Characterisation of lactic acid producing <Emphasis Type="Italic">Sporolactobacillus</Emphasis> strains from tree barks in Thailand

Eight spore-forming lactic acid producing bacteria were isolated from tree barks in Thailand. They were identified as Sporolactobacillus nakayamae (Group I, three isolates), S. terrae (Group II, two isolates), S. kofuensis (Group III, one isolate) and S. inulinus (Group IV, two isolates) based on their phenotypic characteristics and 16S rRNA gene sequence analyses. Four isolates in Groups I and II produced DL lactic acid (89.60–114.61 g/L), while three isolates in Groups III and IV produced D-lactic acid (88.01–113.78 g/L). Isolate BK65-3 identified as S. inulinus produced the highest D-lactic acid concentrations (101.42 g/L), productivity (1.41 g/L/h), yields (84.52%) and optical purity of D-lactic acid (100%).     

<Emphasis Type="Italic">Streptomyces tunisialbus</Emphasis> sp. nov., a novel <Emphasis Type="Italic">Streptomyces</Emphasis> species with antimicrobial activity

A novel actinomycete strain designated S2^T was isolated from Tunisian rhizosphere soil of Lavandula officinalis. This isolate exhibited broad spectrum antibacterial activity against several Gram-positive and Gram-negative bacteria and also antifungal activity against yeast and filamentous fungi. The isolate S2^T presents morphological and chemotaxonomic characteristics typical of the members of the genus Streptomyces. Whole cell hydrolysates of S2^T were found to contain LL-diaminopimelic acid. The major fatty acids were identified as C16:0, anteiso-C15:0 and iso-C16:0 whereas the predominant menaquinones were found to be MK-9(H6) and MK-9(H8). The polar lipids were identified as diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, phosphatidylinositol, phosphatidylinositol mannoside and three unidentified compounds. The G+C content of the genomic DNA was determined to be 71.8 mol%. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain S2^T belongs to the genus Streptomyces and is closely related to Streptomyces netropsis DSM 40259^T with 99.86% sequence similarity. Multi-locus sequence analysis (MLSA) based on four house-keeping gene alleles (gyrB, recA, trpB, rpoB) showed that isolate S2^T is closely related to S. netropsis, with an MLSA distance greater than 0.007. The DNA–DNA relatedness between strain S2^T and its near phylogenetic neighbour was 63.6 ± 2.3%, which is lower than the 70% threshold value for delineation of genomic prokaryotic species. This isolate was also distinguished from the type strain S. netropsis DSM 40259^T, using a combination of morphological and physiological features. Based on its phenotypic and molecular properties, strain S2^T is considered to represent a novel species of the genus Streptomyces, for which the name Streptomyces tunisialbus sp. nov. is proposed. The type strain is S2^T (= JCM 32165^T = DSM 105760^T).     

CPRMethicillin resistant coagulase-negative staphylococci isolated from South Korean ducks exhibiting tremor

Background

We describe coagulase-negative staphylococci (CoNS) isolates collected from ducklings exhibiting tremor in South Korea over the period of 2010 to 2011. Screening of antimicrobial susceptibility and analysis of SCCmec elements of CoNS were also investigated.

Results

Staphylococcus cohnii was the most frequent staphylococcus (9 isolates) and S. sciuri (4 isolates), S. lentus (3 isolate), S. simulans (1 isolate) and S. epidermidis (1 isolate) were also detected. Among the 15 antimicrobials tested in this study, resistance against oxacillin (15 isolates, 83.3%) was most frequently observed, but only one isolate (SNUDS-1) possessed mecA. This isolate was shown to possess SCCmec type III; the type 3 ccr complex and the class A mec complex.

Conclusions

Based on these results, isolate SNUDS-1 was shown to possess SCCmec type III; the type 3 ccr complex and the class A mec complex. Although the SCCmec type III is not predominant in human, MR-CoNS (Methicillin resistance Coagulase-negative staphylococci) in food animals should be monitored to prevent the dissemination of antimicrobial resistance genes and resistant pathogens to the community.

