Penicillin skin testing

TABLE 51-3. Procedure for Performing Penicillin Skin Testing... 

In a patient with a positive penicillin skin test or a history of immediate hypersensitivity to penicillin, vancomycin is the agent of choice. Vancomycin, however, kills S. aureus slowly and is generally regarded as inferior to penicillinase-resistant penicillins for MSSA. Penicillin-allergic patients who fail on vancomycin therapy should be considered for penicillin desensitization. 

In penicillin-allergic patients, oral or parenteral clindamycin may be used. Alternatively, a first-generation cephalosporin such as cefazolin (1 to 2 g IV every 6 to 8 hours) may be used cautiously for patients who have not experienced immediate or anaphylactic penicillin reactions and are penicillin skin test negative. In severe cases in which cephalosporins cannot be used because of documented methicillin resistance or severe allergic reactions to /1-lactam antibiotics, IV vancomycin should be administered. 

The incidence of nonallergic ampicillin eruptions is 40 to 100% in patients with concomitant Epstein-Barr virus (mononucleosis), cytomegalovirus, acute lymphocytic leukemia, lymphoma, or reticulosarcoma. Nonallergic penicillin-associated rashes are characteristically morbilliform (symmetrical, erythematous, confluent, maculopapular) eruptions on the extremities. The onset of typical nonallergic eruptions is more than 72 hours after (3-lactam exposure. The mechanism for the nonurticarial ampicillin rash is not known and is not related to IgE or type I hypersensitivity. Penicillin skin tests are not useful in the evaluation of nonurticarial ampicillin rashes. Patients with a history of nonurticarial ampicillin rashes may receive other (3-lactam antibiotics without greater risk of subsequent serious allergic reactions. 

TABLE 16.6 Comparison of Allergy History with Penicillin Skin Test Results ... 

There was a high degree of cross-reactivity between imipenem determinants, analogous to the penicillin determinants in penicillin-allergic patients. Nine of twenty patients with positive penicillin skin tests had positive skin reactions to analogous imipenem determinants (40). In view of this appreciable cross-reactivity, imipenem should not be given to patients with penicillin allergy. 

Gadde J, Spence M, Wheeler B, Adkinson NF Jr. Clinical experience with penicillin skin testing in a large inner-city 188. STD clinic. JAMA 1993 270(20) 2456-63. 

Patients with a history of a reaction to penicillin are advised not to receive cephalosporins if they can be avoided. Patients who have negative penicillin skin tests or experienced only mild cutaneous reactions, such as macu-lopapular rashes, have a low risk of serious reactions to cephalosporins. 

Other /3-lactam derivatives (e.g., monobactams and carbapen-ems) have been studied for potential cross-reactivity with peniciUms. In vitro and in vivo studies have demonstrated that aztreonam only weakly cross-reacts with penicillin and that it may be administered safely to most patients who are peniciUin-allergic. In contrast, there is considerable cross-reactivity between imipenem (a carbapenem) and penicillin. Therefore, imipenem (and other carbapenems) should not be administered to patients who have positive penicillin skin tests. 

Immediate hypersensitivity reactions to penicillin are rare after a properly performed negative skin test when both major and minor determinants are used. Dermatologic reactions occur in 1% of skin-test-negative patients. A negative penicillin skin test indicates... 

Macy E, Mangat R, Burchetts RJ. Penicillin skin testing in advance of need Multiyear follow-up in 568 test result-negative subjects exposed to oral penicillins. J Allerg CUn limnunol 2003 111 1111-1115. 

If a patient has a mild, delayed allergy to penicillin, first-generation cephalosporins (such as cefazolin) are effective alternatives, but they should be avoided in patients with a history of immediate-type hypersensitivity reactions to penicillins (see Table 109-6). The potential for a true immediate-type allergy should be assessed carefully, and a penicillin skin test should be conducted before giving antibiotic treatment to any patient claiming an allergy. 

Wong, B. B., Keith, P. K, Waserman, S. (2006 Aug). Clinical history as a predictor of penicillin skin test outcome. Annals of Allergy, Asthma (s Immunology Official Publication of the American College of Allergy, Asthma, (s Immunology, 97(2), 169—174. 

Immunologic Of 85 patients with a history of penicillin allergy and positive penicillin skin tests 5 (6%) had an adverse drug reaction to a cephalosporin compared with 5 (0.7%) of 726 patients with a history of penicillin allergy but negative penidllin skin tests [7. Presumed IgE-mediated adverse reactions to the cephalosporins occurred in 2 (2%) of the former compared with only 1 (0.1%) of the latter. 

Park MA, Koch CA, Klemawesch P, Joshi A, Li JT. Increased adverse drug reactions to cephalosporins in penicillin allergy patients with positive penicillin skin test. Int Arch Allergy Immunol 2010 153 (3) 268-73. 

Lin E, Saxon A, Riedl M. Penicillin allergy value of including amoxicillin as a determinant in penicillin skin testing. Int Arch Allergy Immunol 2010 152(4) 313-8. 

Allergic recognition by some patients of side chain determinants highlights the importance of including different individual peniciUins in the battery of penicillin skin test reagents. 

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