Diagnostic Utility of Canine C-Reactive Protein, Haptoglobin, and 25-Hydroxyvitamin-D in Dogs with Nasal Cavity Disease

In this prospective blinded study, canine C-reactive protein (c-CRP), haptoglobin (HPT), and 25-hydroxyvitamin-D (25(OH)D) were investigated for their diagnostic value in 55 dogs with nasal cavity disease (ND). After comprehensive diagnostics including a culture-dependent microbiological examination (ME) of nasal swabs, 17 dogs were excluded due to additionally detected systemic diseases or steroid pre-treatment. Included were 25 dogs with malignant ND (13 carcinomas and 12 sarcomas) and 30 dogs with benign ND (7 benign tumors, 13 idiopathic rhinitis (IR), and 10 others), as well as 10 controls. In none of the 72 dogs with ND was primary bacterial rhinitis diagnosed. Although within the reference interval, compared to the controls, c-CRP was significantly higher in dogs with ND in general and in every subgroup except for benign tumors. Serum HPT concentrations were not different among groups. Compared to the controls, 25(OH)D concentrations were significantly lower (p = 0.041) in malignant ND and sarcomas (p = 0.025). Despite pre-treatment with antibiotics (40/54; 74.1%), in 23/51 (45%) dogs, the ME was positive. Cultivated bacteria did not differ significantly between nasal diseases. The serum markers were not significantly different regarding the positivity of ME. In conclusion, the investigated serum markers were not clinically useful for the reliable detection of canine ND, as was the ME. Because of the low number of dogs with IR and positive or negative ME, further studies regarding c-CRP are needed in a larger group of IR dogs without concomitant diseases to reliably evaluate its utility in IR dogs with suspected secondary bacterial nasal infection.

Comparison of culture-dependent and -independent bacterial detection results on nasal swabs in dogs with nasal discharge

OBJECTIVES

The role of bacterial communities in the pathophysiology of canine nasal disease is still unclear. How and when to treat dogs with suspected secondary bacterial rhinitis and on which test to rely before making a decision to treat with antimicrobials has not been established. The objective is to compare the results of bacterial identification using agar-plate cultures and 16S rRNA gene amplicon sequencing in dogs with nasal discharge suspected to be of bacterial origin.

MATERIALS AND METHODS

Twenty-nine client-owned dogs presented for investigation of nasal disease were included in the study. Paired swabs were collected from the same affected nasal cavity. One swab was streaked on 4 agar media (Columbia Blood Agar, MacConkey, Chapman and Edward's). The other swab was stored in a sterile cryotube at -80°. Extracted DNA underwent a polymerase chain reaction targeting the V1-V3 region of the 16S rRNA gene.

RESULTS

At least one of the species detected by amplicon sequencing with a relative abundance of >10% was also identified by culture in 14 cases (48.3%), in association with marked predominance of one taxon (>80% relative abundance) in six of 14 cases. In 12 dogs (41.4%), the cultured isolates were rare or undetected components of the corresponding sequence libraries. A negative culture in the face of bacterial predominance (>50% relative abundance) of a potentially pathogenic bacteria detected by sequencing occurred in 17% (n=5) of cases; however, the use of other agar media may have decreased this percentage.

CLINICAL SIGNIFICANCE

Standard culture does not reliably predict the bacterial profile detected by 16S rRNA gene amplicon sequencing.