Combination of Xpert MTB/RIF and MTBDRplus for Diagnosing Tuberculosis in a Chinese District.

BACKGROUND The incidence of tuberculosis (TB) remains high in many countries, including some middle- and high-income countries without financial constraints for diagnosis and treatment. The implementation of an improved algorithm for diagnosis using 2 rapid molecular tests should help reduce the TB burden. MATERIAL AND METHODS Between April 2018 and March 2019, sputum samples from 711 patients suspected of TB in Nanshan, Shenzhen, China, were included in this prospective study. All sputum samples were examined by smear microscopy, Mycobacterium Growth Indicator Tube (MGIT) 960 culture, and Xpert MTB/RIF. The sputum remnants of Xpert MTB/RIF were used for MTBDRplus to confirm the Xpert results both for the presence of TB bacilli and for resistance to rifampicin (RIF), and also to diagnose multidrug-resistant tuberculosis (MDR-TB). RESULTS In total, 200 (28.1%) of the 711 sputa were positive for TB by Xpert MTB/RIF, and the sputum remnants were used for MTBDRplus. The simultaneous use of Xpert MTB/RIF and MTBDRplus directly on sputum samples permitted accurate bacteriologic confirmation of TB in 64% (119/187) of cases and detection of 70% (7/10) of strains that were MDR. CONCLUSIONS The implementation of 2 rapid nucleic acid-based tests on sputum samples could facilitate the prompt and appropriate treatment of most TB cases.

Use of GeneXpert Remnants for Drug Resistance Profiling and Molecular Epidemiology of Tuberculosis in Libreville, Gabon.

Multidrug-resistant (MDR) and extensively drug resistant (XDR) strains of Mycobacterium tuberculosis pose major problems for global health. The GeneXpert MTB/RIF (Xpert) assay rapidly detects resistance to rifampin (RIFr), but for detection of the additional resistance that defines MDR-TB (MDR tuberculosis) and XDR-TB, and for molecular epidemiology, specimen cultures and a biosafe infrastructure are generally required. We sought to determine whether the remnants of sputa prepared for the Xpert assay could be used directly to find mutations associated with drug resistance and to study molecular epidemiology, thus providing precise characterization of MDR-TB cases in countries lacking biosafety level 3 (BSL3) facilities for M. tuberculosis cultures. After sputa were processed and run on the Xpert instrument, the leftovers of the samples prepared for the Xpert assay were used for PCR amplification and sequencing or for a line probe assay to detect mutations associated with resistance to additional drugs, as well as for molecular epidemiology with spoligotyping and selective mycobacterial interspersed repetitive-unit-variable-number tandem-repeat (MIRU-VNTR) typing. Of 130 sputum samples from Gabon tested with the Xpert assay, 124 yielded interpretable results; 21 (17%) of these were determined to be RIFr Amplification and sequencing or a line probe assay of the Xpert remnants confirmed 18/21 samples as MDR, corresponding to 12/116 (9.5%) new and 6/8 (75%) previously treated TB patients. Spoligotyping and MIRU typing with hypervariable loci identified an MDR Beijing strain present in five samples. We conclude that the remnants of samples processed for the Xpert assay can be used in PCRs to find mutations associated with the resistance to the additional drugs that defines MDR and XDR-TB and to study molecular epidemiology without the need for culturing or a biosafe infrastructure.

Fine-needle aspiration for diagnosis of tuberculous lymphadenitis in children in Bangui, Central African Republic.

