Detection methods for carbapenem-resistant Pseudomonas aeruginosa in surface water and wastewater

This study aimed to develop a standardized method for detecting carbapenem-resistant P. aeruginosa (CRPA) in water samples, both surface water and wastewater. The growth of well-characterized CRPA strains was determined in four selective agar media supplemented with imipenem, meropenem, or ceftazidime. Wastewater samples presumptively containing CRPA and surface water samples spiked with CRPA strains were filtered and cultured using selective agar plates supplemented with imipenem and meropenem. M-PA-C agar plates supplemented with imipenem performed best compared to other selective agar plates, with a positive predictive value of 80-100%. A prior step using asparagine proline broth with vancomycin is recommended for higher specificity. A combination of nonselective enrichment with selective plating is recommended for low limits of detection. The addition of imipenem in broth increased the lower limit of detection and a lower PPV (32 % vs 73%).