Recombinant BCG vaccine expressing multistage antigens of Mycobacterium tuberculosis provides long-term immunity against tuberculosis in BALB/c mice

Tuberculosis (TB) caused by Mycobacterium tuberculosis (Mtb) persistently kills nearly 1.5 million lives per year in the world, whereas the only licensed TB vaccine BCG exhibits unsatisfactory efficacy in adults. Taking BCG as a vehicle to express Mtb antigens is a promising way to enhance its efficacy against Mtb infection. In this study, the immune efficacy of recombination BCG (rBCG-ECD003) expressing specific antigens ESAT-6, CFP-10, and nDnaK was evaluated at different time points after immunizing BALB/c mice. The results revealed that rBCG-ECD003 induced multiple Th1 cytokine secretion including IFN-γ, TNF-α, IL-2, and IL-12 when compared to the parental BCG. Under the action of PPD or ECD003, rBCG-ECD003 immunization resulted in a significant increase in the proportion of IL-2+ and IFN-γ+IL-2+ CD4+T cells. Importantly, rBCG-ECD003 induced a stronger long-term humoral immune response without compromising the safety of the parental BCG vaccine. By means of the protective efficacy assay in vitro, rBCG-ECD003 showed a greater capacity to inhibit Mtb growth in the long term. Collectively, these features of rBCG-ECD003 indicate long-term protection and the promising effect of controlling Mtb infection.

Exploring the immunogenicity of Rv2201-519: A T-cell epitope-based antigen derived from Mycobacterium tuberculosis AsnB with implications for tuberculosis infection detection and vaccine development

Research dedicated to diagnostic reagents and vaccine development for tuberculosis (TB) is challenging due to the paucity of immunodominant antigens that can predict disease risk and exhibit protective potential. Therefore, it is crucial to identify T-cell epitope-based Mycobacterium tuberculosis (MTB) antigens characterized by specific and prominent recognition by the immune system. In this study, we constructed a T-cell epitope-rich tripeptide-splicing fragment (nucleotide positions 131-194, 334-377, and 579-643) of Rv2201 (also known as the 72 kDa AsnB)from the MTB genome, ultimately yielding the recombinant protein Rv2201-519 in Escherichia coli BL21 (DE3). Subsequently, we gauged the recombinant protein's ability to detect tuberculosis infection through ELISpot and assessed its immunostimulatory effect on mouse models using flow cytometry and ELISA. Our results indicated that Rv2201-519 possessed promising sensitivity; however, the sensitivity was lower than that of a commercial diagnostic kit containing ESAT-6, CFP-10, and Rv3615c (80.56 % vs. 94.44 %). The Rv2201-519 group exhibited a propensity for a CD4+ Th1 cell immune response in inoculated BALB/c mice that manifested as higher levels of antigen-specific IgG production (IgG2a/IgG1 > 1). In comparison to Ag85B, Rv2201-519 induced a more robust Th1-type cellular immune response as evidenced by a notable rise in the ratio of IFN-γ/IL-4 and IL-12 cytokine production and increased CD4+ T cell activation with a higher percentage of CD4+IFN-γ+ T cells. Rv2201-519 also induced a higher level of IL-6 compared with Ag85B, a higher percentage of CD8+ T cells specific for Rv2201-519, and a lower percentage of CD8+IL-4+ T cells. Collectively, the current evidence suggests that Rv2201-519 could potentially serve as an immunodominant protein for tuberculosis infection screening, laying the groundwork for further evaluation in recombinant Bacillus Calmette-Guérin (BCG) and subunit vaccines against MTB challenges in future studies.

Prevalence, Transmission and Genetic Diversity of Pyrazinamide Resistance Among Multidrug-Resistant Mycobacterium tuberculosis Isolates in Hunan, China

Background

China is a country with a burden of high rates of both TB and multidrug-resistant TB (MDR-TB). However, published data on pyrazinamide (PZA) resistance are still limited in Hunan province, China. This study investigated the prevalence, transmission, and genetic diversity of PZA resistance among multidrug-resistant Mycobacterium tuberculosis isolates in Hunan province.

Methods

Drug susceptibility testing (DST) with the Bactec MGIT 960 PZA kit and pyrazinamidase (PZase) testing were conducted on all 298 MDR clinical isolates. Moreover, 24-locus MIRU-VNTR and DNA sequencing of pncA, rpsA, and panD genes were conducted on 180 PZA-resistant (PZA-R) isolates.

Results

The prevalence of PZA resistance among MDR-TB strains reached 60.4%. Newly diagnosed PZA-R TB patients and clustered isolates with identical pncA, rpsA, and panD mutations showed that transmission of PZA-R isolates played a significant role in the formation of PZA-R TB. Ninety-eight mutation patterns were observed in the pncA among 180 PZA-R isolates, and seventy-one (72.4%) were point mutations. Twenty-four of these mutations are new, including 2 base substitutions (V93G and T153S) and 22 nucleotide deletions or insertions. The W119C was found in PZA-S isolates, on the other hand, F94L and V155A mutations were found in both PZA resistant and susceptible isolates with positive PZase activity, indicating that they were not associated with PZA resistance. This is not entirely in line with the WHO catalogue. Ten novel rpsA mutations were found in 10 PZA-R isolates, which all combined with mutations in pncA. Thus, it is unpredictable whether these mutations in rpsA can impact PZA resistance. No panD mutation was found in all PZA-R isolates.

Conclusion

DNA sequencing of pncA and PZase activity testing have great potential in predicting PZA resistance.

Comparison of the Immunogenicity and Efficacy of rBCG-EPCP009, BCG Prime-EPCP009 Booster, and EPCP009 Protein Regimens as Tuberculosis Vaccine Candidates

Bacillus Calmette-Guérin (BCG) is the only widely used prophylactic tuberculosis (TB) vaccine that can prevent severe TB in infants. However, it provides poor protection in adults, and therefore, there is ongoing research into new TB vaccines and immunization strategies with more durable immune effects. The recombinant BCG and BCG prime-protein booster are two important vaccine strategies that have recently been developed based on BCG and could improve immune responses. In this study, three immune strategies based on four protective antigens, namely, ESAT-6, CFP-10, nPPE18, and nPstS1, were applied to construct recombinant rBCG-EPCP009, EPCP009 subunit protein, and BCG prime-EPCP009 booster vaccine candidates. The short- and long-term immune effects after vaccination in Balb/c mice were evaluated based on humoral immunity, cellular immunity, and the ability of spleen cells to inhibit in vitro mycobacterial growth. At 8 and 12 weeks after the initial immunization, splenocytes from mice inoculated with the BCG prime-EPCP009 protein booster secreted higher levels of PPD- and EPCP009-specific IFN-γ, IL-2, TNF-α, IL-17, GM-CSF, and IL-12 and had a higher IFN-γ+CD4+ TEM:IL-2+CD8+ TCM cell ratio than splenocytes from mice inoculated with the rBCG-EPCP009 and EPCP009 proteins. In addition, the EPCPE009-specific IgG2a/IgG1 ratio was slightly higher in the BCG prime-EPCP009 protein booster group than in the other two groups. The in vitro mycobacterial inhibition assay showed that the splenocytes of mice from the BCG prime-EPCP009 protein booster group exhibited stronger inhibition of Mycobacterium tuberculosis (M. tuberculosis) growth than the splenocytes of mice from the other two groups. These results indicate that the BCG prime-EPCP009 protein booster exhibited superior immunogenicity and M. tuberculosis growth inhibition to the parental BCG, rBCG-EPCP009, and EPCP009 proteins under in vitro conditions. Thus, the BCG prime-EPCP009 protein booster may be important for the development of a more effective adult TB vaccine.

A novel multistage antigens ERA005f confer protection against Mycobacterium tuberculosis by driving Th-1 and Th-17 type T cell immune responses

Introduction

Tuberculosis (TB) is a major threat to human health. In 2021, TB was the second leading cause of death after COVID-19 among infectious diseases. The Bacillus Calmette-Guérin vaccine (BCG), the only licensed TB vaccine, is ineffective against adult TB. Therefore, there is an urgent need to develop new effective vaccines.

Methods

In this study, we developed a novel multistage subunit vaccine (ERA005f) comprising various proteins expressed in metabolic states, based on three immunodominant antigens (ESAT-6, Rv2628, and Ag85B). We utilized the E. coli prokaryotic expression system to express ERA005f and subsequently purified the protein using nickel affinity chromatography and anion exchange. Immunogenicity and protective efficacy of ERA005f and ERA005m were evaluated in BALB/c mice.

Results

ERA005f was consistently expressed as an inclusion body in a prokaryotic expression system, and a highly pure form of the protein was successfully obtained. Both ERA005f and ERA005m significantly improved IgG titers in the serum. In addition, mice immunized with ERA005f and ERA005m generated higher titers of antigen-specific IgG2a than the other groups. Elispot results showed that, compared with other groups, ERA005f increased the numbers of IFN-γ-secreting and IL-4-secreting T cells, especially the number of IFN-γ-secreting T cells. Meanwhile, ERA005f induced a higher number of IFN-γ+ T lymphocytes than ERA005m did. In addition, ERA005f improved the expression of cytokines, including IFN-γ, IL-12p70, TNF-α, IL-17, and GM-CSF and so on. Importantly, both ERA005f and ERA005m significantly inhibited the growth of Mtb.

