Tale of compounding oddities

We present a case of a 59-year-old man, who on being evaluated for abdominal pain and headache, was found to have a pancreatic head mass and inflammatory hypophysitis. Xpert MTB/Rif of the pancreatic mass biopsy showed the presence of tuberculosis (TB) with a very low load, and rifampicin resistance was detected with absence of probes A and B. Pyrosequencing (a novel genotypic test for TB) of the Xpert MTB/Rif isolate detected a single, rare, high-confidence mutation (S512T) in the rpoB region (rifampicin resistance determining region in the MTB genome). The TB mycobacteria growth indicator tube (TBMGIT) phenotypic drug susceptibility test (DST), however, showed rifampicin susceptibility. Incidentally, he was unable to tolerate rifampicin and responded well to a non-rifampicin-based regimen. We discuss a possible hypothesis of the Xpert-DST discordance in accordance with a recent literature review on phenotypic DST methods. We also discuss the utility of pyrosequencing in clinical practice for the diagnosis of TB and its resistance patterns.

Download Full-text

Macrocolonies (Granules) Formation as a Cause of False-Negative Results in the MGIT 960 System: Cause Analysis and Correlation with Mycobacterial Species

BioMed Research International ◽

10.1155/2015/501847 ◽

2015 ◽

Vol 2015 ◽

pp. 1-5 ◽

Cited By ~ 1

Author(s):

Xia Yu ◽

Liping Zhao ◽

Guanglu Jiang ◽

Yifeng Ma ◽

Weimin Li ◽

...

Keyword(s):

Bacterial Load ◽

False Negative ◽

Drug Susceptibility ◽

Granule Formation ◽

Negative Results ◽

Indicator Tube ◽

False Negative Results ◽

Specific Species ◽

Culture Positive ◽

Growth Indicator

Background. The viable mycobacterial bacilli can sometimes form granules in the Mycobacterium Growth Indicator Tube (MGIT) to produce instrument-negative outcomes when BACTEC MGIT 960 culture is performed. The cause of this phenomenon has never been analyzed.Methods. Thirty-one instrument-negative, granule presenting MGIT vials were collected for conducting acid-fast staining and also liquid and solid subculture. Species identification and drug susceptibility test were performed with the recovered strains. Cultivation test was done by inoculating small amount of bacilli into the MGIT vials.Results. Twenty-four and twenty-nine of the tested MGIT vials were smear and culture positive, respectively. In total, 18, 4, and 7 of the cultivated strains were identified asMycobacterium tuberculosiscomplex,M. intracellulare, andM. xenopi, respectively. When a limited amount of bacilli was inoculated, the granule formation was observed forM. xenopistrains in the MGIT system.Conclusions. The granules observed in the instrument-negative MGIT vials consisted of viable bacilli, which emphasized the need of visual inspection to increase recovery rate. Limited bacterial load and specific species might be the cause of granule forming.

Download Full-text

Evaluation of Mycobacteria Growth Indicator Tube (Mgit for drug susceptibility testing of Mycobacterium tuberculosis isolates from clinical specimens

Clinical Microbiology and Infection ◽

10.1111/j.1469-0691.1999.tb00129.x ◽

1999 ◽

Vol 5 (4) ◽

pp. 227-230 ◽

Cited By ~ 4

Author(s):

Pablo Zapata ◽

Miguel Arbeloa ◽

Javier Aznar

Keyword(s):

Mycobacterium Tuberculosis ◽

Susceptibility Testing ◽

Drug Susceptibility ◽

Drug Susceptibility Testing ◽

Clinical Specimens ◽

Indicator Tube ◽

Growth Indicator

Download Full-text

Development of Drug Resistance among Comorbid and Non-Comorbid HIV-Negative Relapsed Cases of Tuberculosis in Lahore, Pakistan

10.21203/rs.3.rs-16991/v1 ◽

2020 ◽

Author(s):

Arslan Ahmed Salam ◽

Aamer Ikram ◽

Maha Fatima ◽

Najma Javed Awan

Keyword(s):

