A Review Of Host-Specific Diagnostic And Surrogate Biomarkers In Children With Pulmonary Tuberculosis.

BACKGROUND: Tuberculosis (TB) is one of the most common causes of mortality globally with a steady rise in paediatric cases in the past decade. Laboratory methods of diagnosing TB and monitoring response to treatment have limitations. Current research focuses on interrogating host- and/or pathogen-specific biomarkers to address this problem. METHODS: We reviewed the literature on host-specific biomarkers in TB to determine their value in diagnosis and treatment response in TB infected and HIV/TB co-infected children on anti-tuberculosis treatment. RESULTS AND CONCLUSION: While no single host-specific biomarker has been identified for diagnosis or treatment responses in children, several studies suggest predictive biosignatures for disease activity. Alarmingly, current data on host-specific biomarkers for diagnosing and assessing anti-tuberculosis treatment in TB/HIV co-infected children is inadequate. Various factors affecting host-specific biomarker responses should be considered in interpreting findings and designing future studies within specific clinical settings.

A computational method for the prediction and functional analysis of potential Mycobacterium tuberculosis adhesin-related proteins.

OBJECTIVES: Mycobacterial adherence plays a major role in the establishment of infection within the host. Adhesin-related proteins attach to host receptors and cell-surface components. The current study aimed to utilize in-silico strategies to determine the adhesin potential of conserved hypothetical (CH) proteins. METHODS: Computational analysis was performed on the whole Mycobacterium tuberculosis H37Rv proteome using a software program for the prediction of adhesin and adhesin-like proteins using neural networks (SPAAN) to determine the adhesin potential of CH proteins. A robust pipeline of computational analysis tools: Phyre2 and pFam for homology prediction; Mycosub, PsortB, and Loctree3 for subcellular localization; SignalP-5.0 and SecretomeP-2.0 for secretory prediction, were utilized to identify adhesin candidates. RESULTS: SPAAN revealed 776 potential adhesins within the whole MTB H37Rv proteome. Comprehensive analysis of the literature was cross-tabulated with SPAAN to verify the adhesin prediction potential of known adhesin (n = 34). However, approximately a third of known adhesins were below the probability of adhesin (Pad) threshold (Pad ≥0.51). Subsequently, 167 CH proteins of interest were categorized using essential in-silico tools. CONCLUSION: The use of SPAAN with supporting in-silico tools should be fundamental when identifying novel adhesins. This study provides a pipeline to identify CH proteins as functional adhesin molecules.

M. tuberculosis curli pili (MTP) is associated with alterations in carbon, fatty acid and amino acid metabolism in a THP-1 macrophage infection model.

The initial host-pathogen interaction is crucial for the establishment of infection. An improved understanding of the pathophysiology of Mycobacterium tuberculosis (M. tuberculosis) during macrophage infection can aid the development of intervention therapeutics against tuberculosis. M. tuberculosis curli pili (MTP) is a surface located adhesin, involved in the first point-of-contact between pathogen and host. This study aimed to better understand the role of MTP in modulating the intertwined metabolic pathways of M. tuberculosis and its THP-1 macrophage host. Metabolites were extracted from pelleted wet cell mass of THP-1 macrophages infected with M. tuberculosis wild-type V9124 (WT), Δmtp-deletion mutant and the mtp-complemented strains, respectively, via a whole metabolome extraction method using a 1:3:1 ratio of chloroform:methanol:water. Metabolites were detected by two-dimensional gas chromatography time-of-flight mass spectrometry. Significant metabolites were determined through univariate and multivariate statistical tests and online pathway databases. Relative to the WT, a total of nine and ten metabolites were significantly different in the Δmtp and complement strains, respectively. All nine significant metabolites were found in elevated levels in the Δmtp relative to the WT. Additionally, of the ten significant metabolites, eight were detected in lower levels and two were detected in higher levels in the complement relative to the WT. The absence of the MTP adhesin resulted in reduced virulence of M. tuberculosis leading to alterations in metabolites involved in carbon, fatty acid and amino acid metabolism during macrophage infection, suggesting that MTP plays an important role in the modulation of host metabolic activity. These findings support the prominent role of the MTP adhesin as a virulence factor as well as a promising biomarker for possible diagnostic and therapeutic intervention.

Mycobacterium tuberculosis strains induce strain-specific cytokine and chemokine response in pulmonary epithelial cells.

