Epidemiology of Raoultella species in the context of human infections: a 10-year retrospective study in a tertiary-care hospital in Hungary

Introduction: Raoultella species are Gram-negative non-motile, aerobic, oxidase-negative and catalase-positive rods that are members of the Enterobacterales order that are infrequently described as significant pathogens in human disease. Objectives of the study: To report the incidence and the susceptibility levels of Raoultella species from clinical samples at a tertiary-care center in Hungary, during a 10-year study period (2008–2017). Method: Data collection was performed electronically by searching the records of the laboratory information system (LIS), regarding the samples with significant colony counts for Raoultella spp. Results: N=40 individual Raoultella isolates were identified (4.0±2.8/year, range: 0–9 isolates; highest in 2015, lowest in 2010 and 2011). Raoultella species were isolated from the following sample types: urine (catheterized and midstream): n=18, blood cultures: n=12, stool: n=6 and abscesses: n=4. 36 out of 40 isolates were R. ornithinolytica , while the remaining n=4 were R. planticola . All of the tested strains were susceptible to the group of β -lactam antibiotics. Conclusion: Raoultella species should be considered as emerging pathogens in the context of human infections, especially in older individuals in people with severe immunosuppression. The results suggest that in our local settings, there was-on average-one isolation of Raoultella every three months from various clinical samples and β -lactams may be considered safe choices for empiric therapy.