Enterococcus Hirae Research Articles

Antibiotic Resistance Pattern of Lactobacillus reuteri, Lactobacillus salivarius, and Enterococcus hirae Isolated from Gastrointestinal and Respiratory Tract in Commercial Broiler Chickens

Ever since antibiotics were discovered for the treatment of bacterial diseases, an increase in antibiotic-resistant bacteria has been noticed as an economic and public health concern with a high rate of morbidity and mortality. Antibiotic resistance in broiler chickens can be a great threat to public health. This research aimed to screen commercial poultry’s gastrointestinal and respiratory tract bacteria to observe the antibiotic resistance pattern. In this experiment, gastrointestinal tract (GIT) and respiratory tract (RT) bacteria were identified using 16s rRNA gene sequencing from broiler chickens in anaerobic conditions following a bile salt tolerance assay and an antibiotic susceptibility test. Lactobacillus reuteri, Lactobacillus salivarius, and Enterococcus hirae were identified as the isolates. The bacteria found in the gut had a modest degree of bile salt tolerance. The isolates were sensitive to amoxicillin, gentamicin, and streptomycin but resistant to tetracycline, levofloxacin, metronidazole, azithromycin, and erythromycin. This study ensures that the GIT and RT of broiler chicken is a hidden source of the isolated bacteria. A large part of this bacterial population is antibiotic-resistant and reported as a public health concern.

The gut microbiota of wild birds undergoing rehabilitation as a reservoir of multidrug-resistant enterococci in a metropolitan area in Brazil.

Enterococci are ubiquitous usually commensal bacteria that can act as opportunistic pathogens frequently associated with resistance to multiple antimicrobial classes. A variety of animals may carry potentially harmful enterococci. In the present work, the occurrence and characteristics of enterococci recovered from the fecal microbiota of wild birds belonging to four families (Accipitridae, Cathartidae, Falconidae and Strigidae) were investigated. Enterococci were recovered from 104 (92.0%) fecal samples obtained from 113 birds, and 260 strains were selected for additional characterization. Enterococcus faecalis was the predominant species (63.8%), followed by Enterococcus hirae (16.2%), Enterococcus faecium (11.5%), Enterococcus gallinarum (5.4%), Enterococcus avium (1.5%), Enterococcus casseliflavus (0.8%), and Enterococcus raffinosus and Enterococcus cecorum (0.4% each). Major percentages (11.9% 75.0%) of nonsusceptibility were observed to quinolones (particularly to enrofloxacin), erythromycin, rifampin, nitrofurantoin, tetracycline and streptomycin. Gentamicin and ampicillin resistances (13.3% each) were only detected among E. faecium. A total of 133 (51.2%) strains were MDR, showing a large variety of MDR profiles, composed by simultaneous resistance encompassing 3 to 12 antimicrobials. MDR strains were found in 68.2% of the birds. Antimicrobial resistance was associated with the presence of the aac(6')-aph(2″)-Ia, aph(2″)-Id, ant(6)-Ia, ant(9)-Ia, ant(9)-Ib, tet(M), tet(L), tet(S), erm(B), mef(A/E), msrC, and vat(D) genes. The most common virulence genes were efaA, gelE, ace, eeP, and asa1. PFGE analysis revealed a large genetic diversity among most of the strains. MLST performed for 35 E.faecalis strains revealed 23 different STs, whereas 14 STs were found among 18 E.faecium strains. Hospital-associated lineages ST22, ST25, ST56, ST1274 were identified. The results show that the wild birds investigated can carry a diversity of potentially hazardous enterococcal strains displaying multiple antimicrobial resistance and virulence genes, reinforcing the assumption that these animals provide an important target to monitor the circulation of microorganisms that deserve consideration under the One Health perspective.

Enterococcus hirae Bacteremia Secondary to Urinary Tract Infection: A Case Report

Enterococcus hirae (E. hirae) infection is an uncommon pathogen in human infections. Bacteremia due to E. hirae associated with urinary tract infection is uncommon. We present a case of E. hirae bacteremia in a young woman with no underlying comorbidities. This case report emphasizes the importance of considering E. hirae as a potential pathogen in urinary tract infections.

