Clinical relevance of Mycobacterium chelonae-abscessus group isolation in 95 patients

Blocking ADP-ribosylation expands the anti-mycobacterial spectrum of rifamycins

The clinical utility of rifamycins against non-tuberculous mycobacterial (NTM) disease is limited by intrinsic drug resistance achieved by ADP-ribosyltransferase Arr. By blocking the site of ribosylation, we recently optimized a series of analogs with substantially improved potency against Mycobacterium abscessus. Here, we show that a representative member of this series is significantly more potent than rifabutin against major NTM pathogens expressing Arr, providing a powerful medicinal chemistry approach to expand the antimycobacterial spectrum of rifamycins. IMPORTANCE Lung disease caused by a range of different species of non-tuberculous mycobacteria (NTM) is difficult to cure. The rifamycins are very active against Mycobacterium tuberculosis, which causes tuberculosis (TB), but inactive against many NTM species. Previously, we showed that the natural resistance of the NTM Mycobacterium abscessus to rifamycins is due to enzymatic inactivation of the drug by the bacterium. We generated chemically modified versions of rifamycins that prevent inactivation by the bacterium and thus become highly active against M. abscessus. Here, we show that such a chemically modified rifamycin is also highly active against several additional NTM species that harbor the rifamycin inactivating enzyme found in M. abscessus, including M. chelonae, M. fortuitum, and M. simiae. This finding expands the potential therapeutic utility of our novel rifamycins to include several currently difficult-to-cure NTM lung disease pathogens beyond M. abscessus.

The small non-coding RNA B11 regulates multiple facets of Mycobacterium abscessus virulence

Mycobacterium abscessus causes severe disease in patients with cystic fibrosis. Little is known in M. abscessus about the roles of small regulatory RNAs (sRNA) in gene regulation. We show that the sRNA B11 controls gene expression and virulence-associated phenotypes in this pathogen. B11 deletion from the smooth strain ATCC_19977 produced a rough strain, increased pro-inflammatory signaling and virulence in multiple infection models, and increased resistance to antibiotics. Examination of clinical isolate cohorts identified isolates with B11 mutations or reduced expression. We used RNAseq and proteomics to investigate the effects of B11 on gene expression and test the impact of mutations found in clinical isolates. Over 200 genes were differentially expressed in the deletion mutant. Strains with the clinical B11 mutations showed expression trends similar to the deletion mutant, suggesting partial loss of function. Among genes upregulated in the B11 mutant, there was a strong enrichment for genes with B11-complementary sequences in their predicted ribosome binding sites (RBS), consistent with B11 functioning as a negative regulator that represses translation via base-pairing to RBSs. Comparing the proteomes similarly revealed that upregulated proteins were strongly enriched for B11-complementary sequences. Intriguingly, genes upregulated in the absence of B11 included components of the ESX-4 secretion system, critical for M. abscessus virulence. Many of these genes had B11-complementary sequences at their RBSs, which we show is sufficient to mediate repression by B11 through direct binding. Altogether, our data show that B11 acts as a direct negative regulator and mediates (likely indirect) positive regulation with pleiotropic effects on gene expression and clinically important phenotypes in M. abscessus. The presence of hypomorphic B11 mutations in clinical strains is consistent with the idea that lower B11 activity may be advantageous for M. abscessus in some clinical contexts. This is the first report on an sRNA role in M. abscessus.

Subspecies Distribution and Antimicrobial Susceptibility Testing of Mycobacterium abscessus Clinical Isolates in Madrid, Spain: a Retrospective Multicenter Study

Mycobacterium abscessus (MABS) is the most pathogenic and drug-resistant rapidly growing mycobacteria. However, studies on MABS epidemiology, especially those focusing on subspecies level, are scarce. We aimed to determine MABS subspecies distribution and its correlation with phenotypic and genotypic antibiotic profiles. A retrospective multicenter study of 96 clinical MABS isolates in Madrid between 2016 to 2021 was conducted. Identification at the subspecies level and resistance to macrolides and aminoglycosides were performed by the GenoType NTM-DR assay. The MICs of 11 antimicrobials tested against MABS isolates were determined using the broth microdilution method (RAPMYCOI Sensititer titration plates). Clinical isolates included 50 (52.1%) MABS subsp. abscessus; 33 (34.4%) MABS subsp. massiliense; and 13 (13.5%) MABS subsp. bolletii. The lowest resistance rates corresponded to amikacin (2.1%), linezolid (6.3%), cefoxitin (7.3%), and imipenem (14.6%), and the highest to doxycycline (100.0%), ciprofloxacin (89.6%), moxifloxacin (82.3%), cotrimoxazole (82.3%), tobramycin (81.3%), and clarithromycin (50.0% at day 14 of incubation). Regarding tigecycline, although there are no susceptibility breakpoints, all strains but one showed MICs ≤ 1 μg/mL. Four isolates harbored mutations at positions 2058/9 of the rrl gene, one strain harbored a mutation at position 1408 of the rrl gene, and 18/50 harbored the T28C substitution at erm(41) gene. Agreement of the GenoType results with clarithromycin and amikacin susceptibility testing was 99.0% (95/96). The rate of MABS isolates showed an upward trend during the study period, being M. abscessus subsp. abscessus the most frequently isolated subspecies. Amikacin, cefoxitin, linezolid, and imipenem showed great in vitro activity. The GenoType NTM-DR assay provides a reliable and complementary tool to broth microdilution for drug resistance detection. IMPORTANCE Infections caused by Mycobacterium abscessus (MABS) are increasingly being reported worldwide. Identifying MABS subspecies and assessing their phenotypic resistance profiles are crucial for optimal management and better patient outcomes. M. abscessus subspecies differ in erm(41) gene functionality, which is a critical determinant of macrolide resistance. Additionally, resistance profiles of MABS and the subspecies distribution can vary geographically, highlighting the importance of understanding local epidemiology and resistance patterns. This study provides valuable insights into the epidemiology and resistance patterns of MABS and its subspecies in Madrid. Elevated resistance rates were observed for several recommended antimicrobials, emphasizing the need for cautious drug use. Furthermore, we assessed the GenoType NTM-DR assay, which examines principal mutations in macrolides and aminoglycosides resistance-related genes. We observed a high level of agreement between the GenoType NTM-DR assay and the microdilution method, indicating its usefulness as an initial tool for early initiation of appropriate therapy.

