Detection of IgE antibodies to bacitracin using a commercially available streptavidin-linked solid phase in a patient with anaphylaxis to triple antibiotic ointment.

Background: Bacitracin is a commonly used topical antibiotic that has on occasion been reported to cause anaphylaxis. Evidence of the role of bacitracin specific IgE in such reactions has been demonstrated by skin testing. Because of the potential for provoking a systemic reaction by skin testing, it would be advantageous to develop an in vitro test for bacitracin specific IgE.

Objective: To report our experience coupling bacitracin to a solid phase and using it to detect specific IgE to bacitracin by fluorescent enzyme immunoassay.

Methods: A patient with a history of recurrent anaphylaxis that developed after application of triple antibiotic ointment to an open wound underwent skin testing with triple antibiotic ointment. Bacitracin was biotinylated and coupled to streptavidin ImmunoCAPs. IgE against bacitracin in the patient's serum was detected by fluorescent enzyme immunoassay.

Results: Topical application of triple antibiotic ointment to intact skin produced a 7 X 8-mm wheal with pseudopods. IgE against bacitracin was detected using biotinylated bacitracin-streptavidin ImmunoCAPs at a level of approximately 0.6 KUA/L and confirmed with ImmunoCAPs using direct coupling of bacitracin to the solid phase.

Conclusions: We demonstrate the presence of IgE antibodies to bacitracin in a patient with anaphylaxis to triple antibiotic ointment using a recently described procedure for producing custom allergen solid phases for immunoassay.