Blue Rabbit Coagulase Media

Description

A critical procedural error can occur in some testing laboratories when diagnosing Staphylococcus aureus in conventional mastitis culture. This error occurs when the analyst relies solely on visual hemolytic changes of Staphylococcal colonies grown on Blood Agar to make the determination of Staphylococcus aureus or Staphylococcus spp. This diagnostic error may result in significant underreporting of Staph aureus positive cows, which consequentially may accelerate the rate of new infections or in extreme cases allow a major outbreak of Staph aureus to go undetected. A significantly under-appreciated risk in the industry is that a high percentage (frequently 30-40%) of Staph cows can harbor strains that produce only minor hemolysis or no hemolysis at all.

The use of UHS chromogenic agars assist analysts by highlighting chromogen positive Staphylococcal colonies for confirmation with Blue Rabbit coagulase media. This media provides superior detection of the coagulase enzyme by producing complete firm gelling of blood plasma, with overnight incubation or even as quickly as 4 hours. This media eliminates the ambiguous “weak” or “soft” clot observations seen with many conventional bovine or rabbit plasma test methods.

The Udder Health Systems coagulase plasma is shipped in the frozen state and is ready to use. It is sold in a 48ml vial. It is good for several years in the frozen state but should be used within 7 days of dispensing.

All of these organisms will grow in the coagulase broth; this growth will produce a cloudy appearance. This is not to be interpreted as a positive reaction, only the coagulation reaction is a positive result.

* All Staph spp. will grow in the coagulase broth, but only Staph aureus will generate a positive coagulation reaction. The coagulation can be detected in as little as 4 hrs. Typically the reaction is still readable in 24 hrs. Some false negatives will occur when coagulation occurs but the clot will lyse again by 24 hrs.

† Some strains of E. coli can produce the coagulase reaction. A false positive result can occur if the analyst mistakenly tests an E. coli colony. It is the responsibility of the analyst to only perform this test only on Staphylococcus genus isolates.