Phenotypic and genotypic characteristics of Staphylococcus aureus isolates from raw bulk-tank milk samples of goats and sheep

Two hundred and ninety-three isolates of Staphylococcus aureus obtained from 127 bulk-tank milk samples of goats and sheep from Switzerland were characterised by pheno- and genotypic traits. Of the 293 S. aureus isolates, 193 (65.9%) were egg yolk-negative and 15 (5.1%) were negative for clumping factor and/or protein A determined by a latex agglutinating test system. For 285 isolates, PCR amplification of the 3' end of the coagulase gene showed a single amplicon. Five differently sized PCR products of 500, 580, 660, 740 and 820 bp were distinguished. In 191 isolates (n = 293) staphylococcal enterotoxin (SE) genes were detected: 123 isolates tested positive for SEC gene, 31 for SEG gene, 28 for SEA gene, 26 for SEJ gene, 24 for SEI gene, 4 for SEB gene and 4 for SED gene. Furthermore, 126 isolates were positive for the gene encoding the toxic shock syndrome toxin 1. Coagulase gene restriction profile analysis of the 145 isolates harbouring SEA or SEC genes revealed six different patterns using AluI and five different patterns using HaeIII. In summary, within these two groups, high genotypic uniformity within the different sized coagulase gene amplicons was demonstrated. This is the first study providing comprehensive characterisation data of S. aureus strains originating from bulk-tank milk samples of goats and sheep. Remarkable differences in phenotypic traits between S. aureus originating from goats and sheep and bovine milk were found. Moreover, the high prevalence of toxin-producing S. aureus may be important as it is relevant to food hygiene.     

Phenotypic and genotypic characterization of Staphylococcus aureus isolated from raw camel milk samples

In the present study 320 milk samples collected from 160 apparently healthy camels of three different locations in Sudan were investigated for the presence of Staphylococcus aureus resulting in the isolation of this bacterial pathogen from 28 milk samples from 24 camels. Twenty-five S. aureus were identified phenotypically and by PCR mediated amplification of species-specific genes or gene segments. Investigation of the S. aureus for toxinogenic potential revealed that three S. aureus strains were positive for the enterotoxin encoding gene sec and the genes seg, sei, sem, sen and seo, representing the egc gene cluster. In addition all 25 S. aureus were positive for the superantigen-like encoding gene ssl7 (set1). Partial sequencing of gene sec of the three S. aureus strains yielded an almost complete sequence identity to the sequence of the sec variant sec2. However, all three sec2 genes of the present study showed a deletion of one base causing a frame shift and a corresponding earlier stop codon.According to the present results, the raw camel milk collected from three locations in Sudan seems to be, at least at this stage, of minor importance as vector causing staphylococcal food poisoning.     

Molecular detection of Streptococcus agalactiae in bovine raw milk samples obtained directly from bulk tanks

Mastitis is the most common infectious disease affecting dairy cattle; in addition, it remains the most economically important disease of dairy industries around the world. Streptococcus agalactiae, a contagious pathogen associated with subclinical mastitis, is highly infectious. This bacterium can cause an increase in bulk tank bacterial counts (BTBC) and bulk tank somatic cell counts (BTSCC). The microbiological identification of S. agalactiae in samples from bulk tanks is an auxiliary method to control contagious mastitis. Thus, there are some limitations for time-consuming cultures or identification methods and additional concerns about the conservation and transport of samples. Bulk tank samples from 247 dairy farms were cultured and compared through polymerase chain reaction (PCR), directed to 16S rRNA genes of S. agalactiae, followed by BTBC and S. agalactiae isolation. The mean value of BTBC was 1.08×10(6) CFU mL(-1) and the bacterium was identified through the microbiological method in 98 (39.7%; CI(95%)=33.8-45.9%) and through PCR in 110 (44.5%; CI(95%)=38.5-50.8%) samples. Results indicated sensitivity of 0.8571±0.0353 (CI(95%)=0.7719-0.9196) and specificity of 0.8255±0.0311 (CI(95%)=0.7549-0.8827). The lack of significant difference between microbiological and molecular results (κ=0.6686±0.0477 and CI(95%)=0.5752-0.7620) indicated substantial agreement between the methods. This suggests that PCR can be used for bulk tank samples to detect contagious mastitis caused by S. agalactiae.     

