Mycobacterium Infection of Abscess with Hemoptysis as the Initial Manifestation.

BACKGROUND: Mycobacterium abscessus is a new pathogen in recent years, which belongs to non-tuberculosis mycobacterium. Mycobacterium abscessus is widely involved in many nosocomial infections and secondary aggravation of genetic respiratory diseases. Mycobacterium abscessus is naturally resistant to most antibiotics and is difficult to treat. We report a case of mycobacterium abscessus infection with hemoptysis as the first manifestation. METHODS: Bronchoscopy, next-generation sequencing (NGS). RESULTS: Acid-fast staining of bronchoscopic lavage fluid showed that a small amount of acid-fast bacilli could be seen. NGS test showed the presence of Mycobacterium abscess, sequence number 137 (reference range ≥ 0), and symptomatic treatment against non-tuberculosis mycobacteria. CONCLUSIONS: For the follow-up infection of patients with hemoptysis, the treatment effect of antibiotics is not good, so the pathological tissue should be obtained by bronchoscopy or percutaneous lung biopsy in time, and the diagnosis should be confirmed by NGS if necessary.

Construction of Composite Correlation Index Matrix and Analysis of Cultural Properties of Representatives of Mycobacterium abscessus Complex Isolated from Patients with Cystic Fibrosis.

BACKGROUND: Microbiological diagnosis of mycobacteriosis is often difficult, as it is necessary to differentiate between transient colonization and active infection. METHODS: We studied the cultural properties of Mycobacterium abscessus complex (MABSc) strains obtained from cystic fibrosis patients, and also analyzed composite correlation index (CCI) values in patients with repeated MABSc inoculation and their correlation with the presence of clinical and radiological manifestations of mycobacteriosis. RESULTS: As a result, MABSc more often grew in S-form colonies in patients without clinical manifestations of chronic infection, while R-form colonies were characteristic of patients with chronic infection and clinical symptoms. At the same time, in patients examined once, no growth of colonies in the R-form was recorded, and all strains produced growth in the form of either S-colonies or in the S- and R-forms simultaneously. Statistically significant results were obtained for the relationship of the CCI with the clinical and radiological picture. In addition, a heterogeneous MABSc population with low CCI score values correlated with the development of mycobacteriosis in patients. In patients with high CCI score values (homogeneity of isolated strains), on the contrary, there were no radiological or clinical signs of the disease. CONCLUSION: These data make it possible to build a strategy for monitoring patients depending on changes in CCI score values. The use of CCI matrix to evaluate microorganisms' identification results is a potentially new method that expands the use of matrix-assisted laser desorption ionization time-of-flight mass spectrometry.

In vitro effects of the new oral ß-lactamase inhibitor xeruborbactam in combination with oral ß-lactams against clinical Mycobacterium abscessus isolates.

Non-tuberculosis mycobacteria (NTM), particularly Mycobacterium abscessus subsp. abscessus (M. abscessus), are increasingly being recognized as etiological agents of NTM pulmonary disease. However, treatment options for M. abscessus are limited owing to their natural resistance to most antibiotics, including ß-lactams. M. abscessus produces a class A ß-lactamase, whose activity is inhibited by cyclic boronic acid ß-lactamase inhibitors. We aimed to evaluate the in vitro effects of xeruborbactam, a cyclic boronic acid ß-lactamase inhibitor, against M. abscessus when combined with five ß-lactams (amoxicillin, tebipenem, cefdinir, cefuroxime, and cefoxitin). The drug susceptibilities of 43 M. abscessus clinical isolates obtained from 43 patients between August 2005 and May 2014 were tested. The MIC results for each ß-lactam with or without 4 µg/mL xeruborbactam were examined. Xeruborbactam lowered the MIC90 values of tebipenem, amoxicillin, cefuroxime, and cefdinir by 5, ≥4, 3, and 3 dilutions, respectively. The MIC90 values of cefoxitin without xeruborbactam were 32 µg/mL and did not change upon the addition of xeruborbactam. The lowest MIC90 value was obtained for tebipenem with xeruborbactam. Almost all isolates had an MIC of 4 µg/mL; one isolate had an MIC of 2 µg/mL. With respect to the susceptibility to the same family drug, the number of susceptible isolates increased from 1/43 (2%) to 43/43 (100%) for tebipenem with xeruborbactam. Combining tebipenem and xeruborbactam could be considered an effective all-oral regimen that benefits outpatient treatment of M. abscessus pulmonary disease. IMPORTANCE: Mycobacterium abscessus subsp. abscessus (M. abscessus) disease is treated in two phases; injectable drugs for initial followed by others for continuation. There is a need to develop all-oral treatment methods for M. abscessus infection, especially in the continuation phase. However, treatment options for M. abscessus are limited owing to their natural resistance to most antibiotics. This is the first report to evaluate the in vitro effects of xeruborbactam, a cyclic boronic acid ß-lactamase inhibitor capable of inhibiting the class A ß-lactamase produced by M. abscessus, against 43 M. abscessus clinical isolates when combined with five ß-lactam antibiotics. Xeruborbactam lowered the MIC90 values of tebipenem by five dilutions, and the number of susceptible isolates increased from 1/43 (2%) to 43/43 (100%). We showed that the tebipenem-xeruborbactam combination might be of interest to explore further as a potentially effective oral regimen for outpatient treatment of M. abscessus pulmonary disease.

