Genotyping of Staphylococcus aureus isolated from various sites on farms with dairy sheep using pulsed-field gel electrophoresis.
ABSTRACT We investigated the genetic diversity of 179 Staphylococcus aureus isolates recovered from various sites in 10 farms producing cheeses manufactured with raw ewe's milk. Isolates were collected from handcrafted cheeses, bulk tank milk, milk from half-udders, skin abscesses on the udder if present, hands and anterior nares of farmers, and air of the milking area. The isolates were typed using pulsed-field gel electrophoresis (PFGE) of DNA SmaI digests and compared to other isolates of S. aureus isolated in different hosts or in different locations. The results showed that nine farms were contaminated by S. aureus isolates with identical banding patterns (named OV) or by genetically related isolates (named OV'). These dominant banding patterns were found in a variable proportion of the samples from each farm (range: 11-100%). Most of the strains isolated from nasal carriage or strains isolated from other regions or from other animal species had different PFGE patterns to OV or OV', except for three strains. These results show that a single clone of S. aureus is widely distributed both in infected mammary glands and in cheese produced from raw milk. This study confirms that infected mammary glands are the main source of the contamination of dairy products in sheep.
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ABSTRACT: Staphylococcus aureus has long been recognized as an important pathogen in human disease. Due to an increasing number of infections caused by methicillin-resistant S. aureus (MRSA) strains, therapy has become problematic. Therefore, prevention of staphylococcal infections has become more important. Carriage of S. aureus appears to play a key role in the epidemiology and pathogenesis of infection. The ecological niches of S. aureus are the anterior nares. In healthy subjects, over time, three patterns of carriage can be distinguished: about 20% of people are persistent carriers, 60% are intermittent carriers, and approximately 20% almost never carry S. aureus. The molecular basis of the carrier state remains to be elucidated. In patients who repeatedly puncture the skin (e.g., hemodialysis or continuous ambulatory peritoneal dialysis [CAPD] patients and intravenous drug addicts) and patients with human immunodeficiency virus (HIV) infection, increased carriage rates are found. Carriage has been identified as an important risk factor for infection in patients undergoing surgery, those on hemodialysis or CAPD, those with HIV infection and AIDS, those with intravascular devices, and those colonized with MRSA. Elimination of carriage has been found to reduce the infection rates in surgical patients and those on hemodialysis and CAPD. Elimination of carriage appears to be an attractive preventive strategy in patients at risk. Further studies are needed to optimize this strategy and to define the groups at risk.Clinical Microbiology Reviews 08/1997; 10(3):505-20. · 17.31 Impact Factor
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ABSTRACT: A study using 100 Chios ewes was undertaken in 1992 to determine rate of clinical mastitis, prevalent bacterial pathogens in normal and abnormal milk and to investigate relationships between somatic cell counts and milk production. Mean somatic cell count from mastitis negative (non-infected) samples was 1.574 × 106 cells per ml−1. All mastitis positive samples had somatic cells in excess of 2 × 106 cells per ml−1. An increase of 0.5 × 106 cells above the mean resulted in reduction of mean individual daily production of milk by 18 g. These findings and the supporting evidence by regression and correlation analyses (r = −0.33) strongly suggest that the threshold level for subclinical mastitis in ewes should be close to 1.5 × 106 somatic cells per ml. The presence of high counts of somatic cells and of pathogens in milk samples, particularly staphylococci, are signs of subclinical mastitis and should trigger prophylactic measures to prevent the outburst of clinical mastitis.Small Ruminant Research. 01/1995;
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ABSTRACT: The Fossomatic method for SCC was compared with the direct microscopic method in 85 half-udder samples of sheep milk. The correlation coefficient was .986. The repeatability of the Fossomatic method showed average variation coefficients less than 5%. The carry-over effect between samples was less than 5%. The effect of the storage method (fresh milk, refrigerated at 4 degrees C and frozen at -19 degrees C) and the sample age were studied in 48 samples of foremilk and strippings. The storage method had a significant effect on the SCC variation. The average fresh, refrigerated, and frozen sample counts were 125,000, 110,000, and 82,000 cells/ml for foremilk and 201,000, 192,000, and 145,000 cells/ml for strippings, respectively. The effect of age on the refrigerated samples was also significant; counts were reduced by about 14% from d 1 to 7 in both types of milk. The effect of age on the frozen sample varied. These results suggest standardization of age and storage conditions of the milk samples to reduce variation of SCC. The milk must not be frozen.Journal of Dairy Science 02/1993; 76(1):115-9. · 2.57 Impact Factor