Utility of blood cultures and patterns of antimicrobial resistance in dogs in Western Australia

Heidi Saarenkari

Bacterial culture of blood samples is used to identify pathogens responsible for an infection. They can be useful when the source of infection cannot be easily sampled, or the infection is residing in the vascular space. Blood culture utility is not well documented in veterinary medicine, and it is unknown if blood culture results influence a change in therapy. Therefore, a retrospective observational study was conducted in the Animal Hospital at Murdoch University (TAHMU) (Saarenkari, HK; Sharp, CR; Smart, L. Retrospective evaluation of the utility of blood cultures in dogs (2009–2018): 45 cases. J Vet Emerg Crit Care. 2021; 00: 1- 5) Forty-five dogs had a blood culture submitted over a 10-year period, of which (20%) were considered positive. No significant difference was found between the culture positive and culture negative groups regarding the most frequent reasons for blood culture, final diagnoses, survival until the blood culture result, or whether the infection was hospital- or community-acquired. Resistance to at least one antimicrobial was documented in all dogs with susceptibility reported. In the culture positive dogs, 63% had antimicrobial de-escalation and none had escalation, while 19% of the culture negative dogs had de-escalation and 7% had escalation. Given the first study showed a high proportion of bacterial resistance, results of bacterial cultures and susceptibilities were collated from dog urine and non-urine isolates from both Murdoch University (TAHMU) and clinics across Western Australia. Antibiograms were generated from this data, which display the percentage of bacterial isolates that are susceptible to a certain antimicrobial. The three most frequent bacterial species isolated in urine were Escherichia coli, Proteus spp. and Staphylococcus pseudintermedius. The most frequent antimicrobials tested in urine samples included ampicillin, amoxicillin-clavulanate, cephalexin, gentamicin, enrofloxacin, marbofloxacin, doxycycline and sulphatrimethoprim. Several resistance patterns were observed, including high to extremely high resistance of Staphylococcus spp., Escherichia coli and Enterococcus spp. to ampicillin, and moderate to extremely high resistance to of Streptococcus spp., Pseudomonas spp. and Enterococcus spp. to fluoroquinolones. For non-urine isolates, the most common bacteria isolated were Staphylococcus pseudintermedius, Pseudomonas spp. and Escherichia coli. The most frequent antimicrobials tested in non-urine samples were similar to urine samples, with the addition of amoxicillin, erythromycin and clindamycin. In the WA antibiogram, extremely high resistance was observed across multiple combinations of isolates and antimicrobials. Overall resistance between TAHMU and WA was not significantly different. Access to the antibiograms generated as part of this project will aid veterinarians in selecting appropriate antimicrobials for empirical use in dogs.

Utility of blood cultures and patterns of antimicrobial resistance in dogs in Western Australia

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