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1.
Food Chem ; 304: 125415, 2020 Jan 30.
Artigo em Inglês | MEDLINE | ID: mdl-31479995

RESUMO

The aim of our study was to characterize the proteolytic activity of 170 Lactobacillus strains isolated from traditional Mongolian dairy products (yogurt and fermented milk), and to investigate their capacity to generate bioactive peptides during milk fermentation. All isolates were screened for proteolytic activity using skim milk agar-well diffusion test. Fifteen strains (9 Lactobacillus helveticus and 6 Lactobacillus delbrueckii subsp. bulgaricus) were then selected and further evaluated using an original strategy based on multiparametric analysis, taking into account growth rate, acidification capacity, proteolytic activity, cell envelope associated peptidase (CEP) profile and LC-MS/MS analysis of peptides. All parameters were analyzed using principal component analysis (PCA). Results showed that strain growth and acidification correlate with peptide production and that Mongolian L. helveticus strains differ from Western strains in terms of CEP distribution. The PCA revealed that CEP profiles are major determinants of ß-casein hydrolysis patterns. Strains with distinctive proteolytic activities were identified.

2.
Crit Rev Food Sci Nutr ; : 1-13, 2019 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-31729242

RESUMO

Lactic acid-producing bacteria are the most commonly used probiotics that play an important role in protecting the host against harmful microorganisms, strengthening the host immune system, improving feed digestibility, and reducing metabolic disorders. Lactobacillus fermentum (Lb. fermentum) is a Gram-positive bacterium belonging to Lactobacillus genus, and many reportedly to enhance the immunologic response as well as prevent community-acquired gastrointestinal and upper respiratory infections. Additionally, Lb. fermentum strains produce diverse and potent antimicrobial peptides, which can be applied as food preservative agents or as alternatives to antibiotics. Further functions attributed to probiotic Lb. fermentum strains are their abilities to decrease the level of blood stream cholesterol (as cholesterol-lowering agents) and to potentially help prevent alcoholic liver disease and colorectal cancer among humans. Finally, Lb. fermentum is a key microorganism in sourdough technology, contributing to flavor, texture, or health-promoting dough ingredients, and has recently been used to develop new foods stuffs such as fortified and functional foods with beneficial attributes for human health. Development of such new foodstuffs are currently taking important proportions of the food industry market. Furthermore, an increasing awareness of the consumers prompts the food-makers to implement alternative environmental friendly solutions in the production processes and/or suitable biological alternative to limit the use of antibiotics in feed and food. Here, we give an account on the application of Lb. fermentum strains in the biomedical and food preservation fields, with a focus on probiotic features such as bacteriocin production. We also summarize the use of Lb. fermentum as cell factories with the aim to improve the efficacy and health value of functional food.

3.
Braz J Microbiol ; 50(2): 369-377, 2019 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-30852798

RESUMO

The bacteriocinogenic Enterococcus hirae ST57ACC recently isolated from a Brazilian artisanal cheese was subjected here to additional analyses in order to evaluate its bacteriocin production and the potential influence of ABC transporter system in its expression. Besides these physiological and molecular aspects, the bacteriocin was evaluated for its cytotoxicity against HT-29. Differences in the inoculum size had no impact on the growth of E. hirae ST57ACC; however, the bacteriocin was only produced after 9 h of growth when the strain was inoculated at 5% or 10% (v/v), with similar levels of bacteriocin production obtained by both conventional growth and batch fermentation. Furthermore, potential expression of ABC transporters corresponding to the bacteriocin transport and sugar metabolism was identified. In terms of adverse effects, when a semi-purified fraction of the bacteriocin and the cell-free supernatant were tested against HT-29, total cell viability was similar to observed on untreated cells, indicating the absence of cytotoxic effect. Based on the obtained results, E. hirae ST57ACC can produce its bacteriocin at industrial level by using bioreactors, its bacteriocin expression is potentially influenced by the ABC transporter system, and no cytotoxic effects were observed on HT-29 cells, indicating its potential use as a bio-preservative.


