Frecuencia de enzimas asociadas a sensibilidad disminuida a betalactámicos en aislados de enterobacterias, Caracas, Venezuela / Frequency of enzymes associated with reduced sensitivity to beta-lactamantibiotics in enterobacteria isolates, Caracas, Venezuela

Objective. To determine the frequency of enzymatic mechanisms associated with reduced sensitivity to broad-spectrum beta-lactam antibiotics in enterobacteria isolates obtained at hospital centers in Caracas, Venezuela.Methods. A cross-sectional study was conducted on enterobacteria isolated from patients at eight hospital centers in Caracas, Venezuela, from 15 October 2009 to 15 January 2010. The species were identified using conventional biochemical tests, and their susceptibility to antimicrobial drugs was assessed by antibiogram (Kirby-Bauer method), using the 2010 performance standards published by the Clinical and Laboratory Standards Institute. Beta-lactam-resistant genes were detected using an enhanced polymerase chain reaction assay.Results. Of 1 235 isolates, 207 (16.8%) exhibited resistance to third- and fourthgeneration cephalosporins, carbapenems, or both. They presented the following phenotypes: extended-spectrum beta-lactamase (ESBL), 93.8%; depressed AmpC, 4.3%; and carbapenemase, 1.9%. Further characterization of the first two phenotypes yielded the following breakdown of types: SHV, 36.7%; CTX-M-1 group, 22.3%; TEM, 21.7%; CTX-M-1 group with impermeability, 5.2%; two-enzyme combinations, 4.5%;CTX-M-2 group, 4.3%; PER, 3.4%; and KPC, 1.9%. The SHV type was predominant in the public hospital strains, whereas the CTX-M-1 group was most common in the strains from the private hospitals. Conclusions. Of the enzymatic mechanisms investigated, the SHV type was the most frequent, followed by the CTX-M-1 group and the TEM type. Also, a high percentageof type KPC was found. The research reported here is one of only a few multicenter studies that have been conducted in Venezuela to evaluate the frequency of this type of antimicrobial resistance mechanism, including phenotypical and molecular characterization...

Objetivo. Determinar la frecuencia de los mecanismos enzimáticos asociados a sensibilidad disminuida a los antibióticos betalactámicos de amplio espectro en aislados de enterobacteriasobtenidos de centros hospitalarios de Caracas, Venezuela. Métodos. Se realizó un estudio transversal con enterobacterias aisladas de pacientes de ocho centros hospitalarios de Caracas, Venezuela, desde el 15 de octubre de 2009 al 15 de enero de2010. La identificación se realizó mediante pruebas bioquímicas convencionales, y la susceptibilidada los antimicrobianos mediante antibiograma (Kirby-Bauer), según las normas de 2010 del Instituto de Estándares Clínicos y de Laboratorio. La detección de los genes de resistenciaa betalactámicos se realizó mediante amplificación por reacción en cadena de polimerasa. Resultados. De 1 235 aislados, 207 (16,8%) mostraron resistencia a cefalosporinas de terceray cuarta generación o a carbapenemes o a ambos. De esos, 93,8% presentaron fenotipo betalactamasa de espectro extendido (BLEE); 4,3%, fenotipo AmpC derreprimido, y 1,9%, fenotipocarbapenemasa. La caracterización de los dos primeros fenotipos determinó que 36,7% eran tipo SHV; 22,3%, grupo CTX-M-1; 21,7%, tipo TEM; 5,2%, grupo CTX-M-1 + impermeabilidad; 4,5%, combinación de dos enzimas; 4,3%, grupo CTX-M-2; 3,4%, tipo PER, y 1,9%, tipo KPC.Se observó un predominio del tipo SHV en las cepas obtenidas de hospitales públicos y del grupo CTX-M-1, en los privados. Conclusiones. De los mecanismos enzimáticos investigados, el tipo SHV fue el más frecuente,seguido del grupo CTX-M-1 y tipo TEM. Asimismo, se encontró un alto porcentaje de carbapenemasas tipo KPC. Este es uno de los pocos estudios multicéntricos realizados enVenezuela donde se evalúa la frecuencia de este tipo de mecanismo de resistencia a los antimicrobianos,incluida la caracterización fenotípica y molecular...

An insight into the drug resistance profile & mechanism of drug resistance in Neisseria gonorrhoeae.

