THE INHIBITORY EFFECT OF MONOTERPENES AGAINST ESBL-PRODUCING KLEBSIELLA PNEUMONIAE

Abstract

Introduction: Klebsiella pneumoniae is a Gram-negative bacillus of the Enterobacteriaceae family which may infect primarily the respiratory and urinary tracts. Due to the uncontrolled growth of self-medication, various microorganisms have been developing resistance mechanisms with a greater frequency, thus making infections increasingly difficult to treat. Further research is then required to develop new, more effective treatment options. Several natural products have been studied, such as essential oils and monoterpenes, which have shown promising activity against selected microorganisms. Objective: This study aimed to evaluate the antibacterial activity of the phytochemicals citral, citronellal and citronellol against K. pneumoniae strains producing extended-spectrum beta-lactamases (ESBL), and to determine the minimum inhibitory concentration (MIC) of these monoterpenes. Material and Methods: A serial microdilution technique was performed to test the samples at concentrations of 2048, 1024, 512, 256, 128, 64 and 32 μg/mL. Mueller Hinton broth was employed as the culture medium, and the last column was used for the control of microbial growth and medium sterility. The experiments were carried out in triplicate and incubated at 37 C˚ ± 2 C˚ for 24 hours, followed by visual reading. Results: The phytochemicals citral, citronellal and citronellol did not inhibit the growth of K. pneumonia strains under the conditions and concentrations tested. Conclusion: The monoterpenes presented herein showed no antibacterial activity against the tested strains. DESCRIPTORS: Antimicrobials; Terpenes; Gram-negative bacteria.