Conclusion

The novel multistage antigen ERA005f elicited a strong antigen-specific humoral response and Th-1 and Th-17 cell-mediated immunity in mice. Meanwhile, it can effectively inhibit H37Rv growth in vitro, and represents a correlate of protection in vivo, indicating that ERA005f may exhibit excellent protective efficacy against Mycobacterium tuberculosis H37Rv infection. Our study suggests that ERA005f has the potential to be a promising multistage tuberculosis vaccine candidate.

Immunogenicity and efficacy analyses of EPC002, ECA006, and EPCP009 protein subunit combinations as tuberculosis vaccine candidates

Tuberculosis (TB) is the leading cause of death from infectious diseases worldwide, and developing a new TB vaccine is a priority for TB control. Combining multiple immunodominant antigens to form a novel multicomponent vaccine with broad-spectrum antigens to induce protective immune responses is a trend in TB vaccine development. In this study, we used T-cell epitope-rich protein subunits to construct three antigenic combinations: EPC002, ECA006, and EPCP009. Fusion expression of purified protein EPC002f (CFP-10-linker-ESAT-6-linker-nPPE18), ECA006f (CFP-10-linker-ESAT-6-linker-Ag85B), and EPCP009f (CFP-10-linker-ESAT-6-linker-nPPE18-linker-nPstS1) and recombinant purified protein mixtures EPC002m (mix of CFP-10, ESAT-6, and nPPE18), ECA006m (mix of CFP-10, ESAT-6, and Ag85B), and EPCP009m (mix of CFP-10, ESAT-6, nPPE18, and nPstS1) were used as antigens, formulated with alum adjuvant, and the immunogenicity and efficacy were analyzed using immunity experiments with BALB/c mice. All protein-immunized groups elicited higher levels of humoral immunity, including IgG and IgG1. The IgG2a/IgG1 ratio of the EPCP009m-immunized group was the highest, followed by that of the EPCP009f-immunized group, which was significantly higher than the ratios of the other four groups. The multiplex microsphere-based cytokine immunoassay revealed that EPCP009f and EPCP009m induced the production of a wider range of cytokines than EPC002f, EPC002m, ECA006f, and ECA006m, which included Th1-type (IL-2, IFN-γ, TNF-α), Th2-type (IL-4, IL-6, IL-10), Th17-type (IL-17), and other proinflammatory cytokines (GM-CSF, IL-12). The enzyme-linked immunospot assays demonstrated that the EPCP009f- and EPCP009m-immunized groups had significantly higher amounts of IFN-γ than the other four groups. The in vitro mycobacterial growth inhibition assay demonstrated that EPCP009m inhibited Mycobacterium tuberculosis (Mtb) growth most strongly, followed by EPCP009f, which was significantly better than that of the other four vaccine candidates. These results indicated that EPCP009m containing four immunodominant antigens exhibited better immunogenicity and Mtb growth inhibition in vitro and may be a promising candidate vaccine for the control of TB.

Association of Single-Nucleotide Polymorphisms in the VDR Gene with Tuberculosis and Infection of Beijing Genotype Mycobacterium tuberculosis

Background

The aim of the present study was to investigate the association between vitamin D receptor (VDR) gene polymorphism and tuberculosis susceptibility, as well as the potential interaction of host genetic factors with the heterogeneity of Mycobacterium tuberculosis in the population from Xinjiang, China.

Methods

From January 2019 to January 2020, we enrolled 221 tuberculosis patients as the case group and 363 staff with no clinical symptoms as the control group from four designated tuberculosis hospitals in southern Xinjiang, China. The polymorphisms of Fok I, Taq I, Apa I, Bsm I, rs3847987 and rs739837 in the VDR were detected by sequencing. M. tuberculosis isolates were collected from the case group and identified as Beijing or non-Beijing lineage by multiplex PCR. Propensity score (PS), univariate analysis and multivariable logistic regression models were used to perform the analysis.

Results

Our results showed that the allele and genotype frequencies of Fok I, Taq I, Apa I, Bsm I, rs3847987 and rs739837 in VDR were not correlated with tuberculosis susceptibility or lineages of M. tuberculosis. Two out of six loci of the VDR gene formed one haplotype block, and none of the haplotypes was found to correlate with tuberculosis susceptibility or lineages of M. tuberculosis infected.

Conclusion

Polymorphisms in the VDR gene may not indicate susceptibility to tuberculosis. There was also no evidence on the interaction between the VDR gene of host and the lineages of M. tuberculosis in the population from Xinjiang, China. Further studies are nonetheless required to prove our conclusions.

Genetic Characterization Conferred Co-Resistance to Isoniazid and Ethionamide in Mycobacterium tuberculosis Isolates from Southern Xinjiang, China

Background

Ethionamide (ETH), a structural analogue of isoniazid (INH), is used for treating multidrug-resistant tuberculosis (MDR-TB). Due to the common target InhA, INH and ETH showed cross-resistance in M. tuberculosis. This study aimed to explore the INH and ETH resistant profiles and genetic mutations conferring independent INH- or ETH-resistance and INH-ETH cross-resistance in M. tuberculosis circulating in south of Xinjiang, China.

Methods

From Sep 2017 to Dec 2018, 312 isolates were included using drug susceptibility testing (DST), spoligotyping, and whole genome sequencing (WGS) to analyze the resistance characteristics for INH and/or ETH.

Results

Among the 312 isolates, 185 (58.3%) and 127 (40.7%) belonged to the Beijing family and non-Beijing family, respectively; 90 (28.9%) were INH-resistant (INH^R) with mutation rates of 74.4% in katG, 13.3% in inhA and its promoter, 11.1% in ahpC and its upstream region, 2.2% in ndh, 0.0% in mshA, whilst 34 (10.9%) were ETH-resistant (ETH^R) with mutation rates of 38.2% in ethA, 26.2% in inhA and its promoter, and 5.9% in ndh, 0.0% in ethR or mshA; and 25 (8.0%) were INH-ETH co-resistant (INH^RETH^R) with mutation rates of 40.0% in inhA and its promoter, and 8% in ndh. katG mutants tended to display high-level resistant to INH; and more inhA and its promoter mutants showed low-level of INH and ETH resistance. The optimal gene combinations by WGS for the prediction of INH^R, ETH^R, and INH^RETH^R were, respectively, katG+inhA and its promoter (sensitivity: 81.11%, specificity: 90.54%), ethA+inhA and its promoter+ndh (sensitivity: 61.76%, specificity: 76.62%), and inhA and its promoter+ndh (sensitivity: 48.00%, specificity: 97.65%).

Conclusion

This study revealed the high diversity of genetic mutations conferring INH and/or ETH resistance among M. tuberculosis isolates, which would facilitate the study on INH^R and/or ETH^R mechanisms and provide clues for choosing ETH for MDR treatment and molecular DST methods in south of Xinjiang, China.

A novel multi-component protein vaccine ECP001 containing a protein polypeptide antigen nPstS1 riching in T-cell epitopes showed good immunogenicity and protection in mice

Tuberculosis (TB) is an infectious disease that seriously affects human health. Until now, the only anti-TB vaccine approved for use is the live attenuated Mycobacterium bovis (M. bovis) vaccine - BCG vaccine, but its protective efficacy is relatively low and does not provide satisfactory protection against TB in adults. Therefore, there is an urgent need for more effective vaccines to reduce the global TB epidemic. In this study, ESAT-6, CFP-10, two antigens full-length and the T-cell epitope polypeptide antigen of PstS1, named nPstS1, were selected to form one multi-component protein antigens, named ECP001, which include two types, one is a mixed protein antigen named ECP001m, the other is a fusion expression protein antigen named ECP001f, as candidates for protein subunit vaccines. were prepared by constructing one novel subunit vaccine by mixing or fusing the three proteins and combining them with aluminum hydroxide adjuvant, and the immunogenicity and protective properties of the vaccine was evaluated in mice. The results showed that ECP001 stimulated mice to produce high titre levels of IgG, IgG1 and IgG2a antibodies; meanwhile, high levels of IFN-γ and a broad range of specific cytokines were secreted by mouse splenocytes; in addition, ECP001 inhibited the proliferation of Mycobacterium tuberculosis in vitro with a capacity comparable to that of BCG. It can be concluded that ECP001 is a novel effective multicomponent subunit vaccine candidate with potential as BCG Initial Immunisation-ECP001 Booster Immunisation or therapeutic vaccine for M. tuberculosis infection.

Molecular Epidemiology of Clinical Mycobacterium tuberculosis Isolates from Southern Xinjiang, China Using Spoligotyping and 15-Locus MIRU-VNTR Typing

Background

In the last decades, the molecular epidemiological investigation of Mycobacterium tuberculosis has significantly increased our understanding of tuberculosis epidemiology. However, few such studies have been done in southern Xinjiang, China. We aimed to clarify the molecular epidemic characteristics and their association with drug resistance in the M. tuberculosis isolates circulating in this area.

