2581. An Invertebrate Model to Study Gut Microbiome Dysbiosis

BACKGROUND: Antimicrobials disrupt the gut microbiota by reducing gut microbiome diversity and quantity. Galleria mellonella provides an invertebrate model that is inexpensive, easy to maintain, and does not require specialized equipment. This study investigated the feasibility of using G. mellonella as an in vivo model to evaluate the effect of different antimicrobials on gut microbiota. METHODS: To determine baseline gut microbiota composition, the gut contents of G. mellonella were extracted and genomic DNA underwent shotgun meta-genomic sequencing. To determine the effect of infection and antibiotic use, 30 larvae were injected (left proleg) with ~1 × 10(5) colony-forming unit (cfu) of methicillin-resistant Staphylococcus aureus (MRSA) and were randomized 1:1:1 to treatment with vancomycin (20 mg/kg) or a natural antimicrobial (Nigella sativa seed oil, 70 mg/kg; NS oil), or a combination. The larvae were kept at 37°C post-infection and monitored daily for 72 hours for activity, extent of cocoon formation/growth, melanization, and survival. Two larvae from each group were randomly selected and homogenized with PBS as controls. After 24 hours of incubation, gut contents were extracted and plated for MRSA and Enterococcus cfu counts. RESULTS: Metagenomics analysis showed the gut microbiota composition of G. mellonella larvae was dominated by a subset of closely-related Enterococcus species. After 24 hours of exposure, mean Enterococcus counts were 4 × 10(3) cfu in the vancomycin arm and 6.2 × 10(4) cfu in the NS oil arm. Mean MRSA counts were 3.3 × 10(5) cfu in vancomycin arm and 1.5 × 10(4) cfu in NS oil arm. The combination of vancomycin and NS oil had higher Enterococcus counts than the vancomycin alone arm (6.3 × 10(4) cfu vs. 4 × 10(3) cfu, respectively), suggesting that NS oil may have a role in protecting the gut microbiota. CONCLUSION: This study provides preliminary evidence to support the potential use of G. mellonella to assess the in vivo effect of a natural and synthetic antimicrobial on the gut microbiota. DISCLOSURES: All authors: No reported disclosures.