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Levaquin

Clinical Pharmacology
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Clinical Pharmacology

Levaquin

Aerobic Gram-Negative Microorganisms

Acinetobacter baumannii
Acinetobacter lwoffii
Bordetella pertussis
Citrobacter koseri
Citrobacter freundii
Enterobacter aerogenes
Enterobacter sakazakii
Klebsiella oxytoca
Morganella morganii
Pantoea agglomerans
Proteus vulgaris
Providencia rettgeri
Providencia stuartii
Pseudomonas fluorescens

Anaerobic Gram-Positive Microorganisms

Clostridium perfringens

Susceptibility Tests

Susceptibility testing for levofloxacin should be performed, as it is the optimal predictor of activity.

• Dilution techniques:

Quantitative methods are used to determine antimicrobial minimal 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 levofloxacin powder. The MIC values should be interpreted according to the criteria outlined in Table 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 µg levofloxacin to test the susceptibility of microorganisms to levofloxacin.

Reports from the laboratory providing results of the standard single-disk susceptibility test with a 5 µg levofloxacin disk should be interpreted according the criteria outlined in Table 10. Interpretation involves correlation of the diameter obtained in the disk test with the MIC for levofloxacin.

Table 10: Susceptibility Interpretive Criteria for LEVAQUIN®


  Minimum Inhibitory
Concentrations (µg/mL)		 Disk Diffusion
(zone diameter in mm)
Pathogen S I R S I R
Enterobacteriaceae ≤ 2 4 ≥ 8 ≥ 17 14-16 ≤ 13
Enterococcus faecalis ≤ 2 4 ≥ 8 ≥ 17 14-16 ≤ 13
Methicillin-susceptible Staphylococcus species ≤ 2 4 ≥ 8 ≥ 17 14-16 ≤ 13
Pseudomonas aeruginosa ≤ 2 4 ≥ 8 ≥ 17 14-16 ≤ 13
Haemophilus influenzae ≤ 2a --b --b ≥ 17c --b --b
Haemophilus parainfluenzae ≤ 2a --b --b ≥ 17c --b --b
Streptococcus pneumoniae ≤ 2d 4d ≥ 8d ≥ 17e 14-16e ≤ 13 e
Streptococcus pyogenes ≤ 2 4 ≥ 8 ≥ 17 14-16 ≤ 13
S = Susceptible, I = Intermediate, R = Resistant
a These interpretive standards are applicable only to broth microdilution susceptibility testing with Haemophilus influenzae and Haemophilus parainfluenzae using Haemophilus Test Medium.1
b The current absence of data on resistant strains precludes defining any categories other than"Susceptible." Strains yielding MIC /zone diameter results suggestive of a "nonsusceptible"category should be submitted to a reference laboratory for further testing.
c These interpretive standards are applicable only to disk diffusion susceptibility testing with Haemophilus influenzae and Haemophilus parainfluenzae using Haemophilus Test Medium.2
d These interpretive standards are applicable only to broth microdilution susceptibility tests usingcation-adjusted Mueller-Hinton broth with 2-5% lysed horse blood.
e These zone diameter standards for Streptococcus spp. including S. pneumoniae apply only totests performed using Mueller-Hinton agar supplemented with 5% sheep blood and incubated in5% CO2.
Brand Name: Levaquin
Generic Name: Levofloxacin
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