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PubMed1993

Effect of H1 histone isoforms on the methylation of single- or double-stranded DNA.

The loosely and tightly bound H1 histone isoforms were shown to exert, on the in vitro methylation of linker DNA in H1-depleted oligonucleosomes, inhibitory or activating effects respectively similar to those previously shown in the methylation of Micrococcus luteus dsDNA. When assayed on the enzymic methylation of Micrococcus luteus ssDNA, addition of the tightly bound one resulted in a stimulation similar to that exerted on double-stranded bacterial DNA or on linker DNA from mammalian chromatin, while the loosely bound isoform had no effect whatsoever. The transformation of the "typical" loosely bound H1 isoform into its tightly bound counterpart can be visualized as being an essential event in the modulation of DNA methylation process in eukaryotic chromatin.

Cell Nucleus↗
PubMed2006

Bacterial endosymbionts of Pyrodinium bahamense var. compressum.

The study presents evidence in support of the bacterial theory associated with the toxicity of Pyrodinium bahamense var. compressum. Bacterial endosymbionts from Philippine P. bahamense var. compressum strain Pbc MZRVA 042595 were isolated and identified via 16S rDNA sequence analysis. Taxonomic diversity of the identified culturable intracellular microbiota associated with Philippine P. bahamense var. compressum was established to be limited to the Phyla Proteobacteria, Actinobacteria, and Firmicutes. Major endosymbionts identified included Moraxella spp., Erythrobacter spp., and Bacillus spp., whereas Pseudomonas putida, Micrococcus spp., and Dietzia maris were identified as minor isolates. All identified strains except D. maris, P. putida, and Micrococcus spp. were shown to contain either saxitoxin or neo saxitoxin or both at levels < or =73 ng/10(7) bacterial cells based on high-performance liquid chromatography analysis. Paralytic shellfish poisoning-like physiologic reactions in test animals used in the mouse assay were recorded for the endosymbionts except for P. putida. The study is the first to elucidate the possible contribution of bacterial endosymbionts in the toxicity of P. bahamense var. compressum isolated in the Philippines.

Animals↗
PubMed1990

Cation-dependent solubilization of rat thymocyte chromatin is closely related to decondensation of the nuclei.

The cation-dependent solubilization of rat thymocyte chromatin has been compared with decondensation of the nuclei as a function of sodium phosphate-mediated changes in the concentration of Mg2+ and Na+. After digestion of the nuclei with DNase I or Micrococcus nuclease for a time just sufficient to permit extraction of a maximal amount of chromatin (minimum digestion), solubilization of most of the chromatin was found to occur with the same cation dependency as decondensation of untreated nuclei, while further digestion changed the ionic requirements for solubilization. The cation-dependency of the chromatin solubility and of the nuclear decondensation also exhibited the same variations with temperature. The chromatin in the nuclei became up to 4-times more sensitive to DNase I by decondensation, which also induced a shift in the DNase I cleavage mode from a 200 bp to a 100 bp repeat pattern. In contrast, the sensitivity to Micrococcus nuclease appeared to be nearly unchanged. These results suggest that solubilization of chromatin prepared by a mild endonuclease treatment occurs as a direct consequence of structural changes in the chromatin which take place during decondensation of the nuclei.

Animals↗
PubMed1992

Culture media for non-sporulating gram-positive food spoilage bacteria.

