The rapid increase of plant diseases caused by bacterial phytopathogens calls for an urgent search for new antibacterials. Antimicrobial compounds of natural origin stand up as frontiers in the attempts of the antibiotic overuse replacement. With this in mind, the Hermetia illucens (H. illucens) larvae have recently gained attention as a promising approach to fulfill this need. This study aimed to isolate the active constituents of H. illucens larvae fat and to estimate its antimicrobial capacity. We discovered the best composition of extracting solution retaining the pronounced antimicrobial activity of the extract. Using gas chromatography-mass spectrometry (GC-MS), we identified the unique natural array of fatty acids as the major constituents of the acidified water-methanol extract (AWME) as having new antimicrobial potency. In standard turbidimetric assay, the minimum inhibitory concentration (MIC) of the AWME was 0.78 mg/mL after 24 h of incubation for all five tested phytopathogenic bacteria strains: Pantoea agglomerans, Xanthomonas campestris, Pectobacterium carotovorum subsp. carotovorum, Pectobacterium atrosepticum, and Dickeya solani. The minimum bactericidal concentration (MBC) ranged from 0.78 to 1.56 mg/mL against all tested strains after 24 h of incubation. The inhibition zone size of AWME (INZ) at 50 mg/mL concentration was in the range 12.2 ± 0.56 to 19.0 ± 0.28 mm, while zone size for the positive control (penicillin-streptomycin) (5000 IU/mL–5000 µg/mL) was in the scale of 20.63 ± 0.53 to 24.0 ± 0.35 mm as revealed by standard disk diffusion assay. For the first time, our findings indicated the substantial antibacterial potential of AWME of H. illucens larvae fat against these actual phytopathogens, thus paving the way for further research to determine the mechanism of action in crop protection.

Aeromonas spp. cause many diseases in aquaculture habitats. Hermetia illucens (Hi) larvae were used as feed-in aquacultures and in eradicating pathogenic fish bacteria. In the present study, we applied consecutive extractions of the same biomass of BSFL fat using the acidic water–methanol solution. The major constituents of the sequential extracts (SEs) were free fatty acids (FFAs), and fatty acids derivatives as identified by gas chromatography spectrometry (GC-MS). Our improved procedure enabled gradual enrichment in the unsaturated fatty acids (USFAs) content in our SEs. The present study aimed to compare the composition and antimicrobial properties of SEs. Among actual fish pathogens, A. hydrophila and A. salmonicida demonstrated multiple drug resistance (MDR) against different recommended standard antibiotics: A. salmonicida was resistant to six, while A. hydrophila was resistant to four antibiotics from ten used in the present study. For the first time, we demonstrated the high dose-dependent antibacterial activity of each SE against Aeromonas spp., especially MDR A. salmonicida. The bacteriostatic and bactericidal (MIC/MBC) activity of SEs was significantly enhanced through the sequential extractions. The third sequential extract (AWME3) possessed the highest activity against Aeromonas spp.: inhibition zone diameters were in the range (21.47 ± 0.14–20.83 ± 0.22 mm) at a concentration of 40 mg/mL, MIC values ranged between 0.09 and 0.38 mg/mL for A. hydrophila and A. salmonicida, respectively. AWME3 MBC values recorded 0.19 and 0.38 mg/mL, while MIC₅₀ values were 0.065 ± 0.004 and 0.22 ± 0.005 mg/mL against A. hydrophila and A. salmonicida, respectively. Thus, the larvae fat from Hermitia illucens may serve as an excellent reservoir of bioactive molecules with good capacity to eradicate the multidrug-resistant bacteria, having promising potential for practical application in the aquaculture field.

