In vivo activity of nisin A and nisin V against Listeria monocytogenes in mice

Abstract

Background: Lantibiotics are post-translationally modified antimicrobial peptides, of which nisin A is the most extensively studied example. Bioengineering of nisin A has resulted in the generation of derivatives with increased in vitro potency against Gram-positive bacteria. Of these, nisin V (containing a Met21Val change) is noteworthy by virtue of exhibiting enhanced antimicrobial efficacy against a wide range of clinical and food-borne pathogens, including Listeria monocytogenes. However, this increased potency has not been tested in vivo.

Results: Here we address this issue by assessing the ability of nisin A and nisin V to control a bioluminescent strain of Listeria monocytogenes EGDe in a murine infection model.More specifically, Balb/c mice were infected via the intraperitoneal route at a dose of 1 × 10(5) cfu/animal and subsequently treated intraperitoneally with either nisin V, nisin A or a PBS control. Bioimaging of the mice was carried out on day 3 of the trial. Animals were then sacrificed and levels of infection were quantified in the liver and spleen.

Conclusion: This analysis revealed that nisin V was more effective than Nisin A with respect to controlling infection and therefore merits further investigation with a view to potential chemotherapeutic applications.

Figure 1

The structure of nisin A showing the location of the N-terminal domain, containing one lanthionine and two (β-methyl) lanthionine rings (A, B, and C) linked to the C-terminal intertwined rings (D and E) by a flexible hinge region. Post-translational modifications are highlighted as follows: dehydroalanine (Dha); dehydrobutyrine (Dhb); lanthionine (A-S-A) and (β-methyl) lanthionine (Abu-S-A). Standard residues are represented in the single letter code. Arrow indicates location of the methionine to valine substitution (M21V) in nisin V.

Figure 2

Deferred antagonism assay and mass spectrometry analysis of nisin A and nisin V. (a) Inhibition of growth of L. monocytogenes EGDe::pPL2luxpHELP by the nisin A producing strain L. lactis NZ9700 and the nisin V producing strain L. lactis NZ9800nisA::M21V. (b) Mass spectrometry analysis of the nisin A (3353 amu) and nisin V (3321 amu) peptides produced by the bacterial strains L. lactis NZ9700 and L. lactis NZ9800nisA::M21V, respectively.

Figure 3

Analysis of effect of nisin A and nisin V on Listeria infection in mice 3 days after intraperitoneal infection with 1 × 10⁵ CFU Listeria monocytogenes EGDe::pPL2luxpHELP. Luminescence observed in animals injected with (a) phosphate buffered saline (PBS) (b) 58.82 mg/kg nisin A and (c) 58.82 mg/kg nisin V 30 minutes after Listeria infection.

Figure 4

(a) Relative light unit (RLU) counts in mice 3 days after intraperitoneal infection with 1 × 10⁵ CFU L. monocytogenes EGDe::pPL2luxpHELP. (b) CFU data from livers and (c) spleens of infected mice. Lines connecting groups indicate statistically significant differences between those groups (P < 0.05).