Identification, Safety Assessment, and Antimicrobial Characteristics of Cocci Lactic Acid Bacteria Isolated from Traditional Egyptian Dairy Products.

The main objective of this study is to isolate and identify lactic acid bacteria (LAB) from various Egyptian dairy products, examine their antibacterial and hemolysis potential, and ensure their safety when used as starter cultures in different dairy industries. Egyptian dairy products are often made without the use of commercial starter cultures, using raw milk and artisanal methods. The most popular traditional dairy products are Laban Rayeb and Zabady, as well as the cheese varieties of Ras, Domiati, and Karish. The microbial communities used for fermentation and the diversity of lactic acid bacteria are the most important factors that can affect the quality of these products. In order to investigate the diversity of cocci lactic acid bacteria in Egyptian dairy products, 70 samples of raw or fermented milk and cheeses were collected from traditional cheese-making factories, local markets, and farmhouses located in the Delta area of Egypt. Following this, the LAB were isolated from the samples. One hundred fifty-seven isolates of Gram-positive, catalase-negative, and cocci bacterial species were identified via rep-PCR, and some isolates were confirmed using pheS and 16S rRNA gene sequencing, as follows: Streptococcus infantarius subsp. infantarius (three isolates), Enterococcus hirae (three isolates), Enterococcus faecium (ninety-six isolates), Enterococcus faecalis (forty isolates), Enterococcus durans (six isolates), Lactococcus garvieae (one isolate), Pediococcus acidilactici (seven isolates), and Lactococcus lactis subsp. Lactis (one isolate). These findings validate that five strains have strong antibacterial activity against Escherichia coli, Salmonella typhimurium, and Listeria monocytogenes, and one hundred thirty-four strains were safe for hemolysis. The five strains were selected as protective cultures, including Pediococcus acidilactici, Lactococcus lactis subsp. lactis, E. faecalis, and E. faecium.

Isolation of biosurfactant-producing and crude oil-degrading bacterium, Enterococcus hirae, from hydrocarbon-polluted soils and characterization of the biosurfactant produced

Isolation of biosurfactant-producing and crude oil-degrading bacterium, Enterococcus hirae, from hydrocarbon-polluted soils and characterization of the biosurfactant produced

Functional characterization and biotechnological applications of exopolysaccharides produced by newly isolated Enterococcus hirae MLG3-25-1.

This study investigated the potential applications of Enterococcus hirae MLG3-25-1 exopolysaccharides (EPS), with a focus on their isolation, identification, production, and functional characteristics. After the bacterial strain was cultured in De Man-Rogosa-Sharpe (MRS) medium containing 1% glucose at 37°C, the EPS was refined, and the highest yield of 0.85mg/mL was achieved at the 24-h incubation period. Enterococcus hirae MLG3-25-1 was found to be able to produce EPS. The study explored the microstructure of the EPS, which resembles polysaccharide sheets with smooth surfaces, through scanning electron microscope (SEM) analysis. Through Fourier transform infrared spectroscopy (FT-IR) and nuclear magnetic resonance(NMR) analysis, the chemical composition, aligning with glycosidic bond characteristics, has been deciphered. Furthermore, the antimicrobial and antibiofilm activities against pathogenic bacteria, particularly Bacillus sp., demonstrated potential applications in combating antibiotic resistance. The EPS exhibited notable antioxidant activity (89.36% DPPH scavenging), along with high water-holding capacity (575%), emulsifying activity, and flocculation activity, suggesting its potential as a stabilizing agent in the food industry. Overall, this study provides a comprehensive characterization of Enterococcus hirae MLG3-25-1 EPS, emphasizing its diverse applications in antimicrobial, antioxidant, and food-related industries. These findings lay the groundwork for further exploration and utilization of this EPS in various sectors.