The spoilage association especially of protein-rich foods can be dominated by Gram-positive bacteria, notably lactic acid bacteria (LAB) which affect vacuum packaged refrigerated processed meats and some dairy products. New food ecosystems are being created by novel packaging and processing technologies, resulting in spoilage associations differing from those previously reported. In addition, improvement in identification methods, allow the detection and isolation of 'novel' bacterial groups, e.g., Carnobacterium spp. This review considers the genera Aerococcus, Brevibacterium, Brochothrix, Carnobacterium, Kurthia, Lactobacillus, Leuconostoc, Microbacterium, Micrococcus, Pediococcus and Propionibacterium. Strictly selective procedures, including incubation temperature and atmosphere, are not yet available for the genera Aerococcus, Brevibacterium, Microbacterium and Micrococcus, and only with some limitations for Kurthia and Propionibacterium. On the other hand, a causative role in food spoilage has not been established clearly for all those groups, some of which may be 'opportunistic' in their behaviour. The LAB groups Lactobacillus, Leuconostoc and Pediococcus ('LLP-Group') often share similar habitats and show similar physiological behaviour on a number of elective and selective media. Modifications to increase selectivity have been based mainly on de Man, Rogosa and Sharpe (MRS) or Rogosa agar, and include pH reduction, supplementation with chemical preservatives (e.g., sorbic acid and nitrate) and the use of reduced atmospheres or suboptimal incubation temperatures. Carnobacteria differ from other LAB in their non-aciduric nature, and selective plating procedures use high-pH media (pH 8-9) by which competitors (mainly lactobacilli) are eliminated.

Animals↗
PubMed1992

Relationship between the immune response of sheep and the population dynamics of bacteria isolated from fleecerot lesions.

In sheep wetted by rain, proliferation of bacteria in the skin-fleece microenvironment invariably discolours the fleece and causes a dermatitic condition known as fleecerot. The changes in population dynamics of fleece bacteria were analysed by carrying out skin washings at randomly selected sites on the back of sheep before, and at 48 h and 96 h after exposure to rain. Gram-positive rods belonging to Bacillus species (10(2)-10(4) cfu/cm2) predominated in dry fleece. Gram-positive cocci (e.g. Micrococcus and Staphylococcus species) as well as Gram-negative rods (pseudomonads) were also present but in lower abundance (less than 10(2) cfu/cm2). Fleece bacterial populations generally increased in numbers during the first 24-48 h of wetting. By 96 h however, skin washings showed a preponderance of Pseudomonas aeruginosa (10(4)-10(6) cfu/cm2) and to a lesser extent, pigmented Micrococcus species. Growth of fleece bacteria was associated with a characteristic green or yellow/orange staining of fleece. Fewer species of bacteria were isolated from sheep showing green staining while those animals with yellow/orange discolourations appeared to have a more mixed microflora composition. The predominance of P. aeruginosa in the wet fleece of sheep displaying either green or yellow/orange bacterial stain, was accompanied by a significant serological response against this species. Since skin bacteria have never been observed to penetrate cutaneously in skin sections biopsied from fleecerot sites, it must be concluded that the sheep skin is sensitized by continuous exposure to antigens that are associated with or released by P. aeruginosa.

Animals↗
PubMed2006

Microbiological characteristics of "androlla", a Spanish traditional pork sausage.

Counts of total aerobic mesophilic microflora, lactic acid bacteria, salt-tolerant microflora, Enterobacteriaceae, enterococci, moulds and yeasts, and staphylococci, and some physico-chemical parameters (total solids, NaCl and nitrate contents and pH and aw values) were determined in 20 units of "androlla", a traditional dry-fermented sausage made in the NW of Spain. In general, high counts of all the investigated microbial groups were observed, with average values of 8.99 +/- 0.46 log cfu/g for the total aerobic mesophilic microflora, 9.11 +/- 0.16 log cfu/g for the lactic acid bacteria, 6.87 +/- 0.68 log cfu/g for the salt-tolerant microflora, 2.80+/-1.85 log cfu/g for the Enterobacteriaceae, 3.25 +/- 1.86 log cfu/g for the enterococci, 4.30 +/- 1.73 log cfu/g for the moulds and yeasts, and 3.62 +/- 0.60 log cfu/g for the staphylococci. From MRS agar, SPC agar + 7.5% NaCl, VRBG agar, and KAA agar, 10 colonies were randomly taken from each androlla unit and from each culture medium. A total of 200 strains per culture medium were then identified using the classical methods. Among the isolates from MRS agar, Lactobacillus sakei predominated, followed by Lactobacillus curvatus, Lactobacillus alimentarius and Lactobacillus plantarum. Of the 200 isolates obtained from SPC agar + 7.5% NaCl, only 56 strains belonged to the Staphylococcaceae or Micrococcaceae families. Among the Staphylococcaceae, Staphylococcus xylosus was the main species, followed by Staph. epidermidis; Staph. equorum, Staph. capitis and Staph. saprophyticus were isolated in very low proportions. Among the Micrococcaceae, Micrococcus luteus predominated, followed by Micrococcus lylae, Kocuria varians and Kocuria kristinae. Of the 150 isolates obtained from VRBG agar, Hafnia alvei was the main species, followed by Serratia liquefaciens and Enterobacter amnigenus; six isolates were identified as Salmonella. Among the 190 isolates obtained from KAA agar, 122 were considered enterococci; 20 isolates were identified as Enterococcus faecium, one as Enterococcus faecalis and 101 as Enterococcus inter faecalis-faecium.

