A two-component direct fluorescent-antibody assay for rapid identification of Bacillus anthracis

Emerg Infect Dis. 2002 Oct;8(10):1060-5. doi: 10.3201/eid0810.020392.


A two-component direct fluorescent-antibody (DFA) assay, using fluorescein-labeled monoclonal antibodies specific to the Bacillus anthracis cell wall (CW-DFA) and capsule (CAP-DFA) antigens, was evaluated and validated for rapid identification of B. anthracis. We analyzed 230 B. anthracis isolates; 228 and 229 were positive by CW-DFA and CAP-DFA assays, respectively. We also tested 56 non-B. anthracis strains; 10 B. cereus and 2 B. thuringiensis were positive by the CW-DFA assay, and 1 B. megaterium strain was positive by CAP-DFA. Analysis of the combined DFA results identified 227 of 230 B. anthracis isolates; all 56 strains of the other Bacillus spp. were negative. Both DFA assays tested positive on 14 of 26 aging clinical specimens from the 2001 anthrax outbreak investigation. The two-component DFA assay is a sensitive, specific, and rapid confirmatory test for B. anthracis in cultures and may be useful directly on clinical specimens.

MeSH terms

  • Animals
  • Anthrax / diagnosis
  • Anthrax / microbiology
  • Anthrax / veterinary
  • Antibodies, Monoclonal / immunology
  • Antigens, Bacterial / immunology
  • Bacillus anthracis / classification
  • Bacillus anthracis / immunology
  • Bacillus anthracis / isolation & purification*
  • Bacterial Capsules / immunology
  • Cattle
  • Cell Wall / immunology
  • Environmental Monitoring
  • Fluorescent Antibody Technique / methods*
  • Humans
  • Sensitivity and Specificity


  • Antibodies, Monoclonal
  • Antigens, Bacterial