Extensively drug-resistant tuberculosis

Cotreatment With Clofazimine and Rapamycin Eliminates Drug-Resistant Tuberculosis by Inducing Polyfunctional Central Memory T-Cell Responses

Mycobacterium tuberculosis, the causative agent of tuberculosis, is acquiring drug resistance at a faster rate than the discovery of new antibiotics. Therefore, alternate therapies that can limit the drug resistance and disease recurrence are urgently needed. Emerging evidence indicates that combined treatment with antibiotics and an immunomodulator provides superior treatment efficacy. Clofazimine (CFZ) enhances the generation of T central memory (TCM) cells by blocking the Kv1.3+ potassium channels. Rapamycin (RAPA) facilitates M. tuberculosis clearance by inducing autophagy. In this study, we observed that cotreatment with CFZ and RAPA potently eliminates both multiple and extensively drug-resistant (MDR and XDR) clinical isolates of M. tuberculosis in a mouse model by inducing robust T-cell memory and polyfunctional TCM responses. Furthermore, cotreatment reduces the expression of latency-associated genes of M. tuberculosis in human macrophages. Therefore, CFZ and RAPA cotherapy holds promise for treating patients infected with MDR and XDR strains of M. tuberculosis.

ClpC2 protects mycobacteria against a natural antibiotic targeting ClpC1-dependent protein degradation

Mycobacterium tuberculosis Clp proteases are targeted by several antitubercular compounds, including cyclomarin A (CymA). CymA exerts its toxicity by binding to AAA + chaperone ClpC1. Here, we show that CymA can also bind a partial homologue of ClpC1, known as ClpC2, and we reveal the molecular basis of these interactions by determining the structure of the M. tuberculosis ClpC2:CymA complex. Furthermore, we show deletion of clpC2 in Mycobacterium smegmatis increases sensitivity to CymA. We find CymA exposure leads to a considerable upregulation of ClpC2 via a mechanism in which binding of CymA to ClpC2 prevents binding of ClpC2 to its own promoter, resulting in upregulation of its own transcription in response to CymA. Our study reveals that ClpC2 not only senses CymA, but that through this interaction it can act as a molecular sponge to counteract the toxic effects of CymA and possibly other toxins targeting essential protease component ClpC1 in mycobacteria.

The pncA gene mutations of Mycobacterium tuberculosis in multidrug-resistant tuberculosis

The pncA gene encodes pyrazinamidase enzyme which converts drug pyrazinamide to active form pyrazinoic acid, but mutations in this gene can prevent enzyme activity which leads to pyrazinamide resistance. The cross-sectional study was carried out during 2016-2017 for 12 months. The purpose of the study was to detect mutation at codon 12 and codon 85 in the pncA gene in local multidrug-resistant tuberculosis (MDR-TB) patients by developing a simple molecular test so that disease could be detected timely in the local population. DNA extracted from sputum-cultured samples from MDR-TB patients and subjected to semi-multiplex allele-specific PCR by using self-designed primers against the pncA gene. Among 75 samples, 53 samples were subjected to molecular analysis based on purified DNA quantity and quality. The primers produced 250 and 480 bp fragments, indicating the mutations at codon 12 (aspartate to alanine) and codon 85 (leucine to proline) respectively. MDR-TB was more common in the age group 21-40 years. Fifty-seven percent of samples (n = 30) were found positive for pncA mutations, whereas 43% of samples (n = 23) showed negative results. Thirteen percent of samples (n = 4) had mutations at codon 12 in which aspartate was converted to alanine, and they produced an amplified product of 480 bp. Eighty-seven percent of samples (n = 26) had mutations at codon 85 in which leucine was converted to proline and amplified product size was 250 bp. The mutations were simple nucleotide substitutions. The prevalence of mutations in which leucine was substituted by proline was higher than the mutations in which aspartate was substituted by alanine. A high prevalence of substitution mutation (CTG → CCG; leucine to proline) was detected in MDR-TB cases. Earlier detection of MDR-TB via an effective molecular diagnostic method can control the MDR tuberculosis spread in the population.

Performance of GenoType MTBDRsl assay for detection of second-line drugs and ethambutol resistance directly from sputum specimens of MDR-TB patients in Bangladesh

Background

Rapid and early detection of drug susceptibility among multidrug-resistant tuberculosis (MDR-TB) patients could guide the timely initiation of effective treatment and reduce transmission of drug-resistant TB. In the current study, we evaluated the diagnostic performance of GenoType MTBDRsl (MTBDRsl) ver1.0 assay for detection of resistance to ofloxacin (OFL), kanamycin (KAN) and ethambutol (EMB), and additionally the XDR-TB among MDR-TB patients in Bangladesh.

Methods

The MTBDRsl assay was performed directly on 218 smear-positive sputum specimens collected from MDR-TB patients and the results were compared with the phenotypic drug susceptibility testing (DST) performed on solid Lowenstein-Jensen (L-J) media. We also analyzed the mutation patterns of gyrA, rrs, and embB genes for detection of resistance to OFL, KAN and EMB, respectively.

Results

The sensitivity and specificity of the MTBDRsl compared to phenotypic L-J DST were 81.8% (95% CI, 69.1–90.9) and 98.8% (95% CI, 95.6–99.8), respectively for OFL (PPV: 95.7% & NPV: 94.1%); 65.1% (95% CI, 57.5–72.2) and 86.7% (95% CI, 73.2–94.9), respectively for EMB (PPV: 94.9% & NPV: 39.4%); and 100% for KAN. The diagnostic accuracy of KAN, OFL and EMB were 100, 94.5 and 69.6%, respectively. Moreover, the sensitivity, specificity and diagnostic accuracy of MtBDRsl for detection of XDR-TB was 100%. The most frequently observed mutations were at codon D94G (46.8%) of gyrA gene, A1401G (83.3%) of rrs gene, and M306V (41.5%) of the embB gene.

Conclusion

Considering the excellent performance in this study we suggest that MTBDRsl assay can be used as an initial rapid test for detection of KAN and OFL susceptibility, as well as XDR-TB directly from smear-positive sputum specimens of MDR-TB patients in Bangladesh.

Phototherapy and optical waveguides for the treatment of infection

With rapid emergence of multi-drug resistant microbes, it is imperative to seek alternative means for infection control. Optical waveguides are an auspicious delivery method for precise administration of phototherapy. Studies have shown that phototherapy is promising in fighting against a myriad of infectious pathogens (i.e. viruses, bacteria, fungi, and protozoa) including biofilm-forming species and drug-resistant strains while evading treatment resistance. When administered via optical waveguides, phototherapy can treat both superficial and deep-tissue infections while minimizing off-site effects that afflict conventional phototherapy and pharmacotherapy. Despite great therapeutic potential, exact mechanisms, materials, and fabrication designs to optimize this promising treatment option are underexplored. This review outlines principles and applications of phototherapy and optical waveguides for infection control. Research advances, challenges, and outlook regarding this delivery system are rigorously discussed in a hope to inspire future developments of optical waveguide-mediated phototherapy for the management of infection and beyond.

