Amikacin Susceptibility Testing 

Ceftazidime is a third-generation cephalosporin with broad-spectrum activity, particularly against Gram-negative bacteria, including Pseudomonas aeruginosa. It is used for treating serious infections such as hospital-acquired pneumonia, bloodstream infections, urinary tract infections (UTIs), and intra-abdominal infections. Susceptibility testing for ceftazidime is critical for guiding therapy, especially in the presence of extended-spectrum beta-lactamases (ESBLs) and carbapenemase-producing organisms.

Content:

• Testing Methods:
  • Disk Diffusion (Kirby-Bauer Method):
    • Disks containing ceftazidime (30 µg) are placed on Mueller-Hinton agar plates inoculated with the bacterial isolate.
    • After incubation, the diameter of the inhibition zone is measured and interpreted using CLSI or EUCAST guidelines.
  • Minimum Inhibitory Concentration (MIC) Testing:
    • MIC testing is performed using broth microdilution, agar dilution, or automated systems.
    • The MIC is the lowest concentration of ceftazidime that inhibits visible bacterial growth.
• • Automated Testing Systems:
    • Platforms like Vitek, Phoenix, or MicroScan may include ceftazidime in their susceptibility testing panels.

Application:

• Clinical Use:
  • Ceftazidime is used for treating:
    • Hospital-acquired and ventilator-associated pneumonia.
    • Complicated urinary tract infections (cUTIs) caused by susceptible organisms.
    • Complicated intra-abdominal infections, often in combination with metronidazole for anaerobic coverage.
    • Sepsis and bloodstream infections caused by Gram-negative bacteria.
    • Pseudomonas aeruginosa infections in various sites, including lungs, bloodstream, and soft tissues.
  • Susceptibility testing ensures appropriate use, particularly in infections caused by multidrug-resistant Gram-negative organisms.
• Epidemiological Surveillance:
  • Tracks resistance trends in Enterobacterales and Pseudomonas aeruginosa.
  • Monitors the emergence of ESBL- and carbapenemase-producing organisms in healthcare settings.

Ceftazidime susceptibility testing is essential for guiding therapy in infections caused by Gram-negative bacteria, particularly Pseudomonas aeruginosa and Enterobacterales. Standardized methods, such as MIC testing and disk diffusion, provide reliable results.