Mycobacterium Abscessus Group Research Articles

P-798. Non-Tuberculosis Mycobacterial Infections at a National Cancer Institute-Designated Comprehensive Cancer Center in Florida

Abstract Background Non-tuberculous mycobacteria (NTM) are environmental organisms which become opportunistic pathogens in certain patient populations. NTM prevalence has increased globally, thought to be due to the increased diagnostic testing and availability of population-based studies. This is especially true in Florida, where we have previously documented more cases of Mycobacterium abscessus group compared to M. avium Complex (MAC) group. Current literature of NTM infections in oncology patients is minimal and represents a unique area for study. Here we present our epidemiological and clinical presentation of NTM infection cases at a National Cancer Institute-designated comprehensive cancer center.Figure 1.Patient Characteristics Methods Retrospective, Institutional Review Board-approved, single-center cohort study, of adult patients with microbiologically proven NTM infections who presented from 2020 to 2023. Demographic, laboratory, and susceptibility data were retrieved from the electronic medical record system and evaluated to show institutional patterns.Figure 2.Microbiological Characteristics for Overall Population Results Ninety-three cases of NTM infection met assessment criteria. Baseline characteristics are shown in Figure 1. A large proportion were female (71%) and white (90%). Many had a past or active cancer (80%), with skin (23%), lung (22%), and breast (13%) most prevalent. MAC (52%) and M. abscessus group (31%) were the most common NTM isolates (Figure 2). The majority were pulmonary infections (81%), with the integument accounting for most non-pulmonary sites (78%). Positive cultures were most frequently obtained via bronchoalveolar lavage (62%) followed by sputum (13%). Figure 3 offers insight into infection/culture site and cancer type stratified by organism, while susceptibility patterns are summarized in Figure 4.Figure 3.Site of Infection/Culture and Type of Cancer Stratified by Organism Conclusion NTM infections at our institution were primarily caused by MAC or M. abscessus group and were typically pulmonary in nature, isolated via bronchoalveolar lavage. Most occurred in patients with a solid tumor malignancy. Further research is needed to delineate prevalence patterns, microbiological characteristics, and treatment approaches of NTM infections in our site’s population. Susceptibility by Organism Disclosures All Authors: No reported disclosures

Long-term Outcomes of Adjunctive Lung Resection for Nontuberculous Mycobacteria Pulmonary Disease.

Adjunctive lung resection is recommended for select patients with nontuberculous mycobacteria (NTM) pulmonary disease (PD). However, data are limited on long-term recurrence rates in patients infected with major pathogens, including Mycobacterium avium complex (MAC) and Mycobacterium abscessus (MABC). In this prospective observational study, we retrospectively analyzed data from 125 patients with MAC-PD (n = 90) or MABC-PD (n = 35) who underwent adjunctive lung resection. We evaluated microbiological response, postoperative complications, recurrence, and all-cause mortality over a median 80-month follow-up. Persistent culture positivity (64%) was the most common indication for surgery, followed by hemoptysis, recurrent pneumonia, or radiologic deterioration. Postoperative complications occurred in 18 (14%) patients, with no surgery-related deaths. Treatment outcomes did not significantly differ between the MAC- and MABC-PD groups. Cure with culture conversion was achieved in 112 (90%) patients. Recurrence occurred in 37 (33%) of 112 patients, of which 18 (49%) cases were attributed to reinfection by different NTM species or subspecies. The MAC group had higher recurrence rates than the MABC group (Kaplan-Meier curve, log-rank test, P = .043) and was significantly associated with recurrence in the multivariable analysis (adjusted hazard ratio, 2.71; 95% CI, 1.23-5.99). However, mortality was higher in the MABC-PD group than the MAC-PD group (7/35 vs 4/90, P = .006). Adjunctive lung resection with antibiotics helps to reduce bacterial burden and manage symptoms in patients with NTM-PD. However, it does not prevent recurrence, which is mostly caused by reinfection.

Clinically relevant mutations in the PhoR sensor kinase of host-adapted Mycobacterium abscessus isolates impact response to acidic pH and virulence.

