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

Novel antimycobacterial C-21 amide derivatives of the antibiotic fusidic acid: synthesis, pharmacological evaluation and rationalization of media-dependent activity using molecular docking studies in the binding site of human serum albumin

Fusidic acid is a natural product antibiotic used clinically, primarily against staphylococcal infections. It has also exhibited antimycobacterial activity against Mycobacterium species, including Mycobacterium tuberculosis (Mtb). Novel C-21 fusidic acid amides were synthesized and evaluated for antimycobacterial activity in a drug repositioning approach for tuberculosis. The synthesized compounds exhibited good potency in MB7H9/CAS medium albeit showing low to no activity in MB7H9/ADC medium. The fusidic acid ethanamides were, generally, the most potent of the analogues evaluated for antimycobacterial activity (MIC₉₀ < 10 μM) in the MB7H9/CAS medium. The lack of activity in the MB7H9/ADC medium was supported by strong binding interactions in the fusidic acid binding site of the human serum albumin (HSA) protein. The most potent antimycobacterial analogue was the N-(4-sulfamoylbenzyl)fusidic acid amide (1.26) with an MIC₉₀ value of 2.71 μM.

Therapy for Mycobacterium kansasii Infection: Beyond 2018

The current standard of care therapy for pulmonary Mycobacterium kansasii infection is isoniazid (300 mg/day), rifampin (600 mg/day), and ethambutol (15 mg/kg/day) for 12 months after achieving sputum culture negativity. Rifampin is the key drug in this regimen. The contribution of isoniazid is unclear since its in vitro MICs against M. kansasii are near the peak achievable serum levels and more than 100-fold greater than the MICs for Mycobacterium tuberculosis. Ethambutol likely decreases the emergence of rifampin resistant organisms. There are several new drug classes (e.g., quinolones, macrolides, nitroimidazoles, diarylquinolines, and clofazimine) that exhibit antimycobacterial activities against M. tuberculosis but have not yet been adequately studied against M. kansasii infections. The evaluation of in vitro activities of these agents as well as their study in new regimens in comparison to the standard of care regimen in mouse infection models should be undertaken. This knowledge will inform development of human clinical trials of new regimens in comparison to the current standard of care regimen. It is likely that shorter and more effective therapy is achievable with currently available drugs.

Structure-activity relationships of macrolides against Mycobacterium tuberculosis

Existing 14, 15 and 16-membered macrolide antibiotics, while effective for other bacterial infections, including some mycobacteria, have not demonstrated significant efficacy in tuberculosis. Therefore an attempt was made to optimize this class for activity against Mycobacterium tuberculosis through semisyntheses and bioassay. Approximately 300 macrolides were synthesized and screened for anti-TB activity. Structural modifications on erythromycin were carried out at positions 3, 6, 9, 11, and 12 of the 14-membered lactone ring; as well as at position 4'' of cladinose and position 2' of desosamine. In general, the synthesized macrolides belong to four subclasses: 9-oxime, 11,12-carbamate, 11,12-carbazate, and 6-O-substituted derivatives. Selected compounds were assessed for mammalian cell toxicity and in some cases were further assessed for CYP3A4 inhibition, microsome stability, in vivo tolerance and efficacy. The activity of 11,12-carbamates and carbazates as well as 9-oximes is highly influenced by the nature of the substitution at these positions. For hydrophilic macrolides, lipophilic substitution may result in enhanced potency, presumably by enhanced passive permeation through the cell envelope. This strategy, however, has limitations. Removal of the C-3 cladinose generally reduces the activity. Acetylation at C-2' or 4'' maintains potency of C-9 oximes but dramatically decreases that of 11,12-substituted compounds. Further significant increases in the potency of macrolides for M. tuberculosis may require a strategy for the concurrent reduction of ribosome methylation.

