Active surveillance screening method for the detection of multidrug resistant gram-negative bacteria

Abstract

Background Patients with unrecognised colonisation with multi-drug resistant Gram-negative bacteria (MDRGNB) constitute a reservoir of organisms that can precede invasive disease and potentially be transmitted to other patients. A large percentage of patients colonised with these resistant bacteria are not recognised by clinical cultures but are only detected by performing surveillance cultures. 1 Aims To validate an active surveillance screening method to detect MDRGNB. Methods An agar-based method was trialled to detect MDRGNB. The media was tested against known susceptible and resistant organisms, mixed cultures, and clinical urine and rectal swab specimens. A low-risk ethics application was obtained. Results A selection of different media was used with each testing isolate: MacConkey agar (MCA) with gentamicin 8 mg/L, MCA with ciprofloxacin 2 mg/L, MCA with ceftazidime 2 mg/L and ESBL CHROMagar1. MCA without antibiotic addition was used as a control. The media was tested across 50 different specimens. Discussion We have demonstrated a reliable and practical method to screen for MDRGNB. This methodology can be utilised for an active surveillance study to establish colonisation rates with MDRGNB.