In vitro susceptibility patterns for rapidly growing nontuberculous mycobacteria in the United States

Antimicrobial susceptibility testing for rapidly growing mycobacteria (RGM) is uncommon or only performed in large reference laboratories. Here we developed a cumulative antibiogram for 14 RGM using the largest sample size to date (N = 3860). All RGM showed 82% to 100% susceptibility to amikacin. Mycobacterium abscessus showed low percentages of susceptibility to most antimicrobials; of antimicrobials without interpretations, the minimum inhibitory concentration-90 for clofazimine was low (≤0.5mg/L). All three subspecies had ≤2.6% rrl resistance mutations, however intact erm(41) was detected in 70% to100% of M. abscessus abscessus and bolletii. Mycobacterium chelonae had a similar susceptibility pattern to M. abscessus subsp. massiliense and Mycobacterium immunogenum except that it was susceptible to tobramycin (87%). Mycobacterium fortuitum complex and similar organisms showed higher frequency of susceptibility to fluoroquinolones, beta-lactams, linezolid, and trimethoprim/sulfamethoxazole. Although relatively small published RGM antibiograms showed substantial variance, a comprehensive antibiogram can help influence treatment and monitoring patterns of resistance.     

Treatment outcomes of macrolide-susceptible Mycobacterium abscessus lung disease

Mycobacterium abscessus lung disease is difficult to treat due to inducible resistance to macrolides. However, 15%–20% of isolates are macrolide susceptible. In 14 patients with macrolide-susceptible M. abscessus lung disease, all isolates had nonfunctional erm(41) gene, and sputum culture conversion rate was achieved in 93% (13/14) following antibiotic therapy.     

Drug susceptibility patterns of Mycobacterium abscessus and Mycobacterium massiliense isolated from respiratory specimens

In this study, we aimed to retrospectively investigate and compare the drug susceptibility patterns of two major Mycobacterium abscessus complex (MABC) species; M. abscessus and M. massiliense. A total of 546?MABC respiratory isolates (277?M. abscessus and 269?M. massiliense) from 2011 to 2016 were analyzed in this study. We estimated minimum inhibitory concentrations (MICs) using the broth microdilution method, and we calculated MIC₅₀ and MIC₉₀ values from the MIC distribution. Both M. abscessus and M. massiliense were highly susceptible to amikacin and linezolid. For M. abscessus, the proportions of inducible and acquired resistance to clarithromycin were 68.6% and 12.3%, respectively. Only 15.2% of M. abscessus remained susceptible at day 14. On the other hand, none of the M. massiliense showed inducible resistance and 6.3% showed acquired resistance to clarithromycin. A total of 92.6% of the M. massiliense remained susceptible at day 14. The resistance rate of M. abscessus to moxifloxacin (90.3%) was significantly higher than that of M. massiliense (83.3%; p?=?0.016). These susceptibility differences may explain the divergent treatment outcomes between patients with pulmonary disease caused by these two species.     

Differences in drug susceptibility pattern between Mycobacterium avium and Mycobacterium intracellulare isolated in respiratory specimens

Mycobacterium avium complex (MAC) is the most common etiologic organisms of nontuberculous mycobacteria (NTM) lung disease. In this study, we aimed to retrospectively investigate the differences in drug susceptibility patterns of two major MAC species; Mycobacterium avium and Mycobacterium intracellulare. A total of 1883 major two MAC isolates (1060 M. avium and 823 M. intracellulare) from respiratory specimens were included in this study during the period 2011─2016. The minimum inhibitory concentrations (MICs) were determined by broth microdilution method and MIC₅₀/MIC₉₀ values were derived from MIC distribution. M. intracellulare had generally low susceptible rates than M. avium for almost all tested antimicrobials except ethambutol and amikacin. The susceptible rate to clarithromycin was >94% of the MAC without significant differences between the two species. The MIC₅₀ values of ciprofloxacin, clarithromycin, linezolid, moxifloxacin, and rifampicin were higher in M. intracellulare than in M. avium, contrary to the results of ethambutol with a higher MIC₅₀ in M. avium. In general, M. intracellulare showed a higher resistance rate and higher MIC₅₀ values than M. avium. Differences between this study and previous reports suggest regional differences in drug susceptibility profile of MAC species.     

