The polymerase chain reaction (PCR) technique was used to detect Mycoplasma pneumoniae DNA in clinical samples (nasopharyngeal aspirations or bronchoalveolar lavages) obtained from 100 children, 1 month to 16 years old. PCR allowed the detection of M. pneumoniae DNA from 20 out of the 100 patients studied. In 16 cases, PCR positivity was associated with acute respiratory symptomatology. For five PCR-positive patients, a positive culture or a serological response evidenced acute M. pneumoniae infections. A lack of antibody response was observed particularly with immunocompromised children and infants less than 12 months old. The amount of M. pneumoniae DNA in the PCR was estimated in a semiquantitative way by comparison of its hybridization signal with those obtained for 100, 10, and 1 color-changing unit (CCU) of the M. pneumoniae FH strain. Small amounts (<102 CCU/ml) of M. pneumoniae were found in samples from asymptomatic patients, while larger amounts (.102 to .104 CCU/ml) were found for 8 out of 10 patients with acute pneumonia.

Two associated resistance mechanisms were found in a nalidixic acid-susceptible (4 ,ug/ml) but fluoroquinolone-resistant (8 to 16 ,ug/ml) strain of Escherichia coli Q2 selected under norfloxacin therapy. As compared with the susceptible E. coli Ql isolated before treatment, changes in outer membrane proteins and lipopolysaccharides in Q2 were associated with a 1.5-to 3-fold decrease in the uptake of fluoroquinolones but not nalidixic acid. A 50% inhibition of DNA synthesis in toluene-permeabilized cells of the resistant strain E. coli Q2 required up to 500-fold increased quantities of fluoroquinolones, whereas such inhibition was obtained in both E. coli Ql and Q2 with similar amounts of nalidixic acid. Selection from E. coli Ql on norfloxacin of one-step resistant mutants resembling E. coli Q2 was unsuccessful. From these results we infer that a decrease in outer membrane permeability, associated with a peculiar alteration of the DNA gyrase, was responsible for the unusual quinolone resistance phenotype of E. coli Q2.Quinolones are synthetic antibiotics which can be grouped into the older compounds nalidixic acid, pipemidic acid, piromidic acid, and flumequine and the newer, fluorinated quinolones such as norfloxacin pefloxacin, ofloxacin, and ciprofloxacin. The latter have comparatively enlarged spectra of activity as well as better intrinsic activities. Many studies have been carried out with quinolone-resistant gramnegative bacilli. Two main mechanisms of resistance which may occur either alone or combined have been found (15): (i) modification of the DNA gyrase in either subunit A (8, 10, 15, 20) or B (16, 21), which can give rise to moderate or high levels of resistance, and (ii) decreased uptake of quinolones, which correlates with a decrease in the quantity of porins (5, 10, 13-15). Another not totally elucidated mechanism involving the marA gene may be responsible for low levels of resistance (7).It was the purpose of this study to describe the mechanism(s) which could explain the particular profiles of resistance to fluroroquinolones and susceptibility to nalidixic acid observed in a clinical isolate of Escherichia coli. Hinton agar by using a Steers-type replicator device with ca. 104 CFU per spot and were read after 18 h of incubation at 37°C. MICs of novobiocin were determined as the quantities of antibiotic necessary to totally inhibit the growth of 100 CFU per plate after 18 h of incubation at 37°C (21). Selection of resistant mutants. Mutants resistant to norfloxacin were selected in vitro on plates containing a gradient of the antibiotic from 0 to 8 pug/ml.Extraction of OM proteins and LPS. Cell membranes were prepared from 200 ml of exponential-phase cultures at an optical density at 650 nm of 0.4 as previously described (19). Outer membrane (OM) proteins were obtained as follows: 100 jig of total-membrane protein was incubated for 45 min at 25°C in 70 RI of sodium phosphate buffer (50 mM, pH 7.0) containing 0.3% of N-laurylsarcosine N197 (ICN Biochemicals, Cleveland, Ohio) and centrifuged at ...

Over the 3-year study period beta-lactams and fluoroquinolones remained highly active against Enterobacteriaceae clinical isolates, with the exception of E. aerogenes, probably as a result of the dissemination of multiresistant clones in French hospitals.

A new paediatric formulation of roxithromycin was tested for acceptability, efficacy and safety in a multicentre, prospective, non-comparative trial in 210 children, aged between 2 and 8 years, with a variety of respiratory tract infections. Most children were diagnosed as having rhinobronchitis, acute pharyngitis or acute tonsillitis. A dose of 5-8 mg/kg/day (mean +/- SD, 5.92 +/- 1.12) roxithromycin was given orally for 5-10 days (mean +/- SDL 6.86 +/- 1.80). The formulation consists of a tablet for suspension in a small volume of water, administered using a spoon, twice daily. Acceptability was good, with only eight children refusing their medication because of the taste or because of vomiting. The method of administration was found to be convenient by 76% of parents. The clinical success rate was 89.1% in the intent-to-treat analysis. There were only 18 adverse events reported by 14 patients; of these, only 10 events (all gastrointestinal) in eight patients were classified as drug related. A total of eight patients discontinued treatment because of an adverse event, but in only four were the events drug related.