In 2020, the Centers for Disease Control and Prevention (CDC) estimated that over 2.8 million people in the United States had been diagnosed with drug-resistant infections resulting in an estimated 35,000 deaths. According to the World Health Organization, mortality is about 700,000 people a year, and this is expected to increase to 10 million a year by 2050, at the cost of 100 billion dollars annually. Bacteria have developed strategies to resist most current antibiotics, making it difficult to find safe, effective antibiotic alternatives. Many animals have evolved their own antimicrobial factors, especially invertebrates. Antimicrobial activity has been shown to exist in the central nervous system of the medicinal leech. By working with the genomic library of Hirudo medicinalis, we found a gene family associated with earthworms, initially identified in Lumbricus rebellus. Molecular and microbiological techniques were employed to confirm the existence of antibacterial activity, specific for Gram-positive and Gram-negative bacteria, from different tissues of Hirudo medicinalis. We show a protein extract with antimicrobial properties, where a family of 4 lumbricin-like peptides are the leading player in this family of antibiotics. However, each peptide presents less antibacterial activity individually against marine bacteria than the complete protein extract.
