Localization of EccA3 at the growing pole in Mycobacterium smegmatis.

BACKGROUND: Bacteria require specialized secretion systems for the export of molecules into the extracellular space to modify their environment and scavenge for nutrients. The ESX-3 secretion system is required by mycobacteria for iron homeostasis. The ESX-3 operon encodes for one cytoplasmic component (EccA3) and five membrane components (EccB3 - EccE3 and MycP3). In this study we sought to identify the sub-cellular location of EccA3 of the ESX-3 secretion system in mycobacteria. RESULTS: Fluorescently tagged EccA3 localized to a single pole in the majority of Mycobacterium smegmatis cells and time-lapse fluorescent microscopy identified this pole as the growing pole. Deletion of ESX-3 did not prevent polar localization of fluorescently tagged EccA3, suggesting that EccA3 unipolar localization is independent of other ESX-3 components. Affinity purification - mass spectrometry was used to identify EccA3 associated proteins which may contribute to the localization of EccA3 at the growing pole. EccA3 co-purified with fatty acid metabolism proteins (FAS, FadA3, KasA and KasB), mycolic acid synthesis proteins (UmaA, CmaA1), cell division proteins (FtsE and FtsZ), and cell shape and cell cycle proteins (MurS, CwsA and Wag31). Secretion system related proteins Ffh, SecA1, EccA1, and EspI were also identified. CONCLUSIONS: Time-lapse microscopy demonstrated that EccA3 is located at the growing pole in M. smegmatis. The co-purification of EccA3 with proteins known to be required for polar growth, mycolic acid synthesis, the Sec secretion system (SecA1), and the signal recognition particle pathway (Ffh) also suggests that EccA3 is located at the site of active cell growth.

Identifying nucleic acid-associated proteins in Mycobacterium smegmatis by mass spectrometry-based proteomics.

BACKGROUND: Transcriptional responses required to maintain cellular homeostasis or to adapt to environmental stress, is in part mediated by several nucleic-acid associated proteins. In this study, we sought to establish an affinity purification-mass spectrometry (AP-MS) approach that would enable the collective identification of nucleic acid-associated proteins in mycobacteria. We hypothesized that targeting the RNA polymerase complex through affinity purification would allow for the identification of RNA- and DNA-associated proteins that not only maintain the bacterial chromosome but also enable transcription and translation. RESULTS: AP-MS analysis of the RNA polymerase ß-subunit cross-linked to nucleic acids identified 275 putative nucleic acid-associated proteins in the model organism Mycobacterium smegmatis under standard culturing conditions. The AP-MS approach successfully identified proteins that are known to make up the RNA polymerase complex, as well as several other known RNA polymerase complex-associated proteins such as a DNA polymerase, sigma factors, transcriptional regulators, and helicases. Gene ontology enrichment analysis of the identified proteins revealed that this approach selected for proteins with GO terms associated with nucleic acids and cellular metabolism. Importantly, we identified several proteins of unknown function not previously known to be associated with nucleic acids. Validation of several candidate nucleic acid-associated proteins demonstrated for the first time DNA association of ectopically expressed MSMEG_1060, MSMEG_2695 and MSMEG_4306 through affinity purification. CONCLUSIONS: Effective identification of nucleic acid-associated proteins, which make up the RNA polymerase complex as well as other DNA- and RNA-associated proteins, was facilitated by affinity purification of the RNA polymerase ß-subunit in M. smegmatis. The successful identification of several transcriptional regulators suggest that our approach could be sensitive enough to investigate the nucleic acid-associated proteins that maintain cellular functions and mediate transcriptional and translational change in response to environmental stress.

Moxifloxacin retains antimycobacterial activity in the presence of gyrA mutations.

Moxifloxacin-resistant Mycobacterium tuberculosis mutants were selected in vitro using different concentrations of moxifloxacin. gyrA mutations at codons 88 and 94 were associated with resistance (defined as an MIC of ≥2 µg/ml) (P < 0.0001 and P = 0.0053, respectively). Despite the presence of gyrA mutations, moxifloxacin significantly impedes bacterial growth, supporting its use for the treatment of ofloxacin-resistant M. tuberculosis.

Effect of household and community interventions on the burden of tuberculosis in southern Africa: the ZAMSTAR community-randomised trial.

