Pasteurization of milk and the heat resistance of Mycobacterium avium subsp. paratuberculosis: a critical review of the data

Effective Isolation and Characterization of Mycobacteriophages with the Ability to Lyse Mycobacterium avium subsp. paratuberculosis

Johne's disease (JD), a chronic infectious enteritis of ruminants, causes major economic losses in the dairy industry globally. This enteritis is caused by Mycobacterium avium subsp. Paratuberculosis (MAP). Currently there is no cure for JD and test-based culling has proved ineffective at preventing the spread. To isolate new mycobacteriophages (mbps) that can potentially be used to control JD transmission and infection on dairy farms, we optimized an isolation protocol by fecal spiking and the testing of different isolation solution compositions. Using this protocol, we successfully enhanced the yield of mbps from spiked fecal samples, elevating it from less than 1% to 59%. With this method, we isolated 14 mbps from 475 environmental samples collected from MAP-positive dairy farms, after in-sample enrichment with MAP and the fast-growing M. smegmatis. The sample sources included soil, manure pits, lactation barns, feces, milk, and drain water. After fingerprinting these mbps by restriction enzyme profiling, we concluded that 12 were distinct and novel. Further characterization of their host range revealed that eight were capable of lysing multiple MAP strains. We also studied the cross-resistance, lysogeny, the effect of pH and their antimycobacterial properties in milk replacer. Each novel mbp showed limited cross-resistance and prophage immunity and showed no reduction in the titer in a range of pHs after 4 h. The novel phages were also able to reduce the mycobacterial counts to zero after 8 h in milk replacer. In conclusion, these novel mbps could be considered to be used in the control strategies of JD on farms.

The efficacy and safety of high-pressure processing of food

High-pressure processing (HPP) is a non-thermal treatment in which, for microbial inactivation, foods are subjected to isostatic pressures (P) of 400-600 MPa with common holding times (t) from 1.5 to 6 min. The main factors that influence the efficacy (log10 reduction of vegetative microorganisms) of HPP when applied to foodstuffs are intrinsic (e.g. water activity and pH), extrinsic (P and t) and microorganism-related (type, taxonomic unit, strain and physiological state). It was concluded that HPP of food will not present any additional microbial or chemical food safety concerns when compared to other routinely applied treatments (e.g. pasteurisation). Pathogen reductions in milk/colostrum caused by the current HPP conditions applied by the industry are lower than those achieved by the legal requirements for thermal pasteurisation. However, HPP minimum requirements (P/t combinations) could be identified to achieve specific log10 reductions of relevant hazards based on performance criteria (PC) proposed by international standard agencies (5-8 log10 reductions). The most stringent HPP conditions used industrially (600 MPa, 6 min) would achieve the above-mentioned PC, except for Staphylococcus aureus. Alkaline phosphatase (ALP), the endogenous milk enzyme that is widely used to verify adequate thermal pasteurisation of cows' milk, is relatively pressure resistant and its use would be limited to that of an overprocessing indicator. Current data are not robust enough to support the proposal of an appropriate indicator to verify the efficacy of HPP under the current HPP conditions applied by the industry. Minimum HPP requirements to reduce Listeria monocytogenes levels by specific log10 reductions could be identified when HPP is applied to ready-to-eat (RTE) cooked meat products, but not for other types of RTE foods. These identified minimum requirements would result in the inactivation of other relevant pathogens (Salmonella and Escherichia coli) in these RTE foods to a similar or higher extent.

Phagomagnetic separation-quantitative PCR: A rapid, sensitive and specific surveillance tool for viable Mycobacterium avium ssp. paratuberculosis in bulk tank and individual cow milk samples

