Screening for TB by sputum culture in high-risk groups in Copenhagen, Denmark: a novel and promising approach.

INTRODUCTION: Evidence on screening high-risk groups for TB by mobile X-ray in low-incidence countries is building, but knowledge on other possible screening methods is limited. In this retrospective study we report results from a community based programme screening for TB by spot sputum culture. METHODS: On seven occasions, from September 2012 through June 2014, we offered TB screening to all persons present at 11 locations where socially marginalised people gather in Copenhagen. Spot sputum samples from participants were examined by smear microscopy and culture. Genotype, nucleic acid amplification test and chest X-ray were done if TB was found. RESULTS: Among 1075 participants, we identified 36 cases of TB. Twenty-four cases (66.7%) were identified at the first screening of each participant, that is, the prevalence of TB was 2233/100 000. Thirty-five (97%) of the TB cases were culture-positive and seven (19.4%) were smear-positive. Twelve out of 21 (57.1%) cases tested were nucleic acid amplification test positive. Twenty-eight (77.8%) had chest X-ray suggestive of TB. All patients with TB started treatment, 30 (83.3%) had a successful outcome. DISCUSSION: Screening for TB by spot sputum culture is possible and a promising alternative to mobile X-ray in a community based screening programme. 22.2% did not have chest X-ray suggestive of TB and would not have been identified using mobile X-ray. Most of the TB cases were smear-negative, suggesting that they were identified at an early, less infectious stage, which is essential in order to prevent transmission and gain infection control.

Set-up and validation of mycobacterial interspersed repetitive unit-variable number of tandem repeat (MIRU-VNTR) analysis of Mycobacterium tuberculosis using BioNumerics software.

The objective was to describe and validate a new and alternative software procedure for 24-locus mycobacterial interspersed repetitive unit-variable number-tandem repeat (MIRU-VNTR) typing of Mycobacterium tuberculosis (Mtb) based on the multipurpose BioNumerics software. DNA from randomly selected isolates of Mtb from two European laboratories, including external control samples for MIRU-VNTR typing, were analysed. Samples were genotyped using the commercial 24-locus VNTR typing kit from GenoScreen. The PCR amplified fragments were separated by capillary electrophoresis. For the subsequent analyses, the currently used software GeneMapper was compared with BioNumerics. The endpoint was the level of concordance when comparing genotyping results obtained from BioNumerics with results obtained from GeneMapper and the ECDC proficiency study reference results. Also, the number of necessary manual standard size corrections and allele assignments in the two different software methods were compared. In total, 272 DNA samples, including the ECDC proficiency panel, were analysed. For all samples, there were 100% concordance of results. For a randomly selected set of 96 samples the numbers of manual corrections needed for size standards were 199 with GeneMapper versus zero for BioNumerics. The numbers of manual corrections for allele assignments were 122 with GeneMapper versus 16 with BioNumerics. In conclusion, we have validated the multipurpose software BioNumerics for standard 24-locus MIRU-VNTR typing and the software shows promising benefits in terms of simplification and minimization of hand-on time.

Occupational Tuberculosis in Denmark through 21 Years Analysed by Nationwide Genotyping.

Tuberculosis (TB) is a well-known occupational hazard. Based on more than two decades (1992-2012) of centralized nationwide genotyping of all Mycobacterium tuberculosis culture-positive TB patients in Denmark, we compared M. tuberculosis genotypes from all cases notified as presumed occupational (N = 130) with M. tuberculosis genotypes from all TB cases present in the country (N = 7,127). From 1992 through 2006, the IS6110 Restriction Fragment Length Polymorphism (RFLP) method was used for genotyping, whereas from 2005 to present, the 24-locus-based Mycobacterial Interspersed Repetitive Unit-Variable Number of Tandem Repeat (MIRU-VNTR) was used. An occupational TB case was classified as clustered if the genotype was 100% identical to at least one other genotype. Subsequently, based on genotype, time period, smear positivity, geography, susceptibility pattern, and any reported epidemiological links between the occupational cases and any potential source cases, the occupational case was categorized as confirmed, likely, possible or unlikely occupationally infected. Among the 130 notified presumed occupational cases, 12 (9.2%) could be classified as confirmed and 46 (35.4%) as unlikely, accounting for nearly half of all cases (44.6%). The remaining 72 cases (55.4%) were categorized as possible. Within this group, 15 cases (11.5%) were assessed to be likely occupational. Our study shows that genotyping can serve as an important tool for disentangle occupational TB in high-income low incidence settings, but still needs to be combined with good epidemiological linkage information.