Antimicrobial resistance characterization of Enterococcus faecium, Enterococcus faecalis and Enterococcus hirae isolated from marine coastal recreational waters in the State of São Paulo, Brazil.

Coastal water quality is facing increasing threats due to human activities. Their contamination by sewage discharges poses significant risks to the environment and public health. We aimed to investigate the presence of antibiotic-resistant Enterococcus in beach waters. Over a 10-month period, samples were collected from four beaches in the State of São Paulo (Brazil). Enterococcus isolates underwent matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF/MS) and molecular analysis for accurate genus and species identification. The antimicrobial susceptibility for 14 antibiotics was evaluated using the disc diffusion method followed by a multidrug-resistance (MDR) classification. PCR amplification method was used to detect antimicrobial resistance genes (ARGs). Our findings revealed the prevalence of Enterococcus faecalis, E. faecium and E. hirae. Out of 130 isolates, 118 were resistant to multiple antibiotics. The detection of resistance genes provided evidence of the potential transfer of antibiotic resistance within the environment. Our findings underscore the necessity for continuous research and surveillance to enhance understanding of the pathogenicity and antimicrobial resistance mechanisms of Enterococcus, which is crucial to implement effective measures to preserve the integrity of coastal ecosystems.

Synthesis and antimicrobial activity testing of quaternary ammonium silane compounds

With increasing health awareness of the pathogenic effects of disease-causing microorganisms, interest in and use (of medical textiles, disinfectants in medical devices, etc.) of antimicrobial substances have increased in various applications, such as medical textiles and disinfectants (alcohol-based and nonalcoholic), in medical devices There are several concerns with alcohol-based disinfectants, such as surface deformation of medical devices due to high alcohol content and damage to skin tissue caused by lipid and protein denaturation of cell membranes. Quaternary ammonium compounds (quats) were preferred because they have the potential to prepare water-based disinfectants. In this study, novel (3-chloropropyl)triethoxysilane (CPTMO) and (3-chloropropyl)triethoxysilane (CPTEO) based quaternary ammonium silane compounds (silane-quats) were developed using quats with carbon chain lengths of C12, C14, C16 and C18. Titration (ASTM D2074) was used to calculate the yield of the synthesis and the structures of the products were characterised by Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy (13C NMR, 1H NMR) and gas chromatography-mass spectrometry (GC–MS).The in vitro antimicrobial activity of the synthesized samples was evaluated against Gram-positive (Staphylococcus aureus (S. aureus), Enterococcus hirae (E. hirae)) and Gram-negative (Escherichia coli (E. coli), Pseudomonas aeruginosa (P. aeruginosa)) bacteria and fungi (Candida albicans (C. albicans), Aspergillus brasiliensis (A. brasiliensis)) using the minimum inhibitory concentration (MIC) test. According to MIC tests, the silane-quats with the highest antimicrobial effects were dimethylhexadecyl[3-(trimethoxysilyl)propyl]ammonium chloride (SQ3), which had an MIC of < 16 μg/ml (ppm) against E. coli, S. aureus, E. hirae, C. albicans, and A. brasiliensis and 32 μg/ml against P. aeruginosa. The MIC test results also showed antimicrobial activity at least 2 times greater than that of the commercially available disinfectant benzalkonium chloride (BAC). Findings suggest that SQ3 (C16) holds promise as an effective medical disinfectant, presenting a novel approach to combating microbial infections in healthcare settings.

A Label-Free Optical Flow Cytometry Based-Method for Rapid Assay of Disinfectants' Bactericidal Activity.