     

Isolation,Identification and Screening of Potential Probiotic Bacteria in Milk from South African Saanen Goats

This study aimed to evaluate lactic acid bacteria isolates from Saanen goats’ milk for probiotic attributes, thereby determining their potential as direct-fed microbials for goats. Isolates were identified using API 50CH system, 16S rDNA sequencing and matrix-assisted laser desorption ionization-time of flight mass spectrometry. All 17 isolates obtained were identified as Lactobacillus plantarum except one identified as Pediococcus acidilactici. Four isolates identified as L. plantarum (Accession numbers KJ026587.1, KM207826.1, KC83663.1 and KJ958428.1) by at least two of the techniques used and isolate 17 differently identified by all the methods used were selected as representatives and then screened for probiotic properties. These isolates displayed phenotypic probiotic attributes including tolerance to acid and bile salts, ability to adhere to intestines and possession of antagonistic activities against Proteus vulgaris, Staphylococcus aureus, Salmonella typhimurium, Pseudomonas aeruginosa and Escherichia coli. The lactic acid bacteria isolated from Saanen goats’ milk showed potential to be used as sustainable probiotics in goats’ industry. Successful use of probiotics in animals depends upon availability of appropriate isolates originating from the specific host animal. This study is a positive contribution towards identification of isolates with potential for formulation as direct-fed microbials for South African Saanen goats.     

Isolation and characterization of marine biofilm forming bacteria from a ship’s hull

Background

Diverse aquatic microorganisms are capable of colonizing living and non-living surfaces leading to the formation of biofilms. Commonly visualized as a slimy layer, these biofilms are filled with hundreds of other microorganisms compared to free living planktonic cells. Microbial surface colonization and surface-associated metabolic activities also exert several macroscale deleterious effects, including biofouling, biocorrosion and the persistence and transmission of harmful or pathogenic microorganisms and virulence determinants. The present study deals with the isolation and screening of marine bacteria for biofilm formation. The screened isolates were characterized and identified as Pychrobacter celer, Pychrobacter alimentarius and Kocuria rhizophila by 16S rRNA sequencing.

Methods

Biofilm forming bacteria were isolated by spread plate technique and subjected to screening by microtiter plate assay. The potent biofilm formers were identified by molecular characterization using 16S rRNA gene sequencing.

Results

Twelve bacterial isolates were obtained by pour plate technique and subjected to biofilm assay. Among the 12 isolates three isolates which showed maximum biofilm formation were subjected to molecular characterizationby 16S rRNA gene sequencing method. The isolates were identified as Pychrobacter celer, Pychrobacter alimentarius and Kocuria rhizophila. The EPS produced by the three biofilm forming bacteria was extracted and the protein and carbohydrate content determined.

Conclusion

Among the isolates screened, isolate 8 (Kocuria rhizophila) produced maximum protein and carbohydrate which was also in accordance with the results of microtiter plate assay.

     

Efficient inhibition of some multi-drug resistant pathogenic bacteria by bioactive metabolites from <Emphasis Type="Italic">Bacillus amyloliquefaciens</Emphasis> S<Subscript>5</Subscript>I<Subscript>4</Subscript> isolated from archaeological soil in Egypt

