Measurement of Klebsiella Intestinal Colonization Density to Assess Infection Risk
BackgroundKlebsiella pneumoniae and closely related species K. variicola and K. quasipneumoniae are common causes of healthcare-associated infections, and patients frequently become infected with their intestinal colonizing strain. To assess the association between Klebsiella colonization density and subsequent infections, a case-control study was performed. MethodsA multiplex qPCR assay was developed and validated to quantify Klebsiella (K. pneumoniae, K. variicola, and K. quasipneumoniae combined) relative to total bacterial DNA copies in rectal swabs. Cases of Klebsiella infection were identified based on clinical definitions and having a clinical culture isolate and preceding or co-incident colonization isolate with the same wzi capsular sequence type. Controls were colonized patients without subsequent infection and were matched 2:1 to cases based on age, sex, and rectal swab collection date. Quantitative PCR (qPCR) from rectal swab samples was used to measure the association between relative abundance (RA) of Klebsiella and subsequent infections. ResultsKlebsiella RA by qPCR highly correlated with 16S sequencing ({rho}=0.79; P <.001). The median Klebsiella RA in the study group was 2.6% (interquartile range (IQR) 0.1-22.5, n=238), and was higher in cases (15.7%, IQR 0.93-52.6%, n=83) than controls (1.01%, IQR 0.02-12.8%; n=155; P <0.0001). After adjusting for multiple clinical covariates using inverse probability of treatment weighting, subjects with a Klebsiella RA > 22% had a 2.87-fold (1.64-5.03, P =0.0003) increased odds of infection compared to those with lower colonization density levels. ConclusionsMeasurement of colonization density by qPCR could represent a novel approach to identify hospitalized patients at risk for Klebsiella infection. ImportanceColonization by bacterial pathogens often precedes infection, and offers a window of opportunity to prevent these infections. Klebsiella colonization is significantly and reproducibly associated with subsequent infection, however factors that enhance or mitigate this risk in individual patients are unclear. This study developed an assay to measure the density of Klebsiella colonization, relative to total fecal bacteria, in rectal swabs from hospitalized patients. Applying this assay to 238 colonized patients, high Klebsiella density defined as >22% of total bacteria, was significantly associated with subsequent infection. Based on widely available polymerase chain reaction (PCR) technology, this type of assay could be deployed in clinical laboratories to identify patients at increased risk of Klebsiella infections. As novel therapeutics are developed to eliminate pathogens from the gut microbiome, a rapid Klebsiella colonization density assay could identify patients who would benefit from this type of infection prevention interventions.