Erforschung der Erreger von Mastitis, insbesondere des Nachweises von S. aureus

• Forschungsstelle: BLV
• Projektnummer: 1.10.06
• Projekttitel Englisch: on causative organisms of bovine mastitis with emphasis on detection of Staphylococcus aureus

Schlüsselwörter (Englisch)

Staphylococcus aureus, mastitis, economic damage, cattle, bacteriological testing, sensitivity

Kurzbeschreibung (Englisch)

Staphylococcus aureus (S. aureus) is the most common cause of contagious mastitis in cattle and causes significant economic damage worldwide. Diagnosis of S. aureus by bacteriological testing of quarter milk samples is not satisfactory as the sensitivity is inadequate and the specificity is limited. As a consequence, we developed a novel molecular biological assay which is highly specific and which is 500 to 2000 times more sensitive in clinical milk samples than conventional
bacteriology. In addition we were able to demonstrate by genotyping that there were various udderassociated subtypes whereby 1 subtype (genotype B, GTB) was particularly problematic as it was pathogenic and was associated with high infection rates (up to 87% of cows of a herd were infected).
So far, our investigations were based on single-quarter milk samples taken under aseptic conditions. For control and monitoring whole herds, however, analytics based on bulk tank milk (BTM) samples would be most efficient and most economic. As a consequence, we propose as a first project (field study) to evaluate our novel BTM analytics specific for S. aureus GTB and to investigate the epidemiology of this subtype in Swiss dairy herds. The analytics includes our method
of preparing bacteria from milk together with 3 real-time quantitative PCRs (qPCRs) for the detection of a GTB-typical point mutation within the lukE gene and for recognizing the sea and sed genes. In a second project and in collaboration with epidemiologists, different control strategies will be simulated at the herd and country level and their financial impact will be analyzed. In order to evaluate the mathematically best control strategy in reality, a pilot project will then be launched
including detection, sanitizing and monitoring of affected herds.
Based on our BTM qPCR analytics, an efficient and successful control of S. aureus GTB mastitis is expected. Minimization of this agent in dairy herds is assumed to massively reduce the high financial losses caused by bovine mastitis in Switzerland.

Projektziele (Englisch)

The problems caused by S. aureus are considered as a challenge of great importance for dairy farming. Minimizing S. aureus GTB in the Swiss dairy cow population by regular application of our BTM qPCR analytics, however, would be very promising and is expected to reduce massively the costs in the dairy industry. As a consequence, involved people and organisations would like to have the BTM qPCR analytics soon. Further interest is shown by institutions concerned in disease control or food hygiene as BTM analytics might be suitable to get rapid information about the presence of S. aureus and further bacteria in milk as well as about the spread of a (udder-associated) disease within a population.
Before starting the high throughput implementation of the BTM qPCR analytics for routine purposes, however, we are convinced that further evaluation of the analytics is necessary. In particular, we propose 2 projects lasting together 3 to 4 years:
• Project „field study“: the BTM qPCR analytics for the selective detection of S. aureus GTB of Boss et al. will be evaluated in a field study. In addition, the epidemiology of this pathogen will be investigated.
• „Pilot project“: in a pilot project, the control (minimization, monitoring) of S. aureus GTB will be analyzed by simulating different control strategies at the herd and country level as well as by verifying the best strategy in reality.

URL-Adressen (Deutsch)

1.10.06 Graber ALP - Nachweis Staph. aureus (063-504/3/23)