Immune thrombocytopenia induced by beta-lactam antibiotics: Cross-reactions of responsible antibodies with other beta-lactam drugs.

BACKGROUND: Beta-lactam antibiotics are a relatively common cause of immune thrombocytopenia. Because the many beta-lactam drugs now in clinical use have structural similarities, when a patient experiences this complication the question of whether an alternative member of this drug family can safely be used often arises but there are little data available to guide this decision. STUDY DESIGN AND METHODS: Drug-dependent, platelet-reactive antibodies from 32 patients who experienced thrombocytopenia while being treated with a beta-lactam drug of the penam (piperacillin, etc.) or cephem (ceftriaxone etc.) groups were studied for serologic cross-reactivity with other drugs from these families using flow cytometry. Cross-reactions observed were analyzed for correlations with structural features of the drugs tested. RESULTS: Among 14 antibodies specific for penam drugs, five "strong" cross-reactions with other penam drugs were found. Among 18 antibodies specific for cephem drugs, 8 "strong cross-reactions were identified. Antibodies induced by penam drugs did not cross-react strongly with cephem drugs and vice versa. A strong correlation between cross-reactions and similar or identical R1 side groups of the beta-lactams studied was observed. DISCUSSION: The findings suggest that patients who experience immune thrombocytopenia while being treated with a beta-lactam of the penam group can safely be treated with a cephem drug and vice versa. If a patient is to be switched to another beta lactam within the same group, the likelihood of serologic cross-reactivity can be minimized by choosing an agent with a distinctly different R1 side group.

A Comprehensive Prospective Study of the Costs Associated With Evaluation of ß-Lactam Allergy.

BACKGROUND AND OBJECTIVE: Being labeled as allergic to penicillin (unverified ß-lactam allergy) can result in patients receiving broader-spectrum antibiotics than necessary that may be more toxic, less effective, and/or more expensive than alternative options. Objective: We aimed to evaluate the real costs of evaluating ß-lactam allergy. METHODS: We performed a prospective real-life observational study designed to evaluate all adult patients who consulted for suspected ß-lactam allergy over a 1-year period. Direct and indirect costs were systematically recorded. Direct health costs were calculated based on the number of visits and all additional and diagnostic tests performed, direct nonhealth costs based on the number of visits and the distance from their homes to the Allergy Department, and indirect costs based on absenteeism. RESULTS: A total of 296 patients with suspected allergy to ß-lactams were evaluated in our outpatient clinic from June 1, 2017 to May 31, 2018. Total direct health care costs were €28 176.70, with a mean (SD) cost of €95.19 (37.20). Direct nonhealth costs reached €6551.73, that is, €22.13 (40.44) per patient. Indirect health costs reached €20 769.20, with a mean of €70.17 (127.40). In summary, the total cost was €55 497.63, that is, a cost per patient of €187.49 (148.14). CONCLUSIONS: When all possible costs are taken into account, the evaluation of ß-lactam allergy is not expensive and can reduce future expense arising from unnecessary use of more expensive and less effective antibiotics.

Implementation of EMR-based standardized antibiotic desensitization protocols and its impact on providers.

Background: As desensitization protocols become more readily available and published, more institutions are implementing them and searching for ways to streamline the process. There have been no published studies to date on the effect that electronic medical record systems (EMR) have on the safety and efficiency of ß-lactam antibiotic desensitization. Objective: The purpose of this study was to evaluate the changes in workflow, efficiency, and medical errors after implementation of ß-lactam antibiotic desensitization. Methods: A collaborative effort between the Allergy/Immunology Division and the Pharmacy Department led to the creation and implementation of antibiotic desensitization order sets. Pre- and postimplementation of ß-lactam antibiotic surveys were sent to pharmacists and allergy/immunology fellows and attendings at a single-center tertiary care center. Results: There were only 26 valid respondents (12.3%) to both the pre- and postimplementation surveys. The percentage of respondents who thought that the time needed to prepare desensitization materials was < 4 hours increased from 23% to 77% (p < 0.001). The percentage of respondents who thought that the time needed to input electronic desensitization orders was < 1 hour increased from 19% to 54% (p = 0.002). The percentage of respondents who identified zero errors increased from 42% to 92% (p = 0.001). The perception of the overall desensitization process efficiency significantly increased (p < 0.001). Conclusion: Creation of standardized electronic ß-lactam antibiotic desensitization order sets significantly decreased the time taken to order and prepare materials and increased overall efficiency.

