Cefixime Susceptibility Testing
Cefixime is an oral third-generation cephalosporin antibiotic with broad-spectrum activity against Gram-negative bacteria and limited activity against Gram-positive bacteria. It is widely used for treating urinary tract infections, respiratory infections, and sexually transmitted infections, particularly gonorrhea. Susceptibility testing for cefixime is crucial to determine its efficacy, especially given the increasing resistance among Neisseria gonorrhoeae and other Gram-negative pathogens.
Content:
- Testing Methods:
- Disk Diffusion (Kirby-Bauer Method):
- Disks containing cefixime (5 µg) are placed on Mueller-Hinton agar plates inoculated with the bacterial isolate.
- Disk Diffusion (Kirby-Bauer Method):
- Minimum Inhibitory Concentration (MIC) Testing:
- MIC is determined using broth microdilution or agar dilution methods.
- The MIC is the lowest concentration of cefixime that inhibits visible bacterial growth.
- E-test (Gradient Diffusion):
- A strip with a gradient of cefixime concentrations is placed on an inoculated agar plate.
- Automated Systems:
- Systems like Vitek, Phoenix, or MicroScan can provide MICs for cefixime, but validation for certain pathogens may be limited.
- Minimum Inhibitory Concentration (MIC) Testing:
Application:
- Clinical Use:
- Cefixime is used for:
- Uncomplicated urinary tract infections (UTIs) caused by susceptible Escherichia coli and Proteus mirabilis.
- Respiratory tract infections, including otitis media, sinusitis, and bronchitis.
- Gonorrhea, as part of combination therapy for susceptible Neisseria gonorrhoeae.
- Uncomplicated infections caused by Gram-negative organisms, particularly in outpatient settings.
- Cefixime is used for:
- Antimicrobial Stewardship:
- Promotes appropriate cefixime use to avoid unnecessary reliance on oral fluoroquinolones or broader-spectrum cephalosporins.
- Reduces the risk of resistance development by encouraging targeted therapy.
- Epidemiological Surveillance:
- Monitors resistance trends in Neisseria gonorrhoeae, particularly in regions with rising cefixime resistance.
Cefixime susceptibility testing is essential for managing infections caused by Gram-negative bacteria, especially in the context of rising resistance among Neisseria gonorrhoeae and ESBL-producing Enterobacterales.
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