Drug Resistance ◽

Drug Susceptibility ◽

Susceptibility Test ◽

Rifampicin Resistance ◽

Drug Susceptibility Test ◽

Health Crisis ◽

Mdr Tb ◽

History Of ◽

Xpert Assay ◽

Hiv Negative

Abstract Background: Mycobacterium tuberculosis sometimes become resistant to the drugs that are used to treat it. Drug resistant TB (DR-TB) is spread in the same way as drug susceptible TB. DR-TB is a public health crisis. This study aims to find the pattern of drug resistance and correlations between drug resistance and comorbid/non-comorbid conditions in patients with a relapse of TB. Methodology: A cross-sectional study was conducted among 200 HIV-negative relapsed TB patients from 2016-2017 in Mayo Hospital Lahore. The patients’ sputum samples were tested by Ziehl-Neelsen staining to observe acid-fast bacilli. The demographics and medical history of patients was recorded, who were positive for AFB in their sputum samples. Molecular procedure of Gene-Xpert assay was conducted to detect the presence of MTB and rifampicin resistance in the samples. Whereas, the drug susceptibility test (DST) was conducted on the LJ culture medium containing drugs.Results: Out of 200 relapsed TB cases; 97 were comorbid, 99 were non-comorbid. The most prevalent comorbidities were hypertension (42 cases- 43.3%), diabetes (45 cases-46.4%) and hepatitis B (14 cases-14.4%). Among 97 comorbid patients; 37 worked as laborers, 43 earned less than 20,000 PKR and 23 were found to have a history of imprisonment. Whereas in non-comorbid patients; 20 worked as laborers, 28 earned less than 20,000 PKR and 12 had been in prison before. The Gene-Xpert test detected rifampicin resistance (RR) in 20 comorbid (20.6%) and 33 non-comorbid (33.3%) patients. Whereas, the drug susceptibility test (DST) showed that 22 comorbid (22.7%) and 33 non-comorbid (33.3%) patients were RR. A contrast was seen in the results of Gene-Xpert and DST; Gene-Xpert detected 3 cases of RR-negative whereas the same 3 cases were found to be RR-positive on DST. Only 1 case was RR-positive on Gene-Xpert but RR-negative on DST. 17 comorbid patients (17.5%) were diagnosed with MDR-TB and 5 (5.2%) with XDR-TB. Whereas, in non-comorbid patients, there were 26 cases of MDR-TB (26.3%) and 5 cases of XDR-TB (5.1%). There were 2 patients (2.1%) resistant to all drugs.Conclusion: There was a deviation in the results of molecular Gene-Xpert assay compared to the conventional culture methods. Drug resistance was relatively higher in non-comorbid patients than comorbid patients, however, the difference between the two is not very significant.

Download Full-text

Evaluation of a New Method for Rapid Drug Susceptibility Testing of Mycobacterium avium Complex Isolates by Using the Mycobacteria Growth Indicator Tube

Journal of Clinical Microbiology ◽

10.1128/jcm.36.1.64-67.1998 ◽

1998 ◽

Vol 36 (1) ◽

pp. 64-67 ◽

Cited By ~ 10

Author(s):

Claudio Piersimoni ◽

Domenico Nista ◽

Stefano Bornigia ◽

Giuseppina De Sio

Keyword(s):

Mycobacterium Avium ◽

Mycobacterium Avium Complex ◽

Susceptibility Testing ◽

Drug Susceptibility ◽

Drug Susceptibility Testing ◽

New Method ◽

Indicator Tube ◽

Broth Macrodilution ◽

Bactec System ◽

Growth Indicator

The reliability of the Mycobacteria Growth Indicator Tube (MGIT [BBL]) for rapid drug susceptibility testing of Mycobacterium avium complex (MAC) isolates was evaluated. MICs of amikacin, clarithromycin, clofazimine, ethambutol, and rifabutin were determined by the MGIT system for 16 MAC strains. The results were compared with those obtained by the BACTEC broth macrodilution method. The turnaround times were 6 to 8 days (median, 7 days) for the MGIT and 5 to 7 days (median, 6 days) for the BACTEC system. Agreements with BACTEC system-determined MICs, within ±1 log2 dilution, were 100, 100, 88, 63, and 44% for amikacin, clofazimine, rifabutin, clarithromycin, and ethambutol, respectively. Within ±2 log2 dilutions, agreement with BACTEC system-determined MICs increased to 100% for all the tested drugs. In addition, if MGIT-determined MICs were evaluated according to the thresholds adopted for the interpretation of BACTEC system-determined ones, ethambutol was the only drug for which susceptible strains were frequently misclassified as resistant. It is concluded that the MGIT system is a promising, nonradiometric alternative to the BACTEC method for rapid susceptibility testing of MAC isolates; however, additional studies are required to confirm our results and to determine the optimal criteria for the interpretation of ethambutol MICs.

Download Full-text

Occurrence ofrpoBMutations in Isoniazid-Resistant but Rifampin-Susceptible Mycobacterium tuberculosis Isolates from Germany

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.01752-13 ◽

2013 ◽

Vol 58 (1) ◽

pp. 590-592 ◽

Cited By ~ 16

Author(s):

Sönke Andres ◽

Doris Hillemann ◽

Sabine Rüsch-Gerdes ◽

Elvira Richter

Keyword(s):

Mycobacterium Tuberculosis ◽

Susceptibility Testing ◽

Drug Susceptibility ◽

Drug Susceptibility Testing ◽

Content Type ◽

Indicator Tube ◽

Lowenstein Jensen ◽

Proportion Method ◽

Rifampin Resistance ◽

Growth Indicator

ABSTRACTFour out of 143 phenotypically isoniazid-resistant but rifampin-susceptibleMycobacterium tuberculosisstrains that were isolated from patients in Germany in 2011 had mutations in the rifampin resistance-determining region ofrpoB. After performing drug susceptibility testing (DST) with two methods, the proportion method on Löwenstein-Jensen medium and using the Bactec 960 Mycobacteria Growth Indicator Tube system, we conclude that the two methods are equally reliable for phenotypic DST and MIC determination.

Download Full-text