Methods

A total of 347 isolates obtained from southern Xinjiang, China between Sep, 2017 and Sep, 2019 were included to characterize using a 15-locus MIRU-VNTR (VNTR-15_China) typing and spoligotyping, and test for drug susceptibility profiles. Then the lineages and clustering of the isolates were analyzed, as well as their association with drug resistance.

Results

Spoligotyping results showed that 60 spoligotype international types (SITs) containing 35 predefined SITs and 25 Orphan or New patterns, and 12 definite genotypes were found, and the top three prevalent genotypes were Beijing genotype (207, 59.7%), followed by CAS1-Delhi (46, 13.6%), and Ural-2 (30, 8.6%). The prevalence of Beijing genotype infection in the younger age group (≤30) was more frequent than the two older groups (30~59 and ≥60 years old, both P values <0.05). The Beijing genotype showed significantly higher prevalence of resistance to isoniazid, rifampicin, ethambutol, multi-drug or at least one drug than the non-Beijing genotype (All P values ≤0.05). The estimated proportion of tuberculosis cases due to transmission was 18.4% according to the cluster rate acquired by VNTR-15_China typing, and the Beijing genotype was the risk factor for the clustering (OR 9.15, 95% CI: 4.18-20.05).

Conclusion

Our data demonstrated that the Beijing genotype is the dominant lineage, associated with drug resistance, and was more likely to infect young people and contributed to tuberculosis transmission in southern Xinjiang, China. These findings will contribute to a better understanding of tuberculosis epidemiology in this area.

Whole-Genome Sequencing and Epidemiological Investigation of Tuberculosis Outbreaks in High Schools in Hunan, China

Background

Tuberculosis (TB) seriously threatens individual and public health. Recently, TB outbreaks in schools have been reported more frequently in China and have attracted widespread attention. We reported three TB outbreaks in high schools in Hunan Province, China.

Methods

When a tuberculosis patient was reported in a school, we carried out field epidemiological investigations, including tuberculin skin testing (TST), chest X-ray (CXR) and laboratory test for all close contacts, and whole-genome sequencing (WGS) analyses to understand the transmission patterns, the causes and the risk factors for the outbreaks, thereby providing a foundation for the control of TB epidemics in schools.

Results

A total of 49 students with TB patients were identified in the three schools where TB outbreaks occurred, including nine patients in School A, 14 patients in School B, and 26 patients in School C. In Schools A, B and C, the putative attack rates in the classes of the index case were 13.8% (8/58), 7.6% (5/66), and 40.4% (21/52), while the putative attack rates of expanding screening in the school were 0.3% (1/361), 0.2% (9/3955), and 0.2% (5/2080), respectively. Thirteen patients had patient delay, with a median delay interval of 69 days (IQR 30.5–113 days). Twelve patients had a healthcare diagnostic delay with a median delay interval of 32 days (IQR 24–82 days). Phylogenetic analysis of culture-positive patients revealed that most of them shared a small genetic distance (≤12 SNPs), with three separate genetic clusters (including one MDR-TB genomic cluster), indicating the recent transmission of Mycobacterium tuberculosis strains.

Conclusion

This combination of field investigation and WGS analysis revealed the transmission of three TB outbreaks in schools. Reinforced implementation is needed to improve timely case finding and reduce diagnosis delay in routine TB control in the school population.

High Immunogenicity of a T-Cell Epitope-Rich Recombinant Protein Rv1566c-444 From Mycobacterium tuberculosis in Immunized BALB/c Mice, Despite Its Low Diagnostic Sensitivity

The discovery of immunodominant antigens is of great significance for the development of new especially sensitive diagnostic reagents and effective vaccines in controlling tuberculosis (TB). In the present study, we targeted the T-Cell epitope-rich fragment (nucleotide position 109-552) of Rv1566c from Mycobacterium tuberculosis (MTB) and got a recombinant protein Rv1566c-444 and the full-length protein Rv1566c with Escherichia coli expression system, then compared their performances for TB diagnosis and immunogenicity in a mouse model. The results showed that Rv1566c-444 had similar sensitivity with Rv1566c (44.44% Vs 30.56%) but lower sensitivity than ESAT-6&CFP-10&Rv3615c (44.4% Vs. 94.4%) contained in a commercial kit for distinguishing TB patients from healthy donors. In immunized BALB/c mice, Rv1566c-444 elicited stronger T-helper 1 (Th1) cellular immune response over Rv1566c with higher levels of Th1 cytokine IFN-γ and IFN-γ/IL-4 expression ratio by ELISA; more importantly, with a higher proliferation of CD4⁺ T cells and a higher proportion of CD4⁺ TNF-α⁺ T cells with flow cytometry. Rv1566c-444 also induced a higher level of IL-6 by ELISA and a higher proportion of Rv1566c-444-specific CD8⁺ T cells and a lower proportion of CD8⁺ IL-4⁺ T cells by flow cytometry compared with the Rv1566c group. Moreover, the Rv1566c-444 group showed a high IgG secretion level and the same type of CD4+ Th cell immune response (both IgG1/IgG2a >1) as its parental protein group. Our results showed the potential of the recombinant protein Rv1566c-444 enriched with T-Cell epitopes from Rv1566c as a host T cell response measuring biomarker for TB diagnosis and support further evaluation of Rv1566c-444 as vaccine antigen against MTB challenge in animal models in the form of protein mixture or fusion protein.

Association of Mannose-Binding Lectin 2 Gene Polymorphism with Tuberculosis Based on Mycobacterium tuberculosis Lineages

Purpose

Polymorphisms in MBL2 may contribute to the susceptibility to tuberculosis. The aim of the present study was to determine the associations of the polymorphisms of five loci (rs1800450, rs1800451, rs7096206, rs7095891, and rs11003125) in the MBL2 gene with susceptibility to tuberculosis and specific lineages of Mycobacterium tuberculosis causing tuberculosis in the Uyghur population of Xinjiang, China.

Methods

From January 2019 to January 2020, we enrolled 170 Uyghur tuberculosis patients as the case group and 147 Uyghur staff with no clinical symptoms as the control group from four designated tuberculosis hospitals in southern Xinjiang, China. The polymorphisms of five loci in MBL2 of human were detected by sequencing. Whole-genome sequencing was applied in 68 M. tuberculosis isolates from the case group and the data were used to perform genealogy analysis.

Results

The distributions of allele and genotype frequencies of five loci in MBL2 varied little between the case and control groups and varied little among the groups, including those infected with different lineages of M. tuberculosis and the control (except those of rs11003125), the P values were all >0.05. The distribution of alleles of rs11003125 was statistically different between patients infected with lineages 3 and 4 M. tuberculosis (χ²=7.037, P=0.008). The C allele and CC genotype of rs11003125 were found to be protective factors against lineage 4 infection when compared to lineage 3 (ORs were 0.190 and 0.158, respectively; 95% confidence intervals were 0.053~0.690 and 0.025~0.999, respectively).

Conclusion

Our results suggested that human’s susceptibility to tuberculosis is affected both by the host genetic polymorphisms and the lineage of the M. tuberculosis that people were exposed to. However, due to the limitation of the sample size in the present study, larger sample size and more rigorous design should be guaranteed in future studies.

Deterioration of Cycloserine in Drug Susceptibility Testing of Mycobacterium

Purpose

Cycloserine is an effective group C anti-tuberculosis drug. But the reliability and reproducibility of drug susceptibility tests (DST) for this drug cannot be guaranteed and provide poor clinical predictive values. However, DST of cycloserine in practice provides rough estimate of the drug resistance of Mycobacterium strains, there is practical need to clarify the problem of cycloserine in in vitro DST, and to explore solutions to overcome these limitations.

Methods

The effectiveness of serial cycloserine solutions incubated at 37°C for 1 to 29 days was tested using the Alamar Blue assay, and cycloserine in culture medium was analyzed by UPLC-MS.

Results

The data revealed that cycloserine itself continuously degraded in culture medium. This amount of degradation was sufficient to alter the minimum inhibitory concentration (MIC) value of Mycobacterium strains and therefore could not be ignored, although it was more stable than in phosphoric acid buffer.

Conclusion

The different test times and the degradation of cycloserine were responsible for the lack of agreements between the cycloserine DST methods and the low reliability of this in vitro test. By adjusting with the incubation time depended degradation ratio of cycloserine, more accurate MIC values may be obtained allowing for improved coincidence between in vitro experiment and clinic use. Furthermore, it can guide clinicians to carry out this anti-tuberculosis treatment more effectively and reliably.

