Variation in resistance of Mycobacterium paratuberculosis to acid environments as a function of culture medium

A novel biphasic approach to reactivation of dormant Mycobacterium avium subspecies paratuberculosis

A new culture technique that involves a potato slice and enriched Middlebrook 7H9 in a two-part glass tube has been developed to revive dormant or persistent Mycobacterium avium subspecies paratuberculosis and acclimate it to Middlebrook 7H9 liquid media. This method is more efficient than directly introducing the bacteria into the liquid medium.

Alpha-2-Macroglobulin as a New Promising Biomarker Improving the Diagnostic Sensitivity of Bovine Paratuberculosis

Johne's disease (JD) is a chronic granulomatous enteritis of ruminants caused by Mycobacterium avium subsp. paratuberculosis (MAP), which induces persistent diarrhea and cachexia. JD causes huge economic losses to the dairy industry due to reduced milk production and premature culling. Infected animals excrete MAP via feces during the prolonged subclinical stage without exhibiting any clinical signs. Therefore, accurate detection of subclinical stage animals is crucial for successful eradication of JD in the herd. In the current study, we analyzed serum samples of MAP-infected and non-infected cattle to identify potential biomarker candidates. First, we identified 12 differentially expressed serum proteins in subclinical and clinical shedder groups compared to the healthy control group. Second, we conducted ELISA for three selected biomarkers (alpha-2-macroglobulin (A2M), alpha-1-beta glycoprotein, and transthyretin) and compared their diagnostic performance with that of two commercial ELISA diagnostic kits. Serum A2M levels were significantly higher in the MAP-exposed, subclinical shedder, subclinical non-shedder, and clinical shedder groups than in the healthy control group, suggesting its possible use as a diagnostic biomarker for MAP infection. Furthermore, A2M demonstrated a sensitivity of 90.4%, and a specificity of 100% while the two commercial ELISA kits demonstrated a sensitivity of 67.83 and 73.04% and a specificity of 100%, respectively. In conclusion, our results suggest that measuring A2M by ELISA can be used as a diagnostic tool to detect MAP infection, considerably improving the detection rate of subclinical shedders and MAP-exposed animals that are undetectable using current diagnostic tools.

Paratuberculosis: A Potential Zoonosis and a Neglected Disease in Africa

The Mycobacterium avium subspecies paratuberculosis (MAP) is the causative agent of paratuberculosis, which is an economically important disease of ruminants. The zoonotic role of MAP in Crohn’s disease and, to a lesser extent, in ulcerative colitis, the two major forms of idiopathic inflammatory bowel disease (IIBD), has been debated for decades and evidence continues to mount in support of that hypothesis. The aim of this paper is to present a review of the current information on paratuberculosis in animals and the two major forms of IIBD in Africa. The occurrence, epidemiology, economic significance and “control of MAP and its involvement IIBD in Africa” are discussed. Although the occurrence of MAP is worldwide and has been documented in several African countries, the epidemiology and socioeconomic impacts remain undetermined and limited research information is available from the continent. At present, there are still significant knowledge gaps in all these areas as far as Africa is concerned. Due to the limited research on paratuberculosis in Africa, in spite of growing global concerns, it may rightfully be considered a neglected tropical disease with a potentially zoonotic role.

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.

A Mycobacterium avium subsp. paratuberculosis Predicted Serine Protease Is Associated with Acid Stress and Intraphagosomal Survival

The ability to maintain intra-cellular pH is crucial for bacteria and other microbes to survive in diverse environments, particularly those that undergo fluctuations in pH. Mechanisms of acid resistance remain poorly understood in mycobacteria. Although, studies investigating acid stress in M. tuberculosis are gaining traction, few center on Mycobacterium avium subsp. paratuberculosis (MAP), the etiological agent of chronic enteritis in ruminants. We identified a MAP acid stress response network involved in macrophage infection. The central node of this network was MAP0403, a predicted serine protease that shared an 86% amino acid identity with MarP in M. tuberculosis. Previous studies confirmed MarP as a serine protease integral to maintaining intra-bacterial pH and survival in acid in vitro and in vivo. We show that MAP0403 is upregulated in infected macrophages and MAC-T cells that coincided with phagosome acidification. Treatment of mammalian cells with bafilomcyin A1, a potent inhibitor of phagosomal vATPases, diminished MAP0403 transcription. MAP0403 expression was also noted in acidic medium. A surrogate host, M. smegmatis mc² 155, was designed to express MAP0403 and when exposed to either macrophages or in vitro acid stress had increased bacterial cell viability, which corresponds to maintenance of intra-bacterial pH in acidic (pH = 5) conditions, compared to the parent strain. These data suggest that MAP0403 may be the equivalent of MarP in MAP. Future studies confirming MAP0403 as a serine protease and exploring its structure and possible substrates are warranted.

