RESUMEN
One method of making optimal use of prophylactic antibiotics is for interested parties to agree on guidelines. A postal survey was undertaken to determine the prevalence of this practice within UK hospitals and details of any guidelines used. Eighty-one of the 160 respondents (51%) stated that guidelines were available or in preparation. Prophylaxis was recommended by 100% of respondents for colorectal surgery and prosthetic joint replacement and by 96% for gastro-oesophageal surgery, procedures where it has been proven to be of benefit. Prophylaxis was recommended for the following procedures for which its efficacy remains controversial: cholecystectomy (100%); peripheral vascular grafting (93%); hysterectomy (95%) and noncardiac thoracic surgery (63%). Although 35 combinations of 22 different antimicrobials were recommended, 63% included a cephalosporin; the greatest variety of antibiotics recommended was for peripheral vascular grafting. In 88% of policies it was advocated that prophylaxis be started preoperatively and in 79% that it be continued for less than 24 h. When surgery involved the implantation of a prosthesis the duration of prophylaxis tended to be prolonged. Policies for the prescribing of antimicrobial prophylaxis in surgery are available in many hospitals and for the most part conform with established principles.
Asunto(s)
Antibacterianos/uso terapéutico , Premedicación/estadística & datos numéricos , Cuidados Preoperatorios/normas , Infección de la Herida Quirúrgica/prevención & control , Antibacterianos/administración & dosificación , Humanos , Guías de Práctica Clínica como Asunto , Premedicación/normas , Encuestas y Cuestionarios , Reino UnidoRESUMEN
Mutants have been isolated which lack NADH-dependent nitrite reductase activity but retain NADPH-dependent sulphite reductase and formate hydrogenlyase activities. These NirB- strains synthesize cytochrome c552 and grow normally on anaerobic glycerol-fumarate plates. The defects map in a gene, nirB, which is extremely close to cysG, the gene order being crp, nirB, cysG, aroB. Complementation studies established that nirB+ and cysG+ can be expressed independently. The data strongly suggest that nirB is the structural gene for the 88 kDal NADH-dependent nitrite oxidoreductase apoprotein (EC 1.6.6.4). The nirB gene is apparently defective in the previously described nirD mutant, LCB82. The nirH mutant, LCB197, was unable to use formate as electron donor for nitrite reduction, but NADH-dependent nitrite reductase was extremely active in this strain and a normal content of cytochrome c552 was detected. Strains carrying a nirE, nirF or nirG mutation gave normal rates of nitrite reduction by glucose, formate or NADH.
Asunto(s)
Escherichia coli/enzimología , NADH NADPH Oxidorreductasas/metabolismo , Nitrito Reductasas/metabolismo , Mapeo Cromosómico , Escherichia coli/genética , Genes Bacterianos , Ligamiento Genético , Mutación , Nitrito-Reductasa (NAD(P)H) , Nitrito Reductasas/genética , Análisis Espectral , Temperatura , Transducción GenéticaRESUMEN
Pyruvate and ethanol were both effective electron donors for nitrite reduction by Escherichia coli K12. The pyruvate-dependent rate decreased by approximately 50% when either a cysG mutation, which results in loss of NADH-dependent nitrite reductase activity (EC 1.6.6.4), or a chl mutation, which results in loss of the formate-nitrite oxidoreductase activity, was introduced into the prototrophic parental strain CGSC4315. A double mutant deficient in both of these previously described activities retained only 2% of the rate of nitrite reduction of the parental strain after growth on glucose or 5% after growth on pyruvate. We conclude that any third pathway for nitrite reduction contributes little to the in vivo rate of nitrite reduction by wild-type strains.
Asunto(s)
Escherichia coli/metabolismo , Etanol/metabolismo , Nitritos/metabolismo , Piruvatos/metabolismo , Escherichia coli/enzimología , Glucosa/metabolismo , Oxidación-ReducciónRESUMEN
A set of four isogenic Escherichia coli strains has been constructed in which all possible combinations of NADH- and formate-dependent nitrite reductases are active or inactive. Each pathway can be inactivated genetically without a corresponding loss in the other activity: the two pathways are therefore biochemically independent. The generation of a membrane potential during nitrite reduction by formate has been demonstrated using an ion-selective electrode specific for a lipophilic cation. The observed energy conservation results, at least in part, from the ability of formate dehydrogenase in E. coli to pump protons.