Rapid identification of strains belonging to the Mycobacterium abscessus group through erm(41) gene pyrosequencing

Mycobacterium abscessus and Mycobacterium massiliense lung infections have different clarithromycin susceptibilities, making proper identification important; however, standard multi-gene sequencing in clinical laboratories is laborious and time consuming. We developed a pyrosequencing-based method for rapid identification of strains belonging to the M. abscessus group by targeting erm(41). We examined 55 isolates from new pulmonary M. abscessus infections and identified 28 M. abscessus, 25 M. massiliense, and 2 Mycobacterium bolletii isolates. Multi-gene sequencing of 16S rRNA, hsp65, rpoB, and the 16S–23S ITS region was concordant with the results of erm(41) pyrosequencing; thus, the M. abscessus group can be identified by single-nucleotide polymorphisms in erm(41). The method also enables rapid identification of polymorphic, inducible clarithromycin-resistant sequevars (T28 or C28). Pyrosequencing of erm(41) is a rapid, reliable, high-throughput alternative method for identifying and characterizing M. abscessus species. Further testing of a diverse collection of isolates is necessary to demonstrate the discriminatory power of erm(41) sequencing to differentiating species with this highly divergent group.     

Clinical characteristics of extrapulmonary nontuberculous mycobacteria infections in comparison with pulmonary infections: A single-center,retrospective study in Japan

IntroductionThe prevalence of nontuberculous mycobacteria (NTM) infections is increasing worldwide. Although NTM can affect extrapulmonary organs, studies on the clinical characteristics of extrapulmonary NTM are rare.MethodsWe retrospectively analyzed patients who were newly diagnosed with NTM infections at Hiroshima University Hospital between 2001 and 2021 to investigate species distribution, infected sites, and risk factors of extrapulmonary NTM compared to pulmonary NTM.ResultsOf the 261 NTM infections, 9.6% and 90.4% had extrapulmonary and pulmonary NTM, respectively. The mean ages of patients with extrapulmonary and pulmonary NTM were 53.4 and 69.3 years, 64.0% and 42.8% were male, 36.0% and 9.3% received corticosteroids, 20.0% and 0% had acquired immune deficiency syndrome (AIDS), and 56.0% and 16.1% had any immunosuppressive conditions, respectively. Younger age, corticosteroid use, and AIDS were associated with extrapulmonary NTM. In pulmonary NTM, Mycobacterium avium complex (MAC) accounted for 86.4% of NTM species, followed by M. abscessus complex (4.2%), whereas in extrapulmonary NTM, M. abscessus complex, MAC, M. chelonae, and M. fortuitum accounted for 36.0%, 28.0%, 12.0%, and 8.0%, respectively. Compared to pulmonary NTM, extrapulmonary NTM were significantly more likely to be rapid-growing mycobacteria (RGM) (56.0% vs. 5.5%). The most common sites of infection were the skin and soft tissues (44.0%), followed by the blood (20.0%), tenosynovium, and lymph nodes (12.0%).ConclusionYounger age and immunosuppressive conditions are associated with extrapulmonary NTM, with a higher prevalence of RGM in extrapulmonary NTM than in pulmonary NTM. These results provide a better understanding of extrapulmonary NTM.     

In Vitro Synergy between Clofazimine and Amikacin in Treatment of Nontuberculous Mycobacterial Disease

Disease caused by nontuberculous mycobacteria (NTM) is increasing in frequency. The outcome of treatment for NTM lung disease is poor, particularly lung disease caused by Mycobacterium simiae and M. abscessus. Exploring synergy between active available drugs is a sensible way forward given the lack of new active drugs. We tested for synergy between amikacin and clofazimine, using standardized methods, in 564 consecutive clinical isolates identified as 21 species of rapidly growing mycobacteria, 16 clinical M. avium complex isolates, and 10 M. simiae isolates. Clofazimine and amikacin are each active in vitro against NTM; 97% (n = 548) of the rapid growers revealed MICs of clofazimine of ≤1 μg/ml, and 93% (n = 524) proved susceptible to amikacin. The combination showed significant synergistic activity in 56 of 68 (82%) eligible M. abscessus isolates, 4 of 5 M. chelonae isolates, and 1 M. fortuitum and 1 M. cosmeticum isolate, with 4- to 8-fold decreases in MICs to both drugs. Significant synergy could also be demonstrated against all M. avium complex and M. simiae isolates, with fractional inhibitory concentrations of <0.5. Clofazimine and amikacin show significant synergistic activity against both rapidly and slowly growing nontuberculous mycobacteria. The safety and tolerability of adding clofazimine to amikacin-containing regimens should be tested in clinical trials, and the results of susceptibility tests for these two compounds and their combination merit clinical validation. Synergy between clofazimine and other antibiotics with intracellular targets should be explored.     

