Biomedical subjects

M Vyletĕlová

Publications and source records attributed to M Vyletĕlová.

4 recordsLinked to original sources

PubMed1997

[Testing of culture media for detection of Staphylococcus aureus in bulk milk samples].

Three common selective agar culture media were tested with respect to detection of Staphylococcus aureus: Baird-Parker agar (BP), Mannitol-Salt-Phenol agar (MAN) and Vogel-Johnson agar (VJ). All media were cultivated at temperatures of 37 degrees C and 43 degrees C. Three groups of samples were used for investigations: 1, pure cultures of 52 collection strains of S. aureus received from the Czech Microorganism Collection (Tab. I), 2. pure cultures of 75 laboratory strains of S. aureus from samples of cow raw milk and 3,223 bulk samples of cow raw milk. Medium recovery and frequency of medium failure were evaluated, as well as subjective evaluation of medium selectivity and count feasibility was done. The best results of recovery and failure frequency were observed in BP/37 degrees C for all three groups; except the collection strains, in which a distinction from BP/43 degrees C was only moderately significant (P = 0.1; Tab. II), statistically significantly better results of recovery against the other media were determined for BP/37 degrees C in all cases (Tabs. III, VI, IX). No other medium with better results was found out for any other group of samples as regards failure frequency (Tabs. IV, VII, X). Recoveries of BP/43 degrees C ranged from 78 to 95% in comparison with BP/37 degrees C (Figs. 1-3). A group of three media (VJP/37 degrees C, MAN/37 degrees C, MAN/43 degrees C) showed similar results in all groups of samples, statistically significant differences were rare (Tabs. III, VI, IX); recoveries ranged from 55-85% in comparison with BP/37 degrees C (Figs. 1-3). The cultivation on VJ/43 degrees C turned out absolutely inappropriate. Subjective evaluation (Tab. IX) revealed BP/43 degrees C as the best medium, particularly due to the clearly expressed diagnostic traits and high selectivity for accompanying microflora. Enterococci were the most important accompanying microflora in cases of BP/37 degrees C, BP/43 degrees C and VJ/37 degrees C; while in MAN/37 degrees C and MAN/43 degrees C the microflora making the count difficult consisted of representatives of the genera Staphylococcus, Micrococcus and Bacillus. Determinations on different media (except VJ/43 degrees C) well correlated with each other in general (Tabs. V, VIII, XI), the differences in correlations between the pairs of media were not commonly statistically significant.

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PubMed1997

[Validation of TKT medium for detection of Streptococcus agalactiae in bulk milk samples].

A selective medium for quantitative determination of Streptococcus agalactiae in bulk milk samples was tested. Among the medium bases, Edwards medium (EW) supplemented with 6 to 9% (v/v) of carefully washed sheep erythrocytes was proved to be best (Tab. V). The production of sphingomyelinasis C (BHE, Tab. II) or D (COREX, Tab. I) as a supplement supporting the formation of specific hemolytic zones in the medium, was tested in four strains of Staphylococcus aureus and seven strains of Corynebacterium pseudotuberculosis. Submersion aerated cultivation was used for enzyme production; optimum cultivation time is about 100 hours (Figs. 1, 2). To determine the activity of the enzymes produced a screening method was developed applying hemolytic interactions with CAMP factor of Str. agalactiae. Method sensitivity and reproducibility are sufficiently high for the purposes of observation (Tab. III). The produced enzymes did not show any changes in their activity over the whole period of storage under all conditions of storage (32 days/7 degrees C, 48 weeks/-18 degrees C, lyophilizate 48 weeks/20 degrees C). Sphingomyelinasis C is more resistant to heat denaturation, not losing its activity even after being warmed to 85 degrees C for 5 min; sphingomyelinasis D is sensitive to temperatures higher than 50 degrees C (Fig. 3). COREX was selected (sphingomyelinasis D), produced by the strain CNTCC 18/62 of C. pseudotuberculosis. The enzyme was applied either in raw filtrate of the medium (sterilization by repeated membrane filtration) or in prepurified form obtained by cold acetone precipitation, providing the same results. The medium is highly specific and likely enough selective for Str. agalactiae, unlike BHE it does not provide any positive results with UBERIS-factor+strains of Str. uberis (Tab. V). Optimum cultivation time is 18 hours; prolongation of cultivation for more than 24 hours brings about the risk of falsely positive readings (Tab. VI) in the strains of accompanying microflora (Morganella morganii ssp. morganii, delta-hemolytic staphylococci).

