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PubMed2006

The crystal structure of L-lactate oxidase from Aerococcus viridans at 2.1A resolution reveals the mechanism of strict substrate recognition.

L-Lactate oxidase (LOX) from Aerococcus viridans is a member of the alpha-hydroxyacid-oxidase flavoenzyme family. We have determined the three-dimensional structure of LOX and revealed the mechanism of substrate recognition. The LOX monomer structure has a typical alpha(8)/beta(8) motif commonly found in other flavin family proteins. A related enzyme, glycolate oxidase, catalyzes the oxidation of glycolate rather than lactate. Comparison of the two enzyme structures highlights the importance of five residues around the FMN prosthetic group of LOX, which act synergistically to discriminate between the l/d configurations of lactate. X-ray crystallography of LOX gave a space group I422 of unit-cell parameters a=b=191.096A, c=194.497A and alpha=beta=gamma=90 degrees with four monomers per asymmetric unit. The four independent monomers display slight structural differences around the active site. Diffraction data were collected, under cryogenic conditions to 2.1A resolution at the synchrotron facilities in Japan.

Alcohol Oxidoreductases↗

PubMed2005

Clinical significance of Aerococcus urinae: a retrospective review.

A retrospective chart review was performed on 54 patients with positive urine cultures during a 1-year period to assess the clinical significance of Aerococcus urinae. Based on predetermined criteria, patients were classified into 2 groups: those with urinary tract infections (UTIs) and those who were considered colonized. The majority of the patients were > or =65 years old and were female. Only 31% of patients with UTI and 45% of colonized patients had A. urinae isolated in pure cultures. Both groups had significant but similar underlying medical conditions, with urologic conditions being predominant. Significantly more patients in the UTI group had urinary catheters (P < .01). No direct complications or invasive disease was recognized in either group regardless of whether patients were treated with antibiotics. Apparently, A. urinae is a relatively avirulent organism when cultured from urine.

Age Factors↗

PubMed2003

Classification of Homarus americanus hemocytes and the use of differential hemocyte counts in lobsters infected with Aerococcus viridans var. homari (Gaffkemia).

Hemocytes of the American lobster (Homarus americanus H. Milne Edwards) were classified after examination of Wright-Giemsa stained cytocentrifuge preparations by brightfield light microscopy. Eleven hemocyte types were identified using morphologic criteria. The classification system was then used to monitor changes in the differential hemocyte count (DHC) of lobsters infected with the Gram positive coccus Aerococcus viridans var. homari, etiologic agent of gaffkemia. The appearance of less mature hemocytes in the DHCs of lobsters in the late stages of infection was similar to the 'left shift' of vertebrate inflammation. Results from this study suggest that DHCs can be used to assess and characterize inflammation in H. americanus and possibly other crustaceans.

Animal Diseases↗

PubMed2002

Serum concentration of Hakata antigen, a member of the ficolins, is linked with inhibition of Aerococcus viridans growth.

BACKGROUND: Hakata antigen (Hakata) is a novel serum glycoprotein that consists of collagen- and fibrinogen-like domains, similar to ficolin/p35. Our research suggested that serum Hakata may be a target of a polysaccharide (PSA) produced by Aerococcus viridans. METHODS: A. viridans was incubated with human plasma and Hakata-depleted plasma to examine Hakata binding and growth inhibition of A. viridans through binding with PSA. RESULTS: When A. viridans was mixed with human acid citrate dextrose-one (ACD-A) plasma, it pulled down Hakata complexed with mannose-binding lectin (MBL)-associated serine proteases 1 and 2 (MASP-1 and MASP-2). This complex had the potential for C4 deposition. Serum Hakata circulates as Hakata-MASPs complex in the blood and is proteolytically active. By mixing A. viridans with human plasma, we prepared a Hakata-depleted plasma, deficient in Hakata-MASPs complex. This plasma failed to inhibit A. viridans growth plasma, but does not inhibit Staphylococcus aureus, Yersinia enterocolitica and Escherichia coli. However, a decrease of growth inhibition of A. viridans in Hakata-depleted plasma could be restored by adding a Hakata-MASPs complex preparation in a dose-dependent manner. On the other hand, the Hakata-MASPs complex exhibited strong binding to A. viridans, but not to S. aureus, Y. enterocolitica and E. coli. CONCLUSIONS: The serum concentration of Hakata is linked with growth inhibition of A. viridans upon binding of Hakata via PSA.