Bulk tank milk samples from 392 Northern Ireland dairy farms and individual milk from animals (n = 293) on 4 of these farms were tested by a novel phagomagnetic separation (PhMS)-quantitative (q)PCR assay able to detect and quantify viable Mycobacterium avium ssp. paratuberculosis (MAP), to demonstrate its potential utility as a milk surveillance tool. Viable MAP were detected in 26.5% of the bulk tank milks, with MAP contamination levels ranging from 1 to 8,432 MAP/50 mL of milk; less than 2% of farms had MAP contamination levels >100 MAP/50 mL in their bulk tank milk. Follow-up PhMS-qPCR testing of milk from individual animals on 4 farms that had the highest numbers of MAP in their bulk tank milks indicated that 17 to 24% of animals in each herd were shedding viable MAP in their milk. Mean MAP numbers detected ranged between 6.7 and 42.1 MAP/50 mL of milk. No significant correlation was observed between the detection of viable MAP in bulk or individual milks by PhMS-qPCR and parallel milk ELISA results, or between PhMS-qPCR results and any other milk recording results (somatic cell count, total bacterial count, % butterfat, or % protein). Viable MAP was detected by IS900 qPCR in 52 (85.2%) Pozzato broth cultures of 61 PhMS-qPCR-positive individual milks after 12 wk of incubation, suggesting few PhMS-qPCR results were false positives. The mean sensitivities of the PhMS-qPCR assay and milk ELISA applied to individual milks were estimated by Bayesian latent class analysis to be 0.7096 and 0.2665, respectively, and mean specificities were similar (0.9626 and 0.9509). Our findings clearly demonstrate that the novel PhMS-qPCR assay could be a useful milk surveillance tool for dairy processors, or a milk monitoring tool for Johne's disease control or milk quality assurance programs.

Dietary Regulation of the Crosstalk between Gut Microbiome and Immune Response in Inflammatory Bowel Disease

Inflammatory bowel disease (IBD), a chronic, recurring inflammatory response, is a growing global public health issue. It results from the aberrant crosstalk among environmental factors, gut microbiota, the immune system, and host genetics, with microbiota serving as the core of communication for differently-sourced signals. In the susceptible host, dysbiosis, characterized by the bloom of facultative anaerobic bacteria and the decline of community diversity and balance, can trigger an aberrant immune response that leads to reduced tolerance against commensal microbiota. In IBD, such dysbiosis has been profoundly proven in animal models, as well as clinic data analysis; however, it has not yet been conclusively ascertained whether dysbiosis actually promotes the disease or is simply a consequence of the inflammatory disorder. Better insight into the complex network of interactions between food, the intestinal microbiome, and host immune response will, therefore, contribute significantly to the diagnosis, treatment, and management of IBD. In this article, we review the ways in which the mutualistic circle of dietary nutrients, gut microbiota, and the immune system becomes anomalous during the IBD process, and discuss the roles of bacterial factors in shaping the intestinal inflammatory barrier and adjusting immune capacity.

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.

Evaluation of Mycobacterium smegmatis as indicator of the efficacy of high hydrostatic pressure and ultra-high pressure homogenization treatments for pasteurization-like purposes in milk

The objectives of this study were: to assess the efficiency of high hydrostatic pressure or ultra-high pressure homogenization against Mycobacterium smegmatis in milk and to discuss whether M. smegmatis can be considered a suitable surrogate for other Mycobacterium spp. in high pressure inactivation trials using milk. Three strains of this specie (CECT 3017, 3020 and 3032) were independently inoculated into both skimmed (0.2% fat) and whole milk (3.4% fat) at an approximate load of 6.5 Log CFU/ml and submitted to HHP treatments at 300, 400 or 500 MPa for 10 m at 6°C and 20°C. Evolution of the surviving cells of the inoculated strains was evaluated analysing milk immediately after the treatments and after 5 and 8 d of storage at 6°C. HHP treatments at 300 MPa were seldom efficient at inactivating M. smegmatis strains, but lethality increased with pressure applied in all cases. Generation of sub-lethal injured cells was observed only after 400 MPa treatments since inactivation at 500 MPa was shown to be complete. Significant differences were not observed due to either temperature of treatment or fat content of milk, except for strain CECT3032, which was shown to be the most sensitive to HHP treatments. Milk inoculated with strain CECT3017 was submitted to ultra-high pressure homogenization (UHPH) treatments at 200, 300 and 400 MPa. Maximum reductions were obtained after 300 and 400 MPa treatments, although less than 3.50 Log CFU/ml were inactivated. UHPH did not cause significant number of injured cells. The usefulness of this species as a marker for pressure-based processing seems limited since it showed greater sensitivity than some pathogenic species including other Mycobacteria reported in previous studies.

