Microbiological study of transtracheal aspirates from dogs with suspected lower respiratory tract disease: 264 cases (1989-1995).

OBJECTIVE

To determine the most commonly isolated bacterial species associated with lower respiratory tract disease of dogs and to determine susceptibility of these isolates to antimicrobial agents.

DESIGN

Retrospective case series.

SAMPLE POPULATION

Transtracheal aspirates from 264 dogs with clinical evidence of lower respiratory tract disease.

PROCEDURE

Records of microbiological analyses of transtracheal aspirates obtained from dogs with clinical evidence of lower respiratory tract disease were reviewed. Analyses performed included bacterial culture (anaerobic and aerobic organisms) and susceptibility testing (aerobic organisms). The medical record of each affected dog was evaluated to determine signalment and underlying condition.

RESULTS

Bacteria were isolated from 116 of 264 (44%) samples, and 203 bacterial species were identified. Most (57%) of the samples from which bacteria could be isolated contained a single species, whereas 43% yielded cultures of mixed species. Bacterial species belonging to the family Enterobacteriaceae (particularly Escherichia coli) were isolated most commonly (45.7% of samples contained members of this group), followed by members of the genus Pasteurella (22.4%), obligate anaerobes (21.6%), beta-hemolytic Streptococcus (12.1%), Bordetella bronchiseptica (12.1%), nonhemolytic Streptococcus/Enterococcus sp group (12.1%), coagulase-positive Staphylococcus (9.5%), and Pseudomonas sp (7.8%). The most active antimicrobial drugs (inhibiting > 90% of the isolates) for aerobic microorganisms encountered most often (E. coli and Pasteurella sp) included amikacin, ceftizoxime sodium, enrofloxacin, and gentamicin sulfate.

CLINICAL IMPLICATIONS

Amikacin, ceftizoxime, enrofloxacin, and gentamicin may be rational choices for treatment of suspected infectious lower respiratory tract disease of dogs, before identification of the causative agent(s) and before results of susceptibility tests become available.