Interaction between lactic acid bacteria and Mycobacterium bovis in Ethiopian fermented milk: insight into the fate of M. bovis

Zoonotic tuberculosis in a high bovine tuberculosis burden area of Ethiopia

Background

Tuberculosis (TB) is a major cause of ill health and one of the leading causes of death worldwide, caused by species of the Mycobacterium tuberculosis complex (MTBC), with Mycobacterium tuberculosis being the dominant pathogen in humans and Mycobacterium bovis in cattle. Zoonotic transmission of TB (zTB) to humans is frequent particularly where TB prevalence is high in cattle. In this study, we explored the prevalence of zTB in central Ethiopia, an area highly affected by bovine TB (bTB) in cattle.

Method

A convenient sample of 385 patients with pulmonary tuberculosis (PTB, N = 287) and tuberculous lymphadenitis (TBLN, N = 98) were included in this cross-sectional study in central Ethiopia. Sputum and fine needle aspirate (FNA) samples were obtained from patients with PTB and TBLN, respectively, and cultures were performed using BACTEC™ MGIT™ 960. All culture positive samples were subjected to quantitative PCR (qPCR) assays, targeting IS1081, RD9 and RD4 genomic regions for detection of MTBC, M. tuberculosis and M. bovis, respectively.

Results

Two hundred and fifty-five out of 385 sampled patients were culture positive and all were isolates identified as MTBC by being positive for the IS1081 assay. Among them, 249 (97.6%) samples had also a positive RD9 result (intact RD9 locus) and were consequently classified as M. tuberculosis. The remaining six (2.4%) isolates were RD4 deficient and thereby classified as M. bovis. Five out of these six M. bovis strains originated from PTB patients whereas one was isolated from a TBLN patient. Occupational risk and the widespread consumption of raw animal products were identified as potential sources of M. bovis infection in humans, and the isolation of M. bovis from PTB patients suggests the possibility of human-to-human transmission, particularly in patients with no known contact history with animals.

Conclusion

The detected proportion of culture positive cases of 2.4% being M. bovis from this region was higher zTB rate than previously reported for the general population of Ethiopia. Patients with M. bovis infection are more likely to get less efficient TB treatment because M. bovis is inherently resistant to pyrazinamide. MTBC species identification should be performed where M. bovis is common in cattle, especially in patients who have a history of recurrence or treatment failure.

Acceptability and feasibility of proposed control and prevention strategies for bovine tuberculosis among Ethiopian dairy farmers and associated professionals

A series of Focus Group Discussions were held with farmers, veterinarians and human health workers in two sites in Ethiopia, as part of the Ethiopia Control of Bovine Tuberculosis Strategies Project's efforts to devise and test the acceptability and feasibility of various control strategies for Bovine Tuberculosis (bTB). Group members were asked to give their responses to a range of strategies collected from global efforts to control the disease in cattle and humans in the context of intensification of the dairy industry, as well as those suggested by researchers within the project. Key findings from the study include the observation that a number of strategies utilised routinely to control bTB elsewhere in the world, including 'Test and Slaughter' and 'Test and Segregation' are likely to be impractical in low-resource settings where infrastructure may be unreliable and space both between and on individual farms is limited. It also became clear that farmers called upon to implement biosecurity measures should be supplied with locally-specific information and instructions in order to effectively control and prevent the spread of disease. Additionally, this research supports the need for investment in animal health system strengthening in Ethiopia and other similar settings, in order to enable animal health workers, including veterinarians, to devote time to disease surveillance and farmer sensitisation. Similarly, investment in milk pasteurisation processes and public education on these processes should be prioritised in order to increase their acceptability and feasibility among both producers and consumers.

Effects of different probiotic combinations on the components and bioactivity of Spirulina

Spirulina acts as a good dietary nutritional supplement. However, few research studies have been conducted on its fermentation. Three groups of probiotic combinations, lactic acid bacteria, Bacillus strains, and their mixture, were used to investigate Spirulina fermentation. The results showed that lactic acid bacteria significantly increased the content of amino acids and the ratio of essential amino acids to total amino acids in the fermented Spirulina, compared with the unfermented Spirulina, and this trend was enhanced by the strains' mixture. However, compared to unfermented Spirulina, the amino acid levels were significantly decreased after fermentation with Bacillus strains and so was the total free amino acid and essential amino acid content. Fermentation significantly reduced the contents of the offensive components of Spirulina, with significant differences among the three mixed bacterial treatments. Moreover, Bacillus strain fermentation increased the contents of flavonoids and polyphenols compared to the unfermented Spirulina, and significantly enhanced 1,1-diphenyl-2-trinitrophenylhydrazine free-radical scavenging ability and total antioxidant ability. On the contrary, treatments with lactic acid bacteria and the mixture of lactic acid bacteria and Bacillus strains endowed the fermented supernatants with good antibacterial ability. The results showed that probiotic fermentation has a good effect on Spirulina and can serve as a new procedure for developing new Spirulina-containing food items.

