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PubMed1999

Molecular and physiological characterization of dominant bacterial populations in traditional mozzarella cheese processing

The development of the dominant bacterial populations during traditional Mozzarella cheese production was investigated using physiological analyses and molecular techniques for strain typing and taxonomic identification. Analysis of RAPD fingerprints revealed that the dominant bacterial community was composed of 25 different biotypes, and the sequence analysis of 16S rDNA demonstrated that the isolated strains belonged to Leuconostoc mesenteroides subsp. mesenteroides, Leuc. lactis, Streptococcus thermophilus, Strep. bovis, Strep. uberis, Lactococcus lactis subsp. lactis, L. garviae, Carnobacterium divergens, C. piscicola, Aerococcus viridans, Staphylococcus carnosus, Staph. epidermidis, Enterococcus faecalis, Ent. sulphureus and Enterococcus spp. The bacterial populations were characterized for their physiological properties. Two strains, belonging to Strep. thermophilus and L. lactis subsp. lactis, were the most acidifying; theL. lactis subsp. lactis strain was also proteolytic and eight strains were positive to citrate fermentation. Moreover, the molecular techniques allowed the identification of potential pathogens in a non-ripened cheese produced from raw milk.

Journal Article↗

PubMed2000

On the interpretation of quantitative structure-function activity relationship data for lactate oxidase.

The native flavin, FMN, has been removed from the l-lactate oxidase of Aerococcus viridans, and the apoprotein reconstituted with 12 FMN derivatives with various substituents at the flavin 6- and 8-positions. Impressive linear relationships are exhibited between the sum of the Hammett final sigma(para) and final sigma(ortho) parameters and the redox potentials of the free flavins, and between the redox potentials of the free and enzyme-bound flavins. Rapid reaction kinetics studies of the reconstituted enzymes with the substrates l-lactate and l-mandelate show an increase in the reduction rate constant with increasing redox potential, except that, with lactate, a limiting rate constant of approximately 700 s(-1) is obtained with flavins of high potential. Similar breakpoints are found in plots of the rate constants for flavin N5-sulfite adduct formation and for the reaction of the reduced enzymes with molecular oxygen. These results are interpreted in terms of a two-step equilibrium preceding the chemical reaction step, in which the second equilibrium step provides an upper limit to the rate with which the particular substrate or ligand is positioned with the flavin in the correct fashion for the observed chemical reaction to occur. The relationship of rate constants for flavin reduction and N5-sulfite adduct formation with flavin redox potential below the observed breakpoint indicate development of significant negative charge in the transition states of the reactions. In the case of reduction by substrate, the results are consistent either with a hydride transfer mechanism or with the so called "carbanion" mechanism, in which the substrate alpha-proton is abstracted by an enzyme base protected from exchange with solvent. These conclusions are supported by substrate alpha-deuterium isotope effects and by solvent viscosity effects on sulfite binding.

Apoenzymes↗

PubMed2000

Interaction of two arginine residues in lactate oxidase with the enzyme flavin: conversion of FMN to 8-formyl-FMN.

Two arginine residues, Arg-181 and Arg-268, are conserved throughout the known family of FMN-containing enzymes that catalyze the oxidation of alpha-hydroxyacids. In the lactate oxidase from Aerococcus viridans, these residues have been changed to lysine in two single mutations and in a double mutant form. In addition, Arg-181 has been replaced by methionine to determine the effect of removing the positive charge on the residue. The effects of these replacements on the kinetic and thermodynamic properties are reported. With all mutant forms, there are only small effects on the reactivity of the reduced flavin with oxygen. On the other hand, the efficiency of reduction of the oxidized flavin by l-lactate is greatly reduced, particularly with the R268K mutant forms. The results demonstrate the importance of the two arginine residues in the binding of substrate and its interaction with the flavin, and are consistent with a previous hypothesis that they also play a role of charge neutralization in the transition state of substrate dehydrogenation. The replacement of Arg-268 by lysine also results in a slow conversion of the 8-CH(3)- substituent of FMN to yield 8-formyl-FMN, still tightly bound to the enzyme, and with significantly different physical and chemical properties from those of the FMN-enzyme.