Three Cases of Non-Tuberculosis Mycobacterium Skin Infection Outbreak in Beauty Institutions.

BACKGROUND: From June 2021 to July 2021, our hospital confirmed 3 cases of Mycobacterium infection in skin abscesses. All 3 patients underwent thread embedding and weight loss surgery at the same informal beauty institution, with a history of silk protein injection. None of the patients had any other underlying diseases or surgical history. Symptoms and signs show that the disease is acute and the course of the disease is short. All patients have found subcutaneous masses in different parts of the body. In most cases, the masses show redness and swelling, and some of the masses are accompanied by tenderness, wave sensation, and rupture. After some of the masses rupture, purulent secretions can be seen. METHODS: The pus secreted by the skin lesions of the three patients were cultured to a single bacterium, which was identified by MALDI-TOF MS. Multiple locus sequence typing (MLST) was performed using three specific genes (hsp65, rpoB, and secA1) and seven housekeeping genes (argH, cya, glpK, gnd, murC, pta, and purH). The results were queried through the MLST database of Mycobacterium abscess. RESULTS: All three strains of bacteria were Mycobacterium abscess type ST279 massiliense subtype. Three antibacterial drugs including cefmetazole, amikacin, and clarithromycin were administered in combination with 5-aminolevulinic acid photodynamic therapy (ALA-PDT). After 3 - 6 months, there was no obvious redness or swelling in the surrounding tissues of the wound, and no obvious purulent secretions were observed. All patients were cured and discharged from the hospital. After a follow-up of six months, there was no recurrence of the lesions. CONCLUSIONS: Medical institutions must strictly follow infection control guidelines and take preventive measures to prevent such incidents from happening again. ALA-PDT as a combination therapy for nontuberculous Mycobacterium (NTM) skin infections can improve treatment efficacy and shorten antibiotic usage time.

Notes from the Field: Potential Outbreak of Extrapulmonary Mycobacterium abscessus subspecies massiliense Infections from Stem Cell Treatment Clinics in Mexico - Arizona and Colorado, 2022.

Mycobacterium abscessus is an intrinsically drug-resistant, rapidly growing, nontuberculous mycobacterium; extrapulmonary infections have been reported in association with medical tourism (1). During November-December 2022, two Colorado hospitals (hospitals A and B) treated patient A, a Colorado woman aged 30-39 years, for M. abscessus meningitis. In October 2022, she had received intrathecal donor embryonic stem cell injections in Baja California, Mexico to treat multiple sclerosis and subsequently experienced headaches and fevers, consistent with meningitis. Her cerebrospinal fluid revealed neutrophilic pleocytosis and grew M. abscessus in culture at hospital A. Hospital A's physicians consulted hospital B's infectious diseases (ID) physicians to co-manage this patient (2).

Identification of the Optimal Cultivation Period Required to Isolate Representatives of Mycobacterium abscessus Complex Isolated from Patients with Cystic Fibrosis.

