Polar-Region Soils as Novel Reservoir of Lactic Acid Bacteria from the Genus Carnobacterium.

Polar habitats offer excellent sites to isolate unique bacterial strains due to their diverse physical, geochemical, and biological factors. We hypothesize that the unique environmental conditions of polar regions select for distinct strains of lactic acid bacteria (LAB) with novel biochemical properties. In this study, we characterized ten strains of psychrotrophic LAB isolated from hitherto poorly described sources-High Arctic and maritime Antarctic soils and soil-like materials, including ornithogenic soils, cryoconites, elephant seal colonies, and postglacial moraines. We evaluated the physiological and biochemical properties of the isolates. Based on 16S rRNA and housekeeping genes, the four LAB strains were assigned to three Carnobacterium species: C. alterfunditum, C. maltaromaticum, and C. jeotgali. The remaining strains may represent three new species of the Carnobacterium genus. All isolates were neutrophilic and halophilic psychrotrophs capable of fermenting various carbohydrates, organic acids, and alcohols. The identified metabolic properties of the isolated Carnobacterium strains suggest possible syntrophic interactions with other microorganisms in polar habitats. Some showed antimicrobial activity against food pathogens such as Listeria monocytogenes and human pathogens like Staphylococcus spp. Several isolates exhibited unique metabolic traits with potential biotechnological applications that could be more effectively exploited under less stringent technological conditions compared to thermophilic LAB strains, such as lower temperatures and reduced nutrient concentrations. Analysis of extrachromosomal genetic elements revealed 13 plasmids ranging from 4.5 to 79.5 kb in five isolates, featuring unique genetic structures and high levels of previously uncharacterized genes. This work is the first comprehensive study of the biochemical properties of both known and new Carnobacterium species and enhances our understanding of bacterial communities in harsh and highly selective polar soil ecosystems.

Abolishment of spawner-isolated mortality virus and where the remaining science leads.

In the late 1980s, there was histological and electron microscopy evidence for a parvovirus-like virus in Australian prawns. The data were consistent with infectious hypodermal and haematopoietic necrosis virus (IHHNV). However, these cases did not fit the then current paradigms of the known viruses and sequencing did not find any meaningful sequence homology. The virus was named spawner-isolated mortality virus (SMV; GenBank AF499102.1) in order to allow publication of the information about its occurrence to inform the scientific and aquacultural communities. This virus was present in the early years of mid-crop mortality syndrome (1993-1995). However, as time passed, nucleotide and protein databases have expanded and sequence investigation tools have become more cost effective. The sequence of the entity known as SMV is now shown to be of Carnobacterium divergens (CP016843.1). Therefore, the publications with regard to SMV have been assessed and a recommendation to abolish the name with the still valid science transferred to IHHNV and C. divergens.

Identification of novel Carnobacterium maltaromaticum strains in bone marrow samples of patients with acute myeloid leukemia using a metagenomic binning approach.

The aim of this study aimed to examine the existence of a bacterial metagenome in the bone marrow of patients with acute myeloid leukemia (AML). We re-examined whole-genome sequencing data from the bone marrow samples of seven patients with AML, four of whom were remitted after treatment, for metagenomic analysis. After the removal of human reads, unmapped reads were used to profile the species-level composition. We used the metagenomic binning approach to confirm whether the identified taxon was a complete genome of known or novel strains. We observed a unique and novel microbial signature in which Carnobacterium maltaromaticum was the most abundant species in five patients with AML or remission. The complete genome of C. maltaromaticum "BMAML_KR01," which was observed in all samples, was 100% complete with 8.5% contamination and closely clustered with C. maltaromaticum strains DSM20730 and SF668 based on single nucleotide polymorphism variations. We identified five unique proteins that could contribute to cancer progression and 104 virulent factor proteins in the BMAML_KR01 genome. To our knowledge, this is the first report of a new strain of C. maltaromaticum in patients with AML. The presence of C. maltaromaticum and its new strain in patients indicates an urgent need to validate the existence of this bacterium and evaluate its pathophysiological role.

Interdisciplinary approach to solve unusual mortalities in the European common frog (Rana temporaria) in two high-mountain ponds affected by climate change.

