The exocellular DD-carboxypeptidase-endopeptidase of Streptomyces albus G. Interaction with beta-lactam antibiotics.
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Kinetically, the three-step model proposed for the interaction between beta-lactam antibiotics and the exocellular DD-carboxypeptidases-transpeptidases of Streptomyces R61 and Actinomadura R39 [Frere, Ghuysen & Iwatsubo (1975) Eur. J. Biochem. 57, 343--357; Fuad, Frere, Ghuysen, Duez & Iwatsubo (1976) Biochem. J. 155, 623--629] applies to the interaction between the much less penicillin-sensitive exocellular DD-carboxypeptidase-endopeptidase of Streptomyces albus G and at least phenoxymethylpenicillin, cephalothin and cephalosporin C. The penicillin resistance of the albus G enzyme is mainly due to the low efficiency with which the first reversible complex formed with the antibiotic (complex EI) undergoes transformation into a second more stable complex EI*. Analysis of the ternary interaction between enzyme, NalphaNepsilon-diacetyl-L-lysyl-D-alanyl-D-alanine (Ac2-L-Lys-D-Ala-D-Ala) and cephalosporin C indicates a non-competitive mechanism. (+info)
Penicillin for acute sore throat: randomised double blind trial of seven days versus three days treatment or placebo in adults.
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OBJECTIVE: To assess whether treatment with penicillin for three days and the traditional treatment for seven days were equally as effective at accelerating resolution of symptoms in patients with sore throat compared with placebo. DESIGN: Randomised double blind placebo controlled trial. SETTING: 43 family practices in the Netherlands. PARTICIPANTS: 561 patients, aged 15-60 years, with sore throat for less than seven days and at least three of the four Centor criteria-that is, history of fever, absence of cough, swollen tender anterior cervical lymph nodes, and tonsillar exudate. 142 patients were excluded for medical reasons and 73 needed penicillin. INTERVENTIONS: Patients were randomly assigned to penicillin V for seven days, penicillin V for three days followed by placebo for four days, or placebo for seven days. MAIN OUTCOME MEASURES: Resolution of symptoms in the first week, eradication of bacteria after two weeks, and recurrences of sore throat after two, four, and six months. RESULTS: Symptoms resolved 1.9 and 1.7 days earlier in patients taking penicillin for seven days than in those taking penicillin for three days or placebo respectively. Symptoms resolved 2.5 days earlier in patients with group A streptococci and 1.3 days earlier in patients with high colony counts of non-group A streptococci. 23 (13%) of the placebo group had to be given antibiotics later in the week because of clinical deterioration; three developed a peritonsillar abscess. The eradication rate for group A streptococci was 72% in the seven day penicillin group, 41% in the three day penicillin group, and 7% in the placebo group. Sore throat recurred more often in the three day penicillin group than in the seven day penicillin or placebo groups. CONCLUSION: Penicillin treatment for seven days was superior to treatment for three days or placebo in resolving symptoms of sore throat in patients with group A streptococcal pharyngitis and, possibly, in those with non-group A streptococcal pharyngitis. (+info)
Comparison of short-course (5 day) cefuroxime axetil with a standard 10 day oral penicillin V regimen in the treatment of tonsillopharyngitis.