BACKGROUND: In patients with cystic fibrosis (CF), representatives of the fast-growing Mycobacterium abscessus complex (MABSc) are often distinguished, but the culture of the material taken from such patients increases the growth time. We analyzed the terms of cultivation of MABSc representatives on dense nutrient media and also evaluated the productivity of a modified nutrient medium based on agar for the isolation of Burkholderia cepacia complex (BCC). METHODS: Sixty-four strains of MABSc isolated from patients with CF and suspected tuberculosis were analyzed. The material from the patients was cultured on a universal chromogenic medium, 5% blood agar, yolk-salt agar, selective medium for isolation of BCC, and Löwenstein-Jensen medium. The cultures were incubated for 5 days (37°C, aerobic conditions), after for 23 days (28°C, aerobic conditions). The productivity of the developed nutrient medium was evaluated by the number of cells that gave visible growth after culturing 0.1 mL of a bacterial suspension of 103 CFU/mL. RESULTS: 76.8% of the strains grew in a 2-week period, and 23.2% of the strains were obtained at a later date from 18 to 28 days (average: 21.23 days). The modified medium with a concentration of 240 mg of iron (III) polymaltose hydroxide proved to be the most optimal for the isolation of MABSc. CONCLUSION: When using a chromogenic medium for culture material from patients with CF, it is necessary to extend incubation up to 28 days to increase the probability of MABSc isolation. The modified BCC medium showed a good selectivity result but required further investigation.

Successful management of Mycobacterium abscessus pneumonia in a 53-day-old immunocompetent infant.

Pulmonary infection due to Mycobacterium abscessus complex (MABC) usually occurs in children with underlying risk factors including cystic fibrosis (CF), chronic lung disease, and immunocompromised status, but rarely in immunocompetent children without underlying lung disease, especially in infants. We present a case of MABC pulmonary disease (MABC-PD) in an otherwise healthy 53-day-old male infant with one week of cough and respiratory distress. Computed tomography showed multiple masses across both lungs. Isolated mycobacteria from his bronchoalveolar lavage fluid were identified as MABC. We describe our complete evaluation, including immunodeficiency evaluation incorporating whole exome sequencing and our therapeutic process given complicated susceptibility pattern of the M. abscessus isolate, and review literature for MABC-PD in immunocompetent children. The infant was successfully treated through prolonged treatment with parenteral Amikacin, Cefoxitin, Linezolid, and Clarithromycin, combined with inhaled Amikacin.

Bedaquiline susceptibility testing of Mycobacterium abscessus complex and Mycobacterium avium complex: A meta-analysis study.

OBJECTIVE: This study aims to estimate the overall in vitro activity of bedaquiline (BDQ) against clinical isolates of Mycobacterium abscessus complex (MABS) and M. avium complex (MAC), considering BDQ as a repurposed drug for non-tuberculous mycobacteria (NTM) infections. METHODS: We conducted a systematic review of publications in PubMed/ MEDLINE, Web of Science, and Embase up to 15 April 2023. Studies were included if they followed the Clinical and Laboratory Standards Institute (CLSI) criteria for drug susceptibility testing (DST). Using a random effects model, we assessed the overall in vitro BDQ resistance rate in clinical isolates of MABS and MAC. Sources of heterogeneity were analysed using Cochran's Q and the I2 statistic. All analyses were performed using CMA V3.0. RESULTS: A total of 24 publications (19 reports for MABS and 11 for MAC) were included. Using 1 µg/mL and 2 µg/mL as the breakpoint for BDQ resistance, the pooled rates of in vitro BDQ resistance in clinical isolates of MABS were found to be 1.8% (95% confidence interval [CI], 0.7-4.6%) and 1.7% (95% CI, 0.6-4.4%), respectively. In the case of MAC, the pooled rates were 1.7% (95% CI, 0.4-6.9%) and 1.6% (95% CI, 0.4-6.8%) for 1 µg/mL and 2 µg/mL, respectively. CONCLUSION: This study reports the prevalence of BDQ resistance in clinical isolates of MABS and MAC. The findings suggest that BDQ holds potential as a repurposed drug for treating MABS and MAC infections.

The epidemiology of pulmonary Mycobacterium abscessus species in Japanese population.