Incidence of Mycobacterium paratuberculosis in raw sheep and goats' milk in England, Wales and Northern Ireland

A blind survey of 104 raw sheep and goats' milk samples (90 goat, 14 sheeps) from bulk tanks on farms throughout England, Wales and Northern Ireland was carried out over a 5-month period (January-May 1998) in order to determine the incidence of Mycobacterium paratuberculosis. Each milk sample (100 ml) was divided into two 50ml portions. One portion was decontaminated with 0.75% hexadecylpyridinium chloride for 5h before culture on slopes of Herrold's egg yolk medium and in BACTEC radiometric medium. The second portion was subjected to immunomagnetic separation followed by IS900 PCR (IMS-PCR). The IMS-PCR assay was employed in order to provide a more rapid indication of the presence of M. paratuberculosis in each milk sample than is possible by culture. Information on the Johne's disease status of the sheep and goat herds that took part in the survey was not sought at the time of milk sampling. However, it subsequently emerged that at least some of the herds whose bulk milk was tested during this study were previously or currently infected with Johne's disease. Overall, during this survey one raw goats' milk sample tested positive for the presence of M. paratuberculosis by IMS-PCR (<1% of milk samples tested) but no viable M. paratuberculosis were isolated by culture. The results of this study suggest that bulk raw sheep and goats' milk from these regions of the UK may not represent significant vehicles of transmission of M. paratuberculosis to humans.     

Pseudomonas aeruginosa in raw and pasteurized milk

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.     

乳品厂原料乳卫生质量

原料乳的微生物指标直接影响着原料乳的质量。现在中、小规模乳品厂所用奶源大多为私人奶站收购干乳，通过对几份奶的检测，了解到现用鲜奶质量卫生质量相对较差，这对乳品质量造成一定影响。表１为几份收购原料乳的细菌总数，嗜冷菌数，芽孢总数及耐热芽孢检测结果。（见表１）可见，奶站有自己奶牛场的，细菌污染较轻，收购散户的污染严重。交奶不及时，贮存期长的，嗜冷菌数明显高，饲养条件及挤奶条件对芽孢菌的污染影响较明显。按GB６９１４－８６生鲜牛乳收购标准判断，原料乳整体卫生质量较差，基本都已超出等级范围。不同乳制品对…     

牛乳样品中布鲁氏菌的分离和鉴定

为进一步改良布鲁氏菌(Brucella)的分离和鉴定方法,本研究于2010年～2012年对新疆部分奶牛场进行Brucella病的监测,采用改良Brucella选择添加剂培养分离的方法,从试管凝集试验(SAT)检测阳性的25头奶牛的牛乳样中分离到9株分离菌,经VirB8-PCR方法扩增Brucella的VirB8基因对分离株进行鉴定,结果表明9个分离株均为Brucella。同时采用Brucella分子分型PCR及生物学分型方法进一步対分离株鉴定,结果显示其中7个分离株为牛3型,另外2个分离株为羊3型。本研究为奶牛Brucella病的检疫与防控提供了快速分离及鉴定方法。     

生乳与巴氏杀菌乳中糠氨酸含量及其测定方法研究

本试验研究了生乳与巴氏杀菌乳中糠氨酸含量及其测定方法,并提出糠氨酸作为巴氏杀菌乳中复原乳成分的标示物质,可鉴定巴氏杀菌乳中是否掺入复原乳.研究结果表明,生乳中糠氨酸含量应低于7 mg/100 g;乳粉中糠氨酸含量大于135 mg/100 g;不含复原乳的巴氏杀菌乳中糠氨酸含量应小于12 mg/100 g.使用高效液相色谱(HPLC)紫外检测糠氨酸平均偏差＜5%(n=5);回收率为98.2%.     

Parasitology of feeding raw sheep to fitch

Extract

Sir:–The widespread practice of feeding macerated raw carcasses and offal of cull sheep to fitch (Mustela putorius Juro) prompted some concern as to whether fitch could be a definitive host of Echinococcus granulosus, Taenia hydatigena or Taenia ovis. Because mustelids do not normally feed on sheep carcasses, the lack of records of sheep parasites in mustelids does not necessarily mean that the association could not occur.     

Heat stable inhibitors produced in raw milk.

