Petra Winter

A case of sporadic ovine mastitis caused by Listeria monocytogenes and its effect on contamination of raw milk and raw-milk cheeses produced in the on-farm dairy

We describe a case of listerial mastitis in a flock of 130 sheep. The animals were housed at a farm where the bulk raw ewe milk was processed to produce raw milk soft cheese. List. monocytogenes was shed from the right mammary complex. Shedding was observed over a period of 99 d. A mean level of 4-56 x 10(4) cfu (colony forming units) Listeria monocytogenes/ml was recovered from the raw milk originating from the infected udder. The numbers ranged from 9 x10(1) to 2.95 x 10(5). The bulk milk was contaminated by approx. 5.7 x 10(3) cfu/ml. In the cheese product, 2.0 x 10(2) cfu List. monocytogenes/g were constantly detectable for a period of 7 d post manufacture. The starter culture used for coagulation had a pivotal influence on the behaviour of List. monocytogenes during cheesemaking. Using the same mesophilic buttermilk culture as used by the farmer allowed numbers of Listeria to increase 60-fold within 12 h owing to a delayed acidification of the bulk milk. Addition of a thermophilic yogurt culture reduced the numbers of Listeria within 8 h of incubation.

Important Vectors for Listeria monocytogenes Transmission at Farm Dairies Manufacturing Fresh Sheep and Goat Cheese from Raw Milk

The aim of this study was to determine the transmission routs of Listeria spp. in dairy farms manufacturing fresh cheese made from ovine and caprine raw milk and to evaluate the impact of Listeria monocytogenes mastitis on raw milk contamination. Overall, 5,799 samples, including 835 environmental samples, 230 milk and milk product samples, and 4,734 aseptic half-udder foremilk samples were collected from 53 dairy farms in the dairy intensive area of Lower Austria. Farms were selected for the study because raw milk was processed to cheese that was sold directly to consumers. A total of 153 samples were positive for Listeria spp., yielding an overall prevalence of 2.6%; L. monocytogenes was found in 0.9% of the samples. Bulk tank milk, cheese, and half-udder samples were negative for Listeria spp. Because none of the sheep and goats tested positive from udder samples, L. monocytogenes mastitis was excluded as a significant source of raw milk contamination. L. monocytogenes was detected at 30.2% of all inspected farms. Swab samples from working boots and fecal samples had a significantly higher overall prevalence (P < 0.001) of L. monocytogenes (15.7 and 13.0%, respectively) than did swab samples from the milk processing environment (7.9%). A significant correlation was found between the prevalence of L. monocytogenes in the animal and in the milk processing environment and the silage feeding practices. Isolation of L. monocytogenes was three to seven times more likely from farms where silage was fed to animals throughout the year than from farms where silage was not fed to the animals.

Dynamics of experimentally induced Staphylococcus epidermidis mastitis in East Friesian milk ewes

The responses of five lactating East Friesian milk ewes to experimental mammary infection with Staphylococcus epidermidis and of five control ewes were examined over a period of 10 weeks. Infection caused an influx of neutrophils into milk, the numbers of which started to rise 4 h post infection and peaked 24 h after infection. The initial response was accompanied by mild fever and mild leucopaenia in blood (8 h after infection). No other signs of systemic infection were observed. Milk appeared normal at all times, although the milk yield of infected ewes tended to decline. Staphylococci were absent in milk from four ewes at 2 d and at 3 d after infection, but re-emerged intermittently in four of five ewes at subsequent samplings. Cytokines in milk were measured by ELISA. IL-8 was elevated in infected glands at 2 h and peaked at 8 h. In the four ewes intermittently shedding bacteria, IL-8 remained elevated until the final sampling at 10 weeks. IL-1beta was transiently elevated at 1 d and 2 d and showed a pronounced peak in one sheep. Milk samples from this ewe were bacteriologically negative, somatic cell count (SCC) was within the normal range and the concentrations of IL-1beta, as well as IL-8, were similiar to the control group (n=5) from 1 week after infection until the final sampling. Histological examination revealed leucocytic infiltrates in the four glands remaining infected at the end of the experiment, and a high level of CD5+ lymphocytes in three ewes. The results suggest that the relationship between the initial neutrophil influx and the proinflammatory cytokines may be responsible for determining the course of infection. Subclinical mastitis due to coagulase-negative staphylococci leads to minor changes in milk yield and milk constituents.

Tolerability of N-chlorotaurine in the bovine mammary gland.

N-Chlorotaurine (NCT) is a promising endogenous agent for topical treatment of infections. We tested the tolerability and pharmakokinetics of NCT in the bovine mammary glands in a phase 1 study. Three concentrations of NCT in water (0.1%, 1.0%, 2.0%) were administered intramammarily in each of two cows. Into two quarters of the udder 100 ml NCT was injected into each twice daily for 5 d, while 0.9% NaCl was injected into the other two quarters in a randomized and blinded manner. Samples of milk were taken to determine the number of leucocytes and the activity of NCT, and samples of urine and blood to determine the taurine and chloride concentration. Chloride concentrations in serum samples were determined by an ISE-Unit of a Modular-System of the Roche Diagnostics company. The udder was monitored clinically for signs of inflammation. Oxidative activity could be detected in the milk after single irrigations for 15 min (0.1% NCT) and for maximally 5 h (1% and 2% NCT), respectively. On day 2, leucocytes increased to 4 x 10(6)/ml in the NCT group, while they remained 1 x 10(6)/ml in the saline group. However, on days 3-5 they increased to (5-7) x 10(6) in both the NCT and control group without any statistical difference. One day after the end of dosing the number decreased significantly and reached the baseline (<1 x 10(6)/ml) on day 10. The decrease was similar in both groups. Except for sporadic slight induration of single quarters in both groups and slight reduction of milk performance no disorders occurred. Taurine levels in blood and urine did not change. Irrigation of the bovine mammary gland with both NCT and saline caused a transient increase of leucocytes in the milk, but no severe side effects. The absence of residues and decay products may be a great advantage of NCT over other antimicrobial agents.