Tuberculosis diagnostics in Fiji: how reliable is culture?

Statistical Investigation of High Culture Contamination Rates in Mycobacteriology Laboratory

Background

Culture of Mycobacterium tuberculosis remains the gold standard in mycobacteriology laboratories, constrained by the very high risk of contamination; therefore, contamination rate is an important key performance indicator (KPI) for laboratory monitoring and evaluation processes.

Aim

This study aimed to investigate the factors that contribute to elevated contamination rates in the Sudan National Tuberculosis Reference Laboratory.

Method

A laboratory-based retrospective study was applied; a TB culture register-book was carefully reviewed and data from 2 January 2019 to 31 December 2019 were entered, cleaned, and analyzed using IBM SPSS 20. A multivariate logistic regression model was performed to examine two dependent variables, the massive contamination, and the single tube contamination against predictors of reason for cultivation, type of specimen, experiment team, and the quarter of cultivation.

Results

It has been found that in 2019 contamination rates were frequently higher; the highest rates were recorded in January and November, 28.2 and 25.2%, respectively. August is an exception with an accepted contamination rate of 4.6%. Of 1,149 specimens requested for culture, 945 (82.2%) samples were eligible to be included in multivariate logistic regression analysis. The team conducting the experiment was significantly associated with a high single tube contamination p value 0.007; adjusted odds ratio AOR 3.570 (1.415–9.005). The correlation between the single tube contamination and the massive contamination is significant; p value 0.01.

Conclusion

The study concludes that high culture contamination is the greatest risk to the quality of laboratory service and can end in either the loss of specimens or delay in the decisions of initiating patient treatment. In addition, the low quality or incompleteness of data increases the uncertainty and undermines the measurement of key performance indicators.

Why oral antiseptic mouth rinsing before sputum collection cannot reduce contamination rate of mycobacterial culture in Burkina-Faso

Background

Tuberculosis (TB) diagnosis by culture in most resource-limited settings is hampered by high contamination rate varying up to 31%. Reduction of oral microorganism loads by mouth rinse with antiseptic before sputum collection showed a reduction of contamination. Moreover, knowing the characteristic of residual contaminant microorganisms would be an asset to understand contamination issues.

Objectives

The aim of this study was to evaluate the effects of mouth rinsing with chlorhexidine on mycobacteria culture contaminations and to characterize morphologically the residual contaminants.

Methods

We consecutively included 158 patients in a TB center. Each of them supplied two sputa: The first before mouth rinse, and the second after 60sec of mouth rinsing with chlorhexidine (0.1%). Petroff method and Lowenstein-Jensen media were used for sputum decontamination and inoculation respectively. The contamination rates were compared, and the type of residual contaminants were characterized and compared.

Results

The contamination rate did not differ before and after the mouth rinse (respectively 58/150 (39 %) vs 61/150 (41 %), p=0.7). The major residual contaminants were Gram positive spore forming bacteria (94%).

Conclusion

Chlorhexidine mouth rinsing before sputum collection did not reduce mycobacterial culture contamination rate. This is probably due to spore forming bacteria, highlighted as major residual contaminants.

Meta-narrative review of molecular methods for diagnosis and monitoring of multidrug-resistant tuberculosis treatment in adults

Early and accurate diagnosis and rigorous clinical and microbiological monitoring of multidrug-resistant tuberculosis (MDR-TB) treatment can curb morbidity and mortality. While others are still under evaluation, the World Health Organization has recommended few novel molecular methods for MDR-TB diagnosis only. We present current molecular methods for diagnosis and monitoring of MDR-TB treatment in TB-endemic settings. A systematic meta-narrative review was conducted according to the RAMESES recommendations. Electronic databases were searched for relevant articles published in English language from January 2013 to June 2018. Based on predefined criteria, two independent reviewers extracted the key messages from relevant articles. Disagreement between them was resolved through discussion and the involvement of a third reviewer, if needed. Key messages were synthesized to create the meta-narratives for method's accuracy, drug-susceptibility capability, and laboratory infrastructure required. We included 33 articles out of 1213 records retrieved, of which 16 (48%) and 12 (36%) were conducted in high- and low-TB-endemic settings, respectively. Xpert® MTB/RIF, GenoType MTBDRplus, GenoType MTBDRsl, FlouroType™ MTBDR, TB TaqMan® array card, and DNA sequencers can accurately guide effective treatment regimens. Molecular bacterial load assay quantifies mycobactericidal impact of these regimens. Although they present inherent advantages compared to the current standard of care, they carry important limitations to implementation and/or scale-up. Therefore, considerable effort must now be directed to implementation and health systems research to maximize these forecasted benefits for individual patient's health outcomes.

Tuberculosis, Fiji, 2002-2013

During 2002–2013, a total of 1,890 tuberculosis cases were recorded in Fiji. Notification rates per 100,000 population increased from 17.4 cases in 2002 to 28.4 in 2013. Older persons were most affected, but tuberculosis also increased sharply in persons 25–44 years of age.