Detection of staphylococcal enterotoxins in milk and milk products

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.     

Detection of prostaglandin-like substances in sow's milk

Contents Sow's milk was investigated for the presence of prostaglandin-like substances during parturition and the first stages of lactation, using a bio-assay with a cascade perfusion system. For these tests, strips of rat stomach (fundus) and colon, rabbit stomach and day-old chicken rectum were used. The presence of prostaglandin-like substances in sow's milk was confirmed, with peak levels during parturition and in concentrations which decreased with the progress of lactation. Using an extraction method specific for PGF_2α, an active fraction was received which contained between 13% (day of parturition) and 30% (day 5 of lactation) of the total contraction inducing actzvity of sow's milk. The presence of these active principles in milk is probably connected with the higher blood levels of prostaglandins at the time of parturition, and with the change of permeability in the mammary glands during secretion of the colostrum. The biological role of these cqmpounds is possibly connected with the stimulation these substances may exert on the gastro-intestinal orghns of the piglet. Inhalt: Bestimmung von Prostaglandin-ähnlichen Substanzen in der Milch der Sau Sauenmilch wurde auf das Vorhandensein von Prostaglandin-ähnlichen Substanren während der Ceburt und in der frühen Laktation untersucht. Benutzt wurde ein Bio-Assaysystem mit einem Kaskaden-Perfusionssystem. Dazu wurden Streifen des Rattenmagens (Fundus) und Colon sowie des Kaninchenmagens und von 1 Tage altem Kükenrektum benutzt. Prostaglandin-ähnliche Substanzen konnten so in der Milch festgestellt werden mit Spitzenwerten während der Geburt und in Konzentrationen, die sich während der Laktation verringerten. Unter Benutzung einer für PGF_2α, spezifischen Extraktionsmethode konnte eine aktive Fraktion isoliert werden, die 13%-his 30% (Tag der Geburt, bzw. Tag 5 der Laktation) der gesamten Kontraktionsaktivitat der Sauenmilch enthielt. Die Anwesenheit dieses aktiven Prinzips in der Sauenmilch steht wahrscheinlich in Beziehung zu höheren Blutprostaglandinspiegeln während der Geburt und mit der Veränderung der Permeabilität im Milchfluß während der Kolostralphase. Die biologkche Rolle dieser Substanzen steht möglicherweise in Beziehung mit der stimulierenden Aktivitat dieser Substanren für die Magen-Darm-Organe des Ferkels.     

Detection of Dermatophilus congolensis antibody in the milk of streptothricosis infected cows

Passive haemagglutination and agar gel diffusion tests were used to detect specific antibody to Dermatophilus congolensis antigens in serum and milk of eight streptothricosis infected Friesian milking cows. All the sera and milk samples showed the presence of antibody but titres were higher in sera. Precipitating antibodies were detected only in three sera. A possible implication of this finding is discussed with respect to passive immunity in the young calves from infected dams.     

高效液相色谱法测定羊奶中五种氟喹诺酮类药物残留量的研究

建立了一种可同时检测羊奶中五种氟喹诺酮类药物(环丙沙星、达氟沙星、恩诺沙星、沙拉沙星、二氟沙星)残留的高效液相色谱—荧光检测法。羊奶样品经乙腈提取,正己烷去脂肪,C18柱净化。以0.05 mol/L磷酸三乙胺溶液和乙腈溶液为流动相,流速为0.8 m L/min,激发波长280 nm,发射波长450 nm。结果表明环丙沙星、恩诺沙星、沙拉沙星、二氟沙星在10~200 ng/m L,达氟沙星在2~40 ng/m L呈良好的线性关系,R2均大于0.999。环丙沙星、恩诺沙星、沙拉沙星、二氟沙星的最低定量限为30μg/kg,达氟沙星的最低定量限为6μg/kg。环丙沙星、恩诺沙星、沙拉沙星、二氟沙星在30~200μg/kg的浓度添加水平上,达氟沙星在6~40μg/kg的浓度添加水平上其回收率均在70~100%,批内、批间的相对标准偏差小于20%。该方法简单快速、灵敏度高、重复性好,适用于羊奶中五种氟喹诺酮类药物残留检测。     

Detection of inhibitory substances in milk using the modified reduction micromethod]

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.     

Detection of Chlamydophila abortus in ovine milk by immunomagnetic separation-polymerase chain reaction

The present study was carried out to investigate the presence of Chlamydophila abortus, the causative agent of ovine enzootic abortion, in milk samples collected from sheep flocks with and without the history of abortion in Eastern Turkey by means of immunomagnetic separation (IMS) in conjunction with the polymerase chain reaction (PCR). A total number of 201 milk samples collected from 10 flocks with abortion and four flocks without abortion were tested. In the analysis of the milk samples by IMS-PCR, correct amplification was obtained with three (1.5%) samples originating from one flock with abortion. In the digestion of PCR positive products by AluI, restriction profiles observed in all three samples were determined to be the same as C. abortus S26/3.