Sixty-eight bacterial cultures were isolated from 5 archaeological soils in Egypt. It is necessary to characterize bacteria from ancient temples to develop protection programs for such archaeological places. Purified bacterial cultures were then tested for their capability to inhibit some multi-drug resistant (MDR) pathogenic bacteria including Staphylococcus aureus, Listeria monocytogenes, Bacillus cereus, Escherichia coli and Klebsiella pneumoniae. Among the most active 10 antibacterial isolates, only one isolate designated as S₅I₄ was selected, characterized and identified as belonging to Bacillus amyloliquefaciens. The strain identification was confirmed by amplification of its 16S rRNA gene. The partial nucleotide sequence of the amplified 16S rRNA gene of the tested strain was submitted in GenBank with accession number AB813716. The physical and nutritional parameters were optimized to improve the production of antimicrobial agents by the B. amyloliquefaciens S₅I₄. The maximum antagonistic effect of this strain against the tested MDR pathogenic bacteria was achieved in presence of 1% galactose and 0.5% yeast extract at 37°C and pH 7.0 after 48 h incubation. The antibacterial compounds of B. amyloliquefaciens S₅I₄ were extracted, purified and characterized using spectroscopic analysis (IR, UV, proton NMR and MS). The compound having inhibitory activity was identified as butanedioic acid, octadecyl,1(1carboxy1methylethyl) 4octyl ester.     

Isolation and characterization of arsenic resistant bacteria from tannery wastes and agricultural soils in Thailand

Highly arsenic resistant bacteria (27 isolates), which had a minimum inhibitory concentrations (MICs) for arsenite and arsenate of ? 40 mM and > 400 mM, respectively, were isolated from tannery wastes and agricultural soils collected in Central Thailand. On the basis of the morphological, cultural, physiological and biochemical characteristics, and on the principal ubiquinone component and 16S rRNA gene sequence analyses, they were identified as nine isolates each ofKlebsiella (Groups 1 and 8) andAcinetobacter (Groups 2, 3 and 7), four isolates each ofPseudomonas (Groups 4 and 6) andComamonas (Group 5), and one isolate ofEnterobacter (Group 9). From these 27 isolates, only one isolate, A3-3 from the genusComamonas, appeared potentially capable of oxidizing arsenite to arsenate, as determined by silver nitrate staining of arsenite agar plates after colony growth.     

Characterization of a <Emphasis Type="Italic">Salmonella</Emphasis> Enteritidis bacteriophage showing broad lytic activity against Gram-negative enteric bacteria

In this study, we sought to isolate Salmonella Enteritidis-specific lytic bacteriophages (phages), and we found a lytic phage that could lyse not only S. Enteritidis but also other Gramnegative foodborne pathogens. This lytic phage, SS3e, could lyse almost all tested Salmonella enterica serovars as well as other enteric pathogenic bacteria including Escherichia coli, Shigella sonnei, Enterobacter cloacae, and Serratia marcescens. This SS3e phage has an icosahedral head and a long tail, indicating belong to the Siphoviridae. The genome was 40,793 base pairs, containing 58 theoretically determined open reading frames (ORFs). Among the 58 ORFs, ORF49, and ORF25 showed high sequence similarity with tail spike protein and lysozyme-like protein of Salmonella phage SE2, respectively, which are critical proteins recognizing and lysing host bacteria. Unlike SE2 phage whose host restricted to Salmonella enterica serovars Enteritidis and Gallinarum, SS3e showed broader host specificity against Gram-negative enteric bacteria; thus, it could be a promising candidate for the phage utilization against various Gram-negative bacterial infection including foodborne pathogens.     

Characterization and antimicrobial activity of the bioactive metabolites in streptomycete isolates

Twenty different streptomycete isolates were obtained from soils of southeast Serbia. Five isolates identified as Streptomyces hygroscopicus (SH100, SH101, SH102, SH103, and SH104) showed strong activity against Botrytis cinerea, a parasite found in domestic vines. These isolates were extensively studied for their in vitro antimicrobial activity against Gram-positive bacteria, Gram-negative bacteria, yeasts and fungi, and also antiviral activity against Herpes simplex. The results indicated that the obtained isolates were highly active against Botrytis cinerea, Candida albicans, and Herpes simplex, with an inhibition zone at ≥31 mm. The structure of the bioactive components was determined using elemental analysis, as well as UV/VIS, FTIR, and TLC.     