Virulence and immunity orchestrated by the global gene regulator sigL in Mycobacterium avium subsp. paratuberculosis

Mycobacterium avium subsp. paratuberculosis causes Johne's disease in ruminants, a chronic enteric disease responsible for severe economic losses in the dairy industry. Global gene regulators, including sigma factors are important in regulating mycobacterial virulence. However, the biological significance of such regulators in M. avium subsp. paratuberculosis rremains elusive. To better decipher the role of sigma factors in M. avium subsp. paratuberculosis pathogenesis, we targeted a key sigma factor gene, sigL, activated in mycobacterium-infected macrophages. We interrogated an M. avium subsp. paratuberculosis ΔsigL mutant against a selected list of stressors that mimic the host microenvironments. Our data showed that sigL was important in maintaining bacterial survival under such stress conditions. Survival levels further reflected the inability of the ΔsigL mutant to persist inside the macrophage microenvironments. Additionally, mouse infection studies suggested a substantial role for sigL in M. avium subsp. paratuberculosis virulence, as indicated by the significant attenuation of the ΔsigL-deficient mutant compared to the parental strain. More importantly, when the sigL mutant was tested for its vaccine potential, protective immunity was generated in a vaccine/challenge model of murine paratuberculosis. Overall, our study highlights critical role of sigL in the pathogenesis and immunity of M. avium subsp. paratuberculosis infection, a potential role that could be shared by similar proteins in other intracellular pathogens.

Acetic Acid, the active component of vinegar, is an effective tuberculocidal disinfectant

Effective and economical mycobactericidal disinfectants are needed to kill both Mycobacterium tuberculosis and non-M. tuberculosis mycobacteria. We found that acetic acid (vinegar) efficiently kills M. tuberculosis after 30 min of exposure to a 6% acetic acid solution. The activity is not due to pH alone, and propionic acid also appears to be bactericidal. M. bolletii and M. massiliense nontuberculous mycobacteria were more resistant, although a 30-min exposure to 10% acetic acid resulted in at least a 6-log10 reduction of viable bacteria. Acetic acid (vinegar) is an effective mycobactericidal disinfectant that should also be active against most other bacteria. These findings are consistent with and extend the results of studies performed in the early and mid-20th century on the disinfectant capacity of organic acids. IMPORTANCE Mycobacteria are best known for causing tuberculosis and leprosy, but infections with nontuberculous mycobacteria are an increasing problem after surgical or cosmetic procedures or in the lungs of cystic fibrosis and immunosuppressed patients. Killing mycobacteria is important because Mycobacterium tuberculosis strains can be multidrug resistant and therefore potentially fatal biohazards, and environmental mycobacteria must be thoroughly eliminated from surgical implements and respiratory equipment. Currently used mycobactericidal disinfectants can be toxic, unstable, and expensive. We fortuitously found that acetic acid kills mycobacteria and then showed that it is an effective mycobactericidal agent, even against the very resistant, clinically important Mycobacterium abscessus complex. Vinegar has been used for thousands of years as a common disinfectant, and if it can kill mycobacteria, the most disinfectant-resistant bacteria, it may prove to be a broadly effective, economical biocide with potential usefulness in health care settings and laboratories, especially in resource-poor countries.

