Isolation and characterization of free-living amoebae predating on Acinetobacter baumannii and Klebsiella pneumoniae. Free-living amoebae predating on MDR pathogens

The objective of the study was to test the resistance of human pathogens to unaltered environmental free-living amoebae. From an open-air composting site, we recovered over a hundred amoebae able to feed on Acinetobacter baumannii and Klebsiella pneumoniae. Identification of amoebae was conducted by PCR amplification and sequencing of a 650 bp fragment of the 18S small subunit ribosomal RNA (SSU-rRNA) region. In a standardized and quantitative assay for predation, the isolated amoebae showed a broad predation spectrum, killing clinical isolates of A. baumannii, K. pneumoniae, Pseudomonas aeruginosa and Staphylococcus aureus. The isolated amoebae are capable of feeding on highly virulent carbapenem-resistant or methicillin-resistant clinical isolates. In conclusion, the natural environment is a rich source of amoebae with broad-spectrum bactericidal activities, including against antibiotic resistant isolates.