Amino Acid Sequence↗

PubMed1996

Conversion of L-lactate oxidase to a long chain alpha-hydroxyacid oxidase by site-directed mutagenesis of alanine 95 to glycine.

A mutant form of L-lactate oxidase (LOX) from Aerococcus viridans in which alanine 95 was replaced by glycine was constructed as a mimic of L-lactate monooxygenase but proved instead to be a mimic of the long chain alpha-hydroxyacid oxidase from rat kidney. A95G-LOX keeps oxidase activity with L-lactate at the same level as wild type LOX but has much enhanced oxidase activity with longer chain L-alpha-hydroxyacids, alpha-hydroxy-n-butyric acid, alpha-hydroxy-n-valeric acid, etc., and also the aromatic alpha-hydroxyacid, L-mandelic acid. Kinetic analysis of the activity with these substrates indicates that the reduction of the enzyme bound flavin by substrates is the rate-limiting step in A95G-LOX. The affinity of pyruvate for the reduced enzyme is increased, and sulfite binding to the oxidized enzyme is weaker in A95G-LOX than in native enzyme. Wild type LOX stabilizes both the neutral and anionic flavin semiquinones with a pKa of 6.1, but A95G LOX stabilizes only the anionic semiquinone form. These results strongly suggest that the environment around the N5-C4a region of the flavin isoalloxazine ring is changed by this mutation.

Alanine↗

PubMed2004

L-ficolin is a pattern recognition molecule specific for acetyl groups.

L-ficolin and H-ficolin are molecules of the innate immune system. Upon recognition of a suitable target they activate the complement system. The ligand recognition structure of ficolins is contained within a fibrinogen-like domain. We examined the selectivity of the ficolins through inhibiting the binding to bacteria or to beads coupled with N-acetylglucosamine. The binding of L-ficolin to Streptococcus pneumoniae 11F and the beads was inhibited by N-acetylated sugars and not by non-acetylated sugars. However, it was also inhibited by other acetylated compounds. Based on this selectivity L-ficolin is not easily defined as a lectin. The binding of H-ficolin to Aerococcus viridans was not inhibited by any of the sugars or other compounds examined. Based on the selectivity of L-ficolin we developed a new purification procedure involving affinity chromatography on N-acetylcysteine-derivatized Sepharose. The column was loaded in the presence of EDTA and high salt, and L-ficolin was eluted by decreasing the salt concentration. Further purification was achieved by ion exchange chromatography.

Acetylation↗

PubMed1989

Root canal microflora: qualitative changes after endodontic instrumentation.

The changes in the pattern of bacteria in root canal after repeated washing with NaOCl and endodontic instrumentation were evaluated. Samples were obtained from the root canals of patients before and after endodontic instrumentation, and analyzed according to the usual microbiological techniques. Washing with NaOCl and endodontic instrumentation act against bacteria such as Peptostreptococci, Streptococcus sanguis, Actinomyces israelii, Proteus mirabilis, Bacteroides, whereas Streptococcus lactis and Aerococcus were present before and after endodontic instrumentation. Environmental conditions such as low pH could be responsible for the persistence of gram-positive bacteria. The use of topical treatment and the associated endodontic instrumentation seem useful in the eradication of some bacteria in the root canal.

Dental Care↗

PubMed2003

Macrolide and lincosamide resistance in the gram-positive nasal and tonsillar flora of pigs.

