The Sydney rock oyster is emerging as a groundbreaking contributor to the fight against antimicrobial resistance, thanks to its powerful Antimicrobial Peptide and Protein (AMPP). Researchers have identified that the AMPP from the oyster's hemolymph exhibits potent antibacterial and antibiofilm activities, particularly against challenging respiratory pathogens. This discovery marks a significant step forward in combating existing antimicrobial resistance and potentially reducing its evolutionary rate.
Recent studies tested the oyster AMPP against three clinical strains of Streptococcus pneumoniae and six other respiratory pathogens, demonstrating specific activity toward Streptococcus species. Notably, the AMPP also showed effectiveness against notorious infections caused by golden staph (Staphylococcus aureus) and Pseudomonas aeruginosa, without exhibiting toxic effects on human lung cells. This positions the Sydney rock oyster's AMPP as a promising candidate for further exploration in antimicrobial therapies.
The innovative approach of combining oyster-derived AMPPs with conventional antibiotics such as ampicillin, gentamicin, trimethoprim, and ciprofloxacin has shown remarkable results. At low concentrations, these antibiotic combinations with AMPP improved efficacy between 2- and 32-fold. This synergy not only enhances antibiotic effectiveness but also reduces overall reliance on antibiotics, providing a dual benefit in managing resistant bacterial strains.
“AMPPs are an exciting area with a lot of potential,” said Shauna McGillivray, PhD.
“They are by themselves very potent but, as has been noted in multiple studies, they can also synergize with existing antibiotics, thereby improving efficacy of antibiotics, even in some cases to antibiotics to which there are high levels of resistance,” she added.
The Sydney rock oyster's AMPP exhibits a remarkable capacity to penetrate already-formed biofilms in Streptococcus species and prevent their formation altogether. This capability is critical because biofilms often serve as protective barriers for bacteria against conventional treatments. Additionally, the development of resistance to oyster-derived AMPPs is generally low compared to that observed with standard antibiotics.
"On its own, the oyster AMPP showed specific activity toward the Streptococcus species," stated Kirsten Benkendorff.
“I thought mollusks must have some strong antimicrobial compounds in their hemolymph (blood) to compensate, especially filter-feeding mollusks like oysters that are constantly pumping bacteria through their gills,” Benkendorff explained.
To produce sufficient quantities of these promising AMPPs for preclinical and clinical trials, researchers highlight the potential of large-scale aquaculture production. The Sydney rock oyster's ability to be cultivated widely supports this endeavor, ensuring that enough material will be available for extensive testing and potential therapeutic applications.
“The Sydney rock oyster can be produced on a large scale by aquaculture, so it will be possible to produce sufficient quantities for preclinical and clinical trials,” Benkendorff confirmed.
Despite these promising findings, scientists recognize the need for further studies to explore the potential of cystatins, the most abundant AMPPs present in the hemolymph protein extract (HPE), particularly when used with antibiotics. This ongoing research promises to shed more light on their capabilities and broaden the spectrum of effective antimicrobial agents.
“Only a few proteins are possible AMPP candidates based on their presence in active fractions,” noted Benkendorff.
However, experts also caution against complacency. While the resistance levels are low, they are not nonexistent.
“Low resistance does not mean no resistance, and there is evidence that bacteria can evolve resistance to AMPPs,” McGillivray warned.
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