2006 OPEN FORUM Abstracts
AN INDEPENDENT ANALYSIS OF POSSIBLE PATIENT RALSTONIA COLONIZATION AND INFECTION BY VAPOTHERM
Wesley M. Granger, PhD, RRT, Jonathan B. Waugh PhD, RRT
University of Alabama at Birmingham, Birmingham,
Alabama
Introduction: An independent analysis was conducted using data
submitted to Vapotherm, Inc., as part of an investigation regarding a recent
FDA Preliminary Public Health Notification concerning reported Ralstonia
cultured from a respiratory gas administration device at several hospitals. The
purpose of this analysis was to investigate the possible relationship between
Vapotherm use and the reported patient colonization and infection with Ralstonia.
Methods: We were allowed independent access on a consultant basis
to the data reported on Ralstonia
cultures to the company. We performed an analysis of reported positive Ralstonia cultures from patients and a
possible connection to Vapotherm device use.
Results: The reports indicate that 35 of 38 patients with positive
cultures were exposed to Vapotherm. Based on MDR our analysis reveals that only
5.8% of the positive patient cultures received Vapotherm as the only
respiratory therapy modality. Most of the patients had been intubated and on
mechanical ventilation before being placed on Vapotherm therapy. Further
analysis reveals that 1 patient was a Cystic Fibrosis patient who may have had
pre-existing infection not related to Vapotherm therapy. A 2005 multi-center
analysis of Ralstonia in cystic
fibrosis patients indicated that 46% of the Ralstonia
colonizations and infections were by R.
mannitolilytica (JCM 43(7):3463-3466). A recent CDC analysis using cluster
analysis statistics identified the "Outbreak Species" as Ralstonia mannitolilytica and stated that "strains from 10 states
were highly related" based on pulsed-field gel electrophoresis (PFGE). The CDC
defines this as similarity values of 77% or higher. Other published studies
indicate that similarities are not significant unless they show 90% or greater
values and then only indicate that they are the same strain and not necessarily
are from a common contamination source. Our analysis of the banding patterns
showed strains from only 5 states with a > 90% pattern similarity by cluster
analysis as reported by the CDC. Other
outbreak analyses in the literature using PFGE techniques on common source
contaminations show identical banding patterns and not just similar patterns.
Discussion: A study in 2005 (AEM 71(8):4690-4694) has questioned the
use of cluster analysis in evaluating banding patterns because cluster analysis
tends to show artificially high levels of similarity even between strains that
should not be very similar. They suggest the use of discriminant function
analysis as a more appropriate statistical analysis of similarities. As a
result of this information it is very difficult to determine if the identified
organisms are from a common source and therefore may not be directly linked to
Vapotherm therapy.
Conclusions: (1).
Less than 6% of the Ralstonia
cultures reported as positive were in patients who had received only Vapotherm
therapy. (2). Few if any of the reported 8 infections could be directly related
to the use of Vapotherm. (3). The result of the analysis using PFGE does not
show a common source of colonization by Ralstonia
mannitolilytica but only proves that these are all the same, most common,
species that might be expected in hospitals where cystic fibrosis patients are
treated.