Assuntos
Transportadores de Cassetes de Ligação de ATP/metabolismo , Bacteriocinas/biossíntese , Bacteriocinas/toxicidade , Queijo/microbiologia , Streptococcus faecium ATCC 9790/metabolismo , Bacteriocinas/genética , Brasil , Metabolismo dos Carboidratos , Linhagem Celular , Streptococcus faecium ATCC 9790/genética , Streptococcus faecium ATCC 9790/isolamento & purificação , Conservantes de Alimentos , Células HT29 , Humanos
4.
Arch Microbiol ; 201(5): 679-690, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-30796474

RESUMO

This study investigated the effect of the growth temperature (20 and 37 °C) of Escherichia coli strains isolated from pigs on their adhesion to stainless steel and polycarbonate. This study also evaluated the ability of the DLVO and XDLVO mathematical models to predict this adhesion. The rise of growth temperature from 20 to 37 °C significantly influenced the adhesion of studied E. coli strains. The data also underlined that the mathematical prediction did not fully match with the experimental bacterial adhesion to surfaces. Furthermore, results showed that the colistin-resistant and sensitive E. coli strains adhesion depends on the type of abiotic surface. Based on these results, the mathematical models are limited in the prediction of the bacterial adhesion to abiotic surfaces. The surface roughness is a major parameter of the bacterial adhesion and should be included in the future mathematical models predicting the bacterial adhesion.


Assuntos
Aderência Bacteriana/fisiologia , Escherichia coli O157/fisiologia , Microbiologia de Alimentos/métodos , Cimento de Policarboxilato , Aço Inoxidável , Animais , Colistina/farmacologia , Escherichia coli O157/efeitos dos fármacos , Modelos Teóricos , Suínos , Temperatura Ambiente
5.
Arch Microbiol ; 201(3): 399-407, 2019 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-30719527

RESUMO

During this study, we characterized the seasonality's impact and environmental conditions on the yeast diversity from raw camel's milk collected in Algeria. The yeast counts were estimated to 3.55 × 102 CFU mL-1, with a maximum of 6.3 × 102 CFU mL-1. The yeasts were categorized phenotypically by API 20C AUX, MALDI-TOF and genetically by sequencing 26S rDNA and ITS1-5.8S-ITS2. The rDNA sequencing approaches revealed 12 species including unusual ones such as Trichosporon asahii, Pichia fermentans, Millerozyma farinosa, Pichia galeiformis, Candida tartarivorans and Pichia manshurica. The most dominant species were T. asahii (23%), P. fermentans (19%) and Rhodotorula mucilaginosa (14%). The high occurrence and large diversity were registered in samples collected during the autumn season, in the semi-arid and arid highlands regions with 0.66 × 103 CFU mL-1 and 0.51 × 103 CFU mL-1, respectively. Interestingly, T. asahii, R. mucilaginosa, P. fermentans, C. parapsilosis and C. zeylanoides were detected during both spring and autumn.


Assuntos
Camelus/microbiologia , Candida/isolamento & purificação , Leite/microbiologia , Pichia/isolamento & purificação , Rhodotorula/isolamento & purificação , Saccharomyces cerevisiae/isolamento & purificação , Leveduras/isolamento & purificação , Argélia , Animais , Candida/classificação , Candida/genética , DNA Fúngico/genética , DNA Ribossômico/genética , Pichia/classificação , Pichia/genética , Rhodotorula/classificação , Rhodotorula/genética , Saccharomyces cerevisiae/classificação , Saccharomyces cerevisiae/genética , Estações do Ano , Leveduras/classificação , Leveduras/genética
6.
Chemosphere ; 220: 505-513, 2019 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-30594803

