Biofilms and Mycobacterium tuberculosis

Mycobacterium tuberculosis H37Rv enolase (Rv1023)- expression, characterization and effect of host dependent modifications on protein functionality

Mycobacterium tuberculosis enolase is an essential glycolytic enzyme that catalyzes the conversion of 2, phosphoglycerate (PGA) to phosphoenol pyruvate (PEP). It is also a crucial link between glycolysis and the tricarboxylic acid (TCA) pathway. The depletion of PEP has recently been associated with the emergence of non-replicating drug resistant bacteria. Enolase is also known to exhibit multiple alternate functions, such as promoting tissue invasion via its role as a plasminogen (Plg) receptor. In addition, proteomic studies have identified the presence of enolase in the Mtb degradosome and in biofilms. However, the precise role in these processes has not been elaborated. The enzyme was recently identified as a target for 2-amino thiazoles - a novel class of anti-mycobacterials. In vitro assays and characterization of this enzyme were unsuccessful due to the inability to obtain functional recombinant protein. In the present study, we report the expression and characterization of enolase using Mtb H37Ra as a host strain. Our study demonstrates that the enzyme activity and alternate functions of this protein are significantly impacted by the choice of expression host (Mtb H37Ra or E. coli). Detailed analysis of the protein from each source revealed subtle differences in the post-translational modifications. Lastly, our study confirms the role of enolase in Mtb biofilm formation and describes the potential for inhibiting this process.

Polyphosphate kinase 1 is involved in formation, the morphology and ultramicrostructure of biofilm of Mycobacterium smegmatis and its survivability in macrophage

The most unique characteristic of Mycobacterium tuberculosis is persistence in the human host, and the biofilm formation is related to the persistance. Polyphosphate (polyP) kinase 1 (PPK1) is conserved in Mycobacteria and is responsible for polyP synthesis. polyP is a chain molecule linked by high-energy phosphate bonds, which is considered to play a very important role in bacterial persistence. However, the relationship of PPK1 and mycobacterial biofilm formation is still adequately unclear. In current study, ppk1-deficient mutant (MT), ppk1-complemented (CT) and wild-type strains of M. smegmatis mc² 155 were used to investigate the formation, morphology and ultramicrostructure of the biofilm and to analyze the lipid levels and susceptibility to vancomycin antibiotic. And then WT, MT and CT strains were used to infect macrophages and to analyze the expression levels of various inflammatory factors, respectively. We found that PPK1 was required for M. smegmatis polyP production in vivo and polyP deficiency not only attenuated the biofilm formation, but also altered the phenotype and ultramicrostructure of the biofilm and reduced the cell lipid composition (except for C16.1 and C17.1, most of the fatty acid components from C8-C24). Moreover, the ppk1-deficient mutant was also significantly more sensitive to vancomycin which targets the cell wall, and its ability to survive in macrophages was decreased, which was related to the change of the expression level of inflammatory factors in macrophage. This study demonstrates that the PPK1 can affect the biofilm structure through affecting the content of short chain fatty acid and promote intracellular survival of M. smegmatis by altering the expression of inflammatory factors. These findings establish a basis for investigating the role of PPK1 in the persistence of M. tuberculosis, and provide clues for treating latent infection of M. tuberculosis with PPK1 as a potential drug target.

Protocol for clinical diagnosis and empiric treatment of pulmonary tuberculosis in severely burned patients: observations and literature review

Introduction

Reactivation of pulmonary tuberculosis is a prevalent concomitant infection and cause for mortality in burns patients in Sub-Saharan Africa. First line laboratory diagnostic studies for pulmonary tuberculosis are often negative in these patients and if relied on, result in high mortality. The purpose of this report is to share our experience with a novel protocol of empiric treatment of clinically suspected pulmonary tuberculosis in severely burned patients with negative GeneXpert tests in a tertiary burns centre and to present a brief literature review on the topic.

Methods

A retrospective chart review of all patients, who sustained thermal injury with an inhalation component, with negative GeneXpert tests who were treated empirically for pulmonary tuberculosis over a five-year period (2015-2020) was performed. Additionally, a literature search was performed on Medline (PubMed), Cochrane and Google Scholar databases.

Results

Over the five-year period, 20 patients with suspected pulmonary tuberculosis and severe burns requiring ventilation were managed according to the protocol and all survived to discharge. The literature search identified six factors that explain the consequence of pulmonary tuberculosis in severely burned patients and provide a hypothesis for the negative laboratory studies encountered.

