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Contrasting results of culture-dependent and molecular analyses of Mycobacterium avium subsp. paratuberculosis from wood bison.

ABSTRACT: Reduced to near extinction in the late 1800s, a number of wood bison populations (Bison bison athabascae) have been re-established through reintroduction initiatives. Although an invaluable tool for conservation, translocation of animals can spread infectious agents to new areas or expose animals to pathogens in their new environment. Mycobacterium avium subsp. paratuberculosis, a bacterium that causes chronic enteritis in ruminants, is among the pathogens of potential concern for wood bison management and conservation. In order to inform translocation decisions, our objectives were to determine the M. avium subsp. paratuberculosis infection status of wood bison herds in Canada and to culture and genetically characterize the infective strain(s). We tested fecal samples from bison (n = 267) in nine herds using direct PCR for three M. avium subsp. paratuberculosis-specific genetic targets with different copy numbers within the M. avium subsp. paratuberculosis genome. Restriction enzyme analysis (REA) and sequencing of IS1311 were performed on seven samples from five different herds. We also evaluated a panel of different culture conditions for their ability to support M. avium subsp. paratuberculosis growth from feces and tissues of direct-PCR-positive animals. Eighty-one fecal samples (30%) tested positive using direct IS900 PCR, with positive samples from all nine herds; of these, 75% and 21% were also positive using ISMAP02 and F57, respectively. None of the culture conditions supported the growth of M. avium subsp. paratuberculosis from PCR-positive samples. IS1311 REA and sequencing indicate that at least two different M. avium subsp. paratuberculosis strain types exist in Canadian wood bison. The presence of different M. avium subsp. paratuberculosis strains among wood bison herds should be considered in the planning of translocations.

SUBMITTER: Forde T

PROVIDER: S-EPMC3697503 | biostudies-literature | 2013 Jul

REPOSITORIES: biostudies-literature

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Contrasting results of culture-dependent and molecular analyses of Mycobacterium avium subsp. paratuberculosis from wood bison.

Forde Taya T De Buck Jeroen J Elkin Brett B Kutz Susan S van der Meer Frank F Orsel Karin K

Applied and environmental microbiology 20130517 14

Reduced to near extinction in the late 1800s, a number of wood bison populations (Bison bison athabascae) have been re-established through reintroduction initiatives. Although an invaluable tool for conservation, translocation of animals can spread infectious agents to new areas or expose animals to pathogens in their new environment. Mycobacterium avium subsp. paratuberculosis, a bacterium that causes chronic enteritis in ruminants, is among the pathogens of potential concern for wood bison man ...[more]

PMID: 23686265

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Project description:Mycobacterium avium subsp. paratuberculosis is a host-adapted pathogen that evolved from the environmental bacterium M. avium subsp. hominissuis through gene loss and gene acquisition. Growth of M. avium subsp. paratuberculosis in the laboratory is enhanced by supplementation of the media with the iron-binding siderophore mycobactin J. Here we examined the production of mycobactins by related organisms and searched for an alternative iron uptake system in M. avium subsp. paratuberculosis. Through thin-layer chromatography and radiolabeled iron-uptake studies, we showed that M. avium subsp. paratuberculosis is impaired for both mycobactin synthesis and iron acquisition. Consistent with these observations, we identified several mutations, including deletions, in M. avium subsp. paratuberculosis genes coding for mycobactin synthesis. Using a transposon-mediated mutagenesis screen conditional on growth without myobactin, we identified a potential mycobactin-independent iron uptake system on a M. avium subsp. paratuberculosis-specific genomic island, LSP(P)15. We obtained a transposon (Tn) mutant with a disruption in the LSP(P)15 gene MAP3776c for targeted study. The mutant manifests increased iron uptake as well as intracellular iron content, with genes downstream of the transposon insertion (MAP3775c to MAP3772c [MAP3775-2c]) upregulated as the result of a polar effect. As an independent confirmation, we observed the same iron uptake phenotypes by overexpressing MAP3775-2c in wild-type M. avium subsp. paratuberculosis. These data indicate that the horizontally acquired LSP(P)15 genes contribute to iron acquisition by M. avium subsp. paratuberculosis, potentially allowing the subsequent loss of siderophore production by this pathogen.Many microbes are able to scavenge iron from their surroundings by producing iron-chelating siderophores. One exception is Mycobacterium avium subsp. paratuberculosis, a fastidious, slow-growing animal pathogen whose growth needs to be supported by exogenous mycobacterial siderophore (mycobactin) in the laboratory. Data presented here demonstrate that, compared to other closely related M. avium subspecies, mycobactin production and iron uptake are different in M. avium subsp. paratuberculosis, and these phenotypes may be caused by numerous deletions in its mycobactin biosynthesis pathway. Using a genomic approach, supplemented by targeted genetic and biochemical studies, we identified that LSP(P)15, a horizontally acquired genomic island, may encode an alternative iron uptake system. These findings shed light on the potential physiological consequence of horizontal gene transfer in M. avium subsp. paratuberculosis evolution.

