Ofloxacin (Page 3 of 10)

Diffusion Techniques

Quantitative methods that require measurement of zone diameters also provide reproducible estimates of the susceptibility of bacteria to antimicrobial compounds. One such standardized procedure2 requires the use of standardized inoculum concentrations. This procedure uses paper disks impregnated with 5 mcg ofloxacin to test the susceptibility of microorganisms to ofloxacin.

Reports from the laboratory providing results of the standard single-disk susceptibility test with a 5 mcg ofloxacin disk should be interpreted according to the following criteria:

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

Zone Diameter (mm)

Interpretation

≥ 16

Susceptible (S)

13 to 15

Intermediate (I)

≤ 12

Resistant (R)

For testing Haemophilus influenzae:g

Zone Diameter (mm)

Interpretation

≥ 16

Susceptible (S)

g This zone diameter standard is applicable only to disk diffusion tests with Haemophilus influenzae using Haemophilus Test Medium (HTM)2 incubated in 5% CO2 .

The current absence of data on resistant strains precludes defining any results other than “Susceptible.” Strains yielding zone diameter results suggestive of a “nonsusceptible” category should be submitted to a reference laboratory for further testing.

For testing Neisseria gonorrhoeae:h

Zone Diameter (mm)

Interpretation

≥ 31

Susceptible (S)

25 to 30

Intermediate (I)

≤ 24

Resistant (R)

h These zone diameter standards are applicable only to disk diffusion tests using GC agar base and 1% defined growth supplement incubated in 5% CO2 .

For testing Streptococcus pneumoniae and Streptococcus pyogenes:i

Zone Diameter (mm)

Interpretation

≥ 16

Susceptible (S)

13 to 15

Intermediate (I)

≤ 12

Resistant (R)

i These zone diameter standards are applicable only to disk diffusion tests performed using Mueller-Hinton agar supplemented with 5% defibrinated sheep blood and incubated in 5% CO2 .

Interpretation should be as stated above for results using dilution techniques. Interpretation involves correlation of the diameter obtained in the disk test with the MIC for ofloxacin.

As with standardized dilution techniques, diffusion methods require the use of laboratory control microorganisms that are used to control the technical aspects of the laboratory procedures. For the diffusion technique, the 5 mcg ofloxacin disk should provide the following zone diameters in these laboratory quality control strains:

Microorganism

Zone Diameter (mm)

Escherichia coli

ATCC 25922

29 to 33

Haemophilus influenzae

ATCC 49247j

31 to 40

Neisseria gonorrhoeae

ATCC 49226k

43 to 51

Pseudomonas aeruginosa

ATCC 27853

17 to 21

Staphylococcus aureus

ATCC 25923

24 to 28

Streptococcus pneumoniae

ATCC 49619l

16 to 21

j This quality control range is applicable only to H. influenzae ATCC 49247 tested by a disk diffusion procedure using Haemophilus Test Medium (HTM)2 incubated in 5% CO2 .

k This quality control range is applicable only to N. gonorrhoeae ATCC 49226 tested by a disk diffusion procedure using GC agar base with 1% defined growth supplement incubated in 5% CO2 .

l This quality control range is applicable only to S. pneumoniae ATCC 49619 tested by a disk diffusion procedure using Mueller-Hinton agar supplemented with 5% defibrinated sheep blood and incubated in 5% CO2 .

INDICATIONS AND USAGE

To reduce the development of drug-resistant bacteria and maintain the effectiveness of ofloxacin tablets and other antibacterial drugs, ofloxacin tablets should be used only to treat or prevent infections that are proven or strongly suspected to be caused by susceptible bacteria. When culture and susceptibility information are available, they should be considered in selecting or modifying antibacterial therapy. In the absence of such data, local epidemiology and susceptibility patterns may contribute to the empiric selection of therapy.

Ofloxacin tablets are indicated for the treatment of adults with mild to moderate infections (unless otherwise indicated) caused by susceptible strains of the designated microorganisms in the infections listed below. Please see DOSAGE AND ADMINISTRATION for specific recommendations.

Acute Bacterial Exacerbations of Chronic Bronchitis due to Haemophilus influenzae or Streptococcus pneumoniae.

Community-Acquired Pneumonia due to Haemophilus influenzae or Streptococcus pneumoniae.

Uncomplicated Skin and Skin Structure Infections due to methicillin-susceptible Staphylococcus aureus, Streptococcus pyogenes, or Proteus mirabilis.

Acute, Uncomplicated Urethral and Cervical Gonorrhea due to Neisseria gonorrhoeae (see WARNINGS).

Nongonococcal Urethritis and Cervicitis due to Chlamydia trachomatis (see WARNINGS).

Mixed Infections of the Urethra and Cervix due to Chlamydia trachomatis and Neisseria gonorrhoeae (see WARNINGS).

Acute Pelvic Inflammatory Disease (including severe infection) due to Chlamydia trachomatis and/or Neisseria gonorrhoeae (see WARNINGS).

NOTE: If anaerobic microorganisms are suspected of contributing to the infection, appropriate therapy for anaerobic pathogens should be administered.

Uncomplicated Cystitis due to Citrobacter diversus, Enterobacter aerogenes, Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis, or Pseudomonas aeruginosa.

Complicated Urinary Tract Infections due to Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis, Citrobacter diversus ,* or Pseudomonas aeruginosa.*

Prostatitis due to Escherichia coli.

* = Although treatment of infections due to this organism in this organ system demonstrated a clinically significant outcome, efficacy was studied in fewer than 10 patients.

Appropriate culture and susceptibility tests should be performed before treatment in order to isolate and identify organisms causing the infection and to determine their susceptibility to ofloxacin, USP. Therapy with ofloxacin, USP may be initiated before results of these tests are known; once results become available, appropriate therapy should be continued.

As with other drugs in this class, some strains of Pseudomonas aeruginosa may develop resistance fairly rapidly during treatment with ofloxacin, USP. Culture and susceptibility testing performed periodically during therapy will provide information not only on the therapeutic effect of the antimicrobial agent but also on the possible emergence of bacterial resistance.

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