Cefoxitin disc diffusion test for detection of meticillin-resistant staphylococci

Area of Science:

• Clinical Microbiology
• Infectious Diseases
• Antimicrobial Resistance

Background:

• Staphylococci are primary causes of hospital-acquired infections.
• Increasing meticillin-resistant (MR) staphylococci pose a significant clinical challenge.
• Rapid and accurate detection of meticillin resistance is crucial for patient treatment and infection control.

Purpose of the Study:

• To evaluate the diagnostic accuracy of the cefoxitin disc diffusion (DD) test for detecting meticillin resistance in staphylococci.
• To compare the cefoxitin DD test with other methods like oxacillin DD, mecA gene PCR, and agar dilution (AD).

Main Methods:

• Tested 144 clinical staphylococcal isolates (97 *Staphylococcus aureus*, 47 coagulase-negative staphylococci) using cefoxitin and oxacillin DD tests.
• Confirmed resistance via *mecA* gene PCR and determined Minimum Inhibitory Concentrations (MICs) using agar dilution (AD).
• Assessed sensitivity and specificity of each method against *mecA* gene presence.

Main Results:

• The cefoxitin DD test demonstrated high sensitivity (94.44% for *S. aureus*, 80% for CoNS) and specificity (95.83% for *S. aureus*, 100% for CoNS).
• Compared to oxacillin DD, the cefoxitin DD test showed higher specificity but lower sensitivity.
• Agar dilution (AD) was highly sensitive and specific for both *S. aureus* and CoNS.

Conclusions:

• The cefoxitin disc diffusion test is a valuable tool for detecting meticillin resistance in staphylococci, particularly for its high specificity.
• Combining cefoxitin and oxacillin DD tests enhances the prediction of meticillin resistance.
• Agar dilution (AD) serves as a reliable confirmation method for meticillin resistance in laboratories lacking PCR capabilities.