Mycolicibacterium baixiangningiae sp. nov. and Mycolicibacterium mengxianglii sp. nov., two new rapidly growing mycobacterial species

Four bacterial strains (LJ126^T/S18 and Z-34^T/S20) recovered from faecal samples of Tibetan antelopes on the Qinghai-Tibet Plateau of China were analysed using a polyphasic approach. All four isolates were aerobic, short rod-shaped, non-motile, Gram-stain-positive, acid-fast and fast-growing. Phylogenetic analyses based upon 16S rRNA and whole-genome sequences showed that the two pair of strains formed two distinct branches within the evolutionary radiation of the genus Mycolicibacterium. Strains LJ126^T/S18 and Z-34^T/S20 were most closely related to Mycolicibacterium austroafricanum CCUG 37667^T, Mycobacterium aurum NCTC 10437^T, Mycobacterium pyrenivorans DSM 44605^T, Mycobacterium monacense JCM 15658^T, Mycolicibacterium sarraceniae JCM 30395^T, Mycolicibacterium tokaiense JCM 6373^T and Mycobacterium murale JCM 13392^T, but readily distinguished from the known species by a combination of chemotaxonomic and phenotypic features and by low average nucleotide identity values (74.4-84.9 %). Consequently, the two strain pairs are considered to represent different novel species of Mycolicibacterium for which the names Mycolicibacterium baixiangningiae sp. nov. and Mycolicibacterium mengxianglii sp. nov. are proposed, with LJ126^T (=CGMCC 1.1992^T=KCTC 49535^T) and Z-34^T (=CGMCC 1.1993^T=DSM 106172^T) as the respective type strains.

Construction and immunogenicity of a T cell epitope-based subunit vaccine candidate against Mycobacterium tuberculosis

Despite antibiotic treatment and Bacille Calmette-Guérin (BCG) vaccination, Mycobacterium tuberculosis remains a major public health burden in most developing countries. Therefore, developing an improved vaccine is high priority. In this study, we cloned the genes of the immunodominant antigen of M. tuberculosis viz. its 38-kDa antigen (Pst homolog) (Rv0934, PstS1), and its T cell epitopes (amino acid [aa]169-405 and [aa]802-1119), which we termed PstS1p. Prokaryotic expression showed that the two recombinant proteins were mainly in the form of inclusion bodies. We also evaluated the immunity and immunogenicity of PstS1 and PstS1p. Both PstS1 and its T cell epitopes elicited significantly higher antigen-specific immunoglobulin G (IgG) antibodies in mouse serum, indicating that they enhanced antibody response. They also elicited the T helper 1 (Th1)-type response and promoted CD4⁺ T cell proliferation. Compared to PstS1, PstS1p promoted stronger cell-mediated immune response. These data indicate that PstS1p is highly immunogenic in mice, and may be a promising candidate vaccine for controlling tuberculosis.

Expression and purification of Rv2654 recombinant protein from Mycobacterium tuberculosis and its characteristics of immune response

OBJECTIVES

With the decreased protective effect of Bacille Calmette-Guérin (BCG) vaccine, widespread drug-resistant strains of tuberculosis as well as the lack of effective vaccines, global morbidity and mortality of tuberculosis remains high. The purpose of this study is to evaluate the potential of Mycobacterium tuberculosis antigen Rv2654 as a candidate vaccine against tuberculosis, and to verify the characteristics of cellular and humoral immune responses in mice induced by this protein.

METHODS

Isopropyl-beta-D-thiogalactoside (IPTG) was added to induce the expression of Rv2654 recombinant protein in the logarithmic growth stage of bacteria. The recombinant protein was purified by affinity chromatography and identified by Western blotting. The immunoreactivity of Rv2654 recombinant protein with human sera was detected by ELISA. After immunization with Rv2654 recombinant protein, the levels of Th1/Th2 cytokines in peripheral blood of mice was measured using cytokine magnetic bead arrays, and the T and B lymphocyte subsets in spleen of mice was analyzed by flow cytometry.

RESULTS

The recombinant protein Rv2654 was successfully induced and expressed. The ELISA data showed that the recombinant protein Rv2654 was responsive to the serum of BCG-inoculated patients or active pulmonary tuberculosis patients. In immunized mice with recombinant protein Rv2654, the expression of IFN-γ, TNF-α, IL-2, IL-4, IL-6, IL-10 and other cytokines in peripheral blood was elevated (all P<0.05). Flow cytometry analysis showed that the recombinant protein significantly stimulated the differentiation of CD4+T cells and CD8+T cells into effector T cells, and this effect was more obvious when combined with BCG. The recombinant protein Rv2654 also stimulated the activation and proliferation of B cells and their differentiation into memory cells. However, less plasma cells were produced.

CONCLUSIONS

Rv2654 protein could induce the cell immune responses and it has good binding ability with serum of BCG-inoculated patients and active pulmonary tuberculosis patients, suggesting that it may serve as a good candidate antigen for tuberculosis immunological prophylaxis and diagnostic vaccines.

Quantitative proteomics reveals that dormancy-related proteins mediate the attenuation in mycobacterium strains

Although members of the Mycobacterium tuberculosis complex (MTBC) exhibit high similarity, they are characterized by differences with respect to virulence, immune response, and transmissibility. To understand the virulence of these bacteria and identify potential novel therapeutic targets, we systemically investigated the total cell protein contents of virulent H37Rv, attenuated H37Ra, and avirulent M. bovis BCG vaccine strains at the log and stationary phases, based on tandem mass tag (TMT) quantitative proteomics. Data analysis revealed that we obtained deep-coverage protein identification and high quantification. Although 272 genetic variations were reported in H37Ra and H37Rv, they showed very little expression difference in log and stationary phase. Quantitative comparison revealed H37Ra and H37Rv had significantly dysregulation in log phase (227) compared with stationary phase (61). While BCG and H37Rv, and BCG and H37Ra showed notable differences in stationary phase (1171 and 1124) with respect to log phase (381 and 414). In the log phase, similar patterns of protein abundance were observed between H37Ra and BCG, whereas a more similar expression pattern was observed between H37Rv and H37Ra in the stationary phase. Bioinformatic analysis revealed that the upregulated proteins detected for H37Rv and H37Ra in log phase were virulence-related factors. In both log and stationary phases, the dysregulated proteins detected for BCG, which have also been identified as M. tuberculosis response proteins under dormancy conditions. We accordingly describe the proteomic profiles of H37Rv, H37Ra, and BCG, which we believe will potentially provide a better understanding of H37Rv pathogenesis, H37Ra attenuation, and BCG immuno protection.

Prevalence and Molecular Characteristics Based on Whole Genome Sequencing of Mycobacterium tuberculosis Resistant to Four Anti-Tuberculosis Drugs from Southern Xinjiang, China

Objective

Drug-resistant tuberculosis is a major public health problem, especially in the southern region of Xinjiang, China; however, there is little information regarding drug resistance profiles and mechanism of Mycobacterium tuberculosis in this area. The aim of this study was to determine the prevalence and molecular characteristics of M. tuberculosis resistant to four anti-tuberculosis drugs from this area.

Methods

Three hundred and forty-six isolates from the southern region of Xinjiang, China were included and used to perform phenotypic drug susceptibility testing and whole genome sequencing (WGS). Mutations in seven loci associated with drug resistance, including rpoB for rifampicin (RMP), katG, inhA promoter and oxyR-ahpC for isoniazid (INH), rrs 530 and 912 loops and rpsL for streptomycin (STR), and embB for ethambutol (EMB), were characterized.

Results

Among 346 isolates, 106, 60, 70 and 29 were resistant to INH, RMP, STR and EMB, respectively; 132 were resistant to at least one of the four anti-tuberculosis drugs and 51 were multi-drug resistant (MDR). Beijing genotype and retreated patients showed a significantly increased risk for developing MDR tuberculosis. Compared with the phenotypic data, the sensitivity and specificity for WGS to predict resistance were 96.7% and 98.6% for RMP, 75.5% and 97.1% for INH, 68.6% and 99.6% for STR, 93.1% and 93.7% for EMB, respectively. The most common mutations conferring RMP, INH, STR and EMB resistance were Ser450Leu (51.7%) in rpoB, Ser315Thr (44.3%) in katG, Lys43Arg (35.7%) in rpsL and Met306Val (24.1%) in embB.

Conclusion

This study provides the first information on the prevalence and molecular characters of drug resistant M. tuberculosis in the southern region of Xinjiang, China, which will be helpful for choosing early detection methods for drug resistance (ig, molecular methods) and subsequently initiation of proper therapy of tuberculosis in this area.

Epidemiological characteristics and trends of notifiable infectious diseases in China from 1986 to 2016

Background

Since the 1980s, China has undergone significant social change and the incidence of infectious diseases has also changed considerably. Here, we report the epidemiological features and changes in notifiable infectious diseases in China from 1986 to 2016 to explore the factors contributing to the successful control of infectious diseases and the challenges faced in the prevention and control of infectious diseases.

Methods

The data of notifiable infectious diseases in China from 1986 to 2016 were collected from the monthly analysis report of the National Infectious Disease Surveillance System. Joinpoint regression models were used to examine incidence and mortality trends from 1986 to 2016. IBM SPSS Statistics version 22.0, Excel 2010 and R x64 3.5.2 were used for data analysis.

Results

A total of 132 858 005 cases of notifiable infectious diseases were reported over these 31 years, with an average yearly incidence of 342.14/100 000. There were 284 694 deaths with an average yearly mortality rate of 0.73/100 000. The overall incidence and overall mortality of notifiable infectious diseases both showed a "U" distribution (ie, a decrease, stable, an increase, stable again). The top five diseases in terms of incidence were hand, foot and mouth disease, viral hepatitis, tuberculosis, other infectious causes of diarrhea and dysentery, accounting for 78.0% of all reported cases. The top five causes of death were HIV/AIDS, rabies, tuberculosis, viral hepatitis and epidemic encephalitis B, which accounted for 76.07% of all mortalities. The diseases with the top five fatality rates were rabies, H5N1, H7N9, HIV/AIDS and plague, with rates of 91.06%, 66.07%, 38.51%, 25.19% and 10.31%, respectively.