Growth of Mycobacterium avium subsp. paratuberculosis, Escherichia coli, and Salmonella Enteritidis during Preparation and Storage of Yogurt

The purpose of this study was to determine the viability of Mycobacterium avium subsp. paratuberculosis (MAP), Escherichia coli (E. coli), and Salmonella Enteritidis (S. Enteritidis) during preparation and refrigerated storage of yogurt. Three yogurts were prepared using pasteurized commercial milk. Each yogurt was artificially contaminated with (1) MAP, (2) E. coli + S. Enteritidis, and (3) MAP + E. coli + S. Enteritidis. Samples were taken during and after the fermentation process until day 20 after inoculation. MAP was not detected during their preparation and short-term storage but was recuperated after starting at 180 min after inoculation storage. Live bacterial counts of E. coli, and S. Enteritidis increased during the first 24 hours, followed by a slight decrease towards the end of the study. In this study it was shown how MAP, E. coli, and S. Enteritidis resisted the acidic conditions generated during the preparation of yogurt and low storage temperatures. This work contributes to current knowledge regarding survival of MAP, E. coli, and S. Enteritidis during preparation and refrigerated storage of yogurt and emphasizes the need to improve hygiene measures to ensure the absence of these pathogenic microorganisms in dairy products.

Mycobacterium avium subsp. paratuberculosis survival during fermentation of soured milk products detected by culture and quantitative real time PCR methods

Mycobacterium avium paratuberculosis (MAP), etiological agent of paratuberculosis in ruminants, is able to survive extreme conditions like very low pH (stomach), high temperature (pasteurization) or low temperature (refrigerated storage). Cheese, infant powder milk, cream and other milk and dairy products might thus be considered as possible sources of MAP for humans. The aim of this study was to investigate the survival of two MAP field isolates during fermentation of three different types of soured milk products (SMP; yogurt, acidophilus milk and kefir) under laboratory conditions. Pasteurized MAP-free milk was artificially contaminated with 10(6)MAPcells/mL and survival and absolute numbers of MAP were monitored during fermentation (4 or 16 h) and after six weeks of storage at 4°C by culture and quantitative real time PCR (qPCR). Viability of MAP was determined by culture using Herrold's egg yolk medium and Middlebrook 7H10 with antibiotics, supplemented with Mycobactin J and incubated at 37°C for up to 12 weeks. The absolute numbers of MAP were quantified by previously published qPCR assays targeting F57 and IS900 loci in MAP genome. We herein confirm that MAP can survive pH reduction, however, longer exposure to pH below 4 in SMP seems to be critical because it inhibits growth. Therefore, it is suggested that probiotic cultures that can decrease pH below 4 during fermentation could provide better inactivation of MAP in SMP.

Analysis of the antimicrobial responses of primary phagocytes of the goldfish (Carassius auratus L.) against Mycobacterium marinum

The slow growth rate of Mycobacterium spp. that infect humans coupled with a lack of reliable in vitro infection model systems has hindered the progress of research in host cell-mycobacteria interactions. Recent studies have utilized the relatively fast growing Mycobacterium marinum to examine the host-pathogen interface in natural fish hosts. Here we describe the use of primary goldfish monocyte and mature macrophage cultures to investigate the immune cell-M. marinum interactions. Live and heat-killed M. marinum abrogated the recombinant goldfish (rg)TNFα2 and rgIFNγ-induced monocyte reactive oxygen production. Live but not heat-killed M. marinum also ablated rgIFNγrel and rg-TNFα2 induced macrophage nitric oxide production. M. marinum induced significant changes in gene expression of select NADPH oxidase components and inflammatory cytokine receptors and up-regulated the expression of immunosuppressive genes IL-10, TGFβ1 and SOCS-3. The exposure of monocytes and mature macrophages to M. marinum caused an increase in the mRNA levels of several pro-inflammatory genes. Stimulation of monocytes and macrophages with rgTNFα2, rgIFNγ, or rgIFNγrel reduced the survival of intracellular mycobacteria. The characterization of the interaction between M. marinum and natural host-derived primary phagocyte cultures will enable future studies on the host-pathogen interactions in mycobacterial infections.

Mycobacterium avium subspecies Paratuberculosis and Crohn's regional ileitis: how strong is association?

Mycobacterium avium subsp. paratuberculosis (MAP) is a well-established etiological agent of Johne's disease in animals. In humans, similar clinical condition, first described by Crohn as regional ileitis in 1932, now known as Crohn's diseases (CD), has also been associated with this mycobacterial species. However, there are two schools of thoughts, one favoring MAP as its etiological agent while the second considers it as an immune-inflammatory condition triggered by an external factor. Onset of CD requires a series of events including predisposition of certain inherited genetic traits, associated environmental stimuli, and immune-inflammatory response. A combination of these factors probably leads to this disease. Recently, some human genes have also been identified which regulate ability to respond appropriately to the external factors. Added to these factors are concerns about the selection of clinical specimens and poor adherence to laboratory quality controls. The literature is full of contradictory findings, but there a lack of uniformity in the materials and methods used by many of these researchers. In this review, we provide our perspective under above circumstances and give our point of view which may open a platform for debate regarding the MAP as the etiological agent of human CD.