BACKGROUND: Southern Africa has had an unprecedented increase in the burden of tuberculosis, driven by the HIV epidemic. The Zambia, South Africa Tuberculosis and AIDS Reduction (ZAMSTAR) trial examined two public health interventions that aimed to reduce the burden of tuberculosis by facilitating either rapid sputum diagnosis or integrating tuberculosis and HIV services within the community. METHODS: ZAMSTAR was a community-randomised trial done in Zambia and the Western Cape province of South Africa. Two interventions, community-level enhanced tuberculosis case-finding (ECF) and household level tuberculosis-HIV care, were implemented between Aug 1, 2006, and July 31, 2009, and assessed in a 2×2 factorial design between Jan 9, 2010, and Dec 6, 2010. All communities had a strengthened tuberculosis-HIV programme implemented in participating health-care centres. 24 communities, selected according to population size and tuberculosis notification rate, were randomly allocated to one of four study groups using a randomisation schedule stratified by country and baseline prevalence of tuberculous infection: group 1 strengthened tuberculosis-HIV programme at the clinic alone; group 2, clinic plus ECF; group 3, clinic plus household intervention; and group 4, clinic plus ECF and household interventions. The primary outcome was the prevalence of culture-confirmed pulmonary tuberculosis in adults (≥18 years), defined as Mycobacterium tuberculosis isolated from one respiratory sample, measured 4 years after the start of interventions in a survey of 4000 randomly selected adults in each community in 2010. The secondary outcome was the incidence of tuberculous infection, measured using tuberculin skin testing in a cohort of schoolchildren, a median of 4 years after a baseline survey done before the start of interventions. This trial is registered, number ISRCTN36729271. FINDINGS: Prevalence of tuberculosis was evaluated in 64,463 individuals randomly selected from the 24 communities; 894 individuals had active tuberculosis. Averaging over the 24 communities, the geometric mean of tuberculosis prevalence was 832 per 100,000 population. The adjusted prevalence ratio for the comparison of ECF versus non-ECF intervention groups was 1·09 (95% CI 0·86-1·40) and of household versus non-household intervention groups was 0·82 (0·64-1·04). The incidence of tuberculous infection was measured in a cohort of 8809 children, followed up for a median of 4 years; the adjusted rate ratio for ECF versus non-ECF groups was 1·36 (95% CI 0·59-3·14) and for household versus non-household groups was 0·45 (0·20-1·05). INTERPRETATION: Although neither intervention led to a statistically significant reduction in tuberculosis, two independent indicators of burden provide some evidence of a reduction in tuberculosis among communities receiving the household intervention. By contrast the ECF intervention had no effect on either outcome. FUNDING: Bill & Melinda Gates Foundation.

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

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

Detection of natural infection with Mycobacterium intracellulare in healthy wild-caught Chacma baboons (Papio ursinus) by ESAT-6 and CFP-10 IFN-gamma ELISPOT tests following a tuberculosis outbreak.

BACKGROUND: Both tuberculous and non-tuberculous mycobacteria can cause infection in nonhuman primates (NHP), indicating the existence of potential zoonotic transmission between these animals and visitors to zoos or animal handlers in primate facilities. Screening of mycobacterial infections in NHP is traditionally done by tuberculin skin test (TST), which is unable to distinguish between pathogenic and non-pathogenic mycobacterial infections. In this study, we investigated the use of ESAT-6 and CFP-10 for detection of mycobacterial infections in a wild-caught baboon colony after one baboon died of tuberculosis (TB). METHODS: Peripheral blood lymphocytes for interferon-gamma enzyme-linked immunospot assay (IFN-gamma ELISPOT) assay were obtained from TST positive baboons and those in contact with tuberculous baboons before being euthanased, autopsied and lung tissues taken for histology and mycobacterial culture. RESULTS: Both ESAT-6 and CFP-10 IFN-gamma ELISPOT assays were able to detect early M. tuberculosis but also M. intracellulare infection. Although this indicates potential cross-reactivity with M. intracellulare antigens, the method was able to distinguish M. bovis BCG vaccination from M. tuberculosis infection. This assay performed better than the TST, which failed to detect one M. tuberculosis and two early M. intracellulare infections. CONCLUSION: These results suggest that the IFN-gamma ELISPOT assay could improve the detection of M tuberculosis infections when screening NHP. There is some doubt, however, concerning specificity, as the assay scored positive three animals infected with M. intracellulare.

Pulmonary infection due to Mycobacterium goodii in a spotted hyena (Crocuta crocuta) from South Africa.

We report a case of pyogranulomatous pneumonia due to infection with Mycobacterium goodii in an adult female spotted hyena (Crocuta crocuta). The lungs of the animal showed consolidated, granulomatous lesions, and they were extensively and severely infiltrated. Polymerase chain reaction sequencing of isolated crude lung tissue DNA, and boiled lung culture samples, all confirmed that the causative organism was M. goodii, a recently described fast-growing organism closely related to the nonpathogenic mycobacterial species M. smegmatis. The current study illustrates that this organism can be pathogenic and cause extensive pulmonary disease.

Bovine tuberculosis in African buffaloes: observations regarding Mycobacterium bovis shedding into water and exposure to environmental mycobacteria.

