Characterization of Staphylococcus xylosus and Staphylococcus carnosus isolated from Slovak meat products

Mycotoxins in meat products

Mycotoxin presence in meat products is principally due to the development of toxigenic moulds during ripening, which concretely affect the dry-cured ones. Ochratoxin A (OTA) is the most prevalent mycotoxin in dry-cured hams and fermented sausages. Apart from collecting information on the main toxigenic moulds in dry-cured meat products, the objective of this review is to compile data about the mycotoxin prevalence and the tools for their mitigation. Although no very extensive studies have been performed on the mycotoxin occurrence in such products, much research has been conducted over the last 15 years, particularly in the European Mediterranean countries. Large differences in OTA incidence and amount have been reported, which can be due to differences in the processing followed, the climatic conditions of the producing region, the mould population present or the used detection method. Nevertheless, most of the mean and maximum OTA values observed in dry-cured meat products are above the maximum level of 1 μg/kg recommended officially for pork products in Italy. Aflatoxin B1, cyclopiazonic acid, sterigmatocystin and citrinin are only occasionally reported from dry-cured meat products. To control mycotoxin contamination, manufacturers have several strategies available, with the biopreservation ones being the most appropriate, since the modification of environmental parameters is not feasible, especially in products with long ripening. Native microorganisms alone or in combination with plant extracts are sustainable biopreservatives with a special interest in dry-cured meat products to mitigate the mycotoxin contamination. All these strategies are extensively described in this review, with special attention paid to OTA.

Genomic exploration of the fermented meat isolate Staphylococcus shinii IMDO-S216 with a focus on competitiveness-enhancing secondary metabolites

BACKGROUND

Staphylococcus shinii appears as an umbrella species encompassing several strains of Staphylococcus pseudoxylosus and Staphylococcus xylosus. Given its phylogenetic closeness to S. xylosus, S. shinii can be found in similar ecological niches, including the microbiota of fermented meats where the species may contribute to colour and flavour development. In addition to these conventional functionalities, a biopreservation potential based on the production of antagonistic compounds may be available. Such potential, however, remains largely unexplored in contrast to the large body of research that is available on the biopreservative properties of lactic acid bacteria. The present study outlines the exploration of the genetic basis of competitiveness and antimicrobial activity of a fermented meat isolate, S. shinii IMDO-S216. To this end, its genome was sequenced, de novo assembled, and annotated.

RESULTS

The genome contained a single circular chromosome and eight plasmid replicons. Focus of the genomic exploration was on secondary metabolite biosynthetic gene clusters coding for ribosomally synthesized and posttranslationally modified peptides. One complete cluster was coding for a bacteriocin, namely lactococcin 972; the genes coding for the pre-bacteriocin, the ATP-binding cassette transporter, and the immunity protein were also identified. Five other complete clusters were identified, possibly functioning as competitiveness factors. These clusters were found to be involved in various responses such as membrane fluidity, iron intake from the medium, a quorum sensing system, and decreased sensitivity to antimicrobial peptides and competing microorganisms. The presence of these clusters was equally studied among a selection of multiple Staphylococcus species to assess their prevalence in closely-related organisms.

CONCLUSIONS

Such factors possibly translate in an improved adaptation and competitiveness of S. shinii IMDO-S216 which are, in turn, likely to improve its fitness in a fermented meat matrix.

Genomic and metabolic properties of Staphylococcus gallinarum FCW1 MCC4687 isolated from naturally fermented coconut water towards GRAS assessment

Staphylococcus gallinarum FCW1 was isolated from naturally fermented coconut-water and identified by biochemical and molecular methods. Probiotic characterization and safety assessment were conducted through a series of in vitro tests. A high survival rate was observed when the strain was tested for resistance to bile, lysozyme, simulated gastric and intestinal fluid, phenol, and different temperature and salt concentrations. The strain showed antagonism against some pathogens, was susceptible to all antibiotics tested except penicillin, and showed no hemolytic and DNase activity. Hydrophobicity, autoaggregation, biofilm formation, and antioxidation tests indicated that the strain possessed a high adhesive and antioxidant ability. Enzymatic activity was used to evaluate the metabolic capacities of the strain. In-vivo experiment on zebrafish was performed to check its safety status. The whole-genome sequencing indicated that the genome contained 2,880,305 bp with a GC content of 33.23%. The genome annotation confirmed the presence of probiotic-associated genes and genes for oxalate degradation, sulfate reduction, acetate metabolism, and ammonium transport in the FCW1 strain, adding to the theory that this strain may be helpful in treating kidney stones. This study revealed that the strain FCW1 might be an excellent potential probiotic in developing fermented coconut beverages and treating and preventing kidney stone disease.