Prevalence of Drug-Resistant Tuberculosis in Sudan: A Systematic Review and Meta-Analysis

Drug-resistant tuberculosis (DR-TB) is still one of the most critical issues impeding worldwide TB control efforts. The aim of this systematic review and meta-analysis was to give an updated picture of the prevalence of DR-TB in Sudan. A comprehensive systematic search was performed on four electronic databases (PubMed, Scopus, Web of Science and Google Scholar) to identify all published studies reporting prevalence data of DR-TB in Sudan. Sixteen eligible studies published during 2002-2020 were included. Using meta-analysis of proportions, the pooled prevalence of TB cases with resistance to any anti-TB drugs was 47.0% (95% CI: 35.5-58.6%). The overall prevalence of mono, multi, poly and extensive drug resistance were estimated to be 16.2% (95% CI: 9.0-23.4%), 22.8% (95% CI: 16.0-29.7%), 6.8% (95% CI: 0.5-13.0%) and 0.7% (95% CI: 0-2.1%), respectively. Considering any first-line anti-TB drugs, the resistance prevalence was highest for isoniazid (32.3%) and streptomycin (31.7%), followed by rifampicin (29.2%). In contrast, resistance against second-line drugs was reported for only two antibiotics, namely, ofloxacin (2.1%) and kanamycin (0.7%). Of note, the resistance profile of the previously treated patients was found to be remarkably high compared with the newly diagnosed TB patients. The relatively high prevalence estimation of anti-TB drug resistance warrants strengthening TB control and treatment strategies in Sudan.

In vitro and in vivo evaluation of clastogenicity of second-line antitubercular drug loaded PLGA nanoparticles

Sustained release nanoformulations of second line antitubercular drugs levofloxacin and ethionamide had shown promise in pharmacokinetics and acute and sub-acute toxicity studies. The present study evaluated the clastogenicity potential of the nanoformulations of these antitubercular agents. Clastogenicity was evaluated by (a) in vitro micronucleus assay (b) in vivo micronucleus assay in Swiss albino mice and (c) sister chromatid exchange (SCE) in CHO cell lines. Ethionamide and levofloxacin loaded nanoparticles were 312 ± 64 nm and 245 ± 24 nm in size respectively and drug encapsulation was 35.2 ± 3.1% w/w and 45.6 ± 9.4% w/w, respectively. The frequency of MN-NCE/1000 NCE and MN-PCE/1000 PCE were significantly reduced in mice treated with ethionamide nanoparticle (3.5 ± 0.9, 13.8 ± 16.68) and levofloxacin nanoparticles (5.6 ± 2.7, 16.7 ± 12.7) compared to the mice treated with free ethionamide (11.5 ± 4.1, p = 0.23 and 45.19 ± 19.21, p = 0.38) and free levofloxacin (14.7 ± 1.88, p < 0.0001 and 54.6 ± 18.1, p = 0.0017), respectively. For in vitro, micronucleus assay frequencies of micronuclei per thousand bi-nucleated cells (MN-BN/1000 BN) was 188.3 ± 20.20 and 148 ± 20.42 for ethionamide and levofloxacin nanoparticles as compared to 232.6 ± 16.04 (p = 0.52) and 175 ± 5.56 (p = 0.45) for free ethionamide and levofloxacin, respectively. The average number of SCE per cell for nanoformulation of ethionamide were not different from that of free drug (4.9 ± 0.51 vs 4.1 ± 0.55, p = 0.86). The SCE per cells were not significant difference for nanoformulation of levofloxacin (2.33 ± 1.36 vs 5.46 ± 0.25, p = 0.88). In vitro and in vivo assays have shown relatively less clastogenic potential of equivalent dose of ethionamide nanoparticles as compared to the conventional formulation.

Drug resistant Tuberculosis: A review

Tuberculosis (TB) was announced as a global emergency in 1993. There was an alarming counter attack of TB worldwide. However, when it was known that TB can be cured completely, the general public became ignorant towards the infection. The pathogenic organism Mycobacterium tuberculosis continuously evolved to resist the antagonist drugs. This has led to the outbreak of resistant strain that gave rise to "Multi Drug Resistant-Tuberculosis" and "Extensively Drug Resistant Tuberculosis" that can still be cured with a lower success rate. While the mechanism of resistance proceeds further, it ultimately causes unmanageable totally drug resistant TB (TDR-TB). Studying the molecular mechanisms underlying the resistance to drugs would help us grasp the genetics and pathophysiology of the disease. In this review, we present the molecular mechanisms behind Mycobacterium tolerance to drugs and their approach towards the development of multi-drug resistant, extremely drug resistant and totally drug resistant TB.

Structure based identification of first-in-class fragment inhibitors that target the NMN pocket of M. tuberculosis NAD+-dependent DNA ligase A

NAD⁺-dependent DNA ligase (LigA) is the essential replicative ligase in bacteria and differs from ATP-dependent counterparts like the human DNA ligase I (HligI) in several aspects. LigA uses NAD⁺ as the co-factor while the latter uses ATP. Further, the LigA carries out enzymatic activity with a single divalent metal ion in the active site while ATP-dependent ligases use two metal ions. Instead of the second metal ion, LigA have a unique NMN binding subdomain that facilitates the orientation of the β-phosphate and NMN leaving group. LigA are therefore attractive targets for new anti-bacterial therapeutic development. Others and our group have earlier identified several LigA inhibitors that mainly bind to AMP binding site of LigA. However, no inhibitor is known to bind to the unique NMN binding subdomain. We initiated a fragment inhibitor discovery campaign against the M. tuberculosis LigA based on our co-crystal structure of adenylation domain with AMP and NMN. The study identified two fragments, 4-(4-fluorophenyl)-4,5,6,7-tetrahydro-3H imidazo[4,5-c] pyridine and N-(4-methylbenzyl)-1H-pyrrole-2-carboxamide, that bind to the NMN site. The fragments inhibit LigA with IC₅₀ of 16.9 and 28.7 µM respectively and exhibit MIC of ~20 and 60 µg/ml against a temperature sensitive E. coli GR501 ligA^ts strain, rescued by MtbLigA. Co-crystal structures of the fragments with the adenylation domain of LigA show that they mimic the interactions of NMN. Overall, our results suggest that the NMN binding-site is a druggable target site for developing anti-LigA therapeutic strategies.