Mycobacterium avium subspecies paratuberculosis - an important food borne pathogen of high public health significance with special reference to India: an update

This review underlines the public health significance of 'Indian Bison Type' of Mycobacterium avium subspecies paratuberculosis (MAP) and also its potential as 'zoonotic infection'. In the absence of control programs, bio-load of MAP is increasing and if we take total population of animals (500 million plus) and human beings (1.23 billion plus) into account, the number of infected animals and human beings will run into millions in India. Our research on screening of over 26,000 domestic livestock for MAP infection using 4 different diagnostic tests (microscopy, culture, ELISA and PCR), during last 31 years has shown that the average bio-load of MAP in the livestock population of India is very high (cattle 43%, buffaloes 36%, goats 23% and sheep 41%). 'Mass screening' of 28,291 human samples between 2008-2016 revealed also high bio-load of MAP. It has been proved that MAP is not in-activated during pasteurization and therefore live bacilli are continuously reaching human population by consumption of even pasteurized milk and other milk products. Live bacilli have also been recovered from meat products and the environment thus illustrating the potential of MAP as pathogen of public health concern. However, at present, there is inadequate scientific evidence to confirm a conclusive link between MAP infection and Johne's disease in ruminants and some cases of Crohn's disease in human beings.

Knowledge gaps that hamper prevention and control of Mycobacterium avium subspecies paratuberculosis infection

In the last decades, many regional and country-wide control programmes for Johne's disease (JD) were developed due to associated economic losses, or because of a possible association with Crohn's disease. These control programmes were often not successful, partly because management protocols were not followed, including the introduction of infected replacement cattle, because tests to identify infected animals were unreliable, and uptake by farmers was not high enough because of a perceived low return on investment. In the absence of a cure or effective commercial vaccines, control of JD is currently primarily based on herd management strategies to avoid infection of cattle and restrict within-farm and farm-to-farm transmission. Although JD control programmes have been implemented in most developed countries, lessons learned from JD prevention and control programmes are underreported. Also, JD control programmes are typically evaluated in a limited number of herds and the duration of the study is less than 5 year, making it difficult to adequately assess the efficacy of control programmes. In this manuscript, we identify the most important gaps in knowledge hampering JD prevention and control programmes, including vaccination and diagnostics. Secondly, we discuss directions that research should take to address those knowledge gaps.

Impact of Mycobacterium avium subspecies paratuberculosis on profit efficiency in semi-extensive dairy sheep and goat farms of Apulia, southern Italy

A recent study on paratubercolosis in semi-extensive dairy sheep and goat farms in Apulia revealed a flock positivity of 60.5% and a seroprevalence of 3.0% for sheep and 14.5% for goat, with peaks of 50%. In such a context, providing detailed economic information is crucial for the implementation of a suitable control plan. In this paper we investigated the impact of Mycobacterium avium subspecies paratuberculosis (MAP) on profit efficiency of the Apulian dairy sheep and goat farms. Empirical results through a stochastic frontier model showed that the uninfected farms had a mean level of profit efficiency of 84%, which dropped to 64% in the presence of paratubercolosis as it negatively affected the productivity of feeding, veterinary and labour factors. Structural, managerial and production aspects were involved in the greater inefficiency of the infected farms compared to the uninfected ones: lower experience and schooling of farmers, no access to credit, fewer family members (women in particular) participating in the farming activities, high density of animals per hectare, small flocks, high number of goats in mixed flocks, no confinement practices for young and purchased animals and no pasture rotation. Hence, targeted interventions on these factors by decision makers can ensure effectiveness and efficiency to veterinary and economic action plans.

Short communication: Investigation into Mycobacterium avium ssp. paratuberculosis in pasteurized milk in Italy

This study investigated the presence of viable Mycobacterium avium ssp. paratuberculosis (MAP) in pasteurized milk produced by Italian industrial dairy plants to verify the prediction of a previously performed risk assessment. The study analyzed 160 one-liter bottles of pasteurized milk from 2 dairy plants located in 2 different regions. Traditional cultural protocols were applied to 500mL of pasteurized milk for each sample. The investigation focused also on the pasteurization parameters and data on the microbiological characteristics of raw milk (total bacterial count) and pasteurized milk (Enterobacteriaceae and Listeria monocytogenes). No sample was positive for MAP, the pasteurization parameters complied with European Union legislation, and the microbiological analysis of raw and pasteurized milk showed good microbiological quality. The results show that a 7-log (or >7) reduction could be a plausible value for commercial pasteurization. The combination of hygiene practices at farm level and commercial pasteurization yield very low or absent levels of MAP contamination in pasteurized milk, suggesting that pasteurized milk is not a significant source of human exposure to MAP in the dairies investigated.

