Activities of various quinolone antibiotics against Mycobacterium leprae in infected mice

Insights of synthetic analogues of anti-leprosy agents

Today, the emergence of the phenomenon of drug or multidrug-resistance for community-associated diseases represents a major concern in the world. In these contexts, the chronic infectious disease, leprosy, grounded by a slow-growing bacterium called Mycobacterium leprae or Mycobacterium lepromatosis is a leadingcause of severe disfiguring skin sores and nerve damage in the arms, legs, and skin areas around the body. Even, over 200,000 new leprosy cases are being accounted every year along with the relapsed leprosy cases. Nonetheless, this has been considered a curable disease with a higher dose of multidrug therapy (MDT) for a long period of time. The prolonged action of a high dose of combination drugs administration may cause an adverse reaction that can significantly affect patient compliance, particularly the outbreak of multidrug-resistance in the infected person. To overcome these shortfalls or prevent the resistance-associated problems, researchers are diligently involved in the structural modifications of the clinically used anti-leprosy drugs or the allied compounds for the structure-antimycobacterial activity relationship study. This review article described the detailed synthesis and biological assays of different anti-leprosy compounds reported by several research groups.

The diarylquinoline R207910 is bactericidal against Mycobacterium leprae in mice at low dose and administered intermittently

The diarylquinoline R207910 is profoundly bactericidal in a murine model of tuberculosis. Previously, R207910 was also found to be bactericidal for Mycobacterium leprae-infected mice during lag phase. Herein we evaluate the bactericidal efficacy of R207910 (1 to 120 mg/kg of body weight) when administered five times weekly, once weekly, and once monthly during logarithmic multiplication of M. leprae organisms. All treatments were found to be bactericidal, suggesting that both low and intermittent dosing with R207910 holds promise for leprosy patients.

Powerful bactericidal activity of moxifloxacin in human leprosy

In a clinical trial of moxifloxacin in eight multibacillary leprosy patients, moxifloxacin proved highly effective. In all trial patients, a single 400-mg dose of moxifloxacin resulted in significant killing (P <or= 0.006) of Mycobacterium leprae, ranging from 82% to 99%, with a mean of 91%. In all instances, no viable bacilli were detected with an additional 3 weeks of daily therapy, this observed rapid bactericidal activity being matched previously only by rifampin. On moxifloxacin therapy, skin lesions cleared exceedingly rapidly with definite improvement observed consistently after eight doses and progressive resolution continuing for the 56 days of the trial. Side effects, toxicities, and laboratory abnormalities were mild, not requiring discontinuation of therapy.

Expression and purification of an active form of the Mycobacterium leprae DNA gyrase and its inhibition by quinolones

Mycobacterium leprae, the causative agent of leprosy, is noncultivable in vitro; therefore, evaluation of antibiotic activity against M. leprae relies mainly upon the mouse footpad system, which requires at least 12 months before the results become available. We have developed an in vitro assay for studying the activities of quinolones against the DNA gyrase of M. leprae. We overexpressed in Escherichia coli the M. leprae GyrA and GyrB subunits separately as His-tagged proteins by using a pET plasmid carrying the gyrA and gyrB genes. The soluble 97.5-kDa GyrA and 74.5-kDa GyrB subunits were purified by nickel chelate chromatography and were reconstituted as an enzyme with DNA supercoiling activity. Based on the drug concentrations that inhibited DNA supercoiling by 50% or that induced DNA cleavage by 25%, the 13 quinolones tested clustered into three groups. Analysis of the quinolone structure-activity relationship demonstrates that the most active quinolones against M. leprae DNA gyrase share the following structural features: a substituted carbon at position 8, a cyclopropyl substituent at N-1, a fluorine at C-6, and a substituent ring at C-7. We conclude that the assays based on DNA supercoiling inhibition and drug-induced DNA cleavage on purified M. leprae DNA gyrase are rapid, efficient, and safe methods for the screening of quinolone derivatives with potential in vivo activities against M. leprae.

The continuing challenges of leprosy

Leprosy is best understood as two conjoined diseases. The first is a chronic mycobacterial infection that elicits an extraordinary range of cellular immune responses in humans. The second is a peripheral neuropathy that is initiated by the infection and the accompanying immunological events. The infection is curable but not preventable, and leprosy remains a major global health problem, especially in the developing world, publicity to the contrary notwithstanding. Mycobacterium leprae remains noncultivable, and for over a century leprosy has presented major challenges in the fields of microbiology, pathology, immunology, and genetics; it continues to do so today. This review focuses on recent advances in our understanding of M. leprae and the host response to it, especially concerning molecular identification of M. leprae, knowledge of its genome, transcriptome, and proteome, its mechanisms of microbial resistance, and recognition of strains by variable-number tandem repeat analysis. Advances in experimental models include studies in gene knockout mice and the development of molecular techniques to explore the armadillo model. In clinical studies, notable progress has been made concerning the immunology and immunopathology of leprosy, the genetics of human resistance, mechanisms of nerve injury, and chemotherapy. In nearly all of these areas, however, leprosy remains poorly understood compared to other major bacterial diseases.

