Presence and Role of Acanthamoeba in Wound Infections

Methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa are the main multi-drug resistant pathogens associated with deep wound infections which then may cause septicaemia. Treatment is problematic and re-infection is quite common. Free Living Amoebae (FLA), such as Acanthamoeba, are widely distributed in the environment and may also contaminate wounds. It is well known that Acanthamoeba feed on and protect bacteria. The role of Acanthamoeba in wound infections is not very well understood. It is possible that the presence of Acanthamoeba in wounds is one of the key factors for such re-infections. In this study, 140 wound swabs were collected to check for the presence of Acanthamoeba spp. Only one sample was positive for Acanthamoeba spp. Sequencing of the highly variable DF3 region of 18S rRNA gene for the sample showed that this isolate belongs to genotype T4. In addition, clinical isolates of MRSA and Pseudomonas from wound infections were used in this study. The results showed that MRSA and Pseudomonas were able to bind with, invade, survive and multiply inside Acanthamoeba species. One of the essential compounds for microorganisms to grow is iron. The role of iron chelators, including deferiprone and selected novel compounds based on hydroxyl pyridine moiety, was studied. Findings revealed that all novel iron chelators have an antimicrobial activity against both bacteria. In addition, all novel iron chelators were able to kill Acanthamoeba. Cytotoxic effects of MRSA, P. aeruginosa and Acanthamoeba were investigated using the KB epithelial cell line and mesenchymal stem cells (MSC) using a general caspase inhibitor. The results revealed that the ability of live bacteria to induce cell death was higher compared with heat-killed bacteria, bacteria conditioned medium (BCM) and Acanthamoeba conditioned media (CM). The exact trigger for the cell death in this study was not investigated but the relative contributions of apoptosis and necrosis were investigated using fluorescent technique, caspase inhibition and LDH assay. In conclusion, presence of Acanthamoeba in wounds could be the reason of prolong treatment and reinfection in wounds.