Adaptive Response of Listeria monocytogenes to the Stress Factors in the Food Processing Environment

Listeria monocytogenes are Gram-positive, facultatively anaerobic, non-spore-forming bacteria that easily adapt to changing environmental conditions. The ability to grow at a wide range of temperatures, pH, and salinity determines the presence of the pathogen in water, sewage, soil, decaying vegetation, and animal feed. L. monocytogenes is an etiological factor of listeriosis, especially dangerous for the elderly, pregnant women, and newborns. The major source of L. monocytogenes for humans is food, including fresh and smoked products. Its high prevalence in food is associated with bacterial adaptation to the food processing environment (FPE). Since the number of listeriosis cases has been progressively increasing an efficient eradication of the pathogen from the FPE is crucial. Understanding the mechanisms of bacterial adaptation to environmental stress will significantly contribute to developing novel, effective methods of controlling L. monocytogenes in the food industry.

Efficacy of a Next Generation Quaternary Ammonium Chloride Sanitizer on Staphylococcus and Pseudomonas Biofilms and Practical Application in a Food Processing Environment

Foodborne pathogens are known to adhere strongly to surfaces and can form biofilms in food processing facilities; therefore, their potential to contaminate manufactured foods underscores the importance of sanitation. The objectives of this study were to (1) examine the efficacy of a new-generation sanitizer (Decon7) on Staphylococcus and Pseudomonas biofilms, (2) identify biofilm bacteria from workers’ boots in relation to previous sanitizer chemistry, (3) validate the efficacy of Decon7 on biofilm from workers’ boots from an abattoir/food processing environment, and (4) compare the sensitivity of isolated boot biofilm bacteria to new- and early (Bi-Quat)-generation QAC sanitizers. Decon7 was applied at two concentrations (5%, 10%) and was shown to be effective within 1 min of exposure against enhanced biofilms of Staphylococcus spp. and Pseudomonas spp. in 96-well microplates. Decon7 was also used to treat workers’ boots that had accumulated high levels of biofilm bacteria due to ineffective sanitization. Bacteria isolated before enzyme/sanitizer treatment were identified through 16S rRNA PCR and DNA sequencing. All treatments were carried out in triplicate and analyzed by one-way RM-ANOVA or ANOVA using the Holm–Sidak test for pairwise multiple comparisons to determine significant differences (p < 0.05). The data show a significant difference between Decon7 sanitizer treatment and untreated control groups. There was a ~4–5 log reduction in Staphylococcus spp. and Pseudomonas spp. (microplate assay) within the first 1 min of treatment and also a > 3-log reduction in the bacterial population observed in the biofilms from workers’ boots. The new next-generation QAC sanitizers are more effective than prior QAC sanitizers, and enzyme pre-treatment can facilitate biofilm sanitizer penetration on food contact surfaces. The rotation of sanitizer chemistries may prevent the selective retention of chemistry-tolerant microorganisms in processing facilities.

The microbiome of water and water-associated biofilms in meat processing facilities

&lt;p&gt;Drinking water represents a reservoir for microorganisms. Microorganisms from water are able to attach to the inner surface of a water hose and nourish themselves by the leaking carbon molecules. Through the interaction of different species a multi-species biofilm can develop. Especially in the food processing environment biofilms in water hoses represent a risk factor. Within the food processing sector water hoses are often used to remove disinfecting agents from freshly cleaned surfaces, after the cleaning and disinfection procedure. When biofilms are located inside these water hoses, cells or cell clusters can detach, subsequently contaminating cleaned food contact surfaces.&lt;/p&gt; &lt;p&gt;We checked water hoses as a biofilm hotspot in a meat processing facility by using a flocked swab for biofilm sampling inside the water hose and accessory parts (i.e. nozzle). The bacterial load (culture-based and DNA-based) and the presence of matrix components (carbohydrates, proteins and extracellular DNA) were analysed. &amp;#160;&lt;/p&gt; &lt;p&gt;Herby we identified three from six tested water hoses to harbour a biofilm, by being positive for microorganisms and at least two matrix components. This clearly states the need for further understanding of biofilm formation in water hoses. Within the three other hoses, microorganisms could be detected, but no matrix components. We could isolate twelve genera of the water hose associated biofilms using one growth medium (TSA) and two different incubation temperatures (10&amp;#160;&amp;#176;C and 20&amp;#160;&amp;#176;C). There was only on genus that was present within all three water hose biofilms, which was &lt;em&gt;Rhodococcus&lt;/em&gt;. Previously this genus was isolated from a shower head (Lee 2013), and is known to catabolise a wide range of organic compounds. This potentially enables the growth in a nutrient poor environment like the water hose providing secondary colonisers launch aid to contribute to the biofilm. The genera &lt;em&gt;Flavobacterium&lt;/em&gt;, &lt;em&gt;Microbacterium&lt;/em&gt; and Stenotrophomonas were shared among two of the water hose biofilms. Experiments to assess the biofilm forming ability of &lt;em&gt;isolates&lt;/em&gt; of these genera using a mono-species static biofilm model indicate that all three species are able to produce matrix and can therefore be regarded as biofilm producers.&lt;/p&gt; &lt;p&gt;To date, there is limited information about biofilm development and presence in water hoses, especially in the food processing environment. This first identification of biofilms in water hoses and associated parts emphasizes the need of further research on this topic and detailed monitoring at these sites to prevent recontamination. A currently ongoing microbiome study on the water, the used water hoses, and the water-contacting food contact sites in a meat processing facility will give further details about the biofilm presence and possible transmission of microorganisms encountered there.&lt;/p&gt; &lt;p&gt;&amp;#160;&lt;/p&gt; &lt;p&gt;References:&lt;/p&gt; &lt;p&gt;Lee, Yoonjin. 2013. &amp;#8220;An Evaluation of Microbial and Chemical Contamination Sources Related to the Deterioration of Tap Water Quality in the Household Water Supply System.&amp;#8221; International Journal of Environmental Research and Public Health 10(9):4143&amp;#8211;60.&lt;/p&gt;

PCR–Restriction Fragment Length Polymorphism and Pulsed-Field Gel Electrophoresis Characterization of Listeria monocytogenes Isolates from Ready-to-Eat Foods, the Food Processing Environment, and Clinical Samples in South Africa

ABSTRACT Listeria monocytogenes is a ubiquitous, intracellular foodborne pathogen that is responsible for invasive listeriosis. The ability of L. monocytogenes to cause disease has some correlation with the serotypes of a specific lineage group, making the identification of lineage groups important for epidemiological analysis. The development of typing methods to link the strains of L. monocytogenes to an outbreak of listeriosis would help minimize the spread of the disease. The aim of this study was to design a PCR–restriction fragment length polymorphism (RFLP) method to differentiate between the lineage groups of L. monocytogenes. PCR-amplified fragments of the hly gene for 12 serotypes of L. monocytogenes were sequenced, aligned, and analyzed with the BioEdit program, and single nucleotide polymorphisms (SNPs) within regions of this gene were identified. Because of the difficulty in acquiring a serotype 4ab reference strain, this serotype was not included in this study. We tested the specificity and accuracy of the PCR-RFLP method on these L. monocytogenes reference strains and validated the method with 172 L. monocytogenes strains recovered from humans, food, and the food processing environment in 2000 to 2002 and 2008 to 2010 from regions within South Africa. PCR-RFLP analysis applied in this study placed L. monocytogenes serotypes into one of three lineage groups based on the sequence differences and SNPs within each lineage group. The SNPs were conserved in a region where RFLP analysis could be applied for a distinction between L. monocytogenes lineage groups. HIGHLIGHTS