Difficult-to-treat pulmonary infections caused by nontuberculous mycobacteria of the Mycobacterium abscessus group have been steadily increasing in the USA and globally. Owing to the relatively recent recognition of M. abscessus as a human pathogen, basic and translational research to address critical gaps in diagnosis, treatment, and prevention of diseases caused by this microorganism has been lagging behind that of the better-known mycobacterial pathogen, Mycobacterium tuberculosis. To begin unraveling the molecular mechanisms of pathogenicity of M. abscessus, we here focus on the study of a two-component regulator known as PhoPR which we found to be under strong evolutionary pressure during human lung infection. We show that PhoPR is activated at acidic pH and serves to regulate a defined set of genes involved in host adaptation. Accordingly, clinical isolates from chronically infected human lungs tend to hyperactivate this regulator enabling M. abscessus to escape macrophage killing.

Antimicrobial Susceptibility Distributions of Clinical Isolates of Nontuberculous Mycobacteria in Israel.

There is a scarcity of data regarding the antimicrobial susceptibility testing profiles of nontuberculous mycobacterial (NTM) in Israel and other Middle Eastern countries. We aimed to describe the antimicrobial susceptibility profiles of NTM in Israel. A total of 410 clinical isolates of NTM, identified to the species level using matrix-assisted laser desorption ionization-time of flight mass spectrometry or hsp65 gene sequencing, were included. Minimum inhibitory concentrations for slowly growing mycobacteria (SGM) and rapidly growing mycobacteria (RGM) for 12 and 11 drugs were determined using the Sensititre SLOMYCOI and RAPMYCOI broth microdilution plates, respectively. Mycobacterium avium complex (MAC) was the most frequently isolated species (n = 148; 36%), followed by Mycobacterium simiae (n = 93; 23%), Mycobacterium abscessus group (n = 62; 15%), Mycobacterium kansasii (n = 27; 7%), and Mycobacterium fortuitum (n = 22; 5%) accounting together for 86% of isolates. The most active agents against SGM were amikacin (98%/85%/100%) and clarithromycin (97%/99%/100%), followed by moxifloxacin (25%/10%/100%) and linezolid (3%/6%/100%) for MAC, M. simiae, and M. kansasii, respectively. For RGM, the most active agents were amikacin (98%/100%/88%) followed by linezolid (48%/80%/100%) and clarithromycin (39%/28%/94%) for M. abscessus group, M. fortuitum, and M. chelonae, respectively. These findings can assist in guiding the treatment of NTM infections.

Development of multiplex real-time PCR for detection of clarithromycin resistance genes for the Mycobacterium abscessus group.

Introduction. The M. abscessus molecular identification and its drug-resistance profile are important to choose the correct therapy.Aim. This work developed a multiplex real-time PCR (mqPCR) for detection of clarithromycin resistance genes for the Mycobacterium abscessus group.Methodology. Isolates received by Adolfo Lutz Institute from 2010 to 2012, identified by PCR restriction enzyme analysis of a fragment of the hsp65 gene (PRA-hsp65) as M. abscessus type 1 (n=135) and 2 (n=71) were used. Drug susceptibility test (DST) for CLA were performed with reading on days 3 and 14. Subespecies identification by hsp65 and rpoB genes sequencing and erm(41) and rrl genes for mutation detection and primer design were performed. erm(41) gene deletion was detected by conventional PCR. Primers and probes were designed for five detections: erm(41) gene full size and with deletion; erm(41) gene T28 and C28; rrl gene A2058.Results. In total, 191/206 (92.7 %) isolates were concordant by all methods and 13/206 (6.3 %) were concordant only between molecular methods. Two isolates (1.0 %) were discordant by mqPCR compared to rrl gene sequencing. The mqPCR obtained 204/206 (99.0 %) isolates in agreement with the gold standard, with sensitivity and specificity of 98 and 100 %, respectively, considering the gold standard method and 92 and 93 % regarding DST.Conclusion. The mqPCR developed by us proved to be an easy-to-apply tool, minimizing time, errors and contamination.