RESUMO

We evaluated the acute toxicities of metals cadmium (Cd), copper (Cu) and nickel (Ni) to a widely-distributed copepod Eurytemora affinis isolated from the Seine estuary. Both sexes of adult E. affinis were exposed separately to the three metals at concentration gradients to determine its 50% lethal concentration (LC50). After 4 days of exposure, both males and females showed a higher sensitivity to Cu (male LC50: 25.0 µg.L-1 and female LC50: 38.0 µg.L-1) than to Ni (male LC50: 90.0 µg.L-1 and female 161.0 µg.L-1) and Cd (male LC50: 127.8 µg.L-1 and female LC50: 90.0 µg.L-1). To assess for the first time, the extend of metal bioaccumulation and its effect at population scale, late stages (>200 µm) were collected and exposed to each metal at the concentration of 1/3 LC50, and to their mixture during 144 h without feeding. The Cd concentration consistently increased with time until the end of the experiment, whereas the Ni and Cu concentrations reached a plateau after 24 h and 72 h exposure, respectively. The results revealed that the copepods could accumulate Cu faster than Ni and Cd either in the treatment alone (0.58 L g-1.d-1) or in the three-metal mixture (0.72 L g-1.d-1) after 50% of exposure time (72 h). The number of individuals decreased in copepod populations except for the Cd treatment, where the number of nauplii increased. In addition, all treatments of metal exposure negatively affected bacterial densities in the copepod cultures, where the Cu treatment showed a negative remarkable effect compared with Cd and Ni treatment did.


Assuntos
Cádmio/toxicidade , Copépodes/metabolismo , Cobre/toxicidade , Níquel/toxicidade , Poluentes Químicos da Água/toxicidade , Animais , Copépodes/efeitos dos fármacos , Estuários
7.
Vet Microbiol ; 226: 81-88, 2018 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-30389047

RESUMO

Colistin-resistant Escherichia coli are isolated from pigs suffering from post-weaning diarrhea (PWD). This study was designed to develop an experimental model of PWD using mcr-1-carrying shiga toxin-producing E. coli (STEC) or enterotoxigenic E. coli (ETEC), for the future evaluation of control measures. Three groups of eight piglets, kept in high biosecurity units, were orally inoculated with mcr-1-positive STEC or ETEC, and one unchallenged group was used as a control. Clinical signs were recorded. Regularly-collected fecal samples and samples obtained from the digestive tract of animals sacrificed one month after inoculation were cultured in selective media and isolates were characterized. Blood samples were used to genotype the polymorphisms of the pigs' intestinal receptors for F4 and F18 E. coli adhesins. Diarrhea was more frequent and more fecal samples contained the inoculated strain in the group inoculated with the O149-F4 ETEC strain than with the O141-F18 or O139-F18 STEC strains. However, fewer positive samples were obtained from the two pigs with the F4 resistant genotype. The three inoculated strains could be re-isolated up to the end of the experiment. Excretion peaked on the first week after inoculation with the O149-F4 ETEC strain, and later for the other two. An mcr-1 gene transfer to other commensal isolates was observed only for O139-F18 STEC, while the loss of mcr-1 from the inoculated strain occurred in all groups. The O149-F4 ETEC challenge may be used to evaluate alternative solutions to combat PWD caused by colistin-resistant E. coli in pigs.

8.
Front Microbiol ; 9: 2354, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-30386307

RESUMO

To compensate for their amino acid auxotrophy, lactobacilli have developed the ability to hydrolyze proteins present in their environment. This proteolytic activity not only generates the free amino acids needed by the bacteria, but also a large variety of peptides, some of which are endowed with biological activities. These so-called "bioactive peptides" (BAPs) are interesting from a nutrition and healthcare perspective. The use of lactic acid bacteria (LAB) such as lactobacilli is an effective strategy for production and valorization of new BAPs. The proteolytic activity of lactobacilli is exerted in a strain- and species-dependent manner: each species exhibits different proteinase content, leading to a large variety of proteolytic activities. This underlines the high potential of Lactobacillus strains to produce novel hydrolysates and BAPs of major interest. This review aims at discussing the potential of different Lactobacillus species to release BAPs from fermentation media and processes. Strategies used for peptide production are presented. Additionally, we propose a methodology to select the most promising Lactobacillus strains as sources of BAPs. This methodology combines conventional approaches and in silico analyses.