Mycobacterium avium subsp. paratuberculosis in dairy products, meat, and drinking water

Mycobacterium avium subsp. paratuberculosis (Map) is the cause of Johne's disease, a chronic infection of the gut, in ruminant animals that provide milk and/or meat for human consumption. Map also may be involved in Crohn's disease and type 1 diabetes in humans. Although the role of Map in human diseases has not been established, minimizing the exposure of humans to the organism is considered desirable as a precautionary measure. Infected animals can shed Map in feces and milk, and the organism can become disseminated in tissues remote from the gut and its associated lymph nodes. The presence of at least some Map in raw milk and meat and in natural waters is likely, but the numbers of Map in those foods and waters should be reduced through cooking or purification. The available information relating to Map in milk and dairy products, meats, and drinking water is reviewed here for assessment of the risks of exposure to Map from consumption of such foods and water.

Comparison of culture methods for isolation of nontuberculous mycobacteria from surface waters

The environment is the likely source of most nontuberculous mycobacteria (NTM) involved in human infections, especially pulmonary, skin, and soft tissue infections. In order to measure the prevalence of NTM in different aquatic ecosystems, we tried to standardize the culture methods used for surface water testing since many procedures have been described previously. Cultivation of mycobacteria requires long-term incubation in rich media and inactivation of rapidly growing microorganisms whose growth impedes observation of mycobacterial colonies. Consequently, the two criteria used for evaluation of the methods examined were (i) the rate of inhibition of nontarget microorganisms and (ii) the efficiency of recovery of mycobacteria. We compared the competitive growth of Mycobacterium chelonae and M. avium with nontarget microorganisms on rich Middlebrook 7H11-mycobactin medium after treatment by several chemical decontamination methods that included acids, bases, detergent, or cetylpyridinium chloride (CPC) with and without an antibiotic cocktail, either PANTA (40 U/ml polymyxin, 4 microg/ml amphotericin B, 16 microg/ml nalidixic acid, 4 microg/ml trimethoprim, and 4 microg/ml azlocillin) or PANTAV (PANTA plus 10 microg/ml vancomycin). Our results showed that treatment for 30 min with CPC (final concentration, 0.05%) of water concentrated by centrifugation, followed by culture on a rich medium supplemented with PANTA, significantly decreased the growth of nontarget microorganisms (the concentrations were 6.2 +/- 0.4 log(10) CFU/liter on Middlebrook 7H11j medium and 4.2 +/- 0.2 log(10) CFU/liter on Middlebrook 7H11j medium containing PANTA [P < 0.001]), while the effect of this procedure on NTM was not as great (the concentrations of M. chelonae on the two media were 7.0 +/- 0.0 log(10) CFU/liter and 6.9 +/- 0.0 log(10) CFU/liter, respectively, and the concentrations of M. avium were 9.1 +/- 0.0 log(10) CFU/liter and 8.9 +/- 0.0 log(10) CFU/liter, respectively). We propose that this standardized culture procedure could be used for detection of NTM in aquatic samples.

Mycobacterial survival strategies in the phagosome: defence against host stresses

Infections with Mycobacterium tuberculosis remain a major cause of disease and death in humans. Among the factors that contribute to M. tuberculosis's success as a pathogen is its ability to withstand potentially bactericidal host defences and to resist elimination by an activated immune system. This resistance to killing by the host is in part due to the low permeability of the mycobacterial cell envelope for many toxic molecules. In addition, it depends upon the detoxification of reactive oxygen and reactive nitrogen molecules produced by the host, the repair of the damage these molecules cause and maintenance of a neutral intrabacterial pH within acidic environments. The latter three mechanisms are the focus of this review.

Monensin causes dose dependent inhibition of Mycobacterium avium subspecies paratuberculosis in radiometric culture

Background

Mycobacterium avium subspecies paratuberculosis (MAP) causes a chronic wasting diarrheal disease in ruminants called Johne's disease, that is evocative of human inflammatory bowel disease (IBD). Agents used to treat IBD, called "anti-inflammatories", immuno-modulators" and "immuno-suppressants" inhibit MAP growth in culture. We concluded that, unknowingly, the medical profession has been treating MAP since sulfasalazine's introduction in 1942. Monensin, called a "Growth Enhancer" in cattle, ameliorates Johne's disease without a documented mechanism of action. We hypothesized that Monensin would inhibit MAP in culture.

