Chlorophyllin supplementation of medicated or unmedicated swine diets impact on fecal Escherichia coli and enterococci

Authors: FEYE, KRISTINA - University Of Arkansas; RASMUSSEN, MARK - Iowa State University; Anderson, Robin; Crippen, Tawni - Tc; Harvey, Roger; Poole, Toni; RICKE, STEVEN - University Of Wisconsin; Yeater, Kathleen

Submitted to: Animals
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/26/2024
Publication Date: 7/2/2024
Citation: Feye, K., Rasmussen, M.A., Anderson, R.C., Crippen, T.L., Harvey, R.B., Poole, T.L., Ricke, S.C., Yeater, K.M. 2024. Chlorophyllin supplementation of medicated or unmedicated swine diets impact on fecal Escherichia coli and enterococci. Animals. 14(13). Article 1955. https://doi.org/10.3390/ani14131955.
DOI: https://doi.org/10.3390/ani14131955

Interpretive Summary: Feeding pigs diets containing added antibiotics has been found to select for high carriage of bacterial genes coding for multidrug efflux pumps that can contribute to antibiotic resistance. It has recently been demonstrated that intermediate and end products of chlorophyll compounds digested in the gut of animals consuming green forage, can inhibit efflux pump activity. Considering that commercially reared pigs generally do not eat substantial amounts of feeds containing chlorophyll, this study was conducted to test if feeding pigs a water-soluble chlorophyll product could affect the antibiotic resistance profiles of wildtype populations of fecal Escherichia coli and enterococci. Results from two feeding trials indicate that feeding chlorophyll as a source or precursor of some known efflux pump inhibitors may indeed promote a decrease in antibiotic resistance in the enterococcal but not the E. coli populations. However, under the conditions of the present study the decrease in enterococcal resistance was likely not enough to warrant development into an inexpensive technology to preserve and enhance the efficacy of currently available antibiotics. However, further research designed to optimize chlorophyll administration could potentially lead to practical applications for the swine industry. These results provide important new information on potential strategies being investigated to sustain antibiotic efficiencies in agriculture. Ultimately, this research will help livestock producers find effective new technologies to continue producing safe and wholesome foods for the American consumer.

Technical Abstract: High carriage of genes coding for multidrug efflux pumps has been observed within the pig gut microbiome after consumption of medicated diets. Considering that certain catabolitic products of anaerobic chlorophyll degradation inhibits efflux pump activity, this study was conducted to test if feeding pigs a water soluble chlorophyllin product could affect the antibiotic resistance profiles of wildtype populations of fecal Escherichia coli and enterococci. Trial 1 evaluated the effects of chlorophyllin supplementation (300 mg/meal) in pigs fed twice daily diets supplemented without or with ASP250 (containing chlortetracycline, sulfamethazine, and penicillin at 100, 100 and 50 g/ton, respectively). Trial 2, conducted similarly, evaluated chlorophyllin supplementation in pigs fed diets supplemented without or with 100 g tylosin/ton. Each trial lasted 12 days and fecal samples were collected and selectively cultured at 4-day intervals to enumerate total generic Escherichia coli and enterococcal populations as well as those phenotypically capable of growing in the presence of the fed antibiotics. Performance results from both studies revealed no effect (P > 0.05) of chlorophyllin, antibiotic, or their combined supplementation on average daily feed intake or average daily gain. Daily fed intake tended to be lower (P = 0.0528) with pigs fed diets supplemented with, than without tylosin. Results from trial 1 showed that the ASP250-medicated diets, whether without or with chlorophyllin supplementation, supported higher (P < 0.05) fecal E. coli populations than the non-medicated diets. Enterococcal populations, however, were lower, albeit marginally and not necessarily significantly, in feces from pigs fed the ASP250-medicated than those fed the non-medicated diet. Results from trial 2 likewise revealed an increase (P < 0.05) in E. coli and, to a lesser extent, enterococcal populations in feces collected from pigs fed the tylosin-medicated diet than the non-medicated diet. Evidence indicated, however, that the E. coli and enterococcal populations in trial 1 were generally insensitive to penicillin or chlortetracycline as there was no difference between populations recovered without or with antibiotic selection. Conversely, a treatment x day of treatment interaction observed in trial 2 (P < 0.05) provided evidence, albeit slight, enrichment of tylosin-insensitive enterococci in feces from the pigs fed the tylosin-medicated but not the non-medicated diet. Under the conditions of the present study, it is unlikely that chlorophyllin-derived efflux pump inhibitors potentially present in the chlorophyllin-fed pigs were able to enhance the efficacy of available antibiotics. However, optimization in dose regimen and further characterization could lead to potential practical applications that have commercial potential.