Clinical significance of differentiation of Mycobacterium massiliense from Mycobacterium abscessus

Mycobacterium abscessus multispacer sequence typing

BACKGROUND

Mycobacterium abscessus group includes antibiotic-resistant, opportunistic mycobacteria that are responsible for sporadic cases and outbreaks of cutaneous, pulmonary and disseminated infections. However, because of their close genetic relationships, accurate discrimination between the various strains of these mycobacteria remains difficult. In this report, we describe the development of a multispacer sequence typing (MST) analysis for the simultaneous identification and typing of M. abscessus mycobacteria. We also compared MST with the reference multilocus sequence analysis (MLSA) typing method.

RESULTS

Based on the M. abscessus CIP104536T genome, eight intergenic spacers were selected, PCR amplified and sequenced in 21 M. abscessus isolates and analysed in 48 available M. abscessus genomes. MST and MLSA grouped 37 M. abscessus organisms into 12 and nine types, respectively; four formerly "M. bolletii" organisms and M. abscessus M139 into three and four types, respectively; and 27 formerly "M. massiliense" organisms grouped into nine and five types, respectively. The Hunter-Gaston index was off 0.912 for MST and of 0.903 for MLSA. The MST-derived tree was similar to that based on MLSA and rpoB gene sequencing and yielded three main clusters comprising each the type strain of the respective M. abscessus sub-species. Two isolates exhibited discordant MLSA- and rpoB gene sequence-derived position, one isolate exhibited discordant MST- and rpoB gene sequence-derived position and one isolate exhibited discordant MST- and MLSA-derived position. MST spacer n°2 sequencing alone allowed for the accurate identification of the different isolates at the sub-species level.

CONCLUSIONS

MST is a new sequencing-based approach for both identifying and genotyping M. abscessus mycobacteria that clearly differentiates formerly "M. massiliense" organisms from other M. abscessus subsp. bolletii organisms.

Update in tuberculosis and nontuberculous mycobacterial disease 2011

The number of tuberculosis (TB) cases and global TB incidence rates is decreasing according to the latest World Health Organization Global Tuberculosis Report (1). This is very welcome news. However, the 8.8 million incident cases of TB, 1.1 million deaths from TB among HIV-negative people, the 350,000 deaths from HIV-associated TB, and the millions of children orphaned as a result of parental deaths caused by TB provide a stark reminder of the magnitude of devastation caused by TB each year. Advances in understanding TB epidemiology diagnosis and treatment in 2011, many of which were reported in the Journal, provide hope that the annual decline in TB cases will accelerate.

Otitis media and otomastoiditis caused by Mycobacterium massiliense (Mycobacterium abscessus subsp. bolletii)

We describe two patients with otologic infections caused by Mycobacterium massiliense (M. abscessus subsp. bolletti) which were identified using erm(41) PCR, 23S rRNA, and rpoB gene sequence analysis. They were middle-aged adults with underlying otologic diseases and were treated successfully with clarithromycin-based combination regimens for 3 and 9 months, respectively.

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.

Macrolide treatment for Mycobacterium abscessus and Mycobacterium massiliense infection and inducible resistance

RATIONALE

Macrolides, such as clarithromycin (CLR) and azithromycin (AZM), are frequently the only oral antibiotics that are active against Mycobacterium abscessus and M. massiliense infections.

OBJECTIVES

To compare the activity of CLR and AZM in experimental models.

METHODS

We compared the treatment efficacies of CLR and AZM and determined the correlation between efficacy and induced erythromycin ribosome methyltransferase gene (erm)(41) expression in experimental models of M. abscessus and M. massiliense infections.