Drug-specific history, skin and in vitro tests can reduce the need for drug provocation tests in betalactam-hypersensitivity.

BACKGROUND: Many patients report questionable drug hypersensitivity reactions (DHR) to betalactam antibiotics. A workup is required for objectivation. Direct drug provocation tests (DPTs) omitting a prior allergy workup are increasingly recommended as the primary diagnostic approach. However, apart from the risk of severe side effects, DPTs often are a scarce resource in overloaded healthcare-systems. We investigated how many cases can be solved by drug-specific history, drug-specific IgE, and skin tests obviating the need for DPT. METHODS: We conducted a chart review in a retrospective cohort of 932 patients in an allergy outpatient centre from 2016 to 2017. Patients had been submitted to drug-specific history and specific IgE-, skin prick-, intradermal- and patch-tests with early and late readings with a series of penicillins and cephalosporins but DPTs were no option. RESULTS: Overall, positive in vitro and/or skin tests were found in 96/932 (10.3%) patients. Drug-specific IgE was detected in 40/932 (4.3%) patients, 61/787 (7.8%) patients had positive skin tests. In vitro tests to Pencillin V showed the highest rate of positivity 24/479 (5.0%) and early readings of ampicillin the highest amongst the skin tests (3/49, 6.1%). Immediate skin tests were more often positive than delayed ones (75:45). The combination of all parameters including drug-specific history solved 346/932 (37.1%) cases while 586/932 (62.9%) remained unresolved. Self-reported DHR could be less often confirmed in females and young children (p < 0.05). CONCLUSIONS: Testing with betalactams applying simple, cheap, and safe skin and blood tests can solve a third of DHR-cases on a high throughput scale.

Multiparametric Highly Sensitive Chemiluminescence Immunoassay for Quantification of ß-Lactam-Specific Immunoglobulin E.

ß-lactams (BLCs) are the most widely used antibiotics and consequently the most common cause of drug allergy in the world. The diagnosis of drug allergy is complex and represents a serious challenge that includes a wide variety of methods. In vitro tests are based on the immunological determination of allergen-specific IgE, but the tests in the market lack the required sensitivity and specificity. In addition, the large sample volume, long incubation times, and single-plex configuration have brought their use into question to complement the clinical information. Here, we report a chemiluminescence immunoassay (CLIA) for multiparametric quantification of specific IgE to penicillin G, penicillin V, amoxicillin, and piperacillin, using histone H1 as a carrier. The developed CLIA allowed the determination of BLC-specific IgE below 0.1 IU/mL, thus allowing identification of allergic patients with better sensitivity, using only 25 µL of a sample (serum). The immunoassay was successfully applied in a cohort of 140 human serum samples, showing good sensitivity (64.6%) as well as specificity (100%), which significantly improve the predictive character of existing BLC-allergy in vitro tests.

The negative predictive value of 5-day drug provocation test in nonimmediate beta-lactam allergy in children.

BACKGROUND: Extending the drug provocation test (DPT) period is recommended for patients with suspected nonimmediate beta-lactam antibiotic (BLA) allergy and negative DPT. No consensus has been reached regarding the duration of prolonged provocation. OBJECTIVE: We aimed to determine the negative predictive value (NPV) of the 5-day extended DPT. METHODS: Parents of patients with suspected nonimmediate mild cutaneous reactions with BLAs who had been subjected to 5-day DPT with culprit drugs were questioned by telephone interview about reexposure to the tested drug. Patients with reported reaction during reexposure were reevaluated. Skin tests and serum-specific immunoglobulin E (IgE) analysis were not performed before first DPT. RESULTS: A total of 355 patients had negative results in 5-day DPT. The median age at DPT was 4.2 years, and 52.9% were male. The families of 255 patients (72%) could be contacted. Of these 255 patients, 179 (70%) had used the same drug, and reactions were reported for 6 (3.4%) of those patients, who were subsequently reevaluated. Five of the 6 patients had DPT with amoxicillin-clavulanate and 1 with cefixime. When detailed history was taken, 2 of the 5 patients with amoxicillin-clavulanate reaction were found to have used the drug unintentionally after their reaction to reexposure and did not have any symptoms. One of the patients underwent allergy workup and tested negative, and the other 2 refused the test. The patient with reported cefixime reaction underwent repeated allergy workup and tested negative. Therefore, the NPV of 5-day prolonged DPT was 98.9%. CONCLUSION: The 5-day prolonged DPT has high NPV and seems appropriate in duration for children with suspected nonimmediate-BLA allergy.

