Extensively drug-resistant tuberculosis in sub-Saharan Africa: an emerging public-health concern

Cycles of antibiotic use and emergent antimicrobial resistance in the South African tuberculosis programme (1950-2021): A scoping review and critical reflections on stewardship

The emergent threat of antimicrobial resistance (AMR) has resulted in debates around the use and preservation of effective antimicrobials. Concerns around AMR reflect a history of increasing dependence on antibiotics to address disease epidemics rooted in profound structural and systemic challenges. In the context of global health, this process, often referred to as pharmaceuticalisation, has commonly occurred within disease programmes, of which lessons are vital for adding nuance to conversations around antimicrobial stewardship. Tuberculosis (TB) is a notable example. A disease which accounts for one-third of AMR globally and remains the leading cause of death from a single infectious agent in many low - and middle-income countries, including South Africa. In this scoping review, we chart TB science in South Africa over 70 years of programming. We reviewed published manuscripts about the programme and critically reflected on the implications of our findings for stewardship. We identified cycles of programmatic responses to new drug availability and the emergence of drug resistance, which intersected with cycles of pharmaceuticalisation. These cycles reflect the political, economic, and social factors influencing programmatic decision-making. Our analysis offers a starting point for research exploring these cycles and drawing out implications for stewardship across the TB and AMR communities.

Multidrug-resistant tuberculosis during pregnancy and adverse birth outcomes: a systematic review and meta-analysis

BACKGROUND

Multidrug-resistant tuberculosis (MDR-TB) is a major global public health concern. However, there is a dearth of literature on whether MDR-TB and its medications impact maternal and perinatal outcomes, and when such evidence exists the findings are conflicting.

OBJECTIVES

This systematic review and meta-analysis aimed to examine the impact of MDR-TB and its medications during pregnancy on maternal and perinatal outcomes.

SEARCH STRATEGY

PubMed, Scopus and Web of Science databases were searched from earliest to February 2020.

SELECTION CRITERIA

Records were screened based on pre-defined selection criteria and assessed for quality by two independent reviewers.

DATA COLLECTION AND ANALYSIS

A meta-analysis was performed using the random effects model to calculate pooled prevalence for each outcome.

MAIN RESULTS

Of the 72 records identified, 12 were included in the systematic review and meta-analysis, consisting of 174 pregnant women with MDR-TB and 110 adverse outcomes. Maternal death, pregnancy loss, preterm birth and low birthweight were the most common maternal and perinatal adverse outcomes reported in the studies. The overall pooled prevalence was 7.5% (95% CI 3.2-12.8) for maternal death, 10.6% (95% CI 6.0-16.3) for pregnancy loss, 12.9% (95% CI 0.0-38.0) for preterm birth and 23.7% (95% CI 17.0-31.0) for low birthweight.

CONCLUSIONS

The findings suggest that MDR-TB is associated with a high risk of adverse maternal and perinatal outcomes, but these should be interpreted cautiously because the evidence is largely preliminary. Adequately powered prospective cohort studies are urgently required to corroborate these findings.

TWEETABLE ABSTRACT

Multidrug-resistant tuberculosis may increase the risk of adverse maternal and perinatal outcomes.

Advances in Studies on Prevalence and Interaction Mechanism of Acquired Immunodeficiency Syndrome and Tuberculosis Coinfection

Human immunodeficiency virus (HIV) and tuberculosis (TB) coinfection is a serious public health problem. HIV and TB promote each other, accelerating development of HIV to acquired immunodeficiency syndrome (AIDS) and heightening TB mortality. Determining interaction mechanism between HIV andMycobacterium tuberculosiscan lead to development of effective treatments. This study summarizes prevalence status of AIDS and TB coinfection and research advances concerning their interaction mechanism.

In vitro susceptibility of Mycobacterium tuberculosis to extracts of Eucalyptus camaldulensis and Eucalyptus torelliana and isolated compounds

CONTEXT

Eucalyptus camaldulensis Dehnh. (Myrtaceae) and Eucalyptus torelliana F. Muell are used in Nigerian traditional medicine for the treatment of cough associated with tuberculosis (TB) and other respiratory infections.

