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Digoxin-like immunoreactivity in serum from neonates and infants reduced by centrifugal ultrafiltration and fluorescence polarization immunoassay.


Microdialysis is a technique that allows the measurement of concentrations of free antibiotic in tissue. The free antibiotic concentration is responsible for the antibacterial effect at the target site. We used microdialysis in animal and human studies to investigate the tissue penetration of cefpodoxime. In the animal study, total plasma and free muscle and lung concentrations of cefpodoxime were measured after male Wistar rats had received either 10 mg/kg or 20 mg/kg i.v. cefpodoxime over 5 h or a continuous i.v. infusion of 260 microg/h cefpodoxime after a loading dose of 6 mg/kg. Free muscle concentrations of cefpodoxime were similar to free lung concentrations and therefore provided a surrogate measure of cefpodoxime concentrations at the pulmonary target site. In an open, randomized, two-way crossover, single-dose study in six healthy male volunteers, total plasma and free muscle concentrations were measured after a single oral dose of cefpodoxime 400 mg or cefixime 400 mg. The total plasma concentrations of each antibiotic were similar and higher than free muscle concentrations. The tissue penetration of cefpodoxime was, however, greater than that of cefixime, as shown by two-fold higher peak free muscle concentrations after dosing with cefpodoxime than with cefixime (2.1 mg/L versus 0.9 mg/L). In addition, the area under the curve for tissue (AUC(t)) of cefpodoxime (400 mg) was more than double that of cefixime (400 mg), based on free antibiotic concentrations (15.4 mg x h/L versus 7.3 mg x h/L). These findings indicate that, taking into account pharmacokinetic/pharmacodynamic considerations, cefpodoxime is likely to be more efficacious than cefixime, due to its greater tissue penetration.

One hundred lettuce samples collected in Tehran were transported to the laboratory, homogenized by a stomacher in EC broth containing cefixime, and cultured on MacConkey agar plates. Bacterial DNA was extracted by boiling method and PCR was performed using three pairs of primers targeting stx 1, stx 2 and eaeA genes.

GV104326 is a novel tricyclic beta-lactam (a trinem or, formerly, tribactam). The in vitro activity of GV104326 was compared with those of cefuroxime, cefixime, amoxicillin, amoxicillin-clavulanic acid, cefpirome, and ciprofloxacin. GV104326 had in vitro activity generally similar to that of cefixime against members of the family Enterobacteriaceae (MIC at which 90% of the isolates are inhibited [MIC90], < or = 2 micrograms/ml), with cefuroxime and amoxicillin-clavulanic acid being 8- to 32-fold less active and with cefpirome being 4- to 8-fold more active against members of this family. The trinem had no activity against Pseudomonas aeruginosa or Stenotrophomonas maltophilia (MIC90, > 128 micrograms/ml) but was the most active agent against Acinetobacter calcoaceticus. GV104326 was particularly active against gram-positive cocci. Ninety percent of methicillin-susceptible Staphylococcus aureus strains were susceptible to 0.03 microgram of GV104326 per ml, making it the most active agent studied. Enterococci and Lancefield group A and B streptococci were generally equally or somewhat more susceptible to GV104326 than they were to amoxicillin. Streptococcus pneumoniae strains were highly susceptible to GV104326, and those strains which showed decreased susceptibility to penicillin were generally twofold more susceptible to the trinem than to amoxicillin. Haemophilus influenzae and Moraxella catarrhalis were highly susceptible to GV104326 (MIC90s, 0.12 and 0.03 microgram/ml, respectively). The anaerobes Clostridium perfringens, Bacteroides fragilis, and Peptostreptococcus spp. were more susceptible to the trinems (formerly tribactams) than to the other agents studied.

Of 74 evaluable patients, 24 (32%) had negative follow-up cultures. Culture transport media for these 24 culture-negative patients were tested with DFA or PCR assays for chlamydial infection, and 3 (13%) were positive. Culture positivity rates declined significantly with increasing age and duration of follow-up. Interval treatment with benzathine penicillin resulted in apparent resolution of infection in 9 of 10 patients. Neither a history of a C. trachomatis-associated syndrome nor treatment with cefixime, metronidazole, or antifungal agents was associated with clearance of infection.

A heterologous gene expression system, Xenopus laevis oocytes, was used to prove the intestinal absorption of various beta-lactam antibiotics mediated by an H(+)-dipeptide cotransport system in rat, rabbit and human small intestines. The microinjection of mRNA (messenger RNA) from rat intestine into Xenopus laevis oocytes led to significantly higher uptakes of p.o. active cephalosporins including zwitter-ionic derivatives (cephalexin, cephradine and cefadroxil) and dianionic derivatives (cefixime and ceftibuten) in comparison with oocytes injected with water, whereas the uptake of cefazolin, a parenterally administered derivative, was negligible in both mRNA- and water-injected oocytes. The uptake of cefadroxil was reduced significantly in the presence of dipeptide and various beta-lactam antibiotics, but not in the presence of an amino acid. After sucrose density gradient centrifugation of mRNA, the highest expression of transport activities of both cefadroxil and ceftibuten was observed in the same mRNA fraction with a size of 2.20 to 3.75 kilobases. mRNA-injected oocytes showed a marked pH-dependency in the uptakes of cefadroxil and ceftibuten, whereas water-injected oocytes exhibited only modes uptakes. The most stimulated uptakes of cefadroxil and ceftibuten were observed at an external pH of 5.5 and 5.0, respectively. Furthermore, injection of mRNA isolated from either rat rabbit or human small intestine into oocytes produced significantly higher uptake of cefadroxil and ceftibuten compared with those by oocytes injected with water. Thus, intestinal absorption of p.o. active beta-lactam antibiotics was confirmed to be mediated by an H+ gradient-dependent transport system across the brush-border membrane of rats, rabbits and humans. The carrier-protein for this process is likely a dipeptide transport system.