Atypical Mycobacteriosis Due to Mycobacterium abscessus subsp. massiliense: Our Experince

BACKGROUND

Members of Micobacterium. abscessus complex comprises three subspecies (M. abscessus subsp. Abscessus, M. abscessus subsp. Bolletii, and M. abscessus subsp. Massiliense) and are a rapid-growing nontuberculous mycobacteria present in different aquatic habitats and soil. It often causes a wide spectrum of infections involving pulmonary infections, surgical wound infections, and infections related to mesotherapy, catheters, hemodialysis devices, endocarditis, and disseminated infections in immunocompromised individuals.

METHODS

In this article we comment on the most relevant aspects of nine patients with skin lesions caused by M. abscessus subsp. massiliense infection. Clinical characteristics, histopathology, and molecular identification were performed.

RESULTS

The patients in the clinical cases presented a history of trauma, tattoos, and physical therapy techniques. The most common treatments were minocycline and clindamycin, doxycycline, ceftriaxone, cephalexin, moxifloxacin, rifampicin, and trimethoprim-sulfamethoxazole. The evolution of the treated patients was acceptable, except for one patient, who showed a partial improvement. M. massiliense were identified in all clinical cases using a species-specific PCR.

CONCLUSION

Our series consisted of nine cases of skin biopsies recorded in different years; for this reason, we do not have all the data necessary for a complete description, in particular in four cases, causing limitations in the manuscript, especially in the therapy used and the evolution of patients due to lack of follow-up.

Lungenerkrankung durch seltenere nicht-tuberkulöse Mykobakterien – Neue internationale Empfehlungen

Therapie von NTM-Infektionen Für die Behandlung von NTM-Infektionen der Lungen stehen erstmals Evidenz-basierte internationale Leitlinien zur Verfügung. Nach der ersten Publikation der neuen ATS/ERS/ESCMID- und IDSA-Leitlinien zur Behandlung von Lungenerkrankungen durch M. avium complex, M. kansasii, M. xenopi und M. abscessus von 2020 liegen nun weitere Empfehlungen zur Behandlung von selteneren Lungenerkrankungen durch NTM vor.

Relevante NTM-Spezies Die neuen Empfehlungen umfassen Lungenerkrankungen durch die schnellwachsenden Mykobakterien M. chelonae und M. fortuitum sowie durch die langsam-wachsenden Mykobakterien M. genavense, M. gordonae, M. malmoense, M. simiae und M. szulgai.

Development of a nucleic acid chromatography assay for the detection of commonly isolated rapidly growing mycobacteria

Introduction. Non-tuberculosis mycobacterium infections are increasing worldwide, including those caused by rapidly growing mycobacteria (RGM).Gap Statement. The identification of the aetiological agent in the context of infections is essential for the adoption of an adequate therapeutic approach. However, the methods for the rapid distinction of different RGM species are less than optimal.Aim. To develop a nucleic acid chromatography kit to identify clinically common RGM.Methodology. We tried to develop a nucleic acid chromatography kit designed to detect four RGM species (including three subspecies) i.e. Mycobacterium abscessus subsp. abscessus, Mycobacterium abscessus subsp. bolletii (detected as M. abscessus/bolletii) Mycobacterium abscessus subsp. massiliense, Mycobacterium fortuitum, Mycobacterium chelonae and Mycobacterium peregrinum. The amplified target genes for each species/subspecies using multiplex PCR were analysed using a nucleic acid chromatography assay.Results. Among the 159 mycobacterial type strains and 70 RGM clinical isolates tested, the developed assay correctly identified all relevant RGM without any cross-reactivity or false-negatives. The limits of detection for each species were approximately 0.2 pg µl^-1.Conclusion. The rapid and simple nucleic acid chromatography method developed here, which does not involve heat denaturation, may contribute to the rapid identification and treatment of RGM infections.

Increased whiB7 expression and antibiotic resistance in Mycobacterium chelonae carrying two prophages

BACKGROUND

The global rise in the incidence of non-tuberculosis mycobacterial infections is of increasing concern due their high levels of intrinsic antibiotic resistance. Although integrated viral genomes, called prophage, are linked to increased antibiotic resistance in some bacterial species, we know little of their role in mycobacterial drug resistance.

RESULTS

We present here for the first time, evidence of increased antibiotic resistance and expression of intrinsic antibiotic resistance genes in a strain of Mycobacterium chelonae carrying prophage. Strains carrying the prophage McProf demonstrated increased resistance to amikacin. Resistance in these strains was further enhanced by exposure to sub-inhibitory concentrations of the antibiotic, acivicin, or by the presence of a second prophage, BPs. Increased expression of the virulence gene, whiB7, was observed in strains carrying both prophages, BPs and McProf, relative to strains carrying a single prophage or no prophages.

CONCLUSIONS

This study provides evidence that prophage alter expression of important mycobacterial intrinsic antibiotic resistance genes and additionally offers insight into the role prophage may play in mycobacterial adaptation to stress.

Mycobacterium abscessus complex: A Review of Recent Developments in an Emerging Pathogen

Mycobacterium abscessus complex (MABC) is one of the most clinically relevant species among nontuberculous mycobacteria. MABC's prevalence has increased over the last two decades. Although these changes can be explained by improvements in microbiological and molecular techniques for identifying species and subspecies, a higher prevalence of chronic lung diseases may contribute to higher rates of MABC. High rates of antimicrobial resistance are seen in MABC, and patients experience multiple relapses with low cure rates. This review aims to integrate existing knowledge about MABC epidemiology, microbiological identification and familiarize readers with molecular mechanisms of resistance and therapeutic options for pulmonary infections with MABC.

Arthroscopic treatment of Mycobacterium massiliense septic arthritis outbreak after intra-articular injection: A case-series report and literature review

Non-tuberculous mycobacteria (NTM) comprise mycobacteria, with the exceptions of Mycobacterium (M.) leprae and the M. tuberculosis complex. Septic arthritis caused by NTM is so rare that there is no standardized treatment.Between April and September 2012, 27 patients were infected with M. massiliense in a single clinic following injection of steroid in the knee joint. Clinical data of 9 patients who received arthroscopic treatment in Seoul Hospital of Soonchunhyang University were analyzed retrospectively.Arthroscopic irrigation and debridement were performed average 2.6 times (1-3 times). As 6 out of 9 cases (67%) had joint contracture of the knee joint, arthroscopic adhesiolysis, and brisement were performed. After surgical procedures, Hospital for Special Surgery and Lysholm knee score showed improvement compared before the surgery, but a radiographic result evaluated by Kellgren-Lawrence revealed that 6 cases got deteriorated to stage 4 in the 4-year follow-up.NTM septic arthritis had a higher recurrence and a higher contracture incidence than septic arthritis caused by tuberculous mycobacteria or other bacteria. Treatment was possible with repeated arthroscopic debridement and intravenous antibiotics.