Conclusions

This analysis will benefit the future monitoring of infectious diseases and public health measures in China.

Epidemiological Characteristics and Trends of Registered Leprosy Cases in China From 2004 to 2016

Leprosy is an infectious disease caused by Mycobacterium leprae. China was once one of the countries with severe leprosy epidemics, but its incidence has remained low in recent years. Despite this, there has been no decrease in its incidence more recently, and it is still a public health problem which needs to be controlled. In this study, we analyzed the epidemiological characteristics and trends in the detection rate of new cases of leprosy in China between 2004 and 2016. There were 4,519 cases of leprosy in 28 provinces, municipalities, and autonomous regions between 2004 and 2016, and the total incidence was 0.02815 (per 100,000 individuals) and 21 deaths. The overall incidence of leprosy showed an inverted "V" distribution (i.e., an increase followed by a decrease). Yunnan, Sichuan, Guangdong, Guizhou, and Guangxi were the top five regions with the highest incidence rates, and they accounted for 68.7% of the total cases. There were more male patients than female patients, and peasants accounted for 71.7% of the leprosy cases. The patients with leprosy in China were mainly concentrated in the age-group 15-44 years, as this group accounted for 57.2% of the total cases. The purpose of this study is to explore the epidemiology of leprosy in China. This analysis will be useful for future monitoring of leprosy and establishment of public health measures in China, in keeping with the "Programme for the Elimination of Leprosy in China 2011-2020."

Role of miR-133a in regulating TGF-β1 signaling pathway in myocardial fibrosis after acute myocardial infarction in rats

OBJECTIVE

The aim of this research was to explore the effect of microRNA-133a (miR-133a) on myocardial fibrosis and cardiac function after myocardial infarction in rats, and to investigate the possible regulatory mechanism.

MATERIALS AND METHODS

Myocardial infarction model was successfully established in rats by ligation of the left anterior descending coronary artery. After miR-133a overexpression in rats myocardium, cardiac function was examined by echocardiography. Meanwhile, the degree of myocardial fibrosis was detected by Masson staining. In addition, the expression of α-smooth muscle actin (α-SMA) in cardiomyocytes was detected by immunohistochemistry. Quantitative Real-time polymerase chain reaction (qRT-PCR) was performed to analyze the expression level of miR-133a in the junction of myocardial infarction. The mRNA expressions of transforming growth factor-β1 (TGF-β1), connective tissue growth factor (CTGF), collagen type 1 (col 1), collagen type 3 (col 3) and α-SMA were measured by qRT-PCR as well. Furthermore, the protein levels of the above genes were detected by Western blotting.

RESULTS

MiR-133a expression in the infarct border zone of myocardial tissue was significantly decreased on the 28th day after myocardial infarction surgery (p<0.05). In addition, up-regulation of miRNA-133a in myocardial tissue of rats with myocardial infarction could remarkably improve cardiac function and reduce collagen volume fraction. Furthermore, the mRNA and protein expression levels of TGF-β1, CTGF, col1, col3, α-SMA in myocardial tissue were obviously decreased after miRNA-133a up-regulation (p<0.001).

CONCLUSIONS

Overexpression of miR-133a down-regulates the mRNA and protein levels of TGF-β1 and CTGF after myocardial infarction. Moreover, this may eventually reduce myocardial collagen deposition, inhibit myocardial fibrosis and improve cardiac function.

Detection of Resistance to Fluoroquinolones and Second-Line Injectable Drugs Among Mycobacterium tuberculosis by a Reverse Dot Blot Hybridization Assay

Background

Reliable and timely determination of second-line drug resistance is essential for early initiation effective anti-tubercular treatment among multi-drug resistant (MDR) patients and blocking the spread of MDR and extensively drug-resistant tuberculosis. Molecular methods have the potency to provide accurate and rapid drug susceptibility results. We aimed to establish and evaluate the accuracy of a reverse dot blot hybridization (RDBH) assay to simultaneously detect the resistance of fluoroquinolones (FQs), kanamycin (KN), amikacin (AMK), capreomycin (CPM) and second-line injectable drugs (SLIDs) in Mycobacterium tuberculosis.

Methods

We established and evaluated the accuracy of the RDBH assay by comparing to the phenotypic drug susceptibility testing (DST) and sequencing in 170 M. tuberculosis, of which 94 and 27 were respectively resistant to ofloxacin (OFX) and SLIDs.

Results

The results show that, compared to phenotypic DST, the sensitivity and specificity of the RDBH assay for resistance detection were 63.8% and 100.0% for OFX, 60.0% and 100.0% for KN, 61.5% and 98.1% for AMK, 50.0% and 99.3% for CPM, and 55.6% and 100% for SLIDs, respectively; compared to sequencing, the sensitivity and specificity of the RDBH assay were 95.2% and 100.0% for OFX, 93.8% and 100.0% for SLIDs or KN (both based on mutations in rrs 1400 region and eis promoter), and 91.6% and 100.0% for AMK or CPM (both based on mutations in rrs 1400 region), respectively. The turnaround time of the RDBH assay was 7 h for testing 42 samples.

Conclusion

Our data suggested that compared to sequencing, the RDBH assay could serve as a rapid and reliable method for testing the resistance of M. tuberculosis against OFX and SLIDs, enabling early administration of appropriate treatment regimens among MDR tuberculosis patients.

Trends in the Prevalence and Antibiotic Resistance of Non-tuberculous Mycobacteria in Mainland China, 2000-2019: Systematic Review and Meta-Analysis

Background: China is a high-burden country of tuberculosis. The proportion of diseases caused by non-tuberculous mycobacteria (NTM) has increased, seriously affecting the prevention, control, and management of tuberculosis (TB) and posing a significant threat to human health. However, there is a lack of an organized monitoring system for NTM such as that used for tuberculosis. Comprehensive data on patient susceptibility, dominant species, and drug resistance profiles are needed to improve the treatment protocols and the management of NTM. Methods: Primary research reports of NTM clinical specimens from mainland China published between January 1, 2000 and May 31, 2019 were retrieved from four online resources (BIOSIS, Embase, PubMed, and Web of Science) and three Chinese medical literature databases (CNKI, Wanfang, and Vip) as the Preferred Reporting Items for Systematic Reviews and Meta-Analyses. Results: In total, 339 publications were included in the systematic review, 129 were used in the drug susceptibility analysis, and 95 were used in the meta-analysis. Traditional culture using Lowenstein-Jensen slants combined with P-nitrobenzene acid and thiophene-2-carboxylic acid hydrazine differential medium and proportional method was most commonly used for the isolation, identification, and drug susceptibility testing of NTM in China. The crude isolation rate for NTM among TB suspected cases was 4.66-5.78%, while the proportion of NTM among Mycobacterium isolates was 11.57%. Mycobacterium abscessus and Mycobacterium avium complex were the most common clinical NTM species. NTM only showed general sensitivity to ethambutol, linezolid, clofazimine, amikacin, tobramycin, and clarithromycin. Conclusions: The prevalence of NTM in China has shown a decreasing trend. M. abscessus was replaced as the dominant species by Mycobacterium intracellulare over the course of the study. The geographic diversity of different species showed the effects of environmental and economic factors on the distribution of NTM and indicated that there were important factors still not identified. While there were only a limited number of antibiotics to which NTM showed any sensitivity, the drug resistance profiles of the isolates were highly variable and thus more caution should be taken when empirically treating NTM infection.

Genomic Analysis Identifies Mutations Concerning Drug-Resistance and Beijing Genotype in Multidrug-Resistant Mycobacterium tuberculosis Isolated From China

Development of modern genomics provides us an effective method to understand the molecular mechanism of drug resistance and diagnose drug-resistant Mycobacterium tuberculosis. In this study, mutations in 18 genes or intergenic regions acquired by whole-genome sequencing (WGS) of 183 clinical M. tuberculosis strains, including 137 multidrug-resistant and 46 pan-susceptible isolates from China, were identified and used to analyze their associations with resistance of isoniazid, rifampin, ethambutol, and streptomycin. Using the proportional method as the gold standard method, the accuracy values of WGS to predict resistance were calculated. The association between synonymous or lineage definition mutations with different genotypes were also analyzed. The results show that, compared to the phenotypic proportional method, the sensitivity and specificity of WGS for resistance detection were 94.2 and 100.0% for rifampicin (based on mutations in rpoB), 90.5 and 97.8% for isoniazid (katG), 83.0 and 97.8% for streptomycin (rpsL combined with rrs 530 loop and 912 loop), and 90.9 and 65.1% for ethambutol (embB), respectively. WGS data also showed that mutations in the inhA promoter increased only 2.2% sensitivity for INH based on mutations in katG. Synonymous mutation rpoB A1075A was confirmed to be associated with the Beijing genotype. This study confirmed that mutations in rpoB, katG, rrs 530 loop and 912 loop, and rpsL were excellent biomarkers for predicting rifampicin, isoniazid, and streptomycin resistance, respectively, and provided clues in clarifying the drug-resistance mechanism of M. tuberculosis isolates from China.