Cumulative antimicrobial susceptibilities for respiratory clinical isolates of Mycobacterium avium Complex, Mycobacterium kansasii, and Mycobacterium abscessus from Pakistan 2018 to 2022.

Nontuberculous mycobacteria (NTM) are increasingly identified as causes of protracted pulmonary infections. Antibiotic susceptibility testing requires microdilution methods, which are often unavailable in laboratories in resource-poor settings. We report cumulative antibiograms for the most frequently isolated clinical pulmonary NTM from Pakistan to inform empiric antibiotic management of initial NTM infections. We analyzed data from 2018 to 2022 for the most frequently isolated and clinically relevant NTM isolated from respiratory specimens, i.e., Mycobacterium avium complex (MAC), Mycobacterium abscessus group (MAG), and Mycobacterium kansasii (MK). Antibiograms were developed using the Clinical Laboratory Standards Institute's M39ED5 standard. Percentage susceptibilities and 95% confidence intervals (CI) were calculated. Over 4 years, 529 NTM, comprising 209 MAC, 249 MAG, and 71 MK were analyzed. For MAC and MAG, where clarithromycin (CLR)-based regimens are recommended, CLR was active for 94.8% (95% CI 91.3-96.9), and 77.5% (95% CI 71.4-82.7) isolates, respectively. Combination regimens comprising 3 active drugs CLR + linezolid (LZD) + moxifloxacin for MAC and CLR + LZD + Amikacin for MAG had 98.4% (95% CI 95.9-99.4) and 68.9% (95% CI 62.3-74.8) coverage for pulmonary disease, respectively. For MK, 91.5% (95% CI 82.8-96.1) isolates were susceptible to rifampin (RIF), with a combination of RIF + CLR covering 88.7% (95% CI 79.3-94.2) of MK pulmonary infections, respectively. These data can inform empiric treatment guidance for the most common NTM pulmonary infections, i.e., for MAC, MAG, and MK disease in Pakistan.

Quantifying the effectiveness of ultraviolet-C light at inactivating airborne Mycobacterium abscessus

Mycobacterium abscessus (MABS) group are environmental organisms that can cause infection in people with cystic fibrosis (CF) and other suppurative lung diseases. There is potential for person-to-person airborne transmission of MABS among people with CF attending the same care centre. Ultraviolet light (band C, UV-C) is used for Mycobacterium tuberculosis control indoors; however, no studies have assessed UV-C for airborne MABS. To determine whether a range of UV-C doses increased the inactivation of airborne MABS, compared with no-UVC conditions. MABS was generated by a vibrating mesh nebulizer located within a 400L rotating drum sampler, and then exposed to an array of 265nm UV-C light-emitting diodes (LED). A six-stage Andersen Cascade Impactor was used to collect aerosols. Standard microbiological protocols were used for enumerating MABS, and these quantified the effectiveness of UV-C doses (in triplicate). UV-C effectiveness was estimated using the difference between inactivation with and without UV-C. Sixteen tests were performed, with UV-C doses ranging from 276 to 1104μWs/cm2. Mean (±SD) UV-C effectiveness ranged from 47.1% (±13.4) to 83.6% (±3.3). UV-C led to significantly greater inactivation of MABS (all P-values ≤0.045) than natural decay at all doses assessed. Using an indoor model of the hospital environment, it was estimated that UV-C doses in the range studied here could be safely delivered in clinical settings where patients and staff are present. This study provides empirical in-vitro evidence that nebulized MABS are susceptible to UV-C inactivation.

Vanadium in groundwater aquifers increases the risk of MAC pulmonary infection in O'ahu, Hawai'i.