BACKGROUND: African buffaloes are the maintenance host for Mycobacterium bovis in the endemically infected Kruger National Park (KNP). The infection is primarily spread between buffaloes via the respiratory route, but it is not known whether shedding of M. bovis in nasal and oral excretions may lead to contamination of ground and surface water and facilitate the transmission to other animal species. A study to investigate the possibility of water contamination with M. bovis was conducted in association with a BCG vaccination trial in African buffalo. Groups of vaccinated and nonvaccinated buffaloes were kept together with known infected in-contact buffalo cows to allow natural M. bovis transmission under semi-free ranging conditions. In the absence of horizontal transmission vaccinated and control buffaloes were experimentally challenged with M. bovis. Hence, all study buffaloes in the vaccination trial could be considered potential shedders and provided a suitable setting for investigating questions relating to the tenacity of M. bovis shed in water. RESULTS: Serial water samples were collected from the drinking troughs of the buffaloes once per season over an eleven-month period and cultured for presence of mycobacteria. All water samples were found to be negative for M. bovis, but 16 non-tuberculous Mycobacterium spp. isolates were cultured. The non-tuberculous Mycobacterium species were further characterised using 5'-16S rDNA PCR-sequencing, resulting in the identification of M. terrae, M. vaccae (or vanbaalenii), M. engbaekii, M. thermoresistibile as well as at least two species which have not yet been classified. CONCLUSION: The absence of detectable levels of Mycobacterium bovis in the trough water suggests that diseased buffalo do not commonly shed the organism in high quantities in nasal and oral discharges. Surface water may therefore not be likely to play an important role in the transmission of bovine tuberculosis from buffalo living in free-ranging ecosystems. The study buffalo were, however, frequently exposed to different species of non-tuberculous, environmental mycobacteria, with an unknown effect on the buffaloes' immune response to mycobacteria.

Tuberculosis due to resistant Haarlem strain, Tunisia.

Multidrug-resistant tuberculosis was diagnosed in 21 HIV-negative, nonhospitalized male patients residing in northern Tunisia. A detailed investigation showed accelerated transmission of a Mycobacterium tuberculosis clone of the Haarlem type in 90% of all patients. This finding highlights the epidemic potential of this prevalent genotype.

Reinfection and mixed infection cause changing Mycobacterium tuberculosis drug-resistance patterns.

RATIONALE: Multiple infections with different strains of Mycobacterium tuberculosis may occur in settings where the infection pressure is high. The relevance of mixed infections for the patient, clinician, and control program remains unclear. OBJECTIVES: This study aimed to describe reinfection and mixed infection as underlying mechanisms of changing drug-susceptibility patterns in serial sputum cultures. METHODS: Serial M. tuberculosis sputum cultures from patients diagnosed with multi-drug-resistant (MDR) tuberculosis were evaluated by phenotypic drug-susceptibility testing and mutation detection methods. Genotypic analysis was done by IS6110 DNA fingerprinting and a novel strain-specific polymerase chain reaction amplification method. MEASUREMENTS AND MAIN RESULTS: DNA fingerprinting analysis of serial sputum cultures from 48 patients with MDR tuberculosis attributed 10 cases to reinfection and 1 case to mixed infection. In contrast, strain-specific polymerase chain reaction amplification analysis in 9 of the 11 cases demonstrated mixed infection in 5 cases, reinfection in 3 cases, and laboratory contamination in 1 case. Analysis of clinical data suggests that first-line therapy can select for a resistant subpopulation, whereas poor adherence or second-line therapy resulted in the reemergence of the drug-susceptible subpopulations. CONCLUSIONS: We have shown that, in some patients with MDR tuberculosis, mixed infection may be responsible for observations attributed to reinfection by DNA fingerprinting. We conclude that treatment and adherence determines which strain is dominant. We hypothesize that treatment with second-line drugs may lead to reemergence of the drug-susceptible strain in patients with mixed infection.

Mycosin-1, a subtilisin-like serine protease of Mycobacterium tuberculosis, is cell wall-associated and expressed during infection of macrophages.

BACKGROUND: Exported proteases are commonly associated with virulence in bacterial pathogens, yet there is a paucity of information regarding their role in Mycobacterium tuberculosis. There are five genes (mycP1-5) present within the genome of Mycobacterium tuberculosis H37Rv that encode a family of secreted, subtilisin-like serine proteases (the mycosins). The gene mycP1 (encoding mycosin-1) was found to be situated 3700 bp (four ORF's) from the RD1 deletion region in the genome of the attenuated vaccine strain M. bovis BCG (bacille de Calmette et Guérin) and was selected for further analyses due to the absence of expression in this organism. RESULTS: Full-length, 50 kDa mycosin-1 was observed in M. tuberculosis cellular lysates, whereas lower-molecular-weight species were detected in culture filtrates. A similar lower-molecular-weight species was also observed during growth in macrophages. Mycosin-1 was localized to the membrane and cell wall fractions in M. tuberculosis by Western blotting, and to the cell envelope by electron microscopy. Furthermore, M. tuberculosis culture filtrates were shown to contain a proteolytic activity inhibited by mixed serine/cysteine protease inhibitors and activated by Ca2+, features typical of the subtilisins. CONCLUSIONS: Mycosin-1 is an extracellular protein that is membrane- and cell wall-associated, and is shed into the culture supernatant. The protein is expressed after infection of macrophages and is subjected to proteolytic processing. Although proteolytically active mycosin-1 could not be generated recombinantly, serine protease activity containing features typical of the subtilisins was detected in M. tuberculosis culture filtrates.