Short communication: Antimicrobial potential of Lactobacillus plantarum strains isolated from Slovak raw sheep milk cheeses

Susceptibility of Foodborne Pathogens to Milk-Origin Lactic Acid Bacteria Supernatants: A Comprehensive Meta-Regression Study

This systematic review and meta-analysis compile the in vitro antimicrobial efficacy of lactic acid bacteria (LAB) supernatants against three common pathogenic bacteria found in dairy products: Salmonella spp., L. monocytogenes, and Staphylococcus aureus. After screening and analysis of full papers, identified by searches in PubMed, Scopus, and Web of Science databases, thirty-nine studies were regarded as relevant, and a total of 510 observations were recorded. The effects of moderators on inhibition diameters were assessed by adjusting three pathogen-specific meta-regression models. Results showed that, in general terms, strains from the Enterococcus genus displayed the highest inhibition values against L. monocytogenes (15.90 ± 2.138 mm), whereas Lacticaseibacillus strains were more effective against S. aureus (11.89 ± 0.573 mm). The well diffusion test outperformed the spot and disk diffusion tests, and more acidic LAB supernatants resulted in higher measurements of inhibition diameters (p < 0.001). Meta-regression models incorporating LAB genus, pathogen concentration, and incubation time explained 33.8%, 52.3%, and 19.8% of the total variance in inhibition diameters for L. monocytogenes, Salmonella spp., and S. aureus, respectively. None of the three models showed evidence of publication bias. This meta-regression study demonstrated that LAB strains present in dairy products possess a variable capacity to inhibit any of the three foodborne pathogens. Overall, L. monocytogenes was found to exhibit greater susceptibility than Salmonella spp. and S. aureus; thus, the antilisterial capacity of the selected LAB strains could be exploited in developing biocontrol strategies for cheese-making.

Bioactive Metabolites of Lactiplantibacillus plantarum K014 Against Methicillin-Resistant Staphylococcus aureus ATCC43300 and In Vitro Evaluation of Its Antibacterial, Antioxidant and Anti-inflammatory Activities

This study aims to evaluate the effects of bioactive metabolites produced by lactic acid bacteria against methicillin-resistant Staphylococcus aureus (MRSA) ATCC 43300. A total of six lactic acid bacteria (LAB) were selected to evaluate the antimicrobial activity against MRSA ATCC 43300, a skin pathogen that is highly resistant to most antibiotics. The K014 isolate from a fermented vegetable recorded the highest inhibition against MRSA ATCC 43300 at 91.93 ± 0.36%. 16S rRNA sequencing revealed the K014 isolate is closely related to L. plantarum and the sequence was subsequently deposited in the GenBank database with an accession number of MW180960, named as Lactiplantibacillus plantarum K014. The cell-free supernatant (CFS) of L. plantarum K014 had tolerance to high temperature as well as acidic pH. The bioactive metabolites, such as hydrogen peroxide, lactic acid and hyaluronic acid, were produced by L. plantarum K014. Result from ABTS assay showed higher antioxidant activity (46.28%) as compared to that obtained by DPPH assay (2.97%). The CFS had showed anti-inflammatory activity for lipoxygenase (LOX) assay at 43.66%. The bioactive metabolites of L. plantarum K014 showed very promising potential to be used topical skin pathogens.

Identification and Characterization of Malolactic Bacteria Isolated from the Eastern Foothills of Helan Mountain in China

