Enterotoxigenic Escherichia coli (ETEC: F4) associated with post-weaning diarrhea (PWD) in pigs has developed resistance against several antimicrobial families, leading to increased use of colistin sulfate (CS) for the treatment of this disease. The objective of this study was to determine the efficacy of oral CS treatment in experimental PWD due to ETEC: F4 challenge and determine the effect of this challenge on CS intestinal absorption. In this study, 96 pigs were divided into two trials based on CS dose (100 000 or 50 000 IU/kg). Fecal shedding of ETEC: F4, total E. coli, and CS-resistant E. coli, diarrhea scores, and weight changes were evaluated. Colistin sulfate plasma concentrations were determined by HPLC–MS/MS. Regardless of the dose, CS treatment resulted in a reduction of fecal ETEC: F4 and total E. coli shedding, and in diarrhea scores but only during the treatment period. However, CS treatment resulted in a slight increase in fecal shedding of CS resistant E. coli and did not prevent weight loss in challenged pigs. In addition, challenge with ETEC: F4 resulted in an increase of CS intestinal absorption. Our study is among the first to demonstrate that under controlled conditions, CS was effective in reducing fecal shedding of ETEC: F4 and total E. coli in experimental PWD. However, CS treatment was associated with a slight selection pressure on E. coli and did not prevent pig weight loss. Further studies are needed in field conditions, to better characterize CS therapeutic regimen efficacy and bacterial resistance dissemination.Electronic supplementary materialThe online version of this article (doi:10.1186/s13567-016-0344-y) contains supplementary material, which is available to authorized users.

The aim of the present study was to investigate the in vitro gastric stability of colistin sulfate (CS) and its antimicrobial activity against Escherichia coli and to study the impact of ETEC O149: F4 (K88) infection in pigs on CS intestinal absorption. The stability profile of CS was evaluated in a simulated gastric fluid (SGF). Antimicrobial activity of CS and its degradation products were examined in a 96-well polystyrene microplate model. The effect of experimental infection with ETEC O149: F4 on CS intestinal absorption was determined by quantification of CS systemic concentration using a validated LC-MS/MS method. A rapid degradation of CS accompanied by an increase in CS antimicrobial activity by comparison with non-degraded CS (P<0.0001) was observed in SGF. Additionally, CS levels were not quantifiable in systemic circulation using a highly sensitive method and concurrent oral challenge did not affect CS absorption in an induction model of subclinical post-weaning diarrhea (PWD).

Although supplementing the diet with zinc oxide and arginine is known to improve growth in weanling piglets, the mechanism of action is not well understood. We measured the antioxidant status and inflammatory response in 48 weanling castrated male piglets fed diets supplemented with or without zinc oxide (2,500 mg Zn oxide per kg) and arginine (1%) starting at the age of 20 days. The animals were injected with lipopolysaccharide (100 μg/kg) on day 5. Half of them received another injection on day 12. Blood samples were taken just before and 6, 24 and 48 h after injection and the mucosa lining the ileum was recovered following euthanizing on days 7 and 14. Zinc supplementation increased reduced and total glutathione (GSH) (reduced and total) during days 5 to 7 and arginine decreased oxidized GSH measured on days 5 and 12 and the ratio of total antioxidant capacity to total oxidative status during days 12 to 14. Zinc decreased plasma malondialdehyde measured on days 5 and 12 and serum haptoglobin measured on day 12 and increased both metallothionein-1 expression and total antioxidant capacity measured in the ileal mucosa on day 14. Tumour necrosis factor α concentration decreased from days 5 to 12 (all effects were significant at P < 0.05). This study shows that the zinc supplement reduced lipid oxidation and lipopolysaccharide-induced inflammation during the post-weaning period, while the arginine supplementation had only a limited effect.

In th1s study we characterized, usmg genotyping and phenotypmg methods, ISolates {n=33) from septicaemia outbreaks in swine herds as well as isolates {n=33) recovered from healthy ammals at slaughter. We determined the antimicrobial agents resistance profiles using 24 different an timicrobial agents by the d1sk d1ffus1on on agar method, the phage type, the plasmid profiles and the PFGE profiles usmg Xbal and Spel as restriction enzymes for each isolates. Resistance to as much as 10 antimicrobial agents was found in both categories of isolates. A greater number of PFGE genotypes was observed in isolates from septicaemia. Various phage types were 1dent1fied in both groups of isolates. Among the DT1 04 phage type, many genetic clusters were 1dent1fied Analysis of plasmid profiles indicated that septicemic strains possess higher molecular we1ght plasmids than asymptomatic 1solates. These results Indicated that strams associated w1th sept1caem1a belong to various genet1c lineages and suggest that VIrulence tra1ts are assoc1ated w1th plasmid profiles of stra1ns. Our results also suggest that the genetic d1vers1ty of Salmonella DT 104 m1ght be higher m North Amenca if we cons1der results of s1milar studies m Europe

BackgroundEnterotoxigenic Escherichia coli (ETEC) strains producing multiple enterotoxins are important causes of post-weaning diarrhea (PWD) in pigs. The aim of the present study was to investigate the fecal presence of ETEC enterotoxin as well as F4 and F18 genes as an indicator of colistin sulfate (CS) efficacy for treatment of PWD in pigs. Forty-eight piglets were weaned at the age of 21 days, and were divided into four groups: challenged treated, challenged untreated, unchallenged treated, and unchallenged untreated. Challenge was performed using 109 CFU of an ETEC: F4 strain, and treatment was conducted using oral CS at the dose of 50,000 IU/kg. The fecal presence of genes encoding for STa, STb, LT, F4 and F18 was detected using PCR.ResultsThe PCR amplification of ETEC virulence genes showed that nearly 100% of pigs excreted genes encoding for STa and STb toxins in the feces before the challenge. These genes, in the absence of the gene encoding F4, were considered as a marker for F4-negative ETEC. One day after ETEC: F4 oral challenge pigs in the two challenged groups excreted the genes encoding LT and F4 in the feces. These genes were considered as a marker for F4-positive ETEC. However, the gene encoding F18 was not detected in any fecal samples of the 4 groups throughout the experiment. After only 3 days of successive oral treatment with CS, a significant reduction in both the F4-positive and negative ETEC populations was observed in the challenged treated group compared to the challenged untreated group (p < 0.0001).ConclusionsOur study is among the first to report that under controlled farming conditions, oral CS treatment had a significant effect on both fecal F4-positive and F4-negative ETEC in pigs. However, CS clinical efficiency was correlated with non-detection of F4-positive ETEC in the feces. Furthermore the fecal presence of F4-negative ETEC was not associated with clinical symptoms of post-weaning diarrhea in pigs.Electronic supplementary materialThe online version of this article (doi:10.1186/s12866-016-0915-0) contains supplementary material, which is available to authorized users.