Mycobacterium Abscessus Complex Infections Research Articles

Therapy of Mycobacterium abscessus Infections in Solid Organ Transplant Patients.

Mycobacterium abscessus complex (MABC), a rapidly growing Mycobacterium, is one of the most common causes of non-tuberculous mycobacteria (NTM) infections in the United States of America, and it has been associated with a wide spectrum of infections in immunocompetent and immunosuppressed individuals. Eradicating MABC is very challenging, even with prolonged combination therapies. The management of MABC infections in solid organ transplant (SOT) patients is usually complex given their net state of immunosuppression, associated comorbidities, and potential drug-drug interactions, among other things. In this manuscript, we discussed the antimicrobial management of pulmonary and extrapulmonary MABC infections. In addition, we reviewed promising novel therapies such as clofazimine, omadacycline, bedaquiline, and inhaled tigecycline that could join the existing antimicrobial armamentarium to fight this infection associated with significant morbidity and mortality. However, further studies are needed, especially among the immunocompromised host.

Analysis of Phenotypic and Genotypic Susceptibility to Clarithromycin and Amikacin of Mycobacterium abscessus Complex Strains Isolated from Cystic Fibrosis Patients.

Mycobacterium abscessus complex infections are ever on the rise. To curb their increasing evolution, we performed an in-depth study of 43 clinical isolates of cystic fibrosis patients obtained from 2009 to 2020. We identified their subspecies, uncovered their genotypic resistance profiles, characterised their antibiotic-resistant genes, and assessed their phenotypic antibiotic susceptibilities. The phenotypic and genotypic methods showed total agreement in terms of resistance to clarithromycin and amikacin. Of the 43 clinical strains, 28 belonged to M. abscessus subsp. abscessus (65.1%), 13 to M. abscessus subsp. massiliense (30.2%), and 2 to M. abscessus subsp. bolletii (4.6%). The resistant rates for clarithromycin and amikacin, the two main drugs against M. abscessus complex pulmonary infections, were 64.2% and 14.2%, respectively. We found three strains of M. abscessus subsp. abscessus that showed heteroresistance in the rrl and rrs genes, and these strains also presented double-resistance since they were macrolide- and aminoglycoside-resistant. M. abscessus subsp. abscessus showed a high minimum inhibitory concentration (MIC) and a resistant percentage larger than or equal to 88% to cefoxitin, ciprofloxacin, moxifloxacin, doxycycline, imipenem, and trimethoprim-sulfamethoxazole. These results show a panorama of the high resistance of Mycobacterium abscessus complex to current drugs for cystic fibrosis patients. Thus, other treatment methods are urgently needed.

Nontuberculous mycobacterial (NTM) infections in bronchiectasis patients: A retrospective US registry cohort study

RationaleLongitudinal epidemiological and clinical data are needed to improve the management of patients with bronchiectasis developing nontuberculous mycobacterial (NTM) pulmonary disease. ObjectivesTo describe the epidemiology, patient management, and treatment outcomes of NTM infections in patients with bronchiectasis enrolled in the United States Bronchiectasis and NTM Research Registry (US BRR). MethodsThis was a retrospective cohort study of patients with bronchiectasis and NTM infections enrolled with follow-up in the US BRR in 2008–2019. The study included patients with ≥1 positive NTM respiratory culture in the 24-month baseline period (baseline NTM cohort) and/or during the annual follow-up visits (incident NTM cohort). Incidence, prevalence, baseline patient characteristics, treatment exposure, treatment outcomes, and respiratory clinical outcomes were described in the baseline NTM cohort, incident NTM cohort, and both cohorts combined (prevalent NTM cohort). ResultsBetween 2008 and 2019, 37.9% (1457/3840) of patients with bronchiectasis in the US BRR met the inclusion criteria for this study and were reported to have Mycobacterium avium complex (MAC) and/or Mycobacterium abscessus complex (MABSC) infections. MAC prevalence increased steadily in the US BRR during 2009–2019; incidence was relatively stable, except for a peak in 2011 followed by a slow decrease. MABSC and mixed MAC/MABSC infections were rare. Most patients with bronchiectasis and NTM infections in the registry were female, White, and aged >65 years. The antibiotics administered most commonly reflected current guidelines. In the prevalent cohort, 44.9% of MAC infections and 37.1% of MABSC infections remained untreated during follow-up, and MAC treatment was initiated with delay (>90 days after positive NTM respiratory culture) twice as frequently as promptly (≤90 days after positive NTM respiratory culture) (68.6% vs 31.4%, respectively). The median time from diagnosis to treatment was shorter for MABSC versus MAC infections (194.0 days [interquartile range (IQR) 8.0, 380.0] vs 296.0 days [IQR 35.0, 705.0], respectively). Among patients with MAC infections who completed treatment, 27.6% were classified as cured and 29.6% as treatment failure during the annual follow-up visit window. For MABSC, these proportions were 25.0% and 28.0%, respectively. ConclusionsA considerable proportion of MAC and MABSC infections were untreated or treated after initial delay/observation. MABSC infections were more likely to be treated and start treatment sooner than MAC infections. Further longitudinal studies are warranted to evaluate the monitor-with-delay approach and inform clinical guidelines.