Mycobacterium kansasii: antibiotic susceptibility and PCR-restriction analysis of clinical isolates

Mycobacterium kansasii is the second most common cause of non-tuberculosis mycobacterial diseases in Sao Paulo, Brazil. An important component of the management of infections caused by this organism is antibiotic susceptibility testing. The objective of this study was to determine the drug susceptibility profiles and genotypes of clinical isolates of M. kansasii obtained from patients with or without an infection that met the American Thoracic Society's case definition criteria of M. kansasii disease. One hundred and sixty-nine clinical isolates of M. kansasii collected between 1993 and 1998 in Sao Paulo, Brazil, were tested consecutively. The isolates were genotyped by PCR restriction-enzyme pattern analysis (PRA). Most of the M. kansasii strains were susceptible to isoniazid, streptomycin, rifabutin, rifampicin, clarithromycin, ethionamide, amikacin, clofazimine and cycloserine, and resistant to ethambutol, ciprofloxacin and doxycycline. Of 169 isolates, 167 belonged to the type I PRA genotype and one each belonged to type II and III genotypes. There was no correlation between PRA subtype and M. kansasii disease according to the American Thoracic Society case definition. Clinical trials may be needed to better correlate MIC values with treatment outcomes to identify appropriate parameters for drug-resistance testing of M. kansasii.

In vitro susceptibility of clinical isolates of Brucella melitensis to fucidic acid

Brucella species are facultative intracellular bacteria, and therefore a limited number of antibiotics are effective against these organisms. The side effects of drug combination schemes, and the incidences of relapses and therapeutic failures, have led to investigations of new drugs to treat brucellosis. The purpose of this study was to test the in vitro susceptibility of 50 Brucella melitensis isolates to fucidic acid, which has not previously been used for the treatment of brucellosis. The minimum inhibitory concentrations (MICs) of fucidic acid to 50 B. melitensis isolates that were obtained from blood and bone marrow cultures of patients with brucellosis were studied by the broth microdilution method. The MIC50 and MIC90 values for the 50 B. melitensis strains' susceptibility to fucidic acid were determined to be 0.5 and 2 microg/ml, respectively, and the MIC range was 0.125-2.0 microg/ml. Further experiments are needed to reassess the activity of fucidic acid against intracellular Brucella spp.

In vitro activity of linezolid, clarithromycin and moxifloxacin against clinical isolates of Mycobacterium kansasii

OBJECTIVES

To compare the activity of linezolid with a range of drugs used in the treatment of Mycobacterium kansasii infections.

RESULTS

The percentages of resistant isolates against isoniazid, rifampicin and ethambutol were 2.9%, 1.9% and 2.9%, respectively. All isolates were susceptible to clarithromycin and moxifloxacin both with MIC(90) values of 0.125 mg/L. Linezolid was active against all isolates with MIC(50) and MIC(90) values of 0.5 and 1 mg/L, respectively, both below the susceptibility breakpoint established for mycobacteria.

CONCLUSION

Linezolid, clarithromycin or moxifloxacin, could be used as alternative drugs for treatment of infections due to rifampicin-resistant isolates as well as short-course or intermittent therapy of M. kansasii lung disease.

Epidemiological, clinical and therapeutic features of AIDS-related Mycobacterium kansasii infection during the HIV pandemic: an 11-year follow-up study

OBJECTIVES

Optimal diagnosis and timely treatment of atypical mycobacteriosis, and especially Mycobacterium kansasii disease, remain a serious challenge for clinicians engaged in the management of the immunocompromised host.

METHODS AND RESULTS

From more than 2700 hospitalizations (over 1800 patients) attributable to HIV-associated disorders over an 11-year period, 12 patients were found to have a confirmed M. kansasii infection. This reflects the recent reduction in the frequency of this HIV-related complication, which virtually disappeared after the introduction of potent antiretroviral combinations in 1996. In the early 1990s, the lack of effective antiretroviral regimens made frequent the association with AIDS, a mean CD4 lymphocyte count of nearly 20 cells/microL, and an extremely variable chest X-ray features. The recent detection of a further case was attributable to late recognition of very advanced HIV disease, complicated by multiple opportunistic disorders.