Animals↗
PubMed2005

Aerobic bacterial flora of the nasal cavity in Gulf of California sea lion (Zalophus californianus) pups.

Nasal swab samples from clinically healthy California sea lions pups (Zalophus californianus) from six different reproductive rookeries in the Gulf of California were collected to determine the type and frequency of the representative aerobic bacterial microflora of their nasal mucosa. A total of 114 samples were examined and 100 bacterial isolates were identified and typified by microbiological and biochemical standard tests. Fifty four isolates corresponded to Gram positive bacteria (54%) and 46 isolates to Gram negative bacteria (46%). Fifteen bacterial genera were identified, including Micrococcus, Arcanobacterium, Corynebacterium, Moraxella, Neisseria, Escherichia, Kurthia, Acinetobacter, Staphylococcus, Brevibacillus, Bacillus, Klebsiella, Stenotrophomonas, Pseudomonas and Aeromonas. The most frequently isolated genera were Moraxella (24%), Micrococcus (18%), and Corynebacterium (15%). These results show the presence in the nasal cavity of sea lions of several microorganisms. Although considered part of the normal microflora, they may also be opportunistic pathogens for their hosts and may act as a potential natural sentinel of environmental changes.

Animals↗
PubMed2003

Influence and persistence of phorate and carbofuran insecticides on microorganisms in rice field.

An experiment was conducted in microplots (4 m x 4 m) with two insecticides, phorate and carbofuran at rates of 1.5 and 1.0 kga.i.ha(-1) respectively, to investigate its effect on the population and distribution of bacteria, actinomycetes and fungi as well as the persistence of the insecticidal residues in rhizosphere soils of rice (Oryza sativa L., variety IR-50). Application of the insecticides stimulated the population of bacteria, actinomycetes and fungi in the rhizosphere soils, and the stimulation was more pronounced with phorate as compared to carbofuran. Both the insecticides did not have marked effect on the numbers of Streptomyces and Nocardia in the rhizosphere soils. However, the growth of Bacillus, Escherichia, Flavobacterium, Micromonospora, Penicillium, Aspergillus and Trichoderma with phorate and that of Bacillus, Corynebacterium, Flavobacterium, Aspergillus and Phytophthora with carbofuran were increased. On the other hand, the numbers of Staphylococcus, Micrococcus, Fusarium, Humicola and Rhizopus under phorate and Pseudomonas, Staphylococcus, Micrococcus, Klebsiella, Fusarium, Humicola and Rhizopus under carbofuran were inhibited. Both the insecticides persisted in the rhizosphere soil for a short period of time and the rate of dissipation of carbofuran was higher than that of phorate in the soil depicting the half-life (T1/2) 9.1 and 10.4 days, respectively.

Bacteria↗
PubMed1998

Histamine and tyramine degradation by food fermenting microorganisms.