Methods

Using the radiometric ¹⁴CO₂ Bactec^® system, that expresses mycobacterial growth in arbitrary growth index (GI) units, we studied the effect of Monensin on the growth kinetic of MAP isolated from humans with IBD ("Dominic", "Ben" & UCF-4) and cattle with Johne's disease (303 & ATCC 19698.) Results are expressed as percent inhibition of cumulative GI (%–ΔcGI).

Results

The positive control Clofazimine inhibits every strain tested. The negative controls Cycloheximide & Phthalimide, have no inhibition on any MAP strain. Monensin has dose dependent inhibition on every MAP strain tested. The most susceptible human isolate was UCF-4 (73% – ΔcGI at 1 μg/ml) and bovine isolate was 303 (73% – ΔcGI at 4 μg/ml.) Monensin additionally inhibits M. avium ATCC 25291 (87% – ΔcGI at 64 μg/ml) & BCG (92% – ΔcGI at 16 μg/ml).

Discussion

We show that in radiometric culture the "Growth Enhancer" Monensin causes dose dependent inhibition of mycobacteria including MAP. We posit that the "Growth Enhancer" effect of Monensin may, at least in part, be due to inhibition of MAP in clinical or sub-clinical Johne's disease.

Diagnosis of bovine paratuberculosis by a novel enzyme-linked immunosorbent assay based on early secreted antigens of Mycobacterium avium subsp. paratuberculosis

We previously reported that protein antigens of serodiagnostic potential were more abundant in culture filtrates than cellular extracts from liquid cultures of Mycobacterium avium subsp. paratuberculosis (D. Cho and M. T. Collins, Clin. Vaccine Immunol. 13:1155-1161, 2006). Based on this observation, a novel enzyme-linked immunosorbent assay (ELISA) using antigens secreted by young (early- to mid-log-phase) cultures of M. avium subsp. paratuberculosis JTC303 (a low-passage isolate originating from the ileum of a Holstein bull) in mycobactin-supplemented Watson-Reid medium (pH 6.0) was developed and evaluated using a previously described panel of bovine sera (M. T. Collins et al., Clin. Diagn. Lab. Immunol. 12:685-692, 2005) that included 444 paratuberculosis cases and 412 controls. The new assay, called JTC-ELISA, had a significantly higher diagnostic sensitivity and an equivalent specificity compared to those of five commercial paratuberculosis ELISA kits. By receiver-operating characteristic analysis, the JTC-ELISA had the highest area under the curve of the six assays evaluated. The JTC-ELISA was particularly sensitive at detecting low-level fecal shedders of Mavium subsp. paratuberculosis (40%; the sensitivity of the commercial kits was 20%). The JTC-ELISA works effectively on both serum and milk samples for the detection of cattle with subclinical M. avium subsp. paratuberculosis infections, providing a cost-effective diagnostic tool to support paratuberculosis control programs in cattle herds.

Rapid and reliable method for quantification of Mycobacterium paratuberculosis by use of the BACTEC MGIT 960 system

A simple method for the enumeration of viable Mycobacterium paratuberculosis cells was developed and evaluated using the MGIT 960 culture system. For each of 12 M. paratuberculosis strains isolated from either cattle or humans, single-cell suspensions of M. paratuberculosis cells were adjusted to an optical density at 600 nm of 1.00 (10(7.6) to 10(8.2) cells/ml), and serial dilutions were prepared. Standard curves were established by relating the MGIT time-to-detection data to the log10 CFU for these suspensions using standard plate counting and BACTEC 460 results as reference methods. Universal and strain-specific standard quantification curves were generated. A one-phase exponential decay equation best fit the universal standard curve and strain-specific curves (R2 of 0.96 and >0.99, respectively). Two subgroups within the universal curves were distinguished: one for laboratory-adapted strains and the other for recently isolated low-passage bovine strains. The predictive errors for log(10) estimations using the universal standard curve, each subgroup's standard curve, and strain-specific curves were +/-0.87, +/-0.45, and +/-0.31 log10 units, respectively. CFU estimations by all three standard curves were highly reproducible, regardless of the M. paratuberculosis strain or inoculum volume. In comparison with the previously described BACTEC 460 M. paratuberculosis counting method, quantification with MGIT 960 was less expensive, more rapid, more accurate, and more sensitive (<10 CFU). This MGIT counting method has broad applications for studies requiring the quantification of viable M. paratuberculosis cells, such as drug susceptibility testing or environmental survival studies.