Conclusion

There was an improved outcome for patients with the clinical diagnosis of reactivation of pulmonary tuberculosis when they were started on empirical pulmonary tuberculosis treatment. There are several potential mechanisms that can contribute to reactivation of pulmonary tuberculosis in susceptible severely burned patients. The GeneXpert test should not be relied upon in these patients for a diagnosis, but rather all other clinical evidence should inform management.

Lay Summary

From the current literature evidence most patients who have severe burns complicated by a secondary infection known as pulmonary (lung) tuberculosis, die as a result. The purpose of this report is to share our experience with treatment of pulmonary tuberculosis during a five-year period, from 2015 to 2020, in a specialized adult tertiary burn center. Severely burned patients who were suspected of having pulmonary tuberculosis and received treatment despite having negative laboratory tests for pulmonary tuberculosis, had a better survival rate than expected. A brief literature review on the topic of pulmonary tuberculosis and severe burns was done to investigate causes for reactivation of pulmonary tuberculosis and negative laboratory studies in these patients.The literature search identified the following factors that can potentially affect the reactivation of pulmonary tuberculosis in severely burned patients: decreased immune system; secondary infections; low blood albumin(protein) levels; decreased clearance of bacteria from the airways, the development of pulmonary tuberculosis biofilms (capsules that protect the bacteria from chemicals and antibiotics) and the role of a fat molecule called phosphatidylinositol mannoside in pulmonary tuberculosis.In conclusion, the pulmonary tuberculosis test should not be relied upon in these patients, but rather all the clinical evidence such X-ray changes in association with difficulty to wean the patient off the ventilator should be used to inform treatment choice.

Mycobacterium tuberculosis and Paracoccidioides brasiliensis Formation and Treatment of Mixed Biofilm In Vitro

Co-infection of Mycobacterium tuberculosis and Paracoccidioides brasiliensis, present in 20% in Latin America, is a public health problem due to a lack of adequate diagnosis. These microorganisms are capable of forming biofilms, mainly in immunocompromised patients, which can lead to death due to the lack of effective treatment for both diseases. The present research aims to show for the first time the formation of mixed biofilms of M. tuberculosis and P. brasiliensis (Pb18) in vitro, as well as to evaluate the action of 3’hydroxychalcone (3’chalc) -loaded nanoemulsion (NE) (NE3’chalc) against monospecies and mixed biofilms, the formation of mixed biofilms of M. tuberculosis H37Rv (ATCC 27294), 40Rv (clinical strains) and P. brasiliensis (Pb18) (ATCC 32069), and the first condition of formation (H37Rv +Pb18) and (40Rv + Pb18) and second condition of formation (Pb18 + H37Rv) with 45 days of total formation time under both conditions. The results of mixed biofilms (H37Rv + Pb18) and (40Rv + Pb18), showed an organized network of M. tuberculosis bacilli in which P. brasiliensis yeasts are connected with a highly extracellular polysaccharide matrix. The (Pb18 + H37Rv) showed a dense biofilm with an apparent predominance of P. brasiliensis and fragments of M. tuberculosis. PCR assays confirmed the presence of the microorganisms involved in this formation. The characterization of NE and NE3’chalc displayed sizes from 145.00 ± 1.05 and 151.25 ± 0.60, a polydispersity index (PDI) from 0.20± 0.01 to 0.16± 0.01, and zeta potential -58.20 ± 0.92 mV and -56.10 ± 0.71 mV, respectively. The atomic force microscopy (AFM) results showed lamellar structures characteristic of NE. The minimum inhibitory concentration (MIC) values of 3’hidroxychalcone (3’chalc) range from 0.97- 7.8 µg/mL and NE3’chalc from 0.24 - 3.9 µg/mL improved the antibacterial activity when compared with 3’chalc-free, no cytotoxicity. Antibiofilm assays proved the efficacy of 3’chalc-free incorporation in NE. These findings contribute to a greater understanding of the formation of M. tuberculosis and P. brasiliensis in the mixed biofilm. In addition, the findings present a new possible NE3’chalc treatment alternative for the mixed biofilms of these microorganisms, with a high degree of relevance due to the lack of other treatments for these comorbidities.