To identify whether trace metals influence the risk of NTM infection in O'ahu, Hawai'i. A population-based ecologic cohort study was conducted using NTM infection incidence data from patients enrolled at Kaiser Permanente Hawai'i during 2005-2019. We obtained sociodemographic, microbiologic, and geocoded residential data for all Kaiser Permanente Hawai'i beneficiaries. To estimate the risk of NTM pulmonary infection from exposure to groundwater constituents, we obtained groundwater data from three data sources: (1) Water Quality Portal; (2) the Hawai'i Department of Health; and (3) Brigham Young University, Department of Geological Science faculty. Data were aggregated by an aquifer and were associated with the corresponding beneficiary aquifer of residence. We used Poisson regression models with backward elimination to generate models for NTM infection risk as a function of groundwater constituents. We modeled two outcomes: Mycobacterium avium complex (MAC) species and Mycobacterium abscessus group species. For every 1-unit increase in the log concentration of vanadium in groundwater at the aquifer level, infection risk increased by 22% among MAC patients. We did not observe significant associations between water-quality constituents and infection risk among M. abscessus patients. Concentrations of vanadium in groundwater were associated with MAC pulmonary infection in O'ahu, Hawai'i. These findings provide evidence that naturally occurring trace metals influence the presence of NTM in water sources that supply municipal water systems.

Short Signature rpoB Gene Sequence to Differentiate Species in Mycobacterium abscessus Group.

ABSTRACTMycobacterium abscessus group (MAG) are rapidly growing acid-fast bacteria that consist of three closely related species: M. abscessus (Ma), M. bolletii (Mb), and M. massiliense (Mm). Differentiation of these species can be difficult but is increasingly requested owing to recent infectious outbreaks and their differential drug resistance. We developed a novel and rapid pyrosequencing method using short signature sequences (35 to 45 bp) at a hypervariable site in the rpoB gene to differentiate the three MAG species, along with M. chelonae (Mc), and M. immunogenum (Mi). This method was evaluated using 111 M. chelonae-abscessus complex (MCAC) isolates, including six reference strains. All isolates were successfully differentiated to the species level (69 Ma, four Mb, six Mm, 23 Mc, and nine Mi). The species identifications by this method had 100% agreement with Sanger sequencing as well as an in-silico rpoB typing method. This short signature sequencing (SSS) method is rapid (6 to 7 h), accurately differentiates MAG species, and is useful for informing antimicrobial therapy decision.IMPORTANCE Mycobacterium abscessus group (MAG) are rapidly growing acid-fast bacteria that include three species: M. abscessus, M. massiliense, and M. bolletii. These species are among the leading causes of nontuberculosis mycobacteria infections in humans but difficult to differentiate using commonly used methods. The differences of drug resistance among the species shape the treatment regimens and make it significant for them to be differentiated accurately and quickly. We developed and evaluated a novel short signature sequencing (SSS) method utilizing a gene called rpoB to differentiate the three MAG species, as well as other two species (M. chelonae and M. immunogenum). The identification results had 100% agreement with both the reference method of Sanger sequencing and rpoB typing method via a computer-simulated analysis. This SSS method was accurate and quick (6 to 7 h) for species differentiation, which will benefit patient care. The technology used for this method is affordable and easy to operate.

Case report of a near-fatal case of Mycobacterium massiliense sepsis after de-clotting of an arteriovenous fistula

BackgroundMycobacterium massiliense is a rapidly growing a non-tuberculous mycobacterium that has been validated as a separate species from the Mycobacterium abscessus group. Only few antibiotics have demonstrated germicidal activity against Mycobacterium massiliense, and some of those include amikacin, clarithromycin, and cefoxitin.Case presentationWe present the first reported case of near-fatal septic shock caused by disseminated Mycobacterium massiliense after de-clotting of an infected arteriovenous fistula, in a patient with end-stage renal disease with concomitant human immunodeficiency virus infection. Early recognition of the culprit organism and treatment with a combination therapy of clarithromycin and amikacin led to rapid improvement.ConclusionThis unique case can highlight the importance of taking into consideration Mycobacterium massiliense infection as a cause of arteriovenous fistula thrombosis and highlights the risk of disseminated infection leading to life threatening sepsis upon de-clotting of the fistula.

Nontuberculous Mycobacteria Infection Risk and Trace Metals in Surface Water: A Population-based Ecologic Epidemiologic Study in Oregon.

