In vitro antimycoplasmal activities of rufloxacin and its metabolite MF 922

Abstract

The in vitro activities of rufloxacin and its metabolite, MF 922, were compared with those of ofloxacin, ciprofloxacin, erythromycin, and minocycline against Mycoplasma pneumoniae, Mycoplasma hominis, Mycoplasmafermentans, and Ureaplasma urealyticum. Rufloxacin, MF 922, and ciprofloxacin shared similar activities against all mycoplasmas tested. (MICs for 90%Yo of isolates tested [MIC90s], 0.5 to 4 ,ig/ml). Ofloxacin had the lowest MIC%0s for U. urealyticum, M. fermentans, and M. hominis (MIC90s, 0.25 to 1 ,ug/ml) and erythromycin had the lowest MIC90 for M. pneumoniae (MIC90, 0.004 ,ug/ml).Fluoroquinolones represent a new class of broad-spectrum antimicrobial agents which are active against gram-negative and many gram-positive organisms. These compounds are bactericidal and generally have good pharmacokinetic and safety profiles. However, some pathogens, including mycoplasmas, are not sufficiently susceptible at low concentrations to many of the quinolones tested (1-3, 7-9, 16-18, 21, 22, 25, 27, 33, 34). Several new compounds have been developed in an attempt to broaden the spectrum of activity, increase the potency, and enhance the disposition of the drug at infection sites. Fig. 1) is a new oral 6-fluoroquinolone with a broad spectrum of activity against gram-negative and grampositive aerobic bacteria and some intracellular pathogens, including Chlamydia pneumoniae and Legionella pneumophila (10,23,36). In vitro, the antibacterial activity of rufloxacin is similar to that of norfloxacin (36), while in animal models it has activity similar to that of ciprofloxacin (12). In humans pharmacokinetic studies have demonstrated that rufloxacin is eliminated slowly, with a half-life in plasma of about 35 h (14,19,37). The drug penetrates well into most body fluids, tissues, and cells, where it reaches high and stable concentrations, ranging from 2 to 25 times those in plasma (4,19,35,37). Particularly high concentrations are achieved in epithelial lining fluid (peak mean values, 42 ,ug/ml) and alveolar macrophages (peak mean values, 88 ,ug/ml) (35). Steady high concentrations (60 ,ug/ml) of rufloxacin are attained in urine up to 72 h following administration of a single 400-mg dose (37). In view of its pharmacokinetic profile, it can be used once daily for the treatment of urinary (5, 24) and respiratory tract (20) infections. It is metabolized at a low level. The N-desmethyl derivative (MF 922) (Fig. 1) is the only microbiologically active metabolite detected. In urine it accounts for 2% of the given dose (19). The in vitro activity of MF 922 is comparable to that of the parent compound (36). However, their effects on mycoplasmas have not been described previously. Rufloxacin (The objective of the study described here was to determine the in vitro susceptibilities of Mycoplasma pneumoniae, Myco- plasma hominis, Mycoplasma fermentans, and Ureaplasma urealyticum to rufloxacin and MF 922 compared with those of ofloxacin, ciprofloxacin, erythromycin, and minocycline. Minocycline was selected rather than tetracycline bec...

<i>In Vitro</i> Efficacy of <i>Crataegus oxycantha</i> L. (Hawthorn) and Its Major Components against ATCC and Clinical Strains of <i>Ureaplasma urealyticum</i>

“…In the present study erythromycin was inhibitory to U. urealyticum clinical isolates, with MIC ranges between 0.48 and 1.95 μg/ml. However, in a previous investigation, the U. urealyticum isolates were inhibited by erythromycin at MICs ranging from 0.06 -≥256 μg/ml and 16% of the tested strains were highly resistant to this antibiotic, with MIC values ≥256 μg/ml [21]. This trend demonstrated the isolates used in the present study had not developed antibiotic resistance to macrolides.…”

“…The broth microdilution method, according to CLSI [20], was used. The MIC was defined as the lowest concentration of compound which inhibited the color change in the broth at the time when the color of the control tube changed and the pH of the medium increased from pH 6.0 to pH 6.5 [21]. The MICs were read after an overnight incubation.…”