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A new selective medium for rapidly growing mycobacteria (RGM medium) was evaluated on respiratory specimens from non-cystic fibrosis patients and compared to the mycobacterial growth indicator tube (MGIT) system and Middlebrook 7H11 agar for the isolation of all nontuberculous mycobacteria (NTM). A total of 203 mucolyzed respiratory specimens collected from 163 patients were inoculated on RGM medium and incubated at both 30°C (RGM30) and 35°C (RGM35) over a 28day period. N-Acetyl-L-cysteine-sodium hydroxide (NALC-NaOH)-decontaminated specimens were inoculated into MGIT and Middlebrook 7H11 agar and incubated at 35°C for 42 days. NTM were identified by matrix-assisted laser desorption ionizationtime of flight mass spectrometry (MALDI-TOF MS) or gene sequencing. A total of 133 NTM isolates were recovered overall from 101 (49.8%) specimens collected from 85 (52.1%) patients by a combination of all culture methods. The sensitivity of RGM30 for the recovery of NTM was significantly higher than that of either the MGIT system (76.7% versus 59.4%; P ϭ 0.01) or Middlebrook 7H11 agar (76.7% versus 47.4%; P ϭ 0.0001) alone, but it was not significantly different from that of an acidfast bacillus culture (AFC) which includes both MGIT and Middlebrook 7H11 agar (76.7% versus 63.9%; P ϭ 0.0647). RGM35 had significantly lower sensitivity than the MGIT system (49.6% versus 59.4%; P ϭ 0.0367) and AFC (49.6% versus 63.9%; P ϭ 0.0023). RGM medium was highly effective at inhibiting the growth of nonmycobacterial organisms in the respiratory specimens, with breakthrough contamination rates of 5.4% and 4.4% for RGM30 and RGM35, respectively.

Pulmonary disease arising from slow‐growing mycobacterial infections has emerged as an increasingly prevalent clinical concern over the past two to three decades. Proteins belonging to the family of ESAT‐6 secretion (Esx) systems play critical roles in the virulence of most pathogenic mycobacterial species and are associated with drug resistance. However, no clinical applications can detect and discriminate the expression of species‐specific variants of these proteins in clinical samples, such as early growth cultures, for rapid diagnosis of specific mycobacterial infections, which may require distinct interventions. Conventional immunoassay approaches are not suitable for this purpose due to the significant degree of conservation of Esx proteins among species. Herein we describe the development of a novel immunoprecipitation‐coupled mass spectrometry assay that can distinguish Esx proteins that are expressed by slow‐growing mycobacterial species commonly detected in clinical isolates. This approach uses custom antibodies raised against single semi‐conserved peptide regions in M. tuberculosis (Mtb) EsxB and EsxN to capture corresponding peptides from protein orthologs of mycobacteria associated with human respiratory infections, including Mtb, M. avium, M. intracellulare, M. kansasii, M. gordonae, and M. marinum, to detect these species in standard clinical cultures at the first sign mycobacterial growth to allow rapid disease diagnosis.

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The second messenger, bis-(3¢,5¢)-cyclic dimeric guanosine monophosphate (cyclic di-GMP), is involved in the control of multiple bacterial phenotypes, including those that impact host-pathogen interactions. Bioinformatics analyses predicted that Mycobacterium leprae, an obligate intracellular bacterium and the causative agent of leprosy, encodes three active diguanylate cyclases. In contrast, the related pathogen Mycobacterium tuberculosis encodes only a single diguanylate cyclase. One of the M. leprae unique diguanylate cyclases (ML1419c) was previously shown to be produced early during the course of leprosy. Thus, functional analysis of ML1419c was performed. The gene encoding ML1419c was cloned and expressed in Pseudomonas aeruginosa PAO1 to allow for assessment of cyclic di-GMP production and cyclic di-GMP-mediated phenotypes. Phenotypic studies revealed that ml1419c expression altered colony morphology, motility and biofilm formation of P. aeruginosa PAO1 in a manner consistent with increased cyclic di-GMP production. Direct measurement of cyclic di-GMP levels by liquid chromatography-mass spectrometry confirmed that ml1419c expression increased cyclic di-GMP production in P. aeruginosa PAO1 cultures in comparison to the vector control. The observed phenotypes and increased levels of cyclic di-GMP detected in P. aeruginosa expressing ml1419c could be abrogated by mutation of the active site in ML1419c. These studies demonstrated that ML1419c of M. leprae functions as diguanylate cyclase to synthesize cyclic di-GMP. Thus, this protein was renamed DgcA (Diguanylate cyclase A). These results also demonstrated the ability to use P. aeruginosa as a heterologous host for characterizing the function of proteins involved in the cyclic di-GMP pathway of a pathogen refractory to in vitro growth, M. leprae.