Characterization of indigenous coagulase-negative staphylococci isolated from Chinese spontaneously fermented meat products

Technological, safety-related and volatile properties were analyzed in coagulase-negative staphylococci (CNS) isolates from Chinese spontaneously fermented meat products. A total of 107 CNS isolates were identified via 16 S rRNA sequencing, and the most recovered species were S. saprophyticus (53.3 %), S. edaphicus (12.1 %), and S. epidermidis (10.3 %). Among them, 58 CNS isolates belonging to 9 species were selected with higher activities of catalase, nitrate reductase, proteolysis, and lipolysis, as well as higher tolerance to stressful environmental conditions. Then, 7 CNS isolates belonging to 4 species were further selected based upon excellent technological characteristics, lack of hemolysis and antibiotic resistance, and a low production of biogenic amines. The volatile profiles of these 7 strains cultivated in pork broth was determined. S. casei No. 1 produced significant amounts of phenethyl alcohol, geraniol, and 3-methyl-butanol. S. xylosus No. 120 produced the highest amount of methyl ketones with the potential to provide dry-cured odor of fermented meats. The volatile profile was highly strain dependent. Several CNS identified in this study have the potential to be used as the starter cultures for fermented meat products.

Inhibition of histamine accumulation by novel histamine-degrading species of Staphylococcus sp. isolated from goats and sheep milk

Histamine is an active amine compound that occurs in various fermented foods that may cause adverse effects on the human health. Certain microorganisms are able to degrade histamine by an oxidative deamination reaction. Therefore, the present study aimed to quantify histamine-forming and/or -degrading activity of the isolates derived from milk of goat and sheep herds, in Iran, by the capillary zone electrophoresis (CZE) method; and we evaluated the molecular characteristics of staphylococcal isolates. Among 243 staphylococcal isolates, 29 histamine-degrading bacteria were identified. One of these isolates, identified as Staph. epidermidis, No. 605, exhibited the highest activity compared to others, degrading available histamine to 58.33% within 24 h. By polymerase chain reaction (PCR) analysis, the isolate, No. 605 that exhibited remarkable histamine-degrading activity lacked the genes encoding coagulase and DNase, nor did it harbor any of the five classical enterotoxin genes. This is the first report to show that seven Staphylococcus species, including Staph. chromogenes, Staph. aureus, Staph. haemolyticus, Staph. epidermidis, Staph. pseudintermedius, Staph. agnetis, and Staph. hyicus, were able to degrade histamine, which were hitherto not known to have this capacity. Therefore, histamine-degrading activity is a definite criterion to introduce fermenting organisms able to decrease histamine content in different food products.

Effect of cranberry pomace on the physicochemical properties and inactivation of Salmonella during the manufacture of dry fermented sausages

The effect of cranberry pomace (CP) incorporation on S. enterica serovars inactivation, starter culture population, and physicochemical properties of sausages during the manufacture of dry fermented sausages (DFS) was studied. Sausages containing a five-strain cocktail of S. enterica serovars at 7-log CFU/g, with different levels of CP (control, 0%; low, 0.55%; medium, 1.70%; high, 2.25% wt/wt), or liquid lactic acid (0.33% vol/wt, LA) were subjected to typical fermentation and drying conditions. A significant (P < 0.05) reduction in initial pH was observed in all CP treatments on day 0 as a result of CP native acidity. All treatments except low CP showed a significantly lower pH than the control throughout the study. Water activity (a_w) was not significantly affected by CP level during fermentation. However, sausages containing medium and high CP levels showed a significantly lower final product a_w than the control. DFS with CP exhibited a significantly (P < 0.05) faster and greater Salmonella inactivation during the first 5 days; reduction rate and level directly correlated to CP level. In the presence of medium and high levels of CP, Staphylococcus spp. growth was suppressed, while Lactobacillus spp. and Pediococcus spp. exhibited a stimulatory response. All treatments except low CP had no significant effect on product chemical composition, and Moisture Protein ratio (MPr). Low CP level yielded DFS with a slightly higher (P < 0.05) moisture content and MPr. Medium and high CP levels resulted in darker, duller and redder DFS with a softer texture. Findings suggest that low CP levels can be utilized by DFS manufacturers as a natural functional ingredient to further minimize the risk associated with Salmonella during DFS production without altering final product characteristics.