Adding a second skin prick test reading and modifying the cut-off for beta-lactam-specific IgE enhances the sensitivity in the routine diagnostic workup for immediate beta-lactam hypersensitivity.

BACKGROUND: Beta-lactam (BL)-antibiotics are the most frequent reason for drug-induced hypersensitivity reactions. Because they are more efficient, less toxic, and less costly than other antibiotics, confirmation or exclusion of BL allergy is worthwhile. However, allergy tests for drug allergies are often false-negative. OBJECTIVES: To evaluate the components of a stepwise diagnostic algorithm for immediate BL hypersensitivity with regard to sensitivity (SENS). METHODS: Consecutive patients with suspected allergy to BL antibiotics were retrospectively analyzed with regard to increasing sensitivity (plausible history of immediate BL hypersensitivity serving as external criterion) of (i) skin prick test (SPT) by adding a second reading (n = 746), (ii) BL-specific IgE-determination in vitro at two cut-offs (n = 539), and (iii) adding in vivo testing of minor and major BL determinants (n = 288). RESULTS: In the history-based population indicative of immediate BL hypersensitivity (n = 457), SPT with a sole 20-minute reading identified 99 (SENS: 0.21) and SPT with 20- and 40-minute-reading identified 133 cases (SENS: 0.29). in vitro specific IgE-examination identified 31 positives at a cut-off ≥0.35 kUA/L (5.8% of tested) and 99 at cut-off ≥0.11 kUA/L (18.4% of tested). In 203 SPT-negative individuals, immediate BL hypersensitivity was identified by additional tests: in 79 by specific IgE (cut-off ≥0.11 kUA/L) (thereof 53 identified solely by this test) and in 150 by in vivo testing of BL determinants in combination with Penicillin and Ampicillin intradermally (thereof 124 solely by this test); in 26 individuals both additional tests were positive. The combination of the three outpatient-based test modalities-(i) optimized SPT, (ii) specific IgE at optimized cut-off, and (iii) in vivo testing of BL determinants/Penicillin/Ampicillin-identified altogether 336/457 individuals with immediate BL-hypersensitivity (SENS: 0.73), whereas the combination of the two (i) + (ii) identified 212/457 (SENS: 0.46); (i) + (iii) 283/457 (SENS: 0.61). CONCLUSIONS: To overcome the low sensitivity of allergological tests, optimized reading times of the SPT of BL, a lower cut-off for in vitro detection of BL-specific IgE, and intradermal testing of Penicillin, Ampicillin, and BL-determinants contribute to overall sensitivity under real life conditions to diagnose immediate BL-hypersensitivity.

The use of in vivo and in vitro tests in children with beta lactam allergy.