M. tuberculosis F15/LAM4/KZN has been associated with high transmission rates of drug resistant tuberculosis in the KwaZulu-Natal province of South Africa. The current study elucidated the cytokine/chemokine responses induced by representatives of the F15/LAM4/KZN and other dominant strain families in pulmonary epithelial cells. Multiplex cytokine analyses were performed at 24, 48 and 72h post infection of the A549 pulmonary epithelial cell line with the F15/LAM4/KZN, F28, F11, Beijing, Unique and H37Rv strains at an MOI of ∼10:1. Twenty-three anti- and pro-inflammatory cytokines/chemokines were detected at all-time intervals. Significantly high concentrations of IL-6, IFN-γ, TNF-α and G-CSF at 48h, and IL-8, IFN-γ, TNF-α, G-CSF and GM-CSF at 72h, were induced by the F28 and F15/LAM4/KZN strains, respectively. Lower levels of cytokines/chemokines were induced by either the Beijing or Unique strains at all three time intervals. All strains induced up-regulation of pathogen recognition receptors (PRRs) (TLR3 and TLR5) while only the F15/LAM4/KZN, F11 and F28 strains induced significant differential expression of TLR2 compared to the Beijing, Unique and H37Rv strains. The low induction of cytokines in epithelial cells by the Beijing strain correlates with its previously reported hypervirulent properties. High concentrations of cytokines and chemokines required for early protection against M. tuberculosis infections induced by the F15/LAM4/KZN and F28 strains suggests a lower virulence of these genotypes compared to the Beijing strain. These findings demonstrate the high diversity in host cytokine/chemokine response to early infection of pulmonary epithelial cells by different strains of M. tuberculosis.

Bacterial pili, with emphasis on Mycobacterium tuberculosis curli pili: potential biomarkers for point-of care tests and therapeutics.

CONTEXT: Novel biomarkers are essential for developing rapid diagnostics and therapeutic interventions Objective: This review aimed to highlight biomarker characterisation and assessment of unique bacterial pili. METHODS: A PubMed search for bacterial pili, diagnostics, vaccine and therapeutics was performed, with emphasis on the well characterised pili. RESULTS: In total, 46 papers were identified and reviewed. CONCLUSION: Extensive analyses of pili enabled by advanced nanotechnology and whole genome sequencing provide evidence that they are strong biomarker candidates. Mycobacterium tuberculosis curli pili are emphasised as important epitopes for the development of much needed point-of-care diagnostics and therapeutics.

Pili of Mycobacterium tuberculosis: current knowledge and future prospects.

Many pathogenic bacteria express filamentous appendages, termed pili, on their surface. These organelles function in several important bacterial processes, including mediating bacterial interaction with, and colonization of the host, signalling events, locomotion, DNA uptake, electric conductance, and biofilm formation. In the last decade, it has been established that the tuberculosis-causing bacterium, Mycobacterium tuberculosis, produces two pili types: curli and type IV pili. In this paper, we review studies on M. tuberculosis pili, highlighting their structure and biological significance to M. tuberculosis pathogenesis, and discuss their potential as targets for therapeutic intervention and diagnostic test development.

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.

The role of interferon gamma release assays in the monitoring of response to anti-tuberculosis treatment in children.

Successful control of childhood TB requires early diagnosis, effective chemotherapy and a method of evaluating the response to therapy. Identification of suitable biomarkers that predict the response to anti-TB therapy may allow the duration of treatment to be shortened. The majority of biomarker studies in paediatric TB have focused on the role of T cell-based interferon-gamma (IFN-γ) release assays (IGRAs) in the diagnosis of either latent or active disease. Little has been published on the role of IGRAs in the monitoring response to therapy in children. We reviewed the available literature to ascertain the value of IGRAs in the monitoring of response to anti-TB therapy in children. We explored the results of the few studies that have investigated the role of IGRAs as markers of response to anti-TB treatment in children. We conclude that the role of IGRAs as surrogate markers appears promising. Robust clinical trials are, however, needed to entrench the value of IGRAs as surrogate biomarkers of response to anti-TB therapy in children.

Pili contribute to biofilm formation in vitro in Mycobacterium tuberculosis.