Immune defects in patients with pulmonary Mycobacterium abscessus disease without cystic fibrosis

The prevalence of Mycobacterium abscessus infections in non-cystic fibrosis (CF) patients has increased in recent years. In this study, we investigate whether immune defects explain the apparent susceptibility to this opportunistic infection in non-CF patients.

We performed stimulations of peripheral blood mononuclear cells and whole blood from 13 patients with M. abscessus pulmonary disease and 13 healthy controls to investigate their cytokine production after 24 h and 7 days.

Patients were predominantly women (54%) with a mean age of 59 years; 62% had nodular bronchiectatic disease. Many patients had predisposing pulmonary diseases, such as COPD (46%), and asthma (23%). Patients with COPD showed an impaired interleukin (IL)-6 response to M. abscessus and a reduced IL-17 response to Candida, together with a M. abscessus-specific enhanced IL-22 production. Patients without COPD showed higher levels of interleukin-1 receptor antagonist (IL-1Ra), an anti-inflammatory molecule. Within the non-COPD patients, those with bronchiectasis showed defective interferon (IFN)-γ production in response to Candida albicans.

In conclusion, susceptibility to M. abscessus is likely determined by a combination of immunological defects and predisposing pulmonary disease. The main defect in the innate immune response was a shift of the ratio of IL-1β to IL-1Ra, which decreased the bioactivity of this pathway in the adaptive immune response. In the adaptive immune response there was defective IL-17 and IFN-γ production. Patients with COPD and bronchiectasis showed different cytokine defects. It is therefore crucial to interpret the immunological results within the clinical background of the patients tested.

Measurement of defects in both the innate and adaptive immune responses in patients with M. abscessus pulmonary disease show that susceptibility to M. abscessus is determined by a combination of immunological defects and predisposing pulmonary diseasehttps://bit.ly/2DtbycY

Epidemiology, diagnosis & treatment of non-tuberculous mycobacterial diseases

Non-tuberculous mycobacteria (NTM) are ubiquitously present in the environment, but NTM diseases occur infrequently. NTM are generally considered to be less virulent than Mycobacterium tuberculosis, however, these organisms can cause diseases in both immunocompromised and immunocompetent hosts. As compared to tuberculosis, person-to-person transmission does not occur except with M. abscessus NTM species among cystic fibrosis patients. Lung is the most commonly involved organ, and the NTM-pulmonary disease (NTM-PD) occurs frequently in patients with pre-existing lung disease. NTM may also present as localized disease involving extrapulmonary sites such as lymph nodes, skin and soft tissues and rarely bones. Disseminated NTM disease is rare and occurs in individuals with congenital or acquired immune defects such as HIV/AIDS. Rapid molecular tests are now available for confirmation of NTM diagnosis at species and subspecies level. Drug susceptibility testing (DST) is not routinely done except in non-responsive disease due to slowly growing mycobacteria ( M. avium complex, M. kansasii) or infection due to rapidly growing mycobacteria, especially M. abscessus. While the decision to treat the patients with NTM-PD is made carefully, the treatment is given for 12 months after sputum culture conversion. Additional measures include pulmonary rehabilitation and correction of malnutrition. Treatment response in NTM-PD is variable and depends on isolated NTM species and severity of the underlying PD. Surgery is reserved for patients with localized disease with good pulmonary functions. Future research should focus on the development and validation of non-culture-based rapid diagnostic tests for early diagnosis and discovery of newer drugs with greater efficacy and lesser toxicity than the available ones.

Treatment of Nontuberculous Mycobacterial Pulmonary Disease: An Official ATS/ERS/ESCMID/IDSA Clinical Practice Guideline

Nontuberculous mycobacteria (NTM) represent over 190 species and subspecies, some of which can produce disease in humans of all ages and can affect both pulmonary and extrapulmonary sites. This guideline focuses on pulmonary disease in adults (without cystic fibrosis or human immunodeficiency virus infection) caused by the most common NTM pathogens such as Mycobacterium avium complex, Mycobacterium kansasii, and Mycobacterium xenopi among the slowly growing NTM and Mycobacterium abscessus among the rapidly growing NTM. A panel of experts was carefully selected by leading international respiratory medicine and infectious diseases societies (ATS, ERS, ESCMID, IDSA) and included specialists in pulmonary medicine, infectious diseases and clinical microbiology, laboratory medicine, and patient advocacy. Systematic reviews were conducted around each of 22 PICO (Population, Intervention, Comparator, Outcome) questions and the recommendations were formulated, written, and graded using the GRADE (Grading of Recommendations Assessment, Development, and Evaluation) approach. Thirty-one evidence-based recommendations about treatment of NTM pulmonary disease are provided. This guideline is intended for use by healthcare professionals who care for patients with NTM pulmonary disease, including specialists in infectious diseases and pulmonary diseases.

Treatment of nontuberculous mycobacterial pulmonary disease: an official ATS/ERS/ESCMID/IDSA clinical practice guideline

Nontuberculous mycobacteria (NTM) represent over 190 species and subspecies, some of which can produce disease in humans of all ages and can affect both pulmonary and extrapulmonary sites. This guideline focuses on pulmonary disease in adults (without cystic fibrosis or human immunodeficiency virus infection) caused by the most common NTM pathogens such as Mycobacterium avium complex, Mycobacterium kansasii, and Mycobacterium xenopi among the slowly growing NTM and Mycobacterium abscessus among the rapidly growing NTM. A panel of experts was carefully selected by leading international respiratory medicine and infectious diseases societies (ATS, ERS, ESCMID, IDSA) and included specialists in pulmonary medicine, infectious diseases and clinical microbiology, laboratory medicine, and patient advocacy. Systematic reviews were conducted around each of 22 PICO (Population, Intervention, Comparator, Outcome) questions and the recommendations were formulated, written, and graded using the GRADE (Grading of Recommendations Assessment, Development, and Evaluation) approach. Thirty-one evidence-based recommendations about treatment of NTM pulmonary disease are provided. This guideline is intended for use by healthcare professionals who care for patients with NTM pulmonary disease, including specialists in infectious diseases and pulmonary diseases.

