Study: Marijuana Extract Shows Strong Antibacterial Potential Against Fish Pathogens

A study published this month by the peer-reviewed journal Frontiers in Veterinary Science found that leaf extracts from marijuana may help fight bacterial infections in fish by limiting bacterial growth, disrupting biofilms and interfering with quorum sensing, a communication process bacteria use to coordinate harmful activity. The research was conducted by scientists from the University of South Africa and Marondera University of Agricultural Sciences and Technology. According to the study, the findings suggest marijuana leaf extracts could eventually have potential as protective feed additives in fish production, although researchers say more study is needed.

The team examined acetone extracts from Cannabis “Gorilla Glue 1” against several fish pathogens, focusing on antibacterial, anti-biofilm, anti-quorum-sensing and cytotoxic activity. Biofilms are especially difficult to treat because they help bacteria stick to surfaces and shield themselves from conventional antibiotics, making infections harder to control.

Among the extracts tested, one treatment with 0.36 g nitrogen, 0.12 g phosphorus and 0 g potassium produced the lowest minimum inhibitory concentration, 0.02 mg/mL, against Edwardsiella tarda and Pseudomonas fluorescens. That same treatment also showed the highest selectivity index against Vero kidney cells, which researchers said indicated the most favorable safety profile among the extracts they studied.

The study found that all solvent extracts were able to either prevent or disrupt biofilm formation. One treatment in particular, using 0.36 g nitrogen, 0.06 g phosphorus and 0.12 g potassium, produced more than 50% anti-biofilm inhibition against every pathogen tested. That same treatment also showed the strongest anti-quorum-sensing activity, inhibiting violacein production by 98.61% at 1.25 mg/mL.

Researchers said most of the extracts were not cytotoxic to Vero cells, although a few treatments showed moderate or high toxicity. Even so, the overall findings indicate that marijuana leaf extracts may offer a promising natural tool for reducing microbial infections in aquaculture. The researchers say the results provide support for additional research into whether these extracts can be developed into safe and effective feed additives for fish farming.

You can find the full text of this study by clicking here. The study’s full abstract can be found below.

The resilience of biofilms makes it challenging to treat bacterial infections using conventional antibiotics. The study aimed to assess the antibacterial, anti-biofilm, anti-quorum-sensing, and cytotoxic activities of acetone extracts of Cannabis “Gorilla Glue 1” against fish pathogens. Antibacterial activity was determined using the two-fold serial microdilution method, while anti-biofilm activity was assessed using a modified crystal violet staining in vitro assay. Anti-quorum-sensing activity was evaluated via inhibition of violacein production in Chromobacterium violaceum (ATCC 12472). Cytotoxicity was assessed using a colorimetric assay against Vero kidney cells. Solvent extracts from treatment 0.36 g N; 0.12 g P; 0 g K showed the lowest minimum inhibitory concentration (MIC) value (0.02 mg/mL) against Edwardsiella tarda (ATCC 15947) and Pseudomonas fluorescens (ATCC 13525) compared with other treatments. All tested solvent extracts demonstrated the ability to prevent or disrupt biofilm formation; however, treatment 0.36 g N; 0.06 g P; 0.12 g K showed consistent anti-biofilm activity (>50% inhibition) against all tested pathogens. All solvent extract treatments exhibited comparable anti-quorum-sensing activity, while treatment 0.36 g N; 0.06 g P; 0.12 g K demonstrated the highest inhibition of violacein production (98.61% at 1.25 mg/mL). Most solvent extracts were non-cytotoxic to Vero cells, with LC50 values >0.1 mg/mL, except treatment 0 g N; 0.24 g P; 0 g K, which showed high cytotoxicity (LC50 = 0.04 mg/mL). Treatments 0.36 g N; 0.12 g P; 0 g K, 0 g N; 0.36 g P; 0.6 g K, and 0 g N; 0 g P; 0 g K exhibited moderate toxicity (LC50 = 0.06 mg/mL). Treatment 0.36 g N; 0.12 g P; 0 g K displayed the highest selectivity index (3.00) against Vero cells, indicating the most favorable safety profile among the extracts investigated. Leaf extracts of Cannabis exhibited useful bioactivities coupled with low cytotoxicity, providing impetus for further studies on their potential development as protective feed additives against microbial infections in fish production.