Rifaximin potentiates clarithromycin against Mycobacterium abscessus in vitro and in zebrafish

Background

Mycobacterium abscessus is a non-tuberculous mycobacterium (NTM) that causes chronic pulmonary infections. Because of its extensive innate resistance to numerous antibiotics, treatment options are limited, often resulting in poor clinical outcomes. Current treatment regimens usually involve a combination of antibiotics, with clarithromycin being the cornerstone of NTM treatments.

Objectives

To identify drug candidates that exhibit synergistic activity with clarithromycin against M. abscessus.

Methods

We performed cell-based phenotypic screening of a compound library against M. abscessus induced to become resistant to clarithromycin. Furthermore, we evaluated the toxicity and efficacy of the top compound in a zebrafish embryo infection model.

Results

The screen revealed rifaximin as a clarithromycin potentiator. The combination of rifaximin and clarithromycin was synergistic and bactericidal in vitro and potent in the zebrafish model.

Conclusions

The data indicate that the rifaximin/clarithromycin combination is promising to effectively treat pulmonary NTM infections.

Mycobacterial endocarditis: a comprehensive review

OBJECTIVE

A systematic analysis was made in view of the epidemiology, clinical features, diagnosis, treatment and main outcomes of mycobacterial endocarditis.

METHODS

The data source of the present study was based on a comprehensive literature search in MEDLINE, Highwire Press and Google search engine for publications on mycobacterial endocarditis published between 2000 and 2013.

RESULTS

The rapidly growing mycobacteria become the predominant pathogens with Mycobacterium chelonae being the most common. This condition has changed significantly in terms of epidemiology since the 21st century, with more broad patient age range, longer latency, prevailed mitral valve infections and better prognosis.

CONCLUSION

Mycobacterial endocarditis is rare and the causative pathogens are predominantly the rapidly growing mycobacteria. Amikacin, ciprofloxacin and clarithromycin are the most frequently used targeted antimicrobial agents but often show poor responses. Patients with deep infections may warrant a surgical operation or line withdrawal. With periodic multidrug therapy guided by drug susceptibility testing, and surgical managements, patients may achieve good therapeutic results.

Clinical significance of respiratory isolates for Mycobacterium abscessus complex from pediatric patients

Mycobacterium abscessus complex is the most virulent of rapidly growing mycobacteria causing invasive lung disease. To better delineate clinical pediatric experience and outcomes with M. abscessus complex, we retrospectively gathered 5-year data on M. abscessus complex infection and outcomes in a large, hospital-based pediatric pulmonary center. Patients were selected from the database of the microbiology department at Miller Children's Hospital in Long Beach, CA. Patients had at least one positive pulmonary isolate for M. abscessus complex from February 2006 to May 2011. Treatment modality data were collected and successful therapy of disease was determined as clearance of M. abscessus complex infection after antibiotics proven by culture negative respiratory isolate within at least 12 months of therapy initiation. Two cystic fibrosis patients with M. abscessus complex were identified, one with failed therapy and the other with stable pulmonary status despite persistent isolation. One primary ciliary dyskinesia patient had successful clearance of M. abscessus complex, however is now growing M. avium intracellulare. A patient with no prior medical history was successfully treated with antimycobacterial therapy. Eleven patients with neuromuscular disorders had tracheal aspirates positive for M. abscessus complex. None were treated due to stable lung status and all but two had spontaneous clearance of the mycobacteria. The two remaining persist with sporadic isolation of M. abscessus complex without clinical significance. We concluded that patients with tracheostomy associated M. abscessus complex infections do not appear to require treatment and often have spontaneous resolution. Cystic fibrosis or primary ciliary dyskinesia patients may have clinical disease warranting treatment, but current antimycobacterial therapy has not proven to be completely successful. As M. abscessus complex gains prevalence, standardized guidelines for diagnosis and therapy are needed in the pediatric population. Multicenter cohort analysis is necessary to achieve such guidelines.