Comparison of the proteosomes and antigenicities of secreted and cellular proteins produced by Mycobacterium paratuberculosis

The protein expression profiles and antigenicities of both culture filtrates (CF) and cellular extracts (CE) of Mycobacterium paratuberculosis were compared by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), one-dimensional electrophoresis (1-DE) and 2-DE immunoblotting, and enzyme-linked immunosorbent assay (ELISA). The CF proteins were harvested from supernatants of stationary-phase liquid cultures and concentrated by size exclusion filtration. The CE proteins were extracted by mechanical disruption of cells using glass beads and a high-speed agitator. Analysis of SDS-PAGE gels showed that the majority of CF proteins had low molecular masses (<50 kDa), whereas CE protein mass ranged more evenly over a broader range up to 100 kDa. By 2-DE, CF proteins had a narrow array of pI values, with most being between pH 4.0 and 5.5; CE proteins spanned pI values from pH 4.0 to 7.0. The antigenicities of CF and CE proteins were first determined by 1-DE and 2-DE immunoblotting with serum from a cow naturally infected with M. paratuberculosis. The serum reacted strongly to more proteins in the CF than the CE. Sera from 444 infected and 412 uninfected cattle were tested by ELISA with CF and CE as solid-phase antigens. Receiver-operator characteristic curve analysis of the ELISA results showed a significantly greater area under the curve for CF compared to CE (P<0.05). A high degree of variability in protein binding patterns was shown with 1-DE immunoblot analysis with 31 sera from M. paratuberculosis-infected cattle. Collectively, these results indicate that serologic tests for bovine paratuberculosis may be improved by using proteins derived from CF instead of CE. To maximize the diagnostic sensitivity of serologic tests, multiple proteins will be required. Even so, a CF ELISA may not be able to detect all M. paratuberculosis-infected cattle, in particular those in the early stages of infection that have yet to mount an antibody response.

Proteome and differential expression analysis of membrane and cytosolic proteins from Mycobacterium avium subsp. paratuberculosis strains K-10 and 187

Little is known of protein expression in Mycobacterium avium subsp. paratuberculosis and how this contributes to pathogenesis. In the present study, proteins from both membranes and cytosol were prepared from two strains of M. avium subsp. paratuberculosis, i.e., laboratory-adapted strain K-10 and a recent isolate, strain 187, obtained from a cow exhibiting clinical signs of Johne's disease. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of cytosol and membrane proteins from K-10 and 187 showed marked differences in protein expression. Relative levels of protein expression from both M. avium subsp. paratuberculosis strains were measured by using amine-reactive isobaric tagging reagents (iTRAQ) and tandem mass spectroscopy. Protein identification and relative expression data were obtained for 874 membrane and cytosolic proteins from the M. avium subsp. paratuberculosis proteome. These data showed a number of significant differences in protein expression between strain K-10 and clinical isolate 187. Examples of proteins expressed at higher levels in clinical isolate 187 compared to strain K-10 are AtpC, RpoA, and several proteins involved in fatty acid biosynthesis. In contrast, proteins such as AhpC and several proteins involved in nitrogen metabolism were expressed at higher levels in strain K-10 compared to strain 187. These data may provide insights into the proteins whose expression is important in natural infection but are modified once M. avium subsp. paratuberculosis is adapted to laboratory cultivation. Results from these studies will provide tools for developing a better understanding of M. avium subsp. paratuberculosis infection in the host and offer potential as diagnostic reagents and vaccine candidates.

Interaction between Mycobacterium avium subsp. paratuberculosis and environmental protozoa

Background

Interactions between Mycobacterium avium subsp. paratuberculosis (Map) and free-living protozoa in water are likely to occur in nature. The potential impact of ingestion of Map by two naturally occurring Acanthamoeba spp. on this pathogen's survival and chlorine resistance was investigated.