9.
Appl Microbiol Biotechnol ; 102(22): 9871, 2018 11.
Artigo em Inglês | MEDLINE | ID: mdl-30328491

RESUMO

There is an error in the original publication of this paper. The incorrect author name was captured as "Djamel Dridier" instead of "Djamel Drider". The original article has been corrected.

10.
Appl Microbiol Biotechnol ; 102(23): 9949-9958, 2018 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-30280241

RESUMO

Lactic acid bacteria (LAB), a heterogeneous group of bacteria that produce lactic acid as the main product of carbohydrate degradation, play an important role in the production and protection of fermented foods. Moreover, beside the technological use of these microorganisms added to control and steer food fermentations, their beneficial healthy properties are largely overt. Thus, numerous LAB strains have obtained the probiotic status, which entails the ability to maintain and promote a good health of consumers. In particular, increasing consideration is being focused on probiotic microorganisms that can improve the human immune response against dangerous viral and fungal enemies. For such beneficial microbes, the term "immunobiotics" has been coined. Together with an indirect host-mediated adverse effect against undesirable microorganisms, also a direct antagonistic activity of several LAB strains has been largely demonstrated. The purpose of this review is to provide a fullest possible overview of the antiviral and antifungal activities ascribed to probiotic LAB. The interest in this research field is substantiated by a large number of studies exploring the potential application of these beneficial microorganisms both as biopreservatives and immune-enhancers, aiming to reduce and/or eliminate the use of chemical agents to prevent the development of pathogenic, infectious, and/or degrading causes.

11.
Artigo em Inglês | MEDLINE | ID: mdl-30376295

RESUMO

The steady increase of antimicrobial resistance of different pathogens requires the development of alternative treatment strategies next to the oral delivery of antibiotics. A photothermally activated platform based on reduced graphene oxide (rGO)-embedded polymeric nanofiber mats for on-demand release of antibiotics upon irradiation in the near-infrared is fabricated. Cross-linked hydrophilic nanofibers, obtained by electrospinning a mixture of poly(acrylic acid) (PAA) and rGO, show excellent stability in aqueous media. Importantly, these PAA@ rGO nanofiber mats exhibit controlled photothermal heating upon irradiation at 980 nm. Nanofiber mats are efficiently loaded with antibiotics through simple immersion into corresponding antibiotics solutions. Whereas passive diffusion based release at room temperature is extremely low, photothermal activation results in increased release within few minutes, with release rates tunable through power density of the applied irradiation. The large difference over passive and active release, as well as the controlled turn-on of release allow regulation of the dosage of the antibiotics, as evidenced by the inhibition of planktonic bacteria growth. Treatment of superficial skin infections with the antibiotic-loaded nanofiber mats shows efficient wound healing of the infected site. Facile fabrication and implementation of these photothermally active nanofiber mats makes this novel platform adaptable for on-demand delivery of various therapeutic agents.

