Screening for antimicrobial resistance in fecal samples by the replica plating method

Area of Science:

• Microbiology
• Clinical Laboratory Science

Background:

• Antibiotic resistance in normal flora is a growing concern.
• Accurate detection methods are crucial for monitoring resistance patterns.

Purpose of the Study:

• To evaluate replica plating as a method for detecting antibiotic resistance in normal flora.
• To compare replica plating with a standard five-colony method for resistance detection.
• To validate breakpoint concentrations for replica plating.

Main Methods:

• Compared replica plating with a five-colony method for antibiotic resistance detection.
• Screened 131 fecal samples for resistance to six antibiotics (ampicillin, cefuroxime, nalidixic acid, trimethoprim, sulfamethoxazole, tetracycline).
• Determined Minimum Inhibitory Concentrations (MICs) using standard agar dilution for the five-colony method.

Main Results:

• Replica plating showed no statistically significant difference in resistance detection rates compared to the five-colony method for all tested antibiotics.
• Breakpoint concentrations used in replica plating yielded results comparable to agar dilution methods and National Committee for Clinical Laboratory Standards values.
• Replica plating precisely determined resistance frequencies, revealing an uneven distribution (minority or dominant) in most samples.

Conclusions:

• Replica plating is a reliable and recommended method for detecting antibiotic resistance in normal flora.
• The method offers precise quantification of resistant bacterial populations.
• Observed uneven distribution of resistant flora highlights the need for sensitive detection techniques.