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Oral penicillin V given three times daily in doses of 50,000-100,000 IU daily has been the standard treatment for tonsillopharyngitis for the last few decades. These regimens, initially recommended by the American Heart Association, were extrapolated from i.v. dosing with long-acting forms of penicillin which had been shown to prevent post-streptococcal sequelae. More recently, several antibiotics, including cefuroxime axetil, have been shown to be at least as effective as penicillin G in eradicating group A beta-haemolytic streptococci (GABHS) but their influence on post-streptococcal sequelae has never been assessed in a large-scale trial. The German Society for Pediatric Infectious Diseases (DGPI) undertook a large study of culture-proven tonsillopharyngitis involving several agents and included a 1 year follow-up to establish the effect on sequelae. In one arm of this study, cefuroxime 250 mg bid was compared with 50,000 IU penicillin V given in three divided doses. Cefuroxime axetil was more effective than oral penicillin V in eradicating GABHS at the assessment 2-4 days post-treatment (441/490 (90%) patients versus 1196/1422 (84%) patients; P = 0.001). Clinically, the two agents were equivalent in efficacy, and carriage rates were similar (11.1% and 13.8%, respectively) in patients receiving cefuroxime axetil and penicillin V, 7-8 weeks post-treatment. One case of glomerular nephritis occurred in a patient given penicillin V. There were no post-streptococcal sequelae confirmed for patients treated with cefuroxime axetil. The findings confirm the previously reported efficacy of short-course (4-5 day) treatments with cefuroxime axetil and indicate that short-course treatment is comparable to the standard oral penicillin V regimen in preventing post-streptococcal sequelae. (+info)
Excretion of beta-lactam antibiotics in sweat--a neglected mechanism for development of antibiotic resistance?
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The concentrations of beta-lactam antibiotics after standard doses were measured in blood and apocrine (axilla) and eccrine (forearm) sweat from six adult healthy persons. All persons had ceftazidime (axilla, 28.4 microg/ml; forearm, 11 microg/ml) and ceftriaxone (axilla, 8.9 microg/ml; forearm, 2.5 microg/ml) in sweat, and one person had cefuroxime in sweat (axilla, 7.8 microg/ml) (all data are mean peaks). Three persons had benzylpenicillin (axilla, 2.6 to 0.1 microg/ml) and one had phenoxymethylpenicillin (axilla, 0.4 microg/ml) in sweat. Excretion of beta-lactam antibiotics in the sweat may explain why staphylococci so rapidly become resistant to these drugs. (+info)
Effect of recolonisation with "interfering" alpha streptococci on recurrences of acute and secretory otitis media in children: randomised placebo controlled trial.
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OBJECTIVE: To study the effect of recolonisation with alpha streptococci with the ability to inhibit the growth of otopathogens ("interfering" activity) on the recurrence of acute otitis media in susceptible children and the effect on the frequency of secretory otitis media. DESIGN: Double blind, randomised, placebo controlled study. SETTING: Ear, nose, and throat clinic with three doctors. PARTICIPANTS: 130 children prone to otitis media aged between 6 months and 6 years, 108 of whom were eligible and followed for 3 months. MAIN OUTCOME MEASURES: Recurrence of otitis media during follow up and a normal tympanic membrane at the last valid visit. INTERVENTIONS: Children with no recurrences during the last month received phenoxymethylpenicillin (n=22), and those with a recurrence within 1 month received amoxicillin clavulanic acid (n=86), both twice daily for 10 days. These were followed by a streptococcal or placebo solution sprayed into the nose for a further 10 days. At day 60 the same spray was started for another 10 days. RESULTS: At 3 months 22 children (42%) given the streptococcal spray were healthy and had a normal tympanic membrane compared with 12 (22%) of those given placebo. This difference was shown separately for recurrences of both acute otitis media and secretory otitis media. CONCLUSIONS: Selected bacteria with the ability to inhibit the growth of common otopathogens can be used to protect against recurrent acute otitis media and secretory otitis media in children. (+info)
Five day clarithromycin modified release versus 10 day penicillin V for group A streptococcal pharyngitis: a multi-centre, open-label, randomized study.
