Ofloxacin has been shown to be active against most strains of the following microorganisms both in vitro and in clinical infections as described in the INDICATIONS AND USAGE Section:

Aerobic Gram-positive microorganisms

Staphylococcus aureus (methicillin-susceptible strains)
Streptococcus pneumoniae (penicillin-susceptible strains)
Streptococcus pyogenes

Aerobic Gram-negative microorganisms

Citrobacter (diversus) koseri
Enterobacter aerogenes
Escherichia coli
Haemophilus influenzae
Klebsiella pneumoniae
Neisseria gonorrhoeae
Proteus mirabilis
Pseudomonas aeruginosa

As with other drugs in this class, some strains of Pseudomonas aeruginosa may develop resistance fairly rapidly during treatment with ofloxacin.

Other microorganisms

Chlamydia trachomatis

The following in vitro data are available, but their clinical significance is unknown.

Ofloxacin exhibits in vitro minimum inhibitory concentrations (MIC values) of 2 μg/mL or less against most ( ≥ 90%) strains of the following microorganisms; however, the safety and effectiveness of ofloxacin in treating clinical infections due to these microorganisms have not been established in adequate and well-controlled trials.

Aerobic Gram-positive microorganisms

Staphylococcus epidermidis (methicillin-susceptible strains)
Staphylococcus saprophyticus
Streptococcus pneumoniae (penicillin-resistant strains)

Aerobic Gram-negative microorganisms

Acinetobacter calcoaceticus
Bordetella pertussis
Citrobacter freundii
Enterobacter cloacae
Haemophilus ducreyi
Klebsiella oxytoca
Moraxella catarrhalis
Morganella morganii
Proteus vulgaris
Providencia rettgeri
Providencia stuartii
Serratia marcescens

Anaerobic microorganisms

Clostridium perfringes

Other microorganisms

Chlamydia pneumoniae
Gardnerella vaginalis
Legionella pneumophila
Mycoplasma hominis
Mycoplasma pneumoniae
Ureaplasma urealyticum

Ofloxacin is not active against Treponema pallidum (See WARNINGS.)

Many strains of other streptococcal species, Enterococcus species, and anaerobes are resistant to ofloxacin.

Susceptibility Tests

Dilution Techniques:

Quantitative methods are used to determine antimicrobial minimum inhibitory concentrations (MIC values). These MIC values provide estimates of the susceptibility of bacteria to antimicrobial compounds. The MIC values should be determined using a standardized procedure. Standardized procedures are based on a dilution method¹ (broth or agar) or equivalent with standardized inoculum concentrations and standardized concentrations of ofloxacin powder. The MIC values should be interpreted according to the following criteria:

For testing Enterobacteriaceae, methicillin-susceptible Staphylococcus aureus, and Pseudomonas aeruginosa:

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