Clinical characteristics and drug susceptibility profiles of Mycobacterium abscessus complex infection at a medical school in Thailand

ObjectivesThis study investigated the differences in epidemiological and clinical data, and antimicrobial susceptibilities among different subspecies of Mycobacterium abscessus complex (MABSC) clinical isolates at a medical school in Thailand.MethodsA total of 143 MABSC clinical isolates recovered from 74 patients were genotypically analyzed for erm(41), rrl, and rrs mutations, and antimicrobial susceptibilities were determined using a broth microdilution method. Patient characteristics and clinical outcomes were reviewed from the medical records.ResultsSeventy-four patients were infected with 28/74 (37.8%) M. abscessus subspecies abscessus (MAB), 43/74 (58.1%) M. abscessus subsp. massiliense (MMA), and 3/74 (4.1%) M. abscessus subsp. bolletii (MBO). The clinical findings and outcomes were generally indistinguishable between the three subspecies. All three subspecies of MABSC clinical isolates exhibited high resistance rates to ciprofloxacin, doxycycline, moxifloxacin, TMP/SMX, and tobramycin. MAB had the highest resistance rates to clarithromycin (27.8%, 20/72) and amikacin (6.9%, 5/72) compared to MBO and MMA, with p < 0.001 and p = 0.004, respectively. In addition, the rough morphotype was significantly associated with resistance to amikacin (8.9%, 5/56), clarithromycin (26.8%, 15/56), and imipenem (76.8%, 43/56) (p < 0.001), whereas the smooth morphotype was resistant to linezolid (57.1%, 48/84) (p = 0.002). In addition, T28 of erm(41), rrl (A2058C/G and A2059C/G), and rrs (A1408G) mutations were detected in 87.4% (125/143), 16.1% (23/143), and 9.1% (13/143) of MABSC isolates, respectively.ConclusionsThree MABSC subspecies caused a variety of infections in patients with different underlying comorbidities. The drug susceptibility patterns of the recent circulating MABSC strains in Thailand were different among the three MABSC subspecies and two morphotypes.

Repurposing miconazole and tamoxifen for the treatment of Mycobacterium abscessuscomplex infections through in silicochemogenomics approach.

Drug repositioning is an alternative to overcome the complexity of the drug discovery and approval procedures for the treatment of Mycobacterium abscessus Complex (MABSC) infections that are increasing globally due to the emergency of antimicrobial resistance mechanisms. Here, an in silico chemogenomics approach was performed to compare the sequences from 4942M. abscessus subsp. abscessus (M. abscessus) proteins with 5258 or 3473 therapeutic targets registered in the DrugBank or Therapeutic Target Database, respectively. This comparison identified 446 drugs or drug candidates whose targets were homologous to M. abscessus proteins. These identified drugs were considered potential inhibitors of MABSC (anti-MABSC activity). Further screening and inspection resulted in the selection of ezetimibe, furosemide, itraconazole, miconazole (MCZ), tamoxifen (TAM), and thiabendazole (THI) for experimental validation. Among them, MCZ and TAM showed minimum inhibitory concentrations (MIC) of 32 and 24µg mL-1 against M. abscessus, respectively. For M. bolletii and M. massiliense strains, MCZ and TAM showed MICs of 16 and 24µg mL-1, in this order. Subsequently, the antibacterial activity of MCZ was confirmed in vivo, indicating its potential to reduce the bacterial load in the lungs of infected mice. These results show that MCZ and TAM can serve as molecular scaffolds for the prospective hit-2-lead optimization of new analogs with greater potency, selectivity, and permeability.

