Évaluation des sources d’exposition à Mycobacterium avium subsp. paratuberculosis dans les aliments et l’eau

Mycobacterium avium subsp. paratuberculosis (MAP) is believed to be the causative agent of paratuberculosis (Johne’s disease) in ruminants. MAP infection has also been proposed as the cause of Crohn’s disease (CD) in humans. An increasing number of recent studies suggest some association between MAP and CD, however a cause‐effect relationship has yet to be proved or disproved. Infected cattle appear to be the most important source of human exposure to MAP, and the associated suspected vehicles of transmission are milk, dairy products and beef.   Other possible routes of human exposure to MAP are via contaminated water supplies, vegetables and fruits. A low level survival of MAP has been demonstrated in some surveys of commercially pasteurized milk and retail cheese in several countries outside Canada. Viable MAP has been identified in 1.6‐2.9% of pasteurized retail milk and 3.6% of retail cheese samples in several countries. In addition, viable MAP has been found in the intestine and associated lymph tissues of diseased animals as well as in organs other than the gut. The primary purpose of this article is to review the recent scientific evidence on the potential human exposure to MAP via foods and waterOn croit que Mycobacterium avium subsp. paratuberculosis (MAP) est l’agent causal de la paratuberculose (maladie de Johne) chez les ruminants. L’infection par MAP pourrait aussi être en cause dans la maladie de Crohn (MC) chez les humains. Bien qu’un lien de cause à effet doive toujours être démontré ou réfuté, un nombre croissant d’études récentes donnent à penser qu’il existe un lien entre MAP et la MC. Il semble que les bovins infectés, de même que les vecteurs de transmission connexes soupçonnés tels que le lait, les produits laitiers et le bœuf, constituent la principale source d’exposition à MAP chez les humains. L’approvisionnement en eau ainsi que les légumes et les fruits contaminés par MAP sont d’autres voies d’exposition éventuelles à la bactérie chez les humains.   Lors de certaines études sur le lait pasteurisé et les fromages vendus au détail réalisées dans plusieurs pays autres que le Canada, un faible taux de survie de MAP a été démontré. Dans de nombreux autres pays, la prévalence de cellules viables de MAP a été établie à 1,6 à 2,9 % dans des échantillons de lait pasteurisé et à 3,6 % dans des fromages vendus au détail. En outre, MAP viable    a été découverte dans l’intestin et les tissus lymphoïdes associés d’animaux malades, de même que dans des organes autres que l’intestin. Le principal objectif du présent article consiste à examiner les observations scientifiques récentes sur l’exposition potentielle à MAP par les aliments et l’eau chez les humains

Dysregulation of Cytokine Response in Canadian First Nations Communities: Is There an Association with Persistent Organic Pollutant Levels?

In vitro and animal studies report that some persistent organic pollutants (POPs) trigger the secretion of proinflammatory cytokines. Whether POP exposure is associated with a dysregulation of cytokine response remains to be investigated in humans. We studied the strength of association between plasma POP levels and circulating cytokines as immune activation markers. Plasma levels of fourteen POPs and thirteen cytokines were measured in 39 Caucasians from a comparator sample in Québec City (Canada) and 72 First Nations individuals from two northern communities of Ontario (Canada). Caucasians showed significantly higher levels of organochlorine insecticides (β-HCH, p,p′-DDE and HCB) compared to First Nations. Conversely, First Nations showed higher levels of Mirex, Aroclor 1260, PCB 153, PCB 170, PCB 180 and PCB 187 compared to Caucasians. While there was no difference in cytokine levels of IL-4, IL-6, IL-10 and IL-22 between groups, First Nations had significantly greater average levels of IFNγ, IL-1β, IL-2, IL-5, IL-8, IL-12p70, IL-17A, TNFα and TNFβ levels compared to Caucasians. Among candidate predictor variables (age, body mass index, insulin resistance and POP levels), high levels of PCBs were the only predictor accounting for a small but significant effect of observed variance (∼7%) in cytokine levels. Overall, a weak but significant association is detected between persistent organochlorine pollutant exposure and elevated cytokine levels. This finding augments the already existing information that environmental pollution is related to inflammation, a common feature of several metabolic disorders that are known to be especially prevalent in Canada's remote First Nations communities