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Cranberry pomace inclusion in dry fermented sausages enhances Salmonella inactivation.

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Increase in cranberry pomace levels negatively affects quality of dry fermented sausages.

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Cranberry pomace inclusion does not affect growth of starter culture bacteria.

Screening and optimization of a nitrate reductase-producing Staphylococcus simulans UV-11 and its application

A strain of Staphylococcus simulans D14 (S. simulans D14) showed the highest nitrate reductase activity (NRA) of 4.52 mM NO₂⁻/mg dry weight by the spectrophotometric method, which was screened from traditional Chinese sausage. When the UV mutagenesis time was 25 s, the positive mutation rate was the highest at 26.60%. The NRA of the obtained positive mutant UV-11 was 9.21 mM NO₂⁻/mg dry weight, and the activity was found to be 1.04-fold higher than that of the original strain S. simulans D14. A Plackett–Burman design (PBD) was employed to screen the significant variables pH, KNO₃ (%) and incubation time (h), and response surface methodology (RSM) was used to optimize the significant variables using a Box–Behnken design (BBD). The results showed that the NRA of S. simulans UV-11 was 15.22 mM NO₂⁻/mg dry weight under optimum conditions of 37 °C, pH 6.5, incubation time 15 h, KNO₃ 0.045%, NaCl 5%, NaNO₂ 0.015%, peptone 1%, and D–mannitol 1%, which increased by 65.2% compared with the unoptimized medium. Natural curing agents (containing 10⁷ CFU/g S. simulans UV-11 under optimal conditions and 1.40% celery powder, T2) were added to the cured meat model. T2 produced significantly lighter and redder signals than the control group (C) and the addition of 150 ppm NaNO₂ group (T1). The thiobarbituric acid reactive substance (TBARS) of T2 was 2.30 mg malonaldehyde/kg product and residual nitrite of T2 was 7.1 ppm after 14 days of storage,which were lower than those groups of C and T1. Taking into account the results of cured meat models, S. simulans UV-11 could be selected as a potential starter culture for the processing of natural meat products.

Autochthonous Probiotics in Meat Products: Selection, Identification, and Their Use as Starter Culture

The increasing demand for functional food is pushing the food industry to innovate the conventional and well-known foods. Producing functional foods, especially with probiotics in meat products, is an intricate and multistage task that involves: the selection of microorganisms with probiotic potential, the identification at strain level, and the evaluation of probiotic strains in the processing of meat products. The resistance to digestion, followed by the successful colonization in the small intestine and the safety are the main criteria used to select and identify (at strain level) a probiotic, as reported in recent studies about the autochthonous microbiota of meat products. Further insertion (as starter culture) in a meat system for fermentation is the simplest approach to obtain a probiotic meat product. Among the innumerous microorganisms naturally found in meat products, lactic acid bacteria (LAB) play a central role by fitting in both probiotic and meat products processing criteria.

Synergistic effects of Lactobacillus plantarum and Staphylococcus carnosus on animal food components