A real-time PCR assay based on a specific mutation of PstS1 gene for detection of M. bovis strains

The Mycobacterium tuberculosis complex (MTBC) is composed of several genetically related and pathogenic mycobacterial species, including M. tuberculosis, M. bovis and M.africanum et al. In our previous study, we found that M. bovis strains had a unique SNP located in position 1055 in the sequence of the pstS1 gene in which a T was substituted by a C. In this study, specific primers and MGB probes were designed according to the mutation in PstS1 gene, and a sensitive, specific and rapid real-time PCR assay for M. bovis was established. Then the assay was used to detect M. bovis in simulation samples. The minimum detectable concentration is 10¹ copies for M. bovis DNA. The standard curve showed correlation coefficient between threshold cycle and PstS1 gene fragment copy number was 0.997 and slope is -3.144. The minimum detectable concentration is 10¹ cells/ml for simulation sample. In addition, M.bovis strain 93006, 14 clinical BCG stains and 7 clinical M.bovis strain showed positive while the other strains showed negative results, which proved good specificity. This assay had high sensitivity and specificity for identification of M. bovis from the simulation specimens. The assay can be applied for epidemiological and ecological surveillance of M. bovis strains.

Polymorphism of MPT64 and PstS1 in Mycobacterium tuberculosis is not likely to affect relative immune reaction in human

BACKGROUND

MPT64 and PstS1 are the earliest known immune-dominant antigens of Mycobacterium tuberculosis and have been commonly used as candidates in the diagnosis of tuberculosis.

METHODS

We constructed recombinant plasmids pET-32a-Rv0934 and pET-32a-Rv1980c to express both wild and mutant forms of MPT64 and PstS1 and purified them. From November 9 to December 9, 2016, and November 9 to December 10, 2017, 96 patients with tuberculosis, 53 patients without tuberculosis, and 96 healthy volunteers were enrolled in this study. We used the purified proteins as antigens to perform T-spot and enzyme-linked immunosorbent assay (ELISA) for samples obtained from healthy volunteers and tuberculosis patients.

RESULTS

Regarding T-spot, the area under the curve (AUC) values for MPT64-wild protein (MPT64-H37Rv) and MPT64-mutant protein (MPT64-FJ05395) were 0.723 and 0.750, respectively. The AUC values for PstS1-H37Rv, PstS1-FJ05132, and PstS1-JL06035 were 0.817, 0.796, and 0.745, respectively. With regard to ELISA, the AUC values for MPT64-H37Rv and MPT64-FJ05395 were 0.525 and 0.528, respectively, while those for PstS1-H37Rv, PstS1-FJ05132, PstS1-JL06035 were 0.588, 0.509, and 0.560, respectively. There was no difference between wild and mutant proteins when we used them as antigens to perform T-spot and ELISA assays.

CONCLUSION

MPT64 and PstS1 are likely candidate diagnostic antigens for M tuberculosis T-spot test, at least in combination with other proteins. Polymorphisms of MPT64 and PstS1 had little effect on cell-mediated and humoral immunity in the host.

Effects of dietary calcium pyruvate on gastrointestinal tract development, intestinal health and growth performance of newly weaned piglets fed low-protein diets

AIM

This study was carried out to investigate the effects of dietary calcium pyruvate supplementation on growth performance and intestinal health of weaned piglets fed low-protein diets.

METHODS AND RESULTS

After a 7-day adaptation period, 60 individually housed piglets (Duroc × Yorkshire-Landrace) weaned at 28 days of age were randomly assigned to receive one of three treatments (20 pigs/treatment) for 28 days: control diet (20·0% crude protein [CP]), low-protein diet (15·5% CP), and experimental (15·5% CP + 1·8% calcium pyruvate). At the end of the experiment, six piglets from each diet group were slaughtered and blood and tissue samples were collected. Compared with the control group, feeding piglets with 15·5% CP decreased the daily body weight gain; lengths of the duodenum, jejunum and ileum; and weights of the stomach, duodenum, jejunum and ileum (P < 0·05), while 15·5% CP + 1·8% calcium pyruvate supplementation removed those differences (P > 0·05). Compared with the control group, the diarrhoea incidence and relative richness of Firmicutes in the colon contents of piglets in both the 15·5% CP and 15·5% CP + 1·8% calcium pyruvate groups was decreased. The relative richness of Bacteriodetes in the colon contents of piglets was higher in the 15·5% CP + 1·8% calcium pyruvate group than in the control and 15·5% CP groups (P < 0·05).

CONCLUSION

Calcium pyruvate supplementation for four weeks removed the negative effects of a low-protein diet on the gastrointestinal tract development and daily body weight gain of weaned piglets.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study showed that supplementing a low-protein diet with calcium pyruvate, an effective alternative metabolic fuel to amino acids, was beneficial in improving the intestinal health and maximizing the growth of newly weaned piglets.

Case report: A patient coinfected by Borrelia burgdorferi sensu lato and spotted fever group Rickettsiae in Urumqi, China

RATIONALE

Both Borrelia burgdorferi sensu lato and spotted fever group Rickettsiae (SFGR) are pathogens carried by ticks. There is a possibility of co-infection with these tick-borne diseases.

PATIENT CONCERNS

Male patient, 63 years-of-age, admitted to hospital with skin rash presenting for 1 week and fever with cough and expectoration for 3 days before admission.

DIAGNOSES

We diagnosed that the patient was co-infected by B burgdorferi sl and SFGR using laboratory test results and the patient's clinical manifestations.

INTERVENTIONS

The patient started therapy with oral minocycline, then levofloxacin by intravenous injection for SFGR. Meanwhile, he was treated with penicillin G sodium, cefoperazone sulbactam sodium and ceftriaxone by intravenous injection for B burgdorferi sl.

OUTCOMES

After the patient was in stable condition, he was discharged from hospital.

LESSONS

This case report highlights the possibility of co-infection by 2 tick-borne diseases in Urumqi, Xinjiang Uygur Autonomous Region, China. The antibiotic therapy should be based on the detection of pathogenic bacteria, and the different susceptibilities of co-infecting bacteria should be considered.

Cross-resistance of isoniazid, para-aminosalicylic acid and pasiniazid against isoniazid-resistant Mycobacterium tuberculosis isolates in China

OBJECTIVES

Pasiniazid is a chemical complex of isoniazid (INH) and para-aminosalicylic acid (PAS). The aim of this study was to explore the cross-resistance of INH, PAS and pasiniazid against INH-resistant Mycobacterium tuberculosis isolates in China.

METHODS

A Microplate alamarBlue® Assay was performed to determine the minimum inhibitory concentrations (MICs) of INH, PAS and pasiniazid against 109 INH-resistant M. tuberculosis isolates. A statistical analysis of the relationship between different genotypes, gene mutations, and INH, PAS or pasiniazid susceptibility was then performed.

RESULTS

Among the 109 INH-resistant isolates, 13 (11.9%) and 21 (19.3%) showed resistance to PAS and pasiniazid, respectively. Among the 13 PAS-resistant M. tuberculosis isolates, 11 remained susceptible to pasiniazid. Of 63 INH-resistant isolates harbouring mutations in katG, the inhA promoter or the oxyR-ahpC intergenic region, 52 remained susceptible to pasiniazid. Moreover, 11 of 13 pasiniazid-resistant isolates carried mutations in katG, the inhA promoter or the oxyR-ahpC intergenic region.

CONCLUSION

Taken together, these results demonstrate that PAS resistance and mutations in thekatG gene, inhA promoter or oxyR-ahpC intergenic region in INH-resistant M. tuberculosis have little effect on pasiniazid susceptibility.

A New Single Gene Differential Biomarker for Mycobacterium tuberculosis Complex and Non-tuberculosis Mycobacteria

Background

Tuberculosis (TB) and non-tuberculous mycobacteriosis are serious threats to health worldwide. A simple non-sequencing method is needed for rapid diagnosis, especially in less experienced hospitals, but there is no specific biomarker commonly used for all mycobacteria. The ku gene of the prokaryotic error-prone non-homologous end joining system (NHEJ) has the potential to be a highly specific detection biomarker for mycobacteria.

Methods

A total of 7294 mycobacterial genomes and 14 complete genomes of other families belonging to Corynebacteriales with Mycobacteriaceae were downloaded and analyzed for the existence and variation of the ku gene. Mycobacterium tuberculosis complex (MTBC) and non-tuberculosis mycobacteria (NTM)- specific primers were designed and the actual amplification and identification efficiencies were tested with 150 strains of 40 Mycobacterium species and 10 kinds of common respiratory pathogenic bacteria.

Results

The ku gene of the NHEJ system was ubiquitous in all genome sequenced Mycobacterium species and absent in other families of Corynebacteriales. On the one hand, as a single gene non-sequencing biomarker, its specific primers could effectively distinguish mycobacteria from other bacteria, MTBC from NTM, which would make the clinical detection of mycobacteria easy and have great clinical practical value. On the other hand, the sequence of ku gene can effectively distinguish NTM to species level with high resolution.

