Induction and stability of oxidative stress adaptation in Listeria monocytogenes EGD (Bug600) and F1057 in sublethal concentrations of H2O2 and NaOH

Authors: ABEYSUNDARA, P - Mississippi State University; NANNAPANENI, R - Mississippi State University; SONI, K - Mississippi State University; SHARMA, C - Mississippi State University; MAHMOUD, B - Mississippi State University

Submitted to: International Journal of Food Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/26/2016
Publication Date: 12/1/2016
Citation: Abeysundara, P., Nannapaneni, R., Soni, K., Sharma, C.S., Mahmoud, B. 2016. Induction and stability of oxidative stress adaptation in Listeria monocytogenes EGD (Bug600) and F1057 in sublethal concentrations of H2O2 and NaOH. International Journal of Food Microbiology. 238:288-294.

Interpretive Summary: Oxidative stress is one of the main physiological stresses that L. monocytogenes cells undergo during cleaning and sanitation in the food processing environments. Our study examined the induction of oxidative stress adaptation of L. monocytogenes Bug600 (serotype 1/2a) and F1057 (serotype 4b) under a range of sublethal oxidative stress or sublethal alkaline stress. Our findings show that pre-exposure to either sublethal H2O2 (50 ppm for 30 min) or sublethal alkali (pH 9-10 for 30 min) readily triggers oxidative stress adaptation in both L. monocytogenes Bug600 and F1057. As a result of this, L. monocytogenes cells may become stress-hardened and resist harsh environmental conditions compared to non-adapted cells. These findings suggest that the complete elimination of the sublethal residues of these compounds in the food processing environment may avoid the induction of oxidative stress resistant phenotypes and may reverse the oxidative stress adaptation in L. monocytogenes if such stress adapted cells are present.

Technical Abstract: Food processing and food handling environments may contain residual levels of sanitizers or cleaners which may trigger oxidative stress adaptation in Listeria monocytogenes. The aim of this study was to determine the induction and stability of oxidative stress adaptation in L. monocytogenes EGD (Bug600) (serotype 1/2a) and F1057 (serotype 4b) at different concentrations and times of sublethal oxidative stress induced by H2O2 or sublethal alkali stress induced by NaOH at 37°C. Both L. monocytogenes Bug600 and F1057 strains showed significantly higher survival in lethal oxidative stress (1000ppm H2O2) after pre-exposure to 50ppm H2O2 for 30min compared to control cells (no pre-exposure to H2O2). When the cells were pre-exposed to sublethal alkali stress by NaOH, the oxidative stress adaptation was induced within 5min in L. monocytogenes. The survival of both L. monocytogenes strains was increased by 2 to 4.5 logs in lethal oxidative stress when the cells were pre-exposed to sublethal alkali stress at pH9 from 5 to 120min by NaOH compared to control cells (no pre-exposure to sublethal alkali pH). Two other alkali reagents tested (KOH and NH4OH) also induced oxidative stress adaptation in L. monocytogenes. For both L. monocytogenes strains, the oxidative stress adaptation induced by sublethal H2O2 was reversible in 30min and that induced by sublethal alkali stress was reversible within 60min at 37°C in the absence of such sublethal stress. These findings show that sublethal oxidative or alkali stress conditions can induce oxidative stress adaptation that may increase the risk of survival of L. monocytogenes cells in lethal oxidative stress.