Banca de DEFESA: DÁRCIO LUIZ DE SOUSA JÚNIOR

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
STUDENT : DÁRCIO LUIZ DE SOUSA JÚNIOR
DATE: 07/04/2025
TIME: 14:01
LOCAL: CCAB
TITLE:

ANTIMICROBIAL AND ANTIBIOTIC POTENTIALIZING ACTIVITIES OF THE LECTIN OF Canavalia gladiata (LCG)

KEY WORDS:

Antimicrobial agent; Bacterial multidrug resistance; Efflux pump; Opportunistic infection; Pichia kudriavzevii.

PAGES: 48
BIG AREA: Ciências Biológicas
AREA: Bioquímica
SUMMARY:

Fungal and bacterial infections are gaining prominence due to the increasingly high level of antibiotic resistance that these microorganisms display. The search for new pharmacological targets and antimicrobial substances is therefore a necessity. Among these substances, the species Canavalia gladiata is a legume that, in addition to producing secondary metabolites, also synthesizes a large amount of lectins, carbohydrate-binding proteins that have, among many functions, antimicrobial protection in the plant. The aim of this thesis was to evaluate the antifungal and antibacterial potential of a lectin from C. 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 Escherichia coli ATCC 10536 and Staphylococcus aureus ATCC 25923 standards and S. aureus 10 and multidrug-resistant E. coli 06, as well as strains of S. aureus carrying NorA (S. aureus 1199B) and MepA (S. aureus K2068) efflux pumps. The mean inhibitory concentration (IC50), minimum fungicidal concentration (FCM), minimum inhibitory concentration (MIC) and combined activity with fluconazole (FCZ) were determined using the broth microdilution method, and analysis of the morphological transitions of the fungi was carried out by subculturing in Petri dishes and moist chambers. The antibacterial tests consisted of determining the minimum inhibitory concentration and testing the direct and combined effect with the antibiotics norfloxacin, ciprofloxacin, gentamicin and ampicillin, also using the microdilution method. FCZ reduced yeast growth in the three strains tested, with IC50 ranging from 9.77 to 279.7 µg/mL. CGL did not show direct activity against any of the fungal strains, however, when combined with fluconazole, it showed growth inhibition at concentrations of 1, 16 and 128 µg/mL for C. tropicalis, P. kudriavzevii and C. albicans, 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, partially affecting morphology (yeast/hyphae). CGL had no direct effect against the bacteria analyzed, with a MIC ≥ 1024 µg/mL, however it reduced the MIC of the antibiotics norfloxacin and ciprofloxacin against S. aureus 10 and S. aureus K2068 respectively, demonstrating a combined and potentiating effect of these quinolones.  The results of ampicillin+sulbactam in multidrug-resistant bacterial strains suggest inhibition of the β-lactamase enzyme, but CGL did not show significant results. In the two strains carrying the efflux pump, the MIC was reduced by the standard inhibitors, but the combination with CGL did not determine the inhibition of the efflux proteins. CGL therefore has potential antimicrobial activity on the fungal and bacterial strains analyzed, but in an indirect way, i.e. by modifying the action of antibiotics, potentiating the previously ineffective effect.

COMMITTEE MEMBERS:
Externa à Instituição - CRISTINA RODRIGUES DOS SANTOS BARBOSA - URCA
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