[Determination of beta-lactamase production in strains of Staphylococcus aureus isolated from the milk of cows]. / Zjistování produkce betalaktamázy u kmenu Staphylococcus aureus izolovaných z mléka krav.

Determination of sensitivity to penicillin G by a standard disk assay diffusion method was compared with a iodometric method of test papers to determine beta-lactamase production after Jorgensen in Staphylococcus aureus strains isolated from cow's milk from different farms. Out of 179 test strains, 32 strains 17.8%) were found to be well sensitive in the diffusion test; eight of these strains (25.0%) were demonstrated to produce beta-lactamase. 54 strains (30.2%) were sensitive. 27 strains (50%) of this group produced beta-lactamase. 93 strains (51.9%) were resistant to penicillin G in the diffusion test. 86 strains (92.5%) were found to produce beta-lactamase and seven strains were negative in this test. Using the diffusion test of sensitivity in these cultures, 86 strains were sensitive (48.1%) and 93 strains were resistant (51.9%). Beta-lactamase was produced by 121 strains (67.6%) and no beta-lactamase production was recorded in 58 strains (32.4%). Differences in the results of both tests were manifest mainly in the set of strains qualified as sensitive (inhibition zone diameter 24 to 16 mm) and well sensitive (inhibition zone diameter larger than 25 mm). The results indicate that the currently performed diffusion test of sensitivity to penicillin G should be accompanied by an assay of beta-lactamase production. The iodometric method of test papers is simple, rapid and cheap and can be made in any bacteriological laboratory. The high resistance of Staphylococcus aureus strains to penicillin G documents that this antibiotic is little efficient in the treatment of mastitis of this etiology in the given region.

[Bacteriological findings in samples of milk from cows studied for the causative agent of mastitis]. / Bakteriologické nálezy ze vzorku mléka krav vysetrených na puvodce mastitid.

Milk samples (483,413 on the whole), collected from 237,026 cows, were investigated in the State Veterinary Institute at Pardubice in the period from 1983 to 1987. In the individual years, the proportion of cows whose milk contained the mastitis-inducing bacteria ranged from 18.0 to 24.8%, the average being 21.0%. Streptococcus agalactiae was identified most frequently as the causative agent of mastitis in the examined cows (6.4%); then followed Streptococcus dysgalactiae (3.7%), Staphylococcus aureus (3.4%), and Streptococcus uberis (1.9%). The presence of the beta-haemolytic streptococci with group antigens C, G and L was demonstrated in the milk of 720 cows (i. e. 0.3%) and the remaining species of streptococci were identified in 1.0% of the cows. Coliform microorganisms were detected in 0.6% and Actinomyces pyogenes in 0.1% of the cows. The remaining bacterial species were isolated from the milk of 3.6% of the cows. Coaglucase-negative staphylococci dominated in this group. Over the five years of study, the occurrence of Streptococcus agalactiae in the examined stocks declined from 10.8 to 3.5% but the occurrence of other streptococci and staphylococci increased.

[Verification of peroral vaccination of pigs against enteropathogenic strains of Escherichia coli]. / Ovérení perorální vakcinace prasnic proti enteropatogenním kmenum Escherichia coli.

In a large herd of pigs where the parenteral immunisation of pregnant sows by polyvalent vaccine against enteral coliinfections of new-born piglets was performed successfully for several years, an increased occurrence of diseases and mortality of sucking piglets was observed. After screening tests in the herd, six strains of E. coli, differing from the strains contained in the commercial vaccine, were isolated. The obtained strains were employed for preparation of peroral vaccine for sows by means of the modified method after Kohler. In two cycles of sows (48 animals in experimental group and 60 animals in control group), this method was compared with the effectiveness of the commonly used commercial polyvalent parenteral vaccine against enteral E. coli infections of new-born piglets (manufactured by Bioveta, Ivanovice in Haná). In experimental sow groups vaccinated perorally by the new vaccine, the number of live-born piglets increased by 0.475 piglet per litter, the number of reared piglets up to the age of 28 days by 0.904 piglet per litter and the mortality till the age of 28 days decreased by 6.1% as compared with the control vaccinated by commercial vaccine. The results were not statistically significant. The advantages and disadvantages of both vaccination methods are discussed.