Epidemiology, management, and clinical outcomes of extrapulmonary Mycobacterium abscessus complex infections in heart transplant and ventricular assist device recipients

Nontuberculous mycobacteria are emerging pathogens, yet data on the epidemiology and management of extrapulmonary nontuberculous mycobacteria infections in orthotopic heart transplantation (OHT) and ventricular assist device (VAD) recipients are scarce. We retrospectively reviewed records of OHT and VAD recipients who underwent cardiac surgery at our hospital and developed Mycobacterium abscessus complex (MABC) infection from 2013 to 2016 during a hospital outbreak of MABC linked to heater-cooler units. We analyzed patient characteristics, medical and surgical management, and long-term outcomes. Ten OHT patients and 7 patients with VAD developed extrapulmonary M. abscessus subspecies abscessus infection. The median time from presumed inoculation during cardiac surgery to the first positive culture was 106 days in OHT and 29 days in VAD recipients. The most common sites of positive cultures were blood (n = 12), sternum/mediastinum (n = 8), and the VAD driveline exit site (n = 7). The 14 patients diagnosed when alive received combination antimicrobial therapy for a median of 21 weeks, developed 28 antibiotic-related adverse events, and underwent 27 surgeries. Only 8 (47%) patients survived longer than 12 weeks after diagnosis, including 2 patients with VAD who experienced long-term survival after an explantation of infected VADs and OHT. Despite aggressive medical and surgical management, OHT and VAD patients with MABC infection experienced substantial morbidity and mortality.

Epidemiological trends in nontuberculous mycobacterial infection among people with cystic fibrosis in Germany

ObjectivesPeople with cystic fibrosis (pwCF) are at risk for infection with nontuberculous mycobacteria (NTM). The epidemiology and screening practice of NTM among pwCF in Germany are largely unknown and require investigation. MethodsWe analyzed the data of the German Cystic Fibrosis Registry from 2016 to 2020 for NTM. The annual prevalence and incidence of any NTM, Mycobacterium abscessus complex (MABC), Mycobacterium avium complex (MAC), Mycobacterium gordonae, and other mycobacteria were determined and correlated to patient characteristics. Patients with incident MABC and MAC infection were compared. ResultsThe annual NTM prevalence and incidence remained stable between 7.53% and 8.76%, as well as 3.31% and 4.95%, respectively, among the approximately 6000 registry participants. MABC was the most common NTM, whereas only the prevalence of MAC increased slightly. In each year, only about one-third of all patients were screened for NTM. An association between NTM infections and Aspergillus fumigatus infection and/or allergic bronchopulmonary aspergillosis was observed. On average, patients with incident MAC infection were older than patients with MABC infection. ConclusionThe NTM burden in pwCF in Germany remained unchanged between 2016 and 2020. MABC was the dominant species detected, whereas only MAC infections increased with time and patient age. The previously observed association of Aspergillus fumigatus and NTM was reaffirmed. Awareness of NTM needs to be improved.

Use of Statistical Process Control Methods for Early Detection of Healthcare Facility-Associated Nontuberculous Mycobacteria Outbreaks: A Single-Center Pilot Study.

Nontuberculous mycobacteria (NTM) are emerging pathogens increasingly implicated in healthcare facility-associated (HCFA) infections and outbreaks. We analyzed the performance of statistical process control (SPC) methods in detecting HCFA NTM outbreaks. We retrospectively analyzed 3 NTM outbreaks that occurred from 2013 to 2016 at a tertiary care hospital. The outbreaks consisted of pulmonary Mycobacterium abscessus complex (MABC) acquisition, cardiac surgery-associated extrapulmonary MABC infection, and a bronchoscopy-associated pseudo-outbreak of Mycobacterium avium complex (MAC). We analyzed monthly case rates of unique patients who had positive respiratory cultures for MABC, non-respiratory cultures for MABC, and bronchoalveolar lavage cultures for MAC, respectively. For each outbreak, we used these rates to construct a pilot moving average (MA) SPC chart with a rolling baseline window. We also explored the performance of numerous alternative control charts, including exponentially weighted MA, Shewhart, and cumulative sum charts. The pilot MA chart detected each outbreak within 2 months of outbreak onset, preceding actual outbreak detection by an average of 6 months. Over a combined 117 months of pre-outbreak and post-outbreak surveillance, no false-positive SPC signals occurred (specificity, 100%). Prospective use of this chart for NTM surveillance could have prevented an estimated 108 cases of NTM. Six high-performing alternative charts detected all outbreaks during the month of onset, with specificities ranging from 85.7% to 94.9%. SPC methods have potential to substantially improve HCFA NTM surveillance, promoting early outbreak detection and prevention of NTM infections. Additional study is needed to determine the best application of SPC for prospective HCFA NTM surveillance in other settings.

