Antibacterial and antibiofilm activities of pyocins produced by Pseudomonas aeruginosa against gram-negative bacteria: a systematic review (2015-2025).

BACKGROUND: Antimicrobial resistance among Gram-negative bacteria, particularly Pseudomonas aeruginosa, Escherichia coli, Klebsiella pneumoniae, and Acinetobacter baumannii, has reduced the effectiveness of conventional antibiotics. Biofilm formation further increases bacterial tolerance and exacerbates resistance to multiple antibiotics. Pyocins, bacteriocins produced by P. aeruginosa, are emerging as promising targeted antibacterial and antibiofilm agents. However, there is no comprehensive systematic literature synthesis of pyocin extraction, characterization, antibacterial, and antibiofilm efficacy against a wide range of Gram-negative biofilm-forming pathogens. OBJECTIVES: To systematically evaluate evidence on the extraction, purification, characterization, antibacterial activity, antibiofilm efficacy, and resistance mechanisms of pyocins against Gram-negative bacteria. METHODS: This review followed PRISMA 2020 guidelines and was registered in PROSPERO (ID: CRD420251064333). PubMed, Scopus, Web of Science, and CINAHL databases were searched for studies published between January 2015 and June 2025. Eligible studies included in vitro and preclinical investigations of S-, R-, F-type, or recombinant pyocins. Data on antibacterial activity and antibiofilm outcomes were extracted. Risk of bias was assessed using an adapted ROBINS-E framework. Findings were synthesized narratively. RESULTS: A total of 191 records were identified; 137 were screened after duplicate removal, and 7 studies met the inclusion criteria. Pyocins demonstrated strong antibacterial activity against P. aeruginosa, with minimum inhibitory concentration values as low as 0.003 μg/mL. Antibiofilm effects ranged from 48 to 84% reduction, with enhanced activity when combined with enzymes, particularly glycoside hydrolases. Mechanisms of action included membrane depolarization, pore formation, and receptor-mediated uptake. Resistance mechanisms involved lipopolysaccharide modification, receptor mutation, and immunity proteins. Overall risk of bias was low to moderate. CONCLUSION: Pyocins exhibit potent antibacterial and antibiofilm activity and represent promising alternatives to conventional antibiotics. However, standardized methodologies, in vivo validation, and clinical studies are needed to support their therapeutic application.