M ycobacterium abscessus pulmonary disease: individual patient data meta-analysis

Treatment of Mycobacterium abscessus pulmonary disease (MAB-PD), caused by M. abscessus subsp. abscessus, M. abscessus subsp. massiliense or M. abscessus subsp. bolletii, is challenging.We conducted an individual patient data meta-analysis based on studies reporting treatment outcomes for MAB-PD to clarify treatment outcomes for MAB-PD and the impact of each drug on treatment outcomes. Treatment success was defined as culture conversion for ≥12 months while on treatment or sustained culture conversion without relapse until the end of treatment.Among 14 eligible studies, datasets from eight studies were provided and a total of 303 patients with MAB-PD were included in the analysis. The treatment success rate across all patients with MAB-PD was 45.6%. The specific treatment success rates were 33.0% for M. abscessus subsp. abscessus and 56.7% for M. abscessus subsp. massiliense For MAB-PD overall, the use of imipenem was associated with treatment success (adjusted odds ratio (aOR) 2.65, 95% CI 1.36-5.10). For patients with M. abscessus subsp. abscessus, the use of azithromycin (aOR 3.29, 95% CI 1.26-8.62), parenteral amikacin (aOR 1.44, 95% CI 1.05-1.99) or imipenem (aOR 7.96, 95% CI 1.52-41.6) was related to treatment success. For patients with M. abscessus subsp. massiliense, the choice among these drugs was not associated with treatment outcomes.Treatment outcomes for MAB-PD are unsatisfactory. The use of azithromycin, amikacin or imipenem was associated with better outcomes for patients with M. abscessus subsp. abscessus.

Variation among human, veterinary and environmental Mycobacterium chelonae-abscessus complex isolates observed using core genome phylogenomic analysis, targeted gene comparison, and anti-microbial susceptibility patterns

Mycobacterium chelonae is a member of the Mycobacterium chelonae-abscessus complex and a cause of opportunistic disease in fish, reptiles, birds, and mammals including humans. Isolates in the complex are often difficult to identify and have differing antimicrobial susceptibilities. Thirty-one previously identified rapidly-growing, non-tuberculous Mycobacterium sp. isolates cultured from biofilms, fish, reptiles, mammals, including humans, and three ATCC reference strains were evaluated with nine M. chelonae-abscessus complex whole genome sequences from GenBank by phylogenomic analysis, targeted gene comparisons, and in-vitro antimicrobial susceptibility patterns to assess strain variation among isolates from different sources. Results revealed minimal genetic variation among the M. chelonae strains. However, the core genomic alignment and SNP pattern of the complete 16S rRNA sequence clearly separated the turtle type strain ATCC 35752^T from the clinical isolates and human reference strain “M. chelonae chemovar niacinogenes” ATCC 19237, providing evidence of two distinct subspecies. Concatenation of the partial rpoB (752 bp) and complete hsp65 (1,626 bp) sequence produced the same species/subspecies delineations as the core phylogeny. Partial rpoB and hsp65 sequences identified all the clinical isolates to the appropriate species level when respective cut-offs of 98% and 98.4% identity to the M. chelonae type strain ATCC 35752^T were employed. The human strain, ATCC19237, was the most representative strain for the evaluated human, veterinary, and environmental strains. Additionally, two isolates were identified as Mycobacterium saopaulense, its first identification in a non-fish or non-human host.

Paradigm for diagnosing mycobacterial disease: direct detection and differentiation of Mycobacterium tuberculosis complex and non-tuberculous mycobacteria in clinical specimens using multiplex real-time PCR

AIMS

Mycobacterium tuberculosis and non-tuberculous mycobacteria (NTM) are clinically different, and the rapid detection and differentiation of M. tuberculosis complex (MTBC) and NTM is crucial for patient management and infection control. Given the slow growth of most pathogenic mycobacteria, nucleic acid amplification assays are excellent tools for direct identification of mycobacteria in clinical specimens. Recently, a multiplex real-time PCR assay was developed that can directly detect 20 mycobacterial species in clinical specimens. Here, we evaluated the diagnostic performance of the assay for diagnosing mycobacterial disease under routine laboratory conditions.

METHODS

A total of 3334 specimens collected from 1437 patients suspected of tuberculosis infection were subjected to acid-fast bacilli staining, conventional culture and the multiplex real-time PCR assay. To evaluate the sensitivity and specificity of the assay, the overall diagnosis of tuberculosis was defined by positive culture plus medical history, and the 2007 American Thoracic Society and Infectious Disease Society of America diagnostic criteria for NTM disease were applied.

RESULTS

The sensitivity, specificity, positive predictive value and negative predictive value were 87.5%, 99.6%, 96.1% and 98.5%, respectively, for the detection of MTBC isolates and 53.3%, 99.9%, 95.2%, and 98.9%, respectively, for detecting NTM isolates.

CONCLUSIONS

Thus, the assay can correctly differentiate between MTBC and NTM isolates in clinical specimens and would be a useful tool for the rapid differentiation of tuberculosis and NTM disease, despite its limited sensitivity for the diagnosis of NTM disease.

Systematic Review and Meta-analyses of the Effect of Chemotherapy on Pulmonary Mycobacterium abscessus Outcomes and Disease Recurrence

In pharmacokinetic/pharmacodynamic models of pulmonary Mycobacterium abscessus complex, the recommended macrolide-containing combination therapy has poor kill rates. However, clinical outcomes are unknown. We searched the literature for studies published between 1990 and 2017 that reported microbial outcomes in patients treated for pulmonary M. abscessus disease. A good outcome was defined as sustained sputum culture conversion (SSCC) without relapse. Random effects models were used to pool studies and estimate proportions of patients with good outcomes. Odds ratios (OR) and 95% confidence intervals (CI) were computed. Sensitivity analyses and metaregression were used to assess the robustness of findings. In 19 studies of 1,533 patients, combination therapy was administered to 508 patients with M. abscessus subsp. abscessus, 204 with M. abscessus subsp. massiliense, and 301 with M. abscessus with no subspecies specified. Macrolide-containing regimens achieved SSCC in only 77/233 (34%) new M. abscessus subsp. abscessus patients versus 117/141 (54%) M. abscessus subsp. massiliense patients (OR, 0.108 [95% CI, 0.066 to 0.181]). In refractory disease, SSCC was achieved in 20% (95% CI, 7 to 36%) of patients, which was not significantly different across subspecies. The estimated recurrent rates per month were 1.835% (range, 1.667 to 3.196%) for M. abscessus subsp. abscessus versus 0.683% (range, 0.229 to 1.136%) for M. abscessus subsp. massiliense (OR, 6.189 [95% CI, 2.896 to 13.650]). The proportion of patients with good outcomes was 52/223 (23%) with M. abscessus subsp. abscessus versus 118/141 (84%) with M. abscessus subsp. massiliense disease (OR, 0.059 [95% CI, 0.034 to 0.101]). M. abscessus subsp. abscessus pulmonary disease outcomes with the currently recommended regimens are atrocious, with outcomes similar to those for extensively drug-resistant tuberculosis. Therapeutically, the concept of nontuberculous mycobacteria is misguided. There is an urgent need to craft entirely new treatment regimens.

