Pseudomonas pickettii (Biovar VA‐II): a rare cause of bacteremias in haematologic patients

To the Editor: Pseudomonas pickettii (P. pickettii) is a rare nonfermentative, aerobic, gram-negative bacterium belonging to the rRNA group II of Pseudomonas, which also includes Pseudomonas pseudomallei, Pseudomonas gladioli and Pseudomonas cepacia, that are usually pathogenic for plants and animals (1). P. pickettii in nature is isolated from water environments and appears to be relatively less virulent than the other Pseudomonas species. The incidence of human infections is very low, with only rare cases reported in literature, usually described as nosocomial infections (especially bacteremias) linked to contaminated injectable solutions (1–6). We report here a rare case of P. pickettii epidemic bacteremia that occured in our Department of Hematology. During a 6-month period (from October 1996 to March 1997) 20 bacteremias of P. pickettii were identified in 20 different patients (15 male, 5 female, median age 52 yr, range 26–72 yr) with hematologic malignances. Fifty-five percent (11/20) of patients had an absolute neutrophil count above 1r10/l at onset and during P. pickettii bacteremia; only 45% (9/20) were neutrophenic; 95% (19/20) of patients had venous catheters (16/19 a central venous catheter, 2/19 a peripheral and a central venous catheter, and 1/19 a peripheral venous catheter). In all patients the infection evolved positively without septic shock or death. No risk factors were identified in patients with bacteremia compared to a control group without bacteremia hospitalized in the same period. Apart from blood (emocoltural sets) P. pickettii was also isolated from brushing liquid (sodium chloride 0.9%) of two bone marrow bags, immediately after reinfusion; microbiologic examination of bone marrow before brushing the bags was negative. All nosocomial bacteremias were due to only one P. pickettii strain, identified by the API20NE gallery (Bio Merieux) and confirmed by a gas–liquid chromatographic system (7, 8). The biovariant Va-2 of P. pickettii was identified by negativity of maltose, mannitol and lattose tests according to Pickett (Table 1) (9). A disc sensitivity test for antibiotics (the Kirby–Bauer test) showed resistance to amikacin, gentamicin, netilmycin, tobramicin, ampicillin and ceftazidime and sensitivity to piperacillin, piperacillin/tazobactam, cefotaxime, cefoxitin, ciprofloxacine and imipenem/ cilastatine. In order to identify the source of infections culture specimens were obtained from: (a) all ward environments (swabs from the ventilation system, showers, bidets, taps, wash-basin drains; (b) all infusive solutions (more than 50 samples were taken, at random, from bottles of ‘‘sterile’’ physiologic, glucosate and electrolytic solutions and of distilled water for injection); (c) all detergents and disinfectants (betadine, clorexidine); (d) emocoltural sets; (e) blood and platelet transfusions; (f) patients’ skin (swabs); (g) needles of central venous catheters. The samples of infusive solution taken to detect possible contamination with P. pickettii, were aseptically removed, concentrated by filtration and inoculated in blood agar. Unfortunately the source of infection was not identified. However, in order to