Aerococcus urinae and trimethoprim-sulfamethoxazole

Area of Science:

• Microbiology
• Antimicrobial Resistance
• Clinical Diagnostics

Background:

• Aerococcus urinae is a pathogen increasingly recognized for causing infections.
• Previous reports indicate trimethoprim-sulfamethoxazole (SXT) resistance in A. urinae.
• The influence of laboratory testing conditions on antimicrobial susceptibility results is critical.

Purpose of the Study:

• To investigate the impact of different test media on the observed susceptibility of Aerococcus urinae to trimethoprim-sulfamethoxazole (SXT).
• To determine if the reported SXT resistance in A. urinae is a consistent finding across various laboratory conditions.

Main Methods:

• Twenty-seven clinical isolates of Aerococcus urinae were utilized.
• Antimicrobial susceptibility testing for SXT was performed.
• Testing was conducted in two different media: cation-adjusted Mueller-Hinton broth (CAMHB) supplemented with lysed horse blood and CAMHB supplemented with lysed sheep blood.

Main Results:

• All 27 clinical isolates of A. urinae demonstrated susceptibility to SXT when tested in CAMHB with lysed horse blood.
• In contrast, the same isolates exhibited resistance to SXT when tested in CAMHB with lysed sheep blood.

Conclusions:

• The observed antimicrobial susceptibility of Aerococcus urinae to trimethoprim-sulfamethoxazole is significantly influenced by the type of lysed blood used in the test medium.
• These findings highlight the importance of standardized testing protocols and highlight potential discrepancies in clinical susceptibility reporting for A. urinae.