Radiological findings in nontuberculous mycobacterial pulmonary diseases: A comparison between the Mycobacterium avium complex and the Mycobacterium abscessus complex.

The Mycobacterium abscessus complex (MABC) comprises rapidly growing mycobacteria and has received increasing attention recently, with an increasing number of associated infections reported worldwide. However, the clinical features of MABC pulmonary disease (MABC-PD), especially in terms of the chest computed tomography (CT) findings, are not fully understood. Thus, this retrospective, cross-sectional study aimed to evaluate the clinical background and chest high-resolution CT (HRCT) findings of MABC-PD in comparison with those of Mycobacterium avium complex PD (MAC-PD). Accordingly, 36 patients with MABC-PD and 65 patients with MAC-PD (defined according to the American Thoracic Society criteria), who were newly diagnosed at four major hospitals in Okinawa (Japan) between January 2012 and December 2017, were analyzed. With respect to their clinical background, only cardiovascular diseases were significantly more common in patients with MABC-PD than in those with MAC-PD (38.9% vs. 18.5%, p = 0.0245). HRCT revealed a significantly higher incidence of low attenuation in patients with MABC-PD than in those with MAC-PD (63.9% vs. 10.8%, p<0.0001). On analyzing only never-smokers (20 and 47 patients with MABC-PD and MAC-PD, respectively), this significant difference remained (65.0% vs. 8.5%, p<0.0001), suggesting MABC infection itself caused low attenuation. In terms of the distribution of abnormal shadows, the involvement of the right lower, left upper, and left lower lobes was more common in patients with MABC-PD than in those with MAC-PD. Furthermore, the mean number of involved lung lobes was significantly higher in patients with MABC-PD than in those with MAC-PD (5.6 vs. 4.7, p<0.001). Although further studies are needed, we assume that the aforementioned radiological features of MABC-PD are due to the high virulence of MABC.

Multiresistant organisms: bacteria and beyond

Infections with multiresistant organisms are an emerging problem, cause early mortality post lung transplantation and are sometimes associated with graft dysfunction. Frequently they raise questions about the selection of lung transplant candidates and therapeutic management post lung transplantation. There are no guidelines and management must be individualized. This review summarizes the available therapeutic options in cases of multidrug-resistant (MDR) organisms and outcomes after lung transplant. Improvements in diagnosis, new and more effective drugs and the experience gained in the management of these infections in lung transplantation, lead to a more optimistic horizon than that found a decade ago. Update on the management of Burkholderia cepacia complex, Mycobacterium abscessus complex, Aspergillus spp., Scedosporium spp. and Lomentospora prolificans infections. This review clarifies current posttransplant outcomes and adds a little hope in these scenarios.

Rapid Detection of Clarithromycin and Amikacin Resistance in Mycobacterium abscessus Complex by High-Resolution Melting Curve Analysis.

ABSTRACTThe emergence of Mycobacterium abscessus complex (MABC) infection is the most noteworthy health care problem. Clarithromycin (CLA) and amikacin (AMK) constitute the cornerstone of treatment for patients infected with MABC; thus, early detection of resistance to these two drugs is essential for formulating effective therapeutic regimens. In the present study, we aimed to validate the use of MeltPro MAB assay, a melting curve analysis with dually labeled probes, on a set of clinical isolates to detect CLA and AMK resistance. A total of 103 clinical MABC strains were collected in our analysis, including 76 strains of M. abscessus subsp. Abscessus (MAA) and 27 strains of M. abscessus subsp. Massiliense (MAM). In vitro susceptibility testing revealed that two isolates exhibited intrinsic CLA resistance by harboring A2270T mutation in rrl, and inducible resistance was noted in 42 isolates. Additionally, two MAA isolates with erm(41)T28 genotype were susceptible to CLA. Notably, we found three out of 44 isolates had two melting curve peaks, representing the simultaneous presence of mutant and the wild type in these specimens. In contrast, no known mutations were identified in six AMK-resistant isolates. Further analysis revealed that MeltPro yielded 100% and 96.67% sensitivity and specificity for detecting CLA resistance. In summary, this study firstly demonstrates that MeltPro is a promising diagnostic for early detection of CLA resistance for MABC isolates, which significantly improves the turnaround time within 2 h. Approximate two fifths of MABC isolates are resistant to CLA by 23S rRNA mutation or its methylation, emphasizing the urgent need for early detection of CLA resistance prior to empirical treatment of MABC infections.IMPORTANCE Mycobacterium abscessus complex (MABC) has attracted increasing attention due to the numerous cases of infection. This pathogen is notorious for its intrinsic drug resistance, which complicates clinical management of patients with MABC infections. Clarithromycin (CLA) and amikacin (AMK) are the cornerstone of treatment regimens for MABC. Herein, our data firstly demonstrates that MeltPro is a promising diagnostic for early detection of CLA resistance for MABC isolates. The high frequency of CLA-resistant MABC isolates in China emphasizes the urgent need for early detection of CLA resistance prior to empirical treatment of MABC infections.