Carrier Proteins↗

PubMed1984

Aerococcus viridans endocarditis.

Aerococcus viridans organisms are gram-positive cocci with a strong tendency to form tetrads. These bacteria have infrequently been encountered as a human pathogen, particularly in bacterial endocarditis. A review of the literature suggests that treatment of A. viridans endocarditis should be similar to that for endocarditis caused by penicillin-susceptible streptococci.

Adult↗

PubMed1998

L-lactate oxidase from Aerococcus viridans crystallized as an octamer. Preliminary X-ray studies.

Crystals of flavoenzyme L-lactate oxidase from Aerococcus viridans (LOX) have been obtained that diffract to 3.0 A resolution (P2(1)2(1)2(1), a = 118.4 A, b = 138.4 A, c = 194.6 A). Crystallographic studies suggest that the enzyme may exist as an octameric form with non-crystallographic two- and four-fold axes in the center of the octamer. The four-fold axis makes the tetramer tight, and the tetramers lie upon one another by the two-fold axis.

Chromatography, Gel↗

PubMedDate not supplied

Two epidemics of pseudobacteremia due to Staphylococcus aureus and Aerococcus viridans.

Two epidemics of pseudobacteremia are reported. The first, due to Staphyloccus aureus, was caused by a physician who had active staphylococcal skin infection and nasal colonization. Because the blood culture system in use at the time was open, and used screw cap bottles, we assume that the physician contaminated the bottles at the time of inoculation. The second outbreak, caused by Aerococcus viridans, was traced to contamination of the blood culture bottle tops as they were received from the manufacturer. We assume that there was inadequate disinfection of the bottle tops by the physicians prior to their use.

Cross Infection↗

PubMedDate not supplied

Use of dye affinity chromatography for the purification of Aerococcus viridans lactate oxidase.

Lactate oxidase was purified from Aerococcus viridans (A. viridans) by dye affinity chromatography and FPLC ion exchange chromatography. The lactate oxidase could be purified by comparatively simple procedures, the purification achieved from a crude extract of A. viridans was 41-fold with a specific activity of 143 units/(mg of protein). The purified enzyme was a L-lactate oxidase, which catalyses the conversion of L-lactate in the presence of molecular oxygen to pyruvate and H(2)O(2). This purified lactate oxidase showed an apparent molecular mass of 48,200 in SDS-PAGE and the native molecular weight, as estimated by FPLC gel filtration, was 187,300. This molecular weight indicates that lactate oxidase exists in tetrameric form after gel filtration. To differing degrees, all the triazine dyes tested were inhibitors of lactate oxidase, solutions of free triazine dyes showing an inhibition mechanism which was both time- and pH-dependent.

Chromatography, Affinity↗

PubMed2003

Identification of Aerococcus urinae in urine samples.

To evaluate procedures for the identification of Aerococcus urinae, we examined 24 alpha-hemolytic non-enterococcal bacterial isolates from 4373 urine samples. Published procedures were compared with 16s rRNA sequencing and biochemical profiling (BBL-Crystal-GP). 16s rRNA sequencing and BBL-Crystal-GP identified the same 13 isolates as A. urinae. Published tests failed to distinguish the 13 A. urinae isolates from eight non-A. urinae isolates; several tests exhibited no discrimination. Ciprofloxacin and trimethoprim susceptibility and growth at 45 degrees C improved discrimination. For urinary isolates, standard procedures for identification of A. urinae are redundant and insufficiently discriminatory, and may need revision. BBL-Crystal-GP is an accurate alternative.

