Enterobacterales Infection after Intestinal Dominance in Hospitalized Patients

Intestinal domination by the Enterobacterales order of Gram-negative bacteria is associated with subsequent infection, but 16S rRNA gene sequencing is too costly and slow to be used in a clinical setting. This study aimed to develop a PCR-based assay to measure Enterobacterales density and validate it against 16S rRNA gene sequencing. Furthermore, this study measured the association between Enterobacterales dominance and subsequent infection. A matched case-control study of hospitalized patients who later developed bloodstream, urinary tract, or respiratory Enterobacterales infections (n=95) and patients who remained uninfected (n=189) demonstrated that Enterobacterales abundance was high in both cases and controls, and that an increased risk of infection depended on both the absolute and relative abundance of Enterobacterales as measured by one of the qPCR assays. This association still approached significance after adjusting for relevant clinical parameters. These results demonstrate that using qPCR to measure intestinal colonization dominance is feasible, indicate that hospitalized patients have high levels of Enterobacterales colonization, and suggest that both relative and absolute abundance may be associated with subsequent infection.