Activities of sitafloxacin (DU-6859a), either singly or in combination with rifampin, against Mycobacterium ulcerans infection in mice

Antibacterial Mechanisms and Clinical Impact of Sitafloxacin

Sitafloxacin is a 4th generation fluoroquinolone antibiotic with broad activity against a wide range of Gram-negative and Gram-positive bacteria. It is approved in Japan and used to treat pneumonia and urinary tract infections (UTIs) as well as other upper and lower respiratory infections, genitourinary infections, oral infections and otitis media. Compared to other fluoroquinolones, sitafloxacin displays a low minimal inhibitory concentration (MIC) for many bacterial species but also activity against anaerobes, intracellular bacteria, and persisters. Furthermore, it has also shown strong activity against biofilms of P. aeruginosa and S. aureus in vitro, which was recently validated in vivo with murine models of S. aureus implant-associated bone infection. Although limited in scale at present, the published literature supports the further evaluation of sitafloxacin in implant-related infections and other biofilm-related infections. The aim of this review is to summarize the chemical-positioning-based mechanisms, activity, resistance profile, and future clinical potential of sitafloxacin.

In Vivo Imaging of Bioluminescent Mycobacterium ulcerans: A Tool to Refine the Murine Buruli Ulcer Tail Model

Buruli ulcer (BU) is a neglected tropical disease caused by infection with Mycobacterium ulcerans. Unclear transmission, no available vaccine, and suboptimal treatment regimens hamper the control of this disease. Carefully designed preclinical research is needed to address these shortcomings. In vivo imaging (IVIS^®, Perkin Elmer, Waltham, MA) of infection is an emerging tool that permits monitoring of disease progression and reduces the need to using large numbers of mice at different time-points during the experiment, as individual mice can be imaged at multiple time-points. We aimed to further describe the use of in vivo imaging (IVIS) in BU. We studied the detection of M. ulcerans in experimentally infected BALB/c mouse tails and the subsequent histopathology and immune response in this pilot study. IVIS-monitoring was performed weekly in ten infected BALB/c mice to measure light emitted as a proxy for bacterial load. Nine of 10 (90%) BALB/c mice infected subcutaneously with 3.3 × 10⁵ M. ulcerans JKD8049 (containing pMV306 hsp16+luxG13) exhibited light emission from the site of infection, indicating M. ulcerans growth in vivo, whereas only five of 10 (50%) animals developed clinical signs of the disease. Specific antibody titers were detected within 2 weeks of the infection. Interferon (IFN)-γ and interleukin (IL)-10 were elevated in animals with pathology. Histopathology revealed clusters of acid-fast bacilli in the subcutaneous tissue, with macrophage infiltration and granuloma formation resembling human BU. Our study successfully showed the utility of M. ulcerans IVIS monitoring and lays a foundation for further research.

Isoniazid Pharmacokinetics in the Presence of Ofloxacin and Norfloxacin Antibiotics

The in vivo effects of norfloxacin (NXC) and ofloxacin (OXC) on isoniazid (INH) pharmacokinetics were investigated in 5 apparently healthy volunteers aged 18-39 years after an informed consent. The study was carried out in 3 phases with an interval drug wash out period of at least 1 week in between the phases. In phase 1 (INH alone), subject received 300 mg (usual adult dose) of INH. In phase 2 (INH + OXC), 300 mg of INH was coadministered with 200 mg of OXC, and in phase 3 (INH + NXC) each received 300 mg of INH together with 400 mg of NXC after 1-week drug wash period. Drugs were taken orally with 350 mL of water after an overnight fast, and the subject fasted 3 hours after drug. Plasma, saliva, and urine concentration of INH were predetermined at zero hour, then hourly until the eighth hour, 12 hours, 24 hours, and finally at 48 hours. The urine samples were further collected at 72 hours after drug(s) administration using validated methods. Various pharmacokinetics parameters were calculated. Various pharmacokinetic parameters of INH significantly differed when administered alone or in combination with OXC or with NXC. The mean saliva to plasma ratio of INH concentration was 0.14. The bioavailability indices of INH in the saliva and plasma were similar in all the groups. NXC and OXC reduced the extent and rate of absorption of INH. The determination of INH levels in saliva may be useful in therapeutic drug monitoring and pharmacokinetic studies.

Successful outcomes with oral fluoroquinolones combined with rifampicin in the treatment of Mycobacterium ulcerans: an observational cohort study

Background

The World Health Organization currently recommends combined streptomycin and rifampicin antibiotic treatment as first-line therapy for Mycobacterium ulcerans infections. Alternatives are needed when these are not tolerated or accepted by patients, contraindicated, or neither accessible nor affordable. Despite in vitro effectiveness, clinical evidence for fluoroquinolone antibiotic use against Mycobacterium ulcerans is lacking. We describe outcomes and tolerability of fluoroquinolone-containing antibiotic regimens for Mycobacterium ulcerans in south-eastern Australia.