Organized bacterial communities, or biofilms, provide an important reservoir for persistent cells that are inaccessible or tolerant to antibiotics. Curli pili are cell-surface structures produced by certain bacteria and have been implicated in biofilm formation in these species. In order to determine whether these structures, which were suggested to be encoded by the Rv3312A (mtp) gene, have a similar role in Mycobacterium tuberculosis, we generated a Δmtp mutant and a mtp-complemented strain of a clinical isolate of M. tuberculosis and analyzed these strains for their ability to produce pili in comparison to the wild-type strain. Phenotypic analysis by transmission electron microscopy proved the essentiality of mtp for piliation in M. tuberculosis. We then compared biofilm formation of the derived strains in detergent-free Sauton's media. Biofilm mass was quantified spectrophotometrically using crystal violet. Furthermore, we examined mtp gene expression by quantitative real-time PCR in wild-type cells grown under biofilm versus planktonic growth conditions. We found a 68.4 % reduction in biofilm mass in the mutant compared to the wild-type strain (P = 0.002). Complementation of the mutant resulted in a restoration of the wild-type biofilm phenotype (P = 0.022). We, however, found no significant difference between mtp expression in cells of the biofilm to those growing planktonically. Our findings highlight a crucial, but non-specific, role of pili in the biofilm lifestyle of M. tuberculosis and indicate that they may represent an important target for the development of therapeutics to attenuate biofilm formation, thereby potentially reducing persistence.

Population structure of multi- and extensively drug-resistant Mycobacterium tuberculosis strains in South Africa.

Genotyping of multidrug-resistant (MDR) Mycobacterium tuberculosis strains isolated from tuberculosis (TB) patients in four South African provinces (Western Cape, Eastern Cape, KwaZulu-Natal, and Gauteng) revealed a distinct population structure of the MDR strains in all four regions, despite the evidence of substantial human migration between these settings. In all analyzed provinces, a negative correlation between strain diversity and an increasing level of drug resistance (from MDR-TB to extensively drug-resistant TB [XDR-TB]) was observed. Strains predominating in XDR-TB in the Western and Eastern Cape and KwaZulu-Natal Provinces were strongly associated with harboring an inhA promoter mutation, potentially suggesting a role of these mutations in XDR-TB development in South Africa. Approximately 50% of XDR-TB cases detected in the Western Cape were due to strains probably originating from the Eastern Cape. This situation may illustrate how failure of efficient health care delivery in one setting can burden health clinics in other areas.

Mycobacterium tuberculosis isolates grown under oxygen deprivation invade pulmonary epithelial cells.

Mycobacterium tuberculosis has the ability to adapt to and survive under different environmental conditions, including oxygen deprivation. To better understand the pathogenesis of M. tuberculosis, we studied the invasion of human alveolar (A549) and human bronchial (BBM) epithelial cell lines by M. tuberculosis isolates cultured under oxygen deprivation. We used isolates belonging to the Beijing and F15/LAM4/KZN families, isolates with unique DNA fingerprints and the laboratory strains H37Rv and H37Ra. We determined that: (1) M. tuberculosis bacilli grown under oxygen deprivation invade epithelial cells, (2) the invasion capacity of all 17 isolates differed, and (3) oxygen deprivation influenced the invasion capacity of these isolates. All isolates invaded the A549 more effectively than the BBM cells. Three of the F15/LAM4/KZN isolates, two of which had extensively drug resistance (XDR) profiles, were at least twice as invasive (≥33%) as the most invasive Beijing isolate (15%) (P < 0.05). We conclude that for a more comprehensive understanding of the pathogenesis of M. tuberculosis, studies should include isolates that have been cultured under oxygen deprivation.

Predominance of the Mycobacterium tuberculosis Beijing strain amongst children from a high tuberculosis burden township in South Africa.

The objective was to determine the molecular epidemiology and drug susceptibility patterns of Mycobacterium tuberculosis (MTB) of children and their household contacts (HHC) in Umlazi, a high TB-burden township in South Africa. Sixty eight MTBRifPLUS positive TB-infected children (TIC) (≤14 years) and 111 HHC were enrolled. Drug susceptibility testing (DST) was performed on sputum samples using the proportion method and GenoType® MTBDR. Genotyping of MTB was conducted using IS6110-restriction fragment length polymorphism (RFLP) and spoligotyping. Rifampicin (RIF) susceptibility was observed in 67/68 TIC. GenoType® MTBDRplus and phenotypic DST identified drug resistant strains in five of 16 culture-confirmed TIC. The Beijing strain was identified in six and the F15/LAM4/KZN strain in one of the 13 TIC respectively. Four patients with unknown RFLP strains belonged to spoligoclades S, T1, T3 variant and X2. The S-lineage and an unknown strain were identified in two HHC. MDR-TB and pre-XDR-TB were identified in one HHC each. Household transmission could not be determined as none of the culture-confirmed TIC resided with the six culture-confirmed contacts. The predominance of the hypervirulent Beijing strain and presence of drug-resistant strains must be considered in the implementation of effective TB control strategies and development of efficacious vaccines.