Cultivable butyrate-producing bacteria of elderly Japanese diagnosed with Alzheimer’s disease

The group of butyrate-producing bacteria within the human gut microbiome may be associated with positive effects on memory improvement, according to previous studies on dementia-associated diseases. Here, fecal samples of four elderly Japanese diagnosed with Alzheimer’s disease (AD) were used to isolate butyrate-producing bacteria. 226 isolates were randomly picked, their 16S rRNA genes were sequenced, and assigned into sixty OTUs (operational taxonomic units) based on BLASTn results. Four isolates with less than 97% homology to known sequences were considered as unique OTUs of potentially butyrate-producing bacteria. In addition, 12 potential butyrate-producing isolates were selected from the remaining 56 OTUs based on scan-searching against the PubMed and the ScienceDirect databases. Those belonged to the phylum Bacteroidetes and to the clostridial clusters I, IV, XI, XV, XIVa within the phylum Firmicutes. 15 out of the 16 isolates were indeed able to produce butyrate in culture as determined by high-performance liquid chromatography with UV detection. Furthermore, encoding genes for butyrate formation in these bacteria were identified by sequencing of degenerately primed PCR products and included the genes for butyrate kinase (buk), butyryl-CoA: acetate CoAtransferase (but), CoA-transferase-related, and propionate CoA-transferase. The results showed that eight isolates possessed buk, while five isolates possessed but. The CoA-transfer-related gene was identified as butyryl-CoA:4-hydroxybutyrate CoA transferase (4-hbt) in four strains. No strains contained the propionate CoA-transferase gene. The biochemical and butyrate-producing pathways analyses of butyrate producers presented in this study may help to characterize the butyrate-producing bacterial community in the gut of AD patients.     

Multi-locus sequence typing (MLST) of non-fermentative Gram-negative bacilli isolated from bloodstream infections in southern Poland

Non-fermentative Gram-negative bacilli are now one of the most important causes of severe infections in Polish hospitals. Acinetobacter species are serious concern because of the high prevalence of multi-drug resistance among strains. Resistance profiles for 53 Gram-negative non-fermentative blood isolates were done. MLST was carried out using 44 strains representing the most commonly isolated species: A. baumannii, P. aeruginosa, and S. maltophilia. MLST revealed that all 22 A. baumannii belonged to sequence type (ST) 2. The P. aeruginosa isolates belonged to 10 different STs. Four S. maltophilia isolates matched STs present in the database (ST4, ST15, ST116, ST142), seven isolates showing novel sequence types. Among P. aeruginosa and S. maltophilia PFGE confirmed the genetical variety of strains.     

<Emphasis Type="Italic">Lactobacillus plantarum</Emphasis> as a Probiotic Potential from Kouzeh Cheese (Traditional Iranian Cheese) and Its Antimicrobial Activity

The aim of this study is to isolate and identify Lactobacillus plantarum isolates from traditional cheese, Kouzeh, and evaluate their antimicrobial activity against some food pathogens. In total, 56 lactic acid bacteria were isolated by morphological and biochemical methods, 12 of which were identified as Lactobacillus plantarum by biochemical method and 11 were confirmed by molecular method. For analyzing the antimicrobial activity of these isolates properly, diffusion method was performed. The isolates were identified by 318 bp band dedicated for L. plantarum. The isolated L. plantarum represented an inhibitory activity against four of the pathogenic bacteria and showed different inhibition halos against each other. The larger halos were observed against Staphylococcus aureus and Staphylococcus epidermidis (15 ± 0.3 and 14.8 ± 0.7 mm, respectively). The inhibition halo of Escherichia coli was smaller than that of other pathogen and some L. plantarum did not show any inhibitory activity against E. coli, which were resistant to antimicrobial compounds produced by L. plantarum. The isolated L. plantarum isolates with the antimicrobial activity in this study had strong probiotic properties. These results indicated the nutritional value of Kouzeh cheese and usage of the isolated isolates as probiotic strains.     