Growth medium and nitric oxide alter Mycobacterium abscessus morphotype and virulence

Mycobacterium abscessus complex (MABC) infections cause significant morbidity and mortality among patients with chronic lung disease, like cystic fibrosis. MABC exists in smooth (S) and rough (R) morphotypes, but triggers of morphotype switching and associated pathogenicity or antimicrobial susceptibility are poorly understood. We demonstrate that M. abscessus subspecies abscessus (Mab), massiliense (Mms), and bolletii (Mbl) cultured in Middlebrook (MB) broth exhibit S morphotype, whereas the bacteria grown in Luria Bertani (LB) broth adopt the R morphotype, characterized by low glycopeptidolipid (GPL) expression. The components of broth that mediate this selection are complex, with albumin supplementation promoting growth of S morphotype, but not sufficient for complete selection. Consistent with the findings of other groups, R forms of Mab, Mms and Mbl selected by LB broth were internalized in RAW 264.7 macrophages with higher efficiency than S. Intracellular survival of broth-selected organisms was variable and was higher for S Mab, but lower for S Mms and Mbl. It is proposed that growth in R morphotype is induced during stress conditions, such as nutrient poor environments or during inflammation. One key component of inflammation is release of nitric oxide. We demonstrated that a nitric oxide donor (DETA-NONOate) appears to induce growth in an R morphotype, as indicated by reduced GPL expression of Mab. Mab treated with DETA-NONOate also enhanced susceptibility to azithromycin at sub-MIC concentrations. In conclusion, morphotype and macrophage intracellular bacterial load of MABC subspecies can be manipulated by growing the bacteria in different culture conditions. Nitric oxide may also drive morphotype selection and enhanced azithromycin activity against Mab and macrophage killing.

Increased Virulence of Outer Membrane Porin Mutants of Mycobacterium abscessus.

Chronic pulmonary infections caused by non-tuberculous mycobacteria of the Mycobacterium abscessus complex (MABSC) are emerging as a global health problem and pose a threat to susceptible individuals with structural lung disease such as cystic fibrosis. The molecular mechanisms underlying the pathogenicity and intrinsic resistance of MABSC to antibiotics remain largely unknown. The involvement of Msp-type porins in the virulence and biocide resistance of some rapidly growing non-tuberculous mycobacteria and the finding of deletions and rearrangements in the porin genes of serially collected MABSC isolates from cystic fibrosis patients prompted us to investigate the contribution of these major surface proteins to MABSC infection. Inactivation by allelic replacement of the each of the two Msp-type porin genes of M. abscessus subsp. massiliense CIP108297, mmpA and mmpB, led to a marked increase in the virulence and pathogenicity of both mutants in murine macrophages and infected mice. Neither of the mutants were found to be significantly more resistant to antibiotics. These results suggest that adaptation to the host environment rather than antibiotic pressure is the key driver of the emergence of porin mutants during infection.

Species-Specific Interferon-Gamma Release Assay for the Diagnosis of Mycobacterium abscessus Complex Infection.