Thermal Inactivation of Mycobacterium avium subsp. paratuberculosis in Artificially Contaminated Milk by Direct Steam Injection

The efficiency of direct steam injection (DSI) at 105 °C for 3 s to inactivate Mycobacterium avium subsp. paratuberculosis in milk at a pilot-plant scale was investigated. Milk samples were artificially contaminated with M. avium subsp. paratuberculosis and also with cow fecal material naturally infected with M. avium subsp. paratuberculosis. We also tested milk artificially contaminated with Mycobacterium smegmatis as a candidate surrogate to compare thermal inactivation between M. smegmatis and M. avium subsp. paratuberculosis. Following the DSI process, no viable M. avium subsp. paratuberculosis or M. smegmatis was recovered using culture methods for both strains. For pure M. avium subsp. paratuberculosis cultures, a minimum reduction of 5.6 log10 was achieved with DSI, and a minimum reduction of 5.7 log10 was found with M. smegmatis. The minimum log10 reduction for wild-type M. avium subsp. paratuberculosis naturally present in feces was 3.3. In addition, 44 dairy and nondairy powdered infant formula (PIF) ingredients used during the manufacturing process of PIF were tested for an alternate source for M. avium subsp. paratuberculosis and were found to be negative by quantitative PCR (qPCR). In conclusion, the results obtained from this study indicate that a >7-fold-log10 reduction of M. avium subsp. paratuberculosis in milk can be achieved with the applied DSI process.

IMPORTANCE

M. avium subsp. paratuberculosis is widespread in dairy herds in many countries. M. avium subsp. paratuberculosis is the causative agent of Johne's disease in cattle, and infected animals can directly or indirectly (i.e., fecal contamination) contaminate milk. Despite much research and debate, there is no conclusive evidence that M. avium subsp. paratuberculosis is a zoonotic bacterium, i.e., one that causes disease in humans. The presence of M. avium subsp. paratuberculosis or its DNA has been reported in dairy products, including pasteurized milk, cheese, and infant formula. In light of this, it is appropriate to evaluate existing mitigation measures to inactivate M. avium subsp. paratuberculosis in dairy products. The work conducted in this study describes the efficacy of direct steam injection, a thermal process commonly used in the dairy industry, to eliminate M. avium subsp. paratuberculosis and a surrogate bacterium in milk, thus ensuring the absence of M. avium subsp. paratuberculosis in dairy products subject to these process conditions.

INFLUÊNCIA DA GORDURA DO LEITE BOVINO E CAPRINO NA RESISTÊNCIA DOMycobacterium fortuitum À PASTEURIZAÇÃO LENTA

Resumo Este estudo objetivou mostrar o efeito da gordura do leite caprino e bovino sobre a resistência térmica do Mycobacterium fortuitum. Amostras de leite foram divididas em duas porções, integral e desnatada, cada porção foi inoculada com M. fortuitum e então distribuída em tubos para a quantificação do agente durante a pasteurização lenta, em banho-maria. As amostras foram diluídas e semeadas em Lowenstein-Jensen (37 °C/5 dias), os resultados da contagem foram expressos em Log10 UFC/mL. O tratamento térmico reduziu 4,4 Log10 UFC/mL no leite caprino integral (2,8% de gordura), 4,9 Log10 UFC/mL no leite caprino desnatado (0,3%), 3,9 Log10 UFC/mL no leite bovino integral (5,9%) e 5,4 Log10 UFC/mL no leite bovino desnatado (0,2%), sem diferença significante, possivelmente pelo baixo número de amostras. Os valores D65 °C foram, respectivamente, 10,51 minutos, 8,61 minutos, 18,02 minutos e 7,82 minutos e o valor de R2 baixo das equações da reta indicam que outros fatores, além dos que foram estudados, influenciam a morte térmica do agente. Os resultados sugerem uma tendência de influência da gordura do leite e também da espécie animal sobre a taxa de decaimento do M. fortuitum, sendo que a pasteurização foi menos eficaz sobre oM. fortuitum no leite bovino integral.

Crohn's disease and the mycobacterioses: a quarter century later. Causation or simple association?