Reinstating Mycobacterium massiliense and Mycobacterium bolletii as species of the Mycobacterium abscessus complex

TheMycobacterium abscessus complex is a group of rapidly growing, multiresistant mycobacteria previously divided into three species. Proposal for the union of Mycobacterium bolletii and Mycobacterium massiliense into one subspecies, so-called M. abscessus subsp. massiliense, created much confusion about the routine identification and reporting of M. abscessus clinical isolates for clinicians. Results derived from multigene sequencing unambiguously supported the reinstatement of M. massiliense and M. bolletii as species, culminating in the presence of erm(41)-encoded macrolide resistance in M. bolletii. Present genome-based analysis unambiguously supports the reinstatement of M. massiliense and M. bolletii as species after the average nucleotide identity values of 96.7 % for M. abscessus versus M. bolletii, and 96.4 % for M. abscessus versus M. massiliense, and the 96.6 % identity between M. bolletii and M. massiliense was put into the perspective of a larger, 28-species analysis. Accordingly, DNA-DNA hybridization values predicted by the complete rpoB gene sequencing analysis were between 68.7 and 72.3 % in this complex. These genomic data as well as the phenotypic characteristics prompted us to propose to reinstate the previously known M. massiliense and M. bolletii into two distinct species among the M. abscessus complex.

Mycobacterium abscessus Complex - a Particular Challenge in the Setting of Lung Transplantation

Mycobacterium abscessus complex is an emerging pathogen in lung transplant candidates and recipients. M. abscessus complex is widespread in the environment and can cause pulmonary, skin and soft tissue, and disseminated infection, particularly in lung transplant recipients. It is innately resistant to many antibiotics making it difficult to treat. Herein we describe the epidemiology, clinical manifestations, diagnosis and treatment of M. abscessus with an emphasis on lung transplant candidates and recipients. We also outline the areas where data are lacking and the areas where further research is urgently needed.

Molecular epidemiology of Mycobacterium abscessus complex isolates in Ireland

BACKGROUND

The Mycobacterium abscessus complex are the rapidly growing mycobacteria (RGM) most commonly causing lung disease, especially in cystic fibrosis (CF) patients. Ireland has the world's highest CF incidence. The molecular epidemiology of M. abscessus complex in Ireland is unreported.

METHODS

We performed rpoB gene sequencing and multi-locus sequence typing (MLST) on M. abscessus complex strains isolated from thirty-six patients in 2006-2012 (eighteen known CF patients).

RESULTS

Twenty-eight strains (78%) were M. abscessus subsp. abscessus, eight M. abscessus subsp. massiliense, none were M. abscessus subsp. bolletii. Sequence type 1 (ST1) and ST26 (M. abscessus subsp. abscessus) were commonest. Seven M. abscessus subsp. abscessus STs (25%) were novel (two with novel alleles). Seven M. abscessus subsp. massiliense STs were previously reported (88%), including two ST23, the globally successful clone. In 2012, of 552 CF patients screened, eleven were infected with M. abscessus complex strains (2%).

CONCLUSIONS

The most prevalent M. abscessus subsp. abscessus and M. abscessus subsp. massiliense strains in Ireland belong to widely-distributed STs, but there is evidence of high M. abscessus subsp. abscessus diversity.

Species Identification and Clarithromycin Susceptibility Testing of 278 Clinical Nontuberculosis Mycobacteria Isolates

Purpose of this paper is to analyze different species' proportion of nontuberculosis mycobacteria (NTM) and susceptibility to clarithromycin of different species. 278 clinical NTM isolates were identified into species by using 16S rRNA, rpoB and hsp65. Then clarithromycin susceptibility testing against different species was done separately, using microplate Alamar Blue assay. Finally, resistance isolates' erm(41) of M. abscessus were sequenced in order to analyze mechanisms for clarithromycin resistant. In this test, 131 isolates (47%) belonged to M. avium complex (MAC), and 70 isolates (25%) belonged to M. abscessus. Nearly all the M. abscessus subsp. abscessus resistant to clarithromycin had T28 in erm(41). However, all the M. abscessus subsp. abscessus susceptible to clarithromycin had C28 in erm(41). In this study, we find that MAC was the most common pathogens of NTM, and the second one was M. abscessus. However, M. chelonei, M. fuerth, and M. gordon were rare. Clarithromycin had a good inhibition activity against all the NTM species except M. abscessus subsp. abscessus. The erm(41) genotype is of high relevance to clarithromycin resistance.

Disseminated Mycobacterium abscessus Infection Following Septic Arthritis: A Case Report and Review of the Literature

Mycobacterium abscessus is a rapidly growing mycobacterium found mainly in patients with respiratory or cutaneous infections, but it rarely causes disseminated infections. Little is known about the clinical characteristics, treatment, and prognosis of disseminated M abscessus infection. A 75-year-old Japanese woman who had been treated for 17 years with a corticosteroid for antisynthetase syndrome with antithreonyl-tRNA synthetase antibody developed swelling of her right elbow. X-ray of her right elbow joint showed osteolysis, and magnetic resonance imaging revealed fluid in her right elbow joint. M abscessus grew in joint fluid and blood cultures. She was diagnosed with a disseminated M abscessus infection following septic arthritis. Antimicrobial treatment by clarithromycin, amikacin, and imipenem/cilastatin combined with surgical debridement was administered. Although blood and joint fluid cultures became negative 1 week later, the patient died at 6 weeks from starting antimicrobial treatment. We reviewed 34 cases of disseminated M abscessus infections from the literature. Most of the patients had immunosuppressive backgrounds such as transplantation, use of immunosuppressive agents, hematological malignancy, and end stage renal disease. The duration from onset of symptoms to diagnosis was over 3 months in half of the cases. All fatal cases had positive blood cultures or use of immunosuppressive agents. Clinicians should bear in mind that mycobacterial infections including M abscessus are one of the differential diagnoses in patients with subacute arthritis and soft tissue infections.