Macrolide and lincosamide resistance phenotypes and the presence of the erm(A), erm(B), erm(C), and mef(A) genes were determined in 344 bacterial strains belonging to 34 species and nine genera, isolated from the tonsils and nasal cavities of 2-week- and 6-week-old piglets, derived from four different farms. These piglets had never before been treated with macrolides or lincosamides. Macrolide and lincosamide resistance was most frequently present in Streptococcus and Enterococcus strains, of which over two-thirds were resistant. These genera were followed in decreasing order of resistance frequency by Lactobacillus, Rothia, Staphylococcus, Arcanobacterium, Actinomyces, Pediococcus strains. Only five infrequently occurring species did not show resistance. This high frequency of resistance in nontreated piglets indicates that resistant strains circulate in the herds. In streptococci, enterococci, and Lactobacillus strains, resistance was most often encoded by the erm(B) gene and in staphylococci by erm(A) or erm(C). The erm(B) gene was sporadically detected in other bacterial genera (Actinomyces, Rothia, Aerococcus, Pediococcus). The sequence of the erm(B) gene of 29 strains of 11 pigs originating from the four different farms was determined. This sequence was identical in 12 strains and only differed by 1-6 nucleotides in the other strains, indicating that exchanges of resistance genes might occur between bacterial species and genera belonging to the nasal or tonsillar flora of piglets.

Animals↗

PubMed1988

A comparison of the identification of group A streptococci and enterococci by two rapid pyrrolidonyl aminopeptidase methods.

Group A streptococci and enterococci can be differentiated from other streptococci by their ability to cleave L-pyrrolidonyl-beta-napthylamide (PYR). The authors evaluated two pyrrolidonyl aminopeptidase (PYRase) systems--Minitek (BBL Microbiology Systems, Cockeysville, MD) and Identicult-AE (Scott Laboratories, Inc., Fiskeville, RI)--for the presumptive identification of Group A streptococci and enterococci. Eighty-three Group A streptococci, 77 beta-hemolytic non-Group A streptococci, 74 enterococci, 56 nonenterococcal non-beta-hemolytic streptococci, 1 Streptococcus pneumoniae, and 1 Aerococcus were tested. Compared with results obtained with reference methods (bile esculin agar and 6.5% [w/v] sodium chloride for identification of enterococci, and latex agglutination tests by Streptex [Burroughs Wellcome, NC] for grouping of beta-hemolytic streptococci) both the Identicult-AE and MInitek systems were 100% sensitive and specific for identification of both enterococci and Group A beta-hemolytic streptococci. Advantages of the Identicult-AE system compared with Minitek were the use of a smaller inoculum for which subculture was not necessary, incubation at room temperature rather than at 37 degrees C, and lower cost. Both PYRase kits tested, and in particular the Identicult-AE system, were very easy to use and should be considered as rapid, reliable, and cost-effective alternative methods for the presumptive identification of Group A streptococci and enterococci in the clinical laboratory.

Aminopeptidases↗

PubMed1992

Interactions between bacteria and influenza A virus in the development of influenza pneumonia.

Different proteases from various microorganisms present in the respiratory tract were capable of enhancing influenza virus infectivity and pathogenicity in mice by proteolytic activation of hemagglutinin (HA). Aerococcus viridans, isolated from a patient with pneumonia, secreted a protease that could activate HA directly, similarly to some Staphylococcus aureus strains. The protease of Pseudomonas aeruginosa could not activate HA directly, but combined application of P. aeruginosa protease and virus into mice enhanced virus titers and pathogenicity. Generation of trypsin-like activity in bronchoalveolar lavage fluids resulting from this combination treatment may be responsible for HA activation. A similar indirect effect on HA activation was induced by streptokinase and staphylokinase, which are known to generate plasmin by plasminogen activation. It was concluded that plasminogen-activating streptococci and staphylococci facilitate viral replication and pathogenicity of plasmin-sensitive influenza virus strains by amplification of the plasminogen/plasmin system.

Animals↗

PubMed1995

Transfer of Streptococcus adjacens and Streptococcus defectivus to Abiotrophia gen. nov. as Abiotrophia adiacens comb. nov. and Abiotrophia defectiva comb. nov., respectively.

