Fusidic acid is highly active against extracellular and intracellular Mycobacterium leprae

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.

Mycobacterium leprae is naturally resistant to PA-824

Leprosy responds very slowly to the current multidrug therapy, and hence there is a need for novel drugs with potent bactericidal activity. PA-824 is a 4-nitroimidazo-oxazine that is currently undergoing phase I clinical trials for the treatment of tuberculosis. The activity of PA-824 against Mycobacterium leprae was tested and compared with that of rifampin in axenic cultures, macrophages, and two different animal models. Our results conclusively demonstrate that PA-824 has no effect on the viability of M. leprae in all three models, consistent with the lack of the nitroimidazo-oxazine-specific nitroreductase, encoded by Rv3547 in the M. leprae genome, which is essential for activation of this molecule.

Fusidic acid in vitro activity

Fusidic acid is a narrow spectrum agent that acts to inhibit protein synthesis by inhibition of elongation factor G at the level of the ribosome. Because of high protein binding susceptibility testing in vitro is affected by the presence of blood or serum. In addition, there is a modest inoculum effect in vitro. A breakpoint of 1 or 2 mg/l is most widely used for defining resistance to systemic treatment with fusidic acid. Fusidic acid activity is principally directed at staphylococci, both Staphylococcus aureus and coagulate-negative species which are highly susceptible. It is also active against Gram-positive anaerobic activity, and shows in vitro activity against Neisseria spp., Bordetella pertussis and Moraxella catarrhalis. It has no activity against other aerobic Gram-negative species. Modest activity (MICs just above breakpoint values) is seen with Streptococcus and Enterococcus spp. as well as Gram-negative anaerobic bacteria. Fusidic acid is defined as bacteriostatic. For staphylococci MBC values are generally 8--32-fold that of the MIC. Interaction studies with other antibiotics give varying results depending on methodology. However, interaction with beta-lactams is generally indifferent, as it is with rifampicin, while aminoglycosides and macrolides appear to be synergistic and fluoroquinolones antagonistic. Fusidic acid appears to inhibit the function of neutrophils and T-lymphocytes at clinically achieved concentrations.

Clinical trial of fusidic acid for lepromatous leprosy

Fusidic acid was assessed for antileprosy activity in nine lepromatous leprosy patients. Patients received fusidic acid at either 500 mg/day for 12 weeks or 750 mg/day for 4 weeks followed by 500 mg/day for 8 weeks. All patients showed time-dependent clinical improvement and decreases in bacillary morphological index, radiorespirometric activity and PCR signal, and in serum phenolic glycolipid I. Fusidic acid appears to be a weakly bactericidal antileprosy agent which may have a role in the multidrug treatment of leprosy pending an evaluation of lepra-reaction-suppressive activity.

Development of an in vitro drug screening system for Mycobacterium leprae based on the determination of the intrabacterial sodium to potassium ratio of individual bacterial organisms

In vitro drug effects on Mycobacterium leprae (M. leprae) in a cell-free system have been monitored by mass spectrometric determination of the ratio of the intrabacterial concentrations of the sodium and potassium ions (Na(+), K(+) ratio) of a limited number of individual bacteria per sample. From the drug-induced increase of the median values of the distributions of the Na(+), K(+) ratio, information on the concentration and time dependence of drug effects as well as on antagonistic or synergistic interactions of drugs has been obtained. Moreover, absolute values for the percentage of killed bacteria (% kill) have been derived from the distribution of the Na(+), K(+) ratios within a bacterial population. For this, the limiting value of the Na(+), K(+) ratio (up to which bacteria are viable) -which had been determined as 0.45 for cultivable bacteria - has been presumed to be valid also for M. leprae. Highest killing rates have been observed for fusidic acid and clarithromycin, followed by rifabutine, rifampin, and clofazimine. Minocycline and dapsone have shown only moderate killing effects and isoniazid and - probably due to the restricted metabolism of M. leprae in a cell-free medium - ofloxacin have been completely inactive. Strong ofloxacin effects, however, have been observed for cultivable mycobacteria and intracellular M. leprae phagocytized by a murine macrophage cell line.

