Different microbial biofilm formation on polymethylmethacrylate (PMMA) bone cement loaded with gentamicin and vancomycin.

We studied the in vitro effects of gentamicin and vancomycin alone and in combination added to polymethylmethacrylate (PMMA) cement specimens on the bacterial adhesion of multiresistant clinical isolates. The PMMA specimens (discs) loaded with gentamicin (1.9%) or vancomycin (1.9%) or with a combination of the two were placed in Mueller-Hinton Broth inoculated with bacterial strains. After incubation, bacterial growth was determined by optical density (OD(540)) and sub-cultures. The biofilm PMMA-associated dye (crystal violet) was measured. Antibiotic concentrations in broth were determined by fluorescence polarisation immunoassay. All antibiotic-loaded PMMA cement specimens released high, inhibitory concentrations of gentamicin and vancomycin. However, differences in strain growth and adhesion were recorded. The clinical isolates Met-R/Gent-R CoNS showed no adhesion to gentamicin-loaded specimens for 24 h; strains with Gent-Intermediate susceptibility exhibited growth after 48 h but reduced adhesion. Some Gent-R strains exhibited growth and adhesion to antibiotic-loaded specimens similar to controls (plain discs). Only the VRSA strain (Staphylococcus aureus 5/7) and Escherichia coli were able to grow and adhere to vancomycin-loaded specimens after 24 h of incubation. The specimens loaded with the gentamicin + vancomycin combination showed a synergistic inhibitory effect against all tested strains (no bacterial growth). The degree of bacterial adhesion to PMMA cement loaded with gentamicin or vancomycin may be reduced in spite of a normal growth rate and is different for the tested strains. The effect of gentamicin and vancomycin on bacterial growth and adhesion to PMMA bone cement depends on the antibiotic concentrations, on the characteristics of each specific strain and on its ability to produce biofilm and adhere to antibiotic-loaded PMMA bone cement.

The Charta of Milan: basic criteria for the appropriate and accurate use of antibiotics: recommendations of the Italian Society of Chemotherapy.

This article summarizes the recommendations drawn up by the Italian Society of Chemotherapy regarding the proper use of antimicrobial agents for infectious diseases.

Release of gentamicin and vancomycin from temporary human hip spacers in two-stage revision of infected arthroplasty.

AIM: Evaluation of the delivery of gentamicin and vancomycin from polymethylmethacrylate (PMMA) spacers before and after implantation for the treatment of total hip replacement infections. METHODS: Twenty industrially produced spacers containing gentamicin (1.9%) were utilized. Vancomycin (2.5%) mixed with PMMA cement was used to fill holes drilled in the cement of 14 of the 20 spacers immediately before implantation. The spacers were removed from 20 patients 3-6 months after implantation and then immersed in phosphate buffer at 37 degrees C for 10 days. Antibiotic concentrations were determined by fluorescence polarization immunoassay. RESULTS: Gentamicin and vancomycin were still present in all the spacers removed from the patients. The release of gentamicin alone and in combination with vancomycin was in the range 0.05%-0.4% of the initial amount present, whereas the release of vancomycin was in the range 0.8%-3.3%. The release kinetics showed a similar pattern for both drugs. After a high initial release of drug, a reduced, but constant, elution was observed over the next few days. CONCLUSIONS: The delivery of gentamicin and vancomycin from PMMA cement was high initially, with sustained release over several months. Incorporation of vancomycin into the surface of the spacers permitted spacers to be prepared with multiple antibiotics present and without adversely affecting the release kinetics of the agents. The gentamicin-vancomycin combination shows potential for the treatment of infection following total hip replacement in specific patients.

Release of antibiotics from polymethylmethacrylate cement.

The increase in resistance rates to antibiotics of bacteria isolated from infected hip joints, particularly staphylococci, prompted us to investigate the usefulness of antibiotic combinations such as gentamicin plus vancomycin. Cylinder test specimens of polymethylmethacrylate (PMMA) cement (Cemex, Tecres) containing gentamicin alone, vancomycin alone and both drugs in combination, were studied. The antibiotic concentrations were determined using a microbiological method and fluorescence polarization immunoassay (FPIA). The release of gentamicin alone, vancomycin alone and in combination from PMMA cement was prompt. The combination revealed synergistic antimicrobial activity against Escherichia coli and Enterococcus faecalis. FPIA showed that gentamicin and vancomycin delivery rates from PMMA cement were different. Gentamicin alone and in combination with vancomycin presented similar release rates from PMMA cement (1.50%). Vancomycin release from PMMA cylinders impregnated with the combination was lower (0.51%) than that from cylinders with vancomycin alone (1.16%). Vancomycin showed a 34.1% loss of microbiological activity at 37 degrees C after 10 days of incubation; the reduction corresponded to 15.0% when measured by FPIA. Results obtained with test specimens are indicative for the preparation of antibiotic-impregnated cements for different human prostheses.

The intestinal ecosystem in chronic functional constipation.

