Analysis of Antimicrobial and Antibiofilm Activity of Human Milk Lactoferrin Compared to Bovine Lactoferrin against Multidrug Resistant and Susceptible <i>Acinetobacter baumannii</i> Clinical Isolates

Abstract

<i>Acinetobacter baumannii</i> is an opportunistic bacterial pathogen that causes severe infections in immunocompromised patients. The emergence of multi- and pan-drug resistant strains of <i>A. baumannii</i> from clinical sources has confounded treatment and enhanced morbidity and mortality associated with these infections. One way that <i>A. baumannii</i> circumnavigates environmental and antimicrobial challenge is by forming tertiary architectural structures of cells known as biofilms. Biofilm-inhibiting molecules could be deployed as a potential chemotherapeutic strategy to inhibit or disrupt <i>A. baumannii</i> biofilms and mitigate adverse outcomes due to infection. Lactoferrin is an innate immune glycoprotein produced in high concentrations in both human and bovine milk which has previously been shown to have antibacterial and antibiofilm activities. We sought to test lactoferrin against a bank of clinical isolates of <i>A. baumannii</i> to determine changes in bacterial growth or biofilm formation. Our results indicate that human lactoferrin has slightly more potent antibacterial activities than bovine lactoferrin against certain strains of <i>A. baumannii</i> and that these effects are associated with anatomical site of isolation. Additionally, we have shown that both bovine and human lactoferrin can inhibit <i>A. baumannii</i> biofilm formation and that these effects are associated with anatomical site of isolation and whether the strain forms robust or weak biofilms.