To determine the accuracy of multiplex real-time PCR (Anyplex™ II MTB/MDR kit) in detecting Isoniazid (INH)-and Rifampin (RIF)-resistant Mycobacterium tuberculosis strains from various clinical specimens. The performance of Anyplex™ II MTB/MDR kit in detecting INH-and RIF-resistant M. tuberculosis compared to the conventional drug susceptibility tests by Mycobacterial Growth Indicator Tube (MGIT). A total of 430 clinical samples had positive results for M. tuberculosis from both Anyplex™ II MTB/MDR kit assay and mycobacterial cultures by MGIT method. When compared to MGITs, the sensitivity and specificity of Anyplex™ II MTB/MDR kit in detecting INH-resistant TB were 85.71% and 99.75%, respectively. For the detection of MDR-TB, the sensitivity and specificity of the test were 82.35% and 99.76%, respectively. The positive predictive values and negative predictive values to detect INH-resistant TB were 96.77% and 98.75%, respectively. Anyplex™ II MTB/MDR kit can be used to rapidly detect isoniazid and rifampicin resistances. It has a high sensitivity, specificity and PPV in detecting INH-resistant TB and MDR-TB. This test can be used as an alternative test to Xpert MTB/ RIF because it can rapidly detect both INH-resistant TB and RIF-resistant TB.

Background Diagnosing tuberculosis (TB) in children is challenging due to its paucibacillary nature. Loop-mediated isothermal amplification (TB-LAMP) is a simple, rapid, and specific point-of-care molecular diagnostic test. However, evaluation of its performance remains limited in children. This study aimed to evaluate the diagnostic performance of Eiken TB-LAMP among children with presumed tuberculosis disease. Methods Pulmonary and extrapulmonary specimens were collected from children under 18 years with presumed TB. Each specimen was tested by using TB-LAMP, acid-fast bacilli (AFB) smear microscopy, and one of the two molecular assays (polymerase chain reaction [PCR] or Xpert MTB/RIF). Sensitivity and specificity were estimated compared to mycobacterial culture as reference standard. Results From January 2020 to January 2021, 75 participants with presumed TB were enrolled with median age of 7 years (IQR 2-12). Seventeen specimens from 16 (21.3%) children had bacteriologically confirmed TB: 10 pulmonary and 7 extrapulmonary specimens. Overall sensitivity and specificity of TB-LAMP was 76.5% (95% CI 50.1%-93.2%) and 100% (95% CI 94.3%-100%), respectively. It had significantly higher sensitivity than AFB (52.9%, 95% CI 27.8%-77.0%) and similar to other molecular assays; PCR 82.4% (95% CI 56.6%-96.2%), Xpert MTB/RIF 70.0% (95% CI 34.8%-93.3%). Sensitivity of TB-LAMP for pulmonary, lymph node tissue, and extrapulmonary fluid was 80% (95% CI 44.4%-97.5%), 100% (95% CI 39.8-100), and 33.3% (95% CI 0.8-90.6), respectively. TB-LAMP detected all smear-positive (N = 9) and 50% of smear-negative (N = 8) specimens. Conclusions TB-LAMP had higher sensitivity than AFB microscopy and accuracy similar to other molecular assays in both pulmonary and extrapulmonary specimens. These findings support using TB-LAMP as a point-of-care test in children.

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