BACKGROUND: Tuberculosis (TB) is a major cause of childhood morbidity and mortality in developing countries. One of the main difficulties is obtaining adequate specimens for bacteriological confirmation of the disease in children.The aim of this study is to evaluate the adequacy of fine-needle aspiration (FNA) for the diagnosis of TB. METHODS: In a prospective study conducted at the paediatric hospital in Bangui in 2007-2009, we used fine-needle aspiration to obtain samples for diagnosis of TB from 131 children aged 0-17 years with persistent lymphadenitis. RESULTS: Fine-needle aspiration provided samples that could be used for bacteriological confirmation of TB. Ziehl-Neelsen staining for acid-fast bacilli was positive in 42.7% of samples, and culture identified TB in 67.2% of cases. Of 75 samples that were stain-negative, 49 (65.3%) were culture-positive, while 12 stain-positive samples remained culture-negative. Ten of the 12 stain-positive, culture-negative samples were from patients who had received previous antimicrobial therapy. With regard to phenotypic drug susceptibility, 81/88 strains (91.1%) were fully susceptible to isoniazid, rifampicin, ethambutol and streptomycin, six (6.8%) were resistant to one drug, and one multidrug-resistant strain was found. CONCLUSIONS: Fine-needle aspiration is simple, cost-effective and non-invasive and can be performed by trained staff. Combined with rapid molecular diagnostic tests, fine-needle aspirates could improve the diagnosis of TB and provide valuable information for appropriate treatment and drug resistance.

Molecular detection of fluoroquinolone-resistance in multi-drug resistant tuberculosis in Cambodia suggests low association with XDR phenotypes.

BACKGROUND: Drug susceptibility testing (DST) remains an important concern for implementing treatment of MDR tuberculosis patients. Implementation of molecular tests for drug resistance identification would facilitate DST particularly in developing countries where culturing is difficult to perform. We have characterized multidrug resistant strains in Cambodia using MDTDRsl tests, drug target sequencing and phenotypic tests. METHODS: A total of 65 non-MDR and 101 MDR TB isolates collected between May 2007 and June 2009 were tested for resistance to fluoroquinolones and aminoglycosides/cyclic peptides using the GenoType® MTBDRsl assay and gene sequencing. Rifampicin resistance (RMP-R) was tested using gene sequencing and genotyping was assessed by spoligotyping. RESULTS: A total of 95 of the 101 MDR strains were confirmed to be RMP-R by rpoB gene sequencing. Fourteen of the 101 MDR isolates (14%) carried a gyrA mutation associated with fluoroquinolone-resistance (FQ-R) (detected by the MTBDRsl assay and sequencing) compared with only 1 (1.5%) of the 65 non-MDR strains. Only 1 (1%) of the MDR isolates was found to be XDR TB. The MDR group contained a higher proportion of Beijing or Beijing like strains (58%) than the non MDR group (28%). This percentage is higher in MDR FQ-R strains (71%). CONCLUSIONS: The new GenoType® MTBDRsl assay combined with molecular tests to detect RMP-R and isoniazid resistance (INH-R) represents a valuable tool for the detection of XDR TB. In Cambodia there is a low rate of XDR amongst MDR TB including MDR FQ-R TB. This suggests a low association between FQ-R and XDR TB. Strain spoligotyping confirms Beijing strains to be more prone to accumulate antibiotic resistance.

Rapid identification of mycobacterial whole cells in solid and liquid culture media by matrix-assisted laser desorption ionization-time of flight mass spectrometry.

Mycobacterial identification is based on several methods: conventional biochemical tests that require several weeks for accurate identification, and molecular tools that are now routinely used. However, these techniques are expensive and time-consuming. In this study, an alternative method was developed using matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS). This approach allows a characteristic mass spectral fingerprint to be obtained from whole inactivated mycobacterial cells. We engineered a strategy based on specific profiles in order to identify the most clinically relevant species of mycobacteria. To validate the mycobacterial database, a total of 311 strains belonging to 31 distinct species and 4 species complexes grown in Löwenstein-Jensen (LJ) and liquid (mycobacterium growth indicator tube [MGIT]) media were analyzed. No extraction step was required. Correct identifications were obtained for 97% of strains from LJ and 77% from MGIT media. No misidentification was noted. Our results, based on a very simple protocol, suggest that this system may represent a serious alternative for clinical laboratories to identify mycobacterial species.

