Establishment of a linear regression equation for quantification of beta-hemolytic Escherichia coli in different media and survival of hemolytic Escherichia coli after blending with three different media

Abstract

: Pathogenic E. coli associated post-weaning diarrhea (PWD) and edema disease are common diseases in commercially-housed weanling pigs. An enterotoxigenic E. coli (ETEC) oral challenge model has been used to mimic the physiological responses observed in commercial conditions. However, an oral challenge procedure has two major limitations: (1) the ETEC cell density is unknown at the point of oral inoculation, and (2) blending ETEC with traditional TSB (trypticase soy broth) is not palatable and hence decreases acceptability by piglets. Therefore, the purposes of this study were to (1) establish a regression equation that can be used for estimation of ETEC concentration in dilution media using the spectrophotometric measurement of cell density; and (2) examine survival of ETEC after blending either with TSB, sweetener or dextrose. A strain of ETEC (serogroup beta-hemolytic E. coli O149; K91; F4; toxins LT, STa, STb) was grown in TSB for 3.5 hours, centrifuged, the supernatant was discarded, and the ETEC pellet was then blended either with TSB (100 mL), sweetener (60 mL TSB + 40 mL fruit flavored concentrate), or dextrose (50 mL TSB + 50 mL dextrose; 0.5g/mL dextrose). Cell density was measured using the colorimetric method and also plated on a 5% sheep blood agar for counting of ETEC colony forming units at 0, 5, 35, 65 and 125 min after blending. The optical density at 600 nm explained 83% of ETEC colony forming units, indicating that the established linear equation (y= 6E+08x -4E+07, P<0.004) can be used for robust quantification of ETEC cell density in TSB, sweetener and dextrose media. When ETEC was blended with sweetener and dextrose, survival of ETEC was decreased by 45% and 72% within 5 min post-blending. Therefore, further research is required to find out the suitable medium that has potential to improve palatability without compromising survival of ETEC.

Technical note: novel delivery methods for an enterotoxigenic Escherichia coli infection model in MUC4-locus sequenced weaner pigs1

“…Conventionally, in this system pigs are dosed orally with a liquid broth culture of ETEC-F4 at some time point(s) after weaning, with diarrhea subsequently monitored. However, due to the generally high volume given, low palatability, stress of the procedure, and the time taken, there is often spillage and (or) aspiration of ETEC into the lungs (Kim et al, 2014; Luise et al, 2019). This cannot only lower the prevalence of diarrhea, but also present a potential welfare issue.…”

Effects of saccharin (sweetener) supplementation on growth performance, fecal moisture and litter performance of lactating sows

“…Thus, researchers have done a lot of research in this area. Artificial sweeteners, routinely included in piglets' diet, were thought to enhance feed palatability (Moran et al, 2010;Kim et al, 2014).…”