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In January 1996 the emergence of penicillin-susceptible, multiresistant serotype 6B Streptococcus pneumoniae isolates resistant to chloramphenicol, tetracycline, erythromycin, clindamycin and trimethoprim-sulfamethoxazole was observed in young carriers in the city of Patras, located in the southwestern region of Greece. Later, a significant spread of pneumococci with this unusual phenotype was noted in carriers living in various other areas of the country. Using restriction fragment length polymorphism of the ribosomal RNA genes, clonal relationships were found between these Greek strains and serotype 6B penicillin-susceptible, multiresistant pneumococci isolated in France between January 1992 and September 1996. The French and Greek isolates appear to have a common ancestry. [ABSTRACT FROM AUTHOR]

In the evaluation of treatment failure in group A streptococcal pharyngitis, it is essential to distinguish persistence or relapse with homologous streptococcal strains from the acquisition of new, unrelated strains. Randomly amplified polymorphic DNA analysis and restriction fragment length polymorphism analysis of total DNA were used as epidemiological tools to compare 122 pre- and post-treatment Streptococcus pyogenes isolates obtained from 61 patients. The results obtained by molecular typing showed that bacteriological failures were due to the original strains in 43 cases (70%) and to new strains in 18 cases (30%). In the present study, restriction fragment length polymorphism analysis of total DNA appeared to be more discriminative than randomly amplified polymorphic DNA analysis. Thus, molecular analysis of DNA is an effective way to distinguish recurrence from persistence or relapse and will be useful in assessing the efficacy of new antibiotic treatments. [ABSTRACT FROM AUTHOR]

Time-kill kinetic studies were used to measure the bactericidal activity of amoxicillin/clavulanic acid (in a new form for pediatric use), cefaclor, cefuroxime, cefixime and erythromycin against 30 beta-lactamase producing Moraxella catarrhalis strains. Antibiotics were tested at the mean maximum serum concentration observed after administration of a standard dose and at 0.5 × Cmax, 0.33 × Cmax and 0.25 × Cmax. A 2 log10 reduction in colony counts was obtained with the Cmax of amoxicillin/clavulanic acid and cefixime after 5 h of incubation. After 24 h of incubation a decrease of 3 and 4 log was observed with cefixime and amoxicillin/clavulanic acid respectively. At 0.5 × Cmax and 0.33 × Cmax, bactericidal activity was obtained only with amoxicillin/clavulanic acid. [ABSTRACT FROM AUTHOR]

A combination of esterase electrophoretic typing and analysis of the restriction fragment length polymorphism of ribosomal DNA regions (ribotyping) was used to compare 27 Pseudomonas aeruginosa strains isolated before and after two-week courses of anti-pseudomonal treatment in seven cystic fibrosis patients. A total of 12 courses of therapy were studied in which ciprofloxacin, ceftazidime, azlocillin or imipenem were used alone or in combination with tobramycin. Isolates at a count of ≥ 10 cfu/ml of sputum were collected when there was evidence of therapeutic failure on the basis of persistence of isolates whether or not they were resistant to the antibiotic used for therapy. Emergence of resistance was observed in ten cases and failure to eradicate sensitive strains in five cases. Among the 27 isolates, eight zymotypes and five ribotypes were identified. With this typing approach, resistant post-therapy isolates were found to be identical to pre-therapy isolates in all cases but one. However, in one case an additional resistant strain was isolated after therapy besides that initially present. In all five cases in which susceptibility was still observed after treatment, pretherapy and post-therapy isolates were indistinguishable. Using this molecular typing approach, all the strains were typable. Thus combination of esterase typing and ribotyping should improve the analysis of therapeutic failure in cystic fibrosis patients. [ABSTRACT FROM AUTHOR]

A dynamic in vitro model was used to determine the killing kinetics of daptomycin against 15 vancomycin-resistant clinical isolates of Enterococcus faecium. Concentration profiles simulating those observed in serum following administration of both low-dose (2 mg/kg) and high-dose (6 mg/kg) daptomycin were bactericidal within 5.5 and 2.8 h, respectively. In contrast, when albumin was added to the growth medium, the corresponding bacterial killing times were slowed to>24 h and 7 h; these results suggest that in the clinical setting, daptomycin dosages of approximately 6 mg/kg are required to achieve bactericidal activity against vancomycin-resistant Enterococcus faecium. [ABSTRACT FROM AUTHOR]

The killing kinetics of cefuroxime against 25 Streptococcus pneumoniae isolates with penicillin MICs of <0.1, 0.1-1.0 and 2 mg/l were studied in an in vitro model simulating the serum concentration profile in healthy adults following a single intramuscular injection of 500 mg. Cefuroxime was bactericidal against the isolates with exquisite or slightly diminished susceptibility to penicillin (−4 and −3.9 log10 cfu/ml killing, respectively) during the 6 h incubation period. In contrast, there was only a 2.8 log10 cfu/ml reduction in the initial inoculum of six of the eight isolates resistant to penicillin (MIC 2 mg/l). The two remaining penicillin-resistant isolates (cefuroxime MIC 8 mg/l) only showed a 2 log10 cfu reduction in the initial inoculum. [ABSTRACT FROM AUTHOR]