Résumés d’articles scientifiques

Pig farming is a risk factor for increased nasal S. aureus colonization. Using sequence typing, researchers found a few bacterial strains that were not present in non-farmers but often caused swine infections. The finding suggested a high rate of strain exchange between pigs and farmers.

Samples were taken from 36 farmers' markets in 2007. E. coli was isolated from 8.2% of samples that included lettuce, spinach, carrots and green onions. The bacterial counts ranged from <0.48 to >3.04 log MPN per gram. E. coli was not isolated from tomatoes or strawberries. The percentage of positive samples ranged from 4.4% for carrots to 27.1% for spinach. Cryptosporidium was identified by PCR in one sample of spinach.

Researchers concluded that climate change is likely to increase human exposures to agricultural contaminants. Climate change is anticipated to fuel increased use of pesticides and biocides as farming practices intensify. The magnitude of the increases will be highly dependent on the contaminant type. The potential for source variance arising from behavioral response (intensification of management and altered patterns of chemical and manure use) will also be compounding factors. Risks from many pathogens and particulate and particle-associated contaminants could increase significantly.

Air within a concentrated swine feeding operation were sampled. A total of 137 presumptive Enterococcus isolates were identified. 34% of the isolates were confirmed as Enterococcus, 32% as coagulase-negative Staphylococci and 33% as viridans group streptococci. Regardless of the species, 98% of the isolates expressed high-level resistance to at least two antibiotics commonly used in swine production. The findings suggested that the inhalation of air from these facilities may serve as an exposure pathway for the transfer of multidrug-resistant bacterial pathogens from swine to humans.

Samples were collected from organic and conventional farms and county fairs in Minnesota. E. coli O157 was isolated from 5.2% of fecal samples from 36.8% of farms in 2001 and 4.5% from 23.5% of farms in 2002. 11% of fecal samples were positive from 75% of county fairs. Data suggested that county fairs have the potential for transmission of E. coli O157 to the public.

Most emerging infectious diseases are zoonotic; wildlife constitutes a large and often unknown reservoir. The leading causes of their emergence are human behaviour and modifications to natural habitats (expansion of human populations and their encroachment on wildlife habitat), changes in agricultural practices and globalization of trade. Other factors include wildlife trade and translocation, live animal and bushmeat markets, consumption of exotic foods, development of ecotourism, access to petting zoos and ownership of exotic pets.

An exponential decrease of E. coli populations was observed in surface soil after the application of manure. The estimated average time required to reach undetectable concentrations of E. coli in sandy loam varied from 56 to 70 days, whereas the absence of E. coli was estimated at 77 days in loamy sand. The maximal Salmonella persistence in soil was 54 days.

Antimicrobial resistant E. coli were found in sewage effluent. Resistance rates of E. coli in nearly all of the tested antibiotics were higher in the strains obtained from the slaughterhouses that handled conventional broilers than in those that handled free-range broilers. Wastewater treatment resulted in a 0.5 to 3-log decrease in E. coli but 105 cfu/100 mL were present in the outflow of the plant.

Up to 7000 Giardia cysts and 762 Cryptosporidium oocysts per litre were detected in reclaimed wastewater. Sheep were grazing on forage irrigated with reclaimed wastewater. The pathogens were rarely found on forage plants when the wastewater was used for irrigation, possibly due to environmental attenuation.

Rectal and environmental samples were collected from 16 farms over 24 months. E. coli O157:H7 was found in 3.6% of beef cattle, 3.4% of dairy cattle, 0.9% of chicken, 7.5% of turkey, and 8.9% of swine samples. The pathogen was isolated sporadically from each of the environmental sample types. E. coli was also isolated from fresh feed samples, indicating a potential vector for transmission. The data indicated a high occurrence of E. coli on swine and turkey farms.