OBJECTIVE

Hexane, chloroform, methanol extracts, and isolated compounds of E. camaldulensis and E. torelliana were screened for activity against Mycobacterium tuberculosis H37Rv (MtbH37Rv) to authenticate the traditional use of these plants.

MATERIALS AND METHODS

The microplate alamar blue assay (MABA) method was used to investigate the anti-M. tuberculosis activities. Bioassay-guided fractionation of the hexane extract of E. torelliana leaf was performed, and isolated compounds were characterized by MS, 1D- and 2D-NMR.

RESULTS

The extracts inhibited the growth of MtbH37Rv [minimum inhibitory concentration (MIC) 4-64 µg/mL]. Spectroscopic characterization led to the identification of two compounds, hydroxymyristic acid methylester (1) and a substituted pyrenyl ester, a sterol (2). Compounds 1 and 2 had MIC of 49.45 and 46.99 µg/mL; IC(50) >100 and 38.21 µg/mL; selectivity index (SI) >2.02 and 0.81, respectively, and a minimum bactericidal concentration (MBC) of 62.50 µg/mL.

DISCUSSION AND CONCLUSIONS

The anti-TB activities of these plants on M. tuberculosis H37Rv support their use in traditional medicine for the treatment of coughs associated with TB and reveals the presence of anti-Mtb active compounds in the plants. These findings not only demonstrate a new potential area of therapeutic value of E. camaldulensis and E. torelliana, but also illustrate the role of esters as anti-Mtb active principles in ethnobotanical preparations and as lead compounds in the development of new and effective anti-Mtb drugs.

Assessing tuberculosis case fatality ratio: a meta-analysis

Background

Recently, the tuberculosis (TB) Task Force Impact Measurement acknowledged the need to review the assumptions underlying the TB mortality estimates published annually by the World Health Organization (WHO). TB mortality is indirectly measured by multiplying estimated TB incidence with estimated case fatality ratio (CFR). We conducted a meta-analysis to estimate the TB case fatality ratio in TB patients having initiated TB treatment.

Methods

We searched for eligible studies in the PubMed and Embase databases through March 4^th 2011 and by reference listing of relevant review articles. Main analyses included the estimation of the pooled percentages of: a) TB patients dying due to TB after having initiated TB treatment and b) TB patients dying during TB treatment. Pooled percentages were estimated using random effects regression models on the combined patient population from all studies.

Main Results

We identified 69 relevant studies of which 22 provided data on mortality due to TB and 59 provided data on mortality during TB treatment. Among HIV infected persons the pooled percentage of TB patients dying due to TB was 9.2% (95% Confidence Interval (CI): 3.7%–14.7%) and among HIV uninfected persons 3.0% (95% CI: −1.2%–7.4%) based on the results of eight and three studies respectively providing data for this analyses. The pooled percentage of TB patients dying during TB treatment was 18.8% (95% CI: 14.8%–22.8%) among HIV infected patients and 3.5% (95% CI: 2.0%–4.92%) among HIV uninfected patients based on the results of 27 and 19 studies respectively.

Conclusion

The results of the literature review are useful in generating prior distributions of CFR in countries with vital registration systems and have contributed towards revised estimates of TB mortality This literature review did not provide us with all data needed for a valid estimation of TB CFR in TB patients initiating TB treatment.

Cameroonian medicinal plants: pharmacology and derived natural products

Many developing countries including Cameroon have mortality patterns that reflect high levels of infectious diseases and the risk of death during pregnancy and childbirth, in addition to cancers, cardiovascular diseases and chronic respiratory diseases that account for most deaths in the developed world. Several medicinal plants are used traditionally for their treatment. In this review, plants used in Cameroonian traditional medicine with evidence for the activities of their crude extracts and/or derived products have been discussed. A considerable number of plant extracts and isolated compounds possess significant antimicrobial, anti-parasitic including antimalarial, anti-proliferative, anti-inflammatory, anti-diabetes, and antioxidant effects. Most of the biologically active compounds belong to terpenoids, phenolics, and alkaloids. Terpenoids from Cameroonian plants showed best activities as anti-parasitic, but rather poor antimicrobial effects. The best antimicrobial, anti-proliferative, and antioxidant compounds were phenolics. In conclusion, many medicinal plants traditionally used in Cameroon to treat various ailments displayed good activities in vitro. This explains the endeavor of Cameroonian research institutes in drug discovery from indigenous medicinal plants. However, much work is still to be done to standardize methodologies and to study the mechanisms of action of isolated natural products.

