Udder Health Systems

Washed Cow Blood Agar

Purpose

This is the standard isolation agar used at Udder Health Systems Laboratory for cultivating a wide range of mastitis organisms from individual cow and bulk tank milk samples.  

Description

This cherry red, translucent agar is prepared from a blood agar base with the addition of 5% washed bovine erythrocytes and ½ strength esculin.  This blood agar has been formulated to enhance the detection of Staphylococcus aureus Alpha and Beta hemolysin when present. The addition of esculin enhances the capability of differentiating Streptococci.  Certain Streptococci will hydrolyze esculin, causing a mild background blackening for E-strep and a mild greening or no background coloration for suspect Streptococcus agalactiae and Streptococcus dysgalactiae organisms.  All suspect Streptococcus agalactiae organisms would be moved to our special Camp media.  UHS blood agar will support good growth of a wide variety of fastidious microorganisms.  When reading this agar, anticipate esculin hydrolysis on some coliforms as well.

Refer to table on back for expected culture responses.

Udder Health Systems

Modified Edwards Agar

Purpose

This is a special isolation agar used at Udder Health Systems Laboratory for selection of Streptococcus agalactiae from individual cow and bulk tank milk samples.

Description

This dark purplish red, translucent agar is prepared from a blood agar base with the addition of 5% washed bovine erythrocytes and Beta hemolysin.  This agar has been formulated with inhibitors to discourage a variety of non-target organisms. The addition of Beta hemolysin allows for the capability of differentiating Streptococci by providing a camp-like hemolytic reaction, typically within 24 hours.  The media will exhibit a complete circular hemolysis around each suspect Streptococcus agalactiae colony.  All suspect Streptococcus agalactiae organisms should be moved to our special Camp media for confirmation.  The inhibitors in the media will inhibit Staphylococcus and most coliform organisms.

Refer to table on back for expected culture responses.

Udder Health Systems

Salt Agar

Purpose

This selective agar is used at Udder Health Systems Laboratory for selection of all Staphylococci from bulk tank milk samples.

Description

This crimson red, translucent agar is prepared from a Mannitol Salt agar base with the addition of 5% washed bovine erythrocytes.  This agar has been formulated to enhance the detection of Staphylococcus aureus when present. The addition of blood to the agar provides the capability of differentiating Staphylcocci using hemolysin patterns.  All suspect Staphylococcus aureus suspects should be coagulase tested.  UHS Salt agar will support good growth of Staphylococci, while the salt content will inhibit most other bacteria.

Refer to table on back for expected culture responses.

Udder Health Systems

Camp Agar

 Purpose

This is a specialized indicator agar used at Udder Health Systems Laboratory for confirmation of Streptococcus agalactiae suspects. 

Description

This cherry red, translucent agar is prepared from a blood agar base with the addition of 5% washed bovine erythrocytes and full strength esculin.  This blood agar has been formulated to enhance the presentation of the Beta hemolysin zone of Staphylococcus aureus. The addition of esculin helps to distinguish Camp positive Streptococccus uberis from Streptococcus agalactiae.  Certain Streptococci will hydrolyze esculin, causing a background blackening for E-strep and a mild greening or no background coloration for Streptococcus agalactiae and Streptococcus dysgalactiae organisms. Streptococcus agalactiae growth within the Beta hemolysin zone will exhibit the characteristic wedge shaped complete hemolysis of the CAMP reaction. All Camp positive, esculin negative organisms are recorded as Streptococcus agalactiae.

Refer to table on back for expected culture responses.

Udder Health Systems

Inulin Agar

Purpose

This is an indicator agar used at Udder Health Systems Laboratory for differentiating Streptococcus uberis from other E-streps in isolates from individual cow samples.  The agar is also used as a selective agar in bedding samples for the isolation of Streptococcus uberis.

Description

This light purple opalescent agar is prepared from an inulin agar base. The agar has been formulated to differentiate Streptococcus uberis from other E-streps. Streptococcus uberis will ferment the sugar inulin, causing a background yellowing for Streptococcus uberis and no background color change for other suspect E-Strep organisms. On isolates from commercial dairy clinical specimens, this agar will differentiate Streptococcus uberis from other E-Streps with a sensitivity of 94 % and specificity of 92%. The most frequently false positive inulin organism isolated from field specimens is Streptococcus bovis. UHS Inulin agar will inhibit a wide variety of fastidious microorganisms.

Refer to table on back for expected culture responses.

Udder Health Systems

MacConkey Agar

Purpose

This agar is used at Udder Health Systems Laboratory for the detection, selection, and identification of various gram negative organisms from individual cow and environmental samples.

Description

One of the most common causes of environmental mastitis is coliforms which are gram-negative lactose fermenters.  This pink agar is a selective media that uses the characteristic of growth and lactose fermentation to identify gram-negative organisms.  Lactose fermentation is expressed on this agar through the production of a pink colony.  E. coli and Klebsiella spp. are the most common lactose fermenting mastitis organisms.  Both organisms produce a pink colony. E. coli colonies are pink and generally smaller compared to Klebsiella spp., which are larger and produce a pink colony with a mucoidal appearance.  Non-lactose fermenting organisms (i.e.Pseudomonas species) will also grow on MacConkey agar, however, the colonies will be colorless or opaque.  The antimicrobial components of this agar inhibit the growth of gram-positive and some gram-negative bacteria, such as Pasteurella.  When used as a secondary test, the inability of Pasteurella to grow on MacConkey agar is the primary characteristic of this organism used in its identification.

Refer to table on back for expected culture responses.

*Note: Red color can be due to pigment production, not lactose fermentation.