Genome sequence of a carbapenemase-encoding Acinetobacter baumannii isolate of the sequence type 231 isolated from hospital wastewater in South Africa.

OBJECTIVES: The resistome, virulome, mobilome and phylogenetic relationship of the Acinetobacter baumannii isolate FG121 depicting the multilocus sequence type (ST) 231 isolated from hospital effluent water in South Africa was determined using whole-genome sequence analysis. METHOD: A. baumannii FG121 was isolated on Leed Acinetobacter Medium (LAM) agar and the bacterial isolate was identified using the VITEK®2 platform. Antibiotic susceptibility testing was performed using Kirby-Bauer Disk diffusion method. A whole genome sequencing library was constructed from DNA extracted from the isolate using the Illumina Nextera XT library preparation kit and was sequenced using the Illumina NextSeq500 platform. Generated reads were de novo assembled using SpAdes v.3.9. The assembled contigs were annotated, and multilocus sequence type, antimicrobial resistance, and virulence genes were identified. RESULTS: The resistome was consistent with the resistance phenotype of the isolate with resistance determinants for beta-lactams, aminoglycosides, and tetracycline (blaADC-25, blaOXA-23, blaOXA-51, blaNDM-1, aph[3']-VIa and tet[B]). Global phylogenomic analysis using BacWGSTdb revealed that the isolate belonged to the multilocus sequence type ST-231, similar to previously reported isolates from South Africa, the United States, and related to the invasive KR3831 isolate identified from Oman in 2012, suggesting the isolate might be imported from abroad. Virulome analysis predicted both virulence and biofilm-determinants of A. baumannii, which may help to establish infections in adverse conditions. CONCLUSION: This is the first report on a carbapenemase-encoding A. baumannii ST-231 isolated from hospital effluent water. Our data will offer insight into the global phylogenetic, pathogenicity and distribution of A. baumannii in South Africa.

M. tuberculosis curli pili (MTP) facilitates a reduction of microbicidal activity of infected THP-1 macrophages during early stages of infection.

Mycobacterium tuberculosis (M. tuberculosis) curli pili (MTP) is a surface located adhesin, which is involved in the initial point-of-contact between the pathogen and the host. Host-pathogen interaction is essential for establishing infection. M. tuberculosis has the ability to infect various host lung cell types, which includes both the epithelial cells and macrophages, and subsequent differences in their cellular function will be evident in their metabolic profiles. Understanding the differences between these cell types and their individual metabolic response to M. tuberculosis infection, with and without the presence of the MTP, will aid to better elucidate the role of this adhesin in modulating metabolic pathways during infection. This may further contribute to the development of improved diagnostic and therapeutic interventions, much needed at present in order to improve control the global tuberculosis (TB) epidemic. This study used a two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (GC×GC-TOFMS) metabolomics approach to compare the metabolite profiles of A549 epithelial cells to that of THP-1 macrophages, infected with M. tuberculosis, in the presence and absence of MTP. Significant metabolites were identified using various univariate and multivariate statistical analysis. A total of 44, 40, 50 and 34 metabolites were differentially detected when comparing the (a) uninfected A549 epithelial cells to uninfected THP-1 macrophages, (b) wild-type infected A549 epithelial cells to wild-type infected THP-1 macrophages, (c) ∆mtp-infected A549 epithelial cells to ∆mtp-infected THP-1 macrophages (d) complement-infected A549 epithelial cells to complement-infected THP-1 macrophages, respectively. These included metabolites that were involved in amino acid metabolism, fatty acid metabolism, general central carbon metabolism, and nucleic acid metabolism. In the absence of the M. tuberculosis MTP adhesin, the THP-1 macrophages predominantly displayed higher concentrations of amino acids and their metabolic intermediates, than the A549 epithelial cells. The deletion of MTP from M. tuberculosis in the host infection models potentially elicited a pro-inflammatory phenotype, particularly in the macrophage model. In the presence of MTP, the metabolite profile changes indicate potential regulation of host defence mechanisms, accompanied by a reduction in microbicidal abilities of host cells. Hence MTP can be considered a virulence factor of M. tuberculosis. Therefore, blocking MTP interaction with the host may facilitate a faster pathogen clearance during the initial stages of infection, and potentially enhance current therapeutic interventions.