Evidence for Expanding the Role of Streptomycin in the Management of Drug-Resistant Mycobacterium tuberculosis

In 2019, the WHO tuberculosis (TB) treatment guidelines were updated to recommend only limited use of streptomycin, in favor of newer agents or amikacin as the preferred aminoglycoside for drug-resistant Mycobacterium tuberculosis However, the emergence of resistance to newer drugs, such as bedaquiline, has prompted a reanalysis of antitubercular drugs in search of untapped potential. Using 211 clinical isolates of M. tuberculosis from South Africa, we performed phenotypic drug susceptibility testing (DST) to aminoglycosides by both critical concentration and MIC determination in parallel with whole-genome sequencing to identify known genotypic resistance elements. Isolates with low-level streptomycin resistance mediated by gidB were frequently misclassified with respect to streptomycin resistance when using the WHO-recommended critical concentration of 2 μg/ml. We identified 29 M. tuberculosis isolates from South Africa with low-level streptomycin resistance concomitant with high-level amikacin resistance, conferred by gidB and rrs 1400, respectively. Using a large global data set of M. tuberculosis genomes, we observed 95 examples of this corresponding resistance genotype (gidB-rrs 1400), including identification in 81/257 (31.5%) of extensively drug resistant (XDR) isolates. In a phylogenetic analysis, we observed repeated evolution of low-level streptomycin and high-level amikacin resistance in multiple countries. Our findings suggest that current critical concentration methods and the design of molecular diagnostics need to be revisited to provide more accurate assessments of streptomycin resistance for gidB-containing isolates. For patients harboring isolates of M. tuberculosis with high-level amikacin resistance conferred by rrs 1400, and for whom newer agents are not available, treatment with streptomycin may still prove useful, even in the face of low-level resistance conferred by gidB.

HPLC-DAD and UHPLC/QTOF-MS Analysis of Polyphenols in Extracts of the African Species Combretum padoides, C. zeyheri and C. psidioides Related to Their Antimycobacterial Activity

Combretum padoides Engl. & Diels, C. psidioides Welv. and C. zeyheri Sond. are used forthe treatment of infections and tuberculosis related symptoms in African traditional medicine. In orderto verify these uses, extracts were screened for their growth inhibitory eects against M. smegmatisATCC 14468. Ultra-high pressure liquid chromatography coupled to quadrupole time-of-flightmass spectrometry (UHPLC/QTOF-MS) and GC-MS were used to investigate the polyphenoliccomposition in the active extracts. The lowest minimum inhibitory concentration (MIC), 625 g/mL,was shown by a methanol extract of the stem bark of C. psidioides. A butanol extract of C. psidioidesgave large inhibition zone diameters (IZD 21 mm) and inhibited 84% of the mycobacterial growthat 312 g/mL. Combretastatin B-2 and dihydrostilbene derivatives were present in the methanolextract of C. psidioides, whereas the butanol extract of this species contained punicalagin, corilagin,and sanguiin H-4. Methanol and butanol extracts of the stem bark of C. padoides gave large inhibitionzone diameters (IZD 26.5 mm) and MIC values of 1250 and 2500 g/mL, respectively. C. padoidescontained an ellagitannin with a mass identical to punicalagin ([M-H]- 1083.0587) and a corilaginlike derivative ([M-H]- 633.0750) as well as ellagic acid arabinoside and methyl ellagic acid xyloside.A butanol extract of the roots of C. zeyheri showed mild antimycobacterial activity and containeda gallotannin at m/z [M-H]- 647.0894 as the main compound along with punicalagin and threeunknown ellagitannins at m/z [M-H]- 763.0788, 765.0566, and 817.4212. Our results indicate thatthe studied species of Combretum contain phenolic and polyphenolic compounds with possiblepotential as leads for antimycobacterial drugs or as adjuvants for conventional anti-TB drugs.

Multi-functionalized nanocarriers targeting bacterial reservoirs to overcome challenges of multi drug-resistance

INTRODUCTION

Infectious diseases associated with intracellular bacteria such as Staphylococcus aureus, Salmonella typhimurium and Mycobacterium tuberculosis are important public health concern. Emergence of multi and extensively drug-resistant bacterial strains have made it even more obstinate to offset such infections. Bacteria residing within intracellular compartments provide additional barriers to effective treatment.

METHOD

Information provided in this review has been collected by accessing various electronic databases including Google scholar, Web of science, Scopus, and Nature index. Search was performed using keywords nanoparticles, intracellular targeting, multidrug resistance, Staphylococcus aureus; Salmonella typhimurium; Mycobacterium tuberculosis. Information gathered was categorized into three major sections as 'Intracellular targeting of Staphylococcus aureus, Intracellular targeting of Salmonella typhimurium and Intracellular targeting of Mycobacterium tuberculosis' using variety of nanocarrier systems.

RESULTS

Conventional management for infectious diseases typically comprises of long-term treatment with a combination of antibiotics, which may lead to side effects and decreased patient compliance. A wide range of multi-functionalized nanocarrier systems have been studied for delivery of drugs within cellular compartments where bacteria including Staphylococcus aureus, Salmonella typhimurium and Mycobacterium tuberculosis reside. Such carrier systems along with targeted delivery have been utilized for sustained and controlled delivery of drugs. These strategies have been found useful in overcoming the drawbacks of conventional treatments including multi-drug resistance.

CONCLUSION

Development of multi-functional nanocargoes encapsulating antibiotics that are proficient in targeting and releasing drug into infected reservoirs seems to be a promising strategy to circumvent the challenge of multidrug resistance. Graphical abstract.

Adverse drug reaction prevalence and mechanisms of action of first-line anti-tubercular drugs

PURPOSE

Understanding the appearance of anti-tubercular drug-related adverse drug reactions (ADRs) in patients receiving tuberculosis (TB) treatment is important, and may be related to morbidity and mortality if not recognized early. Here, we aimed to characterize the mechanisms underlying adverse drug reactions due to combination anti-tuberculosis therapy of the Revised National Tuberculosis Control Program (RNTCP).

METHODS

This was a prospective observational study conducted in 9 DOTS centers of New Delhi, India. All enrolled TB patients receiving first-line tuberculosis treatment as per RNTCP guidelines were monitored for ADRs. All ADRs that appeared during the treatment were recorded and analyzed.

RESULTS

The study included 1011 TB patients on anti-TB treatment under DOTS. According to Naranjo's probability scale, of a total 351 (34.72%) reported adverse events, 102 (10.09%) were definite, 59 (5.83%) probable, 123 (12.17%) possible, and 67 (6.63%) doubtful. On the Hartwig severity scale, of the 351 adverse drug events, 225 (22.26%) were mild, 105 (10.38%) were moderate, and 21 (2.08%) were severe. Out of 102 reported adverse drug reactions, 81 (79.41%) were moderate and 21 (20.59%), while 65.28% did not experience any ADRs.

CONCLUSIONS

Directly Observed Treatment (DOT) is effective and safe compared to daily treatment regimens. Patients receiving DOTS therapy needed close monitoring for adverse events. Therefore, a pharmacovigilance program should be added at the National level to accesses the adverse event incidence.

A novel derivative of the fungal antimicrobial peptide plectasin is active against Mycobacterium tuberculosis

Tuberculosis has been reaffirmed as the infectious disease causing most deaths in the world. Co-infection with HIV and the increase in multi-drug resistant Mycobacterium tuberculosis strains complicate treatment and increases mortality rates, making the development of new drugs an urgent priority. In this study we have identified a promising candidate by screening antimicrobial peptides for their capacity to inhibit mycobacterial growth. This non-toxic peptide, NZX, is capable of inhibiting both clinical strains of M. tuberculosis and an MDR strain at therapeutic concentrations. The therapeutic potential of NZX is further supported in vivo where NZX significantly lowered the bacterial load with only five days of treatment, comparable to rifampicin treatment over the same period. NZX possesses intracellular inhibitory capacity and co-localizes with intracellular bacteria in infected murine lungs. In conclusion, the data presented strongly supports the therapeutic potential of NZX in future anti-TB treatment.