Results

Between 4.6 and 9.1% of spiked populations of three Map strains (NCTC 8578, B2 and ATCC 19698), which had been added at a multiplicity of infection of 10:1, were ingested by Acanthamoeba castellanii CCAP 1501/1B and A. polyphaga CCAP 1501/3B during co-culture for 3 h at 25°C. Map cells were observed to be present within the vacuoles of the amoebae by acid-fast staining. During extended co-culture of Map NCTC 8578 at 25°C for 24 d with both A. castellanii and A. polyphaga Map numbers did not change significantly during the first 7 days of incubation, however a 1–1.5 log₁₀ increase in Map numbers was observed between days 7 and 24 within both Acanthamoeba spp. Ingested Map cells were shown to be more resistant to chlorine inactivation than free Map. Exposure to 2 μg/ml chlorine for 30 min resulted in a log₁₀ reduction of 0.94 in ingested Map but a log₁₀ reduction of 1.73 in free Map (p < 0.001).

Conclusion

This study demonstrated that ingestion of Map by and survival and multiplication of Map within Acanthamoeba spp. is possible, and that Map cells ingested by amoebae are more resistant to inactivation by chlorine than free Map cells. These findings have implications with respect to the efficacy of chlorination applied to Map infected surface waters.

Growth of Metarhizium anisopliae on non-preferred carbon sources yields conidia with increased UV-B tolerance

Conidia of the insect-pathogenic fungus Metarhizium anisopliae var. anisopliae produced on different growth substrates (culture media or insect cadavers) demonstrate reproducibly altered tolerance to UV-B radiation [Rangel, D.E.N., Braga, G.U.L., Flint, S.D., Anderson, A.J., Roberts, D.W., 2004. Variations in UV-B tolerance and germination speed of M. anisopliae conidia produced on artificial and natural substrates. J. Invertebr. Pathol. 87, 77-83]. In the current study, the fungus was grown on potato dextrose agar with yeast extract (PDAY), on minimal medium [(MM)=Czapek medium without saccharose], or on MM with one of 16 different carbon sources. The conidia produced on these media were exposed to UV-B radiation. Great amplitude in phenotypic plasticity for UV-B tolerance was demonstrated, viz., conidia produced under nutritive stress [MM or MM supplemented with non-preferred carbon sources (e.g., fructose, galactose, lactose etc.)] had at least two times higher tolerance than conidia produced on the rich medium (PDAY). Endogenous trehalose and mannitol accumulated at least two times more in conidia produced on MM (or MM with lactose, a non-preferred carbon source), as compared to conidia from MM plus glucose. High accumulations of these two carbohydrates in fungal spores are known to protect them against a wide range of stresses. Sporulation, however, was most profuse on PDAY, second best on MM plus d-mannose and least on MM or MM containing non-preferred carbon sources. Taken together, the results illustrate that nutritive stress generated by MM or MM plus a non-preferred carbon source greatly improved UV-B tolerance, but reduced conidial yield; while, on the other hand, preferred carbon sources improved conidial yield, but reduced UV-B tolerance.

Effect of egg yolk on the detection of Mycobacterium avium subsp. paratuberculosis using the ESP II liquid culture system

Rapid diagnosis of paratuberculosis in infected cattle is important for the successful control of Johne disease within herds. Thus, improving culture methods for Mycobacterium avium subsp. paratuberculosis (M. paratuberculosis) will aid in the identification of asymptomatic animals. Egg yolk is a component of the media used for growing M. paratuberculosis, but its requirement as a supplement has not been reported. Using the ESP II liquid culture system, 2 different sources and 5 concentrations (3.3%, 1.6%, 0.8%, 0.4%, and 0%) of egg yolk were analyzed. Egg yolk source did not affect either recovery rate or time to detection, but both parameters were significantly improved when the 3.3% egg yolk concentrations (final volume) were used over media containing no egg yolk. This study also assessed the recovery of M. paratuberculosis from fecal samples that were cultured multiple times using Herrold egg yolk agar (HEY). Specimens containing greater than 70 cfu/g feces could routinely be identified as positive for M. paratuberculosis after only 1 culture attempt, whereas specimens with fewer bacteria were only intermittently positive, even after 5 replicate cultures. Therefore, this study indicates that the sensitivity of the Trek Diagnostic ESP II liquid culture system for M. paratuberculosis is affected by egg yolk concentration and that single culture attempts using HEY solid media may not identify specimens containing low numbers of bacteria.