Selecting the appropriate disinfectant to control and prevent healthcare-associated infections (HAIs) is a challenging task for environmental health experts due to the large number of available disinfectant products. This study aimed to develop a label-free flow cytometry (FCM) method for the rapid evaluation of bactericidal activity and to compare its efficacy with that of standard qualitative/quantitative suspension tests. The bactericidal efficiency of eight commercial disinfectants containing quaternary ammonium compounds (QACs) was evaluated against four strains recommended by EN 13727 (Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, Enterococcus hirae) and four multidrug-resistant pathogens. The proposed FCM protocol measures changes in scattered light and counts following disinfectant exposure, neutralization, and culture steps. Unlike other available FCM-based methods, this approach does not rely on autofluorescence measurements, impedance cytometry, or fluorescent dyes. The FCM scattered light signals revealed both decreased count rates and morphological changes after treatment with minimum inhibitory concentrations (MICs) and higher concentrations for all tested bacteria. The results from the FCM measurements showed excellent correlation with those from standard assays, providing a rapid tool for monitoring the susceptibility profile of clinical, multidrug-resistant pathogens to chemical disinfectants, which could support infection prevention and control procedures for healthcare environments. This label-free FCM protocol offers a novel and rapid tool for environmental health experts, aiding in the optimization of disinfectant selection for the prevention and control of HAIs.

Comparative Study of Physicochemical Properties and Antibacterial Potential of Cyanobacteria Spirulina platensis-Derived and Chemically Synthesized Silver Nanoparticles.

The "green synthesis" of nanoparticles (NPs) offers cost-effective and environmentally friendly advantages over chemical synthesis by utilizing biological sources such as bacteria, algae, fungi, or plants. In this context, cyanobacteria and their components are valuable sources to produce various NPs. The present study describes the comparative analysis of physicochemical and antibacterial properties of chemically synthesized (Chem-AgNPs) and cyanobacteria Spirulina platensis-derived silver NPs (Splat-AgNPs). The physicochemical characterization applying complementary dynamic light scattering and transmission electron microscopy revealed that Splat-AgNPs have an average hydrodynamic radius of ∼ 28.70 nm and spherical morphology, whereas Chem-AgNPs are irregular-shaped with an average radius size of ∼ 53.88 nm. The X-ray diffraction pattern of Splat-AgNPs confirms the formation of face-centered cubic crystalline AgNPs by "green synthesis". Energy-dispersive spectroscopy analysis demonstrated the purity of the Splat-AgNPs. Fourier transform infrared spectroscopy analysis of Splat-AgNPs demonstrated the involvement of some functional groups in the formation of NPs. Additionally, Splat-AgNPs demonstrated high colloidal stability with a zeta-potential value of (-50.0 ± 8.30) mV and a pronounced bactericidal activity against selected Gram-positive (Enterococcus hirae and Staphylococcus aureus) and Gram-negative (Pseudomonas aeruginosa and Salmonella typhimurium) bacteria compared with Chem-AgNPs. Furthermore, our studies toward understanding the action mechanism of NPs showed that Splat-AgNPs alter the permeability of bacterial membranes and the energy-dependent H+-fluxes via FoF1-ATPase, thus playing a crucial role in bacterial energetics. The insights gained from this study show that Spirulina-derived synthesis is a low-cost, simple approach to producing stable AgNPs for their energy-metabolism-targeted antibacterial applications in biotechnology and biomedicine.

Human Health Benefits and Microbial Consortium of Stevia Fermented with Barley Nuruk