Understanding molecular consequences of putative drug resistant mutations in Mycobacterium tuberculosis

Genomic studies of Mycobacterium tuberculosis bacteria have revealed loci associated with resistance to anti-tuberculosis drugs. However, the molecular consequences of polymorphism within these candidate loci remain poorly understood. To address this, we have used computational tools to quantify the effects of point mutations conferring resistance to three major anti-tuberculosis drugs, isoniazid (n = 189), rifampicin (n = 201) and D-cycloserine (n = 48), within their primary targets, katG, rpoB, and alr. Notably, mild biophysical effects brought about by high incidence mutations were considered more tolerable, while different structural effects brought about by haplotype combinations reflected differences in their functional importance. Additionally, highly destabilising mutations such as alr Y388, highlighted a functional importance of the wildtype residue. Our qualitative analysis enabled us to relate resistance mutations onto a theoretical landscape linking enthalpic changes with phenotype. Such insights will aid the development of new resistance-resistant drugs and, via an integration into predictive tools, in pathogen surveillance.

Evolution of drug resistance in Mycobacterium tuberculosis: a review on the molecular determinants of resistance and implications for personalized care

Drug-resistant TB (DR-TB) remains a significant challenge in TB treatment and control programmes worldwide. Advances in sequencing technology have significantly increased our understanding of the mechanisms of resistance to anti-TB drugs. This review provides an update on advances in our understanding of drug resistance mechanisms to new, existing drugs and repurposed agents. Recent advances in WGS technology hold promise as a tool for rapid diagnosis and clinical management of TB. Although the standard approach to WGS of Mycobacterium tuberculosis is slow due to the requirement for organism culture, recent attempts to sequence directly from clinical specimens have improved the potential to diagnose and detect resistance within days. The introduction of new databases may be helpful, such as the Relational Sequencing TB Data Platform, which contains a collection of whole-genome sequences highlighting key drug resistance mutations and clinical outcomes. Taken together, these advances will help devise better molecular diagnostics for more effective DR-TB management enabling personalized treatment, and will facilitate the development of new drugs aimed at improving outcomes of patients with this disease.

Pulmonary resection in the treatment of multidrug-resistant tuberculosis: A case series

Multidrug-resistant (MDR) and extensive drug-resistant (XDR) tuberculosis (TB) are significant health problems throughout the world. Although the main treatment is medical, adjunctive surgical resection may increase the chance of cure in selected patients with MDR-TB or XDR-TB. This study aimed to present a case series of patients who underwent surgical resection for MDR-TB.Between March 2008 and November 2011, surgical resection was performed on 54 patients including 34 with MDR-TB and 20 with XDR-TB at the Departments of Surgery of Shanghai Public Health Clinical Center (Shanghai), Henan Chest Hospital (Henan), and Anhui Chest Hospital (Henan). Preoperative sputum smear samples were positive for 28 patients and sputum quantitative polymerase chain reaction was positive for 32. Patients were treated according to a standard therapy protocol for a mean of 4.2 months before the operation. The variables that affected treatment outcomes were identified through multivariate regression analysis.Fifty-four patients were operated for MDR-TB with localized disease usually complicated by cavity formation or destroyed lung. Thirty-seven were males and 17 were females. Median age was 37.8 (range, 20-75) years. Lobectomy was performed in 46 patients and pneumonectomy in 8. Muscle flaps were used in 36 of the patients with lobectomy and 8 with pneumonectomy. Various complications occurred in 6 (11.1%) patients, including bronchopleural fistula in 1 patient, bleeding in 2 patients, and prolonged air leak in 2 patients. A favorable outcome was achieved in 47 patients (87%) who underwent surgical resection. Higher body mass index (BMI) was associated with better outcome (odds ratio = 0.537, 95% confidence interval: 0.310-0.928, P = .026).Patients with MDR-TB had good treatment outcomes after adjunctive pulmonary resection, and with few complications. Higher BMI was related to a favorable outcome.

Formulation, stabilisation and encapsulation of bacteriophage for phage therapy

Against a backdrop of global antibiotic resistance and increasing awareness of the importance of the human microbiota, there has been resurgent interest in the potential use of bacteriophages for therapeutic purposes, known as phage therapy. A number of phage therapy phase I and II clinical trials have concluded, and shown phages don't present significant adverse safety concerns. These clinical trials used simple phage suspensions without any formulation and phage stability was of secondary concern. Phages have a limited stability in solution, and undergo a significant drop in phage titre during processing and storage which is unacceptable if phages are to become regulated pharmaceuticals, where stable dosage and well defined pharmacokinetics and pharmacodynamics are de rigueur. Animal studies have shown that the efficacy of phage therapy outcomes depend on the phage concentration (i.e. the dose) delivered at the site of infection, and their ability to target and kill bacteria, arresting bacterial growth and clearing the infection. In addition, in vitro and animal studies have shown the importance of using phage cocktails rather than single phage preparations to achieve better therapy outcomes. The in vivo reduction of phage concentration due to interactions with host antibodies or other clearance mechanisms may necessitate repeated dosing of phages, or sustained release approaches. Modelling of phage-bacterium population dynamics reinforces these points. Surprisingly little attention has been devoted to the effect of formulation on phage therapy outcomes, given the need for phage cocktails, where each phage within a cocktail may require significantly different formulation to retain a high enough infective dose. This review firstly looks at the clinical needs and challenges (informed through a review of key animal studies evaluating phage therapy) associated with treatment of acute and chronic infections and the drivers for phage encapsulation. An important driver for formulation and encapsulation is shelf life and storage of phage to ensure reproducible dosages. Other drivers include formulation of phage for encapsulation in micro- and nanoparticles for effective delivery, encapsulation in stimuli responsive systems for triggered controlled or sustained release at the targeted site of infection. Encapsulation of phage (e.g. in liposomes) may also be used to increase the circulation time of phage for treating systemic infections, for prophylactic treatment or to treat intracellular infections. We then proceed to document approaches used in the published literature on the formulation and stabilisation of phage for storage and encapsulation of bacteriophage in micro- and nanostructured materials using freeze drying (lyophilization), spray drying, in emulsions e.g. ointments, polymeric microparticles, nanoparticles and liposomes. As phage therapy moves forward towards Phase III clinical trials, the review concludes by looking at promising new approaches for micro- and nanoencapsulation of phages and how these may address gaps in the field.

Development of Protein-Protein Interaction Inhibitors for the Treatment of Infectious Diseases

Protein-protein interaction (PPI) inhibitors are a rapidly expanding class of therapeutics. Recent advances in our understanding of PPIs and success of early examples of PPI inhibitors demonstrate the feasibility of targeting PPIs. This review summarizes the techniques used for the discovery and optimization of a diverse set PPI inhibitors, focusing on the development of PPI inhibitors as new antibacterial and antiviral agents. We close with a summary of the advances responsible for making PPI inhibitors realistic targets for therapeutic intervention and brief outlook of the field.