BACKGROUND: Mycobacterium abscessus species (MABS) is now a most virulent rapidly growing mycobacteria (RGM), and the rapid increase of MABS was recently observed worldwide, including in Japan. Thus, we gathered evidences of the presence of pulmonary MABS in Japanese population from Japanese articles. METHODS: we searched studies that addressed the isolation of pulmonary non-tuberculous Mycobacteria (NTM) or MABS from clinical respiratory specimens in Japan. RESULTS: the ratio of MABS to NTM was 3.04% (95% confidence interval [CI]: 2.51-3.68), found using the meta-analysis of single proportions. The estimated mean age of patients infected with MABS was 67.72 years (95% CI: 65.41-70.02), found using the meta-analysis of single means. The estimated proportion of females, never smoker, and the co-infection with Mycobacterium avium complex (MAC) was 66.75% (95% CI: 59.23-73.50), 67.57% (95% CI: 62.43-72.32), and 36.74% (95% CI: 25.30-49.90), respectively. The characteristics of MABS in Japan were considerably different from that in Europe and United States from the perspective of age, gender, and complications, wherein the patients in these countries tended to be younger, had lower number of females, and had more occurrences of hereditary diseases, including cystic fibrosis (CF). CONCLUSION: we hypothesized that the characteristics of MABS in the Japanese were involved in those of non-CF MABS, and the distribution of gender and age of MABS were similar to that of MAC in the Japanese.

Spatial Heterogeneity of Nontuberculous Mycobacterial Pulmonary Disease in Shanghai: Insights from a Ten-Year Population-Based Study.

OBJECTIVE: To investigate the spatial heterogeneity of nontuberculous mycobacterial pulmonary disease (NTM-PD) in Shanghai. METHODS: A population-based retrospective study was conducted using presumptive pulmonary tuberculosis surveillance data of Shanghai between 2010 and 2019. The study described the spatial distribution of NTM-PD notification rates, employing hierarchical Bayesian mapping for high-risk areas and the Getis-Ord Gi* statistic to identify hot spots and explore associated factors. RESULTS: Of 1652 NTM-PD cases, the most common species was Mycobacterium kansasii complex (MKC) (41.9%), followed by Mycobacterium avium complex (MAC) (27.1%) and Mycobacterium abscessus complex (MABC) (16.2%). MKC-PD patients were generally younger males with a higher incidence of pulmonary cavities, while MAC-PD patients were more often farmers or had a history of tuberculosis treatment. MKC-PD hot spots were primarily located in the areas alongside the Huangpu River, while MAC-PD hot spots were mainly in the western agricultural areas. Patients with MKC-PD and MAC-PD exhibited a higher risk of spatial clustering compared to those with MABC-PD. CONCLUSIONS: Different types of NTM-PD exhibit distinct patterns of spatial clustering and are associated with various factors. These findings underscore the importance of environmental and host factors in the epidemic of NTM-PD.

Subcutaneous infection caused by Mycobacterium abscessus following botulinum toxin injections: A case report and literature review.

BACKGROUND: The rapid development of cosmetic injections has led to an increased incidence of nontuberculous mycobacterial (NTM) infection. PATIENTS AND METHODS: Here, we presented a case of cutaneous Mycobacterium abscessus infection subsequent to botulinum toxin injection for treating masseter hypertrophy, and reviewed the literature on skin and soft tissue infections caused by NTM after cosmetic injections. RESULTS AND CONCLUSIONS: The patient underwent surgical excision and regular antibiotic therapy and has had nearly 2 months of follow-up without any signs of infection. The diagnosis and treatment of NTM infection have always been challenging, and further research is needed to standardize and guide the treatment.

Disseminated Mycobacterium abscessus infection in a patient on haemodialysis.

We report a 46-year-old woman with disseminated Mycobacterium abscessus infection who was on maintenance haemodialysis for chronic glomerulonephritis. Prolonged blood cultures yielded growth of a rapid-growing nontubercular Mycobacterium. Diagnosis to a species level guided empirical therapy while we awaited antimicrobial susceptibility results. The patient was treated successfully with a multidrug regimen.

