Evaluation of the Petrifilm™ Culture System for the Identification of Mastitis Bacteria as Compared to Standard Bacteriological Methods

Abstract

The largest cost associated with treating clinical mastitis during lactation is the discarded milk during and after therapy. To justify this cost, one should ensure that the present infection will respond to antibiotic therapy. Most intramammary antibiotics target gram-positive cocci organisms, and are not particularly effective against Mycoplasma spp, yeasts and mild infections caused by gram-negative pathogens. Similarly, research has demonstrated that other organisms, such as Streptococcus uberis, are highly responsive to intramammary antibiotics, or that the cure rates achieved by various intramammary treatments are not significantly better than no treatment. Thus, there has been an increasing demand for research towards the development of on-farm mastitis culturing media for early identification and accurate classification of bacterial species. Petrifilm™ plates are selective culture media products, which are used for rapid bacteriological isolation and enumeration from food products. The 3M Petrifilm™ products are small, playing card size, sample-ready plates that will allow users to easily and efficiently perform on-site microbial identification. Petriflim™ plates that are potentially useful for mastitis diagnoses are the Aerobic Count Plates, Coliform Count Plates, and Staph Express Count Plates, due to their ease of use, and the ability to reach a diagnosis in as little as 24 hours. The usefulness of the Petrifilm™ culture system for the diagnosis of mastitis has been previously reported.¹ The objective of the current project was to determine the test characteristics of Petrifilm™ to characterize the causative organism in producer-defined cases of clinical mastitis.