title: Evaluation of a simple in-house test to presumptively differentiate Mycobacterium tuberculosis complex from nontuberculous mycobacteria by detection of p-nitrobenzoic acid metabolites.
abstract: The timely differentiation of Mycobacterium tuberculosis complex (MTC) and non-tubercular mycobacterium (NTM) species is urgently needed in patient care since the routine laboratory method is time consuming and cumbersome. An easy and cheap method which can successfully distinguish MTC from NTM was established and evaluated. 38 mycobacterial type and reference strains and 65 clinical isolates representing 10 species of mycobacterium were included in this study. Metabolites of p-nitrobenzoic acid (PNB) reduction were identified using liquid chromatography and tandem mass spectrometry (LC/MS/MS). A spectrophotometric method was developed to detect these metabolites, which was evaluated on a number of MTC and NTM species. All of the tested NTM species and strains reduced PNB to p-aminobenzoic acid (PABA), while none of the MTC strains showed a similar activity. Spectrophotometric detection of PABA had 100% sensitivity and specificity for MTC and NTM differentiation among the type strains and the clinical isolates tested. PABA was identified as one of the metabolites of PNB reduction. All the tested NTM species metabolized PNB to PABA whereas the MTC members lacked this activity. A simple, specific and cost-effective method based on PABA production was established in order to discriminate MTC from NTM from cultured organisms.
authors.affiliation: National Clinical Laboratory on Tuberculosis, Beijing Key Laboratory on Drug-resistant Tuberculosis Research, Beijing Chest Hospital, Capital Medical University, Beijing Tuberculosis and Thoracic Tumor Institute, Beijing, China.
authors.forename: Guirong
authors.initials: G
authors.lastname: Wang
authors.forename: Xia
authors.initials: X
authors.lastname: Yu
authors.forename: Qian
authors.initials: Q
authors.lastname: Liang
authors.forename: Suting
authors.initials: S
authors.lastname: Chen
authors.forename: Stuart
authors.initials: S
authors.lastname: Wilson
authors.forename: Hairong
authors.initials: H
authors.lastname: Huang
mesh_terms: D010129:4-Aminobenzoic Acid / Q000032:analysis / Q000378:metabolism*; D015373:Bacterial Typing Techniques / Q000191:economics / Q000379:methods*; D001711:Biotransformation; D002853:Chromatography, Liquid; D006801:Humans; D009169:Mycobacterium tuberculosis / Q000302:isolation & purification / Q000378:metabolism*; D009579:Nitrobenzoates / Q000378:metabolism*; D009170:Nontuberculous Mycobacteria / Q000302:isolation & purification / Q000378:metabolism*; D012680:Sensitivity and Specificity; D013053:Spectrophotometry; D053719:Tandem Mass Spectrometry; D014376:Tuberculosis / Q000175:diagnosis* / Q000382:microbiology
chemical_list: D009579:Nitrobenzoates; C008629:4-nitrobenzoic acid; D010129:4-Aminobenzoic Acid