Chronic functional constipation is common in infants, and the bacterial composition of stools in this condition is not known. The study aims were to: (i) investigate the composition of the intestinal ecosystem in chronic functional constipation; (ii) establish whether the addition of the water-holding agent calcium polycarbophil to the diet induces an improvement in constipation; and (iii) determine the composition of the intestinal ecosystem after the use of this agent. In total, 42 children (20F, 22M; mean age: 8.6 +/- 2.9 y) were studied. Twenty-eight children with functional chronic constipation without anatomical disorders were treated double-blind in random sequence for 1 month with an oral preparation of calcium polycarbophil (0.62 g/twice daily) or placebo. Intestinal flora composition was evaluated by standard microbiological methods and biochemical assays on faecal samples collected before and after treatment. Fourteen healthy children were studied as controls. The results show that (i) the constipated children presented a significant increase in clostridia and bifidobacteria in faeces compared to healthy subjects--different species of clostridia and enterobacteriaceae were frequently isolated; no generalized overgrowth was observed; Clostridia outnumbered bacteroides and E. coli mean counts by 2-3log, while bacteroides and E. coli counts were similar (5-6 log10/g fresh faeces); these intestinal disturbances could be defined as a dysbiosis, i.e. a quantitative alteration in the relative proportions of certain intestinal bacterial species. (ii) Clinical resolution of constipation was achieved only in 43% of treated children and an improvement in 21% (one bowel movement every 2 d). (iii) Calcium polycarbophil treatment induced no significant changes in the composition of the intestinal ecosystem, nor in blood chemistry parameters.

Pefloxacin penetration into human necrotic pancreatic tissue.

Antibiotic prophylaxis may be useful in acute necrotising pancreatis, a disease associated with a considerable incidence of infectious complications. The aim of this study was to assess pefloxacin penetration into necrotic pancreatic tissue during human necrotic pancreatitis. Ten patients (mean age 53.2 +/- 17.4 years) with severe acute pancreatitis (mean Ranson score 4.3) were studied. Pefloxacin was administered at a dose of 400 mg bd every 12 h by i.v. infusion (bolus, 15 min). Intraoperative samples of necrotic pancreatic tissue and blood were collected simultaneously 1, 2, 4.5, 6, 8.5 or 10 h after the last pefloxacin administration in patients treated for 1, 3, 4, 7, 8, 17 or 20 days. Drug concentrations were determined by the microbiological agar-well diffusion method (Escherichia coli Kp 05124 as test micro-organism in Isosensitest Agar). Levels in serum ranged from 2.0 to 9.0 mg/L (at 2 and 6 h, respectively), in necrotic pancreatic tissue from 2.0 to 29.0 micrograms/g depending on different sampling time. Maximum tissue peak concentrations appeared between 4 and 6 h. The necrotic pancreatic tissue/serum concentration ratio ranged from 0.9 to 5.1, values depending on tissue sample collection. Therapeutic concentrations (20.6 micrograms/g) above the MIC of potentially pathogenic enteric microorganisms were still present in necrotic pancreatic tissue 10 h after the last drug administration. Pefloxacin appeared to concentrate in necrotic pancreatic tissue, without appreciable accumulation after multiple-dose administration. The pefloxacin concentrations in necrotic pancreatic tissue showed high variability, depending on the degree of necrosis, inflammation and sample vascularization. Our results provided evidence of good, prompt penetration of pefloxacin into necrotic pancreatic tissue. Pefloxacin seems to exhibit favourable pharmacokinetic and pharmacodynamic properties for pancreatic infections.

Twice-weekly dapsone for primary prophylaxis against Pneumocystis carinii pneumonia in HIV-1 infection: efficacy, safety and pharmacokinetic data.

OBJECTIVES: In this study we evaluated the pharmacokinetics, efficacy and safety of dapsone given 100 mg twice weekly as primary prophylaxis against Pneumocystis carinii pneumonia (PCP) in patients with HIV-1 infection. METHODS: This was a prospective open trial, evaluating a total of 55 HIV-1-infected patients with CD4 cell counts below 200/mm3 and without previous episodes of PCP. Plasma concentrations of dapsone were determined with high-performance liquid chromatography (HPLC). After a mean follow-up of 471 days, the PCP rates per year of observation were 6.79%. Discontinuation of treatment as a result of severe side effects was required in four patients (7.5%). At steady state, mean plasma concentrations 24, 72, 96 and 144 h following the administration of dapsone were 1.46plus minus0.8, 0.28plus minus0.20, 0.30plus minus0.21 and 0.37plus minus0.27 mg/L, respectively. Dapsone plasma levels showed a high interpatient variability. The values for the pharmacokinetic parameters were comparable to those described for healthy volunteers. CONCLUSIONS: The administration of 100 mg twice weekly of dapsone seems appropriate to maintain effective plasma concentrations of the drug and to prevent PCP with good safety in patients with HIV-1-related immunodeficiency.

Enhancement of antibiotic antibacterial activity by experimental pleural exudates.

The aim of this research was to study the synergistic effect of experimental pleural exudates and antimicrobial drugs on various microorganisms. The antibacterial activity of different pleural exudates alone and in the presence of sub-MIC amounts of antibiotics was studied by a continuous recording turbidimetric method. Synergistic action between the antibiotics and the exudates was demonstrated. This phenomenon can be explained by the presence of heat-labile substances that themselves possess only slight antibacterial activity but are able to increase the effect of sub-MIC antibacterial drugs.