Clinical and microbiological differences between Mycobacterium abscessus and Mycobacterium massiliense lung diseases

In recent years, many novel nontuberculous mycobacterial species have been discovered through genetic analysis. Mycobacterium massiliense and M. bolletii have recently been identified as species separate from M. abscessus. However, little is known regarding their clinical and microbiological differences in Japan. We performed a molecular identification of stored M. abscessus clinical isolates for further identification. We compared clinical characteristics, radiological findings, microbiological findings, and treatment outcomes among patients with M. abscessus and M. massiliense lung diseases. An analysis of 102 previous isolates of M. abscessus identified 72 (71%) M. abscessus, 27 (26%) M. massiliense, and 3 (3%) M. bolletii isolates. Clinical and radiological findings were indistinguishable between the M. abscessus and M. massiliense groups. Forty-two (58%) patients with M. abscessus and 20 (74%) patients with M. massiliense infections received antimicrobial treatment. Both the M. abscessus and M. massiliense groups showed a high level of resistance to all antimicrobials, except for clarithromycin, kanamycin, and amikacin. However, resistance to clarithromycin was more frequently observed in the M. abscessus than in the M. massiliense group (16% and 4%, respectively; P = 0.145). Moreover, the level of resistance to imipenem was significantly lower in M. abscessus isolates than in M. massiliense isolates (19% and 48%, respectively; P = 0.007). The proportions of radiological improvement, sputum smear conversion to negativity, and negative culture conversion during the follow-up period were higher in patients with M. massiliense infections than in those with M. abscessus infections. Patients with M. massiliense infections responded more favorably to antimicrobial therapy than those with M. abscessus infections.

Clarithromycin and amikacin vs. clarithromycin and moxifloxacin for the treatment of post-acupuncture cutaneous infections due to Mycobacterium abscessus: a prospective observational study

An outbreak of post-acupuncture cutaneous infections due to Mycobacterium abscessus occurred in Ansan, Korea, from November 2007 through to May 2008. During this time a prospective, observational, non-randomized study was conducted involving 52 patients that were diagnosed with cutaneous M. abscessus infection. We compared the clinical response between patients treated with clarithromycin plus amikacin regimen and those treated with clarithromycin plus moxifloxacin regimens with regard to time to resolution of the cutaneous lesions. Among the 52 study patients, 33 were treated with clarithromycin plus amikacin, and 19 were treated with clarithromycin plus moxifloxacin. The baseline characteristics for the treatment groups were not significantly different, except for initial surgical excision (n = 27 vs. 6, respectively, p = 0.001). The median time (weeks) to resolution of the lesions in the clarithromycin plus moxifloxacin-treated subjects was significantly shorter than that in the clarithromycin plus amikacin-treated subjects (17 ± 1.1 vs. 20 ± 0.9, respectively, p = 0.017). With adjustments for age, location of lesions, prior incision and drainage, and excision during medical therapy, clarithromycin plus moxifloxacin-treated subjects were more likely to have resolved lesions (hazard ratio, 0.387; 95% confidence interval, 0.165-0.907; p = 0.029). The frequency of drug-related adverse events in the two treatment groups was not significantly different (n = 18 vs. 14, respectively; p = 0.240). The most common adverse event was gastrointestinal discomfort. The results of our study showed that the combination regimen of clarithromycin and moxifloxacin resulted in a better clinical response than a regimen of clarithromycin plus amikacin when used for treatment of cutaneous M. abscessus infection.

Antibiotic treatment of Mycobacterium abscessus lung disease: a retrospective analysis of 65 patients

RATIONALE

The optimal therapeutic regimen and duration of treatment for Mycobacterium abscessus lung disease is not well established.

OBJECTIVES

To assess the efficacy of a standardized combination antibiotic therapy for the treatment of M. abscessus lung disease.

METHODS

Sixty-five patients (11 males, 55 females, median age 55 yr) with M. abscessus lung disease were treated with clarithromycin, ciprofloxacin, and doxycycline, together with an initial regimen of amikacin and cefoxitin for the first 4 weeks of hospitalization.

MEASUREMENTS AND MAIN RESULTS

Treatment response rates were 83% for symptoms and 74% for high-resolution computed tomography. Sputum conversion and maintenance of negative sputum cultures for more than 12 months was achieved in 38 (58%) patients. These rates were significantly lower in patients whose isolates were resistant to clarithromycin (17%, 2/12) compared with those whose isolates were susceptible or intermediate to clarithromycin (64%, 21/33; P = 0.007). Neutropenia and thrombocytopenia associated with cefoxitin developed in 33 (51%) and 4 (6%) patients, respectively. Drug-induced hepatotoxicity occurred in 10 (15%) patients. Because of these adverse reactions, cefoxitin was discontinued in 39 (60%) patients after treatment for a median of 22 days.

CONCLUSIONS

Standardized combination antibiotic therapy was moderately effective in treating M. abscessus lung disease. However, frequent adverse reactions and the potential for long-duration hospitalization are important problems that remain to be solved.