Introduction. Various cultures of microorganisms have recently been used to accelerate technological processes. In this regard, it appears highly relevant to study the action of beneficial microorganisms on the components of food systems. Study objects and methods. The study objects included a model mixture of beef muscle and pork fat tissue with 2% salt, as well as a model protein. Lactobacillus plantarum and Staphylococcus carnosus were used in an amount of 1×107 CFU/g of raw material. The compositions of free amino and fatty acids, carbohydrates, and other components were analyzed by liquid and gas chromatography with mass-selective detection. Results and discussion. We studied the effect of L. plantarum and S. carnosus on protein, lipid, and carbohydrate components of food systems based on animal raw materials. We found that the combined effect of the cultures was by 25% as effective as their individual use at 4×109 CFU/kg of raw material. The three-week hydrolysis of proteins to free amino acids was almost a third more effective than when the cultures were used separately. The synergistic effect of L. plantarum and S. carnosus on fat components was not detected reliably. Free monosaccharides formed more intensively when the cultures were used together. In particular, the amount of free lactose almost doubled, compared to the cultures’ individual action. Conclusion. We described culture-caused quantitative changes in the main components of animal-based food systems: amino acids, fatty acids, carbohydrates, and basic organic compounds. Also, we identified substances that can affect the taste and aroma of final products when the cultures are used together or separately. These results make it possible to obtain products with a wide variety of sensory properties.

Selection and Evaluation of Staphylococcus xylosus as a Biocontrol Agent against Toxigenic Moulds in a Dry-Cured Ham Model System

Toxigenic moulds can develop on the surface of dry-cured meat products during ripening due to their ecological conditions, which constitutes a risk for consumers. A promising strategy to control this hazard is the use of antifungal microorganisms usually found in these foods. However, to date, the effectiveness of gram-positive catalase-positive cocci (GCC+) has not been explored. The aim of this work was to select GCC+ isolates with antifungal activity to study its effectiveness in a dry-cured ham model system at the environmental conditions reached during the ripening. Forty-five strains of GCC+ were evaluated and the isolate Staphylococcus xylosus Sx8 was selected to assess its efficacy at two different concentrations (106 and 104 cfu/mL) against Penicillium nordicum, Aspergillus flavus, Aspergillus parasiticus, and Penicillium griseofulvum at 15, 20, and 25 °C. The results showed that the inoculation of 106 cfu/mL of S. xylosus completely inhibited the growth of most fungi. In addition, in the presence of this strain at 104 cfu/mL, a significant reduction in fungal growth and mycotoxins production was observed at the three temperatures studied. In conclusion, S. xylosus Sx8 possesses great potential as a biological agent to control toxigenic moulds in dry-cured meat products.

Exploring the Ambiguous Status of Coagulase-Negative Staphylococci in the Biosafety of Fermented Meats: The Case of Antibacterial Activity Versus Biogenic Amine Formation

A total of 332 staphylococcal strains, mainly isolated from meat, were screened for antibacterial activity. Eighteen strains exhibited antibacterial activity towards species within the same genus. These antibacterial strains were further screened against Clostridium botulinum, to assess their potential as anticlostridial starter cultures for the development of fermented meat products without added nitrate or nitrite. Only Staphylococcus sciuri IMDO-S72 had the ability to inhibit all clostridial strains tested, whilst displaying additional activity against Bacillus cereus, Listeria monocytogenes and Staphylococcus aureus. Apart from their potential as bioprotective cultures, the staphylococcal collection was also screened for biogenic amine production, as these compounds may compromise food quality. To this end, ultra-high-performance liquid chromatography coupled to tandem mass spectrometry (UPLC-MS/MS) was applied. A low incidence of biogenic amine production was found, with tyramine and β-phenylethylamine being the most prevalent ones. Concentrations remained relatively low (< 52 mg/L) after a prolonged incubation period, posing no or little threat towards food safety. Taken together, S. sciuri IMDO-S72 could serve as an interesting candidate for the bioprotection of fermented meats as it showed promising antibacterial activity as well as absence of biogenic amine production.

Isolation and Screening of Staphylococcus Xylosus P2 from Chinese Bacon: A Novel Starter Culture in Fermented Meat Products

A novel coagulase negative staphylococci strain as flavor agent for the processing of fermented meat products, Staphylococcus xylosus P2, was screened from Chinese bacon. It was identified on the basis of morphology and 16S rDNA sequence analysis. Its proteolytic, lipolytic and nitrate reductive activities were evaluated. And its growth ability at different temperatures, pH, sodium chloride, sodium nitrite concentrations, biogenic amine and pigment were investigated or detected. Furthermore, the fermentation evaluation with S. xylosus P2 as starter culture was carried out. The result showed that the fermented beef jerky was more attractive on the color, odor, texture, tasty and overall acceptability. It indicated that S. xylosus P2 would be a good starter culture for fermented meat products (jerky).