In this study, the microbial community present during the barley yeast fermentation of stevia leaves and its correlation with antioxidant, anti-obesity, and anti-inflammatory properties, as well as metabolites, were investigated using UPLC-Q-TOF-MS. Stevia was fermented using commercial TSB media (TSB 1, TSB 3, and TSB 5) and sucrose (Sucrose 1, Sucrose 3, and Sucrose 5) for 1, 3, and 5 days, respectively. Stevia ferments showed higher DPPH and ABTS radical scavenging capacity compared to samples incubated with sucrose for 5 days, and all six ferments inhibited nitric oxide production in a concentration-dependent manner in LPS-induced mouse macrophages. Furthermore, UPLC-QTOF-MS analysis identified 23 related substances, including 10 terpenoids (including rubusoside, steviolbioside, and rebadioside derivatives), dulcoside A, and phlomisoside II, which are indicators of stevia, as well as five flavonoids, four phenolic acids, and four fatty acids. We also identified the microbial community during fermentation via the next-generation sequencing of the 16S rRNA gene for bacteria and the internal transcribed spacer (ITS) gene for fungi. The results showed that TSB 1 and Sucrose 1 ferments were dominated by the pathogens Enterococcus hirae (58.93%) and Cronobacter sakazakii (80.92%), while samples fermented for more than 3 days were pathogen-free and dominated by lactic acid bacteria such as Pediococcus stilesii (73.37%). Microbial community analysis using the ITS region showed that Saccharomycopsis fibuligera, classified as a yeast rather than a mold, dominated the stevia fermentation regardless of the fermentation duration. In particular, the microbial community of the fermentation with a sucrose solution was dominated by S. fibuligera by more than 99% throughout the fermentation periods of 1, 3, and 5 days. Finally, to apply the stevia ferments topically to human skin, skin irritation tests were performed on 30 volunteers. The results showed that the highly concentrated extracts (1 mg/mL) of all six stevia ferments were hypoallergenic. Taken together, these findings suggest that barley nuruk fermented from stevia leaves with a sucrose solution offers promise as a natural ingredient for use in functional foods and cosmetics.

Diet-induced changes in the jejunal microbiota of developing broilers reduce the abundance of Enterococcus hirae and Enterococcus faecium

Modern broiler breeds allow for high feed efficiency and rapid growth, which come at a cost of increased susceptibility to pathogens and disease. Broiler growth rate, feed efficiency, and health are affected by the composition of the gut microbiota, which in turn is influenced by diet. In this study, we therefore assessed how diet composition can affect the broiler jejunal gut microbiota. A total of 96 broiler chickens were divided into four diet groups: control, coated butyrate supplementation, medium-chain fatty acid supplementation, or a high-fibre low-protein content. Diet groups were sub-divided into age groups (4, 12 and 33 days of age) resulting in groups of 8 broilers per diet per age. The jejunum content was used for metagenomic shotgun sequencing to determine the microbiota taxonomic composition at species level. The composed diets resulted in a total of 104 differentially abundant bacterial species. Most notably were the butyrate-induced changes in the jejunal microbiota of broilers 4 days post-hatch, resulting in the reduced relative abundance of mainly Enterococcus faecium (-1.8 l2fc, Padj = 9.9E-05) and the opportunistic pathogen Enterococcus hirae (-2.9 l2fc, Padj = 2.7E-08), when compared to the control diet. This effect takes place during early broiler development, which is critical for broiler health, thus exemplifying the importance of how diet can influence the microbiota composition in relation to broiler health. Future studies should therefore elucidate how diet can be used to promote a beneficial microbiota in the early stages of broiler development.

Ningxiang pig-derived Enterococcus hirae HNAU0516 ameliorates postweaning diarrhoea by promoting intestinal health and modulating the gut microbiota in piglets

Early weaning-induced stress precipitates diarrhoea, significantly curtailing the growth performance of piglets. A pivotal contributor to this postweaning affliction is the emergence of gut bacterial dysbiosis. Enterococcus hirae, a promising probiotic, has indicated unclear effects and mechanisms on intestinal health. In this study, we investigated the effects and underlying mechanisms of oral supplementation with Ningxiang pig-derived Enterococcus hirae HNAU0516 orally supplementation on the gut bacterial community, immune response and gut barrier function in piglets. 21 d age Duroc × (Landrace × Yorkshire) piglets with a similar BW were randomly allocated to two groups. The Enterococcus hirae HNAU0516 administration group was inoculated orally with Ningxiang pig-derived Enterococcus hirae HNAU0516 throughout the trial period. Conversely, the control group received the same volume of physiological saline. Our findings revealed that Enterococcus hirae HNAU0516 supplementation effectively reduced diarrhoea rates of piglets (P = 0.010). Notably, this probiotic promoted intestinal development and enhanced intestinal barrier function. It also showed potential anti-inflammatory properties. Furthermore, Enterococcus hirae HNAU0516 supplementation significantly remodelled the colonic microbiota and increased the production of acetate (P = 0.007). In conclusion, our study highlights that Ningxiang pig-derived Enterococcus hirae HNAU0516 improves postweaning diarrhoea by promoting intestinal development, enhancing intestinal barrier function, decreasing intestinal permeability, modulating intestinal microbiota, and increasing short-chain fatty acids production.