Among the aetiological agents of treatable sexually transmitted diseases (STDs), Neissseria gonorrhoeae is considered to be most important because of emerging antibiotic resistant strains that compromise the effectiveness of treatment of the disease - gonorrhoea. In most of the developing countries, treatment of gonorrhoea relies mainly on syndromic management rather than the aetiological based therapy. Gonococcal infections are usually treated with single-dose therapy with an agent found to cure > 95 per cent of cases. Unfortunately during the last few decades, N. gonorrhoeae has developed resistance not only to less expensive antimicrobials such as sulphonamides, penicillin and tetracyclines but also to fluoroquinolones. The resistance trend of N. gonorrhoeae towards these antimicrobials can be categorised into pre-quinolone, quinolone and post-quinolone era. Among the antimicrobials available so far, only the third-generation cephalosporins could be safely recommended as first-line therapy for gonorrhoea globally. However, resistance to oral third-generation cephalosporins has also started emerging in some countries. Therefore, it has become imperative to initiate sustained national and international efforts to reduce infection and misuse of antibiotics so as to prevent further emergence and spread of antimicrobial resistance. It is necessary not only to monitor drug resistance and optimise treatment regimens, but also to gain insight into how gonococcus develops drug resistance. Knowledge of mechanism of resistance would help us to devise methods to prevent the occurrence of drug resistance against existing and new drugs. Such studies could also help in finding out new drug targets in N. gonorrhoeae and also a possibility of identification of new drugs for treating gonorrhoea.

Purification and characterization of extracellular penicillin V acylase from Fusarium sp. SKF 235.

Penicillin V acylase from Fusarium sp. SKF 235 culture filtrate was purified to homogeneity. The enzyme was a glycoprotein and composed of single polypeptide chain with molecular weight of 83,200 Daltons. The pH and temperature optima were 6.5 and 55 degrees C, respectively. The KM for penicillin V was 10 mM but the enzyme was inhibited by penicillin V at concentrations above 50 mM. Products of reaction, 6-aminopenicillanic acid and phenoxyacetic acid inhibited the enzyme competitively and noncompetitively with Ki values of 18 mM and 45 mM, respectively. The enzyme specifically hydrolyzed penicillin V, cephalosporanic acid V and penicillin V sulphoxide. Other phenoxy acetyl amides studied were not hydrolysed. It is proposed that phenoxyacetyl moiety alone is not recognized by the penicillin V acylase and in addition, the beta-lactam structure contributes in formation of enzyme-substrate complex.

Actualizacion: nuevas cefalosporinas de administracion oral / Update about the oral route of new cephalosporines

Las cefalosporinas son antibioticos betalactamicos, químicamente derivados del ácido 7 amido cefalosporánico, que se halla compuesto de un anillo de dihidrotiazina y uno betalactámico. El mecanismo de acción es parecido al de las penicilinas, diferenciadose, sin embargo, en su espectro antibacteriano, la resistencia a las betalactamasas y en la farmacocinética. Las cefalosporinas se claasifican, generalmente, en cefalosporinas de I, II, II y IV generación. Desde un punto de vista práctico, se define como generación a la actividad de la droga in vitro contra bacterias gram (-).

Aspectos farmacológicos das cefalosporinas / Pharmacologic aspects of cephalosporine

Cefalosporinas säo antibióticos betalactâmicos com amplo espectro de atividade e relativamente pouco tóxico. A primeira geraçäo de cefalospsorinas é a mais ativa contra estafilococos e estreptococos sensíveis, mas näo possuem boa atividade contra bacilos gram-negativos (exceto Klehsiella, E. colli e P. mirabilis). A segunda geraçäo de cefalosporinas amplia a sua atividade para H. influenzae e anaeróbios. Finalmente, a terceira geraçäo atua preponderantemente contra Enterobacteriaceae e H. influenzae, mas säo os menos efetivas contra cocos gram-positivos. Este espectro antibacteriano, combinado com suas excelentes propriedades farmacocinéticas e baixa toxicidade, sugere que estas drogas podem ser utilizadas em diversas situaçöes clínicas. A terceira geraçäo näo deve ser usada para tratar infecçöes que possam ser efetivamente curadas com antibióticos mais baratos e menos tóxicos

Enzymatic hydrolysis of 7-phenylacetamidodesacetoxycephalosporanic acid by immobilized penicillin G acylase.

Enzymatic parameters such as pH, temperature and substrate concentration were studied for the hydrolysis of 7-PADCA by penicillin G acylase. Optimum pH and temperature were 8.0 and 50 degrees C, respectively. Km value of soluble and immobilized enzyme for 7-PADCA was 2.3 x 10(-5) M and 7.5 x 10(-5) M, respectively. At 7-PADCA concentration of 5% and an IME: 7-PADCA ratio of 1:2.5, the hydrolysis was complete in 110 min.

Dx de laboratorio de estreptococos (Lancefield C y G) / Laboratory diagnosis of streptococcus (Lancefield C and G)

La presencia de microrganismos en un líquido corporal normalmente estéril como la sangre, puede representar la evidencia de una infección activa que tiene el riesgo de propagarse a otros órganos o tejidos de la economía; por ésto, el laboratorio de microbiología clínica cumple una función muy importante en el diagnóstico, al aislar a los agentes causales mediante hemocultivos