Malolactic fermentation (MLF) converts malic acid into lactic acid by lactic acid bacteria (LAB). MLF may affect potential wine quality impact as global warming intensifies, and the alcohol in the wine increases, which threatens MLF. Lactiplantibacillus plantarum is considered a new generation of MLF starter because of the ability of high ethanol tolerance and good enological characteristics. In this research, 132 LAB strains were isolated from the eastern foothills of Helan Mountain in Ningxia, China. Twenty-one higher ethanol tolerance isolates were obtained by 15% (v/v) ethanol preliminary screening. They were identified by 16S rRNA sequencing and differentiated by randomly amplified polymorphic DNA (RAPD). Stress factors include ethanol, pH, and SO₂, and the combination of stresses was used to screen stress-tolerance strains. β-D-glucosidase activity, MLF performance, and biogenic amine content were tested to evaluate the enological characteristics. GC-MS detected the volatile components of the wine after MLF. The results showed that twenty strains were identified as L. plantarum, and one strain was Lentilactobacillus hilgardii. Especially, the strains of A7, A18, A23, A50, and B28 showed strong resistance to high ethanol, low pH, and high SO₂. A7, A50, and B28 showed better β-D-glucosidase activity and thus were inoculated into cabernet sauvignon wines whose ethanol content was 14.75% (v/v) to proceed MLF. A7 finished MLF in 36 d, while the control strains Oenococcus oeni 31-DH and L. plantarum BV-S2 finished MLF in 24 d and 28 d, respectively. Nevertheless, A50 and B28 did not finish MLF in 36 d. The data showed that A7 brought a more volatile aroma than control. Notably, the esters and terpenes in the wine increased. These results demonstrated the potential applicability of L. plantarum A7 as a new MLF starter culture, especially for high-ethanol wines.

Characterization of Microbial Shifts during the Production and Ripening of Raw Ewe Milk-Derived Idiazabal Cheese by High-Throughput Sequencing

Simple Summary

Idiazabal is a traditional cheese produced from raw ewe milk in the Basque Country (Southwestern Europe). The sensory properties of raw milk cheeses have been attributed, among other factors, to microbial shifts that occur during the production and ripening processes. In this study, we used high-throughput sequencing technologies to investigate the microbiota of Latxa ewe raw milk and the dynamics during cheese production and ripening processes. The microbiota of raw milk was composed of lactic acid bacteria (LAB), environmental bacteria and non-desirable bacteria. Throughout the cheese making and ripening processes, the growth of LAB was promoted, whereas that of non-desirable and environmental bacteria was inhibited. Moreover, some genera not reported previously in raw ewe milk were detected and clear differences were observed in the bacterial composition of raw milk and cheese among producers, in relation to LAB and environmental or non-desirable bacteria, some of which could be attributed to the production of flavour related compounds.

Abstract

In this study, we used high-throughput sequencing technologies (sequencing of V3–V4 hypervariable regions of 16S rRNA gene) to investigate for the first time the microbiota of Latxa ewe raw milk and the bacterial shifts that occur during the production and ripening of Idiazabal cheese. Results revealed several bacterial genera not reported previously in raw ewe milk and cheese, such as Buttiauxella and Obesumbacterium. Both the cheese making and ripening processes had a significant impact on bacterial communities. Overall, the growth of lactic acid bacteria (LAB) (Lactococcus, Lactobacillus, Leuconostoc, Enterococcus, Streptococcus and Carnobacterium) was promoted, whereas that of non-desirable and environmental bacteria was inhibited (such as Pseudomonas and Clostridium). However, considerable differences were observed among producers. It is noteworthy that the starter LAB (Lactococcus) predominated up to 30 or 60 days of ripening and then, the growth of non-starter LAB (Lactobacillus, Leuconostoc, Enterococcus and Streptococcus) was promoted. Moreover, in some cases, bacteria related to the production of volatile compounds (such as Hafnia, Brevibacterium and Psychrobacter) also showed notable abundance during the first few weeks of ripening. Overall, the results of this study enhance our understanding of microbial shifts that occur during the production and ripening of a raw ewe milk-derived cheese (Idiazabal), and could indicate that the practices adopted by producers have a great impact on the microbiota and final quality of this cheese.

Fundamental role of Lactobacillus plantarum and inulin in improving safety and quality of Karish cheese

Background

Karish cheese manufactured traditionally from raw milk may harbor many biological health hazards.

Aim

Production of safe pasteurized Karish cheese with improved sensory characteristics using probiotics and prebiotics (synbiotic Karish cheese).

Methods

Laboratory Karish cheese was made to study the effect of Lactobacillus plantarum with and without inulin on cheese quality. Treatments were examined for sensory, chemical, and microbial quality, shelf life, and survival of L. plantarum were also monitored. The antimicrobial effect of L. plantarum and inulin against Enterobacter aerogenes in cheese was evaluated.

