Novel Animal Model of Enterobacteria Pathogenicity, Virulence, and Amoxicillin—Biosurfactant Synergic Using Nsombé ( <i>Rhynchophorus phoenicis</i> Larvae)

Insect larvae are increasingly being employed as sophisticated infection models in the expanding field of pathogenic bacterial research. This innovative study aims to evaluate an alternative model for analyzing host-pathogen interactions and assessing the efficacy of antimicrobial treatments using the biological system of Rhynchophorus phoenicis larvae. Using PCR techniques targeting 16S rRNA, virulence genes encoding Type III secretion system (T3SS) components, and the Hsp60 gene, four major pathogenic Enterobacteriaceae were identified with 100% detection rates: Salmonella Typhimurium, Klebsiella pneumoniae, Enterobacter cloacae, and enteropathogenic Escherichia coli (EPEC). Virulence assessment revealed that injection of bacterial strains at a concentration of 10⁵ CFU/µL into R. phoenicis larvae was optimal for evaluating pathogenicity. Highly virulent strains-E. coli EPEC strain E2, K. pneumoniae K4, S. Typhimurium S4, and E. cloacae En2-caused significantly reduced larval survival, with bacterial loads in the hemolymph reaching up to 2.5 × 10⁶ CFU/µL. Treatment evaluation showed that the amoxicillin + biosurfactant combination was the most effective in prolonging larval survival across all time points. Survival rates peaked at 80% at 24 h and remained relatively high at up to 70% at 72 h for certain strains. In contrast, amoxicillin alone demonstrated variable and less sustained efficacy. These findings underscore the potential of R. phoenicis larvae as a valuable alternative model for exploring host-pathogen interactions and assessing the synergistic efficacy of combined antimicrobial treatments involving antibiotics and biosurfactants.