Lactoferrin is an antibiofilm adjuvant for Cefazolin based treatment of prosthetic joint infections

Abstract

Lactoferrin (LF) is an immunomodulatory protein known to support β-lactam antibiotics. It has many reported functions, including iron chelation activity, and LF and LF fragments have been reported to have both antimicrobial and antibiofilm activity. This thesis investigated the potential of LF to support the prevention and eradication of biofilm-based chronic infection by β-lactam cefazolin in an orthopaedic setting, and rule out simple iron chelation as its mode of action. Staphylococcus aureus biofilm was used to determine appropriate dosages of LF and cefazolin for in vivo testing of prevention and eradication of chronic prosthetic joint infection (PJI). A novel biofilm inoculation system was developed and optimized to inoculate a four-day small animal model of chronic PJI. It was found that iron-limited native lactoferrin (native LF) is very effective at limiting the proliferation of planktonic S. aureus and enhances the bactericidal activity of cefazolin. In contrast, hololactoferrin (holoLF) may actually enhance biofilm development on hardware. This thesis has shown that 100 μM native LF is an effective adjuvant to cefazolin for eradication of biofilm over a four-day period in vitro, and that this activity may be iron independent. In vivo, LF was found to shift the ratio of bacteria strongly adherent to weakly adherent to a prosthetic to favor weakly adherent cells at an estimated concentration of 3.3 to 33 μM native LF in the presence of cefazolin, thus making the bacteria more susceptible to bactericidal activity in a novel four-day rat model of chronic PJI. From this data, it was concluded that LF has potential as an antibiofilm therapeutic at concentrations approximately 10-times lower than its in vitro antibiofilm activity, that may be independent of antibiotic synergies shown by others, by reducing adherence of the biofilm to surfaces within the infection or by general disruption of the biofilm, regardless of iron status. Importantly, the concentrations of LF and method of delivery demonstrated to be effective against in vivo biofilm is yet to be optimized.