CONCLUSIONS

Mycobacterium kansasii respiratory or disseminated infection continues to occur, and poses diagnostic problems in terms of late or missed identification as a result of slow culture and frequently concurrent opportunistic disease. Serious therapeutic difficulties also arise from the unpredictable in vitro antimicrobial susceptibility profile of these organisms, and from the need to start an effective combination therapy that does not interfere with other medications as soon as possible.

Mycobacterium kansasii septic arthritis: French retrospective study of 5 years and review

Septic arthritis due to Mycobacterium kansasii is rare; only 40 cases have been published. A French national inquiry revealed the occurrence of 10 new cases between 1992 and 1997 (8 men and 2 women: mean age, 37 years; range, 25-54 years). Seven had an underlying condition: AIDS (n=4), chronic skin psoriasis and AIDS (n=2), or a renal transplant (n=1). Trauma to the joint, use of intra-articular corticosteroid(s) 1 month to 2 years after the event, and chronic skin psoriasis were risk factors. The mean interval between appearance of the first symptoms of arthritis and the diagnosis was 5 months. Monarthritis was localized to the knee (n=4), wrist (n=3), finger (n=1), elbow (n=1), or ankle (n=1). The main diagnostic procedure was culture of a synovial biopsy specimen. In all cases, debridement was associated with antimycobacterial treatment. Three patients died of AIDS during treatment, and another is still undergoing treatment; the other 6 patients were cured. M. kansasii infection should be considered in all cases of indolent arthritis with any of the following risk factors: local trauma, local or systemic corticosteroid therapy, chronic skin psoriasis, and immunodepression, especially that due to human immunodeficiency virus infection.

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.

Cutaneous Mycobacterium kansasii infection in a patient with systemic lupus erythematosus: case report and review

Mycobacterium kansasii infections of the skin have been described in 31 previously published cases. The median age of these patients is 43 years, and male patients are more frequently affected than female patients. Most patients (72%) with this infection have some alteration of their immune status, but disseminated infection is relatively uncommon (22%). We present the first reported case of cutaneous M. kansasii infection in a patient with previously diagnosed systemic lupus erythematosus. The clinical presentation is similar to that expected in lupus profundus. While the duration of treatment is long (18 months), this case demonstrates that rifampin combined with at least 2 other antibiotics can provide excellent results. Clarithromycin has demonstrated encouraging in vitro results against M. kansasii but has not yet been reported for treatment of cutaneous infections.

AIDS-related Mycobacterium kansasii infection with initial resistance to clarithromycin

Clarithromycin is a promising drug for the treatment of Mycobacterium kansasii infection. We report a patient with AIDS and severe M. kansasii infection who had previously received a short course of clarithromycin for sinusitis. He had clinical failure of treatment using clarithromycin plus ethambutol, and the initial isolate was found to be highly resistant to clarithromycin. Nucleotide sequencing of the 23S rRNA gene of this isolate demonstrated a single base mutation at position 2058, the same as that found in clarithromycin-resistant Mycobacterium avium.

Skin lesions in a patient with hairy cell leukaemia

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Sparfloxacin worldwide in vitro literature: isolate data available through 1994

Sparfloxacin is a piperazinyl, cyclopropyl-fluoroquinolone with broad-spectrum antibacterial activity. Compared to other quinolones, sparfloxacin displays improved activity against a variety of pathogens including Staphylococcus, Streptococcus, Enterococcus, Chlamydia, Mycoplasma, Ureaplasma, and Mycobacteria species. Other susceptible organism group include Haemophilus, Legionella, Moraxella, Neisseria, Aeromonas, Acinetobacter, Bordetella, Brucella, Campylobacter, Gardnerella, and Helicobacter species. Most Enterobacteriaceae are also susceptible, whereas most isolates of Pseudomonas aeruginosa are not. Sparfloxacin is bactericidal. Activity is generally stable to variations of inoculum, pH, and cation concentration, and it is unchanged in the presence of 5% sodium cholate or 70% human serum. Susceptibility to the drug is diminished in urine. Cross-resistance, although incomplete, has been documented with other quinolones, but not with other antimicrobic classes.