Antibiofilm Synergistic Activity of Streptomycin in Combination with Thymol-Loaded Poly (Lactic-co-glycolic Acid) Nanoparticles against Klebsiella pneumoniae Isolates

Abstract

Background. Thymol is an important component of essential oils found in the oil of thyme, is extracted mainly from Thymus vulgaris, and was shown to act synergistically with streptomycin against Klebsiella pneumoniae biofilms. Additionally, thymol could be encapsulated into poly (lactic-co-glycolic acid) (PLGA) nanoparticles to overcome issues related to its low water solubility and high volatility. The present study aimed to investigate the antibiofilm activity of thymol-loaded PLGA nanoparticles (Thy-NPs) alone and in combination with streptomycin against biofilms of K. pneumoniae isolates. Methods. The broth microdilution method was used to determine the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). The antibiofilm activities were determined by the safranin dye assay. The synergistic effect of Thy-NPs with streptomycin was assessed by the checkerboard method. The kinetic study of the biofilm biomass and time-kill assay were further performed. Results. Thy-NPs exhibited the highest antibacterial activity against K. pneumoniae isolates, with MIC values ranging from 1 to 8 µg/mL. Additionally, Thy-NPs showed the highest antibiofilm activity against K. pneumoniae isolates with minimal biofilm inhibitory concentration (MBIC) and minimal biofilm eradication concentration (MBEC) values ranging from 16 to 64 µg/mL and from 32 to 128 µg/Ml, respectively. The combination treatment combining Thy-NPs with streptomycin showed a synergistic effect against the inhibition of biofilm formation and eradication of biofilms of K. pneumoniae isolates with fractional inhibitory concentration index values ranging from 0.13 to 0.28. In addition, the MBIC and MBEC values of streptomycin against K. pneumoniae isolates were dramatically reduced (up to 128-fold) in combination with Thy-NPs, suggesting that Thy-NPs would enhance the antibiofilm activity of streptomycin. The biomass and time-kill kinetics analysis confirmed the observed synergistic interactions and showed the bactericidal activity of streptomycin in combination with Thy-NPs. Conclusions. Our results indicate that the synergistic bactericidal effect between streptomycin and Thy-NPs could be a promising approach in the control of biofilm-associated infections caused by K. pneumoniae.

Biofilm Formation and Phospholipase and Proteinase Production in Cryptococcus neoformans Clinical Isolates and Susceptibility towards Some Bioactive Natural Products

“…In addition, the MBEC values of natural products and antifungals were up to 8 times and 4 times higher than their MFC values, respectively. Tese results showed that the bioflm was more resistant to antimicrobial agents than planktonic cells, and this could be explained by the limited difusion of antimicrobial agents through the bioflm matrix or the lower growth rate of cells in the bioflm [6,36]. Tese results corroborated those reported earlier [14,24].…”

“…Te bioflm formation assay was performed using the microtiter plate method as previously described by Bisso et al with some modifcations [6]. Standard cultures (1.5 × 10 6 CFU/mL) were diluted 100-fold in SDB supplemented with 2% glucose.…”

“…C. neoformans grows as a bioflm. Bioflms are communities of aggregated microbial cells embedded in an extracellular matrix composed of water, polysaccharides, lipids, proteins, and extracellular DNA [6]. Bioflm formation confers increased resistance of cells inside bioflms to antimicrobials and hosts immune mechanisms compared with their planktonic cells [7].…”

Antibiotic Resistance Profile, Biofilm Formation Ability, and Virulence Factors Analysis of Three Staphylococcus spp. Isolates From Urine

“…The biofilm formation was measured at 570 nm optical density using a microplate reader (VERSA-max, USA). From the obtained optical density value, isolates were classified by their biofilm formation capacity as non-biofilm producers, low biofilm producers, moderate biofilm producers, or strong biofilm producers according to our previously described cut-off [ 20 ].…”

Antibiofilm Activity of Curcumin and Piperine and Their Synergistic Effects with Antifungals against Candida albicans Clinical Isolates

“…Previous studies report that curcumin is a promising anticandida compound of clinical interest [ 5 ]. Piperine is a naturally occurring alkaloid found in consumed species of black pepper ( Piper nigrum ) and long pepper ( Piper longum ) and has antimicrobial and antibiofilm activities against bacteria strains [ 6 , 7 ].…”