Painful Purulent Nodules Caused by Mycobacterium at Site of Lipodissolve Injections.

ABSTRACT: "Lipodissolve" (LD) is a non-FDA-approved solution of phosphatidylcholine in deoxycholate that was developed around 2004. A study of its safety reported minor and uncommon side effects including pain, tender nodules, pigmentary alterations, and ulceration at the site of injection. We present a 53-year-old woman who received LD injections bilaterally to her proximal arms. One week later, she developed painful nodules at each injection site. She was treated with a 10-day course of trimethoprim/sulfamethoxazole without improvement. An incisional biopsy was performed and showed deep dermal suppurative inflammation with numerous neutrophils and granulomas. Stains for bacteria, fungus, and acid-fast organisms were negative. Cultures for acid-fast bacilli grew Mycobacterium abscessus, sensitive to amikacin and clarithromycin. The patient was subsequently treated with intravenous amikacin, azithromycin, and bedaquiline with symptom resolution. Investigation revealed 3 similar infections linked to LD injections originating from the same physician's office. The most common organism implicated in injection infections is Staphylococcus aureus. Infections at injection sites caused by atypical mycobacteria have been reported to occur after tattooing, other types of injections, and implants. Of atypical mycobacteria, M. abscessus accounts for the greatest number of postinjection or iatrogenic infections. Common antitubercular drugs are not effective for treating atypical mycobacteria, making species identification and sensitivity testing imperative for treatment. This case highlights an unusual infection caused by cosmetic injections of LD, previously reported to be associated with minimal side effects, and the importance of examination for acid-fast bacilli and follow-up with culture, even in the absence of organisms identified on stained sections.

The Diagnosis of Nontuberculous Mycobacterial Pulmonary Disease by Single Bacterial Isolation Plus Anti-GPL-Core IgA Antibody.

Although serum anti-glycopeptidolipid (GPL)-core IgA antibody is a highly specific test for infection with Mycobacterium avium complex (MAC), Mycobacterium abscessus, and its subspecies abscessus, subsp. massiliense, and subsp. bolletii (MAB), its use for the definitive diagnosis of MAC pulmonary disease (PD) and MAB-PD are unknown. To clarify the diagnostic accuracy of the anti-GPL-core IgA antibody test among patients with radiologically suspected MAC-PD or MAB-PD who already have a single positive sputum culture test. The first isolations of MAC and MAB from patients with radiologically suspected MAC-PD or MAB-PD at the Osaka Toneyama Medical Center between January 2006 and December 2020 were collected. Patients were enrolled when their serum anti-GPL-core IgA antibody was measured during the 3 months before and after the first isolation. We retrospectively compared the results of anti-GPL-core IgA antibody testing with the final diagnoses based on the current guidelines. We included 976 patients for analysis. The serum anti-GPL-core IgA antibody was positive in 699 patients (71.6%). The positive predictive value of anti-GPL-core IgA antibody for the diagnosis of MAC-PD or MAB-PD was 97.4%. The median time required for the second positive culture after the first isolation was 51 days (interquartile range 12 to 196 days). The positive serum anti-GPL-core IgA antibody test allowed an early and definitive diagnosis of MAC-PD or MAB-PD in those who already had a single positive sputum culture test. IMPORTANCE To satisfy the microbiologic criteria of the current diagnostic guideline for nontuberculous mycobacterial pulmonary disease (PD), at least two positive sputum cultures of the same species of mycobacteria from sputum are required to avoid the casual isolation of mycobacteria. This study showed that the positivity of a serum anti-glycopeptidolipid (GPL)-core IgA antibody test has an excellent diagnostic ability among patients with radiologically suspected Mycobacterium avium complex (MAC)-PD or Mycobacterium abscessus (MAB)-PD who already had a single positive sputum culture test. The usage of single culture isolation plus anti-GPL-core IgA antibody as another diagnostic criterion has a time, cost, and effort-saving effect. Furthermore, it will facilitate the diagnosis of MAC-PD or MAB-PD in the early stage of disease because serum anti-GPL-core IgA antibody becomes high in these patients. Therefore, we proposed adding single culture isolation plus anti-GPL-core IgA antibody as "combined microbiological and serological criteria" to the diagnostic guidelines for MAC-PD and MAB-PD.

