Comparison of three methods for identifying nonfermenting gram-negative rods

Area of Science:

• Clinical Microbiology
• Bacterial Identification
• Diagnostic Systems

Background:

• Accurate identification of nonfermenting gram-negative rods is crucial for patient care.
• Conventional methods are labor-intensive, necessitating evaluation of automated systems.
• The API and Oxi-Ferm systems are widely used for bacterial identification.

Purpose of the Study:

• To compare the accuracy of the API and Oxi-Ferm systems against conventional methods for identifying nonfermenting gram-negative rods.
• To identify specific challenges encountered by each system in bacterial identification.

Main Methods:

• Seventy-six nonfermenting gram-negative rod strains were tested using the API system and conventional media.
• Fifty-one strains were additionally tested using the Oxi-Ferm system.
• Identification results from automated systems were compared to those from conventional methods.

Main Results:

• The Oxi-Ferm system achieved 72% agreement with conventional methods, while the API system showed only 41% agreement.
• Both systems exhibited difficulties in identifying Pseudomonas aeruginosa (API) and P. cepacia.
• Oxi-Ferm had more individual biochemical discrepancies but higher overall agreement.

Conclusions:

• The Oxi-Ferm system offers a more accurate identification of nonfermenting gram-negative rods compared to the API system.
• Further refinement of both systems may be needed to improve identification of challenging species.
• Automated systems provide valuable alternatives to conventional methods in clinical microbiology labs.