid or clavulanic acid alone. One hour after the drug administration, granulomatous tissue was removed and placed in Petri dishes previously inoculated with 10 eight cfu of producing or non-producing ß-lactamase Staphylococcus aureus. After 24h at 37§C, the inhibition zones formad by granulomatous tissue was measured and scored for statistical analysis. Both tests (ex vivo {animal model} and in vitro) showed that the cephalexin was more active than ceftriaxone against non-producing ß-lactamase. S. aureus (p<0.01). Against ß-lactamase producing S. aureus, ceftriaxone was more active than cephalexin, which was inactive. Combinations of clavulanic acid with cephalexin or ceftriaxone had similar antimicrobial activity against non-producing ß-lactamase S. aureus compared to the cephalosporins used alone. When tested using ß-lactamase produzing strains, the combination of clavulanic acid with cephalosporins showed synergism. We conclude that the combination of cephalosporins with clavulanic acid could be useful in staphylococcal infections cauded by ß-lactamase producing strains.

Effect of Micelles, microemulsions and other supramolecular aggregates on the hydrolysis of ß-lactam antibiotics

Realizou-se a revisäo crítica da literatura a respeito da estabilidade de antibióticos ß-lactâmicos em presença de compostos tensoativos. No desenvolvimento da discussäo, analisaram-se os fatores envolvidos na decomposiçäo dos fármacos. A análise indicou que alguns sistemas organizados, obtidos a partir de tensoativos, podem ser usados no controle de velocidade e em mecanismos de decomposiçäo dos antibióticos. Além disso, esses sistemas podem fornecer informaçöes específicas sobre a reatividade desses fármacos num microambiente similar ao do sítio ativo, onde esses compostos devem exercer seu efeito farmacológico.

Streptococcus pneumoniae resistente a antibióticos: aspectos microbiológicos y clínicos / Streptococcus pneumoniae resistant to antibiotics: microbiological and clinical aspects

Se han detectado cepas de S. pneumoníae resistentes a los agentes antimicrobianos en todos los continentes llegando a constituir patógenos predominantes en algunas áreas; muchas de estas cepas son multiresistentes. Debido a la importancia de los neumococos en la etiología de meningitis, cepas con una concentración inhibitorio mínima (CIM) de penicilina G de < 0,06 pg/mi son consideradas sensibles, mientras que las con una CIM de 0,1 a 1 pg/mi son catalogadas como de sensibilidad intermedia y las con CIM de > 1 pg/ mi son denominadas resistentes. Esta revisión comprende los métodos de su detección, las técnicas de estudio de sensibilidad y la terapia de infecciones neumocócicas causadas por cepas resistentes. Recientemente se han definido los métodos de estudio de sensibilidad para ser usados en S. pneumoníae. Se recomienda la evaluación de resistencia a penicilina con discos de 1 pg de oxacilina en todas las cepas aisladas de infecciones clinicamente significativas, el estudio de la actividad in vítro de otros beta-lactámicos en cepas resistentes a penicilina y la determinación de la CIM para otros grupos de agentes antimicrobianos. El tratamiento de infecciones neumocóccicas resistentes depende del grado de resistencia a penicilina y a otros fármacos, de la dosis y vía de administración de ellos, del sitio de la infección, la severidad de la enfermedad y la presencia de condiciones subyacentes. Las recomendaciones actuales de tratamiento son empíricas o están basadas en estudios retrospectivos y por lo tanto, se necesitan estudios prospectivos adecuados que puedan proveer una información más fundamentada

Patrón de susceptibilidad a los antimicrobianos de cepas de enterococos / Pattern of antimicrobial susceptibility of enterococci strains

Enterococci resistance to antimicrobials has increased lately. We studied the susceptibility to 12 antimicrobials of 150 enterococci strains coming from hospitalized and outpatients, using the agar dilution method. Teicoplanin, followed by imipenem and amoxicilin-clavulanic acid had the lower minimal inhibitory concentrations. No strains of E faecalis was resistant to ampicillin, whereas 14 percent of E faecium had minimal inhibitory concentrations over 8 µg/ml. The high minimal inhibitory concentrations of cefpirone (64µg/ml) renders this antimicrobial useless in the treatment of enterococcal infections. Betalactamase production and resistance to glycopeptides were not detected. Antimicrobial susceptibility of strains coming for hospitalized or outpatients were similar

Effect of pH and human serum on the in-vitro activity of B-lactam and aminoglycoside combinations

The effect of three pH values [5.8, 7.4, and 8.0] and human serum on the activity of ampicillin, cefazolin, and cefotaxime alone and in combination with four aminoglycoside antibiotics [streptomycin, tobramycin, gentamicin, and amikacin] against sensitive and resistant strains of Staphylococcus aureus and Pseudomonas aeruginosa was evaluated. The change of pH from 5.8 to 8 noticeably affected the activity of all studied combinations. In general, the five B-lactam aminoglycoside combinations were more active at alkaline pH [pH 8]. However, pH shift towards the acidic side [pH 5.8] decreased their activity and increased their FIC indices. Addition of human serum decreased the in vitro antibacterial activity of B-lactam and aminoglycoside antibiotics, as well as their combinations against the used strains. The degree of influence was related to the ability of each antibiotic to bind with serum albumin. Cefazolin/streptomycin and cefazolin/tobramycin combinations showed the highest degree of protein binding effect

Postantibiotic effect of gentamicin alone and in combination with ciprofloxacin and piperacillin on escherichia coli

The in-vitro post-antibiotic effect [PAE] of gentamicin alone and in combination with piperacillin or ciprofloxacin on 5 clinical isolates of Escherichia coli was evaluated using viable count technique. Gentamicin, piperacillin and ciprofloxacin alone induced a short PAEs on E. coli [1.1h, 1.2 h and 2.6 h, respectively]. At most concentrations, the combination of gentamicin with piperacillin or ciprofloxacin induced longer PAEs on E. coli than the sum of the individual antibiotics PAEs [6.2 h and 6.9 h, respectively]. Addition of gentamicin or ciprofloxacin during the post-antibiotic phase of the piperacillin showed a more consistent bactericidal combination of piperacillin with gentamicin than that of piperacillin with ciprofloxacin