12.
Artigo em Inglês | MEDLINE | ID: mdl-30229513

RESUMO

Here we show that Bacillus pumilus ICVB403 recently isolated from copepod eggs is able to produce, after 48-72 h of growth in Landy medium, extracellular inhibitory compounds, which are active against Staphylococcus aureus ATCC 25923, methicillin-resistant S. aureus (MRSA) ATCC 43300, MRSA-S1, Staphylococcus epidermidis 11EMB, Staphylococcus warneri 27EMB, and Staphylococcus hominis 13EMB. Moreover, these extracellular inhibitory compound(s) were able to potentiate erythromycin against the aforementioned staphylococci. The minimum inhibitory concentration (MIC) of erythromycin was reduced from 32 µg/mL to 8 µg/mL for MRSA ATCC 43300 and MRSA SA-1 strains, and from 32-64 µg/mL to 4 µg/mL for S. epidermidis 11EMB and S. hominis 13EMB strains.The genome sequencing and analysis of B. pumilus ICVB403 unveiled 3.666.195 nucleotides contained in 22 contigs with a G + C ratio of 42.0%, 3.826 coding sequences, and 73 RNAs. In silico analysis guided identification of two putative genes coding for synthesis of surfactin A, a lipopeptide with 7 amino acids, and for a circular bacteriocin belonging to the circularin A/uberolysin family, respectively.

13.
Vet Res ; 49(1): 66, 2018 07 31.
Artigo em Inglês | MEDLINE | ID: mdl-30060765

RESUMO

Due to the continuing global concerns involving antibiotic resistance, there is a need for scientific forums to assess advancements in the development of antimicrobials and their alternatives that might reduce development and spread of antibiotic resistance among bacterial pathogens. The objectives of the 2nd International Symposium on Alternatives to Antibiotics were to highlight promising research results and novel technologies that can provide alternatives to antibiotics for use in animal health and production, assess challenges associated with their authorization and commercialization for use, and provide actionable strategies to support their development. The session on microbial-derived products was directed at presenting novel technologies that included exploiting CRISPR-Cas nucleases to produce sequence-specific antimicrobials, probiotics development via fecal microbiome transplants among monogastric production animals such as chickens and mining microbial sources such as bacteria or yeast to identify new antimicrobial compounds. Other research has included continuing development of antimicrobial peptides such as newly discovered bacteriocins as alternatives to antibiotics, use of bacteriophages accompanied by development of unique lytic proteins with specific cell-wall binding domains and novel approaches such as microbial-ecology guided discovery of anti-biofilm compounds discovered in marine environments. The symposium was held at the Headquarters of the World Organisation for Animal Health (OIE) in Paris, France during 12-15 December 2016.


Assuntos
Criação de Animais Domésticos , Anti-Infecciosos/análise , Descoberta de Drogas , Doenças dos Animais/prevenção & controle , Animais , Bacteriocinas , Bacteriófagos , Sistemas CRISPR-Cas , França , Gado
14.
Microbiol Res ; 210: 59-64, 2018 May.
Artigo em Inglês | MEDLINE | ID: mdl-29625659

RESUMO

The enterovirus Coxsackievirus B4 (CV-B4) can infect different human tissues and provoke abnormal function or destruction of various organs and cells. Moreover, its infections have been linked to the onset of type 1 diabetes. Coxsackievirus B4 is classified as a "challenging virus", due to the intense yet vain efforts to find effective prevention and therapeutic agents, especially within biological compounds. Lactobacillus plantarum is a lactic acid bacterium that is endowed with probiotic properties, and holds great potential for applications in medical and food industry sectors. Several compounds produced by this microorganism have been associated with various benefits including antimicrobial activity. In this work, we investigated the possible antiviral abilities of two Lb. plantarum strains and their derivatives against CV-B4. The different assays carried out (e.g. pre-incubation, competition and post-infection, using HEp-2 cells as human cell model) suggest that the tested microorganisms and their derivatives have an in vitro inhibiting activity against CV-B4. This is the first report showing the anti-CVB4 activity of Lb. plantarum strains and their derivatives.