MEASUREMENTS AND MAIN RESULTS

In all tested M. abscessus isolates, a high level of inducible CLR resistance developed (minimal inhibitory concentration [MIC] on Day 3 versus Day 14; P < 0.001). Whereas the AZM MIC increased on Day 14 (P < 0.01 versus Day 3), the level was significantly lower than the CLR MIC on Day 14 (P < 0.001). However, the MICs of CLR and AZM for the M. massiliense isolates did not change. Compared with CLR, AZM presented greater antibiotic activity against M. abscessus in vitro, ex vivo, and in vivo (P < 0.05), whereas both macrolides were comparably effective against M. massiliense. In M. abscessus infection, the level of erm(41) expression was higher after exposure to CLR than after exposure to AZM (P < 0.001). Experiments using an erm(41)-knockout M. abscessus mutant and an M. massiliense transformant expressing M. abscessus erm(41) confirmed that erm(41) was responsible for inducible CLR resistance.

CONCLUSIONS

CLR induces greater erm(41) expression and thus higher macrolide resistance than AZM in M. abscessus infection. AZM may be more effective against M. abscessus, whereas both macrolides appear to be equally effective against M. massiliense.

A case of empyema necessitatis caused by Mycobacterium abscessus

Non-tuberculosis mycobacteria (NTM) have emerged as an important pathogen in lung infection. NTM infection is rarely accompanied by pleural involvement, and empyema necessitatis caused by NTM is very uncommon. We report a very rare case of Mycobacterium abscessus pulmonary disease with empyema accompanied by empyema necessitatis. The patient was successfully treated by percutaneous tube drainage of the empyema and empyema necessitatis with aggressive antibiotics treatment and surgical resection.

Performance assessment of the DR. TBDR/NTM IVD kit for direct detection of Mycobacterium tuberculosis isolates, including rifampin-resistant isolates, and nontuberculous Mycobacteria

We evaluated the performance of the DR. TBDR/NTM IVD kit, which was designed to detect Mycobacterium tuberculosis, rifampin-resistant M. tuberculosis, and nontuberculous mycobacteria, for detecting 110 positive and 50 negative cultures in Mycobacterium Growth Indicator Tubes. The accuracy rate of this kit for identification of Mycobacterium species was 95.5% (105/110).

Antimicrobial susceptibility testing, drug resistance mechanisms, and therapy of infections with nontuberculous mycobacteria

Within the past 10 years, treatment and diagnostic guidelines for nontuberculous mycobacteria have been recommended by the American Thoracic Society (ATS) and the Infectious Diseases Society of America (IDSA). Moreover, the Clinical and Laboratory Standards Institute (CLSI) has published and recently (in 2011) updated recommendations including suggested antimicrobial and susceptibility breakpoints. The CLSI has also recommended the broth microdilution method as the gold standard for laboratories performing antimicrobial susceptibility testing of nontuberculous mycobacteria. This article reviews the laboratory, diagnostic, and treatment guidelines together with established and probable drug resistance mechanisms of the nontuberculous mycobacteria.

Discovery of a novel hsp65 genotype within Mycobacterium massiliense associated with the rough colony morphology

So far, genetic diversity among strains within Mycobacterium massiliense has rarely been studied. To investigate the genetic diversity among M. massiliense, we conducted phylogenetic analysis based on hsp65 (603-bp) and rpoB (711-bp) sequences from 65 M. massiliense Korean isolates. We found that hsp65 sequence analysis could clearly differentiate them into two distinct genotypes, Type I and Type II, which were isolated from 35 (53.8%) and 30 patients (46.2%), respectively. The rpoB sequence analysis revealed a total of four genotypes (R-I to R-IV) within M. massiliense strains, three of which (R-I, R-II and R-III) correlated with hsp65 Type I, and other (R-IV), which correlated with Type II. Interestingly, genotyping by the hsp65 method agreed well with colony morphology. Despite some exceptions, Type I and II correlated with smooth and rough colonies, respectively. Also, both types were completely different from one another in terms of MALDI-TOF mass spectrometry profiles of whole lipid. In addition, we developed PCR-restriction analysis (PRA) based on the Hinf I digestion of 644-bp hsp65 PCR amplicons, which enables the two genotypes within M. massiliense to be easily and reliably separated. In conclusion, two distinct hsp65 genotypes exist within M. massiliense strains, which differ from one another in terms of both morphology and lipid profile. Furthermore, our data indicates that Type II is a novel M. massiliense genotype being herein presented for the first time. The disparity in clinical traits between these two hsp65 genotypes needs to be exploited in the future study.

