Pathogens of the Respiratory Tract

Even in healthy animals, bacteria of different species can be cultured from the respiratory system. Clinical evaluations of the lower respiratory tract demonstrated that 35–50% of healthy dogs were culture-positive (5). True primary pathogens of the lower respiratory tract are viruses and bacteria, including Bordetella bronchiseptica, Mycoplasma, Streptococcus zooepidemicusm, and Mycobacteria, which are able to overcome respiratory defense mechanisms, and induce respiratory tract infections (5).

The majority of bacteria to be found in the trachea and bronchial tree of healthy and diseased animals seems to be secondary opportunistic invaders, in most cases aspirated from the gastrointestinal tract, which take advantage of factors weakening the host's defense system and become pathogenic.

respiratory tract infections
Secondary Pathogen Dogs

Secondary Pathogens Dogs

Secondary Pathogen Cats

Secondary Pathogens Cats


Klebsiella in the Respiratory Tract

Pathogens of Upper Respiratory Tract Infections

Upper Respiratory Pathogens in Dogs

Upper Respiratory Pathogens in Cats

Pathogens of Lower Respiratory Tract Infections

Lower Respiratory Pathogens in Dogs

Lower Respiratory Pathogens in Cats

Antibiotic Activity

*C=bactericidal, S= bacteriostatic
**Based on Pseudomonas aeurginosa
0 = not likely effective due to intrinsic or acquired resistence
1+= <50% probability of in vitro susceptibility
2+= 50–74% probability of in vitro susceptibility
3+= 75–89% probability of in vitro susceptibility
4+= >90% probability of in vitro susceptibility

Ec= Escherichia coli
Pm= Proteus mirabilis
Kp= Klebsiella pneumoniae
Ssp= Staphylococcus species
Pmult= Pasteurella multocida
Psp= Pseudomonas species
St. Sp Streptococcus species
Bb= Bordetella bronchiseptica

(1) Blondeau JM. Steps To Antimicrobial Therapy. 2nd edition. North American Compendiums Inc. 2014, page 135
(5) King LG, Boothe DM: Bacterial infections of the respiratory tract in dogs and cats. Veterinary Learning Systems Kansas USA, 1997.