Microorganisms suitable for food fermentation were examined with regard to their potential to degrade histamine and tyramine. Out of 64 lactic acid bacteria evaluated in this study, 27 degraded histamine and one tyramine, respectively, with low activity. Among 32 strains of Brevibacterium linens and coryneform bacteria, 21 exhibited histamine and tyramine oxidase activity. None of 20 strains of Staphylococcus carnosus tested degraded histamine or tyramine. One strain out of nine strains of Geotrichum candidum degraded tyramine slightly. Among 44 strains of Micrococcus sp. examined, 17 degraded either one or two biogenic amines. In this study Micrococcus varians (M. varians) LTH 1540 exhibited the highest tyramine oxidase activity of all strains tested and was therefore investigated in detail. The enzyme was found to be located in the cytoplasm and was not membrane bound. The reaction end product p-hydroxyphenyl acetic acid was detected by HPLC analysis. An activity staining for the amine oxidase in a native polyacrylamide gel based on the formation of H2O2 during amine oxidation was developed. Resting cells of the strain exhibited optimal tyramine oxidase activity at a pH of 7 at 37-40 degrees C. The enzyme in the cell free extract had a pH optimum between 7-8. The enzyme activity was decreased by NaCl, glucose and hydralazine. Phenylethylamine and tryptamine were oxidized at lower concentrations than tyramine. The potential for amine degradation was not found to be associated with that of formation of biogenic amines, as 23 microorganisms with the ability to metabolise biogenic amines exhibited no decarboxylase activity toward histidine, tyrosine, phenylalanine, lysine or ornithine.

Fermentation↗
PubMed2002

In vitro evaluation of AZD2563, a new oxazolidinone, tested against unusual gram-positive species.

The recently introduced oxazolidinone, linezolid, has a spectrum and potency directed against Gram-positive organisms, including antimicrobial-resistant isolates. The newest agent in this class, AZD2563 was tested against uncommonly isolated Gram-positive species to establish the breadth of its spectrum. By reference broth microdilution methods, 120 strains were tested (48 Corynebacterium spp., 10 species; 27 Listeria spp., 2 species; 11 Micrococcus spp., 2 species; 23 Bacillus spp., 3 species; 6 Stomatococcus mucilaginosus and one strain each of 5 other species) against AZD2563 and compared to eight other agents. The AZD2563/linezolid MIC(50;) % inhibited at < or =4 microg/mL were: for corynebacteria (0.25/0.25 microg/mL; 100/100%), Listeria spp. (2/2 microg/mL; 100/100%), Micrococcus spp. (1/1 microg/mL; 100/100%), Bacillus spp. (0.5/1 microg/mL; 100/100%), and S mucilaginosus (0.5/1 microg/mL; 100/100%). Using the MIC(90) values, AZD2563 was slightly more potent than linezolid (two-fold). Only four genus- species groups had AZD2563 MICs of strains at 2 microg/mL (Aerococcus, Leuconostoc, Listeria, Rhodococcus), all other isolates were inhibited by < or = 1 microg/mL. The AZD2563 potency and spectrum versus these rarer species was at least equal to linezolid, including some strains resistant to penicillins, macrolides-lincosamides, and fluoroquinolones.

Anti-Bacterial Agents↗
PubMed2002

Towards efficient crude oil degradation by a mixed bacterial consortium.

A laboratory study was undertaken to assess the optimal conditions for biodegradation of Bombay High (BH) crude oil. Among 130 oil degrading bacterial cultures isolated from oil contaminated soil samples, Micrococcus sp. GS2-22, Corynebacterium sp. GS5-66, Flavobacterium sp. DS5-73, Bacillus sp. DS6-86 and Pseudomonas sp. DS10-129 were selected for the study based on the efficiency of crude oil utilisation. A mixed bacterial consortium prepared using the above strains was also used. Individual bacterial cultures showed less growth and degradation than did the mixed bacterial consortium. At 1% crude oil concentration, the mixed bacterial consortium degraded a maximum of 78% of BH crude oil. This was followed by 66% by Pseudomonas sp. DS10-129, 59% by Bacillus sp. DS6-86, 49% by Micrococcus sp. GS2-22, 43% by Corynebacterium sp. GS5-66 and 41% by Flavobacterium sp. DS5-73. The percentage of degradation by the mixed bacterial consortium decreased from 78% to 52% as the concentration of crude oil was increased from 1% to 10%. Temperature of 30 degrees C and pH 7.5 were found to be optima for maximum biodegradation.

Bacteria↗
PubMed1997

Liposome-encapsulated ampicillin: physicochemical and antibacterial properties.

