Loss Of Colonization Research Articles

712. Dynamics of Colonization with Multi-Drug Resistant Organisms and Clinical Outcomes in Critically Ill Patients: A Prospective Cohort Study

Abstract Background Critically ill patients have frequent intestinal colonization with multi-drug resistant organisms (MDRO). However, the duration of colonization and its impact on clinical outcomes are unknown. Methods We performed a prospective cohort study of adult patients admitted to ICUs at a tertiary care hospital. All patients had stool samples collected twice weekly for up to four weeks or until discharge from the ICU. Stool samples were cultured with selective media for vancomycin-resistant enterococci (VRE), extended-spectrum β-lactamase-producing Enterobacterales (ESBL-E), and carbapenem-resistant Enterobacterales (CRE). We characterized patient demographics and compared outcomes between patients with and without colonization. Results A total of 102 patients were included. Mean age was 62 years (SD±15), 62 (61%) were men, 67 (66%) were white, and 34 (33%) were admitted from a separate healthcare facility. Thirty-nine (38%) were colonized with ≥1 MDRO at ≥1 time point. There were no statistically significant differences in baseline characteristics between patients with and without colonization. Of the 39 patients with colonization, 23 (59%) were colonized with VRE at ≥1 time point, 18 (46%) with ESBL-E, and 7 (18%) with CRE; 8 (20%) were colonized with >1 organism (Figure 1). Notably, most patients (13/23 with VRE, 15/18 with ESBL-E, and 4/7 with CRE colonization) were colonized with each MDRO type at only one time point during their ICU stay (Figure 1). In-hospital mortality did not differ according to colonization status (21% with any colonization vs. 17% without, p=0.70). When assessing mortality according to specific MDRO type, VRE colonization was associated with in-hospital mortality (35% with VRE colonization vs. 14% without, p=0.02). Figure 1. Results of serial stool samples tested for target multi-drug resistant organisms in intensive care unit patients. Each horizontal line represents a different patient included in the study (N=102) and each circle represents a separate stool sample. Conclusion Nearly 40% of ICU patients were colonized with VRE, ESBL-E, and/or CRE, although colonization duration was generally limited, possibly reflecting antibiotic pressures and microbiome dynamics in critically ill patients. More research is needed to identify clinical, microbiome, and organism genomic factors that facilitate persistence and loss of colonization. Disclosures All Authors: No reported disclosures

Identification of a d - glycero - d - manno -Heptosyltransferase Gene from Helicobacter pylori

We have identified a Helicobacter pylori d-glycero-d-manno-heptosyltransferase gene, HP0479, which is involved in the biosynthesis of the outer core region of H. pylori lipopolysaccharide (LPS). Insertional inactivation of HP0479 resulted in formation of a truncated LPS molecule lacking an alpha-1,6-glucan-, dd-heptose-containing outer core region and O-chain polysaccharide. Detailed structural analysis of purified LPS from HP0479 mutants of strains SS1, 26695, O:3, and PJ1 by a combination of chemical and mass spectrometric methods showed that HP0479 likely encodes alpha-1,2-d-glycero-d-manno-heptosyltransferase, which adds a d-glycero-d-manno-heptose residue (DDHepII) to a distal dd-heptose of the core oligosaccharide backbone of H. pylori LPS. When the wild-type HP0479 gene was reintegrated into the chromosome of strain 26695 by using an "antibiotic cassette swapping" method, the complete LPS structure was restored. Introduction of the HP0479 mutation into the H. pylori mouse-colonizing Sydney (SS1) strain and the clinical isolate PJ1, which expresses dd-heptoglycan, resulted in the loss of colonization in a mouse model. This indicates that H. pylori expressing a deeply truncated LPS is unable to successfully colonize the murine stomach and provides evidence for a critical role of the outer core region of H. pylori LPS in colonization.

Factors associated with acquisition of, or persistent colonization by, vaginal lactobacilli: role of hydrogen peroxide production.

To identify factors that predict sustained colonization by vaginal lactobacilli, microbiologic, behavioral, and demographic data were obtained from 101 nonpregnant women at baseline and at 4 and 8 months. A total of 272 isolates of lactobacilli were identified to the species level by use of whole chromosomal DNA homology to type strains. The predominant lactobacilli were the species Lactobacillus crispatus (38%) and L. jensenii (41%). Of 57 women initially colonized by H(2)O(2)-producing L. crispatus or L. jensenii, 23 (40%) remained colonized over 8 months, compared with 1 (5%) of 21 women colonized by other H(2)O(2)-producing species or by H(2)O(2)-negative strains (P=.01). Frequency of sexual intercourse (> or =1 sex act per week) was associated with loss of colonization with H(2)O(2)-producing lactobacilli (P=.018), as was antibiotic use (P< or =.0001). Other behavioral and demographic characteristics did not predict sustained colonization. The production of H(2)O(2) is closely linked with species and is a predictor for sustained long-term colonization of the vagina.