The global decline in amphibian populations is a major environmental issue. Chytridiomycosis, Ranaviruses and the red-leg syndrome have been identified in unusual mortality events. However, these infections do not account for all causes of declining amphibian populations. Moreover, several cases of amphibian mortality are difficult to solve without resorting to an interdisciplinary approach. Two cases of unusual mortality in Rana temporaria occurred at two high-mountain ponds (northwest Italy) in April and May 2021. Water and frog samples were analysed to understand the possible causes responsible for the unusual mortalities. Results of the main physicochemical (pH, conductivity, dissolved oxygen, chemical and biochemical oxygen demand) and nutrient (ammonia/ammonium, nitrite, nitrate, total phosphorus) parameters revealed a good condition of the water quality, with the absence of the main cyanotoxins (microcystins/nodularins). However, unseasonably high spring water temperatures were recorded in both ponds (12.73 °C and 14.21 °C for Frog Pond and Selleries Pond, respectively). Frogs (n = 50; snout-vent length: 7.0-9.8 cm; body mass: 85-123 g) collected from Frog Pond mainly presented bumps on the ventral cavity and dermal ulceration associated with the isolation of Carnobacterium maltaromaticum. On the other hand, frogs (n = 5; snout-vent length: 8.0-9.1 cm; body mass: 87-92 g) from Selleries Pond presented petechiae and dermal ulcerations on the rear limbs associated with the isolation of Aeromonas salmonicida and A. sobria. In both mortality events, the interdisciplinary approach revealed an association between frog mortalities and the isolation of bacteria. Isolated bacteria are considered opportunistic pathogens, and the high values of the water temperature has certainly led a stress on the frogs, favouring the spread of bacteria and the death of the frogs. Further studies are needed to assess the pathophysiological effects of the opportunistic bacteria here isolated, clarifying the interactions between emerging pathogens and climate change.

First isolation of Carnobacterium maltaromaticum from farmed Rainbow Trout in Virginia.

OBJECTIVE: Carnobacterium maltaromaticum is considered an emerging pathogen of salmonids in the United States and around the world. METHODS: Bacterial cultures obtained from the posterior kidney and skin of moribund Rainbow Trout Oncorhynchus mykiss from a commercial aquaculture facility in Virginia, USA, grew C. maltaromaticum, which was confirmed by additional phenotypic and molecular characterization. RESULT: A presumptive diagnosis based on the clinical signs, necropsy observations, histopathology, and bacterial cultures was bacterial septicemia due to C. maltaromaticum. CONCLUSION: This represents the first documentation of C. maltaromaticum in Rainbow Trout from Virginia.

Characterization of novel bacteriocin produced by bacteriocinogenic Carnobacterium maltaromaticum isolated from raw milk.

This study was designed to assess newly isolated bacteriocin-producing strain as potential food preservative. A bacteriocin producing lactic acid bacterium, named Carnobacterium maltaromatium KCA018, was screened from raw milk using deferred and spot-on-the-lawn assays. The crude cell free supernatant (CFS) was purified to obtain proteinaceous bacteriocin by ammonium sulfate precipitation (assigned as bacteriocin KCA) and tested for bacteriocin production, physical stability, antimicrobial activity, and bacteriocin-encoding gene detection. The growth curves of C. maltaromatium KCA018 reached late exponential phase after 15 h of incubation at 25 °C and 30 °C (Fig. 2). The maximum production of bacteriocin KCA was reached after 12 h of incubation at 25 °C, showing the antimicrobial activity of more than 3000 AU/ml against Listeria monocytogenes. The purified bacteriocin KCA was stable up to 67 °C for 30 min of exposure and between pH 4 and 7, showing more than 6000 AU/ml. The antibacterial activity of bacteriocin KCA was lost in the presence of pronase, proteinase K, and trypsin. Purified bacteriocin KCA showed higher antibacterial activity against Gram-positive bacteria than against Gram-negative bacteria. The CFS and purified bacteriocin KCA effectively inhibited the growth of L. monocytogenes ATCC 1911, E. faecalis ATCC 19433, and E. feacium ATCC 11576. The molecular weight of purified bacteriocin KCA was estimated at approximately 5 kDa. The positive amplification was observed for pisA and cbnBM1 with approximately between 100 and 200 bp. The newly identified bacteriocin can be a promising preservative for application in food.

Carnobacterium maltaromaticum associated with meningoencephalitis and otitis in stranded common thresher sharks (Alopias vulpinus).

