To evaluate correlations between antimicrobial use and the prevalence of resistance in commensal Escherichia coli isolates from pigs, poultry and cattle, using data from publicly available national or international reports from seven European countries. The link between the quantities of different classes of antimicrobials administered to food-producing animals per country (expressed in mg/population correction unit) and the prevalence of resistance to the different antimicrobial classes (interpreted by EUCAST epidemiological cut-off values) in E. coli isolates (4831 isolates in total) was assessed by means of polynomial regression analysis and determination of Spearman's rank correlation coefficient. A quadratic regression best fitted the antimicrobial use and antimicrobial resistance data. The coefficient of determination was, in decreasing order, 0.99 for fluoroquinolones and amphenicols, 0.94 for third-generation cephalosporins and sulphonamides, 0.93 for aminopenicillins, 0.86 for fluoroquinolones, 0.81 for streptomycin and 0.80 for gentamicin and tetracycline. Spearman's rank correlation coefficient was 1 for amphenicols, 0.96 for sulphonamides, 0.93 for streptomycin and tetracycline, 0.89 for aminopenicillins, 0.71 for gentamicin and 0.70 for third-generation cephalosporins. These remarkably high coefficients indicate that, at a national level, the level of use of specific antimicrobials strongly correlates to the level of resistance towards these agents in commensal E. coli isolates in pigs, poultry and cattle. However, data restraints reveal the need for further detail in collection and harmonization of antimicrobial resistance and use data in Europe.

Short-chain fatty acids have been widely used as feed additives to control Salmonella in poultry. Data on the use of butyric acid in poultry are lacking. In this study, powder form and coated butyric acid were compared in their ability to reduce Salmonella colonization of ceca and internal organs shortly after infection of young chickens with Salmonella enteritidis. In the first trial, 4 groups of 25 specific pathogen free layer chickens were given feed either supplemented with powder form butyric acid, coated butyric acid, a combination of powder form and coated butyric acid (all groups received a total of 0.63 g of butyric acid/kg) or nonsupplemented feed. The specific pathogen free layer chickens were orally infected with 10(6) cfu of S. enteritidis. Coated butyric acid significantly decreased cecal colonization 3 d post-infection compared with control chickens, and powder form butyric acid had no effect. To study long-term shedding and colonization of Salmonella in broilers given coated butyric acid as feed additive (0.63 g of active product butyric acid/kg), 10 Ross broiler chickens were infected at d 5 with 10(5) cfu of S. enteritidis and housed together with 40 noninfected broilers. A control group received nonsupplemented feed. The group of broilers receiving coated butyric acid had a significantly lower number of broilers shedding Salmonella bacteria, but cecal colonization at slaughter age was equal for both groups. In conclusion, butyric acid decreases cecal colonization shortly after infection, decreases fecal shedding, and as a consequence, decreases environmental contamination by S. enteritidis-infected broilers. However, complete elimination can probably only be achieved with a combined approach using both hygienic measures and different protection measures, as the broilers still carried S. enteritidis bacteria in the ceca at slaughter age, although at enrichment level.

The most common source of Salmonella infections in humans is food of poultry origin. Salmonella enterica serovar Enteritidis has a particular affinity for the contamination of the egg supply. In this study, the medium-chain fatty acids (MCFA), caproic, caprylic, and capric acid, were evaluated for the control of Salmonella serovar Enteritidis in chickens. All MCFA were growth inhibiting at low concentrations in vitro, with caproic acid being the most potent. Contact of Salmonella serovar Enteritidis with low concentrations of MCFA decreased invasion in the intestinal epithelial cell line T84. By using transcriptional fusions between the promoter of the regulatory gene of the Salmonella pathogenicity island I, hilA , and luxCDABE genes, it was shown that all MCFA decreased the expression of hilA , a key regulator related to the invasive capacity of Salmonella . The addition of caproic acid (3 g/kg of feed) to the feed of chicks led to a significant decrease in the level of colonization of ceca and internal organs by Salmonella serovar Enteritidis at 3 days after infection of 5-day-old chicks. These results suggest that MCFA have a synergistic ability to suppress the expression of the genes required for invasion and to reduce the numbers of bacteria in vivo. Thus, MCFA are potentially useful products for reducing the level of colonization of chicks and could ultimately aid in the reduction of the number of contaminated eggs in the food supply.