Amikacin Susceptibility Testing 

Ceftaroline is a fifth-generation cephalosporin with broad-spectrum activity against Gram-positive and Gram-negative bacteria. It is unique among cephalosporins because of its potent activity against methicillin-resistant Staphylococcus aureus (MRSA) due to its ability to bind to PBP2a (penicillin-binding protein 2a), a resistance mechanism in MRSA. It is used for treating complicated skin and soft tissue infections (cSSTIs) and community-acquired bacterial pneumonia (CABP). Susceptibility testing is critical for guiding its use in resistant infections.

Content:

• Testing Methods:
  • Disk Diffusion (Kirby-Bauer Method):
    • Disks containing ceftaroline (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 is determined using broth microdilution, agar dilution, or automated systems.
    • The MIC is the lowest concentration of ceftaroline that inhibits visible bacterial growth.
• • Automated Systems:
    • Platforms like Vitek, Phoenix, or MicroScan can provide MIC values for ceftaroline.

Application:

• Clinical Use:
  • Ceftaroline is approved for treating:
    • Complicated skin and soft tissue infections (cSSTIs), including those caused by MRSA and Streptococcus spp.
    • Community-acquired bacterial pneumonia (CABP) caused by susceptible pathogens.
  • Off-label use includes treatment of bloodstream infections and osteomyelitis caused by MRSA when other therapies are unsuitable.
• Antimicrobial Stewardship:
  • Encourages targeted use of ceftaroline in MRSA infections, reducing reliance on vancomycin or linezolid.
• • Avoids inappropriate use in infections caused by Gram-negative organisms producing ESBLs or carbapenemases.
• Epidemiological Surveillance:
  • Monitors the emergence of ceftaroline resistance, particularly in MRSA and Streptococcus pneumoniae.
  • Tracks susceptibility trends in Enterobacterales and other Gram-negative bacteria.

Ceftaroline susceptibility testing is essential for guiding therapy in infections caused by MRSA, Streptococcus pneumoniae, and certain Gram-negative bacteria. Standardized methods, including MIC testing and disk diffusion, ensure reliable results.