Performance Validation of Selective Screening Agars for Guiding Antimicrobial Prophylaxis in Patients Undergoing...

A rectal culture-guided antimicrobial prophylaxis strategy may prevent infections after transrectal ultrasound-guided prostate biopsy (TRUSP). The use of selective culture media could assist the choice of appropriate antibiotic prophylaxis. The objective of our study was to evaluate the performance of four selective media used for guidance of oral antibiotic prophylaxis in TRUSP. In this prospective validation study, we used MacConkey media with vancomycin plus one of the following antibiotics: ciprofloxacin (McC3+CIP/V), trimethoprim (McC3+TMP/V), fosfomycin (McC3+FOF/V), and amdinocillin-amoxicillin-clavulanic acid (McC3+MEC/V). First, clinical strains of Gram-negative bacilli (GNB) (n = 33) were evaluated for growth on the selective media. Thereafter, rectal swabs (n = 97) were randomly collected from residual material of fresh stool samples and plated on a growth control and the four selective media. Levels of recovery of GNB on the growth control and selective media were compared, and the MICs of the antibiotics used in this study were determined. The sensitivity and specificity of the four selective media amounted, respectively, to 90.0% (55.5 to 99.8%) and 98.7% (93.1 to 100.0%) for McC3+CIP/V, 95.7% (85.2 to 99.5%) and 100.0% (91.6 to 100.0%) for McC3+TMP/V, 95.5% (84.5 to 99.4%) and 97.8% (88.2 to 99.9%) for McC3+FOF/V, and 100.0% (76.8 to 100.0%) and 97.6% (87.4 to 99.9%) for McC3+MEC/V. In conclusion, the four selective media were sufficiently sensitive and specific for the identification of rectal GNB resistant to ciprofloxacin, trimethoprim, fosfomycin, or amdinocillin-amoxicillin-clavulanic acid. These media can have added value in streamlining the optimal culture based antibiotic prophylaxis in TRUSP in a non-labor-intensive manner.