In this retrospective study, we used whole-genome sequencing (WGS) to delineate transmission dynamics, characterize drug-resistance markers, and identify risk factors of transmission among Papua New Guinea residents of the Torres Strait Protected Zone (TSPZ) who had tuberculosis diagnoses during 2010–2015. Of 117 isolates collected, we could acquire WGS data for 100; 79 were Beijing sublineage 2.2.1.1, which was associated with active transmission (odds ratio 6.190, 95% CI 2.221–18.077). Strains were distributed widely throughout the TSPZ. Clustering occurred more often within than between villages (p = 0.0013). Including 4 multidrug-resistant tuberculosis isolates from Australia citizens epidemiologically linked to the TSPZ into the transmission network analysis revealed 2 probable cross-border transmission events. All multidrug-resistant isolates (33/104) belonged to Beijing sublineage 2.2.1.1 and had high-level isoniazid and ethionamide co-resistance; 2 isolates were extensively drug resistant. Including WGS in regional surveillance could improve tuberculosis transmission tracking and control strategies within the TSPZ.

Introduction Delays between self-reported symptom onset and commencement of effective treatment contribute to ongoing tuberculosis (TB) transmission; this is a particular concern in patients with drug-resistant (DR)-TB. We assessed improvements in time to commencement of effective treatment in patients diagnosed with DR-TB in the Torres Strait region. Methods All laboratory-confirmed DR-TB cases diagnosed in the Torres Strait between 1 March 2000 and 31 March 2020 were reviewed. We assessed the total time from self-reported onset of symptoms to effective treatment commencement in different programmatic time periods. Pairwise analyses and time to event proportional hazard calculations were used to explore the association between delays in median time to effective treatment, and selected variables. Data were further analysed to examine predictors of excessive treatment delay. Results The median number of days from self-reported onset of symptoms to effective treatment commencement was 124 days. Between 2006 and 2012, most (57%) cases exceeded this grand median while the median time to treat in the most recent time period (2016-2020) was significantly reduced to 29 days (p <0.001). Although there was a reduction in the median time to treat with the introduction of Xpert MTB/RIF (135 days pre-Xpert vs 67 days post-Xpert) this was not statistically significant (p 0.07). Establishment of the Torres and Cape TB Control Unit on Thursday Island (2016-2020) when compared with previous TB programs (2000-2005 p <0.04; 2006-2012 p <0.001) and case type (new vs past treatment; p 0.02) were significantly associated with reduced treatment delay. Conclusion Minimising TB treatment delay in remote settings like the Torres Strait / Papua New Guinea cross-border region requires effective decentralised diagnosis and management structures. Study results suggest that the establishment of the Torres and Cape TB Control Unit on Thursday Island helped to improve time to treatment for TB patients in the region. Possible contributing factors include better symptom recognition, TB education, cross-border communication and patient-centred care.

Introduction: Smear-positive pulmonary tuberculosis (PTB) requires rapid diagnosis and treatment to prevent ongoing transmission. Collection of two sputum specimens is considered the minimum requirement for the diagnosis of PTB but current guidelines in the Torres Strait Islands, Australia, recommend three sputum specimens; this frequently delays treatment initiation. Methods: A retrospective study was performed to ascertain the diagnostic yield of sputum specimens collected in the Torres Strait Islands. The study assessed demographics and characteristics of all PTB cases diagnosed between 2000 and 2018, and assessed the diagnostic yield in 143 patients from whom at least three sputum specimens had been collected prior to treatment commencement. Incremental and cumulative yield was calculated for each sputum specimen. Data were further analysed using binary logistic regression to examine the association between selected characteristics and a smear-positive acid-fast bacilli (AFB) result. Results: Overall, AFB was detected from the first or second sputum specimen in 97 of 101 PTB cases that were sputum smear positive. A smear-positive result was more common (odds ratio 2.84, 95% confidence interval 1.08-7.46) for Papua New Guinea nationals compared to Australian born patients. Of the 429 samples collected, 76 (18%) were of poor quality and the association between poor quality specimens and smear-negative results was significant (p<0.01). Among sputum smear-negative cases, 5/42 (12%) had three consecutive poor quality specimens. The most common collection modality in adults was voluntary expectoration; done in 391/429 (91%) of all specimens collected. Alternative specimen collection methods were mainly used in children; induced sputum 1/429 (0.2%), gastric aspirate 26/429 (6%) and nasopharyngeal aspirate 7/429 (1.6%). Errors with labelling, packaging and transportation occurred in 44 specimens from 15 patients. Conclusion: Two good quality specimens ensure adequate diagnostic yield for PTB and a third specimen should only be collected from patients with two negative specimens who have persistent symptoms. Ideally, decentralised Xpert Ultra® should be the frontline diagnostic test in remote settings, especially in settings like the Torres Strait Islands with high rates of drugresistant TB.

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