[Pseudomonas aeruginosa in raw and pasteurized milk]. / Pseudomonas aeruginosa v syrovém a pasterovaném mléce.

Eighteen strains of Pseudomonas aeruginosa, i.e. 8.87%, were isolated during a year from 203 samples of raw milk. Two Pseudomonas aeruginosa strains, i.e. 4%, were isolated from 50 samples of pasteurized milk. The strains were isolated using propagation techniques in meat-peptone broth with malachite green and on selective media--on centrimide agar (CEM) and on Pseudomonas F agar. All the isolated strains produced protease, whereas lipase was produced by only five strains. The strains were devitalized when exposed to pasteurization temperatures (72 degrees C) for 20 seconds. At cold store temperatures (4 degrees C), Pseudomonas aeruginosa strain cells propagated on average by two orders, inhibitory effects of low temperatures were recorded only with one strain. Inhibitory effects of milk cultures (cream, yogurt) on Pseudomonas aeruginosa were observed; their effects were more clear-cut at the temperature of 4 degrees C. The strains were markedly susceptible to gentamycin.

[Use of a selective sulfite-reducing medium for the isolation of Clostridium perfringens]. / Pouzití selektivního sulfitredukcního média pro izolaci Clostridium perfringens.

The effect of sulphite-reduction in 33 sample bacterial strains was tested. With regard to the capacity of reducing sulphite in modified sulphite-reduction media in a wide scale of bacterial strains the possibility of an application of selective media with an addition of various concentrations of antibiotic solutions was checked. A concentration of 750 microgram of D-cycloserine per 1 ml of the sulphite-reduction medium appeared to be the most advantageous for the isolation and detection of sulphite-reductive clostridia, above all of Clostridium perfringens. This concentration ensured also a sufficient inhibition of undesirable bacteria without any affection of the growth and capacity of Clostridium perfringens to reduce sulphite in the applied medium.

[Detection of inhibitory substances in milk using the modified reduction micromethod]. / Detekce inhibicních látek v mléce modifikovanou reduckcní mikrometodou.

In order to rationalize work and to reduce the consumption of laboratory glassware a reduction micromethod with the bacterial stain Streptococcus thermophilus has been modified; the method is used to detect inhibitory substances in genuine, pausteurized and dried milk, and it is performed on a serological plate made from organic glass. The method is sensitive to most antibiotics used in the veterinary clinical practice. The detection sensitivity to penicillin residua ranges from 0.0015 to 0.0015 i.u. in 1 ml of milk. The method may be assessed as semi-quantitative.