Banca de QUALIFICAÇÃO: LARISSA RAFAELI IZOLAN

Uma banca de QUALIFICAÇÃO de MESTRADO foi cadastrada pelo programa.
STUDENT : LARISSA RAFAELI IZOLAN
DATE: 01/12/2023
TIME: 08:00
LOCAL: Web Conferência - Google Meet: meet.google.com/cym-bqcs-vot.
TITLE:

GENOTYPING AND VIRULENCE FACTORS OF Streptococcus uberis ISOLATED FROM BOVINE MASTITIS IN DAIRY HERDS OF THE MIDWEST REGION OF SANTA CATARINA – BRAZIL.

KEY WORDS:

Dairy cattle farming; MALDI-TOF MS; PCR.

PAGES: 45
BIG AREA: Ciências Agrárias
AREA: Medicina Veterinária
SUMMARY:

Mastitis is one of the primary sanitary concerns in dairy cattle farming, as it not only leads to significant economic impacts but is also a major cause of antimicrobial use in herds. Among the bacteria involved in the etiology of bovine mastitis, Streptococcus uberis (S. uberis) stands out due to its high prevalence in herds, being the most frequently isolated Gram-positive microorganism from cases of clinical mastitis in dairy cattle. Intramammary infections caused by S. uberis present significant variation in terms of duration, severity, and cure rates, partly due to the genetic variability of S. uberis and its numerous virulence factors. In this context, the objective of this study was to genotype strains of S. uberis isolated from chronic cases of subclinical mastitis in dairy herds in the Midwestern region of Santa Catarina, Brazil, by investigating virulence and antimicrobial resistance genes. The S. uberis strains used in the study were obtained through the routine microbiological diagnosis of a cooperative located in the city of Concórdia, Santa Catarina. To do so, cows with a somatic cell count (SCC) exceeding 200,000 cells per mL of milk for two consecutive months were selected for milk sample collection from the affected mammary quarters for microbiological culture, which was performed on SmartColor 2 (Onfarm®) chromogenic agar plates. A total of 1401 samples were analyzed, and 133 samples classified as belonging to the Streptococcus genus. These strains were cryopreserved for subsequent molecular evaluation, and then samples were re-isolated on 5% bovine blood agar with incubation at 37°C for 24 hours to enable ribosomal protein extraction. Subsequently, the Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry (MALDI-TOF MS) technique was used to generate the mass spectra of each strain. Out of the 133 samples, 64 strains of Streptococcus uberis from 25 herds in the Midwestern region of Santa Catarina were confirmed. To assess the in vitro sensitivity of the S. uberis strains to antimicrobials, an antibiogram was performed using the disc diffusion technique. For future Polymerase Chain Reaction (PCR) protocols targeting the research of virulence and antimicrobial resistance genes, the cryopreserved S. uberis strains were re-isolated in Brain Heart Infusion (BHI) broth after 24 hours of incubation at 37°C, and nucleic acids were subsequently extracted using the commercial NewGene FastX® Kit. The preliminary results obtained are as follows: 1) A high genetic diversity among the evaluated S. uberis strains, as identified by the MALDI-TOF MS technique; 2) A significant number of strains exhibiting in vitro multidrug resistance to the tested antimicrobials. These results underscore the importance of genetic characterization of circulating S. uberis strains in the dairy herds of the Midwestern region of Santa Catarina. This knowledge will contribute to understanding their epidemiological profile, as well as mechanisms of resistance and virulence, thereby enabling the implementation of more effective prophylactic and control measures.

COMMITTEE MEMBERS:
Interno - 2613308 - DELANO DIAS SCHLEDER
Interna - 1046884 - ELIZABETH SCHWEGLER
Interno - 1810731 - JULIANO SANTOS GUERETZ
Presidente - 2276764 - MARCELLA ZAMPOLI DE ASSIS
Interno - 1755182 - MARIO LETTIERI TEIXEIRA
Interna - 2408296 - SORAYA REGINA SACCO