Johan W Mouton — Page 3

PubMed2002

Ciprofloxacin in polyethylene glycol-coated liposomes: efficacy in rat models of acute or chronic Pseudomonas aeruginosa infection.

In a previous study in experimental Klebsiella pneumoniae pneumonia, the therapeutic potential of ciprofloxacin was significantly improved by encapsulation in polyethylene glycol-coated ("pegylated") long-circulating (STEALTH) liposomes. Pegylated liposomal ciprofloxacin in high doses was nontoxic and resulted in relatively high and sustained ciprofloxacin concentrations in blood and tissues, and hence an increase in the area under the plasma concentration-time curve (AUC). These data correspond to data from animal and clinical studies showing that for fluoroquinolones the AUC/MIC ratio is associated with favorable outcome in serious infections. Clinical failures and the development of resistance are observed for marginally susceptible organisms like Pseudomonas aeruginosa and for which sufficient AUC/MIC ratios cannot be achieved. In the present study the therapeutic efficacy of pegylated liposomal ciprofloxacin was investigated in two rat models of Pseudomonas aeruginosa pneumonia. In the acute model pneumonia developed progressively, resulting in a rapid onset of septicemia and a high mortality rate. Ciprofloxacin twice daily for 7 days was not effective at doses at or below the maximum tolerated dose (MTD). However, pegylated liposomal ciprofloxacin either at high dosage or given at low dosage in combination with free ciprofloxacin on the first day of treatment was fully effective (100% survival). Obviously, prolonged concentrations of ciprofloxacin in blood prevented death of the animals due to early-stage septicemia in this acute infection. However, bacterial eradication from the left lung was not effected. In the chronic model, pneumonia was characterized by bacterial persistence in the lung without bacteremia, and no signs of morbidity or mortality were observed. Ciprofloxacin administered for 7 days at the MTD twice daily resulted in killing of more than 99% of bacteria in the lung; this result can also be achieved with pegylated liposomal ciprofloxacin given once daily. Complete bacterial eradication is never observed.

Acute Disease↗

PubMed2002

Comparison of the Etest and the sensititre colorimetric methods with the NCCLS proposed standard for antifungal susceptibility testing of Aspergillus species.

The susceptibilities of 25 clinical isolates of Aspergillus fumigatus, A. flavus, A. terreus, A. nidulans, and A. ustus to itraconazole and amphotericin B were determined by an agar diffusion-dilution method (the Etest method) and a colorimetric broth microdilution method (the Sensititre method); and the results were compared with those obtained by the NCCLS proposed standard M-38P method for antifungal susceptibility testing of filamentous fungi. Various MIC endpoints for the three methods were determined visually by four different observers in three blinded experiments, and the reproducibilities among the observers (interobserver agreement) and among the replicates (interexperimental agreement) as well as the levels of agreement between the NCCLS, the Etest, and the Sensititre methods were calculated. High levels of reproducibility (within 1 twofold dilution) were found for the NCCLS method (>95%) with the MIC-0 endpoint (complete inhibition of growth) for both drugs and with the MIC-1 endpoint (slight growth) for itraconazole and for the Sensititre method (>90%) with all MIC endpoints, although for the latter the interexperimental agreement for itraconazole was comparatively lower (83 to 93%). The Etest method was less reproducible (67 to 87%) for both drugs. Using the recommended MIC endpoints, high levels of agreement (within one twofold dilution) between the NCCLS and the Sensititre methods for all species were found for amphotericin B (>77%) but not for itraconazole (<66%), for which the MICs by the Sensititre method were up to 3 twofold dilutions lower than the corresponding MICs by the NCCLS method. The use of the first blue well as an endpoint for the Sensititre method and 48 h of incubation improved the levels of agreement with the NCCLS method. Low levels of agreement between the NCCLS and the Etest methods using the recommended MIC endpoints were found for most species, especially after 48 h of incubation (<50%), when the MICs obtained by the Etest method were up to 9 twofold dilutions higher than the corresponding MICs obtained by the NCCLS method. Relatively better agreement was found after 24 h, although it was species dependent, with the highest levels of agreement (>82%) found for A. terreus and A. ustus for amphotericin B and A. fumigatus for both drugs. Overall, better agreement was found when MIC-0 was used as the MIC endpoint for the NCCLS method for both drugs and when the MICs by the Etest method were determined after 48 h of incubation for itraconazole and after 24 h of incubation for amphotericin B.

Amphotericin B↗