Italian study
In a study of 162 cats in Italy Pennisi et al (1999) demonstrated an isolation rate of 32% in cats with a history of URTD whereas in cats with no history of URTD, the isolation rate was 13% with significant statistical difference between the 2 groups: 
 

History of URTD

Number of cats tested/ positive (% positive)

+

22/68 (32%)

-

9/67 (13%)

Isolation rate of B. bronchiseptica in cats with or without history of URTD (Pennisi et al 1999)