Results

Sensory, chemical, and microbial quality of Karish cheese supplemented with L. plantarum and inulin were positively affected; moreover, the shelf life was extended up to 28 days. Karish cheese contained L. plantarum showed the highest flavor score, while treatment contained both L. plantarum and inulin attained the best body and texture score. Moreover, L. plantarum and inulin significantly reduced E. aerogenes count during Karish cheese chilled storage; the reduction log reached 3.76 log₁₀cfu/g on the seventh day of storage compared to control. Additionally, Inulin significantly increased the survival of L. plantarum throughout the storage period.

Conclusion

This study concluded that using probiotics and prebiotics in Karish cheese synergistically improved its sensory properties, safety, and hygienic quality.

Comparison of the Probiotic Potential between Lactiplantibacillus plantarum Isolated from Kimchi and Standard Probiotic Strains Isolated from Different Sources

In the present study, the properties of the Lactiplantibacillus (Lpb.) plantarum WiKim0112 isolated from kimchi were evaluated by comparing its probiotic properties to those of Lpb. plantarum WCFS1 and KACC 11451 isolated from different sources. In both pH 2 and 3, media containing pepsin, Wikim0112, and WCFS1 showed higher cell viability than KACC11451. Viability of all Lpb. plantarum strains in a medium containing pancreatin and bile salt oxgall was significantly decreased compared to the control. WCFS1 showed the highest thermotolerance, followed by Wikim0112 and KACC11451. Wikim0112 showed a similar level of antibacterial activity to WCFS1 and exhibited an overall higher antibacterial activity than KACC11451 against six pathogens. All Lpb. plantatum strains showed high antioxidant activities in SOD, DPPH, and ABTS assays, especially Wikim0112 and WCFS1 exhibited a higher antioxidant activity than KACC11451. All Lpb. plantarum strains showed approximately 60–62% adhesion rates to Caco-2 cells. Moreover, in LPS-stimulated Caco-2 cells, all Lpb. plantarum strains significantly decreased the mRNA expression of pro-inflammatory cytokines (i.e., IL-1β, IL-6, and TNF-α); Wikim0112 significantly increased the mRNA expression of IL-4 and IFN-γ. Wikim0112 was resistant to streptomycin and vancomycin, whereas WCFS1 and KACC11451 were resistant to four (clindamycin, ciprofloxacin, tetracycline, and vancomycin) and three (ciprofloxacin, tetracycline, and vancomycin) antibiotics, respectively. These results, taken together, indicated that compared to Lpb. plantarum strains isolated from different sources, Wikim0112 showed desirable probiotic properties, suggesting its potential applications in the food and pharmaceutical industries.

Microbiome Associated with Slovak Traditional Ewe’s Milk Lump Cheese

Worldwide consumers increasingly demand traditional/local products, to which those made from ewe’s milk belong. In Slovakia, dairy products made from ewe’s milk have a long tradition. A total of seventeen farmhouse fresh ewe’s milk lump cheeses from various local farm producers in central Slovakia were sampled at farms and then analyzed. Based on the sequencing data analysis, the phylum Firmicutes dominated (60.92%) in ewe’s lump cheeses, followed with the phylum Proteobacteria (38.23%), Actinobacteria (0.38%) and Bacteroidetes (0.35%). The phylum Firmicutes was represented by six genera, among which the highest amount possessed the genus Streptococcus (41.13%) followed with the genus Lactococcus (8.54%), Fructobacillus (3.91%), Enterococcus (3.18%), Staphylococcus (1.80%) and the genus Brochotrix (0.08%). The phylum Proteobacteria in ewe’s lump cheeses involved eight Gram-negative genera: Pseudomonas, Acinetobacter, Enterobacter, Ewingella, Escherichia-Shigella, Pantoea and Moraxella. The phylum Bacteroidetes involved three genera: Bacteroides, Sphingobacterium and Chrysobacterium. Results presented are original; the microbiome of Slovak ewe’s milk lump cheese has been not analyzed at those taxonomic levels up to now.