Lactobacilli Isolated From Wild Boar (Sus scrofa) Antagonize Mycobacterium bovis Bacille Calmette-Guerin (BCG) in a Species-Dependent Manner

Background: Wildlife poses a significant burden for the complete eradication of bovine tuberculosis (bTB). In particular, wild boar (Sus scrofa) is one of the most important reservoirs of Mycobacterium bovis, the causal agent of bTB. Wild boar can display from mild TB lesions, usually found in head lymph nodes, to generalized TB lesions distributed in different anatomical regions; but rarely clinical signs, which complicates the diagnosis of Mycobacterium bovis infection and bTB control. Among the possibilities for this variability in lesion distribution is the influence of the host-beneficial commensal-primed immune barrier. In this respect, beneficial microbes may delay bTB dissemination as a consequence of an antagonistic competition for nutrients and phagocytes. In order to explore this possibility, we have tested whether typical commensals such as lactobacilli have the capacity to reduce the survival rate of the surrogate M. bovis strain Bacillus Calmette-Guerin (BCG); and to modulate its phagocyte intake.

Results: Three Lactobacillus species, L. casei, L. plantarum, and L. salivarius, isolated from wild boar feces displayed a pH-dependent inhibitory activity against BCG and influenced its intake by porcine blood phagocytes in a species-dependent manner. All lactobacilli showed a very significant bactericidal effect against BCG at low pH, but only isolates of L. plantarum and L. casei displayed such antimycobacterial activity at neutral pH. The genomes of these isolates revealed the presence of two-peptide bacteriocins whose precursor genes up-regulate in the presence of BCG cells. Furthermore, L. plantarum reduced significantly the BCG phagocytic intake, whereas L. casei had the opposite effect. L. salivarius had no significant influence on the phagocytic response to BCG.

Conclusions: Our in vitro results show that lactobacilli isolated from wild boar antagonize BCG as a consequence of their antimycobacterial activity and a competitive phagocytic response. These findings suggest that commensal bacteria could play a beneficial role in influencing the outcome of bTB dissemination. Further work with lactobacilli as a potential competitive pressure to control bTB will need to take into account the complex nature of the commensal microbiome, the specific immunity of the wild boar and the in vivo infection context with pathogenic strains of M. bovis.

Survival of Mycobacterium avium subsp. paratuberculosis in raw fermented sausages during production and storage

Mycobacterium avium subsp. paratuberculosis (MAP), the etiological agent of paratuberculosis, is considered to be a potential zoonotic pathogen and meat is one of the sources of MAP exposure for humans. MAP has been shown to be relatively resistant to different food processing methods, but there is a lack of information about the effects of ripening and fermentation processes on MAP survival in meat. Our results demonstrate that a short ripening process during teewurst production did not reduce MAP counts and viable mycobacteria were detected even during 4 weeks of storage. Although no viable MAP was recovered during the dry fermented sausage production process, there was no reduction in MAP count detected by real time PCR during production and storage of both sausages. Although the impact of foodborne exposure to viable MAP and/or mycobacterial components has not yet been clearly determined, the consumption of raw fermented meat products may be considered as a possible route of MAP transmission to humans.

Lactic acid Bacteria isolated from European badgers (Meles meles) reduce the viability and survival of Bacillus Calmette-Guerin (BCG) vaccine and influence the immune response to BCG in a human macrophage model

Background

Bovine tuberculosis (bTB) caused by Mycobacterium bovis is the most serious endemic disease affecting livestock in the UK. The European badger (Meles meles) is the most important wildlife reservoir of bTB transmission to cattle, making eradication particularly difficult. In this respect, oral vaccination with the attenuated M. bovis vaccine Bacillus Calmette-Guerin (BCG) has been suggested as a wide-scale intervention to reduce bTB infection in badgers. However, experimental studies show variable protection. Among the possibilities for this variation is that the resident gut bacteria may influence the success of oral vaccination in badgers; either through competitive exclusion and/or inhibition, or via effects on the host immune system. In order to explore this possibility, we have tested whether typical gut commensals such as Lactic Acid Bacteria (LAB) have the capacity to impact on the viability and survival rate of BCG and to modulate the immune response to BCG using an in vitro model.