Assuntos
Enterovirus/efeitos dos fármacos , Lactobacillus plantarum/metabolismo , Probióticos/farmacologia , Antivirais/farmacologia , Linhagem Celular/efeitos dos fármacos , Proliferação de Células/efeitos dos fármacos , Infecções por Coxsackievirus/tratamento farmacológico , Indústria Alimentícia , Humanos , Medicina do Trabalho
15.
Arch Microbiol ; 200(5): 783-791, 2018 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-29423562

RESUMO

Bacillus subtilis is a wealth source of lipopeptide molecules such as iturins, surfactins and fengycins or plipastatins endowed with a range of biological activities. These molecules, designated secondary metabolites, are synthesized via non-ribosomal peptides synthesis (NRPS) machinery and are most often subjected to a complex regulation with involvement of several regulatory factors. To gain novel insights on mechanism regulating fengycin production, we investigated the effect of the fascinating polynucleotide phosphorylase (PNPase), as well as the effect of lipopeptide surfactin. Compared to the wild type, the production of fengycin in the mutant strains B. subtilis BBG235 and BBG236 altered for PNPase has not only decreased to about 70 and 40%, respectively, but also hampered its antifungal activity towards the plant pathogen Botrytis cinerea. On the other hand, mutant strains BBG231 (srfAA-) and BBG232 (srfAC-) displayed different levels of fengycin production. BBG231 had registered an important decrease in fengycin production, comparable to that observed for BBG235 or BBG236. This study permitted to establish that the products of pnpA gene (PNPase), and srfAA- (surfactin synthetase) are involved in fengycin production.


Assuntos
Bacillus subtilis/metabolismo , Proteínas de Bactérias/fisiologia , Lipopeptídeos/biossíntese , Polirribonucleotídeo Nucleotidiltransferase/fisiologia , Bacillus subtilis/genética , Expressão Gênica , Regulação Bacteriana da Expressão Gênica , Lipopeptídeos/genética , Mutação , Óperon
16.
Probiotics Antimicrob Proteins ; 10(3): 456-465, 2018 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-29168155

RESUMO

This study aimed at comparing the genome of Enterococcus faecalis B3A-B3B, a bacteriocinogenic strain recently isolated from a healthy Iraqi infant to those of Enterococci of clinical and beneficial grades. The putative genes gelE, cpd, efaAfm, ccf, agg, and cob coding for virulence factors were detected in B3A-B3B strain, which meanwhile resulted to be non-cytotoxic, non-hemolytic, devoid of inflammatory effects, and sensitive to most of the antibiotics tested except for clindamycin and trimethoprim, which resistance is usually ascribed to intrinsic nature. B3A-B3B strain was remarkable for its hydrophobicity, auto-aggregation, adhesion to human Caco-2 cells, and survival in simulated gastrointestinal conditions, and cholesterol assimilation fulfilling therefore key beneficial attributes.

17.
Curr Opin Biotechnol ; 49: 23-28, 2018 02.
Artigo em Inglês | MEDLINE | ID: mdl-28787641

RESUMO

Bacteriocins, defined as ribosomally synthesized antimicrobial peptides, have traditionally been used as food preservatives, either added or produced by starter cultures during fermentation. In-depth studies of a select few bacteriocins opened exiting new research fields and broadened the application of these antimicrobial peptides. The possibility of developing bacteriocins into next generation antibiotics, accompanied with the rapid development in genetics and nanotechnology, paves the way to even more fascinating applications such as novel carrier molecules (delivery systems) and the treatment of cancer. Also, some bacteriocins are found to regulate quorum sensing which suggests novel applications for this group of substances. While there is some interesting translational research on bacteriocins from Gram-negative bacteria, the majority of application-oriented studies are focused on bacteriocins from Gram-positive microorganisms, mostly lactic acid bacteria. The applications of bacteriocins are expanding from food to human health.

