Banca de QUALIFICAÇÃO: DÁRCIO LUIZ DE SOUSA JÚNIOR

Uma banca de QUALIFICAÇÃO de DOUTORADO foi cadastrada pelo programa.
STUDENT : DÁRCIO LUIZ DE SOUSA JÚNIOR
DATE: 24/03/2025
TIME: 14:00
LOCAL: Google Meet
TITLE:

ANTIBACTERIAL AND ANTIFUNGAL POTENTIAL OF A LECTIN FROM THE SEEDS OF SPAW BEANS (Canavalia gladiata) AGAINST STANDARD AND MULTIRESISTANT MICRO-ORGANISMS

KEY WORDS:

Antifungal agent; Efflux pump; MDR; Opportunistic infection; Pichia kudriavzevii.

PAGES: 46
BIG AREA: Ciências Biológicas
AREA: Bioquímica
SUMMARY:

 Fungal and bacterial infections have gained prominence due to their increasingly high level of resistance to antibiotics, so that the search for new pharmacological targets and antimicrobial substances is a necessity, while these microorganisms of clinical interest have excelled by surviving antibiotic therapy with the most varied antimicrobial drugs, many of which are already minimal because they can no longer sensitize any pathogenic strain. The aim of this thesis was to evaluate the antifungal and antibacterial potential of a lectin from Canavalia gladiata (CGL). The fine flour of C. gladiata seeds was extracted in 0.15 M NaCl under constant stirring for 4 hours. After centrifugation (4,000/4 °C/10 min), the supernatant was subjected to affinity chromatography (Sephadex G-50). The material was dialyzed and lyophilized. The fungal strains used were Candida albicans (CA INCQS 40006), Candida tropicalis (CT URM 4262) and Pichia kudriavzevii (PK INCQS 40095), while the bacterial strains were multidrug-resistant Staphylococcus aureus 10 and Escherichia coli 06, as well as S. aureus strains carrying NorA and MepA efflux pumps. The mean inhibitory concentration (IC50), the minimum fungicidal concentration (MFC) and the combined activity with fluconazole (FCZ) were determined using the broth microdilution method, and the analysis of the morphological transitions of the fungi was carried out by subculture in Petri dishes and moist chambers. The antibacterial tests consisted of performing the minimum inhibitory concentration and testing the direct and combined effect with the antibiotics norfloxacin, ciprofloxacin, gentamicin and ampicillin. FCZ reduced the population of all three strains tested, with IC50 ranging from 9.77 to 279.7 µg/mL. CGL did not show direct activity against any of the strains, however, when combined with fluconazole, it showed fungal inhibition of 128, 1 and 16 µg/mL for C. albicans, C. tropicalis and P. kudriavzevii, respectively. Among the CGL +FCZ combinations, the most significant inhibition was against the PK INCQS 40095 strain, which showed an inhibition of 82.7%. Fluconazole completely inhibited the morphological transition in CT URM 4262. CGL also had an effect against this strain, although it was less significant. LCG partially affected morphology (yeast/hyphae), although it had no direct effect, the lectin ended up modulating fluconazole, improving the effects of the drug and reducing its initial concentration. CGL had no direct effect against the bacteria (1024 µg/mL), however it reduced the MIC of the antibiotics norfloxacin (S. aureus 10) and ciprofloxacin (S. aureus K2068), demonstrating a combined effect with these quinolones. CGL therefore has potential antifungal activity and against gram-positive bacteria, by modifying the action of antibiotics.

COMMITTEE MEMBERS:
Presidente - FRANCISCO NASCIMENTO PEREIRA JUNIOR
Interna - JACQUELINE COSMO ANDRADE PINHEIRO
Externa à Instituição - JANAÍNA ESMERALDO ROCHA - UECE
Externa à Instituição - MARIA KAROLLYNA DO NASCIMENTO SILVA LEANDRO - URCA