Urinary tract infections (UTIs) affect nearly half of women and an estimated 14 % of the canine companion animal population at least once in their lifetime. As with humans, Escherichia coli is the most commonly isolated bacteria from canine UTIs and infections are dominated by specific phylogenetic groups with notable virulence attributes. In this study, we evaluated uropathogenic E. coli (UPEC) (n = 69) isolated from canine UTIs phenotypically and genotypically for virulence factors, biofilm formation and antimicrobial resistance profiles. Biofilm formation in UPEC strains was positively associated with common virulence factors including papG (p = 0.006), fimH (p < 0.0001), sfaS (p = 0.004), focA (p = 0.004), cnf-1 (p = 0.009) and hlyA (p = 0.006). There was a negative association between biofilm formation and phenotypic antimicrobial resistance for ampicillin (p < 0.0004), ciprofloxacin (p < 0.0001), and trimethoprim-sulfamethoxazole (p < 0.02), as well as multidrug resistance (isolates resistant to ≥ 3 classes of antimicrobials) (p < 0.0002), and the presence of extended spectrum beta-lactamase (ESBL)-producing genes (p < 0.05). In conclusion, UPECs isolated from clinical cases of canine UTIs show a broad negative association between antimicrobial resistance and biofilm formation, and this observation is supported both by phenotypic and genotypic endpoints. As the biofilm formation may result in antimicrobial tolerance, this could be a secondary evasive tactic of UPEC lacking traditional antimicrobial resistance traits. This observation is important for veterinary practitioners to consider when treating puzzling chronic intractable and/or recurrent cases of UTI that appear to be susceptible to antimicrobial therapy via traditional antimicrobial susceptibility testing (AST) methods.

尿路感染（UTIs）一生中至少有一次影响到近一半的女性和大约14％的犬科动物。与人类一样，大肠杆菌是从犬UTI中分离的最常见细菌，感染主要由具有明显毒力属性的特定系统发育群体控制。在这项研究中，我们评估了从表型和基因型上从犬UTI中分离出来的尿路致病性大肠杆菌（UPEC）（n = 69）的毒力因子，生物膜形成和抗菌素耐药性。UPEC菌株中生物膜的形成与常见的毒力因子呈正相关，这些因子包括pap G（p = 0.006），fim H（p <0.0001），sfa S（p = 0.004），foc A（p = 0.004），cnf -1（p = 0.009）和hlyA（p = 0.006）。生物膜的形成与氨苄西林（p <0.0004），环丙沙星（p <0.0001）和甲氧苄氨磺胺甲基异恶唑（p <0.02）的表型抗药性之间存在负相关性，以及多药耐药性（对≥3类抗药性的分离株） （p <0.0002），以及存在产生超广谱β-内酰胺酶（ESBL）的基因（p <0.05）。总之，从犬UTI的临床病例中分离出的UPEC在抗菌素耐药性和生物膜形成之间显示出广泛的负相关性，这一观察结果受到表型和基因型终点的支持。由于生物膜的形成可能导致抗菌素耐药性，这可能是缺乏传统抗菌素耐药性特征的UPEC的次要规避策略。