Results

Twelve LAB isolated from badger faeces displayed inhibitory activity to BCG that was species-dependent. Weissella had a bacteriostatic effect, whereas isolates of enterococci, lactobacilli and pediococci had a more bactericidal activity. Furthermore, BCG-induced activation of the pro-inflammatory transcription factor NF-κB in human THP-1 macrophages was modulated by LAB in a strain-dependent manner. Most pediococci enhanced NF-κB activation but one strain had the opposite effect. Interestingly, isolates of enterococci, lactobacilli and weissella had different effects as immunomodulators of BCG-induced macrophage responses as some had no significant influence on NF-κB activation, but others increased it significantly.

Conclusions

Our in vitro results show that LAB isolated from badgers exhibit significant inhibitory activity against BCG and influence the immune activation mediated by BCG in a human macrophage assay. These findings suggest that gut commensal bacteria could play a role in influencing the outcome of oral BCG vaccination. Inactivated cells of LAB, or LAB that are bacteriostatic but have a synergistic immunostimulatory effect with BCG, could be potential adjuvants to be used for oral vaccination in badgers. Further work is needed to take into account the complex nature of the gut microbiome, specific immunity of the badger and the in vivo context.

Electronic supplementary material

The online version of this article (10.1186/s12866-018-1210-z) contains supplementary material, which is available to authorized users.

Genomic characterization of Mycobacterium tuberculosis lineage 7 and a proposed name: 'Aethiops vetus'

Lineage 7 of the Mycobacterium tuberculosis complex has recently been identified among strains originating from Ethiopia. Using different DNA typing techniques, this study provides additional information on the genetic heterogeneity of five lineage 7 strains collected in the Amhara Region of Ethiopia. It also confirms the phylogenetic positioning of these strains between the ancient lineage 1 and TbD1-deleted, modern lineages 2, 3 and 4 of Mycobacterium tuberculosis. Four newly identified large sequence polymorphisms characteristic of the Amhara Region lineage 7 strains are described. While lineage 7 strains have been previously identified in the Woldiya area, we show that lineage 7 strains circulate in other parts of the Amhara Region and also among foreign-born individuals from Eritrea and Somalia in The Netherlands. For ease of documenting future identification of these strains in other geographical locations and recognizing the place of origin, we propose to assign lineage 7 strains the lineage name 'Aethiops vetus'.

Knowledge of Bovine Tuberculosis, Cattle Husbandry and Dairy Practices amongst Pastoralists and Small-Scale Dairy Farmers in Cameroon

BACKGROUND

Control of bovine tuberculosis (bTB) and zoonotic tuberculosis (zTB) has relied upon surveillance and slaughter of infected cattle, milk pasteurisation and public health education. In Cameroon, like many other sub-Saharan African countries, there is limited understanding of current cattle husbandry or milk processing practices or livestock keepers awareness of bTB. This paper describes husbandry and milk processing practices within different Cameroonian cattle keeping communities and bTB awareness in comparison to other infectious diseases.

STUDY DESIGN

A population based cross-sectional sample of herdsmen and a questionnaire were used to gather data from pastoralists and dairy farmers in the North West Region and Vina Division of Cameroon.

RESULTS

Pastoralists were predominately male Fulanis who had kept cattle for over a decade. Dairy farmers were non-Fulani and nearly half were female. Pastoralists went on transhumance with their cattle and came into contact with other herds and potential wildlife reservoirs of bTB. Dairy farmers housed their cattle and had little contact with other herds or wildlife. Pastoralists were aware of bTB and other infectious diseases such as foot-and-mouth disease and fasciolosis. These pastoralists were also able to identify clinical signs of these diseases. A similar proportion of dairy farmers were aware of bTB but fewer were aware of foot-and-mouth and fasciolosis. In general, dairy farmers were unable to identify any clinical signs for any of these diseases. Importantly most pastoralists and dairy farmers were unaware that bTB could be transmitted to people by consuming milk.

CONCLUSIONS

Current cattle husbandry practices make the control of bTB in cattle challenging especially in mobile pastoralist herds. Routine test and slaughter control in dairy herds would be tractable but would have profound impact on dairy farmer livelihoods. Prevention of transmission in milk offers the best approach for human risk mitigation in Cameroon but requires strategies that improved risk awareness amongst producers and consumers.