Juvenile common thresher sharks (Alopias vulpinus) have been recently stranding along the California coastline. Using Illumina sequencing of the bacterial 16S rRNA gene along with necropsy, cytological, bacteriological, and histological techniques, we screened microbial communities and described lesions characterizing affected sharks with the purpose of identifying potential pathogen sources and pathologic processes. Histopathological assessment of moribund sharks revealed severe meningoencephalitis, as previously described in stranded salmon sharks (Lamna ditropis), along with inflammation of the inner ear and subcutaneous tissues surrounding the endolymphatic ducts. Furthermore, inflamed areas were characterized by the prevalence of Carnobacterium maltaromaticum, suggesting this bacterium as a potential pathogen that gains access to the inner ear through the endolymphatic ducts, with subsequent spread into the brain. The absence or low abundance of this bacterium in the spiral valve in both healthy and infected sharks suggests that Carnobacterium is not a commensal member of their digestive communities and the spiral valve is unlikely to be the source of the pathogen. Furthermore, phylogenetic analysis suggests that C. maltaromaticum strains isolated from diseased sharks have minimal genetic variation and differ from other strains originating from food or diseased teleosts. While a C. maltaromaticum-like organism has previously been associated with meningoencephalitis in salmon shark strandings, this is the first study to report common thresher shark strandings associated with C. maltaromaticum, involving the endolymphatic ducts as portals of entry to the brain.

Development of duplex qPCR targeting Carnobacterium maltaromaticum and Vagococcus salmoninarum.

In November 2018, Vagococcus salmoninarum was identified as the causative agent of a chronic coldwater streptococcosis epizootic in broodstock brook trout (Salvelinus fontinalis) at the Iron River National Fish Hatchery in Wisconsin, USA. By February 2019, the epizootic spread to adjacent raceways containing broodstock lake trout (Salvelinus namaycush), whereby fish were found to be coinfected with Carnobacterium maltaromaticum and V. salmoninarum. To differentiate these two pathogens and determine the primary cause of the lake trout morbidity, a quantitative real-time PCR (qPCR) was developed targeting the C. maltaromaticum phenylalanyl-tRNA synthase alpha subunit (pheS) gene. The qPCR was combined with a V. salmoninarum qPCR, creating a duplex qPCR assay that simultaneously quantitates C. maltaromaticum and V. salmoninarum concentrations in individual lake trout tissues, and screens presumptive isolates from hatchery inspections and wild fish from national fish hatchery source waters throughout the Great Lakes basin. Vagococcus salmoninarum and C. maltaromaticum were co-detected in broodstock brook trout from two tribal hatcheries and C. maltaromaticum was present in wild fish in source waters of several national fish hatcheries. This study provides a powerful new tool to differentiate and diagnose two emerging Gram-positive bacterial pathogens.

Effects of Peroxyacetic Acid Spray and Storage Temperature on the Microbiota and Sensory Properties of Vacuum-Packed Subprimal Cuts of Meat.

We investigated the impact of peroxyacetic acid (PAA; 200 ppm) spray on the microbiota and shelf life of commercial, vacuum-packed beef stored at chiller temperatures. Ribeye cuts (n = 147) were collected from a local beef plant on the day of production for two consecutive days, with one set collected at the start of work with the PAA spray nozzles turned off (control) and during routine production with the PAA spray nozzles turned on (PAA) each day. Packs were stored at 4, 2, and -1°C for up to 34, 104, and 180 days and sampled at appropriate intervals for sensory assessment, microbial enumeration, and microbial profiling by 16S rRNA gene amplicon analysis. Treatment with PAA did not affect the initial meat pH, the initial numbers of total aerobes, lactic acid bacteria, or Enterobacteriaceae (P > 0.05) before storage; however, it delayed the onset of spoilage by 7, 21, and 54 days at 4, 2, and -1°C, respectively. Square-root models of the variation of growth rate with temperature indicated lactic acid bacteria grew faster and Enterobacteriaceae grew slower on PAA-treated than on untreated meat. Negative associations between pH and deterioration of meat during storage were observed for PAA-treated meat. During storage, the microbiota were primarily dominated by Carnobacterium and Lactobacillus/Lactococcus on control meat but by Leuconostoc on PAA-treated meat. Serratia, Yersinia, and Clostridium were identified by linear discriminant effect size analysis as biomarkers for control meat; Clostridium was found in high abundance in samples that had the highest spoilage scores.IMPORTANCE The findings of this study show that PAA solutions applied at low concentrations under commercial settings positively modulated the meat microbiota. It did not have bactericidal effects for beef subprimals with very low microbial loads. However, it differentially impacted the members of the microbiota, which resulted in delayed onset of spoilage of vacuum-packed beef subprimal stored at all three temperatures (4, 2, and -1°C). This differential impact could be through one or a combination of the following factors: favoring the growth of lactic acid bacteria, which may in turn exert a competitive exclusion that might be due to production of antimicrobial compounds such as organic acids and bacteriocins; exerting synergistic antimicrobial effects with low temperatures against members of Enterobacteriaceae; and direct or indirect inhibitory effects against members of the clostridia. These findings not only advance our understanding of the microbial ecology of vacuum-packed meat stored at chiller temperatures but also suggest that bacteriostatic concentrations of antimicrobial interventions can be explored for shelf-life extension.

