Inhibitory and bactericidal activities of levofloxacin against Mycobacterium tuberculosis in vitro and in human macrophages

Abstract

Levofloxacin exhibited twofold greater inhibitory and bactericidal activities than ofloxacin against either extracellular or intracellular tubercle bacilli. The activities of both drugs against extracellular and intracellular bacteria were about the same, despite the accumulation of the drugs in macrophages at a level four-to fivefold greater than that in the extracellular medium. The activities of both drugs against intracellular bacteria were largely associated with the short, 2-h pulsed exposures of the infected macrophages to the concentrations which correspond to those attainable in blood during the period of the maximum concentration of drug in serum.Among the quinolones, ofloxacin was the first agent used to treat patients with tuberculosis (16). Comparison of the in vitro activities of various quinolones indicated that ofloxacin and ciprofloxacin had better potentials than norfloxacin, amifloxacin, perfloxacin, and other compounds of this class for the treatment of tuberculosis (1, 2, 5, 7, 9, 13-15, 17, 18). The MICs of both ofloxacin and ciprofloxacin in various types of liquid media and in 7H10 or 7H11 agar ranged from 0.12 to 2.0 ,ug/ml (10). The MBCs of these two drugs determined in 7H12 broth were 2.0 ,ug/ml, giving MBC/MIC ratios of 2 to 4 (10, 15). Levofloxacin, the optically active L-isomer of ofloxacin, has shown high levels of antibacterial activity both in vitro and in mice against a number of bacterial species, being either as active as or up to fourfold more active than ofloxacin (8).The aim of the study described here was the preclinical evaluation of the activity of levofloxacin in comparison with that of ofloxacin against Mycobacterium tuberculosis in human monocyte-derived macrophages as well as in cell-free medium.Antimicrobial agents. Ofloxacin and levofloxacin were obtained from the R. W. Johnson Pharmaceutical Research Institute (Springhouse, Pa.). Stock solutions were made in phosphate buffer (pH 6.5). These stock solutions were diluted further to make appropriate working solutions.Test strains. Studies in macrophages were conducted with two M. tuberculosis strains: H37Rv, which is susceptible to all antituberculosis drugs, and a Vertullo strain (2937-0), one of the quality control strains in our laboratory, which is resistant to isoniazid, rifampin, streptomycin, and ethambutol. The same two strains and an additional nine clinical isolates were used for determination of the MICs in vitro. Subcultures in 7H9 broth were preserved in aliquots frozen at -70°C. For each experiment, a subculture of frozen stock was made in 7H9 broth. After S to 6 days of cultivation at 37°C, the culture was forced through a 27-gauge needle and was then centrifuged at 250 x g for 5 min to remove large clumps of bacteria.Model of the M. tuberculosis-infected macrophages. The technique for preparation of the human monocyte-derived macrophage monolayers was as described previously by Crowle and colleagues (3, 4), with some modifications given in our * Corresponding author. Mailing address: National Jewish C...

Schneller Nachweis von Mutationen im gyrA-Gen von Mycobacterium tuberculosis mit Relevanz für die Entstehung von Medikamentenresistenzen gegen Chinolone mittels der Real-Time PCR auf dem LightCycler® System

“…Sie verfügen über eine hohe orale Bioverfügbarkeit, Blutspiegel (C max ) ereichen das 2-(Ciprofloxacin 250 mg) bis 9-fache (Moxifloxacin 400 mg) der jeweiligen MHK. Chinolone besitzen zudem eine ausgezeichnete Gewebepenetration und akkumulieren in Makrophagen (Mor, Vanderkolk et al 1994). Gyrasehemmer besitzen außerdem eine gute bakterizide Wirkung.…”

Validation of the Use of Middlebrook 7H10 Agar, BACTEC MGIT 960, and BACTEC 460 12B Media for Testing the Susceptibility of Mycobacterium tuberculosis to Levofloxacin

“…For susceptible strains, LVX test concentrations were 2, 1, 0.5, 0.25, and 0.125 g/ml. The test concentrations selected were expected to be satisfactory, based on previously published MIC results of LVX for M. tuberculosis (5,7,12). BACTEC 460 radiometric MIC determinations were done by standard methods.…”

“…For fluoroquinolone-susceptible strains, quadrant I was the drug-free control, and quadrants II, III, and IV contained LVX at 1, 0.5, and 0.25 g/ml, respectively. The test concentrations selected were expected to be satisfactory based on previously published MIC results of LVX for M. tuberculosis (5,7,13). Plates were inoculated by standard methods (6).…”

Determination of levofloxacin in human serum using liquid chromatography tandem mass spectrometry

“…The greatest bactericidal effect of levofloxacin occurs at maximum serum/plasma concentration to minimum inhibitory concentration (C max : MIC) ratios of 8-10 and area under concentration time curve in 24 hrs to MIC (AUC 0-24 : MIC) ratios of 125:1 [3][4][5]. Levofloxacin has a good in-vitro and in-vivo activity against strains of M.tuberculosis [6][7][8]. MIC values were low in laboratory and in clinical isolates [9] and in mouse models [10].…”