Assessment of Antibiotic Susceptibility within Lactic Acid Bacteria and Coagulase-Negative Staphylococci Isolated from Hunan Smoked Pork, a Naturally Fermented Meat Product in China

The aim of this study was to evaluate the antibiotic susceptibility of lactic acid bacteria (LAB) and coagulase-negative staphylococci (CNS) strains isolated from naturally fermented smoked pork produced in Hunan, China. A total of 48 strains were isolated by selective medium and identified at the species level by 16S rRNA gene sequencing as follows: Staphylococcus carnosus (23), Lactobacillus plantarum (12), Lactobacillus brevis (10), Lactobacillus sakei (1), Weissella confusa (1), and Weissella cibaria (1). All strains were typed by RAPD-PCR, and their susceptibility to 15 antibiotics was determined and expressed as the minimum inhibitory concentration (MIC) using agar dilution method. High resistance to penicillin G, streptomycin, gentamycin, vancomycin, chloramphenicol, norfloxacin, ciprofloxacin, kanamycin, and neomycin was found among the isolates. All the strains were sensitive to ampicillin, while the susceptibility to tetracycline, oxytetracycline, erythromycin, lincomycin, and roxithromycin varied. The presence of relevant resistance genes was investigated by PCR and sequencing, with the following genes detected: str(A), str(B), tet(O), tet(M), ere(A), and catA. Eleven strains, including 3 S. carnosus, 6 L. plantarum, and 2 L. brevis, harbored more than 3 antibiotic resistance genes. Overall, multiple antibiotic resistance patterns were widely observed in LAB and S. carnosus strains isolated from Hunan smoked pork. Risk assessment should be carried out with regard to the safe use of LAB and CNS in food production.

PRACTICAL APPLICATION

We evaluated the antibiotic resistance of lactic acid bacteria and coagulase-negative staphylococci strains isolated from Chinese naturally fermented smoked pork. Our results may provide important data on establishing breakpoint standards for LAB and CNS and evaluating the safety risk of these strains for commercial use.

Microbial occurrence and antibiotic resistance in ready-to-go food items

Foodborne pathogens, such as Escherichia coli, and Salmonella, are commonly prevalent in contaminated food products seen through annual food recalls. Excessive use of antibiotics through the past few decades has led to a multitude of antibiotic resistant bacteria, including foodborne pathogens. We investigated microbial occurrence and their antibiotics resistances in ready-to-go food items, i.e. canned food, bagged food, and baby food. A total of 112 isolates were isolated from varying food items, and 21 of these isolates were identified through 16S rRNA sequencing revealing Bacillus sp., Staphylococcus sp. and Micrococcus sp. Bagged food items showed the most microbial diversity as well as the largest colony forming unit (log 20-25 CFU/g). Isolates showed antibiotic resistance to ampicillin, streptomycin, chloramphenicol, and kanamycin at concentrations of 100, 500, and 1000 µg/mL. 57% isolates were ampicillin resistance followed by kanamycin (26%). A variety of microorganisms present in ready-to-go food items may not be pathogenic, however their occurrence and multiple antibiotic resistance (MAR) poses risk of transferring their genes to foodborne pathogens.

Effect of Swiss Chard (Beta vulgaris var. cicla) as Nitrite Replacement on Color Stability and Shelf-Life of Cooked Pork Patties during Refrigerated Storage

