#4562 OUTBREAK OF RALSTONIA SPP AND BURKHOLDERIA SPP CATHETER-RELATED BLOODSTREAM INFECTION IN A HAEMODIALYSIS UNIT
Authors: Valente Mauro , Orecchioni Francesca , Brigante Fabiana , Moretti Maria Ilaria , D'errico Marcello , Moretti Marco , Tavio Marcello , Cotorruelo Maria Soledad Ferreiro , Pasquali Veronica , Marchi Massimo , Ranghino Andrea 
Published: June 2023

Abstract

Background and Aims
Ralstonia (RB) and Burkholderia (BB) species are environmental Gram-negative bacilli responsible for several nosocomial infections in immunocompromised or frail patients. RB and BB may contaminate medical devices because of their ability to survive in a biofilm and with low nutrient requests. Reports of infection outbreaks due to RB and BB are very few and only in sporadic cases, the source of contamination was identified. We describe here: i) how we managed an outbreak of bacteremia caused by RB and BB occurred in our dialysis unit, ii) what we have done to identify the source of infection and iii) the countermeasures we adopted to reduce the risk of new events.

Method
From 7 to 16 April 2021, 6 out of 39 (15.4%) hemodialyzed (HD) patients with a long-term indwelling central venous catheter (CVC) developed symptoms related to infection. Blood cultures revealed the presence of RB and BB. Thus, a prompt check of the blood cultures of all HD patients with CVC was performed. Blood samples were incubated in an automated microbial detection system (VIRTUO BIOMERIEUX) and subsequently, blood positive samples were inoculated in Chocolate and Columbia blood Agar plates. In addition, a microbiological analysis of disinfectants, drugs used in dialysis unit and samples collected from the reverse osmosis water unit (ROW) and from the ROW delivery line were performed. None of the samples obtained from the ROW and from the ROW delivery line resulted positive. Thus, a microbiological analysis of the biofilm attached on the loading pipes (LP) and on the loading plastic tubes (LPT) that connect the hemodialyzer consoles (HC) to the ROW delivery line were performed. Briefly, LTP were subjected to ultrasound sonication at 30-40 KHz (BactoSonic-Bandelin), to disrupt the bacterial biofilm. The material obtained from sonication was cultured. Bacteria was identified by an automated mass spectrometry (MALDI-TOF VITEK®MS, Biomerieux).

Results
Bacteremia due to RB and BB was confirmed in 7 out of 39 (17.9%) of the hemodialyzed patients with a long-term indwelling CVC. 1 out of 7 was asymptomatic. Baseline characteristics of the 6 symptomatic patients were: mean age 68±16 years; mean C-reactive protein 4.48±1.3 mg/dl; mean procalcitonin 13.27±11.07 ng/ml; mean body temperature 37.9±1.4°C. The antibiotic therapy was decided according to antibiogram and included meropenem and ciprofloxacin. CVC were removed in all infected patients between 6 to 11 days from the diagnosis. Concomitantly, a new one was placed. None of the HD patients with arterio-venous fistulae developed bacteremia. RB and BB were isolated in the biofilm of 11 out of 37 LPT. Thus, we modified the ROW delivery line in order to set up a scheduled chemical and physical disinfections of the ROW delivery line with the hemodialysis consoles connected avoiding the risk of new contamination of the LPT and loading pipes. Briefly, on alternate months the whole system that include ROW delivery line (PE-Xa Medical Device, Fresenius Medical Care), loading pipes, LPT and hemodialysis consoles are disinfected by hot water (90°C) produced by a water heater (AquaB plus HF, Fresenius Medical Care) and by chemical disinfectant, 5% peracetic acid according to the protocols made by the console fabricant. In addition, we added to the reverse osmosis system a filtration module of 0.01 μm (AquaUF, Fresenius Medical Care) prior to the ROW delivery line, Figure 1. Awaiting for the modification of the ROW delivery line, the patients with CVC were dialyzed using a portable water treatment unit. After more than 14 months from the modification of the whole system for production and delivery of ROW none of the hemodialyzed patients developed infection by RB and BB.

Conclusion
Our experience suggests that infection outbreak by unusual bacteria such as RB and BB could be successful treated using antibiotic therapy. Nevertheless, in dialysis unit the source of infection should be investigated in order to adopt the countermeasures necessary to reduce the risk of new infections.