We performed this study to determine the 16S rRNA sequences of the type strains of Streptococcus adjacens and Streptococcus defectivus and to calculate the phylogenetic distances between these two nutritionally variant streptococci (NVS) and other members of the genus Streptococcus. S. adjacens and S. defectivus belonged to one cluster, but this cluster was not closely related to other streptococcal species. A comparative analysis of the sequences of these organisms and other low-G+C-content gram-positive bacteria revealed that the two NVS species formed a distinct cluster and were only remotely related to the Aerococcus and Carnobacterium clusters. The highest level of homology (93.7%) was found between S. adjacens and Carnobacterium divergens. Carnobacterium species have meso-diaminopimelic acid in their cell walls, but S. adjacens and S. defectivus have L-lysine as the diamino acid at position 3 in their peptidoglycan tetrapeptides. On the basis of our findings and the results of previous phenotypic studies, we propose that the NVS species should be placed in a new genus, the genus Abiotrophia, as Abiotrophia adiacens comb. nov. and Abiotrophia defectiva comb. nov.

Base Sequence↗

PubMed2002

Carnobacterium viridans sp. nov., an alkaliphilic, facultative anaerobe isolated from refrigerated, vacuum-packed bologna sausage.

A facultatively anaerobic, non-spore-forming, psychrophilic, gram-positive, non-aciduric but alkaliphilic, rod-shaped bacterium (MPL-11T) was found to be responsible for green discoloration of refrigerated vacuum-packaged bologna upon opening of the package. Although Aerococcus viridans, which had been implicated earlier in causing the same problem, was also found, this is the first report of discoloration caused by an organism shown to be a species of Carnobacterium. Bacterial discoloration was caused by H2O2 production upon exposure of the meat to air. Strain MPL-11T is catalase- and oxidase-negative. It is not motile and does not reduce nitrate to nitrite or produce ammonia from arginine. It does not grow in acetate-containing broth or agar (Rogosa) or produce H2S. The peptidoglycan is of the meso-diaminopimelic acid type and it produces predominantly L(+)-lactic acid from glucose. It grows from at least 2 to 30 degrees C over a pH range from 5.5 to 9.1. Ribotyping suggested that strain MPL-11T could be a species of either Lactobacillus or Carnobacterium, but analysis using DNA sequences from the 16S rRNA gene showed conclusively that the organism belonged to the genus Carnobacterium. Since acid is not produced from amygdalin, inulin, mannitol, methyl alpha-D-glucoside or D-xylose, the organism differs from the seven described species of Carnobacterium. In addition, strain MPL-11T is the first member of the genus found that does not produce acid from ribose. It is capable of acid production/growth on galactose, glucose, fructose, mannose, N-acetylglucosamine, aesculin, cellobiose, maltose, lactose, sucrose, trehalose and tagatose. Although extremely salt tolerant, it does not grow in > or = 4% NaCl. On the basis of phenotypic and genotypic data, it is concluded that this isolate represents a separate, novel species. Accordingly, the name Carnobacterium viridans sp. nov. is proposed. The type strain is strain MPL-11T (= ATCC BAA-336T = DSM 14451T).

DNA, Bacterial↗

PubMed1983

Numerical taxonomy of Streptococcus.

A numerical taxonomic study of strains of Streptococcus, together with representatives of allied genera, showed 28 reasonably distinct phenons. The major areas, with their phenons, were: (a) enterococcal species group (S. faecalis, S. faecium, 'S. avium' and a proposed new species 'S. gallinarum'); (b) paraviridans species group (S. bovis, S. equinus, S. salivarius, 'S. casseliflavus', S. mutans, S. raffinolactis and an unidentified Oral Group I); (c) lactic species group (S. lactis including S. cremoris); (d) thermophilic species group (S. thermophilus); (e) viridans species group (S. mitis, S. sanguis, a proposed new species 'S. oralis' and 'S. milleri'); (f) pyogenic species group (S. agalactiae, S. pyogenes, S. equi, 'S. equisimilis' including 'S. zooepidemicus, and a cluster of Lancefield Group B strains of human origin); (g) parapyogenic species group (S. uberis, 'S. dysgalactiae', and a cluster of strains of Lancefield Groups R, S and T). Species of Aerococcus, Gemella, Leuconostoc and Pediococcus are very closely related to the streptococci.

Enterococcus faecalis↗

PubMed2000

Serological properties of Abiotrophia and Granulicatella species (nutritionally variant streptococci).