Carnobacterium inhibens isolated in blood culture of an immunocompromised, metastatic cancer patient: a case report and literature review.

BACKGROUND: Carnobacterium species are lactic acid-producing Gram-positive bacteria that have been approved by the US Food and Drug Administration and Health Canada for use as a food bio-preservative. The use of live bacteria as a food additive and its potential risk of infections in immunocompromised patients are not well understood. CASE PRESENTATION: An 81-year-old male with a history of metastatic prostate cancer on androgen deprivation therapy and chronic steroids presented to our hospital with a 2-week history of productive cough, dyspnea, altered mentation, and fever. Extensive computed tomography imaging revealed multifocal pneumonia without other foci of infection. He was diagnosed with pneumonia and empirically treated with ceftriaxone and vancomycin. Blood cultures from admission later returned positive for Carnobacterium inhibens. He achieved clinical recovery with step-down to oral amoxicillin/clavulanic acid for a total 7-day course of antibiotics. CONCLUSIONS: This is the fourth reported case of bacteremia with Carnobacterium spp. isolated from humans. This case highlights the need to better understand the pathogenicity and disease spectrum of bacteria used in the food industry for bio-preservation, especially in immunocompromised patients.

Assessment of the spoilage microbiota in minced free-range chicken meat during storage at 4 C in retail modified atmosphere packages.

This study assessed the evolution of spoilage microbiota in association with the changes in pH and concentrations of lactic and acetic acids in retail oxygen-free modified atmosphere (30:70 CO2/N2) packages (MAP) of minced free-range chicken meat during storage at 4 °C for 10 days. MAP retarded growth of spoilage lactic acid bacteria (LAB) below 6.5 log cfu/g and fully suppressed growth of pseudomonads, enterobacteria, enterococci, staphylococci and yeasts. Two distinct Latilactobacillus sakei strain biotypes were predominant and Leuconostoc carnosum, Carnobacterium divergens, Latilactobacillus fuchuensis and Weissella koreensis were subdominant at spoilage. The chicken meat pH ranged from 5.8 to 6.1. l-lactate (832 mg/100 g on day-0) decreased slightly on day-7. d-lactate remained constantly below 20 mg/100 g, whereas acetate (0-59 mg/100 g) increased 5-fold on day-7. All MAP samples developed off-odors on day-7 and a strong 'blown-pack' sulfur-type of spoilage on day-10. However, neither the predominant Lb. sakei nor other LAB or gram-negative isolates formed H2S in vitro, except for C. divergens.

Metatranscriptomic analysis of modified atmosphere packaged poultry meat enables prediction of Brochothrix thermosphacta and Carnobacterium divergens in situ metabolism.

In this study, in situ-expressed metabolic routes of Brochothrix (B.) thermosphacta and Carnobacterium (C.) divergens were evaluated based on a metatranscriptomic dataset from bacteria growing on MAP chicken meat (O2/CO2; N2/CO2). Both species exhibited no (C. divergens) or minor transcription regulation (B. thermosphacta) within their main metabolic routes in response to different atmospheres. Both employ pathways related to glucose and ribose. Gluconeogenesis from lipid-borne glycerol is active in the progressing lack of carbohydrates. Pyruvate fates in both species comprise lactate, ethanol, acetate, CO2, formate, C4-compounds and H2O2 (only B. thermosphacta). Both species express genes for a minimal aerobic respiratory chain, but do not possess the genetic setting for a functional citric acid cycle. While products of carbohydrate and glycerol metabolism display mild to medium sensorial off-characteristics, predicted end products of their amino acid metabolism comprise, e.g., isobutyrate and isovalerate (B. thermosphacta) or cadaverine and tyramine (C. divergens) as potent spoilage compounds.