Rapid MALDI biotyper-based identification and cluster analysis of <Emphasis Type="Italic">Streptococcus iniae</Emphasis>

Streptococcus iniae causes severe mortalities among cultured marine species, especially in the olive flounder (Paralichthys olivaceus), which is economically important in Korea and Japan. Recently, there has been growing concern regarding the emergence of S. iniae as a zoonotic pathogen. Here, 89 S. iniae isolates obtained from diseased olive flounders collected from 2003 to 2008 in Jeju Island, South Korea, were characterized using matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS). The results were aligned both with the available Bruker Daltonics data-base and with a new set of S. iniae data entries developed in our laboratory, and the results were compared. When we used the Bruker Daltonics database, the 89 isolates yielded either “no reliable identification” or were incorrectly identified as Streptococcus pyogenes at the genus level. When we used the new data entries from our laboratory, in contrast, all of the isolates were correctly identified as S. iniae at the genus (100%) and species (96.6%) levels. We performed proteomic analysis, divided the 89 isolates into cluster I (51.7%), cluster II (20.2%), and cluster III (28.1%), and then used the MALDI Biotyper software to identify specific mass peaks that enabled discrimination between clusters and between Streptococcus species. Our results suggest that the use of MALDI TOF MS could outperform the conventional methods, proving easier, faster, cheaper and more efficient in properly identifying S. iniae. This strategy could facilitate the epidemiological and taxonomical study of this important fish pathogen.     

Pine wilt disease and possible causes of its incidence in Russia

Surveys of forests and stockpiled timber of pine, spruce, larch, and silver fir in 14 administrative subjects of the Russian Federation revealed widespread occurrence of the coniferous wood parasitic nematode Bursaphelenchus mucronatus. Twenty species of bacteria belonging to 13 genera have been detected in 25 B. mucronatus isolates, and their identity has been determined by direct sequencing of the 16S RNA gene. The most frequently occurring were bacteria from the genera Pseudomonas, Stenotrophomonas, Pantoea, Bacillus, Burkholderia, and Serratia. Prevalence of Pseudomonas brenneri and P. fluorescence, which were also found in the nematode dauer larva (L_IV) isolated from the fir sawyer beetle Monochamus urussovi, have also been assessed. Two nematode B. xylophilus isolates from Portugal and one isolate from the United States have been examined, and 10 symbiotic bacteria species have been isolated, including Agrobacterium tumefacience, P. fluorescens, P. brenneri, Rahnella aquatilis, Stenotrophomonas maltophilia, S. rhizophila, and Yersinia mollaretii.     

Multilocus sequence typing for phylogenetic view and <Emphasis Type="Italic">vip</Emphasis> gene diversity of <Emphasis Type="Italic">Bacillus thuringiensis</Emphasis> strains of the Assam soil of North East India

An agriculturally important insecticidal bacterium, Bacillus thuringiensis have been isolated from the soil samples of various part of Assam including the Kaziranga National Park. Previously, the isolates were characterized based on morphology, 16S rDNA sequencing, and the presence of the various classes’ crystal protein gene(s). In the present study, the phylogenetic analysis of a few selected isolates was performed by an unambiguous and quick method called the multiple locus sequence typing (MLST). A known B. thuringiensis strain kurstaki 4D4 have been used as a reference strain for MLST. A total of four the MLST locus of housekeeping genes, recF, sucC, gdpD and yhfL were selected. A total of 14 unique sequence types (STs) was identified. A total number of alleles identified for the locus gdpD and sucC was 12, followed by locus yhfL was 11, however, only 6 alleles were detected for the locus recF. The phylogenetic analysis using MEGA 7.0.26 showed three major lineages. Approximately, 87% of the isolates belonged to the STs corresponding to B. thuringiensis, whereas two isolates, BA07 and BA39, were clustered to B. cereus. The isolates were also screened for the diversity of vegetative insecticidal protein (vip) genes. In all, 8 isolates showed the presence of vip1, followed by 7 isolates having vip2 and 6 isolates for vip3 genes. The expression of Vip3A proteins was analyzed by western blot analyses and expression of the Vip3A protein was observed in the isolate BA20. Thus, the phylogenetic relationship and diversity of Bt isolates from Assam soil was established based on MLST, in addition, found isolates having vip genes, which could be used for crop improvement.     

