IN-VITRO SUSCEPTIBILITY OF LISTERIA-MONOCYTOGENES - COMPARISON OF THEE-TEST WITH THE AGAR-DILUTION-TEST

In vitro susceptibility testing was performed on 66 strains of Listeri a monocytogenes. Recently obtained clinical isolates from Austria, Fra nce, Norway and Switzerland and 17 reference strains from three type c ulture collections were tested against ampicillin, gentamicin, trimeth oprim-sulfamethoxazole, ampicillin-sulbactam, meropenem, and first-, s econd-, third- and fourth-generation cephalosporins. All isolates were susceptible to ampicillin, gentamicin, and trimethoprim-sulfamethoxaz ole, ampicillin-sulbactam, and meropenem and more than 86% of the mini mal inhibitory concentration E test values were within plus/minus one dilution step of the agar dilution test. In vitro susceptibility of L. monocytogenes has not changed markedly during the last decades; the l evel of susceptibility of old reference strains did not differ from th at of recently encountered clinical isolates. The E test seems to be a suitable method for Listeria.