Rationale: Nontuberculous mycobacteria (NTM) are ubiquitous environmental bacteria, and some pathogenic species cause lung disease. Environmental factors contribute to increased NTM abundance, with higher potential for exposure and infection. Objectives: To identify water-quality constituents that influence the risk of NTM infection in Oregon. Methods: We conducted a population-based cohort study using patient incidence data from the Oregon statewide NTM laboratory data collected as part of a public health surveillance project from 2007 through 2012. To estimate the risk of NTM pulmonary infection (PI) from exposure to water constituents, we extracted water-quality data from the Water Quality Portal and associated these data with corresponding patient county of residence. Using generalized linear models, we modeled two outcomes: Mycobacterium avium complex species PI and Mycobacterium abscessus group species PI. Results: For every 1-unit increase in the log concentration of vanadium in surface water, infection risk increased by 49% among persons with Mycobacterium avium complex PI. Among those with Mycobacterium abscessus PI, we observed that for every 1-unit increase in the log concentration of molybdenum in surface water, infection risk increased by 41%. The highest risk of infection due to Mycobacterium abscessus group infection was concentrated in counties within the Northwestern region of Oregon. High infection risk associated with Mycobacterium avium complex species did not show any geographic pattern. Conclusions: Concentrations of the trace metals molybdenum and vanadium in surface water sources were associated with NTM infection in Oregon. These findings may help identify regions at higher risk of NTM infection to guide risk reduction strategies.

Clofazimine for treatment of multidrug-resistant non-tuberculous mycobacteria

/QUESTION: Nontuberculous mycobacteria (NTM) infections are increasingly detected but difficult to cure given complex drug-resistance patterns. Select U.S. centers have incorporated clofazimine in the treatment of NTM but experience is limited as procurement restrictions hamper widespread use. A prospective cohort study was performed in patients diagnosed with pulmonary or extrapulmonary NTM infection and treated with clofazimine between February 2015 and April 2019at a tertiary referral hospital. Treatment success was defined by a combined outcome of clinical stabilization, microbiologic cure and radiologic improvement. Secondary outcomes included all-cause mortality and time to sputum culture conversion. Uni/multi-variate regression were used to define associations between pre-determined predictor variables and overall treatment outcome. Of 44 patients enrolled, 39 (89%) received clofazimine along with a median of 3 concomitant antibiotics. Thirty-one (80%) of patients had pulmonary NTM infection, with Mycobacterium abscessus group and Mycobacterium avium complex being the most common species groups identified. Of 36 people with evaluable outcomes, 35 (97%) survived and 22 (58%) had treatment success, including 12 of 19 (63%) with Mycobacterium abscessus group. In multivariate analysis, patients with Mycobacterium abscessus group were more likely to experience treatment success (OR 18.22, 95%CI 0.972-341.43, p=0.052), while macrolide resistance predicted a lack of treatment success (OR 0.053, 95%CI 0.003-0.841, p=0.037). Clofazimine was well-tolerated. Adding clofazimine to multi-class antibiotic regimens for drug-resistant NTM infection led to treatment success in the majority treated. Randomized controlled studies are needed to determine the individual impact of clofazimine within an otherwise optimized drug regimen.

Drug susceptibility patterns of rapidly growing mycobacteria isolated from skin and soft tissue infections in Venezuela.

To our knowledge, this is the first work on drug susceptibility patterns of rapid growing mycobacteria from Latin America. The susceptibility patterns for 14 antimicrobial agents of the three most important species that cause skin infections in Venezuela were determined as follows: 63 strains belonging to Mycobacterium abscessus group, 66 strains of the Mycobacterium fortuitum group, and 13 Mycobacterium chelonae strains. The M. abscessus group strains were resistant to most antibiotics tested while M. fortuitum strains were relatively susceptible to a large number of antibiotics. We demonstrate the presence of an inducible and truncated erm(41) gene in M. abscessus group, namely M. abscessus subsp. massiliense. We show the variations in susceptibility to antimicrobial agents within and between the mycobacterial species and compare our susceptibility patterns with those reported from other countries. We conclude that the identification of mycobacteria to the species level can guide the antibiotic treatment, but that it is always important to consider drug susceptibility testing when rapidly mycobacteria are isolated.