Therapy of Multidrug-Resistant and Extensively Drug-Resistant Tuberculosis

The global epidemic of multidrug-resistant tuberculosis (MDR-TB) caused by Mycobacterium tuberculosis strains resistant to at least isoniazid and rifampin was recently reported as larger than previously estimated, with at least 580,000 new cases reported in 2015. Extensively drug-resistant tuberculosis (XDR-TB), MDR-TB with additional resistance to a second-line fluoroquinolone and injectable, continues to account for nearly 10% of MDR cases globally. Cases in India, China, and the Russian Federation account for >45% of the cases of MDR-TB. Molecular testing helps identify MDR more quickly, and treatment options have expanded across the globe. Despite this, only 20% are in treatment, and treatment is challenging due to the toxicity of medications and the long duration. In 2016 the World Health Organization updated guidelines for the treatment of MDR-TB. A new short-course regimen is an option for those who qualify. Five effective drugs, including pyrazinamide (PZA) when possible, are recommended during the initial treatment phase and four drugs thereafter. Revised drug classifications include the use of linezolid and clofazimine as key second-line drugs and the option to use bedaquiline and delamanid to complete a five-drug regimen when needed due to poor medication tolerance or extensive resistance. Despite multiple drugs and long-duration treatment regimens, the outcomes for MDR and especially XDR-TB are much worse than for drug-susceptible disease. Better management of toxicity, prevention of transmission, and identification and appropriate management of infected contacts are important challenges for the future.

Repurposing clinically approved cephalosporins for tuberculosis therapy

While modern cephalosporins developed for broad spectrum antibacterial activities have never been pursued for tuberculosis (TB) therapy, we identified first generation cephalosporins having clinically relevant inhibitory concentrations, both alone and in synergistic drug combinations. Common chemical patterns required for activity against Mycobacterium tuberculosis were identified using structure-activity relationships (SAR) studies. Numerous cephalosporins were synergistic with rifampicin, the cornerstone drug for TB therapy, and ethambutol, a first-line anti-TB drug. Synergy was observed even under intracellular growth conditions where beta-lactams typically have limited activities. Cephalosporins and rifampicin were 4- to 64-fold more active in combination than either drug alone; however, limited synergy was observed with rifapentine or rifabutin. Clavulanate was a key synergistic partner in triple combinations. Cephalosporins (and other beta-lactams) together with clavulanate rescued the activity of rifampicin against a rifampicin resistant strain. Synergy was not due exclusively to increased rifampicin accumulation within the mycobacterial cells. Cephalosporins were also synergistic with new anti-TB drugs such as bedaquiline and delamanid. Studies will be needed to validate their in vivo activities. However, the fact that cephalosporins are orally bioavailable with good safety profiles, together with their anti-mycobacterial activities reported here, suggest that they could be repurposed within new combinatorial TB therapies.

The potential role of trimethoprim-sulfamethoxazole in the treatment of drug-resistant tuberculosis

Tuberculosis (TB) remains a serious public health threat worsened by emerging drug resistance. Mycobacterium tuberculosis has become resistant not only to front-line drugs but also to second-line antimicrobials directed at drug-resistant TB. Renewed efforts are devoted for the development of new antibiotics active against TB. Also, repurposing of other antibiotics is being explored to shorten the time to develop new drugs against M. tuberculosis. As a result, trimethoprim-sulfamethoxazole (SXT) has emerged as a potential new option to treat drug-resistant TB. SXT has been found to be surprisingly active against drug-resistant M. tuberculosis, not only in vitro but also in vivo. The potential role of SXT for the treatment of multidrug resistant/extensively drug resistant TB might be explored in further clinical evaluations.

Molecular Basis of Drug Resistance in Mycobacterium tuberculosis

In this chapter we review the molecular mechanisms of drug resistance to the major first- and second-line antibiotics used to treat tuberculosis.

The challenge of managing extensively drug-resistant tuberculosis at a referral hospital in the state of São Paulo, Brazil: a report of three cases

Here, we report the cases of three patients diagnosed with extensively drug-resistant tuberculosis and admitted to a referral hospital in the state of São Paulo, Brazil, showing the clinical and radiological evolution, as well as laboratory test results, over a one-year period. Treatment was based on the World Health Organization guidelines, with the inclusion of a new proposal for the use of a combination of antituberculosis drugs (imipenem and linezolid). In the cases studied, we show the challenge of creating an acceptable, effective treatment regimen including drugs that are more toxic, are more expensive, and are administered for longer periods. We also show that treatment costs are significantly higher for such patients, which could have an impact on health care systems, even after hospital discharge. We highlight the fact that in extreme cases, such as those reported here, hospitalization at a referral center seems to be the most effective strategy for providing appropriate treatment and increasing the chance of cure. In conclusion, health professionals and governments must make every effort to prevent cases of multidrug-resistant and extensively drug-resistant tuberculosis.

Evolution of Extensively Drug-Resistant Tuberculosis over Four Decades: Whole Genome Sequencing and Dating Analysis of Mycobacterium tuberculosis Isolates from KwaZulu-Natal

BACKGROUND

The continued advance of antibiotic resistance threatens the treatment and control of many infectious diseases. This is exemplified by the largest global outbreak of extensively drug-resistant (XDR) tuberculosis (TB) identified in Tugela Ferry, KwaZulu-Natal, South Africa, in 2005 that continues today. It is unclear whether the emergence of XDR-TB in KwaZulu-Natal was due to recent inadequacies in TB control in conjunction with HIV or other factors. Understanding the origins of drug resistance in this fatal outbreak of XDR will inform the control and prevention of drug-resistant TB in other settings. In this study, we used whole genome sequencing and dating analysis to determine if XDR-TB had emerged recently or had ancient antecedents.

METHODS AND FINDINGS

We performed whole genome sequencing and drug susceptibility testing on 337 clinical isolates of Mycobacterium tuberculosis collected in KwaZulu-Natal from 2008 to 2013, in addition to three historical isolates, collected from patients in the same province and including an isolate from the 2005 Tugela Ferry XDR outbreak, a multidrug-resistant (MDR) isolate from 1994, and a pansusceptible isolate from 1995. We utilized an array of whole genome comparative techniques to assess the relatedness among strains, to establish the order of acquisition of drug resistance mutations, including the timing of acquisitions leading to XDR-TB in the LAM4 spoligotype, and to calculate the number of independent evolutionary emergences of MDR and XDR. Our sequencing and analysis revealed a 50-member clone of XDR M. tuberculosis that was highly related to the Tugela Ferry XDR outbreak strain. We estimated that mutations conferring isoniazid and streptomycin resistance in this clone were acquired 50 y prior to the Tugela Ferry outbreak (katG S315T [isoniazid]; gidB 130 bp deletion [streptomycin]; 1957 [95% highest posterior density (HPD): 1937-1971]), with the subsequent emergence of MDR and XDR occurring 20 y (rpoB L452P [rifampicin]; pncA 1 bp insertion [pyrazinamide]; 1984 [95% HPD: 1974-1992]) and 10 y (rpoB D435G [rifampicin]; rrs 1400 [kanamycin]; gyrA A90V [ofloxacin]; 1995 [95% HPD: 1988-1999]) prior to the outbreak, respectively. We observed frequent de novo evolution of MDR and XDR, with 56 and nine independent evolutionary events, respectively. Isoniazid resistance evolved before rifampicin resistance 46 times, whereas rifampicin resistance evolved prior to isoniazid only twice. We identified additional putative compensatory mutations to rifampicin in this dataset. One major limitation of this study is that the conclusions with respect to ordering and timing of acquisition of mutations may not represent universal patterns of drug resistance emergence in other areas of the globe.