Species prevalence, virulence genes, and antibiotic resistance of enterococci from food-producing animals at a slaughterhouse in Turkey

Healthy cattle, sheep, and goats can be reservoirs for gastrointestinal pathogenic fecal enterococci, some of which could be multidrug-resistant to antimicrobials. The objective of this study was to determine the prevalence and diversity of Enterococcus species in healthy sheep, goat, and cattle carcasses, as well as to analyze the antimicrobial resistance phenotype/genotype and the virulence gene content. During 2019–2020, carcass surface samples were collected from 150 ruminants in a slaughterhouse. A total of 90 enterococci, comprising five species, were obtained. The overall prevalence of enterococci was found to be 60%, out of which 37.7% were identified as Enterococcus (E.) hirae, 33.3% as E. casseliflavus, 15.5% as E. faecium, 12.2% as E. faecalis, and 1.1% as E. gallinarum. Virulence-associated genes of efaA (12.2%) were commonly observed in the Enterococcus isolates, followed by gelE (3.3%), asaI (3.3%), and ace (2.2%). High resistance to quinupristin-dalfopristin (28.8%), tetracycline (21.1%), ampicillin (20%), and rifampin (15.5%) was found in two, four, four, and five of the Enterococcus species group, respectively. The resistance of Enterococcus isolates to 11 antibiotic groups was determined and multidrug resistant (MDR) strains were found in 18.8% of Enterococcus isolates. Characteristic resistance genes were identified by PCR with an incidence of 6.6%, 2.2%, 1.1%, 1.1%, 1.1%, and 1.1% for the tetM, ermB, ermA, aac(6ʹ)Ie-aph(2")-la, VanC1, and VanC2 genes in Enterococcus isolates, respectively. Efflux pump genes causing multidrug resistance were detected in Enterococcus isolates (34.4%). The results showed that there were enterococci in the slaughterhouse with a number of genes linked to virulence that could be harmful to human health.

Spectral Phasor Applied to Spectrally-Resolved Single Molecule Localization Microscopy.

Spectrally-resolved single-molecule localization microscopy (srSMLM) has emerged as a powerful tool for exploring the spectral properties of single emitters in localization microscopy. By simultaneously capturing the spatial positions and spectroscopic signatures of individual fluorescent molecules, srSMLM opens up the possibility of investigating an additional dimension in super-resolution imaging. However, appropriate and dedicated tools are required to fully capitalize on the spectral dimension. Here, we propose the application of the spectral phasor analysis as an effective method for summarizing and analyzing the spectral information obtained from srSMLM experiments. The spectral phasor condenses the complete spectrum of a single emitter into a two-dimensional space, preserving key spectral characteristics for single-molecule spectral exploration. We demonstrate the effectiveness of spectral phasor in efficiently classifying single Nile Red fluorescence emissions from largely overlapping cyanine fluorescence signals in dual-color PAINT experiments. Additionally, we employed spectral phasor with srSMLM to reveal subtle alterations occurring in the membrane of Gram-positive Enterococcus hirae in response to gramicidin exposure, a membrane-perturbing antibiotic treatment. Spectral phasor provides a robust, model-free analytic tool for the detailed analysis of the spectral component of srSMLM, enhancing the capabilities of multi-color spectrally-resolved single-molecule imaging.

In Vitro Profiling of Potential Fish Probiotics, Enterococcus hirae Strains, Isolated from Jade Perch, and Safety Properties Assessed Using Whole Genome Sequencing.

