IN-VITRO SUSCEPTIBILITY OF STREPTOCOCCUS-PNEUMONIAE TO THE D-ISOMERS AND L-ISOMERS OF OFLOXACIN - INTERPRETIVE CRITERIA AND QUALITY-CONTROLLIMITS

The 1-isomer of ofloxacin (levofloxacin) was twice as active as ofloxa cin and the d-isomer was inactive against 654 Streptococcus pneumoniae isolates. For disc susceptibility tests of pneumococci, 5 mu g levofl oxacin discs can be used with interpretive criteria of less than or eq ual to 12 mm for resistant (MIC greater than or equal to 8.0 mg/L) and greater than or equal to 16 mm for susceptible (MIC less than or equa l to 2.0 mg/L). For quality control of levofloxacin tests, S. pneumoni ae ATCC 49619 should give zones 20-25 mm in diameter and MICs 0.5-2.0 mg/L.