CONCLUSIONS

In the first whole genome-based analysis of the emergence of drug resistance among clinical isolates of M. tuberculosis, we show that the ancestral precursor of the LAM4 XDR outbreak strain in Tugela Ferry gained mutations to first-line drugs at the beginning of the antibiotic era. Subsequent accumulation of stepwise resistance mutations, occurring over decades and prior to the explosion of HIV in this region, yielded MDR and XDR, permitting the emergence of compensatory mutations. Our results suggest that drug-resistant strains circulating today reflect not only vulnerabilities of current TB control efforts but also those that date back 50 y. In drug-resistant TB, isoniazid resistance was overwhelmingly the initial resistance mutation to be acquired, which would not be detected by current rapid molecular diagnostics employed in South Africa that assess only rifampicin resistance.

From many deaths to some few cases of drug-resistant tuberculosis: travelling with the systems quality improvement model in Lacs Health District, Togo

The ultimate goal of every tuberculosis (TB) treatment program is a high treatment success rate. Treatment success is extremely important because, when the rate is high, it significantly contributes to declining numbers of new cases by reducing the number and period of infectious cases, TB morbidity and mortality, and prevents the emergence of resistant strains. Our aim was to decrease TB mortality by increasing pulmonary TB patients’ treatment success rate to at least 85 % in Lacs Health District by end of July 2014.

A systems and dialogic analysis of the public health system related to TB patients’ treatment revealed that it was not performing well; we found weak coverage and quality of TB services, a poorly-functioning TB health information system, poor-performing health workforce, poor availability of HIV tests and antiretroviral for TB patients, and low degree of patients’ participation in their care. We redesigned the system to correct those weaknesses. The effectiveness of these changes was monitored using plan, do, study, act (PDSA) cycles. We increased TB patient success rate from 80% to 95% between February 2012 and July 2014.The mortality rate dropped from 13% to 3% and the failure to follow-up rate dropped from 3% to 2%.

In conclusion, district health systems performance depends on factors such as the closeness of services to population; skilled workforce; the ability to collect and analyze data and use information for action; population empowerment, and good management and improvement capabilities of management team especially the public health director. High TB patients’ success rate depends also on the availability of antiretroviral drugs. It is highly important that every district health management team member develops improvement capabilities.

Fast and efficient detection of tuberculosis antigens using liposome encapsulated secretory proteins of Mycobacterium tuberculosis

PURPOSE

A rapid and efficient diagnostic test was developed for the detection of Mycobacterium tuberculosis antigens in serum samples of active tuberculosis (TB) and extrapulmonary TB patients via a liposomal agglutination-based method.

METHODS

A rapid card test has been developed to facilitate the recognition of high-affinity binding rabbit raised purified culture filtrate protein antibodies coupled on the surface of activated liposomal preparation. In the presence of TB antigens, the polyclonal antibodies bound to the liposomal particles demonstrate a visible agglutination reaction.

RESULTS

The developed assay was simple, rapid, reliable, sensitive, and specific as a diagnostic test for the detection of antigens in serum samples of clinically confirmed cases of TB within 4-5 minutes' duration. The test was evaluated at different hospitals, medical colleges, and pathology centers, and involved 1483 participants. This investigation was conducted to detect the presence of these antigens during the period of active growth of the microorganism in serum samples for pulmonary TB and processed tissue biopsy for other extrapulmonary TB. Results obtained using this test were compared with acid-fast bacilli smear and culture results.

CONCLUSION

Our study demonstrated that the newly developed liposome tuberculosis antigen card test detected antigens in our study population with approximately 97.48% sensitivity and 95.79% specificity. This is the first study to report the liposomal encapsulation of culture filtrate proteins from M. tuberculosis for diagnostic application.

Genome Analysis of the First Extensively Drug-Resistant (XDR) Mycobacterium tuberculosis in Malaysia Provides Insights into the Genetic Basis of Its Biology and Drug Resistance

The outbreak of extensively drug-resistant tuberculosis (XDR-TB) has become an increasing problem in many TB-burdened countries. The underlying drug resistance mechanisms, including the genetic variation favored by selective pressure in the resistant population, are partially understood. Recently, the first case of XDR-TB was reported in Malaysia. However, the detailed genotype family and mechanisms of the formation of multiple drugs resistance are unknown. We sequenced the whole genome of the UM 1072388579 strain with a 2-kb insert-size library and combined with that from previously sequenced 500-bp-insert paired-end reads to produce an improved sequence with maximal sequencing coverage across the genome. In silico spoligotyping and phylogenetic analyses demonstrated that UM 1072388579 strain belongs to an ancestral-like, non-Beijing clade of East Asia lineage. This is supported by the presence of a number of lineage-specific markers, including fadD28, embA, nuoD and pks7. Polymorphism analysis showed that the drug-susceptibility profile is correlated with the pattern of resistance mutations. Mutations in drug-efflux pumps and the cell wall biogenesis pathway such as mmpL, pks and fadD genes may play an important role in survival and adaptation of this strain to its surrounding environment. In this work, fifty-seven putative promoter SNPs were identified. Among them, we identified a novel SNP located at -4 T allele of TetR/acrR promoter as an informative marker to recognize strains of East Asian lineage. Our work indicates that the UM 1072388579 harbors both classical and uncommon SNPs that allow it to escape from inhibition by many antibiotics. This study provides a strong foundation to dissect the biology and underlying resistance mechanisms of the first reported XDR M. tuberculosis in Malaysia.

Development of genetically engineered iNKT cells expressing TCRs specific for the M. tuberculosis 38-kDa antigen

Introduction

The invariant natural killer T (iNKT) cell has been shown to play a central role in early stages immune responses against Mycobacterium tuberculosis (Mtb) infection, which become nonresponsive (anergic) and fails to control the growth of Mtb in patients with active tuberculosis. Enhancement of iNKT cell responses to Mtb antigens can help to resist infection.

Study design and methods

In the present study, an Mtb 38-kDa antigen-specific T cell receptor (TCR) was isolated from human CD8⁺ T cells stimulated by 38-kDa antigen in vitro, and then transduced into primary iNKT cells by retrovirus vector.