It has been more than 25 years since Mycobacterium paratuberculosis was first proposed as an etiologic agent in Crohn's disease based on the isolation of this organism from several patients. Since that time, a great deal of information has been accumulated that clearly establishes an association between M. paratuberculosis and Crohn's disease. However, data are conflicting and difficult to interpret and the field has become divided into committed advocates and confirmed skeptics. This review is an attempt to provide a thorough and objective summary of current knowledge from both basic and clinical research from the views and interpretations of both the antagonists and proponents. The reader is left to draw his or her own conclusions related to the validity of the issues and claims made by the opposing views and data interpretations. Whether M. paratuberculosis is a causative agent in some cases or simply represents an incidental association remains a controversial topic, but current evidence suggests that the notion should not be so readily dismissed. Remaining questions that need to be addressed in defining the role of M. paratuberculosis in Crohn's disease and future implications are discussed.

Modeling the occurrence of Mycobacterium avium subsp. paratuberculosis in bulk raw milk and the impact of management options for exposure mitigation

Mycobacterium avium subsp. paratuberculosis (MAP) is the causal agent of paratuberculosis (Johne's disease) in cattle and other farm ruminants. The potential role of MAP in Crohn's disease in humans and the contribution of dairy products to human exposure to MAP continue to be the subject of scientific debate. The occurrence of MAP in bulk raw milk from dairy herds was assessed using a stochastic modeling approach. Raw milk samples were collected from bulk tanks in dairy plants and tested for the presence of MAP. Results from this analytical screening were used in a Bayesian network to update the model prediction. Of the 83 raw milk samples tested, 4 were positive for MAP by culture and PCR. We estimated that the level of MAP in bulk tanks ranged from 0 CFU/ml for the 2.5th percentile to 65 CFU/ml for the 97.5th percentile, with 95% credibility intervals of [0, 0] and [16, 326], respectively. The model was used to evaluate the effect of measures aimed at reducing the occurrence of MAP in raw milk. Reducing the prevalence of paratuberculosis has less of an effect on the occurrence of MAP in bulk raw milk than does managing clinically infected animals through good farming practices.

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.

Advanced methods for the elimination of microorganisms in industrial treatments: potential applicability to wastewater reuse

Because of the growing need to eliminate undesirable microorganisms in different industrial treatments, mainly in the food and agricultural sector and the pharmaceutical industry, a number of increasingly effective systems for disinfection to eliminate microorganisms have been devised. This article analyzes different methods to eliminate and/or significantly reduce the number of microorganisms in industrial contexts and in environmental engineering. Although, in the past, thermal treatments had been used most frequently for microbial elimination, the method is costly and has the disadvantage of modifying the organoleptic and/or physicochemical properties of the food products. For this reason, new technologies rapidly are being developed, such as high-intensity pulsed electric fields, high-pressure systems, ultrasounds, and irradiation, which effectively eliminate microorganisms without deteriorating the properties of the product. These emerging technologies are potentially applicable in the field of environmental engineering.

Current perspectives on Mycobacterium avium subsp. paratuberculosis, Johne's disease, and Crohn's disease: a review

Mycobacterium avium subsp. paratuberculosis (MAP) causes the disease of cattle, Johne's. The economic impact of this disease includes early culling of infected cattle, reduced milk yield, and weight loss of cattle sold for slaughter. There is a possible link between MAP and Crohn's disease, a human inflammatory bowel disease. MAP is also a potential human food borne pathogen because it survives current pasteurization treatments. We review the current knowledge of MAP, Johne's disease and Crohn's disease and note directions for future work with this organism including rapid and economical detection, effective management plans and preventative measures.

Ulcerative colitis and Crohn's disease: is Mycobacterium avium subspecies paratuberculosis the common villain?

Mycobacterium avium, subspecies paratuberculosis (MAP) causes a chronic disease of the intestines in dairy cows and a wide range of other animals, including nonhuman primates, called Johne's ("Yo-knee's") disease. MAP has been consistently identified by a variety of techniques in humans with Crohn's disease. The research investigating the presence of MAP in patients with Crohn's disease has often identified MAP in the "negative" ulcerative colitis controls as well, suggesting that ulcerative colitis is also caused by MAP. Like other infectious diseases, dose, route of infection, age, sex and genes influence whether an individual infected with MAP develops ulcerative colitis or Crohn's disease. The apparently opposite role of smoking, increasing the risk of Crohn's disease while decreasing the risk of ulcerative colitis, is explained by a more careful review of the literature that reveals smoking causes an increase in both diseases but switches the phenotype from ulcerative colitis to Crohn's disease. MAP as the sole etiologic agent of both ulcerative colitis and Crohn's disease explains their common epidemiology, geographic distribution and familial and sporadic clusters, providing a unified hypothesis for the prevention and cure of the no longer "idiopathic" inflammatory bowel diseases.