Mycobacterium abscessus complex (MABC) infection has a devastating impact on the course of cystic fibrosis (CF) and non-CF lung disease. Diagnosis of MABC pulmonary disease is challenging, and current diagnostic approaches lack accuracy, especially in CF. In this study, we aimed to establish an MABC-specific interferon-γ release assay to detect host immune responses to MABC and improve diagnostics of MABC infection by the detection of antigen-specific T cells. Four species-specific proteins of MABC were overexpressed in an Escherichia coli expression system. Purified proteins were used to stimulate peripheral blood mononuclear cells of study subjects in an ELISpot assay. Interferon-γ response of 12 subjects with established diagnosis of MABC infection (10 CF and two non-CF) was compared with 35 controls (22 CF and 13 non-CF) distributed to three control groups, 17 CF subjects without NTM infection, nine subjects with NTM infection other than MABC, and nine subjects with tuberculosis. Cellular in vitro responses in the MABC group were stronger than in the control groups, especially toward the protein MAB_0405c (39 vs. 4 spots per 300,000 PBMC, p = 0.004; data represent mean values) in all patients and also in the subgroup of CF subjects (39 spots vs. 1 spot, p = 0.003). Receiver operating characteristic curve analysis indicated that spot numbers of at least 20 were highly predictive of MABC infection (all patients: area under curve 0.773, sensitivity 58%, and specificity 94%; CF patients: area under curve 0.818, sensitivity 60%, and specificity 100%). In conclusion, we identified MAB_0405c as a protein that may stimulate MABC-specific interferon-γ secretion and may add to the diagnosis of MABC infection in affected patients.

Antimicrobial susceptibility profiles of Mycobacterium abscessus complex isolates from respiratory specimens in Shanghai, China

ObjectivesThe aim of this study was to compare the antibiotic susceptibility profiles of Mycobacterium abscessus complex (MABC) isolates and to investigate the relationship between susceptibility profiles and genetic mechanisms of macrolide resistance. MethodsMore than 200 isolates collected from respiratory specimens between 2014 and 2018 were randomly analysed in this study. Minimum inhibitory concentrations (Mics) of ten potential antimicrobial agents were determined by the microplate alamarBlue assay. ResultsWe identified 43 MABC isolates, including 32 M. abscessus subsp. abscessus (M. abscessus) (6 from immunocompromised patients) and 11 M. abscessus subsp. massiliense (M. massiliense). The majority of MABC isolates were susceptible to amikacin (96.9% and 100.0% for M. abscessus and M. massiliense, respectively), linezolid (96.9% and 100.0%, respectively), cefoxitin (100.0% and 100.0%, respectively), imipenem (90.6% and 72.7%, respectively) and tobramycin (90.6% and 72.7%, respectively). The resistance rates to clarithromycin and doxycycline in isolates of M. abscessus (68.8% and 100.0%) were significantly higher than those in isolates of M. massiliense (18.2% and 63.6%) (P < 0.05), whereas the percentage of tobramycin-resistant isolates among M. abscessus (9.4%) was significantly lower than among M. massiliense (27.3%) (P = 0.007). Sequencing analyses showed significant differences between erm(41) of M. abscessus and M. massiliense. ConclusionMycobacterium abscessus is the dominant pathogen of pulmonary MABC infections in our hospital. Aminoglycosides (amikacin and tobramycin), β-lactams (cefoxitin and imipenem) and linezolid exhibited potent inhibitory activity against MABC in vitro. The erm(41) gene may be a promising marker to predict macrolide susceptibility for M. abscessus.

Differential In Vitro Activities of Individual Drugs and Bedaquiline-Rifabutin Combinations against Actively Multiplying and Nutrient-Starved Mycobacterium abscessus.

Current treatment options for lung disease caused by Mycobacterium abscessus complex infections have limited effectiveness. To maximize the use of existing antibacterials and to help inform regimen design for treatment, we assessed the in vitro bactericidal activity of single drugs against actively multiplying and net nonreplicating M. abscessus populations in nutrient-rich and nutrient-starvation conditions, respectively. As single drugs, bedaquiline and rifabutin exerted bactericidal activity only against nutrient-starved and actively growing M. abscessus, respectively. However, when combined, both bedaquiline and rifabutin were able to specifically contribute bactericidal activity at relatively low, clinically relevant concentrations against both replicating and nonreplicating bacterial populations. The addition of a third drug, amikacin, further enhanced the bactericidal activity of the bedaquiline-rifabutin combination against nutrient-starved M. abscessus Overall, these in vitro data suggest that bedaquiline-rifabutin may be a potent backbone combination to support novel treatment regimens for M. abscessus infections. This rich data set of differential time- and concentration-dependent activity of drugs, alone and together, against M. abscessus also highlights several issues affecting interpretation and translation of in vitro findings.

