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Survival of Escherichia coli O157:H7 transformed with either the pAK1-lux or pXEN-13 plasmids in in vitro bovine ruminal and fecal microbial fermentations

Duoss, Heather A., Donaldson, Janet R., Callaway, Todd R, Carroll, Jeffery A., Broadway, Paul R., Martin, James M., Shields-Menard, Sara, Schmidt, Ty B.
Foodborne pathogens and disease 2013 v.10 no.1 pp. 1
Escherichia coli O157, bacteria, cattle, genetic transformation, in vivo studies, microbial growth, models, pathogen survival, plasmids, rumen, rumen fermentation, shedding
The use of luminescent plasmids in bacteria may serve as a viable model for the real-time validation of various pre-harvest interventions on the colonization or shedding patterns of Escherichia coli O157:H7 within cattle. The objective of this study was to determine if the growth characteristics of E. coli O157:H7 in mixed ruminal and fecal microbial fluid cultures would be altered when transformed with one of the two luminescent plasmids:pAK1-lux (PAK) or pXEN-13 (XEN). Transformants harboring the luminescent plasmids were compared to the non-transformed parental strain (wild type [WT]) after incubating in mixed ruminal or fecal microbial fluid media for 6 h in triplicate (n = 3). The transformants and WT exhibited similar growth rates. Within mixed ruminal microbial fluid fermentations and mixed fecal microbial fluid, all transformants grew similarly ( p = 0.28) through the 6-h study. The reflective light unit (RLU; photons/pixel per second) photonic emissions of each plasmid within ruminal fluid differed at 0 h ( p = 0.002) and 2 h ( p = 0.02) and within fecal fluid at 0 h ( p = 0.009) and 2 h ( p = 0.04). The RLU remained the same within rumen fluid at 4 h ( p = 0.22) and 6 h ( p = 0.80) and within fecal fluid at 4 h ( p = 0.06) and 6 h ( p = 0.29). Growth of E. coli O157:H7 transformed with the bioluminescent plasmids was not altered in comparison to the WT, suggesting that both plasmids may serve as useful models for in vivo studies.