Bioluminescence and ¹⁹ F Magnetic Resonance Imaging Visualize the Efficacy of Lysostaphin Alone and in Combination with Oxacillin against Staphylococcus aureus in Murine Thigh and Catheter-Associated Infection Models

Abstract

Staphylococci are the leading cause of hospital-acquired infections worldwide. Increasingly, they resist antibiotic treatment owing to the development of multiple antibiotic resistance mechanisms in most strains. Therefore, the activity and efficacy of recombinant lysostaphin as a drug against this pathogen have been evaluated. Lysostaphin exerts high levels of activity against antibiotic-resistant strains of Staphylococcus aureus, including methicillin-resistant S. aureus (MRSA). The therapeutic value of lysostaphin has been analyzed in two different clinically relevant in vivo models, a catheter-associated infection model and a thigh infection model. We infected mice with luciferase-expressing S. aureus Xen 29, and the efficacies of lysostaphin, vancomycin, oxacillin, and combined lysostaphin-oxacillin were investigated by determining numbers of CFU, detecting bioluminescent signals, and measuring the accumulation of perfluorocarbon emulsion at the site of infection by 19 F magnetic resonance imaging. Lysostaphin treatment significantly reduced the bacterial burden in infected thigh muscles and, after systemic spreading from the catheter, in inner organs. The efficiency of lysostaphin treatment was even more pronounced in combinatorial therapy with oxacillin. These results suggest that recombinant lysostaphin may have potential as an anti-S. aureus drug worthy of further clinical development. In addition, both imaging technologies demonstrated efficacy patterns similar to that of CFU determination, although they proved to be less sensitive. Nonetheless, they served as powerful tools to provide additional information about the course and gravity of infection in a noninvasive manner, possibly allowing a reduction in the number of animals needed for research evaluation of new antibiotics in future studies.

Membrane Microdomain Disassembly Inhibits MRSA Antibiotic Resistance

“…To determine whether MRSA penicillin sensitivity can be achieved in an in vivo infection, we compared the infective potential of WT and Δ floA strains in a murine infection model. Infected mice (n = 10; 3 × 10 7 colony-forming units [CFU]) were treated with oxacillin (200 mg/kg/day) ( Hertlein et al., 2014 ) and the survival rate was monitored 3 days post infection ( Figure 7 G). Mice infected with the WT strain showed higher mortality (10% survival rate) than those infected with a Δ floA mutant (70% survival rate; p < 0.01).…”

Development of a Staphylococcus aureus reporter strain with click beetle red luciferase for enhanced in vivo imaging of experimental bacteremia and mixed infections

“…The use of in vivo BLI with bioluminescent S. aureus strains has permitted the noninvasive and longitudinal monitoring of the bacterial burden, which has provided key information about the infectious course and disease pathogenesis in skin and soft tissue infections 13,17,22–26 as well as musculoskeletal infections 16,19,27–34 . In addition, this technology has been used to evaluate therapeutics, such as antibiotics 18,20,35–39 , active and passive vaccines 29,40,41 and other antimicrobials 37,42 as well as S. aureus -specific diagnostic imaging probes 27,43,44 .…”

Immunomimetic Designer Cells Protect Mice from MRSA Infection

“…The bactericidal efficacy of lysostaphin was reported to be higher than those of human native antimicrobials and broad-spectrum antibiotics, including penicillin ( Schaffner et al., 1967 ), oxacillin ( Kiri et al., 2002 ), and vancomycin ( Placencia et al., 2009 ). It is also effective against biofilms ( Kokai-Kun et al., 2009 , Hertlein et al., 2014 ) and has been widely tested in various animal models ( Dajcs et al., 2000 , Hertlein et al., 2014 , Kokai-Kun et al., 2003 , Kokai-Kun et al., 2007 , Patron et al., 1999 ) and in humans ( Davies et al., 2010 , Harris et al., 1967 , Stark et al., 1974 ).…”