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Title: Examination of the cultivatable, aerobic microflora of swine feces and stored swine manure on various media and antibiotics

item Whitehead, Terence
item Cotta, Michael

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 5/14/2014
Publication Date: 5/20/2014
Citation: Whitehead, T.R., Cotta, M.A. 2014. Examination of the cultivatable, aerobic microflora of swine feces and stored swine manure on various media and antibiotics [abstract]. American Society of Microbiology. Poster No. 1451.

Interpretive Summary:

Technical Abstract: Antimicrobial compounds have been commonly used as feed additives for domestic animals to reduce infection and promote growth. Recent concerns have suggested that such feeding practices may result in increased microbial resistance to antibiotics. Our laboratory has been studying the predominant commensal anaerobic bacteria present in both pig feces and manure storage pits in relation to odor production and antibiotic resistance. However, little is known regarding antibiotic resistance in the aerobic bacterial populations which are present in much lower numbers but could add significantly to the resistance gene pool of these ecosystems. This study describes the results of recovery of aerobic bacteria plated on various media in the presence and absence of antibiotics. Swine feces and manure were collected from a local swine farm. Samples were plated onto brain-heart infusion, T-soy, nutrient or habitat simulating medium agar with and without tetracycline, tylosin, or erythromycin at 10 ug/ml to determine relative levels of antibiotic resistance. Plates were incubated at 37°C and colonies counted daily. Randomly selected colonies were isolated and characterized by 16S rDNA sequence analyses and additional antibiotic resistance and biochemical analyses. Under aerobic conditions colonies were recovered at levels of 10-6 to 10-7 CFU/ml. These values are approximately 100-fold lower than numbers obtained when platings and cultivation are performed under anaerobic conditions. Observed colony counts were similar using habitat simulating medium, BHI, or T-Soy media with approximately 10-fold lower counts for nutrient agar. Addition of antibiotics to the media resulted in counts that were 60%-80% of those in control media without antibiotics. Results of 16S rDNA sequence and biochemical analyses of isolated strains demonstrated the presence of known bacterial genera as well as novel genera and species. The recoverable aerobic microflora of swine feces and manure contain high percentage of antibiotic resistant bacteria. The strains isolated represent both known and novel genera and species. Further analyses of these and additional isolates should provide information on these organisms as potential reservoirs of antibiotic resistance genes in these ecosystems.