Native-valve endocarditis caused by Mycobacterium chelonae, misidentified as polymicrobial gram-positive bacillus infection

Mycobacterium chelonae, a species of rapidly growing mycobacteria, may grow in routine blood culture media and stain as gram-positive bacilli, which may cause diagnostic confusion. A patient with native-valve endocarditis caused by M. chelonae, which was misidentified as various gram-positive bacilli, is presented.     

Mycobacterium chelonae bloodstream infection induced by osteomyelitis of toe: A case report

Mycobacterium chelonae is a rapidly growing mycobacterium that has the potential to cause refractory infections in humans. Mycobacteremia resulting from the organism is extremely rare, and its clinical features are yet to be uncovered. We herein present a case of M. chelonae bloodstream infection involving an immunocompromised older patient. A 79-year-old woman, on a long-term treatment with prednisolone plus tacrolimus for rheumatoid arthritis, visited our outpatient department complaining of deteriorating pain and swelling at her right 1st toe. Laboratory parameters showed elevated C-reactive protein and leukocytosis, and magnetic resonance imaging indicated osteomyelitis at the proximal phalanx of her right 1st toe. Considering the refractory course, the infected toe was immediately amputated. M. chelonae was isolated from bacterial cultures of the resected tissue and blood (BD BACTEC™ FX blood culture system, Becton Dickinson, Sparks, MD, USA), leading to a diagnosis of disseminated M. chelonae infection. We treated the patient with an antibiotic combination of clarithromycin, minocycline, and imipenem (2 weeks), which was converted to oral therapy of clarithromycin, doxycycline, and levofloxacin. This case highlighted the potential pathogenesis of M. chelonae to cause mycobacteremia in an immunocompromised patient.     

Mycobacterium abscessus and massiliense lung infection during macrolide treatment for bronchiolitis obliterans after allogeneic hematopoietic stem cell transplantation

In patients undergoing allogeneic hematopoietic stem cell transplantation (allo-SCT), post-transplant lung infection is critical for their prognosis. Mycobacterium abscessus complex is not fully recognized as a nontuberculous mycobacteria (NTM) pathogen of post-SCT lung infection. Here, we present three post-allogeneic SCT patients who developed pulmonary infection caused by M. abscessus complex including M. abscessus and M. massiliense. In all three cases, macrolide antibiotics had been administered for bronchiolitis obliterans syndrome (BOS) before the confirmation of their infection, and macrolide resistance was noted in the M. abscessus isolates, one of which resulted in an unfavorable treatment outcome. It is important to consider M. abscessus lung infection as well as other NTM in patients receiving allo-SCT, particularly those receiving macrolide therapy for BOS.     

Utility of high-performance liquid chromatography analysis of mycolic acids and partial 16S rRNA gene sequencing for routine identification of Mycobacterium spp. in a national reference laboratory

High-performance liquid chromatography analysis of mycolic acids and partial gene sequencing for the first 500-bp 5′ end of the 16S rRNA gene were used singularly and in combination to evaluate the final identification of species. Examination of 200 cultures revealed 100 strains of slowly growing mycobacteria (SGM), 91 strains of rapidly growing mycobacteria (RGM), and 9 strains of other genera. SGM were discriminated in complexes with both methods for 56 strains, composed primarily of the Mycobacterium spp.: Mycobacterium avium, Mycobacterium terrae, and Mycobacterium simiae–Mycobacterium lentiflavum. For RGM, 73 strains were associated with complexes designated as Mycobacterium abscessus–Mycobacterium chelonae, Mycobacterium fortuitum–Mycobacterium peregrinum, and Mycobacterium mucogenicum–Mycobacterium phocaicum. Consistent identification of all the isolates differentiated to single species within the Mycobacterium genus was not possible with either test method. Sequencing results often distinguished complexes containing fewer species, and combining the results from each method increased the confidence of identifying the correct species.     

Transition Metal–α-Amino Acid Complexes with Antibiotic Activity against Mycobacterium spp.