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OBJECTIVE: A multicentre, comparative, randomized, open-label, Phase III trial evaluated the efficacy and tolerability of clarithromycin modified release (MR) versus penicillin V for pharyngitis due to group A beta-haemolytic streptococci (GABHS). METHODS: Three hundred and forty-nine patients (12-40 years) with acute pharyngotonsillitis and a positive Streptococcus A antigen immunoassay test were randomized to receive clarithromycin MR 500 mg od for 5 days or penicillin 590 mg tds for 10 days. Patients were clinically evaluated and a throat swab for culture obtained before treatment, after treatment (day 8 or 13 depending on the treatment arm) and at the follow-up visit (day 30). The main criterion for efficacy was the bacteriological cure rate after treatment. RESULTS: Three hundred and forty-nine patients were considered for the intent-to-treat analysis. After treatment, clinical cure rates were 88.1% in the clarithromycin group and 92.4% in the penicillin group, and eradication rates were 82.8% and 83.6%, respectively. There were no statistically significant differences between the two treatments. Three hundred and three (87%) patients had a positive culture before treatment, among which 29 (9.7%) were found to be clarithromycin resistant. Two hundred and thirty-nine patients were clinically and bacteriologically evaluable for per protocol analysis. After treatment, clinical cure rates were 95.2% in the clarithromycin group and 97.3% in the penicillin group, and eradication rates were 94.4% and 92%, respectively. No statistically significant difference was shown. Adverse events occurred in 46 patients of the clarithromycin group and 31 of the penicillin group (with no statistical difference). Most of them were of mild or moderate severity. CONCLUSION: Clarithromycin MR administered once daily for 5 days is as safe and effective as penicillin V administered three times a day for 10 days in the treatment of GABHS pharyngitis. (+info)
Modification in penicillin-binding proteins during in vivo development of genetic competence of Haemophilus influenzae is associated with a rapid change in the physiological state of cells.
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By using whole-cell labeling assay with 125I-penicillin V, we observed a reduction in the binding of the radiolabeled beta-lactam to four or five penicillin-binding proteins (PBPs) in Haemophilus influenzae cells cultivated under specific conditions. PBPs 3A, 3B, 4, and 6 were altered after the growth of bacteria in diffusion chambers implanted in the peritoneal cavity of rats. PBP 2 was also modified when cells were cultivated in human cerebrospinal fluids. Because this observation may have important consequences on the efficacy of beta-lactams during antibiotic therapy, we characterized the physiological state of bacteria cultivated in animals in the hope of explaining how such important changes in cell properties develop in vivo. Since the development of natural genetic competence occurs at the stationary phase of growth in H. influenzae, we used a DNA transformation assay to evaluate the physiological state of bacteria grown in diffusion chambers implanted in rats. Chromosomal DNA isolated from an antibiotic-resistant donor strain was mixed with bacteria in diffusion chambers. At different times during a 5-h incubation period, recipient bacteria were collected from the chambers, CFU were determined by plate counting, and antibiotic-resistant transformants were isolated on selective plates. Genetic competence rapidly developed in cells grown in rats, and the frequency of transformation by test DNA was elevated. Electron microscopy revealed an irregular cell shape and blebs at the surface of bacteria cultivated in animals and in cerebrospinal fluids. In an attempt to induce a similar physiological state in vitro, we supplemented broth cultures with cyclic AMP or synchronized cultures by a nutritional upshift. No changes in PBPs were observed with supplemental cyclic AMP or during a single cell cycle. Finally, a reduction in the affinity of PBPs for 125I-penicillin V identical to that observed in bacteria grown in rats was observed in cells isolated from the stationary phase of growth in vitro. These results clearly indicate that H. influenzae cells grown in animals undergo a rapid change to a physiological state similar to that found in late-stationary-phase cultures in vitro. This observation indicates that the rational design of future and improved antibiotic therapy of H. influenzae infections should consider cell properties of slow-growing or latent bacteria. (+info)
Molecular basis of the efficacy of cefaclor against Haemophilus influenzae.
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Cefaclor sustained its inhibitory activity against a beta-lactamase-producing strain of Haemophilus influenzae. Although a relatively high permeability coefficient was calculated for ampicillin compared with that calculated for cefaclor, the resulting periplasmic concentration of cefaclor was 5.7 times that of ampicillin. The efficacy of cefaclor may be due to its higher beta-lactamase resistance, which allows it to achieve a greater periplasmic concentration and adequate binding to crucial penicillin-binding proteins. (+info)