Activity of FCE 22101 against methicillin-resistant Staphylococcus aureus and affinity for penicillin binding proteins

The susceptibility of 47 clinical isolates of methicillin-resistant Staphylococcus aureus (MRSA) to FCE 22101, imipenem and methicillin was determined with Iso-Sensitest media, with or without NaCl and with incubation at 30 degrees and 37 degrees C and for 24 and 48 h. All strains had a MIC 8 mg/l of methicillin under at least one of the culture conditions. The MIC90 of FCE 22101 was 1 mg/l, and that of imipenem 16 mg/l. The affinity of FCE 22101 for the penicillin-binding proteins (PBPs) of five clinical isolates of MRSA and S. aureus 13136 p-m+ was examined in envelope preparations and whole cell assay under the growth conditions listed above. PBP 2' was detected in all MRSA, and the clinical isolates had an I50 of 4 mg/l FCE 22101. These in-vitro data suggest that FCE 22101 may be active against MRSA in clinical use.