Adaptive Immune Response to &lt;i&gt;Mycobacterium abscessus&lt;/i&gt; Complex and Cross-Reactivity of BCG Vaccination

Background: Mycobacterium abscessus complex (MABSC) is a major pathogenic group among nontuberculous mycobacteria (NTM). Here we characterized the adaptive immune response to MABSC and its cross reactivity with Mycobacterium bovis (Bacille Calmette-Guerin, BCG) using cystic fibrosis (CF) lung infection as a model. Methods: This was a cross-sectional study enrolling CF patients with and without history of NTM infection (CF/NTM+ and CF/NTM-), non-CF controls vaccinated and not vaccinated with BCG (C/BCG+ and C/BCG-). The anti-MABSC response was assessed in terms of lymphocyte activity and cytokine production after challenge with MABSC, and measurement of specific IgG. Results: The CF/NTM+ and C/BCG+ groups had cellular and cytokine responses with similar intensity, characterized by a Th1-dominated phenotype – high CD4 T-cell proliferation, increased IFN-γ and TNF-α production. The B-cell response and its associated cytokines CD40L and IL-4 were less pronounced, although IgG levels were higher in the CF/NTM+ group than in controls. Proliferating lymphocytes, increased IFN-γ and TNF-α production were also observed in part of the individuals of the CF/NTM- and C/BCG- groups, indicating environmental exposure, undetected or past infection. IL-2 increased only in the CF groups and may be specifically linked to the anti-MABSC response. Altogether, BCG-vaccinated individuals (CF and non-CF) had higher lymphocyte proliferation intensity than the non-vaccinated ones. Conclusion: The anti-MABSC response follows a pattern seen in other mycobacterial infections. BCG vaccination provides a cross-reactive response against MABSC and can have potential to mitigate the pathology of NTM infections. The potential of cytokine measurement for diagnosing MABSC infection is under investigation. Funding Information: RMM was granted a fellowship by the Sao Paulo Research Foundation (FAPESP, grant reference #2019/14134-5) and the study received funds from the Cystisk Fibrose Foreningen (Danish Cystic Fibrosis Association). Declaration of Interests: The authors have no conflicts of interests to declare. Ethics Approval Statement: The study was approved by the Regional Scientific Ethical Committees, Denmark (VEK, RH-19022288) and was in accordance with the Declaration of Helsinki and guidelines from the Danish Data Protection Agency. All participants signed a written informed consent, confirming their voluntary participations.

877. Use of Statistical Process Control Charts for Early Detection of Healthcare Facility-Associated Nontuberculous Mycobacterial Outbreaks

BackgroundNontuberculous mycobacteria (NTM) are increasingly implicated in healthcare facility-associated (HCFA) outbreaks. However, systematic methods for NTM surveillance and outbreak detection are lacking and represent an emerging need. We examined how statistical process control (SPC) might perform in NTM outbreak detection.MethodsSPC charts were optimized for surgical site infection surveillance and adapted to analyze 3 NTM outbreaks that occurred from 2013-2016 at a single hospital. The first 2 outbreaks occurred contemporaneously and consisted of pulmonary Mycobacterium abscessus complex (MABC) acquisition and cardiac surgery-associated extrapulmonary MABC infection, respectively. The third outbreak was a pseudo-outbreak of Mycobacterium avium complex (MAC) at a bronchoscopy suite.We retrospectively analyzed monthly rates of unique patients who had: 1) positive respiratory cultures for MABC obtained on hospital day 3 or later; 2) positive non-respiratory cultures for MABC; and 3) positive bronchoalveolar lavage (BAL) cultures for MAC collected at the bronchoscopy suite. For each outbreak, we used these rates to construct a standardized moving average (MA) SPC chart with MA span of 3 months. Rolling baselines were estimated from average rates for months 7 through 12 prior to each monthly data point. SPC detection was indicated by the first data point above the upper control limit (UCL) of 3 standard deviations. Traditional surveillance detection was defined as the time of outbreak detection by routine infection control procedures.ResultsSPC detection occurred 5, 4, and 9 months prior to traditional surveillance outbreak detection for the three outbreaks, respectively (Figures 1 and 2). Prospective NTM surveillance using the MA chart potentially would have prevented an estimated 19 cases of pulmonary MABC, 9 cases of extrapulmonary MABC, and 80 cases of BAL MAC isolation (Table). No data points exceeded the UCL during 95 cumulative months of post-outbreak surveillance, suggesting low burden of false positive SPC signals.Figure 1. Use of a moving average statistical process control (SPC) chart for early detection of hospital-associated outbreaks of pulmonary Mycobacterium abscessus complex (MABC) and cardiac surgery-associated extrapulmonary MABC infection. The pulmonary chart analyzes cases of hospital-onset respiratory isolation of MABC. The extrapulmonary chart analyzes cases of positive non-respiratory cultures for MABC. CL, center line; LCL, lower control limit; UCL, upper control limit. Figure 2. Use of a moving average statistical process control (SPC) chart for early detection of a pseudo-outbreak of Mycobacterium avium complex (MAC) that occurred at a bronchoscopy suite. The chart analyzes cases of MAC isolated from bronchoalveolar lavage cultures. CL, center line; LCL, lower control limit; UCL, upper control limit. Table. Estimated cases of hospital-associated nontuberculous mycobacteria that would have been prevented by prospective surveillance with a moving average statistical process control (SPC) chart. ConclusionA single MA SPC chart detected 3 HCFA NTM outbreaks an average of 6 months earlier than traditional surveillance. SPC has potential to improve NTM surveillance, promoting early cluster detection and prevention of HCFA NTM.Disclosures All Authors: No reported disclosures