Mutants of Mycobacterium smegmatis unable to grow at acidic pH in the presence of the protonophore carbonyl cyanide m-chlorophenylhydrazone

Mycobacterium smegmatis is able to grow and survive at acidic pH, and exhibits intracellular pH homeostasis under these conditions. In this study, the authors have identified low proton permeability of the cytoplasmic membrane, and high cytoplasmic buffering capacity, as determinants of intrinsic acid resistance of M. smegmatis. To identify genes encoding proteins involved in protecting cells from acid stress, a screening method was developed using the electrogenic protonophore carbonyl cyanide m-chlorophenylhydrazone (CCCP). CCCP was used to suppress intrinsic acid resistance of M. smegmatis. The screen involved exposing cells to pH 5.0 in the presence of CCCP, and survivors were rescued at various time intervals on solid medium at pH 7.5. Cells capable of responding to intracellular acidification (due to CCCP-induced proton equilibration) will survive longer under these conditions than acid-sensitive cells. From a total pool of 5000 transposon (Tn611) insertion mutants screened, eight acid-sensitive M. smegmatis mutants were isolated. These acid-sensitive mutants were unable to grow at pH 5.0 in the presence of 1-5 microM CCCP, a concentration not lethal to the wild-type strain mc2155. The DNA flanking the site of Tn611 was identified using marker rescue in Escherichia coli, and DNA sequencing to identify the disrupted locus. Acid-sensitive mutants of M. smegmatis were disrupted in genes involved in phosphonate/phosphite assimilation, methionine biosynthesis, the PPE multigene family, xenobiotic-response regulation and lipid biosynthesis. Several of the acid-sensitive mutants were also defective in stationary-phase survival, suggesting that overlapping stress protection systems exist in M. smegmatis.

Possible association of GroES and antigen 85 proteins with heat resistance of Mycobacterium paratuberculosis

Conflicting reports on the heat resistance of Mycobacterium paratuberculosis prompted an examination of the effect of culture medium on this property of the organism. M. paratuberculosis was cultured in three types of media (fatty acid-containing medium 7H9-OADC (oleic acid-albumin-dextrose-catalase supplement) and glycerol-containing media WR-GD and 7H9-GD [glycerol-dextrose supplement]) at pH 6.0. M. paratuberculosis grown under these three culture conditions was then tested for heat resistance in distilled water at 65 degrees C. Soluble proteins and mycolic acids of M. paratuberculosis were evaluated by two-dimensional electrophoresis (2-DE) and thin-layer chromatography (TLC), respectively. The type of culture medium used significantly affected the heat resistance of M. paratuberculosis. The decimal reduction times at 65 degrees C (D(65 degrees C) values; times required to reduce the concentration of bacteria by a factor of 10 at 65 degrees C) for M. paratuberculosis strains grown in 7H9-OADC were significantly higher than those for the organisms grown in WR-GD medium (P < 0.01). When the glycerol-dextrose supplement of WR was substituted for the fatty acid supplement (OADC) in 7H9 medium (resulting in 7H9-GD), the D(65 degrees C) value was significantly lower than that for the organism grown in 7H9-OADC medium (P = 0.022) but higher than that when it was cultured in WR-GD medium (P = 0.005). Proteomic analysis by 2-DE of soluble proteins extracted from M. paratuberculosis grown without heat stress in the three media (7H9-OADC, 7H9-GD, and WR-GD) revealed that seven proteins were more highly expressed in 7H9-OADC medium than in the other two media. When the seven proteins were subjected to matrix-assisted laser desorption ionization-mass spectrometric analysis, four of the seven protein spots were unidentifiable. The other three proteins were identified as GroES heat shock protein, alpha antigen, and antigen 85 complex B (Ag85B; fibronectin-binding protein). These proteins may be associated with the heat resistance of M. paratuberculosis. Alpha antigen and Ag85B are both trehalose mycolyltransferases involved in mycobacterial cell wall assembly. TLC revealed that 7H9-OADC medium supported production of more trehalose dimycolates and cell wall-bound mycolic acids than did WR-GD medium. The present study shows that in vitro culture conditions significantly affect heat resistance, cell wall synthesis, and protein expression of M. paratuberculosis and emphasize the importance of culture conditions on in vitro and ex vivo studies to estimate heat resistance.