Evaluation ofListeria innocuaas a suitable indicator for replacingListeria monocytogenesduring ripening of Camembert cheese

Design of a novel affinity probe using the cell wall-binding domain of a Listeria monocytogenes autolysin for pathogen detection

IMPORTANCE

Human listeriosis is caused by consuming foods contaminated with the bacterial pathogen Listeria monocytogenes, leading to the development of a severe and life-threatening foodborne illness. Detection of L. monocytogenes present in food and food processing environments is crucial for preventing Listeria infection. The L. monocytogenes peptidoglycan hydrolase IspC anchors non-covalently to the bacterial surface through its C-terminal cell wall-binding domain (CWBD), CWBDIspC. This study explored the surface binding property of CWBDIspC to design, construct, characterize, and assess an affinity molecular probe for detecting L. monocytogenes. CWBDIspC recognized a cell wall ligand lipoteichoic acid that remains evenly displayed and mostly unoccupied on the bacterial surface for interaction with the exogenously added CWBDIspC. CWBDIspC, when fused to the enhanced green fluorescent protein reporter or covalently conjugated onto magnetic beads, exhibited the functionality as an antibody alternative for rapid detection and efficient separation of the pathogen.

A Comparative Study of the Susceptibility of Listeria Species to Sanitizer Treatments When Grown under Planktonic and Biofilm Conditions

Listeria species are ubiquitous in nature and can adapt to survive in a variety of niches, including food processing environments. Listeria species that colonize these environments may also have the potential to persist. Food safety strategies designed to manage these niches include regular cleaning and disinfection with proven sanitizers containing biocide-active compounds. Typically, these sanitizers are effective against bacteria growing under planktonic conditions, but their efficacy may be compromised when bacteria are contained in biofilms. The susceptibility of persistent Listeria isolates, i.e., those capable of forming biofilms, to a selection of sanitizers was investigated. A quaternary ammonium compound-based sanitizer was the biocide most effective against planktonic bacteria, with a MIC of 0.0015 to 0.006%. In contrast, ethanol-based sanitizers were the least effective. Although, no triclosan tolerance was observed for planktonic Listeria isolates, triclosan was the only biocide that resulted in a significant biomass reduction. Differences between Listeria species were observed; L. monocytogenes and L. welshimeri biofilms were more tolerant to quaternary ammonium compound-based sanitizers than were L. innocua biofilms. These findings extend our understanding of the application of commonly used sanitizers in the food industry and the efficacy of these sanitizers against Listeria species and their associated biofilms.

Listeria monocytogenes incidence changes and diversity in some Brazilian dairy industries and retail products

Listeria monocytogenes can cause listeriosis, a severe foodborne disease. In Brazil, despite very few reported cases of listeriosis, the pathogen has been repeatedly isolated from dairies. This has led the government to implement specific legislation to reduce the hazard. Here, we determined the incidence of L. monocytogenes in five dairies and retail products in the Southeast and Midwest regions of Brazil over eight months. Of 437 samples, three samples (0.7%) from retail and only one sample (0.2%) from the dairies were positive for L. monocytogenes. Thus, the contamination rate was significantly reduced as compared to previous studies. MultiLocus Sequence Typing (MLST) was used to determine if contamination was caused by new or persistent clones leading to the first MLST profile of L. monocytogenes from the Brazilian dairy industry. The processing environment isolate is of concern being a sequence-type (ST) 2, belonging to the lineage I responsible for the majority of listeriosis outbreaks. Also, ST3 and ST8 found in commercialized cheese have previously been reported in outbreaks. Despite the lower incidence, dairy products still pose a potential health risk and the occurrence of L. monocytogenes in dairies and retail products emphasize the need for continuous surveillance of this pathogen in the Brazilian dairy industry.

Novel LDPE/halloysite nanotube films with sustained carvacrol release for broad-spectrum antimicrobial activity

Halloysite nanotubes are employed as nanocarriers of carvacrol, allowing for its high-temperature melt compounding with polyethylene, and resulting in highly potent antimicrobial films.

Occurrence and genetic relatedness of Listeria spp. in two brands of locally processed ready-to-eat meats in Trinidad

Contamination of locally produced, ready-to-eat meats by Listeria spp. has been previously reported at one processing plant in Trinidad. However, the status of this pathogen in locally produced products sold at retail outlets is unknown. This study was conducted to establish whether there is a risk to consumers of locally processed meats caused by the presence of Listeria spp., and whether a link exists between the presence of the pathogen in retail products and the manufacturing plant of one brand (B). Four hundred and eighty ready-to-eat meat products of two popular local brands (A and B) were collected from retail outlets and analysed for the presence of Listeria spp. together with food samples and surfaces from one manufacturing plant (B). Eighty-eight of the retail products (18·3%) were contaminated with Listeria spp., of which, 52·3% were L. innocua, 44·3% were L. monocytogenes and 3·4% belonged to the L. seeligeri-L. welshimeri-L. ivanovii (Siwi) group. L. innocua was found in 15 in-process food samples and on three surfaces of equipment at plant B. Four in-process food samples were also contaminated with Siwi isolates. Repetitive extragenic palindromic PCR DNA fingerprinting showed a possible association between strains of different Listeria spp. and brand as well as with manufacturing plant B.

Decisive role of structure in food microbial colonization and implications for predictive microbiology

Predictive models must consider the significant effect of the physical structure of the food on the magnitude and type of microbial growth. Before such models are developed, a thorough characterization of the food structure is mandatory because this information will determine the modeling approach. In this work, several physical structures common in poultry products were classified and described. Chicken breast skin and flesh and minced breasts were examined by scanning electron microscopy and compared with a meat-based model food. Such systems were surface or internally inoculated with Listeria innocua and incubated at 25 degrees C for 24 h. Different structures, including several substructures, found in the studied systems affected microbial distribution and growth. Based on these experimental findings, the most suitable type of model for each physical structure was determined. This information provides further clarification for predictive microbiology models.

Antilisterial effects of gravinol-s grape seed extract at low levels in aqueous media and its potential application as a produce wash

Grape seed extract (GSE) is a rich source of proanthocyanidins, a class of natural antioxidants reported to have wide-ranging bioactivity as anti-inflammatory, anticarcinogenic, and antimicrobial agents. The ability of GSE to rapidly inactivate Listeria monocytogenes in vitro and the generally recognized as safe status of GSE make this extract an attractive candidate for control of Listeria in or on foods. Previously, GSE has been used at relatively high concentrations (1%) in complex food matrices and in combination with other antimicrobials. We sought to characterize the antilisterial effects of a commercial GSE preparation (Gravinol-S) alone at much lower concentrations (0.00015 to 0.125%) in aqueous solution and to test its possible use as an antimicrobial wash for fresh produce surfaces. Based on broth microdilution tests, the MICs of GSE against L. monocytogenes Scott A and Listeria innocua ATCC 33090 were as low as 50 and 78 mug ml(-1), respectively. GSE was evaluated in 0.85% saline against live cells of L. innocua via flow cytometry, using propidium iodide as a probe for membrane integrity. At sub-MICs and after only 2 min of exposure, treatment with GSE caused rapid permeabilization and clumping of L. innocua, results that we confirmed for L. monocytogenes using fluorescence microscopy and Live/Dead staining. At higher concentrations (0.125%), GSE reduced viable cell counts for L. monocytogenes by approximately 2 log units within 2 min on tomato surfaces. These results suggest the potential for GSE as a natural control of Listeria spp. on low-complexity foods such as tomatoes.