Debugging the intestinal microbiota in IBD

Besides its role in repelling enteropathogenic infections, the gastrointestinal tract is in intimate contact with commensal microbiota. Tremendous advances have been made in determining the pivotal role of the microbiota in both tissue homeostasis and metabolism, as well as in the initiation and maintenance of inflammatory lesions in inflammatory bowel diseases. A better understanding of human gut microbiota could provide innovative targets for treating and/or curing such common immunopathologies of the gastrointestinal tract.

Impact of lactose containing foods and the genetics of lactase on diseases: an analytical review of population data

Dairy foods (DFs) contain complex ingredients that could affect different diseases. The control of lactose digestion phenotypically divides populations into those who can [lactase persistent (LP)] and those who cannot [lactase nonpersistent (LNP)] assimilate lactose. LNP subjects, however, can adapt to lactose intolerance through intestinal bacteria. The DF/LNP status interactions may function as disease risk modifiers. We evaluated the relationship between DF and LNP with colorectal, breast, prostate, ovarian, lung, and stomach cancer and inflammatory bowel diseases (IBD; Crohn's disease and ulcerative colitis). Yearly per capita DF consumption, LNP national prevalence, cancer mortality, and incidence of IBD were obtained from several sources. A negative binomial regression model was used to derive incremental risks. There were statistically significant (P <or= 0.05) increases in risk for colorectal and prostate cancer and ulcerative colitis with DFs and a statistically significant decreased risk for stomach cancer. There were trends (P<0.1) for lung and ovarian cancers and Crohn's disease. As LNP prevalence increased, stomach cancer risk increased, whereas risks of all other conditions decreased (P<0.01). In 3 cancers (prostate, ovarian, and breast), meta-analyses of case-based studies support ecological data. In colorectal cancer, on the contrary, meta-analyses of case-based studies suggest protection. The possible importance of distinguishing LNP/LP status in studies is discussed.

Effective heat inactivation of Mycobacterium avium subsp. paratuberculosis in raw milk contaminated with naturally infected feces

The effectiveness of high-temperature, short holding time (HTST) pasteurization and homogenization with respect to inactivation of Mycobacterium avium subsp. paratuberculosis was evaluated quantitatively. This allowed a detailed determination of inactivation kinetics. High concentrations of feces from cows with clinical symptoms of Johne's disease were used to contaminate raw milk in order to realistically mimic possible incidents most closely. Final M. avium subsp. paratuberculosis concentrations varying from 10(2) to 3.5 x 10(5) cells per ml raw milk were used. Heat treatments including industrial HTST were simulated on a pilot scale with 22 different time-temperature combinations, including 60 to 90 degrees C at holding (mean residence) times of 6 to 15 s. Following 72 degrees C and a holding time of 6 s, 70 degrees C for 10 and 15 s, or under more stringent conditions, no viable M. avium subsp. paratuberculosis cells were recovered, resulting in >4.2- to >7.1-fold reductions, depending on the original inoculum concentrations. Inactivation kinetic modeling of 69 quantitative data points yielded an E(a) of 305,635 J/mol and an lnk(0) of 107.2, corresponding to a D value of 1.2 s at 72 degrees C and a Z value of 7.7 degrees C. Homogenization did not significantly affect the inactivation. The conclusion can be drawn that HTST pasteurization conditions equal to 15 s at > or =72 degrees C result in a more-than-sevenfold reduction of M. avium subsp. paratuberculosis.