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PubMed1997

[A method for estimating the prevalence of mammary Staphylococcus aureus and Streptococcus agalactiae infections in herds based on an examination of bulk milk samples].

Parallel quantitative determination executed in 92 herds at 107 sampling dates was focused on the counts of major pathogens (Staphylococcus aureus, Streptococcus agalactiae) in bulk milk samples and on the prevalence of the above pathogens in a herd by examination of individual milk samples. The counts of main pathogens were also determined in terms of quantity in rinsing water before milking and in bulk samples in 5 herds with pipeline milking. Tab. I shows the qualitative analysis of the relation. Sensitivity of the method is satisfactory for the pathogens observed (95% and 91%, resp.), but method is less specific for Staph. aureus (67% against 92% Str. agalactiae). Figs. 1 and 2 show coordinate graphs of the results obtained while Figs. 3 and 4 document the distribution of frequency of the particular values in data sets. The values do not exhibit normal distribution (P < 0.01). Spearman's coefficient of rank correlation of bulk milk and individual examinations amounted to 0.823 and 0.900 for Staph. aureus and Str. agalactiae, respectively. Four mathematical models were tested in the course of quantitative analysis, describing the relation between bulk milk examination and individual examination: (1) linear regression, (2) linear regression with fixed starting point, (3) logarithmic regression and (4) irrational function. A model based on the equation of irrational function (4) was found to be best: y = a + bx + c square root of x + k +/- a1 + i(t)c1 square root of x + k1. Tab. II shows the parameters of the equation for examined microorganisms. Correlation coefficients for the above equation are r = 0.733 and r = 0.842 for Staph. aureus and Str. agalactiae, respectively. Prediction curves (Figs. 5 to 8) and confidence regions of prediction curves were also determined for the best model, and a prediction table was constructed (Tab. III). It was confirmed that the milking machines were not a significant source of direct contamination of bulk milk samples with the examined pathogens (Tab. V).

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PubMed1995

[Staphylococcus aureus in bulk milk samples].

In the years 1993-1994 the occurrence of Staphylococcus aureus was investigated in bulk milk samples in the area where a Baby Food Factory at Zábreh in Moravia is located, and in Bruntál, Zlín and Policka districts. Evaluation of the results was based on ECC Directive 92/46, while the dynamics of S. aureus presence was followed for the whole period of observation as well as in the particular seasons. A total of 4,485 samples was processed. Out of these, 50.7% contained less than 100 CFU/ml of S. aureus, 41.4% contained 100-500 CFU/ml, 6.73% 500-2,000 CFU/ml and 1.14% contained more than 2,000 CFU/ml (Fig. 1). The samples were divided into three categories: private new-established farms, cooperative and State-owned enterprises in the area of the Zábĕh Factory and others (Zlín, Bruntál and Policka districts). There were highly significant differences in the content of staphylococci (P = 0.01%) between the three categories of samples. Ninety-eight percent of samples from private farms, 96% samples from the Zábreh Factory area and 85% of the other samples comply with the regulation EEC 92/64 (Tab. I) for raw cow's milk for the manufacture of products "made with raw milk" whose manufacturing process does not involve any heat treatment (Fig. 2). The occurrence of S. aureus in the Zábreh Factory area shows an expressive seasonal dynamics (P = 0.005%) with maximum values in winter months (December-March) and minimum values in summer months (July-October)-Fig. 3. The same relationship can be seen on more extensive data files for the particular producers (Fig. 4).(ABSTRACT TRUNCATED AT 250 WORDS)

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