Surviving within the amoebal exocyst: the Mycobacterium avium complex paradigm

<p>Abstract</p> <p>Background</p> <p>Most of environmental mycobacteria have been previously demonstrated to resist free-living amoeba with subsequent increased virulence and resistance to antibiotics and biocides. The <it>Mycobacterium avium </it>complex (MAC) comprises of environmental organisms that inhabit a wide variety of ecological niches and exhibit a significant degree of genetic variability. We herein studied the intra-ameobal location of all members of the MAC as model organisms for environmental mycobacteria.</p> <p>Results</p> <p>Type strains for <it>M. avium</it>, <it>Mycobacterium intracellulare</it>, <it>Mycobacterium chimaera</it>, <it>Mycobacterium colombiense</it>, <it>Mycobacterium arosiense</it>, <it>Mycobacterium marseillense</it>, <it>Mycobacterium timonense </it>and <it>Mycobacterium bouchedurhonense </it>were co-cultivated with the free-living amoeba <it>Acanthamoeba polyphaga </it>strain Linc-AP1. Microscopic analyses demonstrated the engulfment and replication of mycobacteria into vacuoles of <it>A. polyphaga </it>trophozoites. Mycobacteria were further entrapped within amoebal cysts, and survived encystment as demonstrated by subculturing. Electron microscopy observations show that, three days after entrapment into <it>A. polyphaga </it>cysts, all MAC members typically resided within the exocyst.</p> <p>Conclusions</p> <p>Combined with published data, these observations indicate that mycobacteria are unique among amoeba-resistant bacteria, in residing within the exocyst.</p

Mycobacterium tuberculosis Complex Mycobacteria as Amoeba-Resistant Organisms

International audienceBackground: Most environmental non-tuberculous mycobacteria have been demonstrated to invade amoebal trophozoites and cysts, but such relationships are largely unknown for members of the Mycobacterium tuberculosis complex. An environmental source has been proposed for the animal Mycobacterium bovis and the human Mycobacterium canettii.Methodology/Principal Findings: Using optic and electron microscopy and co-culture methods, we observed that 89±0.6% of M. canettii, 12.4±0.3% of M. tuberculosis, 11.7±2% of M. bovis and 11.2±0.5% of Mycobacterium avium control organisms were phagocytized by Acanthamoeba polyphaga, a ratio significantly higher for M. canettii (P = 0.03), correlating with the significantly larger size of M. canetti organisms (P = 0.035). The percentage of intraamoebal mycobacteria surviving into cytoplasmic vacuoles was 32±2% for M. canettii, 26±1% for M. tuberculosis, 28±2% for M. bovis and 36±2% for M. avium (P = 0.57). M. tuberculosis, M. bovis and M. avium mycobacteria were further entrapped within the double wall of <1% amoebal cysts, but no M. canettii organisms were observed in amoebal cysts. The number of intracystic mycobacteria was significantly (P = 10−6) higher for M. avium than for the M. tuberculosis complex, and sub-culturing intracystic mycobacteria yielded significantly more (P = 0.02) M. avium organisms (34×104 CFU/mL) than M. tuberculosis (42×101 CFU/mL) and M. bovis (35×101 CFU/mL) in the presence of a washing fluid free of mycobacteria. Mycobacteria survived in the cysts for up to 18 days and cysts protected M. tuberculosis organisms against mycobactericidal 5 mg/mL streptomycin and 2.5% glutaraldehyde.Conclusions/Significance: These data indicate that M. tuberculosis complex organisms are amoeba-resistant organisms, as previously demonstrated for non-tuberculous, environmental mycobacteria. Intercystic survival of tuberculous mycobacteria, except for M. canettii, protect them against biocides and could play a role in their life cycle

Les mycobactéries du complexe Mycobacterium avium (identification et interactions avec les amibes libres)

