Detection of Mycobacterium tuberculosis Complex Bacilli and Nucleic Acids From Tongue Swabs in Young, Hospitalized Children

Abstract

Diagnosis of tuberculosis in pediatric patients remains challenging due to inherent difficulties associated with obtaining respiratory samples for molecular and culture-based testing. To address this, recent studies have highlighted the utility of tongue swabs to detect Mycobacterium tuberculosis genomic DNA in the oral epithelia of tuberculosis infected adults. It is unknown whether tongue swabs have similar utility for diagnosis of childhood tuberculosis and if the presence of DNA in these swabs was associated with whole bacilli. We therefore sought to conduct a preliminary assessment of the utility of tongue swabs to detect tubercle bacilli and their associated genetic material in young children. For this, we recruited hospitalized children with clinically diagnosed tuberculosis (n = 26) or lower respiratory tract infection (LRTI, n = 9). These categories were blinded for downstream laboratory tests, which included PCR, spoligotyping, smear microscopy, and culture. Mtb genomic DNA was detected by PCR only in clinically diagnosed TB cases [11/26 (31.4%)] and not in cases with LRTI. Of these, 5/11 [45.5%] were associated with a spoligotype. Spoligotyping also detected an additional six specimens that were negative by PCR. Using smear microscopy, 19/26 [73.1%] and 4/9 [44.4] were Mtb positive in the tuberculosis or LRTI categories respectively. We noted positive results on all three tests in 5/26 [19.2%] in the tuberculosis category and 0/9 in the LRTI category. All specimens were culture negative. Collectively, these preliminary data present a compelling case for broader testing of tongue swabs to diagnose tuberculosis in children where obtaining standard sputum specimens is not easy.

Oral swabs with a rapid molecular diagnostic test for pulmonary tuberculosis in adults and children: a systematic review

“…Using an alternative processing method, where a single swab was boiled, incubated, and mixed without using sample reagent, sensitivity was very similar at 77% (60–90) and specificity was 100% (16–100). 21 With the increased biomass collected by double swabs, the processing method using Cepheid sample reagent showed similar sensitivity to the boil method (73% using the Cepheid sample reagent vs 77% using the boil method). The use of sample reagent and similar processing methods to sputum potentially allows laboratories already performing sputum testing with Xpert MTB/RIF Ultra to use oral swabs as a sample type with minimal change in processing methods.…”

“… 20 One study was considered high concern for applicability for patient selection, as it was carried out in a tertiary care referral hospital; however the study was carried out in a population of children with a relatively high prevalence of HIV (17·1%), both of which are target population characteristics for non-sputum-based diagnostic samples. 21 All studies were assessed as unclear concern for applicability of the index test as there is no standard methodology defined for using oral swabs for tuberculosis detection. All studies were considered low risk of bias in the reference test domain, and 18 were assessed as low risk of bias in the flow and timing domain.…”

“…This was the first study in adults with presumptive tuberculosis to demonstrate high sensitivity of oral swabs using Xpert MTB/RIF Ultra. The authors found overall sensitivity of 72% (95% CI 59–83) and specificity of 100% (95% CI 97–100) using a microbiological reference standard, 21 achieved using a double swabbing strategy and processing with Cepheid sample reagent and Xpert MTB/RIF Ultra. Using an alternative processing method, where a single swab was boiled, incubated, and mixed without using sample reagent, sensitivity was very similar at 77% (60–90) and specificity was 100% (16–100).…”

Diagnostic accuracy of oral swab for detection of pulmonary tuberculosis: a systematic review and meta-analysis

“…Notably, Cox et al found that the yield of microbiologic confirmation using oral swab specimens in children with pulmonary TB was suboptimal ( 18 ). Flores et al demonstrated that tongue swabs can be employed for diagnosing TB in children who are clinically diagnosed with TB but are unable to produce sputum samples ( 33 ). Nevertheless, interpretation of these results requires caution as the number of studies on diagnosing OSA in children with pulmonary TB and HIV-positive individuals with pulmonary TB is limited.…”

Drug resistant tuberculosis: Implications for transmission, diagnosis, and disease management

“…For example, the use of cheek swabs have been assessed in adults living with HIV (LaCourse et al, 2022). While tongue swabs were evaluated in young children, a population were traditional sputum samples are not easily obtained (Ealand et al, 2021).…”