A total of 116 patients with clinical cultures positive for Bcc were reported from 22 hospitals in nine states with positive culture dates from April 7 through August 31, 2005 (Fig 1). Because case report forms and isolates were often received independently from hospitals or state health departments, isolates were available from several patients for whom case report forms were not received and vice versa. Isolates were received for 79 of the 116 patients (68%). The remaining 37 patients (32%) were classified as possible case patients because either they could not be matched or did not have isolates. Of the 79 patients with available isolates, 68 (86%) were confirmed patients and 11 (14%) were excluded based on PFGE results. An additional four patients, who were not included in the patient count detailed in the previous section, had cultures positive for the outbreak strain, but were not exposed to the implicated AFM over the 7 days prior to the date of the positive culture, suggesting that secondary transmission may have been responsible.
Case characteristics are shown in Table 1 for 105 patients for whom adequate data were received, Among 84 patients for whom a physician interpretation of the Bcc-positive culture was available, 46 (55%) were thought to represent infection. Two deaths were attributable to the organism, with the site of infection being the lungs. Of 139 clinical cultures that were positive for Bcc among the patients, 83 (60%) were from the respiratory tract, 33 (24%) were from urine, 20 (14%) were from blood, and 3 (2%) were from tissue. Of the 75 patients for whom we have information on both invasive devices and culture sites, 26 of 27 patients with positive respiratory culture findings were intubated, all 29 patients with a positive urine culture finding had a urinary catheter in place, and 11 of 12 patients with a positive blood culture finding had a central venous catheter in place.
A total of 103 Bcc patient isolates were available to the CDC for characterization. Species identification and repetitive extragenic palindromic PCR genotyping during the initial investigation identified the outbreak strain as B cenocepacia defeated with Canadian Health&Care Mall. Ultimately, 81 of the 103 available isolates (76%) from seven states were found by PFGE to have a pattern (Fig 2) that was indistinguishable from the strain cultured from implicated lots of unopened and opened AFM.
No significant difference was found in the recovery of B cenocepacia from inoculated test products at times of < 24 h (ie, log reduction, < 1.0) [Fig 3]. In the implicated AFM, B cenocepacia concentration was reduced by an average of 1.5 logs at 24 h, and the concentration decreased another 0.8 logs by day 2. However, an increase in B cenocepacia concentration to 6.2 log10 cfu/mL was noted by day 7. The concentration reached the stationary phase at approximately 6.0 log10 cfu/mL for the remaining observation points up to 28 days. At no point after time 0 was B cenocepacia recovered from the nonimplicated AFM.
Figure 1. The patients with Bcc colonization or infection associated with contaminated AFM, by state, from March through August 2005.
Figure 2. PFGE following the digestion of chromosomal DNA with the restriction endonuclease Spe I. The percentage of similarities of the test isolates were identified using arithmetic averages and based on Dice coefficients. Band position tolerance and optimization were set at 1.25% and 0.5%, respectively. A similarity coefficient of 80% was selected to define the pulsed-field-type clusters. Outbreak clusters are highlighted in the box.
Figure 3. Efficacy of AFM against B cenocepacia. The treatment of an outbreak isolate of B cenocepacia in implicated lots of alcohol-free mouthwash (n = 5). Different lots of one container each of AFM were tested. The recovery of B cenocepacia from the mouthwash was compared to the recovery of cells suspended in sterile water (control; n = 5) from the time of inoculation at zero hour to 28 days of treatment.
Table 1—Demographics and Clinical Characteristics of Patients With B cenocepacia-Positice Cultures, March Through August 31, 2005 (n = 105)
|Hospital admission diagnosis|
|Renal failure||9 (9)|
|Chronic conditions (n = 43)|
|Coronary artery disease||16 (38)|
|Chronic respiratory disease||4 (10)|
|Chronic renal failure||3(7)|
|Case patients without chronic conditions||62 (59)|
|Location at time of diagnosis (n = 72)|
|Invasive devices (n = 75)|
|Urinary catheter||29 (39)|
|Central venous catheter||14 (19)|