Effect of milk fermentation by kefir grains and selected single strains of lactic acid bacteria on the survival of Mycobacterium bovis BCG

Mycobacterium bovis that causes Bovine tuberculosis (BTB) can be transmitted to humans thought consumption of raw and raw fermented milk products from diseased animals. Lactic acid bacteria (LAB) used in popular traditional milk products in Africa produce anti-microbial compounds that inhibit some pathogenic and spoilage bacteria. M. bovis BCG is an attenuated non-pathogenic vaccine strain of M. bovis and the aim of the study was to determine the effect of the fermentation process on the survival of M. bovis BCG in milk. M. bovis BCG at concentrations of 6 log CFU/ml was added to products of kefir fermentation. The survival of M. bovis BCG was monitored at 12-h intervals for 72 h by enumerating viable cells on Middlebrook 7H10 agar plates enriched with 2% BD BACTEC PANTA™. M. bovis BCG was increasingly reduced in sterile kefir that was fermented for a period of 24h and longer. In the milk fermented with kefir grains, Lactobacillus paracasei subsp. paracasei or Lactobacillus casei, the viability of M. bovis BCG was reduced by 0.4 logs after 24h and by 2 logs after 48 h of fermentation. No viable M. bovis BCG was detected after 60 h of fermentation. Results from this study show that long term fermentation under certain conditions may have the potential to inactivate M. bovis BCG present in the milk. However, to ensure safety of fermented milk in Africa, fermentation should be combined with other hurdle technologies such as boiling and milk pasteurisation.

Identification and survival studies of Mycobacterium tuberculosis within Laboratory-Fermented bovine milk

Background

Mycobacterium tuberculosis and Mycobacterium bovis are the classic agents causing tuberculosis (TB) in humans and animals respectively. Transmission of tuberculous bacteria to humans usually occurs by inhalation of aerosols containing droplets of tubercle bacilli or via consumption of contaminated foods and drinks, primarily milk. The practice of milk pooling, including from cows with TB of the udder, further exacerbates the situation by rendering the whole milk supply infective. The simultaneous presence of indigenous lactic acid bacteria (LAB) in Mycobacterium-contaminated milk is believed to confer protective effect when the milk is adequately fermented. This study assessed the effect of LAB on the viability of mycobacteria in inherently contaminated pool of raw milk during fermentation as a function of time.

Findings

Growth was obtained in the pooled raw milk culture, and identified to be M. tuberculosis. This M. tuberculosis growth was undetectable in the milk culture by day 7 as assessed by plating serial dilutions of the milk culture for up to 14 days.

Conclusions

Some LAB species appear to show inhibitory effect on tubercle bacilli. If proven by more rigorous, controlled experimental results regarding such effect, selected LAB (with proven safety and efficacy) may have potential applications as anti-mycobacterial agents.

Bovine tuberculosis and brucellosis prevalence in cattle from selected milk cooperatives in Arsi zone, Oromia region, Ethiopia

Background

Bovine tuberculosis (BTB) and bovine brucellosis are two important milk-borne zoonoses that have been shown to be prevalent to various degrees in Ethiopian cattle.

The study was carried out in four Woredas (districts) around Asella town, Arsi Zone between October 2011 and March 2012 and included 318 small-holders in 13 dairy cooperatives that marketed the delivered milk. The aims of the study were i) to assess the prevalence of the two diseases in cattle in a cross-sectional study, ii) to assess potential risk factors of BTB and brucellosis to humans as well as the knowledge-attitude-practice (KAP) among these farmers towards these diseases.

Results

BTB testing using the comparative intradermal skin test (CIDT) was done on 584 milking cows, out of which 417 were serologically tested for brucellosis using the Rose Bengal Plate Test and reactors confirmed with an indirect ELISA test (PrioCHECK®). The individual animal prevalence was 0.3% (95% CI 0.1% to 1.3%) for BTB, 1.7% (95% CI 0.8% to 3.5%) for brucellosis and 8.9% (95% CI 6.8% to 11.5%) for MAC (Mycobacterium avium complex). Of the 13 milk cooperatives, two had at least one positive BTB reactor and five had animals positive for brucellosis.

Cross-breeds accounted for 100% and 71.4% of the BTB and brucellosis reactors respectively. For both diseases, there were prevalence variations depending on Woreda. No animal was concomitant reactor for BTB and brucellosis.

Raw milk was consumed by 55.4% of the respondents. 79.2% of the respondents reported touching the afterbirth with bare hands. The latter was fed to dogs in 83% of the households. One cow among the herds of the 130 interviewees had aborted in the last 12 months. Among the interviewees, 77% stated knowing tuberculosis in general but 42 out of the 130 respondents (32.3%) did not know that BTB was transmitted by livestock. Less than half (47.7%) of the respondents knew about brucellosis.

Conclusions

Low prevalence of both diseases reflected the potential for the area to compete with the growing milk demand. The authors discussed the possible control strategies for the area.