<Emphasis Type="Italic">Myroides injenensis</Emphasis> sp. nov., a new member isolated from human urine

A Gram-negative, yellow-pigmented, rod-shaped bacteria, designated M09-0166^Tand M09-1053 were isolated from human urine samples. 16S rRNA gene sequence analysis revealed that the isolates belong to the Myroides cluster and were closely related to Myroides phaeus DSM 23313^T (96.3 %), Myroides odoratimimus KCTC 23053^T (96.1 %), Myroides profundi KCTC 23066^T (96.0 %), Myroides odoratus KCTC 23054^T (95.4 %) and Myroides pelagicus KCTC 12661^T (95.2 %). The major mena quinone was identified as MK-6. The major polar lipids were identified as phosphatidylethanolamine, amino lipids, and several unknown lipids, and the major fatty acids as iso-C_15:0 and iso-C_17:0 3-OH. Phenotypic and chemotaxonomic data supported the affiliation of the isolates with the genus Myroides and clearly indicated that two isolates represent novel species, for which the name Myroides injenensis sp. nov. (type strain, M09-0166^T = KCTC 23367^T = JCM 17451^T) is proposed.     

Diversity of indigenous endophytic bacteria associated with the roots of Chinese cabbage (<Emphasis Type="Italic">Brassica campestris</Emphasis> L.) cultivars and their antagonism towards pathogens

The study aimed to reveal the diversity of endophytic bacteria in the roots of Chinese cabbage (CC) cultivated in two areas in Korea, namely, Seosang-gun (SS) and Haenam-gun (HN), and also in a transgenic plant (TP) from the laboratory. A total of 653 colonies were isolated from the interior of CC roots, comprising 118, 302, and 233 isolates from SS, HN, and TP samples, respectively. Based on 16S rRNA gene sequence analysis, the isolates belonged to four major phylogenetic groups: high-G+C Gram-positive bacteria (HGC-GPB), low-G+C Gram-positive bacteria (LGC-GPB), Proteobacteria, and Bacteriodetes. The most dominant groups in the roots of the SS, HN, and TP cultivars were LGC-GPB (48.3%), Proteobacteria (50.2%), and HGC-GPB (38.2%), respectively. Importantly, most of the isolates that produced cell-walldegrading enzymes belonged to the genus Bacillus. Bacillus sp. (HNR03, TPR06), Bacillus pumilus (SSR07, HNR11, TPR07), and Bacillus subtilis (TPR03) showed high antagonism against the tested food-borne pathogenic bacteria. In addition, Bacillus sp. (HNR03, TPR06), Bacillus pumilus (SSR07, HNR11, HNR17, TPR11), Microbacterium oxidans (SSR09, TPR04), Bacillus cereus HNR10, Pseudomonas sp. HNR13, and Bacillus subtilis (TPR02, TPR03) showed strong antagonistic activity against the fungi Phythium ultimum, Phytophthora capsici, Fusarium oxysporum, and Rhizoctonia solani. The endophytes isolated from the TP cultivar showed the strongest antagonistic reactions against pathogens. This study is the first report on endophytic bacteria from Chinese cabbage roots.     