CLINICAL CHARACTERISTICS AND VISUAL OUTCOMES IN ENDOPHTHALMITIS AFTER KERATOPROSTHESIS IMPLANTATION.

PURPOSE: To describe the presentation, microbiology, management, and prognosis of eyes with endophthalmitis after Boston keratoprosthesis implantation. METHODS: Retrospective case series with history, diagnostics, management, and outcomes data in endophthalmitis after keratoprosthesis implantation presenting to a tertiary center between 2009 and 2020. RESULTS: Of 137 keratoprosthesis-implanted eyes, 7 eyes of 7 patients (5%) developed endophthalmitis. On presentation, 6 (86%) reported decreased visual acuity, and only 1 (14%) reported pain. Peripheral corneal ulcers were present in 2 eyes (29%). Seidel testing was negative in all cases. Six eyes (86%) had retroprosthetic membranes. One (14%) underwent initial pars plana vitrectomy with mechanical vitreous biopsy, whereas 6 (86%) received a needle vitreous tap-half of which were dry. Organisms were isolated after vitreous tap in two eyes: Streptococcus intermedius and Mycobacterium abscessus. The mean visual acuity preendophthalmitis, at presentation, and at 6 months were 20/267, 20/5,944, and 20/734, respectively. The visual acuity improved 9.08 ± 11.78 Early Treatment Diabetic Retinopathy Study lines from presentation to 6 months. Six-month visual acuity was correlated with preendophthalmitis visual acuity (r = 0.92, P = 0.003) but not presenting visual acuity (P = 0.838). CONCLUSION: Visual acuity at 6 months is correlated with preendophthalmitis visual acuity, not presenting visual acuity. Endophthalmitis should be considered in the differential diagnosis of painless intraocular inflammation any time after keratoprosthesis implantation, even if Seidel negative.

Minimum Inhibitory Concentrations before and after Antibacterial Treatment in Patients with Mycobacterium abscessus Pulmonary Disease.

The clinical importance of Mycobacterium abscessus (MABS) pulmonary disease has been increasing. However, there is still a lack of information about MIC distribution patterns and changes in clinical practice settings. The MIC results of rapidly growing mycobacteria isolated from 92 patients with nontuberculous mycobacterial pulmonary disease diagnosed from May 2019 to March 2021 were retrospectively analyzed. Most of the patients (86 patients; 93.5%) were infected with MABS; 46 with Mycobacterium abscessus subsp. abscessus (Mab), and 40 with Mycobacterium abscessus subsp. massiliense (Mma). Significant differences in susceptibility to clarithromycin (15.2% versus 80.0%, P < 0.001) and azithromycin (8.7% versus 62.5%, P < 0.001) were observed between Mab and Mma. Most isolates were susceptible to amikacin (80; 93.0%), and over half were susceptible to linezolid (48; 55.8%). Only one-quarter of isolates (22, 25.6%) were susceptible to imipenem, while more than half (56; 65.1%) had intermediate susceptibility. Fifty-one isolates (59.3%) had MIC values of less than 1 µg/mL for sitafloxacin, which were significantly higher than isolates for moxifloxacin (5; 5.8%), especially in Mab. Sixty-five (75.6%) isolates had MICs of less than 0.5 µg/mL to clofazimine. Two patients showed obvious MIC result changes: from susceptible to resistant to clarithromycin and from resistant to susceptible to amikacin and imipenem. In conclusion, MABS isolates were relatively susceptible to amikacin and linezolid, and clarithromycin and azithromycin were especially effective against Mma. In addition, sitafloxacin and clofazimine had low MICs and might be effective treatment agents. IMPORTANCE The MICs of isolates from 86 patients with Mycobacterium abscessus (MABS); 46 with Mycobacterium abscessus subsp. abscessus (Mab), and 40 with Mycobacterium abscessus subsp. massiliense (Mma) were retrospectively analyzed. The main findings are as follows: (i) Mma were significantly more susceptible to clarithromycin and azithromycin than Mab, and both subspecies tended to be more susceptible to clarithromycin than azithromycin. (ii) Most isolates were susceptible to amikacin (93.0%), and over half to linezolid (55.8%). (iii) Fifty-one isolates (59.3%) had MIC values of less than 1 µg/mL for sitafloxacin, and 65 (75.6%) had less than 0.5 µg/mL for clofazimine, which seems worth clinical investigating. (iv) Among nine cases analyzed chronological changes, only two patients showed obvious MIC result changes even after the long-term multidrug treatment. The present study revealed MICs of MABS clinical isolates before and after treatment in clinical settings, which could help develop future MABS treatments strategies.