Investigation of the population structure of Mycobacterium abscessus complex strains using 17-locus variable number tandem repeat typing and the further distinction of Mycobacterium massiliense hsp65 genotypes

Mycobacterium abscessus complex is a significant pathogen in patients with non-cystic fibrosis (non-CF). Nevertheless, there is little description of the genetic diversity of this species. The aims of this study were to investigate the distribution of M. abscessus complex isolated from respiratory specimens by variable number tandem repeat (VNTR) typing. The results of 104 clinical isolates from 104 non-CF patients were compared using PFGE, hsp65 genotypes and clarithromycin susceptibility. The allelic diversity (Hunter-Gaston Discriminatory Index) of the 17 loci examined by VNTR typing was high (0.977). We determined that C28 sequevar erm(41) genotypes and clarithromycin-acquired resistance isolates were scattered in the minimum spanning tree. Intriguingly, VNTR typing and PFGE were highly congruent and revealed that there were clear examples of grouping of isolates from different individuals amongst both M. abscessus and M. massiliense, and showed five clusters of distinct identical isolates. Within these clusters, M. massiliense hsp65 type I formed three different clusters. Although the distribution of M. massiliense hsp65 type II-1 was low (9.3 %), M. massiliense hsp65 type II-1 isolates separated from clusters contained hsp65 type I isolates. Thus, M. massiliense hsp65 genotypes could be discriminated by analysing VNTRs with sufficient genetic distance for intra-species-level discrimination.

Recent progress towards understanding genetic variation in the Mycobacterium abscessus complex

Mycobacterium abscessus is an emerging cause of respiratory disease and soft tissue infections. Whole genome sequencing and other molecular approaches are enhancing our understanding of outbreaks, antibiotic resistance mechanisms, and virulence properties, and of the phylogeny of the M. abscessus complex. Infection models are providing further insights into factors such as colony phenotype that impact host-pathogen interactions. This paper reviews recent developments in our understanding of genetic variation in M. abscessus and the potential relevance for disease and treatment.

Epidemiology of human pulmonary infection with nontuberculous mycobacteria: a review

Population-based data have documented a worldwide increase in the prevalence of human nontuberculous mycobacterial (NTM) infections since 2000. Mycobacterium avium complex is predominant in North America and East Asia, whereas in regions within Europe, M kansasii, M xenopi, and M malmoense are more common. Host factors important to the current epidemiology of NTM pulmonary disease include thoracic skeletal abnormalities, rheumatoid arthritis, and use of immunomodulatory drugs. Clustering of disease within families suggests a heritable genetic predisposition to disease susceptibility. Warm, humid environments with high atmospheric vapor pressure contribute to population risk.

Risk factors for microbiologic failure among Taiwanese adults with Mycobacterium abscessus complex pulmonary disease

BACKGROUND

The Mycobacterium abscessus complex is a common cause of pulmonary nontuberculous mycobacteria infections in Taiwan. We examined the risk factors associated with treatment outcome in Taiwanese adults with pulmonary disease caused by the M. abscessus complex.

METHODS

We retrospectively reviewed the records of all patients from a southern Taiwan medical center from 2006 to 2012 who had respiratory specimens identified as M. abscessus complex and met the American Thoracic Society criteria for pulmonary disease.

RESULTS

Of the 106 included patients, females (58.5%) and nonsmokers (79.2%) predominated. The mean age of patients was 64.8 years. Sixty-three patients (59.4%) had pre-existing lung disease. Previous mycobacterial pulmonary disease (34.9%) was the most common underlying disorder. Chest radiography indicated that bronchiectasis was common (47.2%) and that cavitations were less common (14.2%). Fifty-six patients received antibiotic treatment. Clinicians were more likely to prescribe antibiotics if the initial sputum acid-fast staining was positive (p < 0.001). Treatment outcome was analyzed in 26 patients who were treated for more than 3 months; three of these patients (11.5%) had clinical failure and 18 (69.2%) experienced sputum conversion. Patients with cavitary lesions were more likely to experience microbiologic failure (p = 0.02). Nine patients had positive cultures after antibiotic treatment for > 1 year. Previous mycobacterial pulmonary disease (p = 0.011) and cavitary lesion (p = 0.034) are risk factors for persistence of M. abscessus complex.

CONCLUSION

With antimicrobial therapy, previous mycobacterial disease, and cavitary lesion are associated with microbiologic failure in Taiwanese adults with M. abscessus complex pulmonary disease.

The First Korean Case of Nontuberculous Mycobacterial Lung Disease Caused by Mycobacterium abscessus Subspecies bolletii in a Patient with Bronchiectasis

We report the first Korean case of lung diseases caused by Mycobacterium abscessus subsp. bolletii in a previously healthy male, except for a previous history of pulmonary tuberculosis and bronchiectasis. All serial isolates are identified as M. abscessus subsp. bolletii by multi-locus sequence analysis based on the hsp65, rpoB, and 16S rRNA fragments. At the genetic level, the isolate has the erm(41) gene with a T28 sequevar, associated with clarithromycin resistance, and no rrl mutation. The isolate is resistant to clarithromycin. Although the symptoms and radiographic findings have improved after combination of antibiotics, the follow-up sputum cultures are persistently positive.

The genome sequence of 'Mycobacterium massiliense' strain CIP 108297 suggests the independent taxonomic status of the Mycobacterium abscessus complex at the subspecies level

Members of the Mycobacterium abscessus complex are rapidly growing mycobacteria that are emerging as human pathogens. The M. abscessus complex was previously composed of three species, namely M. abscessus sensu stricto, 'M. massiliense', and 'M. bolletii'. In 2011, 'M. massiliense' and 'M. bolletii' were united and reclassified as a single subspecies within M. abscessus: M. abscessus subsp. bolletii. However, the placement of 'M. massiliense' within the boundary of M. abscessus subsp. bolletii remains highly controversial with regard to clinical aspects. In this study, we revisited the taxonomic status of members of the M. abscessus complex based on comparative analysis of the whole-genome sequences of 53 strains. The genome sequence of the previous type strain of 'Mycobacterium massiliense' (CIP 108297) was determined using next-generation sequencing. The genome tree based on average nucleotide identity (ANI) values supported the differentiation of 'M. bolletii' and 'M. massiliense' at the subspecies level. The genome tree also clearly illustrated that 'M. bolletii' and 'M. massiliense' form a distinct phylogenetic clade within the radiation of the M. abscessus complex. The genomic distances observed in this study suggest that the current M. abscessus subsp. bolletii taxon should be divided into two subspecies, M. abscessus subsp. massiliense subsp. nov. and M. abscessus subsp. bolletii, to correspondingly accommodate the previously known 'M. massiliense' and 'M. bolletii' strains.