Measurement of immunoglobulin G against Mycobacterial antigen A60 in patients with cystic fibrosis and lung infection due to Mycobacterium abscessus.

BACKGROUND: The diagnosis and prognosis of lung infections due to the emerging nontuberculous mycobacterium (NTM) Mycobacterium abscessus are difficult to establish in children with cystic fibrosis. METHODS: We evaluated the usefulness of an enzyme-linked immunosorbent assay for detecting serum IgG antibodies against the ubiquitous mycobacterial antigen A60. RESULTS: A total of 186 patients with cystic fibrosis (mean age+/-SD, 12.0+/-5.0 years) were studied, including 15 M. abscessus-positive patients who fulfilled American Thoracic Society (ATS) criteria for NTM infection (M. abscessus-infected patients), 7 M. abscessus-positive patients who did not fulfill ATS criteria, 20 patients positive for various other NTM who did not fulfill ATS criteria, and 144 NTM-negative control patients; mean IgG titers (+/-SD) for these 4 groups were 718+/-342 U, 193+/-113 U, 129+/-49 U, and 121+/-53 U, respectively (M. abscessus-infected patients vs. each of the other groups, P<.005). The A60 IgG test was both sensitive (approximately 87%) and specific (approximately 95%) if adapted cutoff values were used (150 U and 250 U for patients aged 10 years, respectively) and correlated well with results of acid-fast bacilli smears. CONCLUSION: Measurement of anti-A60 IgG may be useful for both the diagnosis and assessment of activity of M. abscessus lung infection in persons with cystic fibrosis.

Age-related prevalence and distribution of nontuberculous mycobacterial species among patients with cystic fibrosis.

We studied the prevalence and species distribution of nontuberculous mycobacteria (NTM) in relation to age in 385 patients with cystic fibrosis (CF) (mean age +/- standard deviation [range], 12.0 +/- 6.1 [1 to 24] years; sex ratio, 0.53) attending three Parisian centers. The overall prevalence of NTM in sputum was 8.1% (31 out of 385). The following NTM were isolated (n = 33): Mycobacterium abscessus (n = 13, 39.4%), Mycobacterium avium complex (MAC) (n = 7, 21.2%), Mycobacterium gordonae (n = 6, 18.2%), and other (n = 7, 21.2%). Sixteen patients met the American Thoracic Society microbiological criteria for NTM infection, including 11 patients positive for M. abscessus, 4 for MAC, and 1 for MAC and Mycobacterium kansasii. The overall prevalence of NTM was significantly lower in patients under 15 years old than for patients equal to or more than 15 years old (4.8 versus 14.9%, respectively; P = 0.001). M. abscessus was isolated at all ages, while MAC was not recovered before 15 years (prevalence of 0.0 and 5.2% in patients aged 1 to 14 and 15 to 24, respectively; P = 0.001).

Mycobacterium abscessus and children with cystic fibrosis.

We prospectively studied 298 patients with cystic fibrosis (mean age 11.3 years; range 2 months to 32 years; sex ratio, 0.47) for nontuberculous mycobacteria in respiratory samples from January 1, 1996, to December 31, 1999. Mycobacterium abscessus was by far the most prevalent nontuberculous mycobacterium: 15 patients (6 male, 9 female; mean age 11.9 years; range 2.5-22 years) had at least one positive sample for this microorganism (versus 6 patients positive for M. avium complex), including 10 with >3 positive samples (versus 3 patients for M. avium complex). The M. abscessus isolates from 14 patients were typed by pulsed-field gel electrophoresis: each of the 14 patients harbored a unique strain, ruling out a common environmental reservoir or person-to-person transmission. Water samples collected in the cystic fibrosis center were negative for M. abscessus. This major mycobacterial pathogen in children and teenagers with cystic fibrosis does not appear to be acquired nosocomially.