The objectives of this study were to develop high-performance liquid chromatography (HPLC) and antibacterial assays for ampicillin encapsulated in multilamellar liposomes (MLV) and investigate the physicochemical and antibacterial properties of ampicillin-liposome systems. The major findings were fourfold. First, ammonium acetate (0.575%) in methanol:water (450:550; v/v), adjusted to pH 7.2, was suitable as the mobile phase for the HPLC determinations of ampicillin in both aqueous and liposomal systems. This mobile phase also provided (alone or with additional methanol) complete dissolution of liposomal assay samples in a precolumn treatment that made all of the encapsulated drug available for chromatography. Multiple samples were assayed without any technical limitations. Second, the growth-inhibition antibacterial assay developed, which used the USP test organism Micrococcus Luteus and paper disks, was quantitative for both free and liposome-encapsulated ampicillin. Third, the physicochemical properties of encapsulated ampicillin include encapsulation efficiencies of 10 to 50% for liposome concentrations in the range 10-200 mM (lipid), and a single rate constant to sufficiently and quantitatively describe the diffusion of encapsulated ampicillin, with half-lives in the range of 40 h. Fourth, the biological properties include the first direct evidence that encapsulated ampicillin retains full biological activity; that is, liposome-encapsulated ampicillin was active against extracellular bacterial colonies of Micrococcus luteus. Furthermore, encapsulation enhanced ampicillin stability. For example, free ampicillin in an aqueous solution that was stored for 5 weeks at 4 degrees C lost 50% of its initial activity, whereas liposome-encapsulated ampicillin (freed from unencapsulated drug) stored under the same conditions lost only 17% of its initial activity. The findings of this study, provide strong support for ampicillin-liposome formulations as valid dosage forms for this drug that are worthy of further experimental evaluations.

Ampicillin↗
PubMed1984

Reversible inhibition of bacterial growth after specific inhibition of spermidine synthase by dicyclohexylamine.

The effect of dicyclohexylamine on seven freshly isolated bacterial strains of mastitis pathogens was studied. Streptococcus uberis was the most sensitive strain investigated, since 5 mM-dicyclohexylamine totally arrested its growth and 1.25 mM of the drug caused 60% growth inhibition. The Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa strains were also sensitive to the drug, but less so than Strep. uberis, since 5 mM drug caused only partial inhibition of growth. Micrococcus sp. and Klebsiella sp. grew in the presence of 10.0 mM-dicyclohexylamine, and, finally the growth of Streptococcus agalactiae was not at all affected by dicyclohexylamine. These different sensitivities towards dicyclohexylamine in vivo were paralleled by different sensitivities of the bacteria's spermidine synthase to the drug in vitro, and also by the ability of the drug to lower spermidine concentration in bacterial cells. Spermidine synthase from sensitive bacteria was inhibited by more than 90% by 50 microM-dicyclohexylamine in vitro, and the concentration of spermidine was decreased in E. coli and Ps. aeruginosa by 70% and in Strep. uberis by 95%, whereas in Strep. agalactiae 5 mM-dicyclohexylamine did not affect the concentration of spermidine at all. Dicyclohexylamine treatment led to the accumulation of putrescine in Strep. uberis. Spermidine synthesis catalysed by the extracts of Micrococcus sp. required 500 microM-dicyclohexylamine for 90% inhibition, and Strep. agalactiae contained a spermidine synthase that was still active at 1000 microM-dicyclohexylamine, The observed inhibition of growth was totally reversed by adding 50 microM-spermidine (final concentration) to the medium. Putrescine reversed the inhibition only when bacteria had a spermidine synthase activity insensitive to dicyclohexylamine. Spermine did not overcome the inhibition of growth caused by dicyclohexylamine, probably because it was not taken up by the bacterial cells used in this study. The inhibition of the growth by dicyclohexylamine (even in the case of Strep. uberis) was reversible in the sense that addition of 50 microM-spermidine 18 h after dicyclohexylamine still restored the growth rate of untreated controls.

Bacteria↗
PubMed1997

Antimicrobial activity of food-related Penicillium sp. against pathogenic bacteria in laboratory media and a cheese model system.

