Misdiagnosis of tuberculosis and the clinical relevance of non—tuberculous mycobacteria in Zambia

Challenges and knowledge gaps in the management of non-tuberculous mycobacterial pulmonary disease in sub-Saharan African countries with a high tuberculosis burden: a scoping review

INTRODUCTION

In sub-Saharan African (SSA) countries endemic for tuberculosis (TB), previous TB is a significant risk factor for non-tuberculous mycobacterial pulmonary disease (NTM-PD). The deployment of GeneXpert MTB/RIF in pulmonary TB diagnostic work-up regularly identifies symptomatic patients with a positive smear microscopy but negative GeneXpert, indicative of NTM presence. This scoping review outlines recent evidence for NTM-PD diagnosis and management in SSA.

OBJECTIVE

The review's objective was to outline the risk factors, available diagnostics, management options and outcomes of NTM-PD in high-burden TB settings in SSA using the population-concept-context framework.

DESIGN AND DATA SOURCES

We searched existing literature from PubMed, Web of Science, African Journals Online, Google Scholar and grey literature. Studies published between January 2005 and December 2022 were retained. Data were extracted into Rayyan software and Mendeley and summarised using Excel.

RESULTS

We identified 785 potential articles, of which 105 were included in the full-text review, with 7 papers retained. Included articles used international criteria for diagnosing NTM-PD. Multiple papers were excluded due to non-application of the criteria, suggesting challenging application in the SSA setting. Identified risk factors include previous TB, smoking and mining. Most commonly, chest radiography and not CT was used for the radiological diagnosis of PD, which may miss early changes related to NTM-PD. Molecular methods for NTM species identification were employed in research settings, usually at referral centres, but were unavailable for routine care. Most studies did not report a standardised approach to treatment and they were not offered treatment for the specific disease, marking a lack of guidance in treatment decision-making. When treatment was provided, the outcome was often not reported due to the lack of implementation of standardised outcome definitions.

CONCLUSIONS

These outlined challenges present a unique opportunity for researchers to undertake further studies in NTM-PD and proffer solutions more applicable to SSA.

Nontuberculous Mycobacteria in Humans, Animals, and Water in Zambia: A Systematic Review

Nontuberculous mycobacteria (NTM) are environmental opportunistic pathogens of humans and animals that are emerging with a serious public health impact particularly in individuals with Acquired Immunodeficiency Syndromes. Recent scientific evidence is shifting from NTMs being known as traditional environmental organisms to serious pathogenic organisms in both animals and humans. In humans, factors attributable to this rise have been linked mainly to Human Immunodeficiency Virus and Acquired Immunodeficiency Syndrome pandemic. In recent years there has been an increase in multidrug resistant Tuberculosis in Zambia and it is thought that NTMs could possibly be the cause. This study was therefore formulated to review available information on the prevalence of NTM in humans, animals and the environment, species distribution, zoonotic potential and public health importance in Zambia. This review was conducted in accordance with PRISMA guidelines. A literature search was done in PubMed and Google scholar using predefined search terms such as ‘nontuberculous mycobacteria’, ‘atypical mycobacteria’, ‘mycobacteria other than mycobacterium tuberculosis’ and ‘Zambia’, in combination with Boolean operators (AND, OR). This particular systematic review draws findings based on literature search between 2000 and 2020. Through literature search 243 papers were identified, 23 duplicates were identified and removed and 206 articles were excluded as they did not meet the inclusion criteria. The full text of the remaining 14 articles were considered for this review. The overall prevalence of NTM in humans was 24.39%, in water 21.5%, in animals 16.05% of which the prevalence in cattle was 14.81% and Kafue Lechwe 1.23%. Mycobacterium intracellulare was the most common isolated nontuberculous mycobacteria in humans and cattle while Mycobacterium gordonae was the most common in water, and Mycobacterium stomatepiae sp Nov in Kafue Lechwe. Nontuberculous mycobacteria are an emerging public health threat in Zambia both in humans and animals and this calls for the need for molecular information on the zoonotic transmission of nontuberculous mycobacteria. Increased awareness of nontuberculous mycobacteria diseases among clinicians and laboratory personnel is crucial for patient management and an essential step for facilitating the identification of nontuberculous mycobacteria species in laboratories.

Studies of antimicrobial resistance in rare mycobacteria from a nosocomial environment

BACKGROUND

Nontuberculous mycobacteria (NTM) are ubiquitous in nature and recognized agents of opportunistic infection, which is often aggravated by their intrinsic resistance to antimicrobials, poorly defined therapeutic strategies and by the lack of new drugs. However, evaluation of their prevalence in anthropogenic environments and the associated antimicrobial resistance profiles have been neglected. In this work, we sought to determine minimal inhibitory concentrations of 25 antimicrobials against 5 NTM isolates recovered from a tertiary-care hospital surfaces. Antimicrobial susceptibilities of 5 other Corynebacterineae isolated from the same hospital were also determined for their potential clinical relevance.

