2575. Dramatic Time-Dependent Changes of Bacterial and Fungal Taxonomic Signatures in 4 Body Regions of ICU Patients

BACKGROUND: It has been hypothesized that intensive care unit (ICU)-related complications like nosocomial pneumonia or gastrointestinal dysfunction are associated with disturbances of normal host microorganisms. However, these alterations are largely unknown in ICU patients. The bacterio- and mycobiota in 4 body regions in 14 ICU patients was investigated after admission until death or discharge to other wards. METHODS: Medical ICU patients were sampled with pharyngeal swabs, endotracheal aspirates, gastric secretions and stools or rectal swabs (in constipated patients). V1-V2 (16S rRNA gene) and eukaryoitic ITS sequencing was performed as previously described as well as denoizing, transformation into amplicon sequence variants and analysis using qiime2 and LEfSe (LDA Score > 3.0, P-value < 0.05). For sequence classification databases SILVA 132 (16S) and UNITE version 7.2 (ITS) were used. RESULTS: Samples were obtained at multiple time points from day 1 up to day 47 with a median of 11 samples per patient (range 2 to 17). In 11 patients all intended body regions were sampled (stool was missing in two patients and gastric secretion in two patients). The length of ICU stay and number of antibiotics administered during ICU stay was associated with loss of diversity in all investigated body sites. Taxonomic profiling showed a significant reduction of physiological members from the oral and fecal microbial community (e.g., Clostridiales, Bacteroidales, Faecalibacterium spp. etc.) after 2 weeks at the ICU. In contrast, Enterococcus spp. and Staphylococcus spp. were enriched in the gastric and fecal microbiota. Candida spp. dominated fungal communities of all body sites investigated. Staphylococcus aureus was associated with ITS positive, Candida spp. dominated samples throughout all body sites, while Pseudomonas aeruginosa was associated with ITS-negative samples. CONCLUSION: The length of the ICU stay and the number of different antibiotics administered during the stay at the ICU are associated with severe intestinal dysbiosis, determined by loss of physiological microbes, decreased bacterial richness and domination of low-diversity fecal microbiota. Early colonization of Candida spp. might favor a co-existance of a Staphylococcus spp.-dominated microbiota in the ICU. DISCLOSURES: All authors: No reported disclosures.