Adult↗

PubMed2000

Properties and stability of glycerophosphate oxidase isolated from a mutant strain of Aerococcus viridans.

The properties of microbial L-alpha-glycerophosphate oxidase (GPO) isolated from a mutant strain of Aerococcus viridans DBM 1509 were estimated. The stability at different temperatures and pH were detected. At 4 degrees C the enzyme lost activity during 15 d, at 20 degrees C and 30 degrees C GPO activity decreased during 30 and 25 h, respectively. The highest stability was measured at - 20 degrees C and pH 9. At 4 degrees C the stability was enhanced by the addition of 0.1 M EDTA or by lyophilization in the presence of dextrin. These conditions allow the prolongation of the low stability of microbial GPO which limited its use, and give the opportunity to increase the stability of other enzymes

Dextrins↗

PubMed2003

Lymphadenitis caused by Aerococcus urinae infection.

Aerococcus urinae is rarely reported as a human pathogen. The pathogenesis of this gram-positive coccus is not fully understood. It has been identified as a cause of urinary tract infections but may be associated with severe infections such as endocarditis and septicaemia. This paper presents a case of lymphadenitis caused by A. urinae.

Aged↗

PubMed2003

A study on the kinetic mechanism of apoenzyme reconstitution from Aerococcus viridans lactate oxidase.

The preparation of a reconstitutable apoprotein is widely recognized as an important tool for studying the interactions between protein and coenzyme and also for characterizing the coenzyme-binding site of the protein. Here is described the kinetic analysis of the reconstitution of Aerococcus viridans lactate oxidase apoenzyme with FMN and FAD in the presence of substrate. The reconstitution was followed by measuring the increase in catalytic capacity with time. Lactate oxidase activity was easily removed by obtaining its apoenzyme in an acidic saturated ammonium sulphate solution. When the apoenzyme was reconstituted by the addition of FMN or FAD, a marked lag period was observed, after which the system reached a steady state (linear rate). To explain the binding mechanism of the cofactors to the apoenzyme, a kinetic model is proposed, in which the constants, k3 and k-3, representing the interaction of apoenzyme with cofactor are considered slow and responsible for the lag in the expression of activity. The affinity of apoenzyme was 51-fold higher for FMN than FAD.

Binding Sites↗

PubMed1995

Bacteremia/septicemia due to Aerococcus-like organisms: report of seventeen cases. Danish ALO Study Group.

Some Aerococcus-like organisms (ALOs) have recently been described in Denmark. The bacteria were originally isolated from the urine of elderly patients with urinary tract infections. Since 1987, we have identified 17 cases of bacteremia/septicemia in which ALOs have been isolated in pure culture of blood; we report the data from these cases. Six of the patients presented with endocarditis, eight presented with urosepticemia, and three presented with septicemia. In all but one of the reports, the urinary tract was suspected as the focus of infection, and ALOs were isolated from the urine of nine patients. All but one patient had predisposing illnesses; these were predominantly of urinary or cardiac origin. Five patients died of their infection, two survived the infection but eventually died during hospitalization, and 10 recovered. All of the patients received adequate antimicrobial therapy.

Aged↗

PubMed2001

In vitro antimicrobial susceptibility of Aerococcus urinae to 14 antibiotics, and time-kill curves for penicillin, gentamicin and vancomycin.

