Title: Assessment of Pseudomonas fluorescens and Escherichia coli 0157:H7 populations in monocultures and co-cultures as influenced by substrates, temperatures and storage times. Authors
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: March 5, 2014
Publication Date: August 3, 2014
Citation: Olanya, O.M., Ukuku, D.O., Niemira, B.A., Taylor, J. 2014. Assessment of Pseudomonas fluorescens and Escherichia coli 0157:H7 populations in monocultures and co-cultures as influenced by substrates, temperatures and storage times.. Meeting Abstract. IAFP Meeting. Indianapolis, Indiana. Volume 71, Page 67. Technical Abstract: Assessment of bacterial populations and growth in liquid cultures may enhance prediction of microbial interactions for biological applications. We quantified the populations of Pseudomonas fluorescens and Escherichia coli O157:H7 in monocultures and co-cultures following growth in nutrient abundant and deficient substrates. Bacteria populations were assayed in monocultures and co-cultures in sterile distilled water (SDW), buffered peptone water (BPW), and Trypticase Soy Agar (TSB) following incubation at temperatures of 5-37 deg C and storage times of 0 (control), 24 and 48 hrs. In co-cultures, E. coli O157:H7 cell counts were 1.71-6.27 (20 deg C) and 1.90-9.03 log CFU/ml at 35 deg C. Similarly, populations of P. fluorescens in co-cultures ranged from 3.09-5.91 and 2.88-8.36 at 20 and 35 deg C, respectively. As expected, the populations varied with bacterial strains, storage temperatures and time, and growth substrates; and were significantly (P<0.05) lower on SDW and BPW than on TSB. Populations of both bacteria were significantly (P<0.05) lower at 5 deg C than at temperatures of 20 or 35 deg C. Low suppressive activity of P. fluorescens against E. coli O157:H7 were recorded in these assays. Although the biocontrol potential of P. fluorescens on produce cannot be accurately predicted from in-vitro assays, these studies imply that suppressive effects of P. fluorescens on E. coli O157:H7, indicative of its biological control ability may be optimally quantified in nutrient-rich broths.