In this study, the effects of pre-converted nitrite from Swiss chard powder (PS) on the color stability and shelf-life of cooked pork patties during refrigerated storage for 28 d were investigated. Nitrite was added at a concentration of approximately 120 ppm. Five treatments were formulated as follows: Control (120 ppm nitrite), T1 (2% PS), T2 (2% pre-converted nitrite from celery powder; PC), T3 (1% PS + 60 ppm nitrite), and NC (nitrite-free). The T1 and T3 samples had higher nitrosoheme pigment contents, which were associated with the redness of the samples (p<0.05). T1 resulted in the highest redness value (p<0.05). The redness and yellowness of the cooked pork patties increased with increasing PS levels. The pH of the samples subjected to all treatments decreased with progress of the storage period (p<0.05). The pH of the T1 and T3 samples treated with PS was lower (p<0.05) than that obtained with other treatments, as PS has a lower pH value. The treatments in which PS was added were most effective for reducing the level of thiobarbituric acid reactive substances (TBARS) and the residual nitrite content relative to the control. T1 resulted in the highest flavor, off-flavor, and overall acceptability scores during storage (p<0.05). The total viable bacterial count for all treatments was below 1 Log CFU/g, and E. coli and coliform bacteria were not detected during storage. Therefore, these results suggested that pre-converted nitrite from Swiss chard powder is a potential replacement for nitrite in meat products.

The Use of Starter Cultures in Traditional Meat Products

Starter cultures could play an essential role in the manufacture of traditional cured meat products. In order to achieve objectives related to meat products’ quality and safety improvement, the selection of particular strains constituting a starter culture should be carried out in the context of its application, since its functionality will depend on the type of sausage and process conditions. Also, strain selection should comply with particular requirements to warrant safety. The aim of the current review is to update the knowledge on the use of starter cultures in traditional meat products, with focus on dry-fermented products. In this manuscript, we will try to give answers to some relevant questions: Which starter cultures are used and why? Why are LAB used? What are their role and their specific mode of action? Which other groups of microorganisms (bacteria and fungi) are used as starter cultures and how do they act? A particular revision of omics approach regarding starter cultures is made since the use of these techniques allows rapid screening of promising wild strains with desirable functional characteristics, enabling the development of starter cultures better adapted to the meat matrix.

Characterization and Technological Features of Autochthonous Coagulase-Negative Staphylococci as Potential Starters for Portuguese Dry Fermented Sausages

The manufacture of dry fermented sausages is an important part of the meat industry in Southern European countries. These products are usually produced in small shops from a mixture of pork, fat, salt, and condiments and are stuffed into natural casings. Meat sausages are slowly cured through spontaneous fermentation by autochthonous microbiota present in the raw materials or introduced during manufacturing. The aim of this work was to evaluate the technological and safety features of coagulase-negative staphylococci (CNS) isolated from Portuguese dry fermented meat sausages in order to select autochthonous starters. Isolates (n = 104) obtained from 2 small manufacturers were identified as Staphylococcus xylosus, Staphylococcus equorum, Staphylococcus saprophyticus, and Staphylococcus carnosus. Genomically diverse isolates (n = 82) were selected for further analysis to determine the ability to produce enzymes (for example, nitrate-reductases, proteases, lipases) and antibiotic susceptibility. Autochthonous CNS producing a wide range of enzymes and showing low antibioresistance were selected as potential starters for future use in the production of dry fermented meat sausages.

Staphylococcus nepalensis in the guano of bats (Mammalia)

Thirty randomly selected mesophilic isolates from the six years old guano sample from mixed Myotis myotis and M. blythii summer roosts colony were isolated and identified as Staphylococcus nepalensis using MALDI TOF analysis. 16S rRNA gene sequencing of selected five isolates and subsequent phylogenetic analysis confirmed that all sequences showed the highest similarity to S. nepalensis sequences. Several virulence factors were produced by tested isolates, mainly capsule formation and resistance to tetracycline, ampicillin, gentamycin, and chloramphenicol antibiotics. Our experiments show that the majority of cultivable mesophilic bacteria from the guano of bats belong to the S. nepalensis species. This is the first report on the occurrence of this species in the guano of bats and our results indicate that the guano accumulated near or directly in human dwellings and buildings may represent a significant risk for human health.

