Antimicrobial resistance and virulence of E. coli strains isolated from bovine mastitis with different clinical scores

Author(s)

Simony Trevizan Guerra

• Document type: Doctoral Thesis
• Press: Botucatu. 2019-08-02.
• Institution: Universidade Estadual Paulista (Unesp). Faculdade de Medicina Veterinária e Zootecnia. Botucatu
• Defense date: 2019-07-25
• Advisor: Márcio Garcia Ribeiro

Abstract

Escherichia coli is the major pathogen involved in the etiology of bovine mastitis from the environment origin. This pathogen is characterized by a complexity of virulence factors (VF). Mammary infections by E. coli has shown a wide range of clinical signs causing changes in milk (score 1 or mild), quarters (score 2 or moderate), and systemic signs (score 3 or severe). Nevertheless, to date, the profile of the genes related to the virulence of this pathogen in mammary infections and the severity scores of the cases are not fully understood. In this scenario, a panel of 18 genes associated with extra-intestinal E. coli (ExPEC) were investigated, in addition to in vitro swimming and swarming motility profile, and antimicrobial susceptibility/resistance pattern among 114 E. coli strains isolated from cows with clinical mastitis showing severity scores 1 (45/114=39.5%), 2 (62/114=54.4%) and 3 (n=7/114=6.1%). The main genes related to VF harbored by isolates were adhesins (fimH, 114/114=100%; ecpA, 73/114=64.0%; fimA, 36/114=31.6%), serum resistance (traT, 93/114=81.6%; ompT, 40/114=35.1%), siderophores (irp2, 11/114=9.6%) and hemolysin (hlyA, 8/114=7%). Among studied isolates, 99.1% (113/114) showed in vitro resistance to bacitracin and cloxacillin, 98.2% (112/114) to lincosamin, and 54.4% (62/114) to erytromycin. Out of the total isolates, 98.2% (112/114) were considered multidrug resistant based on multiple antimicrobial resistance (MAR) index. No statistical difference was observed between swimming (13.8mm) and swarming (13.5mm) motility assays, as well as severity scores of clinical mastitis, and the ExPEC associated genes studied. The multidrug resistance of the isolates highlights the need for responsible use of antimicrobials on therapy and control of bovine mastitis. The high frequencies among isolates of the genes related to serum resitance (traT, ompT) and adhesion of the pathogen (ecpA), in addition to main associations between the genes fimH, ecpA e traT among cows with severity scores 1 (7/45=15%) and 2 (14/62=22.6%), is a circumstantial evidence that the genes traT, ecpA e ompT may be used as biomarkers of ExPEC among xviii clinical mammary infections in cows. Nevertheless, the lack of statistical significance between the genes studied and clinical scores indicates that other virulence properties or factors intimately related to cows might be involved in clinical bovine mastitis and severity of cases. In addition, the genes related to ExPEC ompT (serum resistance), ibe10 (invasins), and ecpA (adhesin) were investigated by first time among cows with mastitis where scores of clinical severity were assessed. (AU)

• FAPESP's process: 17/08102-8 - Characterization, molecular profile, virulence and multidrug resistance factors in strains of Escherichia coli isolated from Bovine Mastitis with different scores
• Grantee: Simony Trevizan Guerra
• Support Opportunities: Scholarships in Brazil - Doctorate (Direct)