Background and Importance One of the measures to reduce the rate of infections by multidrug-resistant bacteria in Intensive Care Unit (ICU) services promoted in the Pneumonia Zero (NZ) programme is oropharyngeal decontamination (DOF) and/or selective digestive decontamination (SDD). Of the different existing protocols, we implemented the administration of non-absorbable topical antimicrobials (colistin, gentamicin and nystatin) in the oropharynx (paste) and gastrointestinal tract (solution). Both were developed as magistral formulas. In the event of MRSA isolation or an increase in the MRSA rate in our hospital, vancomycin would be added.

Aim and Objectives The aim was to assess the effect of such a measure on studies of the prevalence of multidrug-resistant bacteria in critically ill patients, and to see if there is selection for resistance mechanisms.

Material and Methods Ambispective study comprising the pre-DDS (01/01/2022–30/04/2022) and DDS (01/01/2023–30/04/2023) periods conducted in the 22-bed ICU.

From July 2022, ICU patients with isolation of multidrug-resistant bacteria in both clinical or surveillance samples, as well as patients with estimated intubation >72 h or non-intubated patients with risk factors for developing pneumonia are administered DDS/DOF. In addition, nasal, pharyngo-tonsillar and perianal exudate samples are collected for microbiological surveillance cultures on admission and every Tuesday thereafter. Incubate at 37°C for 48h.

Results In the pre-DDS period in the ICU, 626 samples are received for colonisation studies from 132 patients. Excluding repeat isolates in each patient,2 3 multidrug-resistant bacteria were detected. In the DDS period, 537 samples are received from 124 patients, detecting nine multi-resistant bacteria. There is a significant difference (p=0.0138) between the proportion of multi-drug resistant bacteria detected in the surveillance studies after applying ICU decontamination measures.

In the first period, the following bacteria were detected: one MRSA, one Acinetobacter baumannii, eight extended-spectrum beta-lactamase (ESBL)-producing enterobacteria and 13 carbapenemase-producing gram-negative bacilli.

Pathogens isolated in the post-decontamination period were: one MRSA, one A.baumannii and 8 BLEE-producing enterobacteria. None of the isolates are carbapenemase-producing.

Conclusion and Relevance The DDS/DOF protocols applied in the ICU of our hospital have shown a significant decrease in colonisation by multidrug-resistant bacteria in critically ill patients. As for MRSA, no differences could be seen in this period, so it would be advisable to extend the study period. However, the role of this measure in the disappearance of carbapenemase-producing bacteria should be highlighted.

Conflict of Interest No conflict of interest.