Chronic suppurative otomastoiditis due to nontuberculous mycobacteria: A case series

IntroductionEight new cases of chronic otomastoiditis due to nontuberculous mycobacteria were reported at Center Hospitalier Universitaire Sainte-Justine (CHUSJ) between 2008 and 2018. In the literature, only 89 cases have been described since 1972. This case series aims to define the clinical presentation, infectious pathogens, as well as diagnostic and therapeutic means employed in cases of nontuberculous mycobacteria otitis media encountered in our tertiary pediatric reference center. MethodsAll cases of otitis media caused by nontuberculous mycobacteria diagnosed at Sainte-Justine between 2008 and 2018 were reviewed. Species identification was retrieved from the Laboratoire de Santé Publique du Québec, Quebec's provincial public health and reference laboratory. ResultsAll 8 cases occurred in immunocompetent children. Clinical features on presentation were chronic tympanostomy tube otorrhea with abundant granulation tissue in 7 cases. CT scan demonstrated coalescent mastoiditis in 3 cases. The median delay between initial presentation and identification of nontuberculous mycobacteria was 81 days. Seven patients had a Mycobacterium (M.) abscessus complex infection. Treatment consisted of weekly microscopic granulation debridement, a combined systemic antibiotic therapy for an average duration of 21 weeks, as well as instillation of boric acid into the middle ear. While 3 cases required at least one mastoidectomy, 2 cases were treated only medically. ConclusionNontuberculous mycobacteria otitis media is a rare clinical entity, for which high clinical suspicion and specific microbiological analyses could minimize diagnostic delay. The use of boric acid as a desiccating agent may allow for a better local control.

Invasive Mycobacterium abscessus Complex Infection After Cardiac Surgery: Epidemiology, Management, and Clinical Outcomes.

We recently mitigated a clonal outbreak of hospital-acquired Mycobacterium abscessus complex (MABC), which included a large cluster of adult patients who developed invasive infection after exposure to heater-cooler units during cardiac surgery. Recent studies have detailed Mycobacterium chimaera infections acquired during cardiac surgery; however, little is known about the epidemiology and clinical courses of cardiac surgery patients with invasive MABC infection. We retrospectively collected clinical data on all patients who underwent cardiac surgery at our hospital and subsequently had positive cultures for MABC from 2013 through 2016. Patients with ventricular assist devices or heart transplants were excluded. We analyzed patient characteristics, antimicrobial therapy, surgical interventions, and clinical outcomes. Ten cardiac surgery patients developed invasive, extrapulmonary infection from M. abscessus subspecies abscessus in an outbreak setting. Median time from presumed inoculation in the operating room to first positive culture was 53 days (interquartile range [IQR], 38-139 days). Disseminated infection was common, and the most frequent culture-positive sites were mediastinum (n = 7) and blood (n = 7). Patients received a median of 24 weeks (IQR, 5-33 weeks) of combination antimicrobial therapy that included multiple intravenous agents. Six patients required antibiotic changes due to adverse events attributed to amikacin, linezolid, or tigecycline. Eight patients underwent surgical management, and 6 patients required multiple sternal debridements. Eight patients died within 2 years of diagnosis, including 4 deaths directly attributable to MABC infection. Despite aggressive medical and surgical management, invasive MABC infection after cardiac surgery caused substantial morbidity and mortality. New treatment strategies are needed, and compliance with infection prevention guidelines remains critical.