Food-related Penicillium species (n = 34) and Geotrichum candidum (n = 11) grown on Czapek Dox and brie agar were tested for their ability to suppress growth of pathogenic bacteria. Ten out of 13 P. camemberti showed antagonistic activity while the other species did not interact significantly with the bacterial growth. The order of inhibition was: Gram-negative bacteria and Bacillus cereus > Listeria monocytogenes, Lactococcus sp. > Micrococcus sp. whereas Lactobacillus sp., Staphylococcus aureus and some Micrococcus sp. were unaffected. When Salmonella typhimurium was inoculated together with P. camemberti P25 in brie agar, bacterial growth was inhibited during the first 6 d of incubation whereafter growth started. The inhibition of L. monocytogenes was similar but less pronounced. The antimicrobial activity produced by P. camemberti P25 and L84 was enhanced with increasing amount of sucrose in the medium. The activity was increased at low pH and destroyed at pH above 8. It was detectable at 15 degrees C but not at 37 degrees C indicating that volatile metabolites might be involved. No significant accumulation of organic acids and no secondary metabolites such as mycotoxins were detected. HSGC-MS analysis indicated that acetaldehyde, benzaldehyde, 3-methylbutanal and 1-octen-3-ol were produced by P. camemberti during the period when inhibitory activity was observed. Pure acetaldehyde and benzaldehyde were shown to be inhibitory to L. monocytogenes and Salm. typhimurium when grown at 15 degrees C and pH 5.5 and 7.0.

Acetaldehyde↗
PubMed1999

Dust-borne bacteria in animal sheds, schools and children's day care centres.

A total of 316 bacterial strains, including psychrophiles, mesophiles and thermophiles, were isolated and identified from indoor dusts in schools, children's day care centres and animal sheds. Several species which had not previously been reported from indoor environments were found: Sphingomonas, Brevibacterium, Nocardiopsis, Deinococcus and Rhodococcus/Gordona. A new psychrophilic actinomycete genus was also found in animal sheds, representing a new undescribed peptidoglycan type and an unusual whole-cell fatty acid composition. The indoor dusts of animal sheds contained mainly the Gram-negative genera Pseudomonas, Pantoea, Flavobacterium and Xanthomonas early in the indoor feeding season, but changed to a composition dominated by Bacillus, Micrococcus and mesophilic and thermophilic actinomycetes towards the end of the season. The dust contained, and air-borne bacterial flora in schools and day care centres were dominated by, Gram-positive bacilli and actinomycetes, notably Bacillus cereus, Brevibacillus brevis, B. licheniformis, B. subtilis and species of Arthrobacter, Corynebacterium, Rhodococcus/Gordona, Nocardiopsis sp., Deinococcus, Staphylococcus and Micrococcus. Indoor air and dust contained Klebsiella oxytoca, Acinetobacter calcoaceticus, Ac. lwoffi, Bacillus cereus and Nocardiopsis dassonvillei with the status of hazard group II. Indoor dusts of animal sheds contained eight different 3-hydroxy fatty acids, the 2-hydroxy fatty acid 14:0 and two 10-methyl fatty acids, whereas in dusts from schools and day care centres, these were below the detection level (< 3.5 ng mg-1). The 3-and 2-hydroxy fatty acids could be assigned to one or more of the dust-contained cultivable strains, but 10-methyl C16:0 was not present in any of the strains isolated. The dusts from schools and children's day care centres contained 0.2-0.3 ng of endotoxin mg-1 and 0.5-1.4 ng of beta-D-glucan mg-1, whereas the dusts from animal sheds contained more 0.3-41 ng mg-1 and 8-35 ng mg-1, respectively.

Air Microbiology↗
PubMed2003

Bacterial species in biofilm cultivated from the end of the Seoul water distribution system.