Application of a Quantitative Carrier Test to Evaluate Microbicides against Mycobacteria

Abstract Microbicides for reprocessing heat-sensitive medical devices, such as flexible endoscopes, must be mycobactericidal to reduce the risk of nosocomial infections. Suspension test methods currently used for efficacy evaluation lack the stringency required for assessing inactivation of mycobacteria on surfaces. The quantitative carrier test method reported here is based on mycobacteria-contaminated reference carrier disks of brushed stainless steel. Each disk was contaminated with 10 L of a suspension of Mycobacterium terrae containing a soil load. Each disk with a dried inoculum was placed in a glass or Teflon vial, and then overlaid with 50 L of the test formulation or 50 L saline for the control carriers. Five test and 3 control disks were used in each run. At the end of the contact time, each vial received 9.95 mL neutralizer solution with 0.1% Tween-80 to stop the reaction and perform the initial microbicide dilution. The inoculum was eluted by mixing on a Vortex mixer for 60 s, and the eluates and saline used to subsequently wash the vials and the funnels were membrane-filtered. Filters were placed on plates of Middlebrook 7H11 agar and incubated at 37C for at least 30 days before colonies were counted and log10 reductions were calculated in colony-forming units. Tests with a range of commercially available products, having claims against mycobacteria, or believed to be broad-spectrum microbicides, showed that the method gave reproducible results. Products used included oxidizing agents (sodium hypochlorite and an iodophore), a phenolic, a quaternary ammonium compound, and ortho-phthalaldehyde. This method represents a much more realistic evaluation than the currently used quantitative suspension test method for the evaluation of mycobactericidal formulations for registration and, when performed at different product concentrations, allows an assessment of any safety margin or risks in using the test formulation in the field.</jats:p

Fate of<i>Cryptosporidium</i>oocysts,<i>Giardia</i>cysts, and microbial indicators during wastewater treatment and anaerobic sludge digestion

The extent of reduction in selected microorganisms was tested during both aerobic wastewater treatment and anaerobic digestion of sludge at the wastewater treatment plant in Ottawa to compare the removal of two encysted pathogenic protozoa with that of microbial indicators. Samples collected included the raw wastewater, the primary effluent, the treated wastewater, the mixed sludge, the decanted liquor, and the cake. All of the raw sewage samples were positive for Cryptosporidium oocysts and Giardia cysts, as well as for the other microorganisms tested. During aerobic wastewater treatment (excluding the anaerobic sludge digestion), Cryptosporidium and Giardia were reduced by 2.96 log10and 1.40 log10, respectively. Clostridium perfringens spores, Clostridium perfringens total counts, somatic coliphages, and heterotrophic bacteria were reduced by approximately 0.89 log10, 0.96 log10, 1.58 log10, and 2.02 log10, respectively. All of the other microorganisms were reduced by at least 3.53 log10. Sludge samples from the plant were found to contain variable densities of microorganisms. Variability in microbial concentrations was sometimes great between samples, stressing the importance of collecting a large number of samples over a long period of time. In all cases, the bacterial concentrations in the cake (dewatered biosolids) samples were high even if reductions in numbers were observed with some bacteria. During anaerobic sludge digestion, no statistically significant reduction was observed for Clostridium perfringens, Enterococcus sp., Cryptosporidium oocysts, and Giardia cysts. A 1-2 log10reduction was observed with fecal coliforms and heterotrophic bacteria. However, the method utilized to detect the protozoan parasites does not differentiate between viable and nonviable organisms. On the other hand, total coliforms and somatic coliphages were reduced by 0.35 log10and 0.09 log10, respectively. These results demonstrate the relative persistence of the protozoa in sewage sludge during wastewater treatment.Key words: Cryptosporidium, Giardia, indicators, wastewater, sludge.</jats:p