Discovering microbiota and volatile compounds of surströmming, the traditional Swedish sour herring.

In this study, the microbiota of ready-to-eat surströmming from three Swedish producers were studied using a combined approach. The pH values of the samples ranged between 6.67 ± 0.01 and 6.98 ± 0.01, whereas their aw values were between 0.911 ± 0.001 and 0.940 ± 0.001. The acetic acid concentration was between 0.289 ± 0.009 g/100 g and 0.556 ± 0.036 g/100 g. Very low concentrations of lactic acid were measured. Viable counting revealed the presence of mesophilic aerobes, mesophilic lactobacilli and lactococci as well as halophilic lactobacilli and lactococci, coagulase-negative staphylococci, halophilic aerobes and anaerobes. Negligible counts for Enterobacteriaceae, Pseudomonadaceae and total eumycetes were observed, whereas no sulfite-reducing anaerobes were detected. Listeria monocytogenes and Salmonella spp. were absent in all samples. Multiplex real-time PCR revealed the absence of the bont/A, bont/B, bont/E, bont/F, and 4gyrB (CP) genes, which encode botulinic toxins, in all the samples analyzed. Metagenomic sequencing revealed the presence of a core microbiota dominated by Halanaerobium praevalens, Alkalibacterium gilvum, Carnobacterium spp., Tetragenococcus halophilus, Clostridiisalibacter spp. and Porphyromonadaceae. Psychrobacter celer, Ruminococcaceae, Marinilactibacillus psychrotolerans, Streptococcus infantis and Salinivibrio costicola were detected as minor OTUs. GC-MS analysis of volatile components revealed the massive presence of trimethylamine and sulphur compounds. Moreover, 1,2,4-trithiolane, phenols, ketones, aldehydes, alcohols, esters and long chain aliphatic hydrocarbons were also detected. The data obtained allowed pro-technological bacteria, which are well-adapted to saline environments, to be discovered for the first time. Further analyses are needed to better clarify the extent of the contribution of either the microbiota or autolytic enzymes of the fish flesh in the aroma definition.

Genome-wide comparison of Carnobacterium maltaromaticum derived from diseased fish harbouring important virulence-related genes.

Although Carnobacterium maltaromaticum has been used as a probiotic in fish, it was reported to cause disease for the first time in Korea. The objective of this study was to understand the differences between pathogenic and non-pathogenic strains. Pathogenicity was tested by challenging rainbow trout with C. maltaromaticum ATCC35586 and 18ISCm isolated from diseased fish, and DSM20342 isolated from a dairy product. We also compared 24 genomes of C. maltaromaticum strains plus the genome of our isolate 18ISCm sequenced in this study. Only the strains from diseased fish caused high mortality with severe histopathological changes. Although all strains shared more than 90% of Ko_id, wecC and xtmA were found only in strains from diseased fish. Interestingly, only strains from diseased fish harboured two wecC paralogs involved in the production of D-mannosaminuronic acid which is a major component of a well-known virulence factor, teichuronic acid. Two wecC paralogs of 18ISCm were increased when they were co-cultured with trout blood cells, suggesting that wecC genes might play a role in virulence. The results of this study show that strains isolated from diseased fish are different from strains derived from food in terms of pathogenicity to fish and the presence of virulence-related genes.

Complementary Antibacterial Effects of Bacteriocins and Organic Acids as Revealed by Comparative Analysis of Carnobacterium spp. from Meat.

