Naturally acquired Mycobacterium tuberculosis complex in laboratory pig-tailed macaques

An outbreak of tuberculosis in endangered northern pig-tailed macaques (Macaca leonina) and milu deer (Elaphurus davidianus) from a zoo in China

BACKGROUND

Tuberculosis (TB) is a zoonotic disease that affects humans and domesticated and wild animals. Animals in zoos are potentially an important source of TB for humans; however they are often neglected in routine disease surveillance programs. This investigation reports an outbreak of TB in milu deer and northern pig-tailed macaques in a zoo in Wuhan, China, which highlighted the need for improved prevention and control of TB in China.

METHODS

Between 24 November and 9 December 2020 two milu deer and a northern pig-tailed macaque that were displaying signs of wasting died. Post-mortem, histopathological diagnosis and acid fast staining were used for the dead animals. Multiple PCR for Mycobacterium tuberculosis complex (MTBC) was performed to identify the bacterial in both milu deer and northern pig-tailed macaque. The serum antibody iELISA for MTBC was then performed for all the surviving milu deer and northern pig-tailed macaques. Six seropositive milu deer and a seropositive northern pig-tailed macaque were subsequently euthanised and, along with two other dead milu deer, necropsied. DNA from these tissue samples was extracted and detected MTBC using PCR and Real-time PCR. Subsequently bacterial isolation was used to confirm the infection.

RESULTS

The lungs of the dead animals displayed gross and histological TB-like lesions and changes, and red staining bacilli were detected in smears of the lesions by microscopy after acid fast staining. Mycobacterium bovis (M. bovis) was detected in the two milu deer and Mycobacterium tuberculosis (M. tb) in the northern pig-tailed macaque using multiple PCR for MTBC. 35.3% surviving milu deer and 50% surviving northern pig-tailed macaques MTBC serologically positive. Six of the euthanised milu deer were also positive on a DNA test for M. bovis and the euthanised northern pig-tailed macaque was positive to M. tb.

CONCLUSIONS

This is the first report of tuberculosis in the endangered species, milu deer and northern pig-tailed macaques, in China, and warrants urgent attention by researchers and conservation authorities. These cases highlight the need for expanding surveillance for MTBC to zoos in China.

Gene-Based Diagnosis of Tuberculosis from Oral Swabs with a New Generation Pathogen Enrichment Technique

A rapid and sensitive diagnosis is crucial for the management of tuberculosis (TB). A simple and label-free approach via homobifunctional imidoesters with a microfluidic platform (SLIM) assay showed a higher sensitivity than the Xpert MTB/RIF assay in the diagnosis of pulmonary TB (PTB). Here, we evaluated the efficacy of the SLIM assay for oral swab samples from cases of suspected PTB. Patients with clinically suspected PTB were prospectively enrolled and oral swab samples were processed using the SLIM assay and the attending physicians were blinded to the results of the SLIM assay. TB cases were defined as those treated with anti-TB chemotherapy for at least 6 months at the discretion of the specialists based on their clinical features and conventional laboratory results, including the Xpert assay. A total of 272 patients (with TB, n = 128 [47.1%]; without TB, n = 144 [52.9%]; mean age, 59.8 years) were enrolled. Overall, the sensitivity of the oral swab-based SLIM assay (65.6%) was higher than that of the sputum-based Xpert assay (43.4%; P = 0.001). Specifically, the SLIM oral swab assay showed a notably higher sensitivity in culture-negative TB cases compared with the Xpert assay (69.0% [95% CI: 49.2 to 84.7%] versus 7.4% [95% CI: 0.9 to 24.3%]; P = 0.001). The specificity of the SLIM and the Xpert assays was 86.1% (95% CI: 79.3 to 91.3%) and 100% (95% CI: 97.2 to 100%), respectively. When only culture-confirmed cases were analyzed, the SLIM oral swab was comparable to sputum Xpert in sensitivity (64.7% versus 54.3%, P = 0.26). The oral swab-based SLIM assay showed a superior sensitivity for TB diagnosis over the sputum-based Xpert assay, especially for culture-negative cases. IMPORTANCE The development of a rapid, accessible, and highly sensitive diagnostic tool is a major challenge in the control and management of tuberculosis. Gene-based diagnostics is recommended for the rapid diagnosis of pulmonary tuberculosis (PTB), but its sensitivity, such as Xpert MTB/RIF assay (Xpert), drops in cases with a low bacterial load. It can only be applied to sputum samples, and it is quite difficult for some patients to produce an adequate amount of sputum. We evaluated the clinical validity of an oral swab-based microfluidic system, i.e., the SLIM assay. The SLIM assay showed a significantly higher sensitivity than the Xpert assay, especially in smear-negative TB cases. This non-sputum-based SLIM assay can be a useful diagnostic test by overcoming the limitations of conventional sputum-based tests in pulmonary TB.

