aureus in a murine infection model . Nisin also displays potent in vitro activity against multi-drug resistant pathogens such as MRSA, vancomycin-intermediate and -heterogeneous S. aureus (VISA and hVISA, respectively)
and VRE, [19–21] while natural variants such C646 as nisin F also show potential in this regard . Notably, several studies have also demonstrated the in vivo efficacy of nisin A, [23–25] nisin Z, [26, 27] and Nisin F [28, 29]. Indeed, nisin F was recently shown to successfully treat respiratory disease caused by S. aureus K in immunocompromised Wistar rats . These animals were infected intranasally with 4 × 105 S. aureus cells prior to treatment with nisin F, also via the P505-15 clinical trial nasal route. Furthermore, nisin F was found to control the growth of S. aureus for up to 15 minutes in mice when injected into the peritoneal cavity . Animals were dosed with 1 × 108 S. aureus cells intraperitoneally and subsequently treated with nisin F, also via the intraperitoneal route. In a subsequent study, Nisin F-loaded
brushite cement was shown to prevent the growth of S. aureus Xen 36 . The brushite cement was subcutaneously implanted into mice and infected with 1 × 103 S. aureus cells. Release of nisin F from the bone cement prevented S. aureus infection for 7 days. Despite the potency of nisin and its natural variants, the gene encoded nature of these antimicrobials facilitates bioengineering thereof with a view to enhancing potency . Indeed, bioengineering of the hinge region of nisin A has been particularly NVP-BSK805 successful in generating variants with enhanced potency against Gram-positive pathogens [32, 33]. One particular derivative,
M21V (also known as nisin V), exhibits an in vitro activity against L. monocytogenes (the causative agent of listeriosis), and indeed other pathogens, which is superior to that of nisin A . While these laboratory-based studies demonstrate the enhanced potency of nisin V against all Gram-positive bacteria tested thus far, it is not known if this enhancement is also evident in vivo. In this study, we address this issue by comparing the efficacy of nisin A and nisin V against a lux-tagged strain of L. monocytogenes (EGDe::pPL2luxpHELP) using a murine infection model and, ultimately, demonstrate the greater MYO10 efficacy of the bioengineered peptide in controlling infection. Results/discussion The ability of nisin A and nisin V to control a L. monocytogenes infection in a murine peritonitis model was investigated. Analysis was carried out through bioluminescent imaging of the pathogen in living mice and through the microbiological analysis of organs when mice were sacrificed. Bioluminescence is achieved through the use of a strong constitutive promoter (Phelp [highly expressed Listeria promoter]) driving expression of the lux genes of P. luminescens integrated into the chromosome of L. monocytogenes EGDe . The resulting strain L.