Characterization of oral swab samples for diagnosis of pulmonary tuberculosis

Abstract

Oral swab analysis (OSA) has been shown to detect Mycobacterium tuberculosis (MTB) DNA in patients with pulmonary tuberculosis (TB). In previous analyses, qPCR testing of swab samples collected from tongue dorsa was up to 93% sensitive relative to sputum GeneXpert, when 2 swabs per patient were tested. The present study modified sample collection methods to increase sample biomass and characterized the viability of bacilli present in tongue swabs. A qPCR targeting conserved bacterial ribosomal rRNA gene (rDNA) sequences was used to quantify bacterial biomass in samples. There was no detectable reduction in total bacterial rDNA signal over the course of 10 rapidly repeated tongue samplings, indicating that swabs collect only a small portion of the biomass available for testing. Copan FLOQSwabs collected ~2-fold more biomass than Puritan PurFlock swabs, the best brand used previously (p = 0.006). FLOQSwabs were therefore evaluated in patients with possible TB in Uganda. A FLOQSwab was collected from each patient upon enrollment (Day 1) and, in a subset of sputum GeneXpert Ultra-positive patients, a second swab was collected on the following day (Day 2). Swabs were tested for MTB DNA by manual IS6110-targeted qPCR. Relative to sputum GeneXpert Ultra, single-swab sensitivity was 88% (44/50) on Day 1 and 94.4% (17/18) on Day 2. Specificity was 79.2% (42/53). Among an expanded sample of Ugandan patients, 62% (87/141) had colony-forming bacilli in their tongue dorsum swab samples. These findings will help guide further development of this promising TB screening method.

Diagnostic performance of oral swabs for non-sputum based TB diagnosis in a TB/HIV endemic setting

“…Different swab types were also evaluated and found that PurFlock Ultra swabs (Puritan, Guilford, USA) had a modest improvement in signal vs. OmniSwabs which were used in this Kenyan evaluation [ 6 ]. Additional evaluation of a variety of swab types in a Ugandan study revealed that Copan FLOQSwabs collected 2-fold more bacterial biomass than PurFlock Ultra swabs and confirmed the previous findings of improved sensitivity of tongue swabs for OSA [ 14 ].…”

Detection of Mycobacterium tuberculosis complex DNA in oronasal swabs from infected African buffaloes (Syncerus caffer)

“…Oronasal swab samples for identification of MTBC DNA using an automated rapid qPCR, the Xpert MTB/RIF Ultra (Ultra) assay (Cepheid, Sunnyvale, California, USA) have been shown to be an effective, alternative to sputum collection for M. tuberculosis diagnosis in humans, especially in patients with other underlying conditions, such as HIV, and in children that are unable to produce these samples 11 , 12 . Sputum collection in animals is not feasible for bTB diagnosis and collection of other airway secretions, for example, bronchoalveolar lavage, are invasive and time-consuming.…”

“…Since lesions in infected animals are typically found in the respiratory system, mycobacteria in droplets, that pass through the oronasal cavities and adhere to epithelia, or are released from lesions in the oropharyngeal lymph nodes or lung, could potentially be detected by the Ultra assay 11 . Therefore, detection of MTBC DNA by Ultra in these samples may provide evidence of infection 12 . Furthermore, collection of oronasal swabs is an easy, inexpensive, rapid method of sample collection and, together with Ultra, could reveal shedding in buffaloes, which would be a tool to evaluate transmission risk for epidemiological studies.…”

Recovery of Mycobacteria from Heavily Contaminated Environmental Matrices

“…Urine can be primarily decontaminated with 2% hydrochloric acid. It is also possible to use the swab method [ 16 ]. For cultivation, the most used media are classical Löwenstein Jensen and Middlebrook solid media or liquid Middlebrook broth with or without enrichment with antibiotics and growth supplements.…”