Tuberculosis: what we don't know can, and does, hurt us

Mycobacterium tuberculosis has a penetrance of its host population that would be the envy of most human pathogens. About one-third of the human population would have a positive skin test for the infection and is thus thought to harbor the bacterium. Globally, 22 "high-burden" countries account for more than 80% of the active tuberculosis cases in the world, which shows the inequitable distribution of the disease. There is no effective vaccine against infection, and current drug therapies are fraught with problems, predominantly because of the protracted nature of the treatment and the increasing occurrence of drug resistance. Here we focus on the biology of the host-pathogen interaction and discuss new and evolving strategies for intervention.

Early treatment outcomes and HIV status of patients with extensively drug-resistant tuberculosis in South Africa: a retrospective cohort study

BACKGROUND

Data from Kwazulu Natal, South Africa, suggest that almost all patients with extensively drug-resistant (XDR) tuberculosis are HIV-positive, with a fatal outcome. Since, there are few data for the treatment-related outcomes of XDR tuberculosis in settings with a high HIV prevalence, we investigated the associations of these diseases in such settings to formulate recommendations for control programmes.

METHODS

In a retrospective cohort study, we analysed the case records of patients (>16 years old) with XDR tuberculosis (culture-proven at diagnosis) between August, 2002, and February, 2008, at four designated provincial treatment facilities in South Africa. We used Cox proportional hazards regression models to assess risk factors associated with the outcomes-mortality and culture conversion.

FINDINGS

195 of 227 patients were analysed. 21 died before initiation of any treatment, and 174 patients (82 with HIV infection) were treated. 62 (36%) of these patients died during follow-up. The number of deaths was not significantly different in patients with or without HIV infection: 34 (41%) of 82 versus 28 (30%) of 92 (p=0.13). Treatment with moxifloxacin (hazard ratio 0.11, 95% CI 0.01-0.82; p=0.03), previous culture-proven multidrug-resistant tuberculosis (5.21, 1.93-14.1; p=0.001), and number of drugs used in a regimen (0.59, 0.45-0.78, p<0.0001) were independent predictors of death. Fewer deaths occurred in patients with HIV infection given highly active antiretroviral therapy than in those who were not (0.38, 0.18-0.80; p=0.01). 33 (19%) of 174 patients showed culture conversion, of which 23 (70%) converted within 6 months of initiation of treatment.

INTERPRETATION

In South Africa, patients with XDR tuberculosis, a substantial proportion of whom are not infected with HIV, have poor management outcomes. Nevertheless, survival in patients with HIV infection is better than previously reported. The priorities for the country are still prevention of XDR tuberculosis, and early detection and management of multidrug-resistant and XDR tuberculosis through strengthened programmes and laboratory capacity.

FUNDING

South African Medical Research Council, European Union Framework 7 program, and European Developing Countries Clinical Trials Partnership.

Extensively drug-resistant tuberculosis treatment outcome in Iran: a case series of seven patients

BACKGROUND

Extensively drug-resistant tuberculosis (XDR-TB) has recently been identified as a major threat to global health. XDR-TB poses a risk of higher failure rates and death during TB treatment. We report herein the outcomes of XDR-TB in patients treated with the standardized regimen in Iran.

PATIENTS AND METHODS

Between 2002 and 2006, seven patients were diagnosed with XDR-TB. All patients were treated with the standardized second-line regimen containing cycloserine, prothionamide, amikacin, and ofloxacin. First-line drugs, such as ethambutol and pyrazinamide, were added to the regimen if drug susceptibility testing showed sensitivity to these drugs.

RESULTS

Four (57.1%) patients were male. All seven patients were HIV-negative. The patient age range was 22-79 years. Of the seven cases, the final outcome was 'cure' in two (28.6%), 'relapse' in one, 'treatment failure' in one, and 'death' in two; the outcome for one patient was unknown.

