Response of Listeria monocytogenes to Disinfection Stress at the Single-Cell and Population Levels as Monitored by Intracellular pH Measurements and Viable-Cell Counts
| Autor: | Vicky Gaedt Kastbjerg, Dennis Sandris Nielsen, Lone Gram, Nils Arneborg |
|---|---|
| Rok vydání: | 2009 |
| Předmět: |
Cytoplasm
Physiology Disinfectant Sodium Intracellular pH Population Colony Count Microbial chemistry.chemical_element Sodium Chloride medicine.disease_cause Applied Microbiology and Biotechnology Microbiology Listeria monocytogenes Stress Physiological medicine education education.field_of_study Microbial Viability Ecology biology Hydrogen-Ion Concentration biology.organism_classification Microscopy Fluorescence chemistry Bacteria Intracellular Disinfectants Food Science Biotechnology |
| Zdroj: | Applied and Environmental Microbiology. 75:4550-4556 |
| ISSN: | 1098-5336 0099-2240 |
| DOI: | 10.1128/aem.02625-08 |
| Popis: | Listeria monocytogenes has a remarkable ability to survive and persist in food production environments. The purpose of the present study was to determine if cells in a population of L. monocytogenes differ in sensitivity to disinfection agents as this could be a factor explaining persistence of the bacterium. In situ analyses of Listeria monocytogenes single cells were performed during exposure to different concentrations of the disinfectant Incimaxx DES to study a possible population subdivision. Bacterial survival was quantified with plate counting and disinfection stress at the single-cell level by measuring intracellular pH (pH i ) over time by fluorescence ratio imaging microscopy. pH i values were initially 7 to 7.5 and decreased in both attached and planktonic L. monocytogenes cells during exposure to sublethal and lethal concentrations of Incimaxx DES. The response of the bacterial population was homogenous; hence, subpopulations were not detected. However, pregrowth with NaCl protected the planktonic bacterial cells during disinfection with Incimaxx (0.0015%) since pH i was higher (6 to 6.5) for the bacterial population pregrown with NaCl than for cells grown without NaCl (pH i 5 to 5.5) ( P < 0.05). The protective effect of NaCl was reflected by viable-cell counts at a higher concentration of Incimaxx (0.0031%), where the salt-grown population survived better than the population grown without NaCl ( P < 0.05). NaCl protected attached cells through drying but not during disinfection. This study indicates that a population of L. monocytogenes cells, whether planktonic or attached, is homogenous with respect to sensitivity to an acidic disinfectant studied on the single-cell level. Hence a major subpopulation more tolerant to disinfectants, and hence more persistent, does not appear to be present. |
| Databáze: | OpenAIRE |
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