Evaluation of Speed Biogram test for detection, identification and microbial susceptibility testing in canine pyoderma and external otitis

Point-of-care testing for bacteria and yeast involved in canine pyoderma and external otitis is a possible approach to reduce both turnaround time and costs for detection and microbial susceptibility testing of infections and to reduce emergence of multidrug-resistant (MDR) pathogens that has become a significant health problem (1). The aim of this study was to evaluate a rapid in vitro diagnostic test, Speed Biogram (Bio Veto Test, La Seyne sur Mer, France) for detection, identification and microbial susceptibility testing of pathogens in canine pyoderma and external otitis, diagnosed by citology, comparing the results with those obtained by standard culture (Trypticase soy agar containing 5% of sheep blood, Microbiol, Italy) and antibiogram (Kirby-Bauer susceptibility test) methods. Speed Biogram enables the identification of the genus of the microorganisms and the evaluation of their susceptibilities of commonly used in veterinary practice antibiotics, via a simple colour change in wells 24-48h after inoculation. Sensitivity and specificity for Speed Biogram for identification of the presence of pathogenic microorganisms and for microbial susceptibility testing was calculated by a 2 x 2 table, while the agreement between Speed Biogram and standard culture and antibiogram methods (SM) was evaluated using unweighted k statistic with a 95% confidence interval (95%CI). A total of 34 canine samples were included through cytological evaluation: 11 samples from bacterial otitis, 6 samples from Malassezia spp. otitis and 11 sample from pyoderma, while 6 auricular sample were taken in healthy dogs, used as a negative control. The sensitivity and specificity of Speed Biogram for detection of the presence of pathogenic microorganisms were, respectively, 100%, 95%CI 0.88–1.00 and 100 %, 95%CI 0.54–1.00. Standard culture of 22 bacterial positive samples resulted in growth of Staphylococcus pseudintermedius (n = 15), Pseudomonas aeruginosa (n = 7), Proteus mirabilis (n = 8), Streptococcus β haemoliticus (n = 2), alone or simultaneously present, while Malassezia spp. was cultured in 6 auricular samples. Unweighted k statistics on 28 culture positive samples demonstrated a k value of 0.633 (95% CI 0.451 to 0.815) with a good agreement in the assessment of bacterial and Malassezia spp. isolation between Speed Biogram and SM. Single or multiple false antimicrobial susceptibilities or resistances with Speed Biogram were observed in 13/22 bacterial standard culture-positive samples, but the sensitivity and specificity of Speed Biogram for antibiogram results were, respectively, 85,71% , 95%CI 0.79-0.91 and 92,81%, 95%CI 0.87-0.96 and unweighted k statistics demonstrated a good or very good agreement between Speed Biogram and SM for all 13 tested antibiotics (average k=0.694) except for enrofloxacin, for which a fair agreement (k=0.54 95%CI 0.184-0.892) has been detected. Speed Biogram is a good and simple to read in house test for detection and identification of bacteria or Malassezia spp. in canine pyoderma and external otitis, with statistical good performances in microbial susceptibility testing, but care must be taken, especially regarding enrofloxacin results, as highlighted false antimicrobial susceptibilities may lead to wrong therapeutic choices, increasing the possibility of selection of MDR bacteria. [1] Walther B. et al. Multidrug-resistant opportunistic pathogens challenging veterinary infection control. Vet Microbiol. 2017;200:71-78.