Anti-staphylococcal effect of enterocin in Sunar and yogurt.

Enterocin was used to control the growth of Staphylococcus aureus strains SA1 and Oxford 209P in Sunar (milk nourishment for suckling babies) and during the yogurt-making process. Reduction by three orders of magnitude was noted in the growth of SA1 strain in Sunar milk nourishment between the enterocin-containing (ES) and the control samples (CS) at 1-d cultivation. An inhibitory effect of enterocin was observed when surviving of SA1 cells were checked 6 h after the start of cultivation (2 h after enterocin application; enterocin was applied after 4 h). Decrease in the count of Oxford 209P strain in yogurt was detected in ES after 1 d of storage in comparison with CS (10(3) and 10(0) CFU mL-1 g-1). Thus a decrease by three orders of magnitude was found between ES and CS at the time mentioned. On the other hand, no bacteriocin activity was detected in ES after 1 d. Activity was detected only immediately after enterocin addition to ES (400 AU/mL) as well as after 1 and 3 1/2 h (200 AU/mL). Although the slight regrowth of the indicator was obtained up to 1 week of yogurt storage, the difference between ES and CS persisted. The lowest pH of the final yogurt product was noted in the reference yogurt sample but differences among the pH values of yogurt samples were not significant.

[Oxytetracycline in the milk of dairy cows with clinical signs of mastitis during the lactation period]. / Vylucovanie oxytetracyklínu mliekom dojníc s klinickými prejavmi mastitídy pocas laktacného obdobia.

The objective of this study was to determine the oxytetracycline residues in milk from cows with clinical mastitis dosed with two extra-label routes of oxytetracycline administration not only during antibiotic's treatment (5 days), but also six days after treatment by use of a liquid chromatography method of testing with a detection limit of 20 ppb. Both groups of animals were treated once daily for five milkings at 24-hour intervals following morning milkings. Composite milk samples (equal volumes of foremilk from each quarter) were collected during morning and afternoon milkings, mixed together (1:1), and stored until analyzed. Milk samples were analyzed just before the first treatment (0 hour) and ten times at 24-hour intervals. Residue studies in milk cows indicate that oxytetracycline passes into milk. Residues in milk were higher for the cows receiving oxytetracycline by intramammary route (Tab. I) than for the cows receiving oxytetracycline intramuscularly (Tab. II). The highest mean data were 195.68 mg/kg after intramammary infusion (Fig. 2) and 2.74 mg/kg after intramuscular injection (Fig. 3) on the 5th day of the treatment beginning. The analysis data showed that oxytetracycline persisted in milk for as long as two days after both treatments at the concentration 0.03 mg/kg versus 0.02 mg/kg, respectively. No residues were detected in milk of any animal from the 4th day of the cessation of the therapy (Fig. 1) as detected by the HPLC method.

Determination of staphylococcal enterotoxins in milk and milk products by three methods.

For food evaluation, the determination of the number of Staphylococcus aureus colonies is insufficient in the view of present scientific knowledge. The results, advantages and disadvantages of diagnostic methods are demonstrated on an example of three methods of detection of staphylococcal enterotoxins in milk and milk products. 133 strains were investigated with the method of biotyping of Staphylococcus aureus strains. Four of their strains were included in biotype A, seven strains of S. aureus were not included in any biotype and the other strains belonged in biotypes C and E. This method can be used as an auxiliary method for evaluation of foods containing S. aureus bacteria. The agar-gel precipitation method of enterotoxin detection in isolated strains of Staphylococcus aureus has just restricted valiability. When examining 96 strains of S. aureus with this method, strains which were producing staphylococcal enterotoxins were isolated 17 times. The main disadvantage of this method is a fact that the result concerning the isolated strains need not be identical with the result of enterotoxin detection in food. Direct assays of staphylococcal enterotoxins in milk and milk products using an enzymoimmunological method (ELISA test) seem to be most promising, mainly due to their high sensitivity (0.0001-0.001 micrograms.ml-1) and other advantages.

[Transport of nitrates and nitrites into the milk of dairy cows through the digestive system]. / Prestup dusicnanov a dusitanov do mlieka dojníc cestou tráviaceho traktu.

Increased nitrate concentrations in milk are not only dangerous to human health as the milk is the material for production of baby and infant food, but they cause also many problems in technological milk processing. The study was aimed at the transfer of nitrates and nitrites into milk of dairy cows following nitrate loading. An experiment included 6 dairy cows of the Slovakian Spotted breed at the Experimental Veterinary Centre at Zemplínska Teplica. Prior to start of the experiment samples of feedstuffs and feed water, milk were taken and examined for the presence of nitrates and nitrites. KNO3 in water solution was applied to selected dairy cows in two-week intervals in single peroral doses of 150; 75; 37.5; 18.75 and 9.5 g two hours before evening milking. Nitrate and nitrite residue contents were studied in individual milk samples obtained from manual milking 2, 14, 26, 38 and 50 hours after application of appropriate KNO3 amount. Following the peroral application of KNO3 to dairy cows, a marked increase in nitrate content in milk appeared in dependence on applied KNO3 (Tab. I). Average value of residual nitrate in milk two hours after administration of 150 g of KNO3 was 34.60 mg of NO3-/l. Increased levels of residual nitrate in milk were found also 38 hours after KNO3 application. Nitrate content in milk after 50 hours was almost identical with that that was determined in milk of experimental cows from morning milking on the day of administration of 150 g of KNO3, considered as the control samples. The values of residual nitrate exceeded 0.05 mg neither in single sample of NaNO2/l.(ABSTRACT TRUNCATED AT 250 WORDS)

[Detection of staphylococcal enterotoxins in milk and milk products]. / Detekcia stafylokokových enterotoxínov v mlieku a v mliecnych výrobkoch.

For food evaluation the determination of the number of Staphylococcus aureus (hereinafter S. aureus) colonies is insufficient in view of present scientific knowledge. The results, advantages and shortcomings of diagnostic methods are demonstrated on an example of three methods of detection of staphylococcal enterotoxins in milk and milk products. 133 strains were investigated by the method of biotyping of S. aureus strains. Four strains of S. aureus were included in biotype A, seven xin-producing strains were isolated seventeen times by detection of 96 S. aureus strains were not included in any biotype, the other strains belonged to biotypes C and E. This method can be used as an auxiliary method of evaluation of foods containing S. aureus bacteria. The agar-gel precipitation method of enterotoxin detection in isolated strains of S. aureus has just restricted validity. The enteroto-strains. The main shortcoming of this method is a fact that the result concerning the isolated strains need not be identical with the result of enterotoxin detection in food. Direct assays of staphylococcal enterotoxins in milk and milk products using an enzymoimmunological method seem to be the most promising, mainly due to their high sensitivity (0.0001-0.001 micrograms.ml1-) and other advantages. Positive and negative results are presented on an example of two model trials with winter sheep milk cheese.