Soil collected in the Great Smoky Mountains National Park yielded a novel Listeria species, L. swaminathanii, effectively expanding the sensu stricto clade to ten species

Soil samples collected in the Great Smoky Mountains National Park yielded a Listeria isolate that could not be classified to the species level. Whole-genome sequence-based average nucleotide identity BLAST and in silico DNA-DNA Hybridization analyses confirmed this isolate to be a novel Listeria sensu stricto species with the highest similarity to L. marthii (ANI=93.9%, isDDH=55.9%). Additional whole-genome-based analysis using the Genome Taxonomy Database Toolkit, an automated program for classifying bacterial genomes, further supported delineation as a novel Listeria sensu stricto species, as this tool failed to assign a species identification but identified L. marthii as the closest match. Phenotypic and genotypic characterization results indicate that this species is nonpathogenic. Specifically, the novel Listeria species described here is phenotypically (i) non-hemolytic and (ii) negative for phosphatidylinositol-specific phospholipase C activity; the draft genome lacks all virulence genes found in the Listeria pathogenicity island 1 (LIPI-1), as well as the internalin genes inlA and inlB. While the type strain for the new species is phenotypically catalase-negative (an unusual characteristic for Listeria sensu stricto species), its genome contained an apparently intact catalase gene (kat); hence assessment of this phenotype with future isolates will be important. Rapid species identification systems (Listeria API, VITEK 2, VITEK MS) misidentified this novel species as either L. monocytogenes, L. innocua, or L. marthii. We propose the name L. swaminathanii, and the type strain is FSL L7-0020T (=ATCC TSD-239T).

Isolation, Identification and Antibiotic Susceptibility Patterns of Listeria Monocytogens from Pregnant Women

IntroductionThe present study is made to determine the prevalence rate, isolation, identification and antibioticsusceptibility pattern of L. monocytogens isolated from pregnant women. This research not onlyguides to the clinician for treatment but also help laboratory worker to monitor susceptibilitypattern among the Listeria species. MethodsThe samples were collected from Gynecology department from January 2017 to December 2019and processed in the Department of Microbiology at College of Medical Sciences, Bharatpur Nepal.Two hundred thirty four antenatal mothers having age between 17 and 39 years of gestation periodbetween 7th weeks and 36th weeks patient with a flue like sign and symptoms were screened forL. monocytogens. Bacterial isolation identification and antibiotic sensitivity tests were done as perstandard microbiological guidelines. ResultsIn this present research, the prevalence of L. monocytogens was found 39/234 (16.7%), where high rate of Listeria infection was found 21(53.1%) among the patients of age between 25 and 32 who were mostly from urban area. We found eating meat 38(97.4%) and fish 39(100.0%), non-pasteurized simple boiled milk 39(100.0%) and vegetables like salad eater 32(82.1%) has highest rate of listeriosis. The results showed most of the listeriosis were occurring in a 3rd trimester 17(43.6%) compared with the 2nd and 1st trimester. Overall, the antibiotics resistance pattern found low in L. monocytogens. This investigation also showed less resistance in erythromycin 9(23.1%), ciprofloxacin 8(20.5%), chloramphenicol 16(41.1%). The increased resistance pattern among Listeria species were found in penicillin 31(79.5%), cotrimoxazole 20(51.3%), amoxicillin 21(55.1%) and vancomycin 29(74.4%). ConclusionsIt is very important to consider listeriosis in a clinical practice now a day. Maternal Listeriosis shouldbe considered in all age group of pregnant women. Regular surveillance of antibiotic susceptibility test is very much important for clinician to select best medicine to treat different cases of listeriosis.

Incidence, Enumeration and Confirmation of Listeria and its Species in Ready-to-eat Street Vended Salads Sold at Various Outlets of Faisalabad City, Pakistan

The desire for a healthy lifestyle and faster mode of preparation has supported the consumption of ready to eat fresh salad. Street vended salads are recognized as a source of pathogenic transamination in different parts of the world. The present study was designed to evaluate the safety status of fresh vegetable and Russian salads being sold at various food outlets of Faisalabad. Samples of freshly prepared salads were collected from representative selected different areas of Faisalabad city divided into four different zones (zone 1, zone 2, zone 3 and zone 4). Prevalence and enumeration of Listeria was done through microbial testing via the spread plate method. Among samples of vegetable salad, highest prevalence of Listeria was found in the zone 2 (75%) whereas Russian salad samples from zones 1 and 3 exhibited 62% prevalence, the highest among all 4 zones of study. On the whole, the lowest prevalence of Listeria was found in zone 4 (50% vegetable salad and 58% Russian salad). Biochemical conformation of Listeria done through different tests for the identification of various Listeria species, exhibited that Listeria monocytogenes and Listeria innocua were highly prevalent in samples from zones 1 and 3 respectively. The results will help to improve safety concerns associated with street vended foods.

