Penicillin is one of the most commonly used beta-lactam antibiotics. It inhibits the action of enzymes required for cross-linking of peptidoglycans in the bacterial cell wall, thus weakening the bacteria’s ability to maintain an osmotic gradient, which results in cell lysis. Despite its wide-usage, it also is responsible for a sizeable amount of adverse drug reactions (ADRs). This reaction can vary from a mild rash to life-threatening symptoms, such as anaphylaxis.
Penicillin hypersensitivity is strongly associated with the presence of the HLA-B*55:01 allele in those with European ancestry. Due to the unpredictable and potentially severe nature of adverse drug reactions, it is recommended to consider testing for the presence of HLA-B*55:01 allele prior to initiating penicillin therapies. This test may also be used to further support a self-reported penicillin allergy. It is important to note that absence of the HLA-B*55:01 allele does not exclude a patient from possessing sensitivity to penicillin.