The antibacterial activities of
amoxicillin-
gentamicin,
trovafloxacin,
trimethoprim-sulfamethoxazole (
TMP-SMX) and the combination of
trovafloxacin with
TMP-SMX were compared in a model of
meningoencephalitis due to Listeria monocytogenes in infant rats. At 22 h after intracisternal
infection, the cerebrospinal fluid was cultured to document
meningitis, and the treatment was started. Treatment was instituted for 48 h, and efficacy was evaluated 24 h after administration of the last dose. All tested treatment regimens exhibited significant activities in brain, liver, and blood compared to infected rats receiving saline (P < 0.001). In the brain,
amoxicillin plus
gentamicin was more active than all of the other regimens, and
trovafloxacin was more active than
TMP-SMX (bacterial titers of 4.1 +/- 0.5 log10 CFU/ml for
amoxicillin-
gentamicin, 5.0 +/- 0.4 log10 CFU/ml for
trovafloxacin, and 5.8 +/- 0.5 log10 CFU/ml for
TMP-SMX; P < 0.05). In liver,
amoxicillin-
gentamicin and
trovafloxacin were similarly active (2.8 +/- 0.8 and 2.7 +/- 0.8 log10 CFU/ml, respectively) but more active than
TMP-SMX (4.4 +/- 0. 6 log10 CFU/ml; P < 0.05). The combination of
trovafloxacin with
TMP-SMX did not alter the antibacterial effect in the brain, but it did reduce the effect of
trovafloxacin in the liver.
Amoxicillin-
gentamicin was the most active
therapy in this study, but the activity of
trovafloxacin suggests that further studies with this
drug for the treatment of
Listeria infections may be warranted.