Temperature shock, injury and transient sensitivity to nisin in Gram negatives

• Published in: Journal of applied microbiology 2001-10, Vol.91 (4), p.715-724
• Main Authors: Boziaris, I.S, Adams, M.R
• Format: Article
• Language: English
• Subjects: Anti-Bacterial Agents - pharmacology; Biological and medical sciences; Cold Temperature; cold treatment; Food industries; Food microbiology; Freezing; Fundamental and applied biological sciences. Psychology; heat; Heat-Shock Response; Hot Temperature; hydrophobicity; lipopolysaccharides; microbiological quality; nisin; Nisin - pharmacology; permeability; Pseudomonas aeruginosa; Pseudomonas aeruginosa - drug effects; Pseudomonas aeruginosa - growth & development; Pseudomonas aeruginosa - physiology; Salmonella Enteritidis; Salmonella enteritidis - drug effects; Salmonella enteritidis - growth & development; Salmonella enteritidis - physiology; Staphylococcus aureus; Surface Properties; temperature
• ISSN: 1364-5072; 1365-2672
• DOI: 10.1046/j.1365-2672.2001.01433.x

Aims: The effect of thermal stresses on survival, injury and nisin sensitivity was investigated in Salmonella Enteritidis PT4, PT7 and Pseudomonas aeruginosa. Methods and Results: Heating at 55 degrees C, rapid chilling to 0.5 degrees C or freezing at -20 degrees C produced transient sensitivity to nisin. Cells were only sensitive if nisin was present during stress. Resistance recovered rapidly afterwards, though some cells displayed residual injury. Injury was assessed by SDS sensitivity, hydrophobicity changes, lipopolysaccharide release and NPN uptake. LPS release and hydrophobicity were not always associated with transient nisin sensitivity. Uptake of NPN correlated better but persisted longer after treatment. Conclusions: Thermal shocks produce transient injury to the outer membrane, allowing nisin access. After treatment, the permeability barrier is rapidly restored by a process apparently involving reorganization rather than biosynthetic repair. Significance and Impact of the Study: Inclusion of nisin during food treatments that impose sub-lethal stress on Gram negatives could increase process lethality, enhancing microbiological safety and stability.