In-vitro synergy testing of nine antimicrobial combinations against Listeria monocytogenes.

In-vitro antimicrobial synergy against Listeria monocytogenes was assessed using nine combinations in chequerboard (bacteriostatic) tests and time-kill (bactericidal) studies. Ampicillin/gentamicin and trimethoprim/sulphamethoxazole were the most synergistic combinations in bacteristatic tests, whereas gentamicin with ampicillin, trimethoprim or vancomycin and trimethoprim/sulphamethoxazole were the most synergistic in bactericidal tests. Gentamicin-containing combinations were most effective at killing L. monocytogenes and those containing rifampicin least effective.