Outbreak of Ralstonia pickettii bacteraemia in patients with haematological malignancies and haematopoietic stem cell transplant recipients

Abstract number: P1772

Mikulska M., Alberti M., Durando P., Molinari M.P., Van Lint M.T., Bregante S., Dominietto A., Raiola A.M., Del Bono V., Icardi G., Orengo G., Bacigalupo A., Viscoli C.

Objectives:Ralstonia pickettii is a non-fermenting Gram-negative rod commonly found in soil and moist environments. It is rarely isolated from clinical specimens or associated with infections, although blood stream infections (BSI) have been reported.

Methods: We describe a series of 11 R. pickettii BSI occurring over a period of 3 months (3/06/08–19/08/08) in 10 patients with haematological malignancies or after haematopoietic stem cell transplant (HSCT). Of them, 9 were cared for in the HSCT Unit, both in inpatient and outpatient facilities, and 1 was admitted for chemotherapy to another haematology unit in the same hospital.

Results: Clinical and microbiological features of the patients are shown in Table 1.

32 isolates were recovered from blood and 1 from a catheter tip. All patients had a central venous catheter at the time of BSI. The isolates were susceptible to aminoglycosides, fluoroquinolones, 3rd and 4th generation cephalosporins, piperacillin/tazobactam and carbapenems, and resistant to aztreonam.

In 5/11 BSI, the patients had a full-blown sepsis syndrome, while the other 6 episodes were free of symptoms, with no increase in C-reactive protein. All the patients received intravenous antibiotic therapy with cephalosporins or meropenem. The symptomatic patients improved and blood cultures became negative after a median of 2 days (range: 1–18). Six patients had the central venous catheter removed and 1 tip culture was positive for R. pickettii, 1 for K. pneumoniae and 3 were negative. No patient died due to R. pickettii BSI; 1 patient died of other causes (cardiomyopathy).

Epidemiological and microbiological investigations were undertaken and environmental samples, together with samples of several potential contaminated substrates (chlorhexidine, sterile saline and water, glucose and heparin solutions, hand-washing antiseptic soap) were cultured. Additionally, all the existing hygiene and infection control procedures were reviewed and actively monitored. All the cultures resulted negative for R. pickettii.

Conclusion: We report successful treatment and control of an outbreak of R. pickettii BSI in a HSCT Unit. Although R. pickettii is a pathogen with low intrinsic virulence and it might be a contaminant of blood cultures, it should not be overlooked when it is repeatedly recovered from sterile body fluids, especially in immunocompromised hosts who lack both classical signs and symptoms of the sepsis and full capacity to fight infections.

Table 1. Clinical and microbiological features of patients with Ralstonia pickettii bacteraemia