Simple Sample Preparation Method for Direct Microbial Identification and Susceptibility Testing From Positive Blood...

Area of Science:

• Clinical microbiology
• Infectious diseases
• Diagnostic technology

Background:

• Rapid identification and antibiotic susceptibility testing are crucial for treating bloodstream infections effectively.
• Current methods often require lengthy culture-dependent processes, delaying targeted therapy.
• Simultaneous direct analysis from positive blood cultures remains an unmet clinical need.

Purpose of the Study:

• To develop and evaluate a combined method for simultaneous direct identification and antibiotic susceptibility testing of bacteria from positive blood cultures.
• To assess the speed, accuracy, and reliability of the novel method compared to conventional laboratory techniques.

Main Methods:

• A lysis-centrifugation-wash procedure was optimized to prepare bacterial pellets from positive blood cultures.
• Direct identification was performed using matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry (MALDI-TOF MS).
• Antibiotic susceptibility testing was conducted using the Vitek 2 system.

Main Results:

• The entire sample preparation process was completed in under 15 minutes.
• Direct MALDI-TOF MS achieved high identification rates: 96.49% for Gram-negative and 97.22% for Gram-positive bacteria.
• Vitek 2 testing showed high category agreement for antibiotic susceptibility: 96.89% for Gram-negative and 92.81% for Gram-positive bacteria, with low error rates.

Conclusions:

• The developed lysis-centrifugation-wash method provides a fast, easy, and accurate approach for direct bacterial identification and antibiotic susceptibility testing from positive blood cultures.
• This method has the potential to significantly expedite the selection of effective targeted antibiotic therapy for patients with bloodstream infections.
• The findings suggest a valuable alternative to conventional culture-dependent methods in clinical microbiology laboratories.