Discrimination of Mycobacterium abscessus subsp. massiliense from Mycobacterium abscessus subsp. abscessus in clinical isolates by multiplex PCR

The rapidly growing mycobacterium M. abscessus sensu lato is the causative agent of emerging pulmonary and skin diseases and of infections following cosmetic surgery and postsurgical procedures. M. abscessus sensu lato can be divided into at least three subspecies: M. abscessus subsp. abscessus, M. abscessus subsp. massiliense, and M. abscessus subsp. bolletii. Clinical isolates of rapidly growing mycobacteria were previously identified as M. abscessus by DNA-DNA hybridization. More than 30% of these 117 clinical isolates were differentiated as M. abscessus subsp. massiliense using combinations of multilocus genotyping analyses. A much more cost-effective technique to distinguish M. abscessus subsp. massiliense from M. abscessus subsp. abscessus, a multiplex PCR assay, was developed using the whole-genome sequence of M. abscessus subsp. massiliense JCM15300 as a reference. Several primer sets were designed for single PCR to discriminate between the strains based on amplicons of different sizes. Two of these single-PCR target sites were chosen for development of the multiplex PCR assay. Multiplex PCR was successful in distinguishing clinical isolates of M. abscessus subsp. massiliense from samples previously identified as M. abscessus. This approach, which spans whole-genome sequencing and clinical diagnosis, will facilitate the acquisition of more-precise information about bacterial genomes, aid in the choice of more relevant therapies, and promote the advancement of novel discrimination and differential diagnostic assays.

Further isolation of Mycobacterium abscessus subsp. abscessus and subsp. bolletii in different regions of Japan and susceptibility of these isolates to antimicrobial agents

The aim of this study was to genetically analyse Mycobacterium abscessus subsp. abscessus (hereafter M. abscessus) and M. abscessus subsp. bolletii (hereafter M. bolletii) isolates from six different regions of Japan and to determine the antimicrobial susceptibility of these isolates. Subspeciation of 143 clinical isolates of M. abscessus group was done by comparative sequence analysis of the rpoB and hsp65 genes and the internal transcribed spacer (ITS) region. Genetic analysis led to the identification of 90 M. abscessus (62.9%) and 53 M. bolletii (37.1%; comprising 50 'M. massiliense' and 3 'M. bolletii' in the old nomenclature). No significant differences were found between the M. abscessus and M. bolletii isolates in any characteristics. Susceptibility to clarithromycin and linezolid for M. bolletii isolates was significantly higher than that for M. abscessus (P<0.05). Moreover, the results demonstrated that 82 M. abscessus isolates with T28 sequevar were resistant to clarithromycin owing to the expression of erm(41), which was induced by clarithromycin, whilst 8 isolates with C28 sequevar were susceptible. Acquired clarithromycin resistance in 'M. bolletii' isolates was significantly associated with previous Mycobacterium avium complex (MAC) treatment compared with that of M. abscessus isolates; however, intrinsic inducible susceptibility of M. abscessus isolates was not associated with MAC treatment. However, acquired resistance to clarithromycin by mutation in the rrl gene encoding 23S rRNA did not occur in 14 of 18 resistant isolates. Strains with acquired resistance to clarithromycin and mutation in rrl consisted of two M. bolletii (one 'M. massiliense' and one 'M. bolletii') and two M. abscessus T28 sequevar.

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.

Mycobacterial genotypes are associated with clinical manifestation and progression of lung disease caused by Mycobacterium abscessus and Mycobacterium massiliense

BACKGROUND

Mycobacterium abscessus and Mycobacterium massiliense, which cause lung disease, are variable in their clinical manifestation and progression. We hypothesized that mycobacterial genotypes represent their pathogenic phenotypes, which would result in particular genotypes being associated with disease progression.

METHODS

Variable number tandem repeat (VNTR) loci were selected to establish a genotype assay that was capable of differentiating patients with heterogeneous prognoses in the development cohort (48 isolates). The analysis was reevaluated in the validation cohort (63 isolates).

RESULTS

A total of 53 M. abscessus and 58 M. massiliense isolates were assembled into 3 clusters based on their VNTR genotyping. The patients in cluster A were more likely to have stable disease of the nodular bronchiectatic form; 100% of M. abscessus patients and 96% of M. massiliense patients were followed without antibiotic treatment for >24 months after diagnosis. In contrast, the patients in cluster B were more likely to have progressive disease of the nodular bronchiectatic form; 96% of M. abscessus patients and 81% of M. massiliense patients started antibiotic treatment within 24 months after diagnosis. All patients in cluster C had fibrocavitary disease and started antibiotic treatment immediately after diagnosis. The genetic distance of each clinical isolate from the reference strain was associated with the highest likelihood of disease progression and a disease phenotype of the fibrocavitary form (P < .001).

CONCLUSIONS

Mycobacterial genotyping of M. abscessus and M. massiliense may provide valuable information for predicting disease phenotype and progression.

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.

Multiple cases of cutaneous Mycobacterium massiliense infection in a "hot spa" in Japan

Seven body polishers working in the same "hot spa" presented with multiple red nodules and papules on their hands and forearms. A causative agent was successfully isolated from two of the subjects and from a swab sample collected from the underside of a bed cover in the body-polishing facility. The two cutaneous isolates and the environmental isolate were rapidly growing mycobacteria that formed nonphotochromogenic smooth or smooth/rough colonies on Ogawa egg slants. They were identified as Mycobacterium massiliense by multigenotypic analysis using the 16S rRNA, hsp65, and rpoB genes and the 16S-23S rRNA internal transcribed spacer (ITS) region. However, the use of the 16S rRNA gene sequence and/or DNA-DNA hybridization (DDH Mycobacteria Kit) alone would not distinguish M. massiliense from mycobacteria in the M. chelonae-M. abscessus group. The three isolates were significantly more susceptible to clarithromycin, doxycycline, and minocycline than the M. abscessus and M. bolletii reference strains. One cutaneous isolate and the environmental isolate were in a related cluster by randomly amplified polymorphic DNA PCR (RAPD-PCR). Of the several mycobacterial species found in the day spa, only M. massiliense was isolated from biopsy specimens of the skin lesions, suggesting that this bacterium is a human skin pathogen. This is the first known report of cutaneous M. massiliense infections that could not be attributed to a prior invasive procedure. This is also the first report of M. massiliense infection in Japan.