Susceptibility of Mycobacterium kansasii to ofloxacin, sparfloxacin, clarithromycin, azithromycin, and fusidic acid

The MICs of ofloxacin, sparfloxacin, clarithromycin, azithromycin, and fusidic acid for clinical isolates of Mycobacterium kansasii were determined by the radiometric (BACTEC) method. All drugs except azithromycin elicited MICs for 90% of the strains tested that were lower than previously reported achievable maximum concentrations in serum. Ofloxacin, sparfloxacin, and clarithromycin had the largest maximum concentration in serum/MIC for 90% of strains ratio of the drugs tested.

In vitro activities of ceftriaxone and fusidic acid against 13 isolates of Coxiella burnetii, determined using the shell vial assay

The susceptibilities of 13 isolates of Coxiella burnetii to fusidic acid and ceftriaxone were determined by use of the recently described shell vial assay (D. Raoult, H. Torres, and M. Drancourt, Antimicrob. Agents Chemother, 35:2070-2077, 1991). At a concentration of 4 micrograms/ml, ceftriaxone was bacteriostatic for four isolates and slowed the multiplication of the other nine. Fusidic acid at a concentration of 2 micrograms/ml was bacteriostatic for six isolates and slowed the multiplication of three others. These results show that these compounds could be effective in the phagolysosome of C. burnetii-infected cells.

Nucleotide sequence of the first cosmid from the Mycobacterium leprae genome project: structure and function of the Rif-Str regions

The nucleotide sequence of cosmid B1790, carrying the Rif-Str regions of the Mycobacterium leprae chromosome, has been determined. Twelve open reading frames were identified in the 36716bp sequence, representing 40% of the coding capacity. Five ribosomal proteins, two elongation factors and the beta and beta' subunits of RNA polymerase have been characterized and two novel genes were found. One of these encodes a member of the so-called ABC family of ATP-binding proteins while the other appears to encode an enzyme involved in repairing genomic lesions caused by free radicals. This finding may well be significant as M. leprae, an intracellular pathogen, lives within macrophages.

Pharmacoeconomics of antibacterial treatment

Antibacterial drugs account for between 3 and 25% of all prescriptions, between 6 and 21% of the total market value of drugs in a single country, and up to 50% of the drug budget in hospitals. Bacterial infection is widely perceived as disease caused by harmful outside agents which can be isolated and tested to select the best drug for treatment. In fact, the need for any treatment and the pros and cons of different drugs are just as debatable as in any other therapeutic area. Moreover, the bacteria which make up the normal flora of the body fulfil important roles, so that the ecological implications of treatment for the individual and for society should be considered in assessing the costs and consequences of antibacterial treatment. In this review we outline the most important issues relating to the treatment of bacterial infection in the community and in the hospital, contrasting information from developed and developing countries where appropriate. We review the existing literature on economic evaluation, but in general most of the literature deals with containing the costs of antibacterial drugs in hospitals, and there are many gaps in the literature on cost-effectiveness of treatment. Consequently there are still extreme variations in medical practice which present a challenge for future evaluation. As the outcomes of antibacterial treatment are apparent in a few weeks or months, this is an ideal field for testing pharmacoeconomic methodology. The desire to overcome medical practice variation through consensus statements should be avoided. Instead we recommend wider application of decision analysis to acknowledge that choices exist for the diagnosis and treatment of bacterial infection and to gather information about the implications of these choices. Much of the existing literature would be improved by a more explicit definition of costs. Direct costs to the health services should be distinguished from non medical costs. Moreover, the analysis should consider whether savings from one budget result in costs to another health service budget, or to the patient (transfer costs). These deficiencies in cost analysis will be relatively easy to correct. Of more concern is the fact that the efficacy of much antibacterial treatment is either totally debatable, or variable, depending on factors such as the type of patient treated or the quality of delivery of treatment.(ABSTRACT TRUNCATED AT 400 WORDS)