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Characteristics of 12 Case-patients With Bacteremia Caused by Alcaligenes xylosoxidans*

Figure 1.  

Scanning electron micrograph of lumen of segment of central venous catheter removed from an asymptomatic patient. Biofilm contains rod-shaped bacteria (Alcaligenes xylosoxidans) in association with fibrinlike material on the catheter surface.

Figure 2.  

Pulsed-field gel electrophoresis of isolates from patients with Alcaligenes xylosoxidans bloodstream infection. Lane 1, laboratory standard; lanes 2 and 6, community strains of A. xylosoxidans; lanes 3–5 and 7–13, outbreak strains; lane 14, central venous catheter (CVC) port biofilm outbreak strain; lane 15, CVC port outbreak stain.

Alcaligenes xylosoxidans Bloodstream Infections in Outpatient Oncology Office: Results



A total of 12 patients with A. xylosoxidans bloodstream infection were found: 9 from the retrospective case–control study and 3 from the prospective study ( Table ). All 12 were immunocompromised. Their ages ranged from 41 to 79 years (mean 65.8 years), and 10 (83.3%) were female. Case-patients had differing underlying diagnoses and chemotherapy regimens. Casepatients had had fevers, chills, and/or rigors within minutes to days after an infusion through their CVC. Several case-patients had multiple episodes of fever and chills during and immediately after visits to Office B when their CVC was accessed for blood collection, chemotherapy, or routine flushes. For some, these symptoms were attributed to possible side effects of chemotherapy. All casepatients had visited Office B from November 12 through December 18, 2001. Case-patient 1 was hospitalized from October 12 through November 10, 2001, and had visited Office B for daily collection to monitor neutropenia from November 13 through 19, 2001. Patients with A. xylosoxidans bloodstream infection were treated with antimicrobial drugs and CVC removal. Available records showed case-patients were treated with piperacillin/tazobactam; 1 case-patient who was allergic to penicillin was treated with aztreonam. One patient died from underlying malignancy (end-stage pancreatic cancer).

Matched Case–Control Study

Of the 9 case-patients identified, 7 who had clear onset date of bloodstream infection symptoms were selected for the case–control study. Case-patients were younger than controls (mean age 63.5 years [range 41–73 years] and mean age 73.2 years [range 35–89 years], respectively; p = 0.047). Case-patients were significantly more likely to have a CVC than controls. Matched case–control analysis showed that all 7 case-patients versus 4 of 47 control patients had a CVC at the time of illness onset (p <0.0001). The 2 other case-patients not included in the case–control study also had CVCs. Patients with CVCs received heparin and saline flushes before and after the CVC was used for blood collection or infusions. No records documented when each of the Office B nurses accessed the CVCs. Patients without CVCs who needed only blood collection for testing did not receive any flushes; however, those without CVCs who needed blood tests before receiving an infusion received a heparin and saline flush after a peripheral intravenous line was placed. Case-patients and controls did not have statistically significant differences in peripheral leukocyte counts, intravenous medications administered, types of chemotherapy received, or underlying diseases.

Prospective Cohort Study

In February 2002, 29 patients with CVCs had blood collected for culture. Of the 3 (10%) who had positive culture results for A. xylosoxidans, chart review showed that 2 had been intermittently symptomatic ( Table ).

Environmental Investigation

Cultures from available open solutions in the oncology office, collected 6 weeks after the initial cluster of A. xylosoxidans–positive blood cultures, and environmental cultures did not grow A. xylosoxidans. A sample from a sterile saline bottle that was open in the infusion room was positive for Bacillus circulans, and a tap water sample was positive for Moraxella spp.

Infection Control Practices and Procedures

Office B had 10 patient examination rooms and a separate, large, open infusion room where several patients could receive chemotherapy. The infusion room contained a hood and sink for preparation of intravenous medication. Of the 4 staff members at Office B who regularly accessed CVCs; inserted peripheral intravenous catheters; collected blood; and prepared or administered chemotherapy, flushes, or intravenous medications, only 1 was a registered nurse who had a California state license. The 3 nonlicensed staff members were reported to have received nursing training in their native country but did not have documented formal training or education. One nurse wore artificial fingernails but had removed them before hand culture samples were collected; thus, the fingernails were unavailable for culture. The following breaches in infection control were noted: intravenous catheters were inserted by persons not wearing gloves; unlabeled, prefilled syringes were stored in the hood; no documentation of hood cleaning was found; open, multidose heparin vials and saline bottles, some undated, were found throughout the facility; nonhygienic material was stored in the chemotherapy medication preparation hood; and failure to wash hands between patients was noted. No pharmacists were employed at Office B. No documentation of staff training and evaluation for chemotherapy preparation or infection control competency was available.

CVC Biofilm Studies

Scanning electron microscopy of the CVC showed a biofilm that contained rod-shaped bacteria in association with fibrinlike material on the catheter surface (Figure 1). A pure bacterial culture recovered from the CVC lumen was identified as A. xylosoxidans.

Molecular Studies

A. xylosoxidans blood culture isolates from case-patients were indistinguishable by PFGE analysis (Figure 2); in contrast, 3 A. xylosoxidans isolates from a local reference laboratory had different PFGE patterns. The isolate from the CVC biofilm matched the A. xylosoxidans bloodstream infection outbreak strain.

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