2124. The Epidemiology, Demographics, and Geographical Distribution of Human Non-Tuberculosis Mycobacteria (NTM) Disease in the Endemic Central Florida Region

BackgroundOf the >100,000 people in the United States infected yearly with non-tuberculosis mycobacteria (NTM), Florida has the highest yearly incidence and prevalence of NTM disease. However, little has been documented on the epidemiology and distribution of NTM disease within Central Florida.MethodsA retrospective case review study was conducted from January, 2011 to December, 2017 at a large tertiary acute care medical center in Tampa, Florida to identify all NTM infection cases. Demographics (age, sex at birth, ethnicity), comorbidities, HIV testing status, residential zip code, NTM species, and specimen sources were collected.ResultsOf the 507 isolates, Mycobacterium abscessus group was the most common (45.4%; n = 230), and contained M. abscessus spp. abscessus (34.5%; n = 175), M. abscessus spp. massilense (8.7%; n = 44), and M. abscessus spp. bolletii (1.18%; n = 6). Other rapid growers were M. fortuitum species (6.9%; n = 35) and M. chelonae (2.56%; n = 13). Of the slower growers, M. gordonae (19.9%; n = 101) and M. avium complex (8.28%; n = 42) were the most common. Of the M. avium complex, M. chimera was most common (4.9%; n = 25). Samples were mostly isolated from sputum (51.7%; n = 262), bronchial lavage (26%; n = 132), skin and soft tissue (11%; n = 58), and blood (7.1%; n = 36). Of the 361 unique patients, average age was 59.2 years (12 to 95 years), with 47.6% (n = 172) greater than 65 years of age, and mostly male 57.9% (n = 208). Caucasians represented 73.4% (n = 265) of our cohort, and African Americans and Hispanics represented 16.3% (n = 59) and 6.8% (n = 24), respectively. Most cases were in those residing outside the Tampa Bay metro area 81.2% (n = 293/361). Notable comorbidities included COPD (n = 83), cystic fibrosis (n = 41), lung transplant (n = 40), heart transplant (n = 12), pulmonary fibrosis (n = 12), and renal transplant (n = 7). A total of 145 individuals received HIV testing at the hospital facility, and of these 44 individuals were living with HIV.ConclusionThis study identified a diversity of NTM species across a wide geographical and demographic distribution in the endemic Central Florida region. M. abscessus group had the highest prevalence. This is valuable in understanding which populations are at risk for developing NTM infection in this area of Florida. Disclosures All authors: No reported disclosures.

P159 Factors associated with Mycobacterium abscessus group (MABS) infection type in people with cystic fibrosis

P159 Factors associated with Mycobacterium abscessus group (MABS) infection type in people with cystic fibrosis

Cutaneous nontuberculous mycobacteria infections: A retrospective case series of 78 patients from the Texas Gulf Coast region

The incidence of cutaneous nontuberculous mycobacteria (NTM) infections is increasing. These infections are a diagnostic and therapeutic challenge. We investigated the clinical features, diagnosis, and management of cutaneous NTM infections. A retrospective case series studied 78 patients from a Gulf Coast tertiary referral center diagnosed with cutaneous NTM infection by culture or stain of a skin biopsy specimen. A history of trauma, procedure, or environmental exposure was common. The mean time between the initial evaluation and diagnosis was 12weeks. Only 15% of acid-fast bacillus-positive cultures had a positive acid-fast bacillus smear, and only 43% of those accompanied by skin biopsy specimen had a positive Fite stain. Immunosuppressed patients were more likely to have a positive Fite stain. Treatment included surgery and multiple antibiotics. Immunosuppressed patients and Mycobacterium abscessus group infections were more likely to have persistent disease. M chelonae and M abscessus isolates were indistinguishable and therefore were reported together. Five cases were not confirmed by culture. Even with clinical suspicion, the diagnosis of NTM infection can be difficult. Results of acid-fast bacillus smears and special stains are frequently negative. Antibiotic resistance is common. Multidrug treatment is often required, and surgical therapy may be needed.