Activities of moxifloxacin in combination with macrolides against clinical isolates of Mycobacterium abscessus and Mycobacterium massiliense

Infections caused by Mycobacterium abscessus and Mycobacterium massiliense are on the rise among humans. Although macrolides, including clarithromycin (CLR) and azithromycin (AZM), are key antibiotics for the treatment of M. abscessus and M. massiliense infections, treatment regimens for these infections are still largely undefined. In this study, we evaluated the in vitro, ex vivo, and in vivo activities of moxifloxacin (MXF) in combination with macrolides against clinically isolated M. abscessus and M. massiliense strains. Overall, CLR, AZM, and MXF alone showed activity against both species in vitro, ex vivo, and in vivo. When MXF was combined with a macrolide against M. abscessus isolates, antagonism was observed in 65.4% (17/26) of the strains with CLR and 46.2% (12/26) of the strains with AZM in vitro as well as in 66.7% (10/15) of the strains with CLR and 40.0% (6/15) of the strains with AZM in macrophages as determined by the fractional inhibitory concentration index. In contrast, either indifferent or synergistic effects of the MXF-macrolide combinations were observed against only M. massiliense strains. Moreover, a murine infection model showed similar results. Antagonism between the MXF and macrolide combinations was observed in five out of seven M. abscessus strains, while indifferent and synergistic effects for these combinations were observed for three of the six M. massiliense strains tested, respectively. In conclusion, the activity of MXF in combination with a macrolide differed for M. abscessus and M. massiliense infections and the addition of MXF to macrolide therapy had no benefit for the treatment of M. abscessus infections.

Impaired Expression of MAPK Is Associated with the Downregulation of TNF-α, IL-6, and IL-10 in Mycobacterium abscessus Lung Disease

Background

Healthy individuals who develop nontuberculous mycobacteria (NTM) lung disease are likely to have specific susceptibility factors which can lead to a NTM infection. The aim of the present study was to investigate the mechanism underlying innate immune responses, including the role of mitogen-activated protein kinase (MAPK), in Mycobacterium abscessus lung disease.

Methods

Extracellular signal-regulated kinase (ERK1/2) and p38 MAPK expression in monocytes from peripheral blood mononuclear cells were measured by Western blot analysis after stimulation by Mycobacterium avium in five patients with M. abscessus lung disease and seven healthy controls. A M. avium-induced cytokine assay was performed after inhibition of ERK1/2 and p38 MAPK pathways.

Results

Mycobacterium avium induced p38 and ERK1/2 expression in monocytes from healthy controls and subsequently upregulated tumor necrosis factor (TNF)-α, interleukin (IL)-6, and IL-10 production. In monocytes from patients with M. abscessus lung disease, however, induction of p38 and ERK1/2 expression, and the production of TNF-α, IL-6, and IL-10 were significantly lower.

Conclusion

Decreased activity of MAPK and cytokine secretion in monocytes from patients with M. abscessus lung disease may provide an explanation regarding host susceptibility to these uncommon infections.

CNS infections caused by Mycobacterium abscessus complex: clinical features and antimicrobial susceptibilities of isolates

OBJECTIVES

CNS infections caused by non-tuberculous mycobacteria (NTM) are rare and only three cases of CNS infections due to Mycobacterium abscessus complex have been reported.

METHODS

We searched the Mycobacteriology Database of the National Taiwan University Hospital and identified patients with CNS infections due to NTM.

RESULTS

A total of 15 patients, namely 4 HIV-seropositive patients and 11 HIV-seronegative patients, with CNS infections caused by NTM were identified during 2000-10. All of the HIV-seropositive patients had disseminated Mycobacterium avium complex infections. Among the 11 HIV-seronegative patients, NTM CNS infections were due to M. abscessus complex in 8 patients, M. avium complex in 2 patients and Mycobacterium kansasii in 1 patient. All the six preserved M. abscessus complex isolates were confirmed to be Mycobacterium massiliense by erm(41) PCR and 23S rRNA gene sequence analysis. Among the eight patients with infections due to M. abscessus complex, three had otolaryngological diseases, four had received neurosurgery and one had disseminated disease. Five patients received surgical debridement or intracranial device removal and three patients died of M. abscessus complex CNS infection. Among the five patients who survived, all received clarithromycin-based combination therapy with a median duration of 12 months and four received surgical intervention. All six isolates available for drug susceptibility testing showed uniform susceptibility to clarithromycin and five were susceptible to amikacin.