Synthetic iridium-, rhodium-, and ruthenium-amino acid complexes with hydrophobic l-amino acids have antibiotic activity against Mycobacterium spp., including Mycobacterium bovis BCG and the rapidly growing species Mycobacterium abscessus and Mycobacterium chelonae. Concentrations of transition metal-amino acid complexes demonstrating hemolysis or cytotoxicity were 10- to 25-fold higher than were the MICs.     

Vertebral osteomyelitis caused by Mycobacteroides abscessus subsp. abscessus resulting in spinal cord injury due to vertebral body fractures

Nontuberculous mycobacteria (NTM) rarely cause vertebral osteomyelitis; however, the clinical characteristics of vertebral osteomyelitis caused by NTM are poorly understood due to its rarity. A 74-year-old man with lung cancer was treated with prednisolone for immune checkpoint inhibitor-associated immune-related adverse events. He had been experiencing mild back pain without febrile episodes for five months, and was admitted to the hospital for worsening back pain and progressive paraplegia. Magnetic resonance imaging showed spinal cord compression at T4-5 due to fractures of the T5 and T7 vertebral bodies. The culture of a sample of pus from the T7 vertebral body obtained at the time of spinal fusion surgery yielded the Mycobacteroides abscessus (M. abscessus) complex. The patient was diagnosed with vertebral osteomyelitis caused by M. abscessus complex and treated with clarithromycin, amikacin, and imipenem; clarithromycin was later replaced by sitafloxacin because of inducible macrolide resistance. However, his neurologic deficits were irreversible, and he died due to a deteriorating general condition. The strain was identified up to subspecies level as M. abscessus subsp. abscessus by hsp65 and rpoB sequencing and nucleic acid chromatography. Although vertebral osteomyelitis due to NTM is rare, delayed diagnosis can lead to serious complications or poor outcomes. A prolonged clinical course, less frequent fever, vertebral destruction or spinal deformity, neurological deficits, or immunosuppressed conditions might be suggestive of NTM vertebral osteomyelitis.     

Mycobacterium abscessus subsp. abscessus empyema complicated with subcutaneous abscess

There have been no case reports of thoracic subcutaneous abscess after surgery for Mycobacterium abscessus complex associated empyema. We herein report a case of Mycobacterium abscessus subsp. abscessus (M. abscessus subsp. abscessus) induced subcutaneous abscesses following surgical treatment for concurrent M. abscessus subsp. abscessus -associated empyema and pneumothorax. A 75-year-old woman had M. abscessus subsp. abscessus -associated empyema and pneumothorax. She underwent surgical treatment of decortication and fistulectomy and suffered from M. abscessus subsp. abscessus -associated subcutaneous abscesses after thoracentesis/drainage. A multidisciplinary approach combined with surgical care, thermal therapy, and multidrug chemotherapy contributed to a successful result. An early multidisciplinary approach is believed to be important in cases of M. abscessus subsp. abscessus -associated empyema and subcutaneous abscess.     

Three cases of otitis media caused by Mycobacterium abscessus subsp. abscessus: Importance of medical treatment and efficacy of surgery

This study aimed to assess the clinical presentation, antibiotic therapy, surgery, and outcomes in patients with otitis media caused by Mycobacterium abscessus subsp. abscessus and discuss the efficacy of surgery. This is a retrospective case review of three patients diagnosed with otomastoiditis caused by M. abscessus subsp. abscessus. All patients had refractory otorrhea. One patient had granulation tissue in the tympanic membrane. They received medical treatment and underwent surgery. Otorrhea was resolved several months after the initiation of long-term multiantibiotic therapy in all cases. The timing of surgery varied among patients. Before initiating antibiotic therapy, mastoidectomy was performed to achieve definitive diagnosis in two patients, and wound dehiscence developed in these patients. Two patients underwent debridement after the initiation of multiantibiotic therapy. After antibiotic administration, tympanoplasty was performed to improve hearing in one patient. All patients achieved culture negativity after treatment, and no recurrences have been noted. From three cases, it is suggested that the mainstay of treatment for M. abscessus subsp. abscessus is long-term multiantibiotic therapy, and surgery itself may have little effect on achieving ear dryness. Thus, in most patients, drug therapy should be prioritized. Considering postoperative complications, surgery before achieving ear dryness should be avoided, except in emergency cases. In addition, if the diagnosis is not confirmed by repeated bacteriological tests, mastoidectomy should be performed to collect specimens. Tympanoplasty for hearing loss or eardrum perforation is recommended after discontinuation of medications.     

