Screening for Gram-negative bacteria: Impact of preanalytical parameters

Area of Science:

• Microbiology
• Infectious Diseases
• Clinical Diagnostics

Background:

• Screening for multidrug-resistant Gram-negative bacteria often uses rectal swabs.
• Preanalytic steps like sampling technique, devices, and site are not standardized.
• Standardization is essential for optimal and consistent screening results.

Purpose of the Study:

• To identify optimal preanalytic parameters for rectal swab screening.
• To establish a general basis for screening irrespective of specific antibiotic resistance patterns.
• To compare different swab types and sampling sites for bacterial recovery.

Main Methods:

• Evaluation of rayon, polyurethane-cellular-foam, and nylon-flocked swabs.
• Assessment of perianal, intraanal, and deep intraanal sampling sites.
• Quantification of E. coli, K. pneumoniae, P. aeruginosa, and A. baumannii recovery.

Main Results:

• Bacterial recovery was independent of sampling time during hospital stay.
• Polyurethane-cellular-foam and nylon-flocked swabs showed significantly higher recovery than rayon swabs.
• Intraanal swabbing yielded higher bacterial quantities than perianal swabbing, except for A. baumannii detection.

Conclusions:

• Nylon-flocked or polyurethane-cellular-foam swabs and intraanal sampling are generally superior for bacterial recovery.
• Perianal sampling may be more suitable for detecting specific pathogens like A. baumannii.
• Gender-related differences in bacterial recovery were observed for perianal but not intraanal swabs.