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Applied and Environmental Microbiology, March 2009, p. 1315-1323, Vol. 75, No. 5
0099-2240/09/$08.00+0     doi:10.1128/AEM.01826-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Molecular Ecology of Listeria monocytogenes: Evidence for a Reservoir in Milking Equipment on a Dairy Farm{triangledown}

Alejandra A. Latorre,1* Jo Ann S. Van Kessel,2 Jeffrey S. Karns,2 Michael J. Zurakowski,1 Abani K. Pradhan,1 Ruth N. Zadoks,1,{dagger} Kathryn J. Boor,3 and Ynte H. Schukken1

Department of Population Medicine and Diagnostic Sciences, Cornell University, Ithaca, New York 14850,1 Environmental Microbial Safety Laboratory, ANRI, USDA-ARS, Beltsville, Maryland 20705,2 Department of Food Science, Cornell University, Ithaca, New York 148533

Received 6 August 2008/ Accepted 18 December 2008

A longitudinal study aimed to detect Listeria monocytogenes on a New York State dairy farm was conducted between February 2004 and July 2007. Fecal samples were collected every 6 months from all lactating cows. Approximately 20 environmental samples were obtained every 3 months. Bulk tank milk samples and in-line milk filter samples were obtained weekly. Samples from milking equipment and the milking parlor environment were obtained in May 2007. Fifty-one of 715 fecal samples (7.1%) and 22 of 303 environmental samples (7.3%) were positive for L. monocytogenes. A total of 73 of 108 in-line milk filter samples (67.6%) and 34 of 172 bulk tank milk samples (19.7%) were positive for L. monocytogenes. Listeria monocytogenes was isolated from 6 of 40 (15%) sampling sites in the milking parlor and milking equipment. In-line milk filter samples had a greater proportion of L. monocytogenes than did bulk tank milk samples (P < 0.05) and samples from other sources (P < 0.05). The proportion of L. monocytogenes-positive samples was greater among bulk tank milk samples than among fecal or environmental samples (P < 0.05). Analysis of 60 isolates by pulsed-field gel electrophoresis (PFGE) yielded 23 PFGE types after digestion with AscI and ApaI endonucleases. Three PFGE types of L. monocytogenes were repeatedly found in longitudinally collected samples from bulk tank milk and in-line milk filters.

* Corresponding author. Mailing address: Cornell University—Quality Milk Production Services, 22 Thornwood Drive, Ithaca, NY 14850. Phone: (607) 255-8202. Fax: (607) 257-8485. E-mail: aal39{at}cornell.edu

{triangledown} Published ahead of print on 29 December 2008.

{dagger} Present address: Department of Veterinary Clinical Studies, Royal (Dick) School of Veterinary Studies, University of Edinburgh, Roslin, Midlothian EH25 9RG, Scotland, United Kingdom.

Applied and Environmental Microbiology, March 2009, p. 1315-1323, Vol. 75, No. 5
0099-2240/09/$08.00+0     doi:10.1128/AEM.01826-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.





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