Hermetia illucens (HI) is a promising insect that widely employed as a sustainable source of food and has been recently used as a successful antimicrobial agent. Fatty acids extracted sequentially from HI larvae fight against MDR nosocomial pathogenic bacteria such as Staphylococcus aureus. This strain is resistant to various antibiotics, causing many issues and deaths in healthcare sectors. The present study aimed to elucidate the mechanism of bactericidal efficacy of fatty acids (FAs) in HI larvae fat against S. aureus ATCC 55804 strain. The disk diffusion assay, minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and half of the minimum inhibitory concentration (MIC50) applied in this study, proved the antimicrobial activity of fatty acids. The mechanism of FAs action was evaluated by several approaches, including inhibition of the bacterial growth curves and salt tolerance assays, scanning electron (SEM) and transmission electron (TEM) microscopies. S. aureus ATCC 55804 was resistant to 30% out of ten tested antibiotics belonging to different classes. In addition, microscopic observations showed the inhibitory effect of acidic water methanol extract (AWME3) by targeting of the S. aureus ATCC 55804 cell membrane and causing the considerable morphological alterations on the bacterial wall and destruction its cytoplasmic contents leading to the cellular content release and cell death. This study revealed the potential efficacy of AWME3 as a novel therapeutic antibacterial agent effective against resistant nosocomial bacterial pathogens.

IN VITRO grown potato cultivars shoots were used to understand….. how polyvinyl pyrrolidone (PVP) and three levels of potassiuminteract with two levels of salinity to determine Na+ and K+ contents,and antioxidant enzyme activities leading to control survival,multiplication and growth of cultured plant shoots. Explant survivaland the number of regenerants/explant decreased with the increase of NaClconcentration but increased K+ content of the culture medium from 20mM to 30 mM improved explants survival frequency and the growthparameters estimated under relatively high salt stress (80 mM NaCl) inboth cultivars. Also, number of regenerants was influenced by K+ levelwhere it was higher in medium containing 40 mM NaCl and 30 mMK+ than other cultured on the same NaCl concentration with 20 mMK+. The positive effect of 30 mM K+ on the previous parameters wasassociated with increase shoot K+ content leading to decrease Na+/K+ratio and increase of some antioxidant enzymes (SOD, POX and CATin Agria or SOD, POX and APX in Hermes) activity, especially underrelatively high salt stress. PVP application increased K+ content andactivities of some antioxidant enzymes (CAT and APX) but decreasedNa+/K+ ratio of shoots subjected to relatively high salt stress in Agriabut under both salt stresses in Hermes. Consequently, sufficientpotassium supply was necessary to conserve low Na+/K+ ratio andefficient scavenging system by antioxidant agent (PVP) application orincrease the endogenous antioxidant enzymes activities leading tominimize the negative effect of salt stress on in vitro grown potato.

Hypervirulent mucoviscus Klebsiella pneumoniae (hvKp) is rapidly emerging as opportunistic pathogens that have a global impact leading to a significant increase in mortality rates among clinical patients. Anti-virulence strategies that target bacterial adhesion and biofilm formation, proposed as alternatives to antibiotic treatments for reducing the rapid emergence of bacterial resistance. The main objective of this study was to examine the efficacy of fatty acid-enriched extract (AWME3) derived from the fat of Hermetia illucens fly larvae to combat biofilms formed by multidrug-resistant (MDR) and highly virulent hvKp pathogens. To reach these goals we used crystal violet (CV) and ethidium bromide (EtBr) assays on the mature biofilms of K. pneumoniae KPi1627, KPM9 and ATCC BAA-2473 strains. We found that exposure of hvKp strains to AWME3 at a concentration of 500 µg/mL (corresponding to 2× minimum inhibitory concentration, MIC) significantly affects the membrane permeability (p < 0.0001), causing serious disturbances and changes in the composition of membrane phospholipids, as confirmed by the detected increase in CV and EtBr uptake by 70 and 80%, respectively, compared to the control group. We used scanning electron microscopy (SEM) as a direct microscopic method to collect evidence of bactericidal action of AWME3 extract and the destruction of hvKp biofilms. In conclusion, our study demonstrates the exceptional capability of natural AWME3 extract, enriched with a unique combination of fatty acids, to effectively eliminate biofilms formed by highly drug-resistant and highly virulent pathogens K. pneumoniae (hvKp). Our results highlight the potential to control and minimize the rapid emergence of bacterial resistance by treating biofilm-associated infections caused by hvK pathogens with AWME3.