Thieme, L. | bioRxiv Science

bioRxiv2025

Galleria mellonella model for studying Gram-positive bacterial implant biofilms

Implant-associated biofilm infections, particularly those caused by Staphylococcus aureus and Enterococcus faecalis, present significant challenges in clinical settings, often necessitating surgical removal. This study investigates the potential of the invertebrate model Galleria mellonella for evaluating biofilm formation of S. aureus and E. faecalis clinical isolates, the leading causes of implant-associated infections. Utilizing expanded polytetrafluoroethylene (ePTFE) sutures as a surrogate for cardiac implants, we employed two biofilm formation methodologies reflecting the two main routes of implant infections: in vivo biofilm development within larvae mimicking hematogenous spread and pre-formed biofilm transplantation mimicking contamination during surgery. Scanning electron microscopy revealed complex biofilm structures for the biofilm formed inside of the larvae on implant, closely mimicking clinical conditions. Antibiotic treatments with vancomycin and rifampicin demonstrated significant reductions in bacterial biofilms, proving highly effective. The study highlights the G. mellonella models potential for preclinical biofilm research, offering a cost-effective and ethical alternative to vertebrate models while providing valuable insights into biofilm-related infections and their treatment.

microbiology↗

bioRxiv2023

Bacteriophage-mediated decolonization of Enterobacteriaceae in a novel Galleria mellonella gut colonization model

PurposeGalleria mellonella larvae have emerged as an invertebrate model for studying bacterial pathogenesis and novel therapeutic options due to ethical concerns associated with the use of mammalian models such as mice. The benefits of using G. mellonella larvae include a less complex microbiome in the gut, making it suitable for gut colonization studies. The intestinal colonization of Klebsiella pneumoniae (Kp) and Escherichia coli (Ec), two of the most antibiotic-resistant bacteria on the World Health Organizations (WHO) priority list, plays a key role in the spread of antibiotic resistance. Bacteriophage therapy is emerging as a promising alternative for antibiotic-resistant bacteria due to its ability to specifically target and infect bacterial hosts, making it suitable for gut decontamination. This study aimed to establish a novel Enterobacteriaceae G. mellonella larvae gut colonization model and compare the efficacy of conventional antibiotic treatment with a one-time phage cocktail in decolonizing the gut. ApproachLarvae were force-fed with different concentrations of bacterial doses of K. pneumoniae and E. coli at 0 h, 24 h, and 48 h, followed by survival monitoring at 24 h intervals. After 48 h and 120 h of the last force feed, the colony forming unit (CFU) count in the gut was evaluated. After successful colonization, larvae were one-time force-fed with either a 107 PFU/larvae bacteriophage cocktail or with ciprofloxacin 4 mg/L or meropenem 2 mg/L. After 24 h post phage feeding, CFU counts were determined. Main findingsThree bacterial doses of 106 CFU/larvae led to a stable gut colonization in the larvae gut regardless of the K. pneumoniae and E. coli strains. Bacteriophage force-feeding reduced bacterial colonization by 4 log10 CFU/larvae whereas antibiotic treatment led to a 2 log10 CFU/larvae reduction compared to the control. The novel alternative G. mellonella model for gut colonization studies can be used for proof-of-concept studies, reducing or even obviating the number of follow-up experiments in vertebrate models.

microbiology↗