AIX-MARSEILLE2-BU Méd/Odontol. (130552103) / SudocSudocFranceF

Effects of two fibers used separately and in combination on physico-chemical, textural, nutritional and sensory properties of beef fresh sausage

[Purpose]: The purpose of this paper is to investigate the influence of different dietary fibers on color, nutritional, physico-chemical, sensory and textural properties of fresh sausage.[Design/methodology/approach]: This study was undertaken to determine the effects of partial beef meat substitution (15, 10.5 and 6 percent) at different combinations: barley beta-glucan concentrate (BBC at 1 percent) alone, carrot fiber (ID809 at 1 percent) alone and a mixture of both fibers (BBC and ID809 at 0.5 percent of each), on the quality of fresh sausage.[Findings]: Results revealed that the supplementation of dietary fibers generally decreased protein contents and increased moisture. Color parameters were significantly affected by the addition of dietary fibers. Meat substitution with dietary fibers tended toward red coloration, which enhanced sensory properties of fresh sausages, especially general acceptability. Fresh sausages formulated with a mixture of dietary fibers recorded good firmness. Indeed, it increased extrusion force values and provided a greater hardness at sensory level. This manuscript reports that beef sausage formulated with a mixture of BBC and ID809 and reduced beef meat rate improved acceptability to consumer.[Originality/value]: The paper approaches a new subject that may be relevant to functional food. There are few research works to evaluate consumer preferences of new product developments and to achieve healthier and more economic fresh sausages formulated with a mixture of two fibers after reducing beef meat content.This research was financially supported by the Tunisian Ministry of Higher Education, Scientific Research and Information and Communication Technology.Peer reviewe

Effects of probiotic strains, Lactobacillus plantarum TN8 and Pediococcus acidilactici, on microbiological and physico-chemical characteristics of beef sausages

This study was undertaken to evaluate the effects of a combination of probiotic strains namely, Lactobacillus plantarum TN8 and Pediococcus acidilactici MA 18/5M and dietary fiber on microbiological and physico-chemical characteristics of sausages stored at 4 °C up to 12 days. L. plantarum TN8 might be a potential food additive in the meat industry as a probiotic agent. Microbial counts revealed a decrease in Enterobacteriaceae of inoculated sausages, which reached values below 2 log CFU/g in the stored product. Reformulated sausages recorded good textural attributes and improved sensory features. At the end of storage period, sausages with different probiotic strains decreased the b* color parameter and cooking loss when compared with control samples. Sensorial and color parameters could be used for constructing regression models to predict overall acceptability. On the other hand, the free fatty acid profile was significantly affected by probiotic strains. Overall, the inclusion of two probiotic strains and fiber improved the hygienic quality and sensorial features of sausages.This research was funded by the Tunisian Ministry of Higher Education and Scientific Research (LRCBS05), and by a bilateral project between Tunisia and Morocco (17TM06).Peer Reviewe

Effect of partial replacement of nitrite with a novel probiotic Lactobacillus plantarum TN8 on color, physico-chemical, texture and microbiological properties of beef sausages

This work investigates the effects of partial nitrite substitution by the probiotic Lactobacillus plantarum TN8, on the quality and safety of beef sausages during 10 days of storage at 4 °C. The obtained results revealed that the texture was affected in terms of a reduction of hardness, springiness and chewiness. Color ratio a*/b* was also significantly affected (P 0.05) were observed while a significant decrease in pH values in sausage formulated with TN8 strain were reported due to the growth of lactic acid bacteria. Finally, our study demonstrated that TN8 strain addition at 7 log CFU/g can be used as a biopreservative for beef sausage by decreasing the growth of Salmonella enterica and Listeria monocytogenes and maintaining lipid oxidation. Overall, our findings demonstrated that the incorporation of TN8 strain into beef sausage formulation could be an interesting strategy to produce healthier sausage by lowering nitrite levels.This research was financially supported by the Tunisian Ministry of Higher Education and Scientific Research (LRCBS05).Peer Reviewe