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Biomedical subjects

T I Afanas'eva

Publications and source records attributed to T I Afanas'eva.

At least 19 recordsLinked to original sources
PubMed1981

[Characteristics of the effect of egg lysozyme on micrococci and staphylococci].

The nature of the optical density of suspensions of Staph. aureus and M. luteus cells at various concentrations of chicken egg albumin lysozyme and two products of its chemical transformation was studied comparatively. The experiments were performed in 1/15 M Na-phosphate buffer at pH 6.2 and a temperature of 20-22 degrees C. It was shown that the decrease in the optical density of the suspensions observed at relatively low concentrations of lysozyme, i.e. 0.032-0.064 mg/ml, was due to lysis of both microbial species. The increase in the optical density of the suspensions at higher (0.5-2.0 mg/ml) concentrations of lysozyme was connected with formation of insoluble aggregates of an electrostatic character. Lysozyme in such aggregates is the positively charged component and the microbial cell material is the negatively charged component. When M. luteus strains are sensitive to lysozyme, the aggregates are formed from the cell fragments or lysis acid products. When Staph, aureus strains have higher resistance levels, the aggregates are formed from both the lysis products and the intact live cells which is of special interest.

Acetylation↗
PubMed1980

[Biological characteristics of coagulase-negative staphylococci isolated from conjunctivitis].

The biological properties of 101 strains of coagulase-negative staphylococci isolated from conjunctival secretions of conjunctivitis patients, as well as from healthy persons were studied. More than a half of these strains (66%) were identified as Staph. epidermidis. 18% of the strains differed from this species only by the absence of phosphatase activity. The existence of the phosphatase-negative variants of Staph. epidermidis was inferred from this fact. About 1/3 of the cultures could not be identified in accordance with the scheme of the International Subcommittee on the Taxonomy of Staphylococci and Micrococci. The biological activity of the cultures isolated from conjunctivitis patients did not differ from that of the cultures isolated from healthy persons. The frequent occurrence of hemolytic activity in the strains isolated from both conjunctivitis patients and healthy persons was noted (88% and 83%, respectively). The conclusion on the variegated character and lability of the phenotypic characteristics of staphylococci has been made.

Coagulase↗
PubMed1979

[Inhibiting action of egg albumin on the growth of coagulase-negative species of staphylococci].

The effect of various concentrations of native egg albumin on growth of three staphyloccal species was studied. It was found that addition of 25 per cent of the albumin to the medium prepared from dry nutrient agar inhibited growth of Staph. epidermidis and Staph. saprophyticus, had no effect on growth of Staph. aureus and promoted formation of a pigment by it. A mechanism of the albumin inhibitory effect is suggested. It is proposed that the albumin medium be used for differentiation of Staph. aureus and the coagulase-negative species of staphylococci.

Coagulase↗
PubMed1979

[Significance of determining novobiocin sensitivity in the taxonomy of staphylococci].

Novobiocin sensitivity of 96 strains belonging to various staphylococcal species was studied. It was noted that Staph. saprophyticus significantly differed from Staph. aureus and Staph. epidermidis with respect to the above antibiotic. The MIC up to 2 micrograms/ml and the growth inhibition zones of 26--35 mm in diameter were characteristic of Staph. aureau and Staph. epidermidis, while the respective figures for most of the strains of Staph. saprophyticus were 32--64 micrograms/ml and 12--17 mm. However, 28 percent of the strains of Staph. saprophyticus did not differ with respect to their movobiocin sensitivity from the other 2 species. It is concluded that the "novobiocin test" may be used for differentiation of staphylococci, within the genera. At the same time it was shown that the method of the paper sensitivity discs compares very favourably with the method of serial dilutions in agar not only because of its simplicity and convenience of manipulation with single strains, but also of the possibility of identifying the population heterogenicity with respect to novobiocin sensitivity.

Dose-Response Relationship, Drug↗
PubMed1979

[Action of egg lysozyme on representatives of the family Micrococcaceae. The action on staphylococci].

The results of the study on the effect of various concentrations of lysozyme on staphylococci of three species, i.e. Staphylococcus aureus, Staphylococcus epidermidis and Staphylococcus saprophyticus are presented. The study was performed with the use of the turbidimetric method. It was found that all the staphylococci had a common tendency for changing the optic density (OD) of the suspensions under the effect of lysozyme which was different from that in Micrococcus luteus. However, the dynamics of decreasing the OD in Staph. saprophyticus was characterized by some properties which provided a supposition that the structures of the cell walls in Staph. aureus and Staph. epidermidis were close, while the cell walls in Staph. saprophyticus had some unknown characteristics.

Dose-Response Relationship, Drug↗
PubMed1978

[Action of egg lysozyme on representatives of the family Micrococcaceae. Its action on Micrococcus].

The results of the study of the effect of various concentrations of egg lysozyme on M. luteus and M. varians using 2 methods, i.e. serial dilutions in agar and turbidimetric are presented. It was found that the MIC of lysozyme for M. luteus ranged within wide limits, from less than 0.0003 to 1 mg/ml. M. varians was stable to lysozyme. The MIC for all the strains was 8 mg/ml. The turbidimetric method provided determination of general regularities in changes of the optical density in all the strains of M. luteus under the effect of various concentrations of lysozyme. On the basis of these data it was possible to consider the method as the most deep means for determining the intraspecies similarities in the surface structures of Micrococcus as compared to the method of serial dilutions in agar. The dynamics of the changes in the optical density of the M. luteus suspension markedly differed from that of M. varians.