The demands of intensified aquaculture production and escalating disease prevalence underscore the need for efficacious probiotic strategies to enhance fish health. This study focused on isolating and characterising potential probiotics from the gut microbiota of the emerging aquaculture species jade perch (Scortum barcoo). Eighty-seven lactic acid bacteria and 149 other bacteria were isolated from the digestive tract of five adult jade perch. The screening revealed that 24 Enterococcus hirae isolates inhibited the freshwater pathogens Aeromonas sobria and Streptococcus iniae. Co-incubating E. hirae with the host gut suspensions demonstrated a two- to five-fold increase in the size of growth inhibition zones compared to the results when using gut suspensions from tilapia (a non-host), indicating host-specificity. Genome analysis of the lead isolate, E. hirae R44, predicted the presence of antimicrobial compounds like enterolysin A, class II lanthipeptide, and terpenes, which underlay its antibacterial attributes. Isolate R44 exhibited desirable probiotic characteristics, including survival at pH values within the range of 3 to 12, bile tolerance, antioxidant activity, ampicillin sensitivity, and absence of transferable antimicrobial resistance genes and virulence factors commonly associated with hospital Enterococcus strains (IS16, hylEfm, and esp). This study offers a foundation for sourcing host-adapted probiotics from underexplored aquaculture species. Characterisation of novel probiotics like E. hirae R44 can expedite the development of disease mitigation strategies to support aquaculture intensification.

Investigation of advanced biological properties of carbon, carbon‐boron quantum dots, and copper (II) phthalocyanine nanoconjugates

Non‐peripherally, glycerol terminal groups substituted copper (II) phthalocyanine were non‐covalently (electrostatic and/or π–π interaction) attached to carbon (CQD) and carbon‐boron quantum dots (CBQD) to form QDs‐Pc nanoconjugate systems. Synthesized novel phthalocyanine compounds and QDs‐Pc conjugate systems were characterized using different spectroscopic techniques. Various biological assessments were applied to newly synthesized compounds. Conjugates 4 and 5 had a maximal free radical scavenging activity of 71.3% and 68.1% at a 100 mg/L concentration. Compounds exhibited high antidiabetic activities at 200 mg/L. Also, compounds showed significant DNA nuclease activity at all tested concentrations. The most efficient MIC value was obtained as 4 mg/L against Enterococcus hirae and Enterococcus feacalis. This MIC value was further decreased after photodynamic therapy, and it was observed that the antimicrobial effects of the compounds increased. Inhibition of microbial cell viability was obtained as 100% for all compounds. In addition, compounds exerted perfect biofilm inhibitory effects.

Bacteriocins against biogenic amine-accumulating lactic acid bacteria in cheese: Nisin A shows the broadest antimicrobial spectrum and prevents the formation of biofilms

Cheese is a food in which toxic concentrations of biogenic amines (BA) may be reached, mainly as a consequence of the decarboxylation of determined amino acids by certain lactic acid bacteria (LAB). To maintain the food safety of cheese, environmentally friendly strategies are needed that specifically prevent the growth of BA-producing LAB and the accumulation of BA. The bacteriocins produced by LAB are natural compounds with great potential as food biopreservatives. This work examines the antimicrobial potential of 7 bacteriocin-containing, cell-free supernatants (CFS: coagulin A-CFS, enterocin A-CFS, enterocin P-CFS, lacticin 481-CFS, nisin A-CFS, nisin Z-CFS and plantaricin A-CFS) produced by LAB against 48 strains of the LAB species largely responsible for the accumulation of the most important BA in cheese, i.e., histamine, tyramine and putrescine. Susceptibility to the different CFS was strain-dependent. The histamine-producing species with the broadest sensitivity spectrum were Lentilactobacillus parabuchneri (the species mainly responsible for the accumulation of histamine in cheese) and Pediococcus parvulus. The tyramine-producing species with the broadest sensitivity spectrum was Enterococcus faecium, while Enterococcus faecalis and Enterococcus hirae were among the most sensitive putrescine producers. Nisin A-CFS was active against 31 of the 48 BA-producing strains (the broadest antimicrobial spectrum recorded). Moreover, commercial nisin A prevented biofilm formation by 67% of the BA-producing, biofilm-forming LAB strains. These findings underscore the potential of bacteriocins in the control of BA-producing LAB, and support the use of nisin A as a food grade biopreservative for keeping BA-producing LAB in check and reducing BA accumulation in cheese.

