Clinical Whole Genome Sequencing for Clarithromycin and Amikacin Resistance Prediction and Subspecies Identification of Mycobacterium abscessus

Performance Evaluation of a Commercial Automated Library Preparation System for Clinical Microbial Whole-Genome Sequencing Assays

Next-generation sequencing (NGS) has proven clinical utility on disease management and serves as an important tool for genomic surveillance. Currently, hurdles surrounding its implementation, namely the complex and demanding analytical workflows, have impeded its widespread use in many laboratories. To address this challenge, the UCLA Molecular Microbiology and Pathogen Genomics Laboratory evaluated the performance of the Tecan MagicPrep NGS system, a commercial automated solution for library preparation for clinical whole-genome sequencing assays, against the Illumina Nextera DNA Flex Library Prep. Using 35 unique organisms (28 bacteria and 7 fungi) for various clinical applications, including microbial identification and genomic characterization, we compared the quantity and quality of the prepared libraries and the resulting sequences, and concordance of the overall results. We also assessed the impact of its implementation on laboratory workflow. The MagicPrep NGS produced higher library concentrations with smaller sizes, and correspondingly, higher molarity. Quality metrics of the sequences, however, demonstrated no significant impact on the overall results, producing 100% concordance with the reference method. Importantly, workflow analysis showed 5 hours less hands-on time per run with more flexibility. This evaluation study indicates that performance of the MagicPrep NGS is comparable to the Nextera DNA Flex with the added benefit of improving workflow efficiency and reducing labor for performing routine clinical microbial whole-genome sequencing tests.

Clinical Metagenomic Next-Generation Sequencing for Diagnosis of Central Nervous System Infections: Advances and Challenges

Central nervous system (CNS) infections carry a substantial burden of morbidity and mortality worldwide, and accurate and timely diagnosis is required to optimize management. Metagenomic next-generation sequencing (mNGS) has proven to be a valuable tool in detecting pathogens in patients with suspected CNS infection. By sequencing microbial nucleic acids present in a patient's cerebrospinal fluid, brain tissue, or samples collected outside of the CNS, such as plasma, mNGS can detect a wide range of pathogens, including rare, unexpected, and/or fastidious organisms. Furthermore, its target-agnostic approach allows for the identification of both known and novel pathogens. This is particularly useful in cases where conventional diagnostic methods fail to provide an answer. In addition, mNGS can detect multiple microorganisms simultaneously, which is crucial in cases of mixed infections without a clear predominant pathogen. Overall, clinical mNGS testing can help expedite the diagnostic process for CNS infections, guide appropriate management decisions, and ultimately improve clinical outcomes. However, there are key challenges surrounding its use that need to be considered to fully leverage its clinical impact. For example, only a few specialized laboratories offer clinical mNGS due to the complexity of both the laboratory methods and analysis pipelines. Clinicians interpreting mNGS results must be aware of both false negatives-as mNGS is a direct detection modality and requires a sufficient amount of microbial nucleic acid to be present in the sample tested-and false positives-as mNGS detects environmental microbes and their nucleic acids, despite best practices to minimize contamination. Additionally, current costs and turnaround times limit broader implementation of clinical mNGS. Finally, there is uncertainty regarding the best practices for clinical utilization of mNGS, and further work is needed to define the optimal patient population(s), syndrome(s), and time of testing to implement clinical mNGS.

Applications and advances in molecular diagnostics: revolutionizing non-tuberculous mycobacteria species and subspecies identification

Non-tuberculous mycobacteria (NTM) infections pose a significant public health challenge worldwide, affecting individuals across a wide spectrum of immune statuses. Recent epidemiological studies indicate rising incidence rates in both immunocompromised and immunocompetent populations, underscoring the need for enhanced diagnostic and therapeutic approaches. NTM infections often present with symptoms similar to those of tuberculosis, yet with less specificity, increasing the risk of misdiagnosis and potentially adverse outcomes for patients. Consequently, rapid and accurate identification of the pathogen is crucial for precise diagnosis and treatment. Traditional detection methods, notably microbiological culture, are hampered by lengthy incubation periods and a limited capacity to differentiate closely related NTM subtypes, thereby delaying diagnosis and the initiation of targeted therapies. Emerging diagnostic technologies offer new possibilities for the swift detection and accurate identification of NTM infections, playing a critical role in early diagnosis and providing more accurate and comprehensive information. This review delineates the current molecular methodologies for NTM species and subspecies identification. We critically assess the limitations and challenges inherent in these technologies for diagnosing NTM and explore potential future directions for their advancement. It aims to provide valuable insights into advancing the application of molecular diagnostic techniques in NTM infection identification.