Assessment of clarithromycin susceptibility in strains belonging to the Mycobacterium abscessus group by erm(41) and rrl sequencing

Clarithromycin was the drug of choice for Mycobacterium abscessus infections until inducible resistance due to erm(41) was described. Because M. abscessus was split into M. abscessus sensu stricto, Mycobacterium massiliense, and Mycobacterium bolletii, we looked for erm(41) in the three species and determined their clarithromycin susceptibility levels. Ninety strains were included: 87 clinical strains from cystic fibrosis patients (61%) and others (39%), representing 43 M. abscessus, 30 M. massiliense, and 14 M. bolletii strains identified on a molecular basis, and 3 reference strains. Clarithromycin and azithromycin MICs were determined by broth microdilution and Etest with a 14-day incubation period. Mutations in rrl (23S rRNA gene) known to confer acquired clarithromycin resistance were also sought. erm(41) was detected in all strains but with two deletions in all M. massiliense strains. These strains were indeed susceptible to clarithromycin (MIC(90) of 1 μg/ml) except for four strains with rrl mutations. M. abscessus strains harbored an intact erm(41) but had a T/C polymorphism at the 28th nucleotide: T28 strains (Trp10 codon) demonstrated inducible clarithromycin resistance (MIC(90) of >16 μg/ml), while C28 strains (Arg10) were susceptible (MIC(90) of 2 μg/ml) except for two strains with rrl mutations. M. bolletii strains had erm(41) sequences similar to the sequence of the T28 M. abscessus group, associated with inducible clarithromycin resistance (MIC(90) of >16 μg/ml). erm(41) sequences appeared species specific within the M. abscessus group and were fully concordant with clarithromycin susceptibility when erm(41) sequencing was associated with detection of rrl mutations. Clarithromycin-resistant strains, including the six rrl mutants, were more often isolated in cystic fibrosis patients, but this was not significantly associated with a previous treatment.

An oxidative environment promotes growth of Mycobacterium abscessus

Mycobacterium abscessus infections, particularly those causing chronic lung diseases, are becoming more prevalent worldwide. M. abscessus infections are difficult to treat because of antibiotic resistance. Thus, new treatment options are urgently needed. M. abscessus is an intracellular pathogen that primarily infects macrophages and fibroblasts. Because this bacterium has only recently been identified as a separate species, very little is known about M. abscessus-host interactions and how M. abscessus growth is regulated. Oxidative stress has long been shown to inhibit the growth of bacterial organisms. However, some intracellular bacteria, such as Mycobacterium tuberculosis, grow well in oxidizing environments. In this study, we show that M. abscessus infection causes the host cell environment to become more oxidizing. Furthermore, we show that a more oxidizing environment leads to enhanced growth of M. abscessus inside macrophages. In the presence of antioxidants, MnTE-2-PyP (chemical name: manganese(II) meso-tetrakis-(N-methylpyridinium-2-yl) porphyrin) or N-acetyl-l-cysteine, M. abscessus growth is inhibited. These results lead us to postulate that antioxidants may aid in the treatment of M. abscessus infections.

Clinical significance of differentiation of Mycobacterium massiliense from Mycobacterium abscessus

RATIONALE

Mycobacterium massiliense has been recognized as a separate species from Mycobacterium abscessus; however, little is known regarding the clinical impact of this differentiation.

OBJECTIVES

To compare clinical features and treatment outcomes between patients with M. abscessus lung disease and those with M. massiliense lung disease.

METHODS

We performed molecular identification of stored clinical isolates of M. abscessus complex and compared clinical characteristics and treatment outcomes between 64 patients with M. abscessus lung disease and 81 patients with M. massiliense lung disease.

MEASUREMENTS AND MAIN RESULTS

The clinical and radiographic manifestations of disease caused by each species were similar. Standardized combination antibiotic therapy, including a clarithromycin-containing regimen in combination with an initial 4-week course of cefoxitin and amikacin, was given to 57 patients (24 with M. abscessus and 33 with M. massiliense) for more than 12 months. The proportion of patients with sputum conversion and maintenance of negative sputum cultures was higher in patients with M. massiliense infection (88%) than in those with M. abscessus infection (25%; P < 0.001). Inducible resistance to clarithromycin (minimal inhibitory concentrations ≥ 32 μg/ml) was found in all tested M. abscessus isolates (n = 19), but in none of the M. massiliense isolates (n = 28).

CONCLUSIONS

Treatment response rates to combination antibiotic therapy including clarithromycin were much higher in patients with M. massiliense lung disease than in those with M. abscessus lung disease. The inducible resistance to clarithromycin could explain the lack of efficacy of clarithromycin-containing antibiotic therapy against M. abscessus lung disease.

Rapidly growing nontuberculous mycobacteria cultured from home tap and shower water

Tap and shower water at two locations in the Netherlands was examined for the presence of rapidly growing nontuberculous mycobacteria. Cultures yielded Mycobacterium peregrinum, M. salmoniphilum, M. llatzerense, M. septicum, and three potentially novel species, a distribution different from that in clinical samples.

Pulmonary Mycobacterium abscessus in an AIDS patient

Mycobacterium abscessus is an unusual pathogen in HIV/AIDS patients. We report a case of M abscessus with review of the literature, which revealed 1 confirmed case in an HIV/AIDS patient. Preliminary diagnosis was presumed to be pulmonary tuberculosis secondary to positive acid-fast bacilli in sputum stain. After initial treatment failure, sputum stains were repeated, and the species was identified; therefore the antibiotic regimen was tailored for M abscessus. Early recognition and treatment of nontuberculous mycobacteria is vital in the reduction of complications and mortality in HIV/AIDS patients. M abscessus is a highly virulent and should be considered as a potential offending pathogen on differential diagnosis in an immunocompromised host.