Genome reorganization during emergence of host-associated Mycobacterium abscessus.

Mycobacterium abscessus is a rapid growing, free-living species of bacterium that also causes lung infections in humans. Human infections are usually acquired from the environment; however, dominant circulating clones (DCCs) have emerged recently in both M. abscessus subsp. massiliense and subsp. abscessus that appear to be transmitted among humans and are now globally distributed. These recently emerged clones are potentially informative about the ecological and evolutionary mechanisms of pathogen emergence and host adaptation. The geographical distribution of DCCs has been reported, but the genomic processes underlying their transition from environmental bacterium to human pathogen are not well characterized. To address this knowledge gap, we delineated the structure of M. abscessus subspecies abscessus and massiliense using genomic data from 200 clinical isolates of M. abscessus from seven geographical regions. We identified differences in overall patterns of lateral gene transfer (LGT) and barriers to LGT between subspecies and between environmental and host-adapted bacteria. We further characterized genome reorganization that accompanied bacterial host adaptation, inferring selection pressures acting at both genic and intergenic loci. We found that both subspecies encode an expansive pangenome with many genes at rare frequencies. Recombination appears more frequent in M. abscessus subsp. massiliense than in subsp. abscessus, consistent with prior reports. We found evidence suggesting that phage are exchanged between subspecies, despite genetic barriers evident elsewhere throughout the genome. Patterns of LGT differed according to niche, with less LGT observed among host-adapted DCCs versus environmental bacteria. We also found evidence suggesting that DCCs are under distinct selection pressures at both genic and intergenic sites. Our results indicate that host adaptation of M. abscessus was accompanied by major changes in genome evolution, including shifts in the apparent frequency of LGT and impacts of selection. Differences were evident among the DCCs as well, which varied in the degree of gene content remodelling, suggesting they were placed differently along the evolutionary trajectory toward host adaptation. These results provide insight into the evolutionary forces that reshape bacterial genomes as they emerge into the pathogenic niche.

Assessment of in vitro activities of novel modified antimicrobial peptides against clarithromycin resistant Mycobacterium abscessus.

Mycobacterium abscessus (Mab) is one of the most drug resistant bacteria with a high treatment failure rate. Antimicrobial peptides (AMPs) are alternative therapeutic agents against this infection. This study was aimed to assess the in vitro activities of thirteen AMPs (S5, S52, S6, S61, S62, S63, KLK, KLK1, KLK2, Pug-1, Pug-2, Pug-3 and Pug-4) that have never been investigated against drug resistant Mab isolates. Only four novel modified AMPs (S61, S62, S63 and KLK1) provided the lowest minimum inhibitory concentration (MIC) values ranging from 200-400 µg/ml against the Mab ATCC19977 strain. These four potential AMPs were further tested with 16 clinical isolates of clarithromycin resistant Mab. The majority of the tested strains (10/16 isolates, 62.5%) showed ~99% kill by all four AMPs within 24 hours with an MIC <50 µg/ml. Only two isolates (12.5%) with acquired clarithromycin resistance, however, exhibited values <50 µg/ml of four potential AMPs, S61, S62, S63 and KLK1 after 3-days-incubation. At the MICs level, S63 showed the lowest toxicity with 1.50% hemolysis and 100% PBMC viability whereas KLK1 showed the highest hemolysis (10.21%) and lowest PBMC viability (93.52%). S61, S62 and S63 were further tested with clarithromycin-AMP interaction assays and found that 5/10 (50%) of selected isolates exhibited a synergistic interaction with 0.02-0.41 FICI values. This present study demonstrated the potential application of novel AMPs as an adjunctive treatment with clarithromycin against drug resistant Mab infection.