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A short-term program of performing serial active screening cultures (ASC) in the intensive care unit was instituted to establish a method for the detection of antibiotic-resistant Gram-negative bacteria (GNB) and the local rates of colonisation. Of all submitted ASC, 25.9% (30/116 collected swabs) isolated an antibiotic-resistant GNB. ChromID ESBL agar (bioMérieux, France) identified the majority of these organisms, with the additional antibiotic-impregnated media [MacConkey agar (MCA) with ciprofloxacin, MCA with gentamicin and MCA with ceftazidime] adding limited benefit. Compared to swabs performed on admission, 37.8% (14/37) of patients cultured a new antibiotic-resistant isolate on discharge. Serial screening in intensive care has the ability to identify patients with unrecognised colonisation with antibiotic-resistant GNB; however, the increase in the laboratory workload and logistical challenges in the collection of the surveillance swabs may limit this program's expansion.

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.