Direct Microbial Identification using An Automated Microbial Identification System to Facilitate the EUCAST RAST...

Area of Science:

• Clinical Microbiology
• Infectious Diseases
• Antimicrobial Stewardship

Background:

• Gram-negative (GN) sepsis requires rapid diagnosis and treatment, but conventional methods take 3-4 days.
• Existing rapid methods for antimicrobial susceptibility testing (AST) often rely on mass spectrometry, limiting use in resource-limited settings.
• Faster diagnostic turnaround time (TAT) is crucial for effective sepsis management.

Purpose of the Study:

• To evaluate a direct inoculum protocol (DIP) for rapid microbial identification of four common Gram-negative sepsis pathogens.
• To assess the feasibility of DIP for early AST reporting in resource-limited settings.
• To reduce the diagnostic TAT for Gram-negative sepsis.

Main Methods:

• A direct inoculum protocol (DIP) was evaluated using an automated microbial identification and AST system (aMIAST).
• DIP was used to identify four rapid AST (RAST) reportable Gram-negative pathogens directly from positively flagged automated blood culture bottles (+aBCs).
• Results from DIP were compared against the standard inoculum preparation protocol (SIP) in aMIAST.

Main Results:

• Of 105 monomorphic Gram-negative +aBCs identified by SIP, DIP correctly identified 94% (98/105) of the target pathogens.
• Major and very major error rates for DIP were 6% and 1.7%, respectively.
• Provisional clinical reports can be provided within 24 hours using DIP with the EUCAST RAST method.

Conclusions:

• The direct inoculum protocol (DIP) offers a viable alternative for rapid Gram-negative pathogen identification from blood cultures.
• This method significantly reduces diagnostic TAT, facilitating earlier antimicrobial therapy for sepsis.
• DIP has the potential to improve sepsis management in resource-limited settings by overcoming reliance on mass spectrometry.