ANTIBACTERIAL ACTIVITY AND TOXICITY OF THE ETHANOLIC EXTRACT OF Eugenia uniflora L. LEAVES ON Pseudomonas aeruginosa

BOBADILLA, F.; NOVOSAK MG; WINNIK, D.; KACHUK, A.; LACZESKI, M.; QUIROGA, M.

Journal of microbiology, biotechnology and food sciences

Faculty of Biotechnology and Food Sciences, Nitra, Eslovaquia

Año: 2018 vol. 8 p. 842 - 846

1338-5178

Pseudomonas aeruginosa is one of the main causes of nosocomial infections worldwide, with great potential for multi-resistance development. The World Health Organization (WHO) lists antimicrobial resistance as an emerging public health problem that makes new therapies an extremely urgent issue. Natural products provide unlimited opportunities for the discovery of new drugs. Eugenia uniflora L. (commonly ?pitanga?) is a small tree native to subtropical America that is attributed, among others, antimicrobial properties. The aim of this work was to study the antibacterial capacity of the ethanolic leaf extract of Eugenia uniflora L. on Pseudomonas aeruginosa, its possible synergistic action with antibiotics used in the treatment of infections caused by this microorganism and to carry out general toxicity tests using the crustacean Artemia saline. The extract was obtained dried by digestion at 37 °C. The strain P. aeruginosa PAO1 was used in all the trials and three clinical isolations of this species were added for the determination of the Minimum Inhibitory Concentration (MIC) and Minimum Bactericide Concentration (MBC). The antibacterial activity of the extract was established by disc diffusion techniques, MIC, MBC, Time-killing curve and resistance analysis by broth dilution. Its interaction with commercial antibiotics meropenem (MER), piperacillin (PIP), Ceftazidime (CAZ), ciprofloxacin (CIP), amikacin (AMK) and colistin (COL) was studied. The extract had a Minimum Inhibitory Dose (MID) of 0.5 mg d-1. At different doses tested, the inhibition diameters were found in a range between 6 (0.25 mg d-1) and 13.7 mm (8 mg d-1). The MIC for P. aeruginosa PAO1 was 1.33 mg mL-1 and for the clinical isolations tested was 0.83 mg mL-1. CBM values showed wider range amplitude, between 8 and 16 mg mL-1 for P. aeruginosa PAO1 (mean 13.33 mg mL-1) and from 1 to 16 mg mL-1 for clinical isolations (mean 8.33 mg mL-1). The MBC/MIC ratio (MICI) had an average of 10.67 for P. aeruginosa PAO1 and 8.67 for the clinical isolations, which qualify the action of the extract as bacteriostatic. The Time-killing curve showed that at a concentration of 8 mg mL-1 the count remains constant, similar to the initial inoculum, over time. The total loss of viability of the bacteria occurs at 24 h to 16 mg mL-1 and at 8 h to 32 mg mL-1. The combination of the MER with the extract results in a decrease in its inhibitory action on P. aeruginosa PAO1. Meanwhile, the combination with PIP or CAZ produces a synergistic action. For CIP, AMK and COL the combination is indifferent. The LC50 obtained using A. salina was 0.61 mg mL-1; indicating that the extract has a moderate toxity.