Identification and characterization of potential autochthonous starter cultures from a Croatian "brand" product "Slavonski kulen"

The microbial population of a traditional Croatian fermented sausage "Slavonski kulen" was isolated, identified and subjected to technological and functional characterization in order to select potential autochthonous functional starter cultures. Dominant microflora were lactic acid bacteria (LAB), followed by staphylococci. Identification of isolated lactobacilli showed domination of Leuconostoc mesenteroides and Lactobacillus acidophilus while Staphylococcus xylosus and Staphylococcus warneri outnumbered the staphylococcal microbiota. Most of the isolated LAB and Staphylococcus species displayed good growth in the presence of 5% of NaCl and at 12, 18 and 22°C. All LAB and most of the staphylococci possess proteolytic activity and only Staphylococcus xylosus had lipolytic activity. All lactobacilli and staphylococci isolates produced significant concentrations of lactic acid (as determined by HPLC) and showed antimicrobial activity against pathogenic test microorganisms. Dominant LAB and Staphylococcus species displayed growth in the presence of 1% bile. Most of the staphylococci and all of lactobacilli showed sensitivity to all antibiotics tested.

Safety-related properties of staphylococci isolated from food and food environments

AIMS

To test some safety-related properties within 321 staphylococci strains isolated from food and food environments.

METHODS AND RESULTS

The isolates were identified as Staphylococcus aureus, Staphylococcus epidermidis, Staphylococcus saprophyticus, Staphylococcus pasteuri, Staphylococcus sciuri, Staphylococcus warneri and Staphylococcus xylosus. Decarboxylase activity was quite common for the various Staphylococcus spp., and tyrosine was the most frequently decarboxylated amino acid. The frequency of antibiotic resistance was highest in Staph. pasteuri and Staph. xylosus. Several of the isolates were tolerant to QAC compounds, and in some cases, QAC tolerance was present in antibiotic-resistant strains. Most of the strains displayed moderate to high adhesion rates to stainless steel and Teflon(®). The strains that readily formed biofilms belonged to the species Staph. aureus, Staph. epidermidis and Staph. pasteuri.

CONCLUSIONS

An high incidence of some safety hazards was found within the staphylococcal strains of food origin tested in this study. In particular, amino acid decarboxylase activity and biofilm-forming ability were common within strains, and antibiotic resistance and tolerance to QAC-based compounds occurred frequently as well. These characteristics are an important safety concern for food industry.

SIGNIFICANCE AND IMPACT OF THE STUDY

This work gives a first picture of safety hazards within staphylococcal species isolated from food environments. The presence of disinfectant-resistant staphylococci is a concern because resistance can be genetically transferred between the various Staphylococcus species. This could lead an increase and spread of resistant enterotoxic staphylococci and/or pathogenic staphylococci.

Distribution of aminogenic activity among potential autochthonous starter cultures for dry fermented sausages

Any bacterial strain to be used as starter culture should have suitable characteristics, including a lack of amino acid decarboxylase activity. In this study, the decarboxylase activity of 76 bacterial strains, including lactic acid bacteria and gram-positive, catalase-positive cocci, was investigated. These strains were previously isolated from European traditional fermented sausages to develop autochthonous starter cultures. Of all the strains tested, 48% of the lactic acid bacteria strains and 13% of gram-positive, catalase-positive cocci decarboxylated one or more amino acids. Aminogenic potential was strain dependent, although some species had a higher proportion of aminogenic strains than did others. Thus, all Lactobacillus curvatus strains and 70% of Lactobacillus brevis strains had the capacity to produce tyramine and beta-phenylethylamine. Some strains also produced other aromatic amines, such as tryptamine and the diamines putrescine and cadaverine. All the enterococcal strains tested were decarboxylase positive, producing high amounts of tyramine and considerable amounts of beta-phenylethylamine. None of the staphylococcal strains had tyrosine-decarboxylase activity, but some produced other amines. From the aminogenic point of view, Lactobacillus plantarum, Lactobacillus sakei, and Staphylococcus xylosus strains would be the most suitable for use as autochthonous starter cultures for traditional fermented sausages.

Viability of Staphylococcus xylosus isolated from artisanal sausages for application as starter cultures in meat products

Viability of Staphylococcus xylosus isolated from artisanal sausages for application as starter cultures in meat products Viability of Staphylococcus xylosus strains AD1 and U5 isolated from natural fermented sausages was investigated as starter cultures in fermented sausages produced in the South Region of Brazil. The study demonstrated that the Staphylococcus xylosus strains AD1 and U5 showed significant growth during fermentation, stability over freeze-dried process, negative reaction for staphylococcal enterotoxins and viability for using as a single-strain culture or associated with lactic acid bacteria for production of fermented sausages.