Bacteria in Crohn's disease: mechanisms of inflammation and therapeutic implications

Microbial agents are implicated in each of the most prevalent etiologic hypotheses of Crohn's disease. Although chronic infection with a specific, persistent pathogen cannot be excluded, it is more likely that Crohn's disease is caused by an overly aggressive immune response to normal commensal enteric bacteria. The complex, predominantly anaerobic microbiota in the distal ileum and colon provide a constant source of antigens and adjuvants that stimulate chronic immune-mediated inflammation in genetically susceptible hosts. Host genetic susceptibility in the form of defective mucosal barrier function, bacterial killing or processing can lead to enhanced exposure to luminal bacteria and their immunologically active components, whereas defective immunoregulation can lead to lack of appropriate immunosuppression. Either process can lead to overly aggressive T-cell responses to normal bacteria that causes tissue damage. Transient infection with pathogenic organisms could serve as environmental triggers to initiate inflammatory responses that are perpetuated in susceptible hosts by commensal microbial antigens. In addition, commensal bacteria such as Escherichia coli recovered from the ileum of patients with recurrent Crohn's disease after resection can contain virulence factors that mediate epithelial attachment, invasion, and resistance to killing. Finally, Western diet, antibiotic use, hygiene, and public health practices may have altered the balance of beneficial versus aggressive microbial species. Crohn's disease patients exhibit enhanced humoral and T-cell responses to common commensal bacterial and fungal antigens. These observations may help identify clinically relevant patient subsets and suggest novel therapeutic approaches to restore a beneficial balance of enteric microbiota, enhanced microbial killing, and inhibit aggressive T-cell responses to microbial antigens.

Mechanisms of disease: pathogenesis of Crohn's disease and ulcerative colitis

Crohn's disease and ulcerative colitis are idiopathic, chronic, relapsing, inflammatory conditions that are immunologically mediated. Although their exact etiologies remain uncertain, results from research in animal models, human genetics, basic science and clinical trials have provided important new insights into the pathogenesis of chronic, immune-mediated, intestinal inflammation. These studies indicate that Crohn's disease and ulcerative colitis are heterogeneous diseases characterized by various genetic abnormalities that lead to overly aggressive T-cell responses to a subset of commensal enteric bacteria. The onset and reactivation of disease are triggered by environmental factors that transiently break the mucosal barrier, stimulate immune responses or alter the balance between beneficial and pathogenic enteric bacteria. Different genetic abnormalities can lead to similar disease phenotypes; these genetic changes can be broadly characterized as causing defects in mucosal barrier function, immunoregulation or bacterial clearance. These new insights will help develop better diagnostic approaches that identify clinically important subsets of patients for whom the natural history of disease and response to treatment are predictable.

Inactivation of Mycobacterium avium subsp. paratuberculosis in cow's milk by means of high hydrostatic pressure at mild temperatures

Two strains of Mycobacterium avium subsp. paratuberculosis (3644/02 and ATCC 19698) were inoculated (approximately 6 log CFU/ml) into sterilized milk to evaluate inactivation by high hydrostatic pressure. Reductions of M. avium subsp. paratuberculosis increased with pressure level. Significant differences were also found between M. avium subsp. paratuberculosis strains and between the media used. Average reductions of 4 log CFU/ml after treatment with 500 MPa are comparable to those caused by thermal treatments.

Real-time PCR-based methods for detection of Mycobacterium avium subsp. paratuberculosis in water and milk

A real-time PCR assay for quantitative detection of Mycobacterium avium paratuberculosis has been developed. It targets and amplifies sequences from the IS900 insertion element which is specific for this bacterium, and includes an internal amplification control. The assay was tested against 18 isolates of M. avium paratuberculosis, 17 other mycobacterial strains, and 25 non-mycobacterial strains, and was fully selective. It is capable of detecting <3 genomic DNA copies with 99% probability or alternatively, using cells directly in the reaction, 12 cells can be detected with 99% probability. Using prior centrifugation, the assay was able to consistently and quantifiably detect 10(2) M. avium paratuberculosis cells in 20 ml artificially contaminated drinking water. With a simple detergent and enzymatic sample pretreatment before centrifugation and nucleic acid extraction, the assay was able to consistently detect 10(2) M. avium paratuberculosis in 20 ml artificially contaminated semi-skimmed milk. The assay will be a useful addition to the range of diagnostic tools available for the study of M. avium paratuberculosis.

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.