Carnobacterium maltaromaticum and Carnobacterium divergens are often predominant in the microbiota of vacuum-packaged (VP) meats after prolonged storage at chiller temperatures, and more so in recent studies. We investigated the antibacterial activities of C. maltaromaticum and C. divergens (n = 31) from VP meats by phenotypic characterization and genomic analysis. Five strains showed antibacterial activities against Gram-positive bacteria in a spot-lawn assay, with C. maltaromaticum strains having an intergeneric and C. divergens strains an intrageneric inhibition spectrum. This inhibitory activity is correlated with the production of predicted bacteriocins, including carnobacteriocin B2 and carnolysin for C. maltaromaticum and divergicin A for C. divergens The supernatants of both species cultured in meat juice medium under anaerobic conditions retarded the growth of most Gram-positive and Gram-negative bacteria in broth assay in a strain-dependent manner. C. maltaromaticum and C. divergens produced formate and acetate but not lactate under VP meat-relevant conditions. The relative inhibitory activity by Carnobacterium strains was significantly correlated (P < 0.05) to the production of both acids. Genomic analysis revealed the presence of genes required for respiration in both species. In addition, two clusters of C. divergens have an average nucleotide identity below the cutoff value for species delineation and thus should be considered to be two subspecies. In conclusion, both bacteriocins and organic acids are factors contributing significantly to the antibacterial activity of C. maltaromaticum and C. divergens under VP meat-relevant conditions. A few Carnobacterium strains can be explored as protective cultures to extend the shelf life and improve the safety of VP meats.IMPORTANCE The results of this study demonstrated that both bacteriocins and organic acids are important factors contributing to the antibacterial activities of Carnobacterium from vacuum-packaged (VP) meats. This study demonstrated that formate and acetate are the key organic acids produced by Carnobacterium and demonstrated their association with the inhibitory activity of carnobacteria under VP meat-relevant storage conditions. The role of lactate, on the other hand, may not be as important as previously believed in the antimicrobial activities of Carnobacterium spp. on chilled VP meats. These findings advance our understanding of the physiology of Carnobacterium spp. to better explore their biopreservative properties for chilled VP meats.

Carnobacterium antarcticum sp. nov., a psychrotolerant, alkaliphilic bacterium isolated from sandy soil in Antarctica.

A novel, alkaliphilic, psychrotolerant, facultative anaerobe, designated CP1T, was isolated from sandy soil near the Davis Station in Antarctica. The short-rod-shaped cells displayed Gram-positive staining and did not form spores. Strain CP1T was able to grow at temperatures between 4 and 36 °C, pH 6.0-9.5, and in the presence of up to 5.0 % (w/v) NaCl. 16S rRNA gene and multilocus (pheS, rpoA, and atpA) sequence analysis revealed Carnobacterium mobile DSM 4848T and Carnobacterium iners LMG 26642T as the closest relatives (97.4 and 97.1 % 16S rRNA gene sequence similarity, respectively). The genomic G+C content was 38.1 mol%, and DNA-DNA hybridization with DSM 4848T revealed 32.4±3.4 % similarity. The major fatty acid components were C14 : 0 and C16 : 1ω9c. The cell wall contained meso-diaminopimelic acid and was of peptidoglycan type A1γ. Based on physiological, genotypic and biochemical characteristics, strain CP1T represents a novel species of the genus Carnobacterium for which the name Carnobacterium antarcticum sp. nov. is proposed. The type strain is CP1T (=DSM 103363T=CGMCC 1.15643T).

Farm and abattoir sources of Carnobacterium species and implications for lamb meat spoilage.

AIMS: To investigate the transmission route of Carnobacterium from the farm environment to the meat-manufacturing plant and potential risk for meat spoilage. METHODS AND RESULTS: A sheep farm-level survey of Carnobacterium, consisting of 150 environmental and animal (no 100) associated samples, was carried out on two farms. A further 20 lamb carcass samples were taken from an abattoir servicing one of the farms. The majority of Carnobacterium maltaromaticum isolates were associated with fleece followed by hard sheep contact surfaces, rectal-anal mucosal swabs and carcasses. Enterobacterial repetitive intergenic consenus PCR (ERIC-PCR) profiling revealed four distinct ERIC types. Each ERIC type was found on both farms, three of which were also found on lamb carcasses. CONCLUSIONS: Enterobacterial repetitive intergenic consenus PCR was effective at demonstrating within-species variability in C. maltaromaticum. This study provides initial information showing that farm sources maybe an important transmission route of Carnobacterium for contamination of lamb carcasses and subsequently the meat processing environment. SIGNIFICANCE AND IMPACT OF THE STUDY: Data on distribution, diversity, sources and transmission routes for meat product contamination is limited for spoilage bacteria. This study highlights the importance of good hygienic slaughter practices and cleaning routines to remove accumulated detritus from the handling of animals that may lead to cross-contamination.