Assessment of Quality and Safety of Farm Level Produced Cheeses from Sheep and Goat Milk

Consumption of sheep’s and goat’s milk and cheese is currently increasing. The production process of these types of cheese is being carried out by traditional domestic production at farm level. However, knowledge in the field of hygiene, technology and health safety of cheeses are still insufficient. This study aimed to examine the physical and chemical quality and microbiological safety of sheep’s and goat’s milk and cheeses made from them. The month of milking influenced the content of milk components (p < 0.001) in sheep’s milk and goat’s milk, but no changes in SCC content during the examined period were found (p > 0.05). Level of contamination by Enterobacteriaceae sp. and coagulase-positive staphylococci was lower than 5 log CFU/mL in sheep’s and goat’s milk. During the ripening time, the number of lactic acid bacteria significantly raised (p < 0.001). Ripening time statistically changed (p < 0.001) not just the microbial safety of cheeses but also the color (p < 0.01). Under the applicable regulations, the analyzed samples were evaluated as suitable for human consumption.

Antimicrobial Resistance of Lactobacillus johnsonii and Lactobacillus zeae in Raw Milk

Lactobacillus johnsonii and Lactobacillus zeae are among the lactobacilli with probiotic properties, which occur in sour milk products, cheeses, and to a lesser extent in raw milk. Recently, resistant strains have been detected in various species of lactobacilli. The aim of the study was to determine the incidence of resistant Lactobacillus johnsonii and Lactobacillus zeae strains in various types of raw milk. A total of 245 isolates were identified by matrix-assisted laser desorption/ionization mass spectrometry and polymerase chain reaction methods as Lactobacillus sp., of which 23 isolates of Lactobacillus johnsonii and 18 isolates of Lactobacillus zeae were confirmed. Determination of susceptibility to selected antibiotics was performed using the E-test and broth dilution method, where 7.3% of lactobacilli strains were evaluated as ampicillin-resistant, 14.7% of isolates as erythromycin-resistant, and 4.9% of isolates as clindamycin-resistant. The genus Lactobacillus johnsonii had the highest resistance to erythromycin (34.8%), similar to Lactobacillus zeae (33.3%). Of the 41 isolates, the presence of the gene was confirmed in five Lactobacillus johnsonii strains and in two strains of Lactobacillus zeae. The presence of resistant strains of Lactobacillus johnsonii and Lactobacillus zeae is a potential risk in terms of spreading antimicrobial resistance through the food chain.

Probiotic Properties of Lactiplantibacillus plantarum LB5 Isolated from Kimchi Based on Nitrate Reducing Capability

The purpose of this study was to investigate the probiotic properties of lactic acid bacteria isolated from Korean radish water kimchi (dongchimi). A total of 800 isolates of lactic acid bacteria were isolated from kimchi, and the strain having reduction and tolerance capability for nitrate and nitrite was selected and identified as Lactiplantibacillus plantarum LB5 (LPLB5) by 16S rRNA sequencing. LPLB5 showed higher tolerance to acidic pH values (pH 2.5), 0.3% bile salts, and heat treatment (40, 50, and 60 °C). Antibacterial activity showed strong inhibition against four food-borne pathogenic bacteria (E. coli O157:H7 ATCC 35150, Pseudomonas aeruginosa KCCM 12539, Listeria monocytogenes KCCM 40307, and Staphylococcus aureus ATCC 25923). The strain did not show any antibiotic resistance, β-hemolytic activity, or ability to produce β-glucuronidase. LPLB5 also exhibited a 30% auto-aggregation ability and 33–60% co-aggregation ability with four pathogenic bacteria (E. coli O157: H7 ATCC 35150, E. coli KCTC 2571, L. monocytogenes ATCC 51776, and S. aureus ATCC 25923). Moreover, the strain showed approximately 40% 2,2-diphenyl-1-picryl-hydrazyl (DPPH) radical- and 10% 2-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid (ABTS) radical-scavenging activity. In cell culture studies, human colon epithelial cells (Caco-2) were treated with LPLB5 (10⁶ and 10⁷ CFU/mL); the bacteria showed more than 70% adherence onto and a 32% invasion rate into the Caco-2 cells. LPLB5 significantly decreased the mRNA expression levels of pro-inflammatory cytokines (interleukin-1 beta (IL-1β), interleukin 6 (IL-6), and tumor necrosis factor-alpha (TNF-α)) and increased the mRNA expression levels of anti-inflammatory cytokines (interleukin-4 (IL-4), interleukin-10 (IL-10), and interferon-gamma (IFN-γ)) in lipopolysaccharide-stimulated Caco-2 cells. Our data suggest that LPLB5 is safe and possesses probiotic, antioxidant, and anti-inflammatory activities.