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

Acid resistance of Mycobacterium paratuberculosis was examined as a function of growth conditions (i.e., in vitro growth medium and pH). M. paratuberculosis was cultured in either fatty acid-containing medium (7H9-OADC) or glycerol-containing medium (WR-GD or 7H9-GD) at two culture pHs (pHs 6.0 and 6.8). Organisms produced in these six medium and pH conditions were then tested for resistance to acetate buffer at pHs 3, 4, 5, and 6 at 20 degrees C. A radiometric culture method (BACTEC) was used to quantify viable M. paratuberculosis cell data at various acid exposure times, and D values (decimal reduction times, or the times required to kill a 1-log(10) concentration of bacteria) were determined. Soluble proteins of M. paratuberculosis grown under all six conditions were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) to identify proteins that may be associated with acid resistance or susceptibility. The culture medium affected growth rate and morphology: thin floating sheets of cells were observed in 7H9-OADC versus confluent, thick, waxy, and wrinkled pellicles in WR-GD. Culture medium pH affected growth rate (which was highest at pH 6.0), but it had little or no effect on D values for M. paratuberculosis at any test pH. When grown in 7H9-OADC, M. paratuberculosis was more acid resistant at all test pHs (higher D values) than when grown in WR-GD. Glycerol appeared to be the culture medium component most responsible for lower levels of M. paratuberculosis acid resistance. When glycerol was substituted for OADC in the 7H9 medium, D values were significantly lower than those of 7H9-OADC-grown M. paratuberculosis and were approximately the same as those for M. paratuberculosis grown in WR-GD medium. Comparison of the SDS-PAGE protein profiles for M. paratuberculosis cultures grown in 7H9-OADC, WR-GD, or 7H9-GD medium revealed that increased expression of 34.2- and 14.0-kDa proteins was associated with higher levels of acid resistance of M. paratuberculosis grown in 7H9-OADC medium and that 56.6- and 41.3-kDa proteins were associated with lower levels of acid resistance. This is the first report showing that in vitro culture conditions significantly affect growth characteristics, acid resistance, and protein expression of M. paratuberculosis, and the results emphasize the importance of culture conditions for in vitro susceptibility studies.

Targeting enteric bacteria in treatment of inflammatory bowel diseases: why, how, and when

PURPOSE

This review discusses the role of bacterial adjuvants and antigens in induction and reactivation of chronic intestinal inflammation in susceptible hosts; discusses the results of recent therapeutic trials of antibiotics, probiotics, and prebiotics; and suggests future treatment strategies.

RECENT FINDINGS

Bacterial adjuvants, including peptidoglycan, lipopolysaccharide, and DNA (CpG) bind to membrane-bound toll-like receptors (TLR-2, 4, and 9. respectively) or cytoplasmic (NOD1 and NOD2) receptors (pattern recognition receptors) that activate nuclear factor-kappaB and transcription of many proinflammatory cytokines and adhesion, costimulatory, and major histocompatibility complex class II molecules. Experimental enterocolitis does not occur in a sterile (germ-free) environment and is prevented and treated by broad-spectrum antibiotics. Individual nonpathogenic intestinal bacterial species selectively induce experimental colitis, with host specificity. Crohn disease and ulcerative colitis patients exhibit pathogenic immune responses (loss of immunologic tolerance) to multiple normal enteric bacterial species and serologic responses to Mycobacterium paratuberculosis. Metronidazole and ciprofloxacin selectively treat colonic Crohn disease, but not ulcerative colitis or ileal Crohn disease, and may prevent recurrence of postoperative Crohn disease. Certain probiotic species decrease relapse of ulcerative colitis and chronic pouchitis and delay onset of pouchitis.

SUMMARY

Normal, nonpathogenic enteric bacteria induce and perpetuate chronic intestinal inflammation in genetically susceptible hosts with defective immunoregulation, bacterial clearance, or mucosal barrier function. Altering the composition and decreasing mucosal adherence/invasion of commensal bacteria with antibiotics, probiotics, and prebiotics can potentially prevent and treat Crohn disease, pouchitis, and possibly ulcerative colitis, but optimal treatments have not yet been identified.

The genetics of nontuberculous mycobacterial infection

The molecular aetiology of familial susceptibility to disseminated mycobacterial disease, usually involving weakly pathogenic strains of mycobacteria, has now been elucidated in more than 30 families. Mutations have been identified in five genes in the interleukin-12-dependent interferon-gamma pathway, highlighting the importance of this pathway in human mycobacterial immunity. Knowledge derived from the study of these rare patients contributes to our understanding of the immune response to common mycobacterial pathogens such as Mycobacterium tuberculosis and Mycobacterium leprae, which remain major public health problems globally. This knowledge can be applied to the rational development of novel therapies and vaccines for these important mycobacterial diseases.