2.6. Case definition
The criteria for accepting that a fish was diseased and positive for
marine flexibacteriosis involved two parts: method of recovery and
quantification of colonies and cells. T. maritimum had to be recovered from mortalities by culture and in smears by IFAT as these methods
are more specific than Gram stain. The minimum abundance of cells
required for a positive result was 10–50 bacteria per 25 fields for
IFAT and Gram stain. The minimum abundance required to record a
positive result in culture was growth of colonies extending to the first
streaking lines