18.
Front Microbiol ; 8: 2278, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-29209292

RESUMO

We studied a collection of 79 colistin-resistant Escherichia coli isolates isolated from diseased pigs in France between 2009 and 2013. We determined a number of phenotypic and genetic characters using broth microdilution to characterize their antimicrobial susceptibility. We performed pulse field gel electrophoresis (PFGE) to assess their genetic diversity and assign them to phylogroups. High-throughput real-time PCR micro-array was used to screen for a selection of genetic markers of virulence, and PCR and sequencing of the main recognized resistance genes allowed us to investigate the mechanisms of colistin resistance. Results showed that isolates belonged to several phylogroups and most had a unique PFGE profile. More than 50% of the isolates were also resistant to sulfonamides, trimethoprim, tetracycline, ampicillin or chloramphenicol. The mcr-1 gene was detected in 70 out of 79 isolates and was transferred by conjugation in 33 of them, sometimes together with resistance to sulfonamides, trimethoprim, tetracycline, ampicillin, chloramphenicol, cefotaxime, or gentamicin. Mutations in the amino-acid sequences of proteins MgrB, PhoP, PhoQ, PmrB, but not PmrA, were detected in isolates with or without the mcr-1 gene. More than one-third of the isolates harbored the F18, F4, astA, hlyA, estI, estII, elt, stx2e, iha, orfA, orfB, paa, terE, ecs1763, or ureD virulence markers. In conclusion, although most isolates had a unique PFGE profile, a few particular combinations of phylogenetic groups, virulence genes and mutations in the sequenced genes involved in colistin resistance were identified on a number of occasions, suggesting the persistence of certain isolates over several years.

19.
Artigo em Inglês | MEDLINE | ID: mdl-29185234

RESUMO

Lactobacilli strains are considered as a preventive means for treatment of vaginal infections or post-antibiotic treatment to repopulate the vaginal mucosa. This study aimed at establishing the vaginal lactobacillus profile of Algerian women with different vaginal diseases. Afterwards, lactobacilli isolated from swabs were in vitro characterized for their probiotic hallmarks. This prospective study allowed isolation of 44 Lactobacillus strains and 160 potentially pathogens, among which are Escherichia coli (50 isolates), Staphylococcus sp. (38 isolates), Enterococcus sp. (16 isolates), and Candida sp. (56 isolates). All Lactobacilli strains were characterized for their antagonism, adhesion to polystyrene, and resistance to acidity and bile. Consequently, six Lactobacillus strains (Lb. fermentum 5LB4, 5LB10, 5LB12, Lb. plantarum 5LB2, 5LB11, and Lactobacillus sp. 4LB9) were moderately or weakly adherent, and 35 potentially pathogens exhibited weak to strong adhesion to polystyrene. Antagonism was recorded for 36 Lactobacillus strains towards E. coli 6E2, S. aureus 7S3, Enterococcus sp. 5EN8, and Candida albicans C1 used as indicator organisms. Finally, Lb. fermentum 9LB6, 4LB16, and 10LB1 and Lb. plantarum 9LB4 were remarkable for their inhibitory activity, absence of hemolytic potential, and for their resistance to acidity (pH 1.5) and bile (0.5%) harsh conditions.

20.
Front Microbiol ; 8: 1919, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-29085344

RESUMO

Copepods represent a major source of food for many aquatic species of commercial interest for aquaculture such as mysis shrimp and early stages of fishes. For the purpose of this study, the culturable mesophilic bacterial flora colonizing Acartia tonsa copepod eggs was isolated and identified. A total of 175 isolates were characterized based on their morphological and biochemical traits. The majority of these isolates (70%) were Gram-negative bacteria. Matrix-assisted laser desorption/ionization-time of flight-mass spectrometry (MALDI-TOF-MS) was used for rapid identification of bacterial isolates. Here, 58% of isolates were successfully identified at the genus level and among them, 54% were identified at the species level. These isolates belong to 12 different genera and 29 species. Five strains, identified as Bacillus pumilus, named 18 COPS, 35A COPS, 35R COPS, 38 COPS, and 40A COPS, showed strong antagonisms against several potential fish pathogens including Vibrio alginolyticus, V. anguillarum, Listeria monocytogenes, and Staphylococcus aureus. Furthermore, using a differential approach, we show that the antimicrobial activity of the 35R COPS strain is linked primarily to the production of antimicrobial compounds of the amicoumacin family, as demonstrated by the specific UV-absorbance and the MS/MS fragmentation patterns of these compounds.

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