Conclusion

The Ku protein existed before the differentiation of Mycobacterium species, which was an important protein involved in maintaining of the genome’s integrity and related to the special growth stage of mycobacteria. It was rare in prokaryotes. These features made it a highly special differential biomarker for Mycobacterium.

Synergistic activities of clofazimine with moxifloxacin or capreomycin against Mycobacterium tuberculosis in China

Clofazimine (CFZ) is a promising candidate drug for use in the management of multidrug-resistant tuberculosis (MDR-TB) patients. In this study, the minimum inhibitory concentration (MIC) method and checkerboard method were used to investigate potential synergies between CFZ and moxifloxacin (MOX) or capreomycin (CAP). Thirty Mycobacterium tuberculosis strains were collected, including 13 MDR strains, 2 extensively drug-resistant (XDR) strains, 3 pan-sensitive strains and 12 strains resistant to other drugs. When the minimum fractional inhibitory concentration indexes (FICIs) were calculated, synergy was found in 21 (70.00%) M. tuberculosis strains against the CFZ/CAP combination and 29 (96.67%) against the CFZ/MOX combination. When the maximum FICIs were calculated, 10 of 15 MDR/XDR strains and 2 of 15 other drug-resistant or pan-sensitive strains showed antagonism against the CFZ/CAP combination, whilst 8 of 15 MDR/XDR strains and 1 of 15 other drug-resistant or pan-sensitive strains showed antagonism against the CFZ/MOX combination, respectively. In conclusion, these findings demonstrate that the combination of CFZ and MOX shows better synergism than the combination of CFZ and CAP. The MDR/XDR isolates are more likely to show antagonism than the other drug-resistant or pan-sensitive strains in both the CFZ/MOX and CFZ/CAP combinations. CFZ in combination with MOX may be a promising drug regimen for the treatment of MDR-TB, particularly for susceptible M. tuberculosis infections.

Ribokinase screened from T7 phage displayed Mycobacterium tuberculosis genomic DNA library had good potential for the serodiagnosis of tuberculosis

Tuberculosis caused by Mycobacterium tuberculosis (M. tuberculosis) is the leading cause of death among infectious diseases in the worldwide. Lack of more sensitive and effective diagnostic reagents has increased the awareness of rapid diagnosis for tuberculosis. In this study, T7 phage displayed genomic DNA library of M. tuberculosis was constructed to screen the antigens that specially bind with TB-positive serum from the whole genome of M. tuberculosis and to improve the sensitivity and specificity of tuberculosis serological diagnosis. After three rounds of biopanning, results of DNA sequencing and BLAST analysis showed that 19 positive phages displayed four different proteins and the occurrence frequency of the phage which displayed ribokinase was the highest. The results of indirect ELISA and dot immunoblotting indicated that representative phages could specifically bind to tuberculosis-positive serum. The prokaryotic expression vector containing the DNA sequence of ribokinase gene was then constructed and the recombinant protein was expressed and purified to evaluate the serodiagnosis value of ribokinase. The reactivity of the recombinant ribokinase with different clinical serum was detected and the sensitivities and specificities in tuberculosis serodiagnosis were 90% and 86%, respectively by screening serum from tuberculosis patients (n = 90) and uninfected individuals (n = 90) based on ELISA. Therefore, this study demonstrated that ribokinase had good potential for the serodiagnosis of tuberculosis.

[Detection and prevention of nitrous oxide iatrogenic pollution in dental treatments]

Nitrous oxide (N(2)O), also known as laughing gas, is widely used in the dental offices as a common inhaled sedative analgesic gas to reduce anxiety and pain during treatment. Studies have shown that long-term exposure to higher concentrations of laughing gas may have a certain impact on the health of medical staff, while currently research on iatrogenic pollution in applications of laughing gas in oral therapy is not sufficient. In the United States and Europe, the condition of applications of laughing gas is relativrly mature, and there are related regulations and recommended measures to prevent and control iatrogenic pollution. However, studies in these countries still show that there is iatrogenic pollution in the clinical use of laughing gas and lack of uniform detection measures. While, in China, there is little research on the health effects of laughing gas on medical staff and on how to detect and control nitrous oxide pollution. This review is about the hazards, monitoring and control of clinical application of nitrous oxide.

Polymorphisms of human T cell epitopes of Mycobacterium tuberculosis indicate divergence of host immune pressure on different categories of proteins

Mycobacterium tuberculosis is the most successful pathogen with multiple mechanisms to subvert host immune response, resulting in insidious disease. There are few studies on whether the bacteria undergo antigenic variation in response to host immune pressure. Studies on T cell epitopes of M. tuberculosis can help us further understand the mechanism of interaction between the bacteria and host immune system. Here, we selected 180 M. tuberculosis complex in China, amplified 462 experimentally verified human T cell epitopes, sequenced and compared the results to analyze the diversity of those epitopes. It proved that a large majority human T cell epitopes of M. tuberculosis are conserved. However, polymorphisms of T cell epitopes indicated different categories of proteins suffered divergence from host immune pressure. Moreover, Beijing strains are more conservative than non-Beijing strains in T cell epitopes, which might make them easier to transmit than non-Beijing strains.

In Vitro Activity of β-Lactams in Combination with β-Lactamase Inhibitors against Mycobacterium tuberculosis Clinical Isolates

OBJECTIVES

Evaluating the activity of nineteen β-lactams in combination with different β-lactamase inhibitors to determine the most potent combination against Mycobacterium tuberculosis (MTB) in vitro.

METHODS

Drug activity was examined by drug susceptibility test with 122 clinical isolates from China. Mutations of blaC and drug targets ldtMt1 , ldtMt2 , dacB2, and crfA were analyzed by nucleotide sequencing.

RESULTS

Tebipenem (TBM) in combination with clavulanate (CLA) exhibited the highest anti-TB activity. The MIC of β-lactam antibiotics was reduced most evidently in the presence of CLA, compared to avibactam (AVI) and sulbactam (SUB). Eight polymorphism sites were identified in blaC, which were not associated with β-lactams resistance. Interestingly, one strain carrying G514A mutation in blaC was highly susceptible to β-lactams regardless of the presence of inhibitors. The transpeptidase encoding genes, ldtMt1 , ldtMt2 , and dacB2, harboured three mutations, two mutations, and one mutation, respectively, but no correlation was found between these mutations and drug resistance.

CONCLUSION

The activity of β-lactams against MTB and different synergetic effect of β-lactamase inhibitors were indicated. TBM/CLA exhibited the most activity and has a great prospect in developing novel anti-TB regimen; however, further clinical research is warranted. Moreover, the resistance to the β-lactam antibiotics might not be conferred by single target mutation in MTB and requires further studies.

Single-nucleotide polymorphisms related to fluoroquinolone and aminoglycoside resistance in Mycobacterium avium isolates

Objective

The relationships between fluoroquinolone and aminoglycoside resistance and single-nucleotide polymorphisms (SNPs) in gyrA, gyrB, and rpsL genes were investigated in 95 clinical isolates of Mycobacterium avium from China.

Methods

Fluoroquinolone and aminoglycoside resistance were determined by the broth microdilution method. GyrA, gyrB, and rpsL were sequenced, SNPs were identified, and the corresponding amino acid mutations were recorded.

Results

The M. avium isolates displayed high levels of ofloxacin (93.68%), ciprofloxacin (92.63%), and streptomycin (65.26%) resistance. Moxifloxacin (18.95%) and amikacin (2.11%) were highly active against the strains. Fluoroquinolone resistance involving gyrA and gyrB gene mutations was identified. For gyrA, the most frequent SNPs were T→C (71/95, 74.74%), followed by A→G (64/95, 67.37%) and T→C (62/95, 65.26%). The amino acid mutations occurred mainly at Gly2444Asp (GGT→GAT) (20/95, 21.05%), Ala2445Ser (GCC→TCC) (20/95, 21.05%), Ala2447Val (GCC→GTC) (20/95, 21.05%), Val2449Ile (GTC→ATC) (20/95, 21.05%), and Glu2450Gln (GAA→CAA) (20/95, 21.05%). Prominent SNPs in gyrB included A→C (69/95, 72.63%), C→T (51/95, 53.68%), and T→G (29/95, 30.53%), and their amino acid substitutions were Ile2160Val (ATT→GTT) (21/95, 22.11%), Ile2160Met (ATT→ATG) (20/95, 21.05%), and Ile2273Leu (ATC→CTC) (11/95, 11.58%). Among the strains with aminoglycoside resistance, SNPs in rpsL were identified mostly at position G→A (73/95, 76.84%). G→C (21/95, 22.11%) was commonly seen. The amino acid mutations primarily involved Ala1539985Thr (GCC→ACC) (19/95, 20.00%), His1539992Asp (CAC→GAC) (19/95, 20.00%), and Gln-1539983Glu (CAG→GAG) (18/95, 18.95%).

Conclusion

Our study provides valuable information that could be used for the future diagnosis and treatment of M. avium disease.