Detection of Mycobacterium tuberculosis complex antibodies in free-ranged wild boar and wild macaques in selected districts in Selangor and reevaluation of tuberculosis serodetection in captive Asian elephants in Pahang, Peninsular Malaysia

Tuberculosis (TB) is a chronic inflammatory and zoonotic disease caused by Mycobacterium tuberculosis complex (MTBC) members, affecting several domestic animals, wildlife species and humans. The preliminary investigation was aimed to detect antibody against MTBC among indigenous wildlife which are free-ranged wild boar, free-ranged wild macaques and captive Asian elephants in selected areas of Selangor and elephant conservation centre in Pahang, respectively. The results indicate that MTBC serodetection rate in wild boar was 16.7% (7.3–33.5 at 95% confidence interval (CI)) using an in-house ELISA bPPD IgG and 10% (3.5–25.6 at 95% CI) by DPP^®VetTB assay, while the wild macaques and Asian elephant were seronegative. The univariate analysis indicates no statistically significant difference in risk factors for sex and age of wild boar but there was a significant positive correlation (P<0.05) between bovine TB in dairy cattle and wild boar seropositivity in the Sepang district.

Sample adequacy controls for infectious disease diagnosis by oral swabbing

Oral swabs are emerging as a non-invasive sample type for diagnosing infectious diseases including Ebola, tuberculosis (TB), and COVID-19. To assure proper sample collection, sample adequacy controls (SACs) are needed that detect substances indicative of samples collected within the oral cavity. This study evaluated two candidate SACs for this purpose. One detected representative oral microbiota (Streptococcus species DNA) and the other, human cells (human mitochondrial DNA, mtDNA). Quantitative PCR (qPCR) assays for the two target cell types were applied to buccal swabs (representing samples collected within the oral cavity) and hand swabs (representing improperly collected samples) obtained from 51 healthy U.S. volunteers. Quantification cycle (Cq) cutoffs that maximized Youden’s index were established for each assay. The streptococcal target at a Cq cutoff of ≤34.9 had 99.0% sensitivity and specificity for oral swab samples, whereas human mtDNA perfectly distinguished between hand and mouth swabs with a Cq cutoff of 31.3. The human mtDNA test was then applied to buccal, tongue, and gum swabs that had previously been collected from TB patients and controls in South Africa, along with “air swabs” collected as negative controls (total N = 292 swabs from 71 subjects). Of these swabs, 287/292 (98%) exhibited the expected Cq values. In a paired analysis the three oral sites yielded indistinguishable amounts of human mtDNA, however PurFlock^TM swabs collected slightly more human mtDNA than did OmniSwabs^TM (p = 0.012). The results indicate that quantification of human mtDNA cannot distinguish swabs collected from different sites within the mouth. However, it can reliably distinguish oral swabs from swabs that were not used orally, which makes it a useful SAC for oral swab-based diagnosis.

Microbiological diagnosis of pulmonary tuberculosis in children by oral swab polymerase chain reaction

Microbiological diagnosis of pediatric pulmonary tuberculosis (TB) is challenging due to the difficulty of collecting and testing sputum from children. We investigated whether easily-obtained oral swab samples are useful alternatives or supplements to sputum. Oral swabs and induced sputum (IS) were collected from 201 South African children with suspected pulmonary TB. IS samples were tested by mycobacterial culture and Xpert MTB/RIF. Oral swabs were tested by PCR targeting IS6110. Children were categorized as Confirmed TB (microbiologic confirmation on IS), Unconfirmed TB (clinical diagnosis only), or Unlikely TB (recovery without TB treatment). Relative to Confirmed TB, PCR on two oral swabs per child was 43% sensitive and 93% specific. This sensitivity fell below that of sputum Xpert (64%). Among children with either Confirmed or Unconfirmed TB, PCR on two oral swabs per child was 31% sensitive and 93% specific, which was more sensitive than sputum testing among this group (21%). Although oral swab analysis had low sensitivity in sputum-positive children, it detected TB in a significant proportion of sputum-negative children who were clinically diagnosed with TB. Specificity at 93% was suboptimal but may improve with the use of automated methods. With further development, oral swabs may become useful supplements to sputum as samples for diagnosis of pulmonary TB in children.

