BACKGROUND: The emergence of bacterial drug resistance encourages the 
re-evaluation of the potential of existing antimicrobials. Lantibiotics are 
post-translationally modified, ribosomally synthesised antimicrobial peptides 
with a broad spectrum antimicrobial activity. Here, we focussed on expanding the 
potential of lacticin 3147, one of the most studied lantibiotics and one which 
possesses potent activity against a wide range of Gram positive species 
including many nosocomial pathogens. More specifically, our aim was to 
investigate if lacticin 3147 activity could be enhanced when combined with a 
range of different clinical antibiotics.
RESULTS: Initial screening revealed that polymyxin B and polymyxin E (colistin) 
exhibited synergistic activity with lacticin 3147. Checkerboard assays were 
performed against a number of strains, including both Gram positive and Gram 
negative species. The resultant fractional inhibitory concentration (FIC) index 
values established that, while partial synergy was detected against Gram 
positive targets, synergy was obvious against Gram negative species, including 
Cronobacter and E. coli.
CONCLUSIONS: Combining lacticin 3147 with low levels of a polymyxin could 
provide a means of broadening target specificity of the lantibiotic, while also 
reducing polymyxin use due to the lower concentrations required as a result of 
synergy.