In vitro activity of ciprofloxacin, ofloxacin and levofloxacin against Mycobacterium tuberculosis

BACKGROUND

The increasing incidence of drug-resistant Mycobacterium tuberculosis necessitates therapeutic alternatives. The fluoroquinolones fulfill most of the criteria for an ideal class of antimycobacterial drugs. The aim of the present study was to determine to in vitro activities of ciprofloxacin, ofloxacin, and levofloxacin against M. tuberculosis strains.

METHODS

Susceptibility to four antituberculous drugs used in first-line treatment of tuberculosis was tested in 100 strains isolated from clinical samples. Nineteen strains (19%) were resistant to at least one of the four antituberculous drugs and 13 were multidrug resistant. The in vitro antimycobacterial activity of ciprofloxacin, ofloxacin, and levofloxacin was then determined against 100 M. tuberculosis strains using standard agar proportion dilution method.

RESULTS

Ciprofloxacin, ofloxacin, and levofloxacin were active against all tested strains of M. tuberculosis in vitro.

CONCLUSIONS

Ciprofloxacin, ofloxacin, and levofloxacin have relatively potent in vitro activity against M. tuberculosis. Further in vivo studies are needed to determine the role of these compounds in the treatment of tuberculosis, but use should be limited to special circumstances rather than first-line treatment.

Enhanced antitumor activity of ultrasonic irradiation in the presence of new quinolone antibiotics in vitro

To determine if there is any synergistic antitumor effect of ultrasound (US) in the presence of new quinolone (NQ) antibiotics, 0.2 mM solutions of lomefloxacin hydrochloride (LFLX), sparfloxacin (SPFX), ciprofloxacin hydrochloride (CPFX), and gatifloxacin hydrate (GFLX) were tested as sonodynamic agents against sarcoma 180 cells in vitro. After US irradiation at 2 W/cm(2) for 30 and 60 s, the survival rates of tumor cells in the presence of NQ antibiotics were significantly lower than those in their absence (P < 0.001). In May-Giemsa smears, most of the tumor cells remained intact in the control group. However, in the 0.2 mM SPFX group, the tumor cells were mostly fragmented. The synergistic antitumor effect of SPFX was dose-dependent. Furthermore, when D-mannitol was used with SPFX, the survival rate of tumor cells after irradiation was comparable with that when SPFX alone was applied, but when L-histidine was used concurrently, the survival rate of tumor cells was significantly higher than that when SPFX alone was applied. These findings suggest that NQ antibiotics would exhibit useful antitumor activity under US irradiation, and that generation of singlet oxygen is involved in the process of cell damage.

Experimental evaluation of possible new short-term drug regimens for treatment of multibacillary leprosy

Groups of nude mice, with both hind footpads infected with 10(8) Mycobacterium leprae organisms, were treated with 4-week courses of different drug combinations. The effect treatment on each group was evaluated by subinoculating footpad homogenates from the treated mice into groups of normal and nude mice for subsequent regrowth, assessed 1 year later. A combination of rifampin (RMP) with clarithromycin (CLARI), minocycline (MINO), and ofloxacin (OFLO) resulted in the complete killing of M. leprae after 3 weeks of treatment. A combination of sparfloxacin (SPAR) and RMP also resulted in a similar bactericidal effect after 3 weeks of treatment. Other drug combinations showed variable effects. Very little or no effect was observed with any regimen if the treatment was given for less than 2 weeks. World Health Organization (WHO) multidrug therapy (MDT) given for 8 weeks was as effective as the two combinations described above. The results suggest that multidrug combinations consisting of RMP-OFLO (or SPAR)-CLARI (and/or MINO) are as effective as the WHO MDT for the treatment of experimental leprosy. Moreover, they imply that these combinations, which were found to be active in a 4-week experimental treatment protocol, could be administered as treatment to patients for a period of time shorter than the present 2-year regimen without a loss of effectiveness.

Clinical trial of sparfloxacin for lepromatous leprosy

Nine previously untreated patients with lepromatous leprosy were treated with 200 mg of sparfloxacin daily for 12 weeks to determine whether this drug is bactericidal for Mycobacterium leprae in humans. The efficacy of therapy was monitored both clinically and by measuring changes in morphological index, mouse footpad infectivity, and the radiorespirometric activity of M. leprae organisms obtained from serial biopsy specimens and also by determining titers of phenolic glycolipid-I in serum. Most patients showed clinical improvement within 2 weeks of treatment; this was accompanied by significant reductions in the morphological index, mouse footpad infectivity, and bacillary radiorespirometric activity. After 4 weeks of treatment, all patients had a morphological index of zero and specimens from most patients were noninfectious for mice, while the median decrease in radiorespirometric activity was > 99%. Overall results by the rapid radiorespirometric assay paralleled those of the mouse footpad and morphological index assays. Sparfloxacin given at 200 mg once daily appears to be rapidly bactericidal in humans, with activity similar to that observed in a previous clinical trial with 400 mg of ofloxacin.