In Vitro Interaction between Mycoplasma agalactiae and Small Ruminants' Endogenous Bacterial Strains of Enterococcus spp. and Coagulase-Negative Staphylococcus.

Recently, an antimicrobial effect on Mycoplasma agalactiae (Ma), the main etiological agent of contagious agalactia (CA), was reported in vitro with strains of Enterococcus spp. from ovine and caprine milk. The aim of this work was to evaluate the interaction of Ma with the same Enterococcus spp. isolated from other anatomical locations (vagina) and other bacterial populations present in milk, such as coagulase-negative staphylococci (CNS). The vaginal Enterococcus strains and the raw milk CNS were isolated from sheep and goats. Experimental in vitro conditions were prepared to assess the growth of Ma with and without the presence of these strains. The selected vaginal strains were identified as Enterococcus (E.) hirae and E. mundtii, and the strains of CNS were identified as Staphylococcus petrasii. Different interactions of Ma with ovine and caprine wild vaginal strains of Enterococcus and dairy strains of CNS are described for the first time: Ma can grow exponentially during 15 h with the selected strains, although with certain strains, its optimal growth can be negatively affected (p < 0.05). The colonization and/or excretion of Ma could, therefore, be influenced by certain endogenous bacterial strains. Our results increase the knowledge about possible bacterial ecology dynamics surrounding CA.

Serological monitoring of Enterococcus cecorum specific antibodies in chickens

Pathogenic Enterococcus cecorum (EC) has gained increasing importance as the cause of skeletal infections in meat-type chicken production. Since effective intervention strategies are scarce, it must be focused on preventive measures. Vaccination of meat-type breeder chicken flocks is common practice to protect the progeny against infection with EC. However, no data are available on seroconversion after infection or vaccination. The aim of the present study was the serological monitoring of chickens for EC-specific immunoglobulin Y (IgY) using a newly established EC-specific, indirect ELISA for chickens. Sera from previous infection studies were used for the establishment of the assay. Serum samples from confirmed EC-positive meat-type chicken flocks, vaccinated, and non-vaccinated meat-type chicken breeder flocks were analyzed for EC-specific IgY. Comparison of ELISA results with results from real-time PCR and/or bacteriological examination via culture revealed fair to substantial agreement. In infected chickens, more samples were classified as positive via ELISA than via real-time PCR and/or bacteriological examination via culture. Focusing on chickens experimentally infected at 1 day post-hatch (dph), the highest proportion of positive results and highest S/P ratios were found at 42 dph (p < 0.05). A similar trend was observed for the samples from naturally infected chickens (p < 0.05). Adjustment of the secondary antibody against immunoglobulin M (IgM) may open possibilities to use the assay during the early phase of the growing period, when there is still a chance to treat the infection. The examination of samples from vaccinated and non-vaccinated meat-type breeder chickens revealed no significant differences of S/P ratios independent of farm and autogenous vaccine used. In addition to that, monitoring of a non-vaccinated meat-type breeder chicken flock at 4, 10, 15, and 19 weeks post-hatch showed a continuous increase of ELISA-positive serum samples associated with an increase of S/P ratios. This may be explained by cross reactivity with antibodies to Enterococcus hirae or natural antibodies. The usage of EC-specific, recombinant proteins for coating of the plates may help to reduce unspecific background and increase the assay’s specificity in future applications. In conclusion, the newly developed ELISA provides a suitable tool for serological monitoring of meat-type chickens during experimental studies with EC under standardized conditions. Remarkably, the assay is able to detect a higher proportion of EC-positive chickens than other methods, which are currently available. However, the assay is not yet suitable for the monitoring of breeder flocks due to high background.