Bilateral Jaw Mycobacterium Abscessus Mimicking Actinomycosis: A Postoperative Complication of Wisdom Teeth Extraction

The incidence of nontuberculous mycobacteria infections has surged over recent decades. Mycobacterium abscessus is one example that can present unique diagnostic challenges due to its variable antibiotic resistance profile and its clinical similarities to Actinomycoses israelii in postodontogenic infections. The authors report a case of a 22-year-old healthy female presenting with bilateral mandibular nodules following wisdom teeth extraction. After a presumptive diagnosis of actinomycosis, cultures revealed a Mycobacterium abscessus infection susceptible to macrolides. Magnetic resonance imaging depicted bilateral sinus tracts without osteomyelitis. The patient opted for dual antibiotic therapy, consisting of azithromycin and omadacycline, without surgical intervention. Given her clinical and radiographic improvement after three months, the patient elected to continue dual antibiotic therapy for 12 months with appropriate clinical and radiographic monitoring. This case underscores the importance of early microbial cultures to guide diagnosis and treatment, particularly considering Mycobacterium abscessus's similarities with other pathogens and its variable macrolide susceptibility due to genetic mutations. As highlighted in this case, clinicians must successfully differentiate between and appropriately treat various nontuberculous mycobacteria.

Rapid Mycobacterium abscessus antimicrobial susceptibility testing based on antibiotic treatment response mapping via Raman Microspectroscopy

OBJECTIVES

Antimicrobial susceptibility tests (ASTs) are pivotal tools for detecting and combating infections caused by multidrug-resistant rapidly growing mycobacteria (RGM) but are time-consuming and labor-intensive.

DESIGN

We used a Mycobacterium abscessus-based RGM model to develop a rapid (24-h) AST from the beginning of the strain culture, the Clinical Antimicrobials Susceptibility Test Ramanometry for RGM (CAST-R-RGM). The ASTs obtained for 21 clarithromycin (CLA)-treated and 18 linezolid (LZD)-treated RGM isolates.

RESULTS

CAST-R-RGM employs D2O-probed Raman microspectroscopy to monitor RGM metabolic activity, while also revealing bacterial antimicrobial drug resistance mechanisms. The results of clarithromycin (CLA)-treated and linezolid (LZD)-treated RGM isolates exhibited 90% and 83% categorical agreement, respectively, with conventional AST results of the same isolates. Furthermore, comparisons of time- and concentration-dependent Raman results between CLA- and LZD-treated RGM strains revealed distinct metabolic profiles after 48-h and 72-h drug treatments, despite similar profiles obtained for both drugs after 24-h treatments.

CONCLUSIONS

Ultimately, the rapid, accurate, and low-cost CAST-R-RGM assay offers advantages over conventional culture-based ASTs that warrant its use as a tool for improving patient treatment outcomes and revealing bacterial drug resistance mechanisms.

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

OBJECTIVES

This 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.

METHODS

A 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.

RESULTS

Seventy-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.

CONCLUSIONS

Three 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.

Catheter-Related Bloodstream Infection Caused by Mycolicibacterium iranicum, California, USA

We describe a case of catheter-related bacteremia caused by Mycolicibacterium iranicum in the United States. The case highlights the value of using next-generation sequencing to identify infrequent and emerging pathogens and the challenges associated with choosing appropriate treatments because of limited knowledge of drug resistance mechanisms in those emerging pathogens.

Next Generation and Other Sequencing Technologies in Diagnostic Microbiology and Infectious Diseases

Next-generation sequencing (NGS) technologies have become increasingly available for use in the clinical microbiology diagnostic environment. There are three main applications of these technologies in the clinical microbiology laboratory: whole genome sequencing (WGS), targeted metagenomics sequencing and shotgun metagenomics sequencing. These applications are being utilized for initial identification of pathogenic organisms, the detection of antimicrobial resistance mechanisms and for epidemiologic tracking of organisms within and outside hospital systems. In this review, we analyze these three applications and provide a comprehensive summary of how these applications are currently being used in public health, basic research, and clinical microbiology laboratory environments. In the public health arena, WGS is being used to identify and epidemiologically track food borne outbreaks and disease surveillance. In clinical hospital systems, WGS is used to identify multi-drug-resistant nosocomial infections and track the transmission of these organisms. In addition, we examine how metagenomics sequencing approaches (targeted and shotgun) are being used to circumvent the traditional and biased microbiology culture methods to identify potential pathogens directly from specimens. We also expand on the important factors to consider when implementing these technologies, and what is possible for these technologies in infectious disease diagnosis in the next 5 years.

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

The 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. abscessussubsp. Abscessus (MAA) and 27 strains of M. abscessussubsp. 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.

IMPORTANCEMycobacterium 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.