Lactobacillus plantarum relieves diarrhea caused by enterotoxin-producing Escherichia coli through inflammation modulation and gut microbiota regulation

Lactobacillus plantarum can relieve diarrhea caused by enterotoxigenic Escherichia coli (ETEC), but the remission mechanism has not been fully explained. This study compares the ability of four Lactobacillus plantarum strains from different niches to alleviate diarrhea caused by ETEC infection and explores their potential remission manner. The results showed that Lactobacillus plantarum CCFM1143 had the most obvious protective effect on diarrhea caused by ETEC. FGDLZ1M5, FCQNA30M6 and CCFM1143 reduced tumor necrosis factor-α (TNF-α), interferon-γ (IFN-γ) and interleukin (IL)-6 as well as jejunal injury. Moreover, FCQNA30M6 and CCFM1143 increased the aquaporin AQP3, and CCFM1143 increased interleukin (IL)-10 and decreased heat-stable enterotoxin (ST), while FGDLZ1M5 reduced the toll-like receptor (TLR4). The gut microbiota analysis demonstrated that ETEC increased Proteus and Pseudomonas and reduced Bifidobacterium, Odoribacter, Allobaculum and Blautia. A supplement of Lactobacillus plantarum could reconstruct the unbalanced gut microbiota. Furthermore, CCFM1143 significantly increased butyric acid, acetic acid, propionic acid and isobutyric acid, while FGDLZ1M5 only increased butyric acid. In summary, Lactobacillus plantarum alleviated ETEC-induced diarrhea by regulating the inflammatory cytokines, rebalancing the gut microbiota and modulating short-chain fatty acids (SCFAs) generation, which could provide the foundation and support for subsequent clinical trials and probiotic products.

Susceptibility to Bacteriocins in Biofilm-Forming, Variable Staphylococci Isolated from Local Slovak Ewes' Milk Lump Cheeses

Seventeen staphylococci isolated from 54 Slovak local lump cheeses made from ewes’ milk were taxonomically allotted to five species and three clusters/groups involving the following species: Staphylococcus aureus (5 strains), Staphylococcus xylosus (3 strains), Staphylococcus equorum (one strain) Staphylococcus succinus (5 strains) and Staphylococcus simulans (3 strains). Five different species were determined. The aim of the study follows two lines: basic research in connection with staphylococci, and further possible application of the bacteriocins. Identified staphylococci were mostly susceptible to antibiotics (10 out of 14 antibiotics). Strains showed γ-hemolysis (meaning they did not form hemolysis) except for S. aureus SAOS1/1 strain, which formed β-hemolysis. S. aureus SAOS1/1 strain was also DNase positive as did S. aureus SAOS5/2 and SAOS51/3. The other staphylococci were DNase negative. S. aureus SAOS1/1 and SAOS51/3 showed biofilm formation on Congo red agar. However, using quantitative plate assay, 12 strains out of 17 showed low-grade biofilm formation (0.1 ≤ A₅₇₀ < 1), while five strains did not form biofilm (A₅₇₀ < 0.1). The growth of all strains, including those strains resistant to enterocins, was inhibited by nisin and gallidermin, with high inhibition activity resulting in the inhibition zone in size from 1600 up to 102,400 AU/mL (arbitrary unit per milliliter). This study contributes to microbiota colonization associated with raw ewe’s milk lump cheeses; it also indicates bacteriocin treatment benefit, which can be used in prevention and/or elimination of staphylococci.