To those users who desire to use a live, cultured organism as a positive control for the RedLine Alert (TM) test, in addition to or instead of the positive control antigen provided with the RedLine Alert kit, we recommend the use of B. anthracis Sterne strain.
B. anthracis Sterne is an avirulent, attenuated strain (i.e., It contains the pXO1 virulence plasmid but lacks the pXO2 virulence plasmid; both plasmids are required for virulence.). When used as a positive control, the Sterne strain is not subject to the requirements of 42 CFR Part 73 and 9 CFR Part 121 and is exempt from the list of select biological agents: http://www.selectagents.gov.
The avirulent Sterne strain may be obtained from the Colorado Serum Company (Denver, Colorado) as their Anthrax Spore Vaccine, Catalog No. 19102: http://www.colorado-serum.com Phone: 303-295-7527 or 800-295-7527; FAX: 303-295-1923
Clinical laboratories should fax order requests on the letterhead of their organization when requesting the Anthrax Spore Vaccine.
As an alternative to the use of B. anthracis Sterne, it is also possible to use B. cereus ATCC 7064, which is partially cross-reactive in the RedLine Alert Test.
The advantages of using B. cereus ATCC 7064 as a positive control are (1) it is readily available from the American Type Culture Collection (ATCC) and (2) since B. cereus is hemolytic, the use of B. cereus ATCC 7064 as a live positive control would serve as a safeguard that the positive control in this case (i.e., hemolytic B. cereus ATCC 7064) could never be confused with an actual positive sample (i.e., non-hemolytic B. anthracis ). http://www.atcc.org/
A further advantage of using B. cereus ATCC 7064 as a positive control is that, since this organism exhibits only partial cross-reactivity with the RedLine Alert test, the intensity of the positive line in the "S" window of the RedLine Alert cassette produced from testing a 1-2mm colony of B. cereus ATCC 7064 will not be as strong as a comparable positive line produced by testing a similarly sized 1-2mm colony of B. anthracis . The positive line produced by B. cereus ATCC 7064 will typically appear as a "low positive", as described in the package insert.
NOTE: In no case should a B. cereus strain other than ATCC 7064 be used as a positive control. Most isolates of B. cereus give a negative result in the RedLine Alert test and would not be suitable as a positive control.