Inducible Resistance to Amikacin in Mycobacterium abscessus Isolated in Beijing, China

We aimed to determine the prevalence of amikacin (AMK) resistance of clinical Mycobacterium abscessus (MAB) isolates and to investigate if AMK resistance was induced by AMK exposure. A total of 75 MAB isolates underwent susceptibility testing for AMK after 3 and 14 days of incubation, respectively. The partial fragment of the rrs gene conferring AMK resistance was sequenced. The MIC values for AMK ranged from 0.5 to 128 μg/mL, with MIC50 and MIC90 values of 2 and 32 μg/mL, respectively. In addition, 9.3% of isolates (7/75) were resistant to AMK, all of which harbored a mutation within the rrs locus, including six with A1408G mutation and one with a C1409T mutation. Of note, the MICs of three isolates were significantly increased from 2 μg/mL to 64 μg/mL (one isolate) and 2 μg/mL to 128 μg/mL (two isolates), suggesting that three of the MAB isolates had inducible resistance to AMK. In conclusion, our data demonstrate that approximately one-tenth of clinical MAB isolates in Beijing harbored AMK resistance due to the acquisition of rrs mutations. Additionally, we firstly identified that intrinsic AMK resistance is inducible in MAB isolates, highlighting the urgent need to establish a proper method for the in vitro detection of AMK susceptibility in MAB.

Reinfection or relapse? A case study of whole genome sequencing guided genomic characterization of Mycobacterium abscessus chronic infection in a cystic fibrosis patient

A 7-year-old cystic fibrosis patient with increased cough, new pulmonary infiltrate, and declining pulmonary function was diagnosed with clarithromycin resistant Mycobacterium abscessus infection. Treatment was initiated with clofazimine, linezolid and cefoxitin; she responded well to therapy and achieved microbiological clearance after completion of 12-month treatment. One year later, she had re-emergence of worsening symptoms and her sputum culture again grew clarithromycin resistant M. abscessus. Using a laboratory developed whole genome sequencing (WGS) test, the bacterium was determined to be the same strain with the same resistance mechanisms, indicating a relapse. This was deemed a critical element of clinical information, as the isolation of a genetically distinct organism would have indicated a new infection and would have served as evidence that a 12-month regimen was likely sufficient to achieve eradication. The confirmation of a relapse prompted the prolongation of the therapy plan to a goal of 24 months. Reinfection and relapse are great challenges in patients with cystic fibrosis who may acquire new strain of M. abscessus from the environment, may harbor multiple subpopulations of bacteria, or may have persistent infections but intermittent bacteria shedding that could not be eradicated. WGS has emerged as a powerful molecular tool to accurately differentiate re-infection from relapse thus solving this conundrum.

Whole genome sequencing and prediction of antimicrobial susceptibilities in non-tuberculous mycobacteria

Non-tuberculous mycobacteria (NTM) are opportunistic pathogens commonly causing chronic, pulmonary disease which is notoriously hard to treat. Current treatment for NTM infections involves at least three active drugs (including one macrolide: clarithromycin or azithromycin) over 12 months or longer. At present there are limited phenotypic in vitro drug susceptibility testing options for NTM which are standardised globally. As seen with tuberculosis, whole genome sequencing has the potential to transform drug susceptibility testing in NTM, by utilising a genotypic approach. The Comprehensive Resistance Prediction for Tuberculosis is a database used to predict Mycobacterium tuberculosis resistance: at present there are no similar databases available to accurately predict NTM resistance. Recent studies have shown concordance between phenotypic and genotypic NTM resistance results. To benefit from the advantages of whole genome sequencing, further advances in resistance prediction need to take place, as well as there being better information on novel drug mutations and an understanding of the impact of whole genome sequencing on NTM treatment outcomes.

Whole Genome Sequencing in the Management of Non-Tuberculous Mycobacterial Infections

Infections caused by non-tuberculous mycobacteria (NTM) have been a public health problem in recent decades and contribute significantly to the clinical and economic burden globally. The diagnosis of infections is difficult and time-consuming and, in addition, the conventional diagnostics tests do not have sufficient discrimination power in species identification due to cross-reactions and not fully specific probes. However, technological advances have been made and the whole genome sequencing (WGS) method has been shown to be an essential part of routine diagnostics in clinical mycobacteriology laboratories. The use of this technology has contributed to the characterization of new species of mycobacteria, as well as the identification of gene mutations encoding resistance and virulence factors. Sequencing data also allowed to track global outbreaks of nosocomial NTM infections caused by M. abscessus complex and M. chimaera. To highlight the utility of WGS, we summarize recent scientific studies on WGS as a tool suitable for the management of NTM-induced infections in clinical practice.