Methodology/Principal Findings

Analysis was performed of prospectively collected data including all primary Mycobacterium ulcerans infections treated at Barwon Health between 1998 and 2010. Medical treatment involved antibiotic use for more than 7 days; surgical treatment involved surgical excision of a lesion. Treatment success was defined as complete lesion healing without recurrence at 12 months follow-up. A complication was defined as an adverse event attributed to an antibiotic that required its cessation. A total of 133 patients with 137 lesions were studied. Median age was 62 years (range 3–94 years). 47 (34%) had surgical treatment alone, and 90 (66%) had combined surgical and medical treatment. Rifampicin and ciprofloxacin comprised 61% and rifampicin and clarithromycin 23% of first-line antibiotic regimens. 13/47 (30%) treated with surgery alone failed treatment compared to 0/90 (0%) of those treated with combination medical and surgical treatment (p<0.0001). There was no difference in treatment success rate for antibiotic combinations containing a fluoroquinolone (61/61 cases; 100%) compared with those not containing a fluoroquinolone (29/29 cases; 100%). Complication rates were similar between ciprofloxacin and rifampicin (31%) and rifampicin and clarithromycin (33%) regimens (OR 0.89, 95% CI 0.27–2.99). Paradoxical reactions during treatment were observed in 8 (9%) of antibiotic treated cases.

Conclusions

Antibiotics combined with surgery may significantly increase treatment success for Mycobacterium ulcerans infections, and fluoroquinolone combined with rifampicin-containing antibiotic regimens can provide an effective and safe oral treatment option.

Buruli ulcer is a necrotizing infection of skin and subcutaneous tissue caused by Mycobacterium ulcerans and is the third most common mycobacterial disease worldwide (after tuberculosis and leprosy). In recent years its treatment has radically changed, evolving from a predominantly surgically to a predominantly medically treated disease. The World Health Organization now recommends combined streptomycin and rifampicin antibiotic treatment as first-line therapy for Mycobacterium ulcerans infections. However, alternatives are needed where recommended antibiotics are not tolerated or accepted by patients, contraindicated, or not accessible nor affordable. This study describes the use of antibiotics, including oral fluoroquinolones, in the treatment of Mycobacterium ulcerans in south-eastern Australia. It demonstrates that antibiotics combined with surgery are highly effective in the treatment of Mycobacterium ulcerans. In addition, oral fluoroquinolone-containing antibiotic combinations are shown to be as effective and well tolerated as other recommended antibiotic combinations. Fluoroquinolone antibiotics therefore offer the potential to provide an alternative oral antibiotic to be combined with rifampicin for Mycobacterium ulcerans treatment, allowing more accessible and acceptable, less toxic, and less expensive treatment regimens to be available, especially in resource-limited settings where the disease burden is greatest.

Fighting mycobacterial infections by antibiotics, phytochemicals and vaccines

Buruli ulcer is a neglected disease caused by Mycobacterium ulcerans and represents the world's third most common mycobacterial infection. It produces the polyketide toxins, mycolactones A, B, C and D, which induce apoptosis and necrosis. Clinical symptoms are subcutaneous nodules, papules, plaques and ulcerating oedemae, which can enlarge and destroy nerves and blood vessels and even invade bones by lymphatic or haematogenous spread (osteomyelitis). Patients usually do not suffer from pain or systematic inflammation. Surgery is the treatment of choice, although recurrence is common and wide surgical excisions including healthy tissues result in significant morbidity. Antibiotic therapy with rifamycins, aminoglycosides, macrolides and quinolones also improves cure rates. Still less exploited treatment options are phytochemicals from medicinal plants used in affected countries. Vaccination against Buruli ulcer is still in its infancy.

Successful treatment of Mycobacterium ulcerans osteomyelitis with minor surgical debridement and prolonged rifampicin and ciprofloxacin therapy: a case report

Introduction

Treatment for osteomyelitis-complicating Mycobacterium ulcerans infection typically requires extensive surgery and even amputation, with no reported benefit from adjunctive antibiotics.

Case presentation

We report a case of an 87-year-old woman with M. ulcerans osteomyelitis that resolved following limited surgical debridement and 6 months of therapy with rifampicin and ciprofloxacin.

Conclusion

M. ulcerans osteomyelitis can be successfully treated with limited surgical debridement and adjunctive oral antibiotics.

Outcomes for Mycobacterium ulcerans infection with combined surgery and antibiotic therapy: findings from a south-eastern Australian case series

OBJECTIVE

To describe the effect of antibiotics on outcomes of treatment for Buruli or Bairnsdale ulcer (BU) in patients on the Bellarine Peninsula in south-eastern Australia.