Antibiotic resistance and biofilm formation of Acinetobacter baumannii isolated from high-risk effluent water in tertiary hospitals in South Africa.

OBJECTIVES: Discharge of drug-resistant, biofilm-forming pathogens from hospital effluent water into municipal wastewater treatment plants poses a public health concern. This study examined the relationship between antibiotic resistance levels and biofilm formation of Acinetobacter baumannii strains isolated from hospital effluents. METHODS: Antibiotic susceptibility of 71 A. baumannii isolates was evaluated by the Kirby-Bauer disk diffusion method. Minimum inhibitory concentrations (MICs) were determined by the agar dilution method, while the minimum biofilm eradication concentration (MBEC) was determined by the broth dilution method. Genotyping was performed for plasmid DNA. Biofilm formation was evaluated by the microtitre plate method and was quantified using crystal violet. A P-value of <0.05 was regarded as statistically significant in all tests. RESULTS: Extensively drug-resistant (XDR) strains made up 58% of the isolates, while multidrug-resistant (MDR) and pandrug-resistant (PDR) strains made up 50% of the isolates from final effluent. The MBEC of ciprofloxacin increased by 255-fold, while that of ceftazidime was as high as 63-1310-fold compared with their respective MICs. Isolates were classified into four plasmid pattern groups with no association between biofilm formation and plasmid type (P = 0.0921). The degree of biofilm formation was independent of the level of antibiotic resistance, although MDR, XDR and PDR isolates produced significant biofilm biomass (P = 0.2580). CONCLUSION: These results suggest that hospital effluent is a potential source of MDR biofilm-forming A. baumannii strains. Appropriate treatment and disposal of effluents are essential to prevent the presence of drug-resistant pathogens in wastewater.

Light Forge: A Microfluidic DNA Melting-based Tuberculosis Test.

BACKGROUND: There is a well-documented lack of rapid, low-cost tuberculosis (TB) drug resistance diagnostics in low-income settings across the globe. It is these areas that are plagued with a disproportionately high disease burden and in greatest need of these diagnostics. METHODS: In this study, we compared the performance of Light Forge, a microfluidic high-resolution melting analysis (HRMA) prototype for rapid low-cost detection of TB drug resistance with a commercial HRMA device, a predictive "nearest-neighbor" thermodynamic model, DNA sequencing, and phenotypic drug susceptibility testing (DST). The initial development and assessment of the Light Forge assay was performed with 7 phenotypically drug resistant strains of Mycobacterium tuberculosis (M.tb) that had their rpoB gene subsequently sequenced to confirm resistance to Rifampin. These isolates of M.tb were then compared against a drug-susceptible standard, H37Rv. Seven strains of M.tb were isolated from clinical specimens and individually analyzed to characterize the unique melting profile of each strain. RESULTS: Light Forge was able to detect drug-resistance linked mutations with 100% concordance to the sequencing, phenotypic DST and the "nearest neighbor" thermodynamic model. Researchers were then blinded to the resistance profile of the seven M.tb strains. In this experiment, Light Forge correctly classified 7 out of 9 strains as either drug resistant or drug susceptible. CONCLUSIONS: Light Forge represents a promising prototype for a fast, low-cost diagnostic alternative for detection of drug resistant strains of TB in resource constrained settings.

Immunoscreening of the M. tuberculosis F15/LAM4/KZN secretome library against TB patients' sera identifies unique active- and latent-TB specific biomarkers.

Tuberculosis (TB) protein biomarkers are urgently needed for the development of point-of-care diagnostics, new drugs and vaccines. Mycobacterium tuberculosis extracellular and secreted proteins play an important role in host-pathogen interactions. Antibodies produced against M. tuberculosis proteins before the onset of clinical symptoms can be used in proteomic studies to identify their target proteins. In this study, M. tuberculosis F15/LAM4/KZN strain phage secretome library was screened against immobilized polyclonal sera from active TB patients (n = 20), TST positive individuals (n = 15) and M. tuberculosis uninfected individuals (n = 20) to select and identify proteins recognized by patients' antibodies. DNA sequence analysis from randomly selected latent TB and active TB specific phage clones revealed 118 and 96 ORFs, respectively. Proteins essential for growth, virulence and metabolic pathways were identified using different TB databases. The identified active TB specific biomarkers included five proteins, namely, TrpG, Alr, TreY, BfrA and EspR, with no human homologs, whilst latent TB specific biomarkers included NarG, PonA1, PonA2 and HspR. Future studies will assess potential applications of identified protein biomarkers as TB drug or vaccine candidates/targets and diagnostic markers with the ability to discriminate LTBI from active TB.