Diagnosis and molecular characteristics of human infections caused by <Emphasis Type="Italic">Anaplasma phagocytophilum</Emphasis> in South Korea

Human granulocytic anaplasmosis (HGA) is a tick borne infection caused by Anaplasma phagocytophilum. HGA cases in South Korea have been identified since the first report in 2014. In this study, we investigated the serological response in 594 clinical samples of patients with acute febrile illness and molecular characteristics of A. phagocytophilum clinical isolates obtained from HGA patients. In serological test for A. phagocytophilum, 7.91% (47/594 cases) were positive for IgG and Ig M and 13 of 47 cases showed seroconversion. In the detection rate of the 16S rRNA, msp2(p44), and ankA, genes were showed 3.68% (14/380 cases) for A. phagocytophilum-specific 16S rRNA gene. Phylogenetic analysis of three clinical isolates demonstrated high sequence similarity (98.58–100%) with A. phagocytophilum 16S rRNA sequences identified from public databases. Analysis of the msp2(p44) gene showed highly variable similarity rates (7.24–98.85%) even within isolated countries and host ranges. These results provide clues into the bacterial characterization of A. phagocytophilum originating from Korean patients, providing useful guidance for treatment and improving clinical outcomes.     

Screening and molecular identification of lactic acid bacteria from <Emphasis Type="Italic">gari</Emphasis> and <Emphasis Type="Italic">fufu</Emphasis> and <Emphasis Type="Italic">gari</Emphasis> effluents

Bacterial strains were isolated from cassava-derived food products and, for the first time, from cassava by-products, with a focus on gari, a flour-like product, and the effluents from the production processes for gari and fufu (a dough also made from cassava flour). A total of 47 strains were isolated, all of which were tested to determine their resistance to acidic pH and to bile salt environments. Four of the 47 isolates tested positive in both environments, and these four isolates also showed antibacterial behaviour towards both Gram-positive and Gram-negative microbial pathogens (i.e. Methicillin-resistance Staphylococcus aureus, Listeria monocytogenes, Bacillus cereus, Salmonella enteritidis, Escherichia coli, Escherichia coli (O157), Yersinia enterocolitica). In most cases, the antibacterial activity was related to bacteriocin production. Molecular identification analysis (16S rDNA and randomly amplified polymorphic DNA-PCR) revealed that the four isolates were different strains of the same species, Lactobacillus fermentum. These results demonstrate that bacteria isolated from cassava-derived food items and cassava by-products have interesting properties and could potentially be used as probiotics.     

Possible Probiotic Lactic Acid Bacteria Isolated from Oysters (<Emphasis Type="Italic">Crassostrea gigas</Emphasis>)

We attempted to isolate lactic acid bacteria (LAB) from the marine oyster (Crassostrea gigas) and selected several environmental stress-resistant isolates for the development of a future probiotic adjuvant for marine aquaculture. Twenty-six presumptive LAB isolates were extracted from oysters and screened (by an agar diffusion assay) for antimicrobial activity toward various pathogens: Vibrio parahaemolyticus, Streptococcus iniae, and Edwardsiella tarda. Eight isolates had an antibacterial activity toward V. parahaemolyticus; in particular, 6 isolates showed a growth-inhibitory activity, with inhibition zone diameters > 15 mm. Of these, 5 isolates (JL17, JL18, JL28, HL7, and HL32) were also active against S. iniae and E. tarda. Enterococcus faecium HL7 was selected as the isolate most resistant to environmental stressors: the minimum NaCl, ethanol, and hydrogen peroxide concentrations at which HL7 cells lost their viability were 1.9 M, 11%, and 0.013%, respectively. When an antibiotic sensitivity test was performed on E. faecium HL7, this isolate was found to be resistant to trimethoprim/sulfamethoxazole, cephalothin, ampicillin, rifampin, gentamicin, cefotaxime, cefepime, cefotetan, nalidixic acid, and kanamycin. While the oyster model studies provided indication that E. faecium HL7 could be a good candidate as biocontrol agent against V. vulnificus, further optimization is needed in the actual animal rearing situation.