Edible marine algae: a new source for anti-mycobacterial agents

Tuberculosis is a dreaded disease, which causes innumerable death worldwide. The emergence of drug resistance strains makes the situation devastating. Therefore, for better management of public health, it is mandatory to search for new anti-mycobacterial agents. In this context, the current study investigated two edible marine algae, Ulva lactuca and Ulva intestinalis, for the probable source of new anti-mycobacterial agents. To test the anti-mycobacterial activity, alcoholic extracts of these two algae were spotted on the Mycobacterium smegmatis lawn. Upon incubation, clear zone was observed at the spots. It indicated that these two extracts have anti-mycobacterial activity. In addition, their anti-biofilm property was also tested. It was found that both the extracts inhibit the mycobacterial biofilm development as well as they can disperse the preformed mycobacterial biofilm. Since these two are capable of dispersing preformed mycobacterial biofilm, it is possible that in the presence of either of these two extracts, isoniazid and rifampicin can kill biofilm encapsulated mycobacterium in combinatorial therapy. Consistent with the hypothesis, rifampicin and isoniazid killed mycobacteria that were present in biofilm. Thus, these two extracts augment the activity of rifampicin and isoniazid upon biofilm dispersal. Moreover, treatment of different cell lines with these two extracts exhibited no or little cytotoxic effects. Thus, these two agents have the potential to be good therapeutic agents against mycobacterial diseases.

Mycobacterium tuberculosis prosthetic joint infections: A case series and literature review

OBJECTIVES

We aimed to characterize diagnosis, management, and outcome of Mycobacterium tuberculosis prosthetic joint infections (PJI).

METHODS

Cases of M. tuberculosis PJI documented in 7 referral French centers were retrospectively reviewed. Data were collected from medical files on a standardized questionnaire. We performed a literature review using the keywords 'prosthetic joint', and 'tuberculosis'.

RESULTS

During years 1997-2016, 13 patients (8 males, 5 females, median age 79 years [range, 60-86]) had documented M. tuberculosis PJI, involving hip (n = 6), knee (n = 6), or shoulder (n = 1). Median time from arthroplasty to diagnosis was 9 years [0.4-20]. The diagnosis was obtained on joint aspirates (n = 9), or synovial tissue (n = 4). PCR was positive in all cases tested (5/5). Median duration of antituberculosis treatment was 14 months [6-32]). Nine patients underwent surgery: debridement (n = 4), resection arthroplasty (n = 3), and revision arthroplasty (1-stage exchange, n = 2). PJI was controlled in 12 patients. Seventeen additional cases of documented M. tuberculosis PJI have been reported, with a favorable outcome in 79% (11/14) of patients with no surgery, 85% (11/13) with debridement, 86% (19/22) with revision arthroplasty, and 81% (17/21) with resection (NS).

CONCLUSIONS

M. tuberculosis PJI can be controlled with prolonged antituberculosis treatment in most cases, with or without surgical treatment.

Immune response elicited by two rBCG strains devoid of genes involved in c-di-GMP metabolism affect protection versus challenge with M. tuberculosis strains of different virulence

Pellicles, a type of biofilm, have gathered a renewed interest in the field of tuberculosis as a structure that mimics some characteristics occurring during M. tuberculosis infection, such as antibiotic recalcitrance and chronicity of infection, and as a source of antigens for humoral response in infected guinea pigs. In other bacteria, it has been well documented that the second messenger c-di-GMP modulates the transition from planktonic cells to biofilm formation. In this work, we used the live vaccine Mycobacterium bovis BCG to determine whether deletion of genes involved in c-di-GMP metabolism would affect interaction with macrophages, capacity to induce immune response in a murine cell line and mice, and how the protein profile was modified when grown as surface pellicles. We found that deletion of the BCG1419c (Delta c-di-GMP phosphodiesterase, ΔPDE) gene, or deletion of the BCG1416c (Delta c-di-GMP diguanylate cyclase, ΔDGC) gene, altered production of TNF-α, IL-6, and IL-1β, in murine macrophages, and resulted in attenuation in intra-macrophage replication. Moreover, in addition to the improved immunogenicity of the BCGΔBCG1419c mutant already reported, deletion of the BCG1416c gene leads to increased T CD4⁺ and T CD8⁺ activation. This correlated with protection versus lethality in mice infected with the highly virulent M. tuberculosis 5186 afforded by vaccination with all the tested BCG strains, and controlled the growth of the mildly virulent M. tuberculosis H37Rv in lungs by vaccination with BCGΔBCG1419c during chronic late infection from 4 to 6 months after challenge. Furthermore, when grown as surface pellicles, a condition used to manufacture BCG vaccine, in comparison to BCG wild type, both rBCGs changed expression of antigenic proteins such as DnaK, HbhA, PstS2, 35KDa antigen, GroEL2, as well as AcpM, a protein involved in synthesis of mycolic acids, molecules relevant to modulate inflammatory responses.