Use of Carnobacterium spp protective culture in MAP packed Ricotta fresca cheese to control Pseudomonas spp.

Ricotta fresca is a whey cheese susceptible of secondary contamination, mainly from Pseudomonas spp. The extension of the shelf life of refrigerated ricotta fresca could be obtained using protective cultures inhibiting the growth of this spoilage microorganism. A commercial biopreservative, Lyofast CNBAL, comprising Carnobacterium spp was tested against Pseudomonas spp. The surface of ricotta fresca samples were inoculated either with Pseudomonas spp or Pseudomonas and Carnobacterium spp. Samples were MAP packed, stored at 4 °C and analyzed the day of the inoculum and 7, 14 and 21 days after the contamination. Microbiological analyses included total bacterial count, mesophilic lactic acid bacteria, Enterobacteriaceae, Pseudomonas spp, Listeria monocytogenes, moulds and yeasts. Pseudomonas mean initial contamination level was comparable in blank and artificially inoculated samples, respectively with values of 2.15 ±â€¯0.21 and 2.34 ±â€¯0.26 log cfu g-1. Carnobacterium spp. significantly reduced the growth of Pseudomonas spp respectively of 1.28 log and 0.83 log after 14 and 21 days of refrigerated storage. Intrinsic properties and physico-chemical composition were also investigated. Limited variation of pH was observed in samples inoculated with the protective cultures, indicating low acidification properties of Carnobacterium spp. Instead, no significant differences were observed for aW, moisture, fat and proteins during storage and between inoculated and control samples.

Testing commercial biopreservative against spoilage microorganisms in MAP packed Ricotta fresca cheese.

Ricotta fresca cheese is susceptible to secondary contamination and is able to support the growth of pathogens or spoilage psychotrophic bacteria during storage. The aim of the present study was to evaluate which among three commercial biopreservatives was suitable to be used to control the growth of spoilage microorganisms in sheep's milk MAP ricotta fresca cheese. 144 Ricotta fresca cheese samples were inoculated either with the bioprotective culture Lyofast FPR 2 (including Enterococcus faecium, Lactobacillus plantarum e Lactobacillus rhamnosus) or Lyofast CNBAL (Carnobacterium spp) or the fermentate MicroGARD 430. Not inoculated control and experimental ricotta were MAP packed (30% CO2 and 70% N2) and stored at 4 °C. Triplicate samples were analyzed after 5 h and 7, 14 and 21 days after inoculation for total bacterial count, mesophilic lactic acid bacteria, Enterobacteriaceae, Pseudomonas spp, Listeria monocytogenes, moulds and yeasts. Among the tested biopreservatives only Carnobacterium spp was able to control Pseudomonas spp and Enterobacteriaceae. The maximum reduction in the concentration of Pseudomonas spp and Enterobacteriaceae was respectively 1.93 and 2.66 log10 cfu/g, observed 14 days after production. Therefore, Carnobacterium spp was selected as the culture of choice to conduct a challenge study against Pseudomonas spp.

Genes associated to lactose metabolism illustrate the high diversity of Carnobacterium maltaromaticum.

The dairy population of Carnobacterium maltaromaticum is characterized by a high diversity suggesting a high diversity of the genetic traits linked to the dairy process. As lactose is the main carbon source in milk, the genetics of lactose metabolism was investigated in this LAB. Comparative genomic analysis revealed that the species C. maltaromaticum exhibits genes related to the Leloir and the tagatose-6-phosphate (Tagatose-6P) pathways. More precisely, strains can bear genes related to one or both pathways and several strains apparently do not contain homologs related to these pathways. Analysis at the population scale revealed that the Tagatose-6P and the Leloir encoding genes are disseminated in multiple phylogenetic lineages of C. maltaromaticum: genes of the Tagatose-6P pathway are present in the lineages I, II and III, and genes of the Leloir pathway are present in the lineages I, III and IV. These data suggest that these genes evolved thanks to horizontal transfer, genetic duplication and translocation. We hypothesize that the lac and gal genes evolved in C. maltaromaticum according to a complex scenario that mirrors the high population diversity.