Results

The TCR gene-modified iNKT cells are endowed with new features to behave as a conventional MHC class I restricted CD8⁺ T lymphocyte by displaying specific antigen recognition and anti-Mtb antigen activity in vitro. At the same time, the engineered iNKT cells retaining its original capacity to be stimulated proliferation by non-protein antigens α-Gal-Cer.

Conclusions

This work is the first attempt to engineer iNKT cells by exogenous TCR genes and demonstrated that iNKT cell, as well as CD4⁺ and CD8⁺ T cells, can be genetically engineered to confer them a defined and alternative specificity, which provides new insights into TCR gene therapy for tuberculosis patients, especially those infected with drug-resistant Mtb.

The Mycobacterium tuberculosis ClpP1P2 Protease Interacts Asymmetrically with Its ATPase Partners ClpX and ClpC1

Clp chaperone-proteases are cylindrical complexes built from ATP-dependent chaperone rings that stack onto a proteolytic ClpP double-ring core to carry out substrate protein degradation. Interaction of the ClpP particle with the chaperone is mediated by an N-terminal loop and a hydrophobic surface patch on the ClpP ring surface. In contrast to E. coli, Mycobacterium tuberculosis harbors not only one but two ClpP protease subunits, ClpP1 and ClpP2, and a homo-heptameric ring of each assembles to form the ClpP1P2 double-ring core. Consequently, this hetero double-ring presents two different potential binding surfaces for the interaction with the chaperones ClpX and ClpC1. To investigate whether ClpX or ClpC1 might preferentially interact with one or the other double-ring face, we mutated the hydrophobic chaperone-interaction patch on either ClpP1 or ClpP2, generating ClpP1P2 particles that are defective in one of the two binding patches and thereby in their ability to interact with their chaperone partners. Using chaperone-mediated degradation of ssrA-tagged model substrates, we show that both Mycobacterium tuberculosis Clp chaperones require the intact interaction face of ClpP2 to support degradation, resulting in an asymmetric complex where chaperones only bind to the ClpP2 side of the proteolytic core. This sets the Clp proteases of Mycobacterium tuberculosis, and probably other Actinobacteria, apart from the well-studied E. coli system, where chaperones bind to both sides of the protease core, and it frees the ClpP1 interaction interface for putative new binding partners.

Tricyclic dihydrobenzoxazepine and tetracyclic indole derivatives can specifically target bacterial DNA ligases and can distinguish them from human DNA ligase I

DNA ligases are critical components for DNA metabolism in all organisms.

Antibiotic resistance: what, why, where, when and how?

BACKGROUND

Antibiotic resistance is a threat to the effective prevention and treatment of an ever-increasing range of infections caused by bacteria, parasites, viruses and fungi.

SOURCES OF DATA

Peer-reviewed journal articles, governmental and professional society publications.

AREAS OF AGREEMENT AND CONTROVERSY

There is consensus about the development and spread of antibiotic resistance, the reasons for the development of antibiotic resistance and the clinical impact. There is more debate about the most appropriate way of tackling this increasing problem.

GROWING POINTS

This review discusses a number of initiatives (local and global) that are being undertaken to protect the antibiotics we currently have available for use and to encourage the development of newer agents.

Shaping the CD4+ memory immune response against tuberculosis: the role of antigen persistence, location and multi-functionality

Abstract Effective vaccination against intracellular pathogens, such as tuberculosis (TB), relies on the generation and maintenance of CD4 memory T cells. An incomplete understanding of the memory immune response has hindered the rational design of a new, more effective TB vaccine. This review discusses how the persistence of antigen, the location of memory cells, and their multifunctional ability shape the CD4 memory T cell response against TB.

Mycobacterium tuberculosis adhesins: potential biomarkers as anti-tuberculosis therapeutic and diagnostic targets

Adhesion to host cells is a precursor to host colonization and evasion of the host immune response. Conversely, it triggers the induction of the immune response, a process vital to the host’s defence against infection. Adhesins are microbial cell surface molecules or structures that mediate the attachment of the microbe to host cells and thus the host–pathogen interaction. They also play a crucial role in bacterial aggregation and biofilm formation. In this review, we discuss the role of adhesins in the pathogenesis of the aetiological agent of tuberculosis, Mycobacterium tuberculosis. We also provide insight into the structure and characteristics of some of the characterized and putative M. tuberculosis adhesins. Finally, we examine the potential of adhesins as targets for the development of tuberculosis control strategies.

Genome analysis of 17 extensively drug-resistant strains reveals new potential mutations for resistance

We report the whole-genome sequence of an extensively drug-resistant (XDR) tuberculosis (TB) strain of Latin American-Mediterranean (LAM) lineage. This strain is phenotypically resistant to aminoglycosides, but carries no related mutations in rrs, tlyA, and eis. Through genome analysis comparison with 16 XDR strains, we found 218 non-synonymous single nucleotide polymorphisms (SNPs) shared that could confer resistance.

Substrate delivery by the AAA+ ClpX and ClpC1 unfoldases activates the mycobacterial ClpP1P2 peptidase

Mycobacterial Clp-family proteases function via collaboration of the heteromeric ClpP1P2 peptidase with a AAA+ partner, ClpX or ClpC1. These enzymes are essential for M. tuberculosis viability and are validated antibacterial drug targets, but the requirements for assembly and regulation of functional proteolytic complexes are poorly understood. Here, we report the reconstitution of protein degradation by mycobacterial Clp proteases in vitro and describe novel features of these enzymes that distinguish them from orthologues in other bacteria. Both ClpX and ClpC1 catalyse ATP-dependent unfolding and degradation of native protein substrates in conjunction with ClpP1P2, but neither mediates protein degradation with just ClpP1 or ClpP2. ClpP1P2 alone has negligible peptidase activity, but is strongly stimulated by translocation of protein substrates into ClpP1P2 by either AAA+ partner. Interestingly, our results support a model in which both binding of a AAA+ partner and protein-substrate delivery are required to stabilize active ClpP1P2. Our model has implications for therapeutically targeting ClpP1P2 in dormant M. tuberculosis, and our reconstituted systems should facilitate identification of novel Clp protease inhibitors and activators.

Reduced virulence of an extensively drug-resistant outbreak strain of Mycobacterium tuberculosis in a murine model

Bacterial drug resistance is often associated with a fitness cost. Large outbreaks of multidrug-resistant (MDR) and extensively drug-resistant (XDR) TB have been described that predominately affect persons with HIV infection. We obtained four closely-related Mycobacterium tuberculosis strains (genotype F15/LAM4/KZN) from an outbreak in KwaZulu-Natal (KZN), South Africa, including drug-sensitive, MDR, and XDR clinical isolates. We compared the virulence of these strains in a murine model of aerosol M. tuberculosis infection for four phenotypes: (1) competitive in vivo growth in lung and spleen, (2) non-competitive in vivo growth in lung and spleen, (3) murine survival time, and (4) lung pathology. When mixtures of sensitive, MDR, and XDR KZN strains were aerosolized (competitive model), lung CFUs were similar at 60 days after infection, and spleen CFUs were ordered as follows: sensitive > MDR > XDR. When individual strains were aerosolized (non-competitive model), modest differences in lung and spleen CFUs were observed with the same ordering. C57BL/6, C3H/FeJ, and SCID mice all survived longer after infection with MDR as compared to sensitive strains. SCID mice infected with an XDR strain survived longer than those infected with MDR or sensitive strains. Lung pathology was reduced after XDR TB infection compared to sensitive or MDR TB infection. In summary, increasing degrees of drug resistance were associated with decreasing murine virulence in this collection of KZN strains as measured by all four virulence phenotypes. The predominance of HIV-infected patients in MDR and XDR TB outbreaks may be explained by decreased virulence of these strains in humans.

