In vitro activities of 22 antimicrobial agents against Listeria monocytogenes strains isolated in Barcelona, Spain

The in vitro activity of 22 antimicrobial agents against 82 human Listeria monocytogenes strains isolated in Barcelona from 1994 to 1998 was determined. Ampicillin and gentamicin showed good in vitro activity against all strains (MIC90: 1 and ≤0.25 μg/ml, respectively). No resistance to rifampin or co-trimoxazole was detected and only one strain was resistant to tetracycline. Of the nine fluoroquinolones tested, clinafloxacin and gemifloxacin were the most active compounds (MIC90: 0.12 and 0.25 μg/ml, respectively). No increasing MICs values were observed during the five-year period.