AIMS: To investigate changes in the bacterial population and the safety of the biofilm at the end of the drinking water distribution system in Seoul (Korea), selective media and bacterial community analyses were applied to a semi-pilot galvanized iron pipe (GIP) model. METHODS AND RESULTS: No total coliforms or faecal streptococci were detected on m-Endo or m-Enterococcus agar. No Salmonella spp. and Shigella spp. were detected on bismuth sulphite agar or Hektoen enteric agar, respectively. The latter two media detected coliforms, where m-Endo was negative. Biofilm formation started within 1 week (ca 104 CFU cm(-2)) and exceeded 105 CFU cm(-2) within 6 weeks. Although the fatty acid methyl ester analysis revealed dynamic changes in bacterial composition, Micrococcus, Bacillus, and Pseudomonas spp. were persistent members of the biofilm community. Micrococcus spp. was detected most frequently and in high numbers. CONCLUSIONS: Coliforms and Enterococcus species can be recovered from biofilms in water distribution systems. SIGNIFICANCE AND IMPACT OF THE STUDY: This study illustrates the role of biofilms in the chronic deterioration of the water-distribution system in Seoul (Korea).

Bacteriological Techniques↗
PubMed1999

Clinical application of a homogeneous colorimetric assay for tear lysozyme.

PURPOSE: Tear lysozyme and tear lactoferrin are enzymes synthesized by the lacrimal gland. Their concentration in human tears reflects tear gland function. Tear gland dysfunction can lead to ocular surface disease. We developed a colorimetric lysozyme assay. The objective of this study was to determine the diagnostic power and the clinical application of this assay that allows rapid and precise quantification of tear lysozyme. METHODS: Tear specimens of 120 eyes (30 Sjögren's patients and 30 controls) were collected using standardized filter paper discs. Tear lysozyme concentration was determined using p-nitrophenyl penta-N-acetyl-beta-chitopentaoside as substrate in the colorimetric assay. The results were compared to clinical findings and to two commonly used tests, the Micrococcus agar diffusion assay for tear lysozyme and the tear lactoferrin immunodiffusion assay. RESULTS: The colorimetric assay showed a good dose-response relationship. The use of the assay as a method of diagnosing aqueous tear deficiency, using the clinical findings and the medical history as gold standard, demonstrated 85% sensitivity and 92% specificity. The results of the colorimetric assay when compared with the Micrococcus agar diffusion assay showed a linear relationship of r=0.77; when compared with the lactoferrin immunoassay r=0.73. CONCLUSIONS: The colorimetric assay is simple to perform and does not require sophisticated laboratory equipment and personnel. Results can be precisely quantified within one hour after tear collection. The diagnostic power of the test is comparable to previously reported assays for lysozyme and lactoferrin and will be useful in the diagnosis of ocular surface disease.

Adolescent↗
PubMed1958

Bactericidal action of histone.

The arginine-rich fraction of calf thymus histone (histone B) exerts bactericidal activity on various coliform bacilli and micrococci under certain conditions in vitro. Final concentrations of less than 1 microg. histone per ml. kill susceptible microbes without detectable morphological alteration or lysis. Among the microorganisms highly susceptible to histone are Escherichia, Salmonella, Shigella, Pseudomonas, Klebsiella, and Micrococcus pyogenes var. albus. Less susceptible or completely resistant are Proteus, Serratia, Micrococcus pyogenes var. aureus, and various types of hemolytic streptococci. Coliforms grown on solid media are much more resistant to the lethal effect of histone than are those cultured in liquid media. This difference is apparently related to the physiological state of the bacteria; agar grown microorganisms washed with water remain resistant to histone, whereas incubation in broth rapidly renders them more susceptible. Histone is adsorbed onto heat-killed E. coli K-12 under conditions suitable for lethal action on this organism. The bactericidal activity of histone is but little affected by pH of the test system, but ionic strength of the medium exerts a marked influence, the lethal action being reduced or blocked as the salt concentration reaches levels higher than that of 0.15-0.2 M NaCl. Relatively high concentrations of rabbit serum or of bovine plasma albumin reduce the bactericidal activity of histone in a medium at pH 7; these serum preparations are, however, essentially without effect in the test system at pH 5.6. The bactericidal effect of histone is antagonized by addition to the medium of small amounts of certain basic substances (protamine, spermine), or of various acid polysaccharides (heparin, nucleic acid, bacterial lipopolysaccharides). The rate of killing of E. coli K-12 by histone increases as the temperature and the concentration of histone are raised. Within the limits studied, this rate also appears to be directly proportional to the concentration of bacteria in the system.

Animals↗