Aerococcus urinae is a newcomer in clinical and microbiological practice, causing urinary tract infections, bacteraemia/septicaemia and/or endocarditis. This study presents for the first time an evaluation of the activity of a representative panel of antibiotics against a large number of A. urinae isolates. The in vitro susceptibilities (MICs) of 56 isolates of A. urinae to 14 antibiotics were determined by agar dilution. In general, A. urinae isolates showed little inter-isolate variability, and had low MICs of penicillin, amoxicillin, piperacillin, cefepime, vancomycin and rifampicin. High-level aminoglycoside resistance was not found for any of the isolates. Moderate to good activity was seen with quinolones, erythromycin and tetracycline. Isolates from two patients with endocarditis were studied with time-kill curves for penicillin, gentamicin and vancomycin. Penicillin and vancomycin alone exhibited slow or no bactericidal activity against the two strains. When combining either penicillin or vancomycin with gentamicin, rapid bactericidal activity was obtained for both strains with both combinations. The treatment options for A. urinae seem to include penicillins for less severe cases. In severe cases, i.e. endocarditis, the time-kill investigations suggest a beneficial effect of combination with gentamicin. In the penicillin-allergic patient vancomycin in combination with gentamicin represents the most obvious alternative.

Anti-Bacterial Agents↗

PubMed2002

Superior vena cava syndrome caused by Aerococcus viridans para-aortic abscess after heart transplantation.

Superior vena cava (SVC) syndrome is usually caused by extrinsic compression by malignant tumors, but para-aortic abscess can be responsible for this syndrome. We report a case of SVC syndrome caused by para-aortic abscess caused by Aerococcus viridans infection in a man who received orthotopic heart transplantation. A. viridans is a common saprophytic organism in hospital environments. There are reports of this organism being the cause of endocarditis, but no reports of it as the cause of a para-aortic abscess. This is a first report of A. viridans infection in organ transplant patients.

Abscess↗

PubMed1977

Serological grouping of virulent and avirulent strains of the lobster pathogen Aerococcus viridans.

Virulent strains of Aerococcus viridans (formerly Gaffkya homari) are the aetiologic agents of gaffkemia, a septicaemic disease of the American lobster (Homarus americanus). The virulent and avirulent forms of this bacterium, previously thought to be taxonomically indistinguishable, have been differentiated by serological studies. Antisera were produced in rabbits using autoclaved bacteria as antigens. Reactions were measured by agglutination tests using microtitre techniques and an antigenic scheme was determined. Specific antisera were prepared by absorption and used to determine antigens of strains of A. viridans and other Gram-positive cocci. In general, only virulent strains of A. viridans have antigen b. Both virulent and avirulent strains possess other antigens also detected in strains of the genus Staphylococcus.

Agglutination Tests↗

PubMed2005

Crystallization and preliminary X-ray diffraction study of L-lactate oxidase (LOX), R181M mutant, from Aerococcus viridans.

L-Lactate oxidase (LOX) from Aerococcus viridans is a member of the alpha-hydroxyacid oxidase flavoenzyme family. An X-ray crystallographic study of a LOX mutant in which Arg181 is replaced by Met was initiated in order to understand the functions of the conserved amino-acid residues around the FMN in the enzyme active site. LOX-R181M crystals belong to the tetragonal space group I422, with unit-cell parameters a = b = 192.632, c = 200.263 A, alpha = beta = gamma = 90 degrees. There are four monomers in the asymmetric unit. Diffraction data were collected under cryogenic conditions to 2.44 A resolution from LOX-R181M crystals at BL41XU, SPring-8.

Binding Sites↗

PubMed2006

The 2.1 A structure of Aerococcus viridans L-lactate oxidase (LOX).

The crystal structure of L-lactate oxidase (LOX) from Aerococcus viridans has been determined at 2.1 A resolution. LOX catalyzes the flavin mononucleotide (FMN) dependent oxidation of lactate to pyruvate and hydrogen peroxide. LOX belongs to the alpha-hydroxy-acid oxidase flavoenzyme family; members of which bind similar substrates and to some extent have conserved catalytic properties and structural motifs. LOX crystallized as two tightly packed tetramers in the asymmetric unit, each having fourfold symmetry. The present structure shows a conserved FMN coordination, but also reveals novel residues involved in substrate binding compared with other family members.

Amino Acid Sequence↗