Bacteriology:

Cotton-tipped swabs were taken from the sub-cutaneous lesions on the head and areas of purulent teno-synovitis after first searing the over-lying structures. The swabs were streaked across plates of Blood Agar and McConkey Agar and incubated overnight at 37 C. In addition swabs were rolled across glass slides. These slides were stained using both a Gram stain and Giemsa. Small bi-polar-stained rods were seen in smears stained by both methods, though the numbers varied from swab to swab. The bi-polar staining was more evident in the Giemsa-stained material. The gram-staining was intermediate, with a moderate amount of retention of the crystal violet colouring.
Six swabs were taken from head lesions and 1 swab from a joint lesion. All 7 swabs yielded small transparent colonies after about 14 hours incubation, though the growth ranged from scanty to abundant.

Anti-bacterial Sensitivity Testing
A modified Kirby-Bauer technique was used in which the cultures were streaked across Blood Agar plates in such a way as to provide fairly uniform numbers of bacteria across the plate. Sensitivity disks were placed in a circular pattern, the plates were incubated 14-24 hours and observed for the presence of zones of inhibition around the disks.
Wide zones of inhibition were found around all of the disks tested.

The conclusion is that the causative bacteria were, at least in-vitro, highly sensitive to most commonly used anti-bacterials.

Identification and Sero-typing of isolates
One culture from each of the three houses was submitted to another laboratory without sub-passage for the purpose of sero-typing. There were two objectives in doing this:
1. to confirm that the isolates were P.multocida
2. to verify that the strains are similar to those included in commercially-available vaccines, most immediately with a view to the protection of the replacement males.
The isolates were confirmed to be P.multocida and the results of serotyping were the same for all three isolates:
Carter System - Type D\par Heddlestone System - strong reaction to serum 7, also reactions to serum 16 and weaker cross-reactions to sera 1,9,13,14.
Advice was given by the vaccine manufacturers to the effect that the range of strains present in at least one of the commercially-available vaccines should provide protection against this infection. As always 2 applications of vaccine and an interval of about 4 weeks after the second application are required to reach maximum protection.