Serological variations were examined among 12 type or reference strains and 91 oral isolates of vitamin B6-dependent Abiotrophia and Granulicatella spp. Rabbits were immunized with whole cells of 12 selected strains and 10 typing antisera were obtained, which were unreactive with the Lancefield group A to G antigen preparations. The reactivity of the antisera and autoclaved cell surface antigen extracts was tested by double diffusion in agar gel and a capillary precipitin test. These typing antisera categorized all Abiotrophia defectiva strains, all except one Granulicatella elegans strain, three-quarters of the Granulicatella adiacens, and half of the Granulicatella paraadiacens into 8 serotypes and 2 subserotypes. The Granulicatella balaenopterae type strain was unserotypable. All A. defectiva strains were serotype I, some of which were divided into subserotype I-1 and/or I-5. The G. adiacens strains generally belonged to serotype II or III, and the G. paraadiacens strains to serotype IV, V or VI. All G. adiacens or G. paraadiacens serotype II strains were also subserotype I-5. The G. elegans strains were serotype VII or VIII. These Abiotrophia and Granulicatella serotypes were undetectable among 33 strains of the other 11 species including the bacteriolytic enzyme-producing but vitamin B6-independent strains of Streptococcus, Enterococcus, Dolosigranulum and Aerococcus. The proposed serotyping system for Abiotrophia and Granulicatella spp. would be helpful in the identification and classification of these unique coccal isolates in ecological and epidemiological studies.

Animals↗

PubMed1989

Studies on antagonism between porcine skin bacteria.

Strains of Staphylococcus warneri, Staph. epidermidis and Aerococcus viridans isolated from porcine skin were shown to produce substances that inhibited the growth of Staph. hyicus. Studies of interactions between the inhibitor-producing bacteria and Staph. hyicus on cellulose acetate membranes demonstrated a significant reduction (P less than 0.001) of the Staph. hyicus population at various stages of its growth cycle, depending on the inhibitor used. Inhibitor production profiles in batch culture showed a change in production with culture growth. Trypsin and an extracellular substance from Staph. hyicus had similar effects in reducing inhibitor production. Staphylococcus hyicus was shown to produce varying amounts of a proteolytic enzyme during growth in batch culture. Such in vitro models of bacterial interaction enable potential mechanisms of disease control using inhibitor-producing organisms to be investigated and provide a basis for studies in vivo.

Animals↗

PubMed2005

M-ficolin, an innate immune defence molecule, binds patterns of acetyl groups and activates complement.

Ficolins play a role in the innate immune defence as pathogen-associated molecular pattern recognition molecules. Three ficolins are found in humans: H-ficolin, L-ficolin and M-ficolin. L-ficolin and H-ficolin circulate in blood in complexes with mannan-binding lectin-associated serine proteases (MASPs) and are capable of activating the complement system. L-ficolin shows affinity for acetylated compounds and binds to various capsulated strains of bacteria. H-ficolin has been shown to bind Aerococcus viridans. Less is known about M-ficolin, but it is thought to be present only on monocytes. We have synthesized recombinant M-ficolin and find that it, in a manner similar to L-ficolin, is able to bind to acetylated compounds and to associate with recombinant MASP-2. Upon binding to M-ficolin ligands, the associated MASP-2 zymogen is activated and cleaves C4, thus triggering the complement system. We developed a monoclonal rat anti-human-M/L-ficolin antibody and verified by flow cytometric analysis the presence of ficolin on the surface of peripheral blood monocytes.

Acetylation↗

PubMed1995

The direct application of the polymerase chain reaction to DNA extracted from foods.

Two methods for the successful extraction of DNA from foods are described. The rapid lysis method uses a proteinase K buffer system to lyse cells and solubilize food samples. DNA is then precipitated using isopropanol. The second method achieves cell lysis using toluene and mutanolysin, and solubilization using guanidium thiocyanate. Following protein removal with organic solvents DNA is precipitated with isopropanol. Both methods enabled the polymerase chain reaction to be applied directly to DNA extracted from samples of cheese, coleslaw and raw chicken and allowed the direct rapid, sensitive and specific detection of Yersinia enterocolitica, Aerococcus viridans and Listeria monocytogenes in these foods.