DESIGN

Observational, non-randomised study with data collected prospectively or through medical record review.

PATIENTS AND SETTING

All 40 patients with BU managed by staff of Barwon Health's Geelong Hospital (a public, secondary-level hospital) between 1 January 1998 and 31 December 2004.

MAIN OUTCOME MEASURES

Epidemiology, clinical presentation, diagnosis, treatment and clinical outcomes.

RESULTS

There were 59 treatment episodes; 29 involved surgery alone, 26 surgery plus antibiotics, and four antibiotics alone. Of 55 episodes where surgery was performed, minor surgery was required in 22, and major surgery in 33. Failure rates were 28% for surgery alone, and 19% for surgery plus antibiotics. Adjunctive antibiotic therapy was associated with increased treatment success for lesions with positive histological margins (P < 0.01), and lesions requiring major surgery for treatment of a first episode (P < 0.01). The combination of rifampicin and ciprofloxacin resulted in treatment success in eight of eight episodes, and no patients ceased therapy because of side effects with this regimen.

CONCLUSIONS

Adjunctive antibiotic therapy may increase the effectiveness of BU surgical treatment, and this should be further assessed by larger randomised controlled trials. The combination of rifampicin and ciprofloxacin appears the most promising.

Mycobacterium ulcerans infection: control, diagnosis, and treatment

The skin disease Buruli ulcer, caused by Mycobacterium ulcerans, is the third most common mycobacterial disease after tuberculosis and leprosy and mainly affects remote rural African communities. Although the disease is known to be linked to contaminated water, the mode of transmission is not yet understood, which makes it difficult to propose control interventions. The disease is usually detected in its later stages, when it has caused substantial damage and disability. Surgery remains the treatment of choice. Although easy and effective in the early stages of the disease, treatment requires extended excisions and long hospitalisation for the advanced forms of the disease. Currently, no antibiotic treatment has proven effective for all forms of M ulcerans infection and research into a new vaccine is urgently needed. While the scientific community works on developing non-invasive and rapid diagnostic tools, the governments of endemic countries should implement active case finding and health education strategies in their affected communities to detect the disease in its early stages. We review the diagnosis, treatment, and control of Buruli ulcer and list priorities for research and development.

Efficacy of the combination rifampin-streptomycin in preventing growth of Mycobacterium ulcerans in early lesions of Buruli ulcer in humans

Mycobacterium ulcerans disease is common in some humid tropical areas, particularly in parts of West Africa, and current management is by surgical excision of skin lesions ranging from early nodules to extensive ulcers (Buruli ulcer). Antibiotic therapy would be more accessible to patients in areas of Buruli ulcer endemicity. We report a study of the efficacy of antibiotics in converting early lesions (nodules and plaques) from culture positive to culture negative. Lesions were excised either immediately or after treatment with rifampin orally at 10 mg/kg of body weight and streptomycin intramuscularly at 15 mg/kg of body weight daily for 2, 4, 8, or 12 weeks and examined by quantitative bacterial culture, PCR, and histopathology for M. ulcerans. Lesions were measured during treatment. Five lesions excised without antibiotic treatment and five lesions treated with antibiotics for 2 weeks were culture positive, whereas three lesions treated for 4 weeks, five treated for 8 weeks, and three treated for 12 weeks were culture negative. No lesions became enlarged during antibiotic treatment, and most became smaller. Treatment with rifampin and streptomycin for 4 weeks or more inhibited growth of M. ulcerans in human tissue, and it provides a basis for proceeding to a trial of antibiotic therapy as an alternative to surgery for early M. ulcerans disease.

Mycolactones and Mycobacterium ulcerans disease

CONTEXT

Mycobacterium ulcerans causes devastating necrotic lesions in affected individuals. The disease, commonly called Buruli ulcer, is increasing in prevalance in western African countries. Treatment is mainly surgical; no clinical trials have been done to support the use of antimycobacterial drugs. A secreted polyketide toxin, mycolactone, is responsible for the tissue damage; its chemical structure has been elucidated.

STARTING POINT

Although the main treatment is surgical, many patients with Buruli ulcer present late because of unusual beliefs about the disease and its treatment. Isabelle Aujoulat and colleagues recently showed, in a study in southern Bénin, Africa (Trop Med Int Health 2003; 8: 750-59), that although the ulcer is well recognised, the cause is often seen as environmental or because of witchcraft. In addition, treatment is thought to be destructive, costly, and ineffective. WHERE NEXT? Antimycobacterial drug regimens that hold promise based on animal and preliminary human studies will soon be tested in large well-designed controlled clinical trials. Information gleaned from the genomic sequence of M ulcerans could be used to design more effective vaccines, or new drug targets (eg, that knock out the enzymes of M ulcerans that synthesise mycolactone species).