Airborne antituberculosis activity of Eucalyptus citriodora essential oil

The rapid emergence of multi- and extensively drug-resistant tuberculosis (MDR/XDR-TB) has created a pressing public health problem, which mostly affects regions with HIV/AIDS prevalence and represents a new constraint in the already challenging disease management of tuberculosis (TB). The present work responds to the need to reduce the number of contagious MDR/XRD-TB patients, protect their immediate environment, and interrupt the rapid spread by laying the groundwork for an inhalation therapy based on anti-TB-active constituents of the essential oil (EO) of Eucalyptus citriodora. In order to address the metabolomic complexity of EO constituents and active principles in botanicals, this study applied biochemometrics, a 3-D analytical approach that involves high-resolution CCC fractionation, GC-MS analysis, bioactivity measurements, and chemometric analysis. Thus, 32 airborne anti-TB-active compounds were identified in E. citriodora EO: the monoterpenes citronellol (1), linalool (3), isopulegol (5), and α-terpineol (7) and the sesquiterpenoids spathulenol (11), β-eudesmol (23), and τ-cadinol (25). The impact of the interaction of multiple components in EOs was studied using various artificial mixtures (AMxs) of the active monoterpenes 1, 2, and 5 and the inactive eucalyptol (33). Both neat 1 and the AMx containing 1, 2, and 33 showed airborne TB inhibition of >90%, while the major E. citriodora EO component, 2, was only weakly active, at 18% inhibition.

The role of healthcare strategies in controlling antibiotic resistance

In an interview in March 2013, the Chief Medical Officer described antibiotic resistance as a 'ticking time bomb' and ranked it along with terrorism on a list of threats to the nation. Her report Infections and the Rise of Antimicrobial Resistance (Department of Health, 2011) highlighted that, while a new infectious disease has been discovered nearly every year over the past three decades, there have been very few new antibiotics developed, leaving our armoury nearly empty. Antibiotic resistance is a universal problem that needs to be tackled by a wide variety of strategies and players. Our approach to tackling resistance to antibiotic agents must therefore also be dynamic. As well as reducing environmental use, we also need to lower antibiotic use in the healthcare setting. Healthcare workers have a huge role to play in combating antibiotic resistance. This article focuses on several issues related to antibiotic resistance, including antibiotic modes of action and the properties that confer resistance on bacteria. It includes information on antibiotic usage and describes current healthcare strategies we can adopt to help reduce the development of resistance.

Biochemical characterization of Mycobacterium tuberculosis IMP dehydrogenase: kinetic mechanism, metal activation and evidence of a cooperative system

Proposed kinetic mechanism forMtIMPDH in the presence of K⁺.

Risk factors for extensively drug-resistant tuberculosis: a review

INTRODUCTION

Extensively drug-resistant tuberculosis (XDR-TB) is emerging as a global public health problem. Its treatment is more expensive and difficult, and the outcomes much severe. The identification of risk factors for XDR-TB is of paramount importance to design effective TB control strategies.

OBJECTIVE

To review published articles on risk factors for XDR-TB.

METHODS

We identified 249 English articles on PubMed, and 182 were excluded by the abstract. The remaining articles were retrieved for full-text detailed evaluation by authors, and 27 relevant articles were selected for final review.

RESULTS

Some risk factors were consistently present, mainly previous TB treatment and its length. Other conditions often associated were immigration, alcoholism and HIV coinfection. Pre-XDR-TB points to an increased risk of XDR-TB.

CONCLUSION

The information regarding determinants of XDR-TB is relatively weak. However, special emphasis should be given to minimize the risks of TB retreatment to prevent the emergence of highly resistant TB.

Light based anti-infectives: ultraviolet C irradiation, photodynamic therapy, blue light, and beyond

Owing to the worldwide increase in antibiotic resistance, researchers are investigating alternative anti-infective strategies to which it is supposed microorganisms will be unable to develop resistance. Prominent among these strategies, is a group of approaches which rely on light to deliver the killing blow. As is well known, ultraviolet light, particularly UVC (200-280 nm), is germicidal, but it has not been much developed as an anti-infective approach until recently, when it was realized that the possible adverse effects to host tissue were relatively minor compared to its high activity in killing pathogens. Photodynamic therapy is the combination of non-toxic photosensitizing dyes with harmless visible light that together produce abundant destructive reactive oxygen species (ROS). Certain cationic dyes or photosensitizers have good specificity for binding to microbial cells while sparing host mammalian cells and can be used for treating many localized infections, both superficial and even deep-seated by using fiber optic delivered light. Many microbial cells are highly sensitive to killing by blue light (400-470 nm) due to accumulation of naturally occurring photosensitizers such as porphyrins and flavins. Near infrared light has also been shown to have antimicrobial effects against certain species. Clinical applications of these technologies include skin, dental, wound, stomach, nasal, toenail and other infections which are amenable to effective light delivery.

Contributions of culture and antimicrobial susceptibility tests to the retreatment of patients with pulmonary tuberculosis

INTRODUCTION

This study evaluated the efficacy of retreatment of pulmonary tuberculosis (TB) with regard to treatment outcomes and antimicrobial susceptibility testing (ST) profiles.

METHODS

This retrospective cohort study analyzed 144 patients treated at a referral hospital in Brazil. All of them had undergone prior treatment, were smear-positive for TB and received a standardized retreatment regimen. Fisher’s 2-tailed exact test and the χ² test were used; RRs and 95% CIs were calculated using univariate and multivariate binary logistic regression.

RESULTS

The patients were cured in 84 (58.3%) cases. Failure was associated with relapsed treatment and abandonment (n=34). Culture tests were obtained for 103 (71.5%) cases; 70 (48.6%) had positive results. ST results were available for 67 (46.5%) cases; the prevalence of acquired resistance was 53.7%. There were no significant differences between those who achieved or not therapeutic success (p=0.988), despite being sensitive or resistant to 1 or more drugs. Rifampicin resistance was independently associated with therapeutic failure (OR: 4.4, 95% CI:1.12-17.37, p=0.034). For those cases in which cultures were unavailable, a 2nd model without this information was built. In this, return after abandonment was significantly associated with retreatment failure (OR: 3.59, 95% CI:1.17-11.06, p=0.026).

CONCLUSIONS

In this cohort, the general resistance profile appeared to have no influence on treatment outcome, except in cases of rifampicin resistance. The form of reentry was another independent predictor of failure. The use of bacterial culture identification and ST in TB management must be re-evaluated. The recommendations for different susceptibility profiles must also be improved.