Lack of synergism of ampicillin and gentamicin in experimental listeriosis

Infection. Jan-Feb 1987;15(1):40-1. doi: 10.1007/BF01646117.


Strain SLCC 4013 of Listeria monocytogenes is susceptible in vitro to ampicillin (MIC 0.5 mg/l) as well as to gentamicin (MIC 0.5 mg/l). Whereas treatment of mice infected with this virulent strain with 0.5 mg ampicillin twice a day resulted in a marked decrease in bacterial counts per spleen, the administration of 2 mg gentamicin twice a day hardly reduced bacterial multiplication. The combination of both drugs was not much more effective than ampicillin alone. Thus, a synergistic effect of both these antibiotics on intracellularly growing bacteria could not be demonstrated.

MeSH terms

  • Ampicillin / therapeutic use*
  • Animals
  • Dose-Response Relationship, Drug
  • Drug Therapy, Combination
  • Female
  • Gentamicins / therapeutic use*
  • Listeriosis / drug therapy*
  • Mice
  • Mice, Inbred Strains
  • Microbial Sensitivity Tests


  • Gentamicins
  • Ampicillin