Evaluation of a synthetic peptide for the detection of anti-Mycobacterium tuberculosis curli pili IgG antibodies in patients with pulmonary tuberculosis.

Tuberculosis (TB) remains a serious threat in underdeveloped areas. Mycobacterium tuberculosis curli pili (MTP), a virulence factor, is a potential biomarker for a reliable point of care (POC) test and was evaluated for its ability to react with Immunoglobulin G (IgG) in TB patients. An MTP synthetic peptide in a slot blot assay was used to screen serum/plasma samples (n = 65) in 3 separate cohorts, including 40 TB positive (16 HIV co-infected), 20 TB negative/HIV negative patients and 5 healthy volunteers. Forty samples were true positives (HIV positive, n = 16), 23 true negatives (HIV negative) and 2 false positives (HIV negative). The McNemar test demonstrated a 3.08% accuracy estimate (CI: -2.1% - 3.08%). This confirms that MTP is expressed during infection, including HIV-TB co-infection, is likely to be suitable for the design of a POC test and supports the validation of MTP for TB detection in larger patient populations.

Evolution of the extensively drug-resistant F15/LAM4/KZN strain of Mycobacterium tuberculosis in KwaZulu-Natal, South Africa.

BACKGROUND: Although several hot spots of multidrug-resistant tuberculosis have been identified on the African continent, extensive drug resistance (XDR) has not been reported until recently, when a large number of XDR cases were identified in KwaZulu-Natal. The majority of the patients involved were infected with the same strain of Mycobacterium tuberculosis (F15/LAM4/KZN). We report this strain's development from multidrug resistance to XDR. METHODS: We searched databases for studies performed during the period 1994-2005 that involved the resistance patterns of isolates of M. tuberculosis with the F15/LAM4/KZN strain fingerprint. RESULTS: As early as 1994, the F15/LAM4/KZN strain was responsible for a number of cases of multidrug-resistant tuberculosis, indicating the ability of the strain to cause cases of primary resistant tuberculosis. Some of the isolates were also resistant to streptomycin. From 1994 onwards, multidrug-resistant isolates with resistance to additional drugs were found, and the first XDR isolate was discovered in 2001. CONCLUSIONS: Drug resistance to as many as 7 drugs developed in a local strain of M. tuberculosis in slightly more than a decade. This coincided with the introduction of the directly observed therapy-based and directly observed therapy-plus-based tuberculosis-control programs. It is postulated that the introduction of these programs in the absence of susceptibility testing or drug resistance surveillance has been instrumental in the development of XDR in this highly transmissible F15/LAM4/KZN strain. The expanding pool of human immunodeficiency virus-infected, tuberculosis-susceptible individuals has likely contributed to this development.

Identification of unique essential proteins from a Mycobacterium tuberculosis F15/LAM4/KZN phage secretome library.

Mycobacterium tuberculosis (Mtb) is the causative agent of tuberculosis disease (TB), the leading cause of death from bacterial infection worldwide. Although treatable, the resurgence of multidrug-resistant and extensively drug-resistant TB is a major setback for the fight against TB globally. Consequently, there is an urgent need for new Mtb-derived biomarkers for use in the design of new drugs and rapid point-of-care diagnostic or prognostic tools for the management of TB transmission. Therefore, the present study aimed to identify unique Mtb-secreted proteins from the extensively drug-resistant Mtb F15/LAM4/KZN phage secretome library. A whole genome library was constructed using genomic DNA fragments of the Mtb F15/LAM4/KZN strain. A phage secretome sub-library of 8 × 103 clones was prepared and phage DNA was sequenced from 120 randomly selected clones. DNA sequence BLAST analysis identified 86 open reading frames. Using bioinformatics tools and databases, 10 proteins essential for in vivo growth and survival of Mtb (Nrp, PssA, MmpL5, SirA, GatB, EspA, TopA, EccCa1, Rv1634 and Rv3103c) were identified. Proteins essential for the growth and survival of Mtb during infection have potential application in the development of diagnostic tools, new drugs and vaccines. Further studies will be conducted to evaluate their potential application in the fight against TB.