A Sample of Current Grant-Funded

Research Studies being Conducted at QMPS

• Raw milk quality and the risk of zoonotic pathogens (with Dept. of Food Science)

This study, which involves researchers from the section of Epidemiology, QMPS, NYSAHDC (in the Department of Population Medicine and Diagnostic Sciences) at Cornell and the University of California at Davis, is funded by a USDA grant. The Listeria project is progressing well, and a number of publications have been published, along with other publications in preparation.

• Listeriosis in dairy and beef herds (in cooperation with PM&DS and U.C. Davis)

Researchers from the section of Epidemiology, QMPS, NYSAHDC (in the Department of Population Medicine and Diagnostic Sciences) at Cornell and the University of California at Davis are involved in this study which is funded by a USDA grant.  The project started in 2003, and samples collected from several dairy farms in the State of New York are being analyzed by standard microbiological procedures as well as molecular diagnostic procedures. Two papers have been presented on this project; one at the NMC meeting in Burlington, VT and another at the International Dairy Federation in Maastricht, the Netherlands.

• Antimicrobial resistance in mastitis pathogens (with University of Guelph)

Currently, in cooperation with the Ontario Veterinary College, we are evaluating antimicrobial resistance patterns for Staphylococcus aureus before and after dry-off treatment with antibiotics. Pulsed gel strain typing is now being performed on all isolates. Preliminary results were presented at the World Buiatrics Meeting in Quebec in July 2004. 

• Infection dynamics in two dairy herds (with University of Vermont)

The New York herd has completed its year of intensive follow-up and we are now analyzing the data. The Vermont herd is working with Dr. John Barlow at the University of Vermont (UVM) as the project coordinator. Data collection has been completed on both herds and the data will be analyzed in the next year. Dr. Barlow, in collaboration with Dr. Zadoks, was able to secure additional funding from the competitive USDA grant program for molecular diagnostics.

• Cell count dynamics in New York

A paper was presented at the International Dairy Federation meeting in Maastricht, the Netherlands, which was well received. A peer-reviewed publication is in the process of being completed.

• Streptococcus uberis and other streptococci

In collaboration with a private practitioner, antimicrobial resistance in mastitis pathogens was explored. The techniques for this project had been developed as part of our on-going research program on bovine streptococci. In the veterinarian's clinic, antimicrobial sensitivity testing is performed, using standard methods. Clients of the veterinarian complained that the results from the tests did not match the outcome of mastitis treatments, and that the test overestimated the proportion of resistant bacteria. Using customized sensitivity testing and PCR, we were able to demonstrate that the interpretation criteria for the standard method were inaccurate. Based on the results of the molecular tests, alternative interpretation criteria were proposed that can be applied to the standard sensitivity tests used in the clinic.

In addition to the diagnostic work and the applied research, basic scientific research is on-going. The molecular lab is an important partner in several USDA-funded projects, including projects on streptococcal mastitis, milk quality and food safety in transitioning organic farms, and the impact of treatment of subclinical mastitis on herd level prevalence of mastitis and possible side-effects on antimicrobial resistance in mastitis-causing pathogens. The food safety component of the organic farm study will be used to develop real-time PCR detection capability for food borne pathogens in bulk tank milk. This testing will be made available for farmers submitting bulk tank milk samples for routine bacteriology and could be incorporated into the NYSCHAP program.

The diagnostic and scientific work in the Quality Milk Molecular Laboratory has been presented at numerous scientific meetings and in scientific publications. Presentations using results from the Molecular Laboratory were given at the meeting of the International Dairy Federation in Maastricht, The Netherlands, in June. Publications using results from the Molecular Laboratory appeared in the Journal of Clinical Microbiology (Multi-locus sequence typing of Streptococcus uberis provides sensitive and epidemiologically relevant subtype information and reveals positive selection in the virulence gene pauA), Veterinary Microbiology (Ribotyping of Streptococcus uberis from a dairy's environment, bovine feces and milk) and the Journal of Dairy Science (Of cats and cows: how a cat with chronic sinusitis caused an outbreak of mastitis among cows on a dairy farm). These results are shared with our veterinary and extension staff, and used in extension publications, teaching and continuing education programs.

• Chronic coliform infections (with University of Tennessee)

In this study, we are investigating the pathogenesis of chronic coliform mastitis. Three E. coli strains associated with transient infections, and three associated with persistent infections were evaluated for their ability to adhere to, invade and persist in transformed mammary epithelial cells (Mac-T). Both groups could adhere to Mac-T effectively and there was no statistical difference between each group.  By using gentamycin protection assay and immunofluorescence staining we showed that E. coli strains associated with persistent infections invaded MAC-T cells more than E. coli strains associated with transient infections.  Blocking FimH with mannose decreased but did not eliminate bacterial adherence and invasion. Two cytoskeletal disrupting agents, cytochalasin D and colchicines, inhibited the invasion of MAC-T cells. This indicates that both actin filaments and microtubules play a role in the invasion process. Genistein and wortmannin both inhibit internalization.  All of the persistent and one transient strain could survive and replicate intracellularly in Mac-Ts.  In bovine, the invasion of mammary epithelial cells and intracellular survival could provide E. coli with a survival advantage, allowing the microbes to better resist detection and clearance by both innate and adaptive immune defense mechanisms and hence play an important role in the pathogenesis of persistent coliform mastitis. Further work may lead to methods for prevention and treatment of these newly found infections in the mammary gland of cows.

• Dynamics of infectious diseases on dairy farms (RDQMA project)

As the Regional Dairy Quality Management Alliance (RDQMA) Research Pilot Project moves forward, QMPS continues to be a key player. Over a year of sampling has been completed on the research farm in New York, coordinated by QMPS staff and a baseline level of management on the farm has been set. The Pennsylvania farm (coordinated by Penn State) and Vermont farm (coordinated by University of Vermont) are also progressing in sampling and have established a baseline level.

Data from all farms are beginning to come together to show some interesting results. Dr. Bob Whitlock from University of Pennsylvania has analyzed the fecal and serum of the cattle for MAP (Johne’s Disease) over the past year and has found exciting preliminary data that shows the impact that one MAP super shedder can have on the environment of an entire farm. Likewise, Dr. Jo Ann Van Kessel and Dr. Jeff Karns from the Agricultural Research Service (ARS) in Beltsville MD, and the team at Penn State have been dealing with samples from the Pennsylvania farm, which has had an outbreak of sub-clinical salmonella on their farm this past year. This outbreak is being followed closely to ensure the continued health of the cattle and the safety of the food products coming off the farm. Also, the data that are being collected by studying the transmission of the infection are extremely valuable scientifically. Bulk tank results continue to show that all the farms on the study are excellent stewards of their animals and are high quality milk producers.

The database continues to be populated with the results from the labs and the data gathered on the farm in the form of economic data, nutrient management data and individual cow health data. An on-line management survey has also been completed this year to automate the quarterly surveys that are administered at each farm visit. Over the next year, emphasis for this project will be on securing funding through state lobbying with local congressional leaders and at the national level. With continued funding, the RDQMA-ARS liaison group will be searching for two more Northeast farms to add to the project in the 2005-2006 year.

• Milk Quality and Food Safety on Organic Dairies (USDA funded)

Over the next four years, we will be studying five dairy herds as they transition from conventional dairy management to organic dairy production. Aspects to be studied will be the dynamics of udder health and intramammary infections, antimicrobial resistance, milk quality and food safety.