Noninvasive Detection of Tuberculosis by Oral Swab Analysis

Diagnostic tests for tuberculosis (TB) usually require collection of sputum, a viscous material derived from human airways. Sputum can be difficult and hazardous to collect and challenging to process in the laboratory. Oral swabs have been proposed as alternative sample types that are noninvasive and easy to collect. This study evaluated the biological feasibility of oral swab analysis (OSA) for the diagnosis of TB. Swabs were tested from South African adult subjects, including sputum GeneXpert MTB/RIF (GeneXpert)-confirmed TB patients (n = 138), sputum GeneXpert-negative but culture-positive TB patients (n = 10), ill non-TB patients (n = 37), and QuantiFERON-negative controls (n = 34). Swabs were analyzed by using a manual, nonnested quantitative PCR (qPCR) targeting IS6110 Two swab brands and three sites within the oral cavity were compared. Tongue swabbing yielded significantly stronger signals than cheek or gum swabbing. A flocked swab performed better than a more expensive paper swab. In a two-phase study, tongue swabs (two per subject) exhibited a combined sensitivity of 92.8% relative to sputum GeneXpert. Relative to all laboratory-diagnosed TB, the diagnostic yields of sputum GeneXpert (1 sample per subject) and OSA (2 samples per subject) were identical at 49/59 (83.1%) each. The specificity of the OSA was 91.5%. An analysis of "air swabs" suggested that most false-positive results were due to contamination of manual PCRs. With the development of appropriate automated methods, oral swabs could facilitate TB diagnosis in clinical settings and patient populations that are limited by the physical or logistical challenges of sputum collection.

Detection of Mycobacterium tuberculosis Complex in New World Monkeys in Peru

The Mycobacterium tuberculosis complex causes tuberculosis in humans and nonhuman primates and is a global public health concern. Standard diagnostics rely upon host immune responses to detect infection in nonhuman primates and lack sensitivity and specificity across the spectrum of mycobacterial infection in these species. We have previously shown that the Oral Swab PCR (OSP) assay, a direct pathogen detection method, can identify the presence of M. tuberculosis complex in laboratory and free-ranging Old World monkeys. Addressing the current limitations in tuberculosis diagnostics in primates, including sample acquisition and pathogen detection, this paper furthers our understanding of the presence of the tuberculosis-causing bacteria among New World monkeys in close contact with humans. Here we use the minimally invasive OSP assay, which includes buccal swab collection followed by amplification of the IS6110 repetitive nucleic acid sequence specific to M. tuberculosis complex subspecies, to detect the bacteria in the mouths of Peruvian New World monkeys. A total of 220 buccal swabs from 16 species were obtained and positive amplification of the IS6110 sequence was observed in 30 (13.6%) of the samples. To our knowledge, this is the first documentation of M. tuberculosis complex DNA in a diverse sample of Peruvian Neotropical primates.

Detection of Mycobacterium tuberculosis DNA on the oral mucosa of tuberculosis patients

Diagnosis of pulmonary tuberculosis (TB) usually includes laboratory analysis of sputum, a viscous material derived from deep in the airways of patients with active disease. As a diagnostic sample matrix, sputum can be difficult to collect and analyze by microbiological and molecular techniques. An alternative, less invasive sample matrix could greatly simplify TB diagnosis. We hypothesized that Mycobacterium tuberculosis cells or DNA accumulate on the oral epithelia of pulmonary TB patients, and can be collected and detected by using oral (buccal) swabs. To test this hypothesis, 3 swabs each were collected from 20 subjects with active pulmonary TB and from 20 healthy controls. Samples were tested by using a polymerase chain reaction (PCR) specific to the M. tuberculosis IS6110 insertion element. Eighteen out of 20 confirmed case subjects (90%) yielded at least 2 positive swabs. Healthy control samples were 100% negative. This case-control study supports past reports of M. tuberculosis DNA detection in oral swabs. Oral swab samples are non-invasive, non-viscous, and easy to collect with or without active TB symptoms. These characteristics may enable simpler and more active TB case finding strategies.

Non-human sources of Mycobacterium tuberculosis

Mycobacterium tuberculosis is a successful pathogen responsible for the vast majority of deadly tuberculosis cases in humans. It rests in a dormant form in contaminated people who constitute the reservoir with airborne interhuman transmission during pulmonary tuberculosis. M. tuberculosis is therefore regarded majoritary as a human pathogen. Here, we review the evidence for anthroponotic M. tuberculosis infection in non-human primates, other mammals and psittacines. Some infected animals may be sources for zoonotic tuberculosis caused by M. tuberculosis, with wild life trade and zoos being amplifying factors. Moreover, living animals and cadavers can scatter M. tuberculosis in the environment where it could survive for extended periods of time in soil where amoebae could play a role. Although marginal in the epidemiology of human tuberculosis, these data indicate that M. tuberculosis is not uniquely adapted to humans.