Project description:The genetic similarity between Mycobacterium avium subsp. paratuberculosis and other mycobacterial species has confounded the development of M. avium subsp. paratuberculosis-specific diagnostic reagents. Random shotgun sequencing of the M. avium subsp. paratuberculosis genome in our laboratories has shown >98% sequence identity with Mycobacterium avium subsp. avium in some regions. However, an in silico comparison of the largest annotated M. avium subsp. paratuberculosis contigs, totaling 2,658,271 bp, with the unfinished M. avium subsp. avium genome has revealed 27 predicted M. avium subsp. paratuberculosis coding sequences that do not align with M. avium subsp. avium sequences. BLASTP analysis of the 27 predicted coding sequences (genes) shows that 24 do not match sequences in public sequence databases, such as GenBank. These novel sequences were examined by PCR amplification with genomic DNA from eight mycobacterial species and ten independent isolates of M. avium subsp. paratuberculosis. From these analyses, 21 genes were found to be present in all M. avium subsp. paratuberculosis isolates and absent from all other mycobacterial species tested. One region of the M. avium subsp. paratuberculosis genome contains a cluster of eight genes, arranged in tandem, that is absent in other mycobacterial species. This region spans 4.4 kb and is separated from other predicted coding regions by 1,408 bp upstream and 1,092 bp downstream. The gene upstream of this eight-gene cluster has strong similarity to mycobacteriophage integrase sequences. The GC content of this 4.4-kb region is 66%, which is similar to the rest of the genome, indicating that this region was not horizontally acquired recently. Southern hybridization analysis confirmed that this gene cluster is present only in M. avium subsp. paratuberculosis. Collectively, these studies suggest that a genomics approach will help in identifying novel M. avium subsp. paratuberculosis genes as candidate diagnostic sequences.

Project description:BackgroundMycobacterium avium subspecies avium (M. avium) is frequently encountered in the environment, but also causes infections in animals and immunocompromised patients. In contrast, Mycobacterium avium subspecies paratuberculosis (M. paratuberculosis) is a slow-growing organism that is the causative agent of Johne's disease in cattle and chronic granulomatous infections in a variety of other ruminant hosts. Yet we show that despite their divergent phenotypes and the diseases they present, the genomes of M. avium and M. paratuberculosis share greater than 97% nucleotide identity over large (25 kb) genomic regions analyzed in this study.ResultsTo characterize genome similarity between these two subspecies as well as attempt to understand their different growth rates, we designed oligonucleotide primers from M. avium sequence to amplify 15 minimally overlapping fragments of M. paratuberculosis genomic DNA encompassing the chromosomal origin of replication. These strategies resulted in the successful amplification and sequencing of a contiguous 11-kb fragment containing the putative Mycobacterium paratuberculosis origin of replication (oriC). This fragment contained 11 predicted open reading frames that showed a conserved gene order in the oriC locus when compared with several other Gram-positive bacteria. In addition, a GC skew analysis identified the origin of chromosomal replication which lies between the genes dnaA and dnaN. The presence of multiple DnaA boxes and the ATP-binding site in dnaA were also found in M. paratuberculosis. The strong nucleotide identity of M. avium and M. paratuberculosis in the region surrounding the origin of chromosomal replication led us to compare other areas of these genomes. A DNA homology matrix of 2 million nucleotides from each genome revealed strong synteny with only a few sequences present in one genome but absent in the other. Finally, the 16s rRNA gene from these two subspecies is 100% identical.ConclusionsWe present for the first time, a description of the oriC region in M. paratuberculosis. In addition, genomic comparisons between these two mycobacterial subspecies suggest that differences in the oriC region may not be significant enough to account for the diverse bacterial replication rates. Finally, the few genetic differences present outside the origin of chromosomal replication in each genome may be responsible for the diverse growth rates or phenotypes observed between the avium and paratuberculosis subspecies.

Project description:The cross-reactivity of mycobacterial antigens in immune-based diagnostic assays has been a major concern and a criticism of the current tests that are used for the detection of paratuberculosis. In the present study, Mycobacterium avium subsp. paratuberculosis recombinant proteins were evaluated for antigenic specificity compared to a whole-cell sonicate preparation (MPS). Measures of cell-mediated immunity to M. avium subsp. paratuberculosis antigens were compared in calves inoculated with live M. avium subsp. paratuberculosis, M. avium subsp. avium (M. avium), Mycobacterium kansasii, or Mycobacterium bovis. Gamma interferon (IFN-γ) responses to MPS were observed in all calves that were exposed to mycobacteria compared to control calves at 4 months postinfection. Pooled recombinant M. avium subsp. paratuberculosis proteins also elicited nonspecific IFN-γ responses in inoculated calves, with the exception of calves infected with M. bovis. M. avium subsp. paratuberculosis proteins failed to elicit antigen-specific responses for the majority of immune measures; however, the expression of CD25 and CD26 was upregulated on CD4, CD8, gamma/delta (γδ) T, and B cells for the calves that were inoculated with either M. avium subsp. paratuberculosis or M. avium after antigen stimulation of the cells. Stimulation with MPS also resulted in the increased expression of CD26 on CD45RO(+) CD25(+) T cells from calves inoculated with M. avium subsp. paratuberculosis and M. avium. Although recombinant proteins failed to elicit specific responses for the calves inoculated with M. avium subsp. paratuberculosis, the differences in immune responses to M. avium subsp. paratuberculosis antigens were dependent upon mycobacterial exposure. The results demonstrated a close alignment in immune responses between calves inoculated with M. avium subsp. paratuberculosis and those inoculated with M. avium that were somewhat disparate from the responses in calves infected with M. bovis, suggesting that the biology of mycobacterial infection plays an important role in diagnosis.

Dataset Information

Contrasting results of culture-dependent and molecular analyses of Mycobacterium avium subsp. paratuberculosis from wood bison.

Publications

Contrasting results of culture-dependent and molecular analyses of Mycobacterium avium subsp. paratuberculosis from wood bison.

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