In the literature, there is a limited number of case reports of Paenibacillus urinalis in adults. However, there is no information available regarding P. urinalis infection in children and infants. Paenibacillus growth in blood and sterile site cultures is generally considered contamination; it is unclear whether P. urinalis is the true cause of the infection. In this retrospective study, we aimed to clinically evaluate P. urinalis growth in the blood cultures of children at a tertiary referral hospital over a 5.5-year period, with identification performed using the MALDI-TOF MS method. A total of 170 hospitalized children showed P. urinalis growth in sterile site cultures (blood: 162; catheter: 7; CSF: 1), with forty percent of all growth occurring in only three wards (neonatal intensive care unit, hematology, oncology). Of 170 cultures, 5 (2.9%) showed further P. urinalis growth in control cultures, which could be considered significant. In cases with a second culture, the average growth time (time to positivity) was relatively short, at 24 + 7 h (mean + SD, min-max: 17–33 h). No mortality was observed in any case. Evaluations were conducted by the Hospital Infection Control Committee to determine the source of P. urinalis contamination. P. urinalis growth was detected in 33% of samples taken from clean, packaged linens before use; 53% of ambient air cultures; and 65% of hospitalized patient skin swabs. In conclusion, P. urinalis blood culture growths are primarily considered contamination; however, these growths should be carefully evaluated in risk groups (especially those admitted in neonatal intensive care units and young infants less than 3 months old). In hospitalized patients, clustered growths may be influenced by environmental (such as clean packaged linens and ambient air) and skin colonization.

Paenibacillus is abundant in nature and environmental samples, and generally does not contain invasion factors. Therefore, Paenibacillus growth in blood is generally considered a contamination. However, it can lead to infection in children and adults, particularly in at-risk groups. In many of these cases, it may not be clear whether Paenibacillus is the true cause of the infection. The literature reports a limited number of cases of Paenibacillus urinalis in adults. However, there is no information available regarding P. urinalis infection in children and infants. This retrospective study aimed to clinically evaluate P. urinalis growth in blood cultures of children in a tertiary referral hospital over a 5.5-year period. A total of 170 hospitalized children showed P. urinalis growth in blood cultures (blood; 162, catheter; 7, CSF; 1). Identification was performed using the MALDI-TOF MS method. Forty percent of all P. urinalis growths occurred in only three wards (neonatal intensive care unit, hematology, oncology). Of 170 cultures, 5 (2.9%) showed P. urinalis growth again in control cultures, which was considered significant. In cases with a second culture, the average culture growth time was 24+7 hours (mean + SD, min-max; 17-33 hours). No mortality was observed in any case. Evaluations were conducted under the responsibility of the Hospital Infection Control Committee to determine the source of P. urinalis contamination. P. urinalis growth was detected in 33% of samples taken from clean, packaged linens before use, 53% of ambient air cultures, and 65% of skin swabs of the hospitalized patients. In conclusion, P. urinalis blood culture growths are primarily considered contamination. However, these growths should be carefully evaluated in risk groups. In hospitalized patients, clustered growths may be influenced by environmental and skin colonization.