Tetrahydropyridine derivative as efflux inhibitor in Mycobacterium abscessus.

This study aimed to evaluate a tetrahydropyridine derivative (THP) as a potential inhibitor of the efflux mechanism and modulator of the high level of antimicrobial resistance usually observed in members of the Mycobacterium abscessus (M. abscessus) group. The strain M. abscessus subsp. abscessus (ATCC 19997) was used as reference, in addition to three clinical isolates: M. abscessus subsp. abscessus (AT 07), and two M. abscessus subsp. bolletii (AT 46 and AT 52). The minimum inhibitory concentration (MIC) of amikacin (AMI), ciprofloxacin (CIP), clarithromycin (CLA), verapamil (VP), and THP derivative (NUNL02) was determined. The NUNL02 showed activity against M. abscessus; the MIC of AMI against ATCC 19997 was reduced more than 16-fold, and the MIC of CIP against AT 52 was reduced four-fold. When combined with CLA, the MIC was reduced against all tested strains. In addition, to detect and quantify the activity of the efflux mechanism, the intracellular accumulation kinetics of the fluorometric substrate ethidium bromide in the presence and absence of VP and NUNL02 were evaluated. The NUNL02 was found to be a more effective efflux inhibitor than VP, which is the classical inhibitor. The tetrahydropyridine derivative, NUNL02, is a promising adjuvant in the treatment of infections caused by M. abscessus.

High throughput Phenotypic Microarray profiling of Mycobacterium abscessus

Mycobacterium abscessus group comprises of five species of rapidly growing mycobacteria. These mycobacteria are increasingly responsible for difficult-to treat, opportunistic cutaneous and respiratory tract infections, notably in cyctic fibrosis patients. Identification at the species level remains problematic and is relying on nucleotide sequence analyses, leaving a need for routine, phenotypic identification of such isolates. Here, the carbon and peptide nitrogen source utilization patterns of Mycobacterium abscessus complex mycobacteria was investigated using Biolog phenotype MicroArray analysis based on tetrazolium dye reduction. In a first step, a data base was built after duplicate investigation of Mycobacterium abscessus, Mycobacterium bolletii, Mycobacterium massiliense, Mycobacterium chelonae and Mycobacterium franklinii type strains. In this study, 190 carbon sources were tested; 77 (40.5%), 77 (40.5%), 77 (40.5%), 76 (40%) and 37 (19.5%) were found to be utilized by type strains of M. abscessus, M. bollettii, M. massiliense, M. chelonae and M. franklinii. Of 285 peptide nitrogen sources, they were found able to utilize 217 (76 %), 216 (75.7 %), 209 (73. 3 %), 194 (68 %) and 24 (8.4 %) nitrogen substrates, respectively. Each species yielded one specific profile, thus allowing for their unambiguous phenotypic identification at the species level. In a second step, a collection of M. abscessus, M. bolletii, M. massiliense and M. chelonae was tested to assess the usefulness of the Biolog for identification. We observed that all then identical strains were correctly identified at the species level.

Mycobacterium abscessus Complex Infections: A Retrospective Cohort Study.