RESULTS

Our phylogenetic study with each of the NTM isolates confirm they belong to Mycobacterium obuense, Mycobacterium mucogenicum and Mycobacterium paragordonae species, the latter initially misidentified as strains of M. gordonae, a species frequently isolated from patients with NTM disease in Portugal. In contrast to other strains, the M. obuense and M. mucogenicum examined here were resistant to several of the CLSI-recommended drugs, suggestive of multidrug-resistant profiles. Surprisingly, M. obuense was susceptible to vancomycin. Their genomes were sequenced allowing detection of gene erm (erythromycin resistance methylase) in M. obuense, explaining its resistance to clarithromycin. Remarkably, and unlike other strains of the genus, the Corynebacterium isolates were highly resistant to penicillin, ciprofloxacin and linezolid.

CONCLUSIONS

This study highlights the importance of implementing effective measures to screen, accurately identify and control viable NTM and closely related bacteria in hospital settings. Our report on the occurrence of rare NTM species with antibiotic susceptibility profiles that are distinct from those of the corresponding Type strains, along with unexpected resistance mechanisms detected seem to suggest that resistance may be more common than previously thought and also a potential threat to frail and otherwise vulnerable inpatients.

IP-10 Kinetics in the First Week of Therapy are Strongly Associated with Bacteriological Confirmation of Tuberculosis Diagnosis in HIV-Infected Patients

Simple effective tools to monitor the long treatment of tuberculosis (TB) are lacking. Easily measured host derived biomarkers have been identified but need to be validated in larger studies and different population groups. Here we investigate the early response in IP-10 levels (between day 0 and day 7 of TB therapy) to identify bacteriological status at diagnosis among 127 HIV-infected patients starting TB treatment. All participants were then classified as responding or not responding to treatment blindly using a previously described IP-10 kinetic algorithm. There were 77 bacteriologically confirmed cases and 41 Xpert MTB/RIF® and culture negative cases. Most participants had a measurable decline in IP-10 during the first 7 days of therapy. Bacteriologically confirmed cases were more likely to have high IP-10 levels at D0 and had a steeper decline than clinically diagnosed cases (mean decline difference 2231 pg/dl, 95% CI: 897–3566, p = 0.0013). Bacteriologically confirmed cases were more likely to have a measurable decline in IP-10 at day 7 than clinically diagnosed cases (48/77 (62.3%) vs 13/41 (31.7%), p < 0.001). This study confirms the association between a decrease in IP-10 levels during the first week of treatment and a bacteriological confirmation at diagnosis in a large cohort of HIV positive patients.

Molecular identification of non-tuberculous mycobacteria isolated from clinical specimens in Zambia

BACKGROUND

The emergence of Acquired Immunodeficiency Syndrome has highlighted the increased incidence and importance of the disease caused by Non-tuberculous Mycobacteria (NTM). While disease due to M. avium-intracellulare complex is apparently common throughout the world, other Non-tuberculous mycobacterial species have been isolated from both immunocompromised and immunocompetent individuals. The increasing number of infections caused by these organisms has made it clinically important to quickly identify mycobacterial species. The diagnosis of a pathogenic versus a non-pathogenic species not only has epidemiological implications but is also relevant to the demands of patient management. Since antibiotic treatment varies according to the species encountered, species identification would reduce the burden of some of these emerging opportunistic pathogens especially in immunocompromised patients and improve their quality of life.

FINDINGS

A total of 91 NTM suspected isolates from four regions of Zambia were included in the study. These isolates were identified using the sequence analysis of the 16S-23S rRNA intergenic transcribed spacer (ITS) region of Mycobacteria. Fifty-four of the 91 (59%) isolates were identified as NTM and these included M. intracellulare (27.8%), M. lentiflavum (16.7%), M. avium (14.8%), M. fortuitum (7.4%), M. gordonae (7.4%), M. kumamotonense (3.7%), M. indicus pranii (3.7%), M. peregrinum (3.7%), M. elephantis (1.85%), M. flavescens (1.85%), M. asiaticum (1.85%), M. bouchedurhonense (1.85%), M. chimaera (1.85%), M. europaeum (1.85%), M. neourum (1.85%), M. nonchromogenicum (1.5%).

CONCLUSION

The study has shown that DNA sequencing of the ITS region may be useful in the preliminary identification of NTM species. All species identified in this study were potentially pathogenic.