|Nisbet, David - Dave|
Submitted to: Journal of Food Protection
Publication Type: Peer reviewed journal
Publication Acceptance Date: 12/22/2005
Publication Date: 5/1/2006
Citation: Dimitrijevic, M., Anderson, R.C., Callaway, T.R., Jung, Y.S., Harvey, R.B., Ricke, S.C., Nisbet, D.J. 2006. Inhibitory effects of select nitrocompounds on growth and survivability of Listeria monocytogenes in vitro. Journal of Food Protection. 69:1061-1065. Interpretive Summary: Listeria monocytogenes is an important pathogen capable of causing invasive infections in animals and humans. It is estimated that L. monocytogenes causes approximately 2500 serious human illnesses and as many as 500 deaths per year in the United States at substantial cost. We report here results from experiments testing the effects of the potential chemical inhibitors 2-nitro-1-propanol (2NPOH), 2-nitroethanol (2NEOH) and nitroethane (NE), on growth and survivability of L. monocytogenes. In all cases, inhibition was greatest with 2NPOH and least with NE. For instance, the growth of L. monocytogenes was significantly reduced by as much as 78% when tested with 2NPOH. Inhibition of L. monocytogenes growth by 2NPOH, 2NEOH and NE was observed whether tested at two typical incubation temperatures, 30 and 37 deg C, or whether in the presence of oxygen, as would be expected in feed or food, or in the absence of oxygen, as would be expected in gut environments. The survivability of L. monocytogenes was also reduced during storage at refrigeration temperatures. The ability of L. monocytogenes to survive and grow at cold temperatures is one of the characteristics that make it such a dangerous pathogen. Results from the present study show that 2NEOH, NE and in particular, 2NPOH, inhibited L. monocytogenes under a variety of conditions. This research provides the basis for further studies to develop new disinfectants and feed ingredients to control this important foodborne pathogen in animals and foods. Ultimately, this research will help farmers and food manufacturers produce safer food products for the American consumer.
Technical Abstract: We report the effects of 2-nitro-1-propanol (2NPOH), 2-nitroethanol (2NEOH) and nitroethane (NE), on growth and survivability of L. monocytogenes. In all cases, inhibition was greatest with 2NPOH and least with NE. For instance, specific growth rates of L. monocytogenes strain 18 were reduced (P < 0.05) 76, 60 and 29% from controls incubated without added nitrocompound (0.62 ± 0.02 h**-1) during aerobic culture at 37 deg C in brain heart infusion (BHI) broth containing 10 mM 2NPOH, 2NEOH or NE, respectively. Specific growth rates of L. monocytogenes strain Scott A were reduced (P < 0.05) 67, 45 and 11%, respectively, from controls (0.67 ± 0.02 h**-1) when cultured similarly. Specific growth rates for L. monocytogenes strain 18 incubated similarly except at 30 deg C were reduced (P < 0.05) 76, 60 and 30%, respectively, and were reduced (P < 0.05) 78, 23 and 23% during anaerobic culture at 30 deg C in BHI containing 15 mM 2NPOH, 2NEOH or NE (control rates ranged from 0.37 ± 0.07 to 0.74 ± 0.05 h**-1). Survivability of L. monocytogenes strain 18 was reduced (P < 0.05) during aerobic storage (4 mo at 4 deg C) in BHI containing 2NPOH or 2NEOH (by 7.8 and 1.9 log units, respectively) but not NE. The inhibitory effect of 2NPOH was approximately 20% greater during growth at pH 7.0 than at pH 5.6 or 8.0. These results demonstrate the differential inhibitory activity of 2NPOH, 2NEOH and NE against L. monocytogenes in vitro.