Abstract

Bacterial infection and sepsis is a major cause of morbidity and mortality after hematopoietic stem cell transplantation. We report a case of Brevundimonas vesicularis bacteremia in a patient following mismatched related donor peripheral blood stem cell transplantation (PBSCT).

Case Report

The patient was a 36 year-old African American woman with a two year history of acute myelogenous leukemia (AML). She was initially treated with an induction chemotherapy regimen of Idarubicin and Ara-C with only a partial response. She required a second course of chemotherapy with the same agents to achieve a complete remission. She received two additional courses of consolidation chemotherapy with high dose Ara-C after achieving full remission to maintain her in remission for 7 months. At that point a bone marrow biopsy with flow cytometry revealed evidence of recurrent disease. Autologous PBSCT was considered due to lack of an allogeneic marrow donor. Autologous PBSCT was performed following standard conditioning with Busulfan and Cytoxan. Recurrence of AML was detected 6 months after autologous PBSCT and she underwent salvage chemotherapy with Etoposide and Mitoxantrone. One month later, she was in morphological remission but the cytogenetic analysis of the bone marrow was positive. Mismatched related donor PBSCT was performed. After her pancytopenia resolved she was discharged home. She was readmitted 45 days post transplant for evaluation of fever and cough of one day duration. On examination she was in respiratory distress with a respiratory rate of 30/min, temperature of 103°F, heart rate of 120 beats/min and a blood pressure of 75/40 mm Hg. Chest auscultation revealed bilateral diffuse crackles. Cardiac, abdominal and neurological examination was unremarkable. There were no indwelling intravascular devices. Two sets of blood cultures were obtained and she was started on empiric broad spectrum antimicrobial coverage including Vancomycin, Meropenem, Amikacin, Amphotericin B and Gancyclovir. The initial chest radiograph showed bilateral diffuse bilateral air-space opacities (Figure 1a). She developed severe hypoxemic respiratory failure requiring intubation and mechanical ventilation. She required vasopressor therapy for hypotension unresponsive to fluid resuscitation. A diagnosis of Septic Shock and Acute Respiratory Distress Syndrome (ARDS) was made. Repeat chest radiograph showed progression of her bilateral parenchymal infiltrates (Figure 1b).

Figure 1: a) Chest radiograph on presentation showing bilateral patchy air-space disease. b) Chest radiograph five hours later showing rapid progression of air-space disease. Also note that the endotracheal tube is in the right main bronchus.

Unfortunately the patient died less than 24 hours after presentation. Sputum and tracheal aspirate cultures grew only normal flora. The two aerobic blood cultures grew a gram-negative rod after 5 days of incubation. The organism was oxidase positive, fermented only glucose and esculin, and produced yellow pigment on blood agar. Brevundimonas vesicularis was identified by MicroScan NBPC30 system, which was resistant to Amikacin, Aztreonam, Cefepime, Ceftazidime, Ceftriaxone, Meropenem, Piperacillin-tazobatam, and Tobramycin. Intermediate activity was noted with Imipenem and Gentamicin. The organism was susceptible only to Ciprofloxacin and Ticarcillin-Clavulanate. We believe this case represents a case of B vesicularis bacteremia resulted in septic shock and ARDS. Although chest radiograph on admission showed patchy infiltrates consistence with pneumonia, we did not isolate the organism from sputum or tracheal aspirates. The source of bacteremia could not be identified.

Discussion

Brevundimonas vesicularis was formerly classified as a member of group IV of the genus Pseudomonas, and was called Pseudomonas vesicularis (1). This organism is a slender, motile, aerobic, non-sporulating non-fermenting gram-negative rod (1, 2). The organism was first described in 1954, when Busing et al cultured it from the seminal vesicle of a leech (3). Brevundimonas vesicularis has been isolated from specimens obtained from various environmental sources including shower hoses (4), hydrotherapy pools (5), bottled non-carbonated mineral water (6), soil (7), and reprocessed dialyzers (8). Interestingly, Brevundimonas species has been isolated from the Russian space laboratory Mir (9). The organism has also been isolated from human specimens. Otto et al in 1978 found five strains of B vesicularis, isolated from cervical cultures of patients with cervicitis. The Centers for Disease Control in 1984 reported a collection of clinical isolates of B vesicularis from blood, cerebrospinal fluid, urine, eye, wound, and vaginal cultures (10). Human infection with B vesicularis is rare and only a few cases have been reported in literature (Table 1) (1,2,3, 7, 11,12,13). There are also two reports of B vesicularis bacteremia outbreaks due to use of formaldehyde-reprocessed dialyzers (8). To our best of knowledge, this is the first report of B vesicularis Bacteremia after peripheral blood stem cell transplantation.

In conclusion, B vesicularis bacteremia can present as fulminant septic shock. This is the first reported case of B vescularis that is resistant to both Meropenem and Piperacillin-tazobactam. Although B vesicularis was resistant to ciprofloxacin in previously reported cases, in this case B vescularis was susceptible to ciprofloxacin. Since extensive data on antibiotic sensitivity of B vescularis is lacking, until more information is available ciprofloxacin should be considered in the antibiotic regimen in treatment of B vescularis bacteremia while awaiting antibiotic susceptibility results.

Table 1: Summary of clinical description of reported cases of Brevundimonas vesicularis infections in humans

Correspondence to

Bobbak Vahid, MD Thomas Jefferson University 1015 Chestnut Street, Suite M-100 Philadelphia, PA 19107 Tel: 215 955-6591 Fax: 215 955-0830 Bobbak.vahid@mail.tju.edu

References