Base Sequence↗

PubMed1996

Inhibition of peptidoglycan biosynthesis in vancomycin-susceptible and -resistant bacteria by a semisynthetic glycopeptide antibiotic.

LY191145 is a p-chlorobenzyl derivative of LY264826 (A82846B) with activity against both vancomycin-susceptible and -resistant enterococci. Incorporation of L-[14C]lysine into peptidoglycan of intact vancomycin-susceptible and -resistant Enterococcus faecium was inhibited by LY191145 (50% inhibitory concentrations of 1 and 5 microgram/ml, respectively). Inhibition was accompanied by accumulation of UDP-muramyl-peptide precursors in the cytoplasm. This agent inhibited late-stage steps in peptidoglycan biosynthesis in permeabilized E. faecium when either the UDP-muramyl-pentapeptide precursor from vancomycin-susceptible E. faecium or the UDP-muramyl-pentadepsipeptide precursor from vancomycin-resistant E. faecium was used as a substrate. Inhibition of late-stage steps led to accumulation of an N-acetyl-[14C]glucosamine-labeled lipid intermediate indicative of inhibition of the transglycosylation step. Inhibition of peptidoglycan polymerization without affecting cross-linking in a particulate membrane-plus-wall-fragment assay from Aerococcus viridans was consistent with this explanation. The fact that inhibition of peptidoglycan biosynthesis by LY191145 was not readily antagonized by an excess of free acyl-D-alanyl-D-alanine or acyl-D-alanyl-D-lactate ligands indicates that the manner in which this compound inhibits transglycosylation may not be identical to that of vancomycin.

Anti-Bacterial Agents↗

PubMed1997

In vitro antibacterial activity of LY333328, a new semisynthetic glycopeptide.

LY333328 is a semisynthetic N-alkyl derivative of LY264826, a naturally occurring structural analog of vancomycin. LY333328 was evaluated for its in vitro inhibitory and bactericidal activities in comparison with those of the two currently available glycopeptides (vancomycin and teicoplanin). Glycopeptide-susceptible test strains included a total of 311 isolates (most of clinical origin) from the genera Staphylococcus, Enterococcus, Streptococcus, Aerococcus, Gemella, Lactococcus, Listeria, Corynebacterium, and Clostridium. Test strains resistant or intermediate to vancomycin and/or teicoplanin included 56 clinical isolates of Enterococcus (of the VanA, VanB, and VanC phenotypes) and 32 clinical isolates of Staphylococcus (S. haemolyticus, S. epidermidis, and S. aureus), 31 strains of gram-positive genera outside the spectrum of activity of vancomycin (Leuconostoc, Pediococcus, Lactobacillus, and Erysipelothrix), and laboratory-derived organisms obtained after exposure of susceptible Staphylococcus isolates to teicoplanin (6 strains) or laboratory-derived organisms with resistance determinants received from VanA enterococci (2 Enterococcus and 25 Listeria transconjugants). LY333328 was highly active against staphylococci, enterococci, and listeriae (whether they were clinical or laboratory-derived strains) resistant to the currently available glycopeptides. In particular, the MICs of LY333328 did not vary substantially between teicoplanin-susceptible and teicoplanin-resistant staphylococci and between vancomycin-susceptible and vancomycin-resistant enterococci. LY333328 demonstrated fairly good inhibitory activity even against most strains of Leuconostoc, Pediococcus, and Erysipelothrix (MIC range, 1 to 8 microg/ml), whereas it proved less active (although much more active than vancomycin or teicoplanin) against Lactobacillus strains. In minimal bactericidal concentration (MBC) and time-kill studies, LY333328 demonstrated excellent bactericidal activity; enterococci, in particular, which were largely tolerant of vancomycin and teicoplanin, were uniformly killed by LY333328, with MBC-to-MIC ratios of 4 to 8 for most vancomycin-susceptible and vancomycin-resistant strains. In attempts to select for resistant clones, no survivors stably growing in the presence of 10 microg of LY333328 per ml were obtained from the Staphylococcus and Enterococcus test strains exposed to the drug.

Anti-Bacterial Agents↗