Bloodstream Isolation of Klebsiella Pneumoniae in Adults Hospitalized with SARS-CoV-2 During the Omicron BA.5 Wave: A Retrospective Cohort Study

Background and Objectives: Secondary bloodstream infection in patients hospitalized with coronavirus disease 2019 (COVID-19) can lengthen admission and increase antimicrobial exposure, yet pathogen-specific evidence from the Omicron period is scarce. We examined how often Klebsiella pneumoniae was recovered from blood among adults admitted with SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) infection during the Omicron BA.5 wave, and which clinical features and outcomes accompanied it. Materials and Methods: This retrospective single-center cohort comprised 395 adults admitted in Timișoara, Romania, from 12 July to 25 September 2022. Patients with K. pneumoniae in blood culture were compared with all remaining patients, whether their cultures showed no growth or another pathogen. Groups were compared with the Mann–Whitney U and Fisher’s exact tests. The association between K. pneumoniae and a hospital stay of at least 14 days was estimated with Firth penalized logistic regression, adjusted for age, sex, and admission oxygen saturation. Results: Blood cultures grew K. pneumoniae in 16 patients (4.1%), another pathogen in 73 (18.5%), and nothing in 306 (77.5%). Median length of stay was 17.5 days (IQR (interquartile range) 9.8–25.2) with K. pneumoniae and 9.0 days (IQR 7.0–16.0) in the rest of the cohort (p = 0.006); a stay of at least 14 days occurred in 56.3% versus 28.0% (unadjusted OR 3.31, p = 0.022). The association persisted after adjustment (Firth adjusted OR 3.18, 95% CI 1.14–8.87; p = 0.027; maximum-likelihood estimate 3.25, 95% CI 1.16–9.12; p = 0.025). In-hospital death occurred in 1 of 16 exposed patients (6.3%) and in 61 of 379 others (16.1%; Fisher’s exact p = 0.485); with a single exposed death, the age- and sex-adjusted Firth estimate was imprecise (adjusted OR 0.48, 95% CI 0.04–2.21). Conclusions: K. pneumoniae bloodstream isolation was infrequent in this Omicron BA.5 cohort but was accompanied by a markedly longer hospital stay. Causality and an effect on mortality cannot be inferred: culture dates, place of acquisition, device exposure, and isolate susceptibility were not available, the untimed exposure is prone to immortal-time bias, and no non-COVID-19 comparator was studied. Prospective surveillance combining time-stamped microbiology with resistance phenotyping is needed.