CONCLUSION

Our study shows a poor prognosis in patients with XDR-TB. This indicates the necessity of detecting XDR-TB cases earlier, as well as the need to gain access to more second-line agents. This is particularly important in resource-limited settings in order to administer individualized regimens.

Doomsday postponed? Preventing and reversing epidemics of drug-resistant tuberculosis

Extensively drug-resistant (XDR) strains of Mycobacterium tuberculosis, now known to be present in 50 countries, heighten the threat posed by untreatable and fatal human tuberculosis (TB). To combat epidemics of drug-resistant TB, it is vital to understand why some resistant strains have greater reproductive fitness--a greater propensity to spread--than drug-susceptible strains. If public health malpractice has been a more important determinant of reproductive success than genetic mechanisms, then improved diagnosis and treatment could keep the frequency of resistant strains among TB cases low in any population. Recent data suggest that national TB control programmes that use existing drugs efficiently can postpone and even reverse epidemics of multidrug-resistant TB, although the effect of such programmes on XDR strains remains largely unknown.

The potential of South African plants against Mycobacterium infections

ETHNOPHARMACOLOGICAL RELEVANCE

In South Africa, tuberculosis (TB) caused by Mycobacterium tuberculosis is the most commonly notified disease and the fifth largest cause of mortality, with one in ten cases of TB resistant to treatment in some areas. Many plants are used locally in traditional medicine to treat TB-related symptoms.

AIM OF THE STUDY

The aim was to summarize currently available knowledge on South African plants used to treat TB symptoms, and antimycobacterial efficacy of plant-derived extracts and compounds.

MATERIALS AND METHODS

The traditional uses of plants for respiratory ailments and TB were collated and tabulated. The antimycobacterial activity tests of extracts and chemical constituents of several of these plants and others using different methods and target organisms were summarized.

RESULTS

Almost 180 plants used for TB-related symptoms in South African traditional medicine were documented. About 30% of these have been tested for antimycobacterial efficacy, mostly against fast-growing, non-pathogenic Mycobacterium species.

CONCLUSIONS

Many plant species are used in traditional South African medicine to alleviate symptoms of TB, and several interesting leads have originated for further inquiry following in vitro antimycobacterial activity evaluation. However, much work remains to be done on the systematic assessment of anti-TB efficacy of local plants against pathogenic Mycobacterium species, both in vitro and in vivo.

Importance of improved TB diagnostics in addressing the extensively drug-resistant TB crisis

There is an urgent need for new, rapid diagnostics to stem the tide of multidrug-resistant (MDR) and extensively drug-resistant (XDR) TB. Current identification and detection of resistance for the majority of Mycobacteria, including Mycobacterium tuberculosis, require weeks and multiple methodologies to complete. The sheer number and variety of tests required often exceeds the capacity of many laboratories. Current strategies center on improvement of existing tests and development of novel ones. Ultimately, what is needed is a single, rapid, diagnostic for identification and determination of drug resistance in M. tuberculosis. Such a method should be capable of detecting antibiotic resistance for all first- and second-line agents irrespective of the genetic mechanism of resistance. Detection should be achievable directly from clinical specimens. Yet, improved diagnostics are only part of a larger solution. Such a solution must include a comprehensive approach in which careful consideration is given to each particular setting relative to local resources and overall burden of disease. Such an approach is essential for the future of TB control and stemming the tide of MDR-TB and XDR-TB.

Epidemiology and treatment of multidrug resistant tuberculosis

Multidrug resistant tuberculosis is now thought to afflict between 1 and 2 million patients annually. Although significant regional variability in the distribution of disease has been recorded, surveillance data are limited by several factors. The true burden of disease is likely underestimated. Nevertheless, the estimated burden is substantial enough to warrant concerted action. A range of approaches is possible, but all appropriate interventions require scale-up of laboratories and early treatment with regimens containing a sufficient number of second-line drugs. Ambulatory treatment for most patients, and improved infection control, can facilitate scale-up with decreased risk of nosocomial transmission. Several obstacles have been considered to preclude worldwide scale-up of treatment, mostly attributable to inadequate human, drug, and financial resources. Further delays in scale-up, however, risk continued generation and transmission of resistant tuberculosis, as well as associated morbidity and mortality.