Inactivation of nontuberculous mycobacteria by gaseous ozone treatment

Nontuberculous mycobacteria (NTM) are environmental bacteria resistant to many common disinfectants and ultraviolet radiation. Inhalation of aerosols generated from NTM-containing water and soil causes NTM lung disease, especially in people with underlying lung diseases and decreased immunity. To prevent healthcare-acquired NTM infections, it is important to eradicate NTM living in hospital environments. Therefore, we evaluated the efficacy of gaseous ozone for the inactivation of NTM, namely Mycobacterium (M.) avium, M. intracellulare, M. kansasii, M. abscessus subsp. abscessus and M. abscessus subsp. massiliense. Gaseous ozone treatment at 1 ppm for 3 h reduced the bacterial number of all strains by more than 97%. Gaseous ozone treatment could be a practical, effective and convenient disinfection method for NTM living in hospital environments.     

Mycobacterium wolinskyi Infection Confirmed by rpoB Gene Sequencing

Identification of rapidly growing mycobacteria (RGM) is problematic because there are many taxonomic changes. 16S rRNA gene is commonly used to identify Mycobacterium species, but alternative gene targets have been introduced for more accurate identification. We report a rare case of a prosthetic knee infection due to Mycobacterium wolinskyi. The isolate was not identified by 16S rRNA gene sequencing alone and substantially confirmed by rpoB gene sequencing. The identification was delayed because our laboratory did not routinely identify RGM to the species level. Simultaneous sequencing of both 16S rRNA and rpoB genes will allow rapid and accurate identification of M. wolinskyi isolates. J. Clin. Lab. Anal. 26:325‐327, 2012. © 2012 Wiley Periodicals, Inc.     

In vitro activity of tedizolid against the Mycobacterium abscessus complex

Infections due to Mycobacterium abscessus carry a poor prognosis since this rapidly growing mycobacterium is intrinsically resistant to most antibiotics. Here, we evaluate the in vitro activity of the new oxazolidinone tedizolid against a collection of 44 M. abscessus clinical isolates. The MIC₅₀s and MIC₉₀s of tedizolid (2 and 8 μg/mL, respectively) were 2- to 16-fold lower than those of linezolid. There was no difference between the 3M. abscessus subspecies. Time-kill assays did not show any bactericidal activity at 4- and 8-fold the MIC. Combination of tedizolid with clarithromycin was synergistic against 1 out of 6 isolates, while indifferent interactions were observed for tedizolid combined with tigecycline, ciprofloxacin, and amikacin.     

In vitro activity between linezolid and other antimicrobial agents against Mycobacterium abscessus complex

Linezolid (LZD) serves as an effective option in the treatment of Mycobacterium abscessus complex (MABC) infection. Unfortunately, the combined activities of LZD with other antimicrobial agents against MABC have not been evaluated systemically. In this study, we randomly selected 32 Mycobacterium abscessus and 32 Mycobacterium massiliense isolates for the determination of in vitro synergistic effect between LZD and other antimicrobial agents, including amikacin (AMK), moxifloxacin (MOX), cefoxitin (CFX) and tigecycline (TGC). Out of 64 MABC isolates tested, only one (1.6%, 1/64) and two (3.2%, 2/64) exhibited resistance to AMK and LZD, respectively. Statistical analysis revealed that the percentage of TGC-resistant isolates was significantly lower among M. massiliense (9.4%, 3/32) than that among M. abscessus (25.0%, 8/32, P < 0.001). In addition, LZD and AMK showed synergy for 29 MABC isolates (45.3%), whereas no antagonism was noted for this combination. The second mostly frequent synergistic effect was found in LZD plus TGC combination, and 26.6% (17/64) of the strains tested exhibited synergy. In contrast, LZD-CFX and LZD-MOX combinations appeared antagonistic for half of the isolates (48.4%, 31/64 for CFX and 51.6%, 33/64), and almost no synergistic effect was reported in any of the strains for these two combinations. In conclusion, our data reveal that LZD and AMK show the most potent activity against MABC. The frequent synergism is observed in LZD-AMK and LZD-TGC combinations, while LZD rarely exhibits in vitro synergy with MOX and CFX when tested against MABC.