BackgroundInfections caused by Mycobacterium abscessus group strains are usually resistant to multiple antimicrobials and challenging to treat worldwide. We describe the risk factors, treatment, and clinical outcomes of patients in 2 large academic medical centers in the United States.MethodsA retrospective cohort study of hospitalized adults with a positive culture for M. abscessus in Miami, Florida (January 1, 2011, to December 31, 2014). Demographics, comorbidities, the source of infection, antimicrobial susceptibilities, and clinical outcomes were analyzed. Early treatment failure was defined as death and/or infection relapse characterized either by persistent positive culture for M. abscessus within 12 weeks of treatment initiation and/or lack of radiographic improvement.ResultsOne hundred eight patients were analyzed. The mean age was 50.81 ± 21.03 years, 57 (52.8%) were females, and 41 (38%) Hispanics. Eleven (10.2%) had end-stage renal disease, 34 (31.5%) were on immunosuppressive therapy, and 40% had chronic lung disease. Fifty-nine organisms (54.6%) were isolated in respiratory sources, 21 (19.4%) in blood, 10 (9.2%) skin and soft tissue, and 9 (8.3%) intra-abdominal. Antimicrobial susceptibility reports were available for 64 (59.3%) of the patients. Most of the isolates were susceptible to clarithromycin, amikacin, and tigecycline (93.8%, 93.8%, and 89.1%, respectively). None of the isolates were susceptible to trimethoprim/sulfamethoxazole, and only 1 (1.6%) was susceptible to ciprofloxacin. Thirty-six (33.3%) patients early failed treatment; of those, 17 (15.7%) died while hospitalized. On multivariate analysis, risk factors significantly associated with early treatment failure were disseminated infection (odds ratio [OR], 11.79; 95% confidence interval [CI], 1.53–81.69; P = .04), acute kidney injury (OR, 6.55; 95% CI, 2.4–31.25; P = .018), organ transplantation (OR, 2.37; 95% CI, 2.7–23.1; P = .005), immunosuppressive therapy (OR, 2.81; 95% CI, 1.6–21.4; P = .002), intravenous amikacin treatment (OR, 4.1; 95% CI, 0.9–21; P = .04), clarithromycin resistance (OR,79.5; 95% CI, 6.2–3717.1, P < .001), and presence of prosthetic device (OR, 5.43; 95% CI, 1.57–18.81; P = .008). Receiving macrolide treatment was found to be protective against early treatment failure (OR, 0.13; 95% CI, 0.002–1.8; P = .04).ConclusionsOur cohort of 108 M. abscessus complex isolates in Miami, Florida, showed an in-hospital mortality of 15.7%. Most infections were respiratory. Clarithromycin and amikacin were the most likely agents to be susceptible in vitro. Resistance to fluoroquinolone and trimethoprim/sulfamethoxazole was highly common. Macrolide resistance, immunosuppression, and renal disease were significantly associated with early treatment failure.

Genetic correlates of clarithromycin susceptibility among isolates of the Mycobacterium abscessus group and the potential clinical applicability of a PCR-based analysis of erm(41).

To define the genetic basis of clarithromycin resistance among isolates of the Mycobacterium abscessus group (MAG). We analysed 133 isolates identified as MAG. Species identification was confirmed by sequencing the rpoB gene. Clarithromycin susceptibility testing was performed according to CLSI recommendations, with an extended 14 day incubation. Known resistance genotypes of erm(41) and rrl were identified by sequencing; the presence of deletions in erm(41) was detected by PCR. The 133 MAG isolates included 82 M. abscessus, 27 Mycobacterium massiliense and 24 Mycobacterium bolletii. After the 3 day incubation, only five isolates demonstrated clarithromycin resistance (R); after 14 days of extended incubation, an additional 92 exhibited inducible resistance (IR), with the remaining being susceptible (S). The distribution of susceptibility phenotypes varied among the species. Among M. abscessus isolates, 11% were S, 84% IR and 5% R; among M. bolletii isolates, 96% were IR and 4% R; and among M. massiliense isolates 100% were S. Sequencing of rrl identified only a single isolate with the A2058G mutation. Deletions in erm(41) were present in 30 susceptible isolates; among the remaining 103 isolates, 97 were R or IR (sensitivity, 83%; specificity, 100%; positive predictive value, 100%; negative predictive value, 94%). Among the six susceptible isolates without deletions, all carried the erm(41) T28C point mutation. A significant proportion of MAG isolates demonstrate inducible resistance to clarithromycin that is only detectable with an extended 14 day incubation. Further, the majority of clarithromycin-susceptible MAG isolates have characteristic deletions in erm(41) that can rapidly and reliably be detected by a simple PCR.