CONCLUSIONS

Our study revealed that M. abscessus complex isolates, particularly M. massiliense, should be considered potential pathogens causing CNS infections. Long-duration clarithromycin-based combination therapy plus surgical intervention may provide the best chance of cure.

Outcomes in patients with Mycobacterium abscessus pulmonary disease treated with long-term injectable drugs

BACKGROUND

The ATS (American Thoracic Society) has recommended periodic administration of multidrug therapy, including a macrolide and one or more parenteral agents or a combination of parenteral agents, over 2-4 months, for treatment of Mycobacterium abscessus pulmonary disease. However, there is little hard evidence supporting these guidelines, and treatment outcomes have not yet been reported.

METHODS

We retrospectively evaluated 41 patients with M. abscessus pulmonary disease treated in accordance with ATS guidelines. These patients were treated empirically with multidrug regimens, including a macrolide and one (amikacin) or more (amikacin and cefoxitin or imipenem) parenteral agents, over several months. Treatment outcomes were defined as treatment success, failure, or default.

RESULTS

Seventeen (41.5%) patients were prescribed a macrolide and one parenteral agent, and 24 (58.5%) were prescribed a macrolide and two parenteral agents. The median duration of parenteral and total antibiotic treatment were 230 days (range, 60-601 days) and 511 days (range, 164-1249 days), respectively. The treatment success, failure, and default rates were 80.5% (33/41), 12.2% (5/41), and 7.3% (3/41), respectively. Four patients relapsed over 445 days (range, 0-1443 days) of follow-up. There were no significant differences in treatment success and relapse rates between the groups receiving one and two parenteral agents. Adverse reactions developed in 18 of 41 patients (43.9%).

CONCLUSIONS

Combination antibiotic therapy, including long-term (minimum 2-4 months) parenteral drugs, as recommended by the ATS, resulted in successful treatment outcomes in 80.5% of patients with M. abscessus lung disease in Korea.

In Vitro Antimicrobial Susceptibility of Mycobacterium massiliense Recovered from Wound Samples of Patients Submitted to Arthroscopic and Laparoscopic Surgeries

Testing of rapidly growing species of mycobacteria (RGM) against antibacterial agents has been shown to have some clinical utility. This work establishes the MICs of seven antimicrobial agents following the guidelines set forth by the Clinical and Laboratory Standards Institute (CLSI) against eighteen isolates of Mycobacterium massiliense recovered from wound samples of patients submitted to minimally invasive surgery such as arthroscopy and laparoscopy. The isolates showed susceptibility to amikacin (MIC₉₀ = 4 μg/mL) and clarithromycin (MIC₉₀ < 1 μg/mL) but resistance to ciprofloxacin (MIC₉₀ > 16 μg/mL), doxycycline (MIC₉₀ > 32 μg/mL), sulfamethoxazole (MIC₉₀ > 128 μg/mL), and tobramycin (MIC₉₀ = 32 μg/mL), and intermediate profile to cefoxitin (MIC₉₀ = 64 μg/mL). Therefore, we suggest that the antimicrobial susceptibilities of any clinically significant RGM isolate should be performed.

Efficient differentiation of Mycobacterium abscessus complex isolates to the species level by a novel PCR-based variable-number tandem-repeat assay

A novel duplex PCR method based on variable-number tandem-repeat targets to discriminate among Mycobacterium abscessus complex isolates was developed and evaluated in 85 clinical isolates. The assay accuracy was confirmed by a multiple-target sequence analysis. The duplex PCR assay is a one-step, reliable, and accurate assay for discriminating M. abscessus species.