Animals↗
PubMed1978

[Drop method of determining micrococcal and staphylococcal sensitivity to egg lysozyme].

Two methods for determination of staphylococcal and micrococcal sensitivity to lysozyme, i.e. the method of serial dilutions in agar and the drop method developed by the authors were compared. The drop method is a modification of the procedure described by Kloos et al. Close correlation between these two methods (r = 0.97 +/- 0.018) was found. The regression curve providing determination of the lysozyme MIC with the drop method was plotted. The drop method is more simple and economical as compared to the method of serial dilutions in agar. It has an advantage in testing sensitivity of single strains.

Dose-Response Relationship, Drug↗
PubMed1978

[Importance of carbohydrate tests for interspecies differentiation of staphylococci].

The authors present the results of interspecies identification of coagulaso-negative staphylococci isolated from different sources. Modification of the method of aerobic carbohydrate and alcohols fermentation of hard media is described. Use of the latest recommendations of the International Subcommittee on taxonomy of staphylocossi and micrococci permitted to identify the greater part of 120 strains studied as Staph. epidermidis and Staph. saprophyticus; however, 1/3 of the cultures differed from these species ("intermediate" strains). Galactose and mannose fermentation was characteristic of Staph. epidermidis, and the absence of fermentation of these carbohydrates--of Staph. saprophyticus. The differences in the fermentation of mannite and tregalose, on the one hand, and on mannose and galactose--on the other, were characteristic of 57% of the "intermediate" strains. The data obtained permitted to draw a conclusion on nonhomogeneity of the group of coagulase-negative staphylococci by their reference to different carbohydrates and alcohols, and on a possibility of existence of not only of different species of these staphylococci, but also of their biochemical variants.

Aerobiosis↗
PubMed1976

[Comparative antibiotic sensitivity of different species of staphylococci isolated from humans].

A total of 206 strains of various staphylococcal species isolated from various sources were studied with respect to their sensitivity to 18 antibiotics. The number of strains poly-resistant to the antibiotics was almost the same among Staph. aureus and Staph. epidermidis, i. e. 54.8 and 51.3 per cent respectively. The coagulase-negative and mannitol-negative variants of Staph. aureus and Staph. epidermidis possessing high biological activity (10-14 properties) were resistant to more antibiotics as compared to the low active strains.

Anti-Bacterial Agents↗
PubMed1976

[Role of the lysozyme-like enzyme of staphylococci in their pathogenicity].

Observations of the authors of the present work permit to put forward the following suppositions on the biological significance of the lysozyme sign included into the number of sign-of the staphylococcus pathogenicity: 1) the action of the lysozyme-like enzyme (LLE) as a facs for increasing the permeability of the cell wall and thus promoting the exit of the "pathogenicity enzymes"; 2) its participation in the growth and division of staphylococci, pointing to the differences in the rate of the growth of the cultures forming and nonforming the LLE; 3) participation of the LLE in the microbial antagonism processes--crude LLE (in the form of lipoproteid complex) stipulated the antimicrobial effect against a number of nonpathogenic microbes. None of these hypotheses can be accepted without further investigations, particularly with the purified enzyme.

Animals↗
PubMed1976

[Pigment formation and other biological properties of staphylococci].

A comparison was made of the pigment-forming capacity and the enzymatic activity, growth rate, virulence and sensitivity to antibiotics and egg lysozyme in 397 pigment, 203 pigment-free strains of staphylococci and 24 pigment-free Staph aureus mutants. Pigment formation did not always correlate with the general biological activity of the cultures, the rate of their growth and the sensitivity to antibiotics and lysozyme. Pigment-free staphylococcus mutants retained the principal properties of the initial strains (including the virulence and sensitivity to antibiotics and egg lysozyme) more frequently. It is supposed that the marker determining the pigment formation in staphylococci was not connected with the markers determining the most significant pathogenicity properties and also antibiotic resistance.

Drug Resistance, Microbial↗
PubMed1975

[Production of a lysozyme-like enzyme by various representatives of the genus Staphylococcus].

On the basis of studying 855 strains of various staphylococci it was shown that production of a lysozyme-like enzyme (LLE) failed to serve as a characteristic sign for all the representatives of Staphylococcus genus. It was mostly observed in S. aureus (in 85% of the strains). In nonpathogenic strains of S. epidermidis LLE could not be revealed either by the dish or by affine chromatography on chitin; among S. epidermidis, isolated from the patients there were cultures which did or did not form the LLE. Cultures occupying an intermediate position (coagulase-negative or mannite-negative) formed the LLE in 66.9% of cases. It was shown that the virulence and the general biological activity of the lysozyme-positive intermediate strains were higher than in the lysozyme-negative ones.

Animals↗
PubMed1975

[Antibacterial activity of a lysozyme-like enzyme from staphylococci].

A lysozyme-like enzyme isolated from the culture broth of Staph. aureus 712 presented in its native state a lipoproteid complex. The lytic and antibacterial spectrum of the enzyme was similar to that of the egg albumin enzyme. However, the lipoproteid complex was somewhat superior to the egg albumin complex in its activity against Micrococcus lysodeikticus, a number of gramnegative bacteria and staphylococci. Out of the organisms studied Microccus lysodeikticus, Sarcina and Bac. subtilis proved to be most sensitive to the both enzymes. Comparison of the amount of the enzyme formed in the culture medium with its minimum inhibitory concentration with respect to most of the microbes tested provided a supposition that the lipoproteid enzyme did not play a significant role in the process of the microbial antagonism.

Acetylglucosaminidase↗