Twenty raw farm milk samples were tested for inhibitory substances before and after being kept at room temperature until the pH fell to less than 6.3 but greater than 6.2. The tests were done using the IDF-method and the commercial Thermocult method. In both methods B. stearothermophilus var. chalidolactis is used as the test organism. In two instances a thermostable inhibitor was produced with an inhibitory potential greater than 0.01 IU/ml penicillin standard. The IDF-method was found unsuitable for the study of relatively small concentrations of antibiotics or other chemotherapeutics in milk.     

Incidence of foreign substances in raw and pasteurized milk

In 1980 to 1982, the occurrence of inhibiting substances, herbicides and chemical elements contaminating raw farm and bulk milk and pasteurized milk in different stages of technological processing was studied in the input regions of 19 dairies of the Lacrum Brno concern corporation. Residues of inhibiting substances were demonstrated by the thin-layer microbiological diffusion disk method using the testing strain of B. stearothermophilus var. calidolactis, to be present in raw milk (9.1% out of 143 samples) as well as in pasteurized milk (2.0% out of 151 samples). Chromatographic method (sensitivity 0.01-0.05 mg.kg-1 milk) was used for examining 135 raw milk samples for the occurrence of herbicides based on diazines and triazines. Herbicides were demonstrated to get into milk; residues were found in 45 samples (33.3%). Atomic absorption spectrophotometry was used for examining 143 raw milk samples for the contents of zinc, copper, iron and manganese. As to zinc content, 100% of the samples met the standard, as to iron content 99%, and as to the content of copper, 89% (Ministry of Health Directives, No. 50, 1978). The content of manganese remained within the range up to 0.1 mg.kg-1 milk in 60% of the samples. Out of the 135 milk samples (101 raw, 34 pasteurized milk ones) examined for the content of lead, four samples (3%) failed to meet the limit of the highest admissible level.     

Coxiella burnetii in bulk tank milk samples from dairy goat and dairy sheep farms in The Netherlands in 2008

In 2007, a human Q fever epidemic started, mainly in the south eastern part of The Netherlands with a suspected indirect relation to dairy goats, and, to a lesser degree, to dairy sheep. This article describes the Q fever prevalences in Dutch dairy goat and dairy sheep bulk tank milk (BTM) samples, using a real-time (RT) PCR and ELISA. Results of BTM PCR and ELISA were compared with the serological status of individual animals, and correlations with a history of Q fever abortion were determined. When compared with ELISA results, the optimal cut-off value for the RT-PCR was 100 bacteria/ml. In 2008, there were 392 farms with more than 200 dairy goats, of which 292 submitted a BTM sample. Of these samples, 96 (32.9 per cent) were PCR positive and 87 (29.8 per cent) were ELISA positive. All farms with a history of Q fever abortion (n=17) were ELISA positive, 16 out of 17 were also PCR positive. BTM PCR or ELISA positive farms had significantly higher within-herd seroprevalences than BTM negative farms. In the south eastern provinces, the area where the human Q fever outbreak started in 2007, a significantly larger proportion of the BTM samples was PCR and ELISA positive compared to the rest of The Netherlands. None of the BTM samples from dairy sheep farms (n=16) were PCR positive but three of these farms were ELISA positive. The higher percentage of BTM positive farms in the area where the human Q fever outbreak started, supports the suspected relation between human cases and infected dairy goat farms.     

Evaluation of an ELISA to detect antibodies to maedi-visna virus in individual and pooled samples of milk from sheep

An elisa was used to detect antibodies to maedi-visna virus in samples of serum and milk from individual sheep; the results obtained indicated that the elisa can be used to detect antibodies in milk. The assay was also applied to samples of bulk-tank milk; a standard curve was created and used to calculate the seroprevalence of maedi-visna in 11 flocks of sheep and the results were compared with the results obtained by applying the elisa to individual serum samples. There was good agreement between the seroprevalences calculated from the standard curve for bulk-tank milk and from the individual serum samples.     

HACCP体系在保持原料奶风味中的应用

通过对原料奶生产过程中可能出现的"ABC"三种来源的不良风味进行危害分析,确定关键控制点,并制定了保持原料奶风味的HACCP体系表。为原料奶生产过程中,保持优良风味,去除不良风味提供一种切实可行的预防措施。