Proteomic Characterization of Antibiotic Resistance in Listeria and Production of Antimicrobial and Virulence Factors

Some Listeria species are important human and animal pathogens that can be found in contaminated food and produce a variety of virulence factors involved in their pathogenicity. Listeria strains exhibiting multidrug resistance are known to be progressively increasing and that is why continuous monitoring is needed. Effective therapy against pathogenic Listeria requires identification of the bacterial strain involved, as well as determining its virulence factors, such as antibiotic resistance and sensitivity. The present study describes the use of liquid chromatography–electrospray ionization tandem mass spectrometry (LC–ESI–MS/MS) to do a global shotgun proteomics characterization for pathogenic Listeria species. This method allowed the identification of a total of 2990 non-redundant peptides, representing 2727 proteins. Furthermore, 395 of the peptides correspond to proteins that play a direct role in Listeria pathogenicity; they were identified as virulence factors, toxins and anti-toxins, or associated with either antibiotics (involved in antibiotic-related compounds production or resistance) or resistance to toxic substances. The proteomic repository obtained here can be the base for further research into pathogenic Listeria species and facilitate the development of novel therapeutics for these pathogens.

A Systematic Review of Listeria Species and Listeria monocytogenes Prevalence, Persistence, and Diversity throughout the Fresh Produce Supply Chain

Listeria monocytogenes is an increasing food safety concern throughout the produce supply chain as it has been linked to produce associated outbreaks and recalls. To our knowledge, this is the first systematic literature review to investigate Listeria species and L. monocytogenes prevalence, persistence, and diversity at each stage along the supply chain. This review identified 64 articles of 4863 candidate articles obtained from four Boolean search queries in six databases. Included studies examined naturally detected/isolated Listeria species and L. monocytogenes in fresh produce-related environments, and/or from past fresh produce associated outbreaks or from produce directly. Listeria species and L. monocytogenes were detected in each stage of the fresh produce supply chain. The greatest prevalence of Listeria species was observed in natural environments and outdoor production, with prevalence generally decreasing with each progression of the supply chain (e.g., packinghouse to distribution to retail). L. monocytogenes prevalence ranged from 61.1% to not detected (0.00%) across the entire supply chain for included studies. Listeria persistence and diversity were also investigated more in natural, production, and processing environments, compared to other supply chain environments (e.g., retail). Data gaps were identified for future produce safety research, for example, in the transportation and distribution center environment.

Prevalence of Listeria species and Listeria monocytogenes on Raw Produce Arriving at Frozen Food Manufacturing Facilities

Ubiquity of Listeria monocytogenes in the environment impacts the food industry and presents concerns for frozen food facilities. This study determined the prevalence and numbers of Listeria species and L. monocytogenes on raw produce arriving at frozen food facilities. Raw produce was collected using multi-level blinding protocols to ensure anonymity of participants and avoid traceback. Five raw vegetables were selected: corn, carrots, green beans, peas, and spinach. Raw products were collected after arrival at the facilities but before any cleaning or other pre-processing steps that are typically performed inside the facility. The FDA BAM method for detection of Listeria spp. and L. monocytogenes was followed, with PCR screening followed by selective plating methods. Listeria numbers were estimated from positive samples using MPN methodology. A total of 290 samples were collected, with 96 and 17 samples positive for Listeria spp. (33.1%) and L. monocytogenes (5.9%), respectively. Enumeration data for the 96 Listeria spp. samples indicated 82 samples had greater than 100 MPN Listeria spp./g and 14 samples less than 100 MPN Listeria spp./g. The prevalence of Listeria spp. varied by commodity: spinach (66.7%), peas (50%), corn (32.2%), green beans (22.2%), and carrots (13%). L. monocytogenes prevalence was determined in corn (13.6%), peas (6.3%), and green beans (4.2%) arriving at processing facilities. Such data was previously unavailable to frozen vegetable processors and is valuable in implementing process control standards. The prevalence and pathogen concentration data from raw commodities found in this study can provide the industry information to conduct more accurate quantitative risk assessments and provide a baseline to model and target appropriate pathogen reduction steps during processing.