IncA/C plasmids conferring high azithromycin resistance in vibrio cholerae

Azithromycin (AZM) is a clinically important antibiotic against Vibrio cholerae, especially for inhibiting V. cholerae colonisation of the intestine and for the treatment of severe cholera in children and pregnant women. An IncA/C plasmid was isolated from two high minimum inhibitory concentration (MIC) AZM-resistant V. cholerae strains of the two mainly pathogenic serogroups (O1 and O139) isolated in China. In the 172 predicted open reading frames (ORFs), 16 genes were related to antibiotic resistance, of which 5 were well-defined genes associated with macrolide resistance. The five macrolide resistance genes distributed in two clusters, mphR-mrx-mph(K) and mel-mph2, flanked by insertion sequence elements and involving two kinds of resistance mechanism. Deletion of the complete region of the two clusters deceased the AZM MIC from ≥64 µg/mL to ≤0.5 µg/mL. This IncA/C plasmid shows great ability to accumulate antibiotic resistance genes. In addition to 11 resistance genes to other antibiotics, 5 macrolide resistance genes with different function were gathered repeatedly through transposition on one plasmid. This genotype could not be simply explained by antibiotic stress applied on the host from the environment or treatment. These phosphorylases and transmembrane transporters might be involved in the transport and metabolism of other non-antibiotic substances, enabling this kind of plasmid to propagate better in the host.

CTL immunogenicity of Rv3615c antigen and diagnostic performances of an ESAT-6/CFP-10/Rv3615c antigen cocktail for Mycobacterium tuberculosis infection

T cell immune responses have played pivotal roles in host immune protection against Mycobacterium tuberculosis (MTB) infection. MTB specific antigen, Rv3615c (EspC), was identified to be as immunodominant as the well-known ESAT-6 and CFP-10, and has brought promising expectations to more sensitive T-cell based diagnosis and vaccine development. However, limited knowledge about the immunogenicity and diagnostic values of this antigen has restricted its application in clinical practice. Herein, the Rv3615c antigen was identified as a robust CTL immunoantigen with broadly cross-human leucocyte antigen (HLA) allele recognized peptides which may contribute to the broad recognition of Rv3615c antigen among the population. A three-antigen-cocktail (3-Ag-cocktail) comprising of ESAT-6, CFP-10 and Rv3615c was investigated in a multicenter, randomized and double-blinded study to evaluate its clinical diagnostic performances. A significantly improved sensitivity was demonstrated against the 3-Ag-cocktail compared with that against ESAT-6 and CFP-10. Both responsive magnitude and sensitivity were significantly lower in patients concurrently suffering from cancer, indicating its restriction in diagnosis of immunocomprised patients. In conclusion, inclusion of the Rv3615c antigen with multiple HLA restricted CTL epitopes would benefit the T-cell based diagnosis of MTB infection.

Isolation and identification of multiple drug resistant nontuberculous mycobacteria from organs of cattle produced typical granuloma lesions

Nontuberculosis mycobacteria are widespread in the environment and some are zoonotic. 320 tissue samples with visible lesions were obtained from dairy cows and examined by histopathology. Eleven samples showed typical granulomatous lesions and a total of 8 strains were cultured. Three genes (16S rRNA, hsp65 and rpoB) were sequenced for species identification. All mycobacterial isolates were tested for rifampicin, isoniazid, ethambutol, streptomycin, capreomycin, kanamycin, para-aminosalicylic acid susceptibility. Six strains were identified as M. fortuitum, 1 was M. avium, 1 was M. conceptionense, isolated from cattle for the first time. Seven of the 8 isolated strains showed multiple drug resistance.

Molecular Characteristics of Mycobacterium tuberculosis Strains Isolated from Cutaneous Tuberculosis Patients in China

Cutaneous tuberculosis (CTB) is probably underreported due to difficulties in detection and diagnosis. To address this issue, genotypes of Mycobacterium tuberculosis strains isolated from 30 patients with CTB were mapped at multiple loci, namely, RD105 deletions, spacer oligonucleotides, and Mycobacterial Interspersed Repetitive Unit-Variable Number Tandem Repeats (MIRU-VNTRs). Fifty-eight strains of pulmonary tuberculosis (PTB) were mapped as experimental controls. Drug resistance-associated gene mutations were determined by amplicon sequencing of target regions within 7 genes. Beijing family isolates were the most prevalent strains in CTB and PTB. MIRU-VNTR typing separated the Beijing strains from the non-Beijing strains, and the majority of CTB could be separated from PTB counterparts. Drug resistance determining regions showed only one CTB strain expressing isomazid resistance. Thus, while the CTB strains belonged to the same phylogenetic lineages and sub-lineages as the PTB strains, they differed at the level of several MIRU-VNTRs and in the proportion of drug resistance.

Evaluation of Rv0220, Rv2958c, Rv2994 and Rv3347c of Mycobacterium tuberculosis for serodiagnosis of tuberculosis

Tuberculosis (TB), the leading cause of death among infectious diseases worldwide, is caused by Mycobacterium tuberculosis (M. tuberculosis). Early accurate diagnosis means earlier prevention, treatment and control of TB. To confirm efficient diagnostic antigens for M. tuberculosis, the serodiagnosis value of four recombinant proteins including Rv0220, Rv2958c, Rv2994 and Rv3347c was evaluated in this study. The specificities and sensitivities of four recombinant proteins were determined based on enzyme‐linked immunosorbent assay (ELISA) by screening sera from smear‐positive pulmonary TB patients (n = 92), uninfected individuals (n = 60) and patients with Mycoplasma pneumoniae (n = 32) that potentially cross‐react with M. tuberculosis. The ELISAs showed that Rv0220, Rv2958c, Rv2994 and Rv3347c exhibited high specificities and sensitivities in detecting immunoglobulin G (IgG) antibody, with 98.3/91.3%, 91.7/85.9%, 93.3/89.1% and 93.3/80.4% respectively. According to the receiver‐operating characteristic (ROC) analysis, the area under the ROC of the target proteins was 0.988, 0.969, 0.929 and 0.945 respectively. Western blot was established to evaluate the immunoreactivities of target proteins to mice and human sera. Results demonstrated that Rv0220, Rv2958c, Rv2994 and Rv3347c could specifically recognize TB‐positive sera and the sera of mice immunized with the corresponding protein. Thus, Rv0220, Rv2958c, Rv2994 and Rv3347c were valuable potential diagnostic antigens for M. tuberculosis.

Antimicrobial susceptibility and MIC distribution of 41 drugs against clinical isolates from China and reference strains of nontuberculous mycobacteria

To treat nontuberculous mycobacteria (NTM) infections more optimally, further research pertaining to mycobacterial susceptibility to antimicrobial agents is required. A total of 82 species of NTM reference strains and 23 species of NTM clinical isolates were included. Minimum inhibitory concentrations (MICs) for 41 drugs were determined using the microdilution method in cation-adjusted Mueller-Hinton broth. The results showed that most of the NTM were susceptible to aminoglycosides, quinolones, three macrolides (clarithromycin, azithromycin and roxithromycin), cefmetazole, linezolid and capreomycin. Rapidly growing mycobacterium strains were additionally susceptible to cefoxitin, clofazimine, rifapentine, doxycycline, minocycline, tigecycline, meropenem and sulfamethoxazole, whereas slowly growing mycobacterium strains were additionally susceptible to rifabutin. This study on the susceptibility of NTM includes the largest sample size of Chinese clinical isolates and reference strains. NTM species-specific drug susceptibility patterns suggested that it is urgent to identify the species of NTM, to normalise the treatment of NTM infectious disease and to clarify the resistance mechanisms of NTM.

[Analysis on human T cell epitopes polymorphisms of five specific antigens of Mycobacterium tuberculosis in 13 areas of China]

OBJECTIVE

To investigate the polymorphisms of the coding gene and the human T cell epitopes of antigen GlnA1, Mpt70, LppX, GroES and LpqH on Mycobacterium tuberculosis complex (MTBC) strains in thirteen provinces of China.

METHODS

A total of 173 clinical MTBC isolates from thirteen provinces were selected to test the gene sequences of the five antigens, using PCR and DNA sequencing methods. Sequences were compared and sliced by BioEdit, and the variations of the human and nonhuman T cell epitopes were analyzed. The rates on synonymous mutation (dS), non-synonymous mutation (dN) and dN/dS values were calculated by Mega 6.0 software.

RESULTS

Among the 173 strains, there were two non-synonymous mutations in the non-epitope region of glnA1, one non-synonymous mutations in epitope domain of mpt70, one non-synonymous mutation and one synonymous mutation in the epitope domain of lpqH; while groES showed no mutation. lppX had five non-synonymous mutations and one synonymous mutation in the epitope domain. Nine strains presented higher polymorphism at the same gene locus of position 152 in lppX. And seven of the fifteen epitopes contained in lppX were altered and the dN/dS value of this gene was 0.19.

CONCLUSIONS

Data from the human T cell epitope domains of MTBC antigens Mpt70, LppX and LpqH contained epitope diversity, indicated that these antigens may have involved in diversifying the selection to evade the host immunity. GlnA1 had the polymorphism in epitope domain, which might have little influence on the immuno-response. While GroES seemed relatively conservative, it could play an important role on identification, diagnosis and the development of potential Mycobacterium tuberculosis vaccine.