11. Inhibitors of bacterial cell wall synthesis MCBL Enfermería 30/01/12 Cell wall Attachment of new wall unit to growing peptidoglycan UDP L- lysine D- ala Beta-lactams Bind to and inhibit enzymes which catalyse this link NAG NAM NAG NAM
23. MCBL Enfermería 30/01/12 ACTIVIDAD ANTIMICROBIANA IN VITRO 1.- Determinar la potencia de un antimicrobiano en solución. 2.- Determinar la concentraciónen los líquidos o tejidos del cuerpo. 3.- Determinar la susceptibilidad de un microorganismo a las concentraciones conocidas de un antimicrobiano.
24. MCBL Enfermería 30/01/12 MEDICION DE LA ACTIVIDAD ANTIMICROBIANA IN VITRO: antibiogramas 1.- METODO DE DILUCION: cuantitativo 2.- METODO DE DIFUSION: cualitativo
29. MCBL Enfermería 30/01/12 Tabla 1. actividad antimicrobiana de cefalosporinas de diferente generación frente a una especie de bacilos Gram negativos ( E. coli ) y una especie de Cocáceas Gram positivas ( S. pneumoniae ) Compuesto y generación de cefalosporina E. coli CIM 90 μ g/mL S. pneumoniae CIM 90 μ g/mL Primera generación Cefazolina 16 0,12 Segunda generación Cefuroxime 8 0,06 Tercera generación Cefotaxima 0,12 0,06 Ceftriaxona 0,25 0,5 Ceftazidima 0,25 0,25 Cuarta generación Cefepime 0,06 0,12
30.
31.
32.
33.
34.
35.
36.
37.
38.
39.
40.
41.
Notas del editor
The beta-lactams comprise a large family of groups of compounds that all contain a beta-lactam ring. They include the penicillins, cephalosporins, carbapenems (e.g. imipenem) ,monobactams (aztreonam), and cephamycins that bind to and inhibit the enzyme, the penicillin binding protein, that catalyse the link between L-lysine and D-alanine. This group of antibiotics is shown in the next slide.
Vancomycin is a fermentation product of an actinomycete. It has a large complex structure and its antibacterial activity is largely restricted to Gram positive organisms. It is bactericidal against most, but against Enterococcus and some viridans streptococci it is bacteriostatic. Vancomycin is poorly absorbed from the GI tract. It doesn’t readily cross the blood brain barrier. It is excreted renally. Rapid IV administration can give rise to release of histamine from basophils and mast cells and gives rise to the ‘red-neck’ syndrome with pruritus, flushing, angio-oedema and, rarely cardiovascular collapse. It can cause nephrotoxicity and ototoxicity – drug levels need monitoring. Oral vancomycin is used to treat pseudomembranous colitis and staphylococcal enterocolitis. Teicoplanin doesn’t cause red neck syndrome; it has the advantage of less frequent dosing (once or twice daily versus qds) + less potential for oto- and nephrotoxicity.