Effect of different oral oxytetracycline treatment regimes on selection of antimicrobial resistant coliforms in nursery pigs.

A major concern derived from using antimicrobials in pig production is the development of resistance. This study aimed to assess the impact of selected combinations of oral dose and duration of treatment with oxytetracycline (OTC) on selection of tetracycline resistant (TET-R) coliforms recovered from swine feces. The work encompassed two studies: 1) OTC 5mg/kg and 20mg/kg were administered to nursery pigs for 3 and 10days, respectively, under controlled experimental conditions, and 2) 10mg/kg, 20mg/kg and 30mg/kg OTC were given to a higher number of pigs for 6, 3 and 2days, respectively, under field conditions.

Genotype variation and genetic relationship among Escherichia coli from nursery pigs located in different pens in the same farm.

Background: So far, little is known about the genetic diversity and relatedness among Escherichia coli (E. coli) populations in the gut of swine. Information on this is required to improve modeling studies on antimicrobial resistance aiming to fight its occurrence and development.

Modeling the growth dynamics of multiple Escherichia coli strains in the pig intestine following intramuscular ampicillin treatment.

Background: This study evaluated how dosing regimen for intramuscularly-administered ampicillin, composition of Escherichia coli strains with regard to ampicillin susceptibility, and excretion of bacteria from the intestine affected the level of resistance among Escherichia coli strains in the intestine of nursery pigs. It also examined the dynamics of the composition of bacterial strains during and after the treatment. The growth responses of strains to ampicillin concentrations were determined using in vitro growth curves.

Multistrain models predict sequential multidrug treatment strategies to result in less antimicrobial resistance than combination treatment.

Background: Combination treatment is increasingly used to fight infections caused by bacteria resistant to two or more antimicrobials. While multiple studies have evaluated treatment strategies to minimize the emergence of resistant strains for single antimicrobial treatment, fewer studies have considered combination treatments. The current study modeled bacterial growth in the intestine of pigs after intramuscular combination treatment (i.

Apramycin treatment affects selection and spread of a multidrug-resistant Escherichia coli strain able to colonize the human gut in the intestinal microbiota of pigs.

The effect of apramycin treatment on transfer and selection of an Escherichia coli strain (E. coli 912) in the intestine of pigs was analyzed through an in vivo experiment. The strain was sequenced and assigned to the sequence type ST101 and serotype O11.

Pharmacodynamic modelling of in vitro activity of tetracycline against a representative, naturally occurring population of porcine Escherichia coli.

Background: The complex relationship between drug concentrations and bacterial growth rates require not only the minimum inhibitory concentration but also other parameters to capture the dynamic nature of the relationship. To analyse this relationship between tetracycline concentration and growth of Escherichia coli representative of those found in the Danish pig population, we compared the growth of 50 randomly selected strains. The observed net growth rates were used to describe the in vitro pharmacodynamic relationship between drug concentration and net growth rate based on E max model with three parameters: maximum net growth rate (amax); concentration for a half-maximal response (E max); and the Hill coefficient (γ).

Tentative colistin epidemiological cut-off value for Salmonella spp.

The objective of this research was to determine minimal inhibitory concentration (MIC) population distributions for colistin for Salmonella on subtype level. Furthermore, we wanted to determine if differences in MIC for colistin could be explained by mutations in pmrA or pmrB encoding proteins involved in processes that influence the binding of colistin to the cell membrane. During 2008-2011, 6,583 Salmonella enterica subsp.