BACKGROUND: Drug allergies are reactions within the context of drug hypersensitivity reactions, which are caused by immunological mechanisms due to a previously sensitising drug. Beta-lactam antibiotics (BLA) are the leading agents causing drug hypersensitivity reactions in children. The aim of this study is to evaluate the diagnostic importance of in vivo and in vitro diagnostic tests in children with suspected immediate-type BLA hypersensitivity and to investigate the frequency of their use for the final diagnosis. METHODS: Patients admitted to the Outpatient Clinic of Division of Paediatric Allergy and Immunology with suspicion of immediate-type BLA hypersensitivity between December 2014 and December 2018 were investigated. Patients with a history of immediate reactions to BLA were examined by performing drug specific IgE, skin prick tests, intradermal tests and drug provocation tests (DPT). RESULTS: During the study period, 148 patients were admitted to our clinic with suspected immediate-type BLA hypersensitivity. Forty-eight patients completed all assessment steps and were enrolled in the study. It has been shown that 27 patients did not have drug allergy. BLA hypersensitivity was proven in 21 patients by using in vivo test algorithm. More than half of the patients were diagnosed via skin tests with culprit drug. CONCLUSION: Allergy work-up should be performed in patients with immediate reactions to BLA. A skin test can demonstrate BLA hypersensitivity in most patients. Thus, skin tests should be performed prior to the drug provocation test.

A EAACI drug allergy interest group survey on how European allergy specialists deal with ß-lactam allergy.

An accurate diagnosis of ß-lactam (BL) allergy can reduce patient morbidity and mortality. Our aim was to investigate the availability of BL reagents, their use and test procedures in different parts of Europe, as well as any differences in the diagnostic workups for evaluating subjects with BL hypersensitivity. A survey was emailed to all members of the EAACI Drug Allergy Interest Group (DAIG) between February and April 2016, and the questionnaire was meant to study the management of suspected BL hypersensitivity. The questionnaire was emailed to 82 DAIG centres and answered by 57. Amoxicillin alone or combined to clavulanic acid were the most commonly involved BL except in the Danish centre, where penicillin V was the most frequently suspected BL. All centres performed an allergy workup in subjects with histories of hypersensitivity to BL: 53 centres (93%) followed DAIG guidelines, two national guidelines and two local guidelines. However, there were deviations from DAIG recommendations concerning allergy tests, especially drug provocation tests. A significant heterogeneity exists in current practice not only among countries, but also among centres within the same country. This suggests the need to re-evaluate, update and standardize protocols on the management of patients with suspected BL allergy.

Antibiotic Allergy in Children: More than Just a Label.

Within the broad category of adverse drug reactions in children, there has been a recent focus specifically on the evaluation of children with antibiotic allergy, in particular, beta-lactam allergy. The potential consequences of being labeled beta-lactam allergy are increasingly recognized. Appropriate evaluation of children with suspected reactions to antibiotics is essential as it is increasingly being recognized that the label of "penicillin allergy" is associated with adverse health and economic outcomes. This review will focus on the 3 main classes of antibiotics reported to cause allergic reactions in children: beta lactams (penicillin derivatives and cephalosporins), macrolides, and sulfonamides. This article is a narrative review of the prevalence, diagnosis, and management of different types of antibiotic allergies in children. Our review reveals that antibiotic allergy is often overreported and not appropriately diagnosed in the pediatric age groups. There is a recent shift in the diagnostic paradigm from the use of skin tests and if negative challenges to the use of challenge only in the pediatric age group. Larger studies to establish the usefulness and safety of this new approach as well as updated guidelines are needed.

Skin tests are important in children with ß-lactam hypersensitivity, but may be reduced in number.

BACKGROUND: There is no perfect agreement on how to perform an allergy workup in suspected beta-lactam (BL)-allergic children, since skin test (ST)-induced pain is often a limitation. The aim of the study was to assess the possibility of reducing the number of ST in children when performing a complete allergy workup for BL hypersensitivity reactions. METHODS: A retrospective analysis of all patients referring to the Allergy Unit of the University Hospital of Montpellier (France) with positive responses in immediateand non-immediate-reading ST to a BL over a 16-year period was performed, to determine the positive predictive value (PPV) of ST. All pediatric patients with a suspected BL hypersensitivity were skin-tested with the suspected drug only, during the following 54 months. RESULTS: A total of 319 patients reporting 328 BL reactions were included in the retrospective study. The PPV of ST for the reported drug was of 99.4%. Based on the results, the number of patients to include in the prospective study was estimated to be 101. In the prospective study, 229 children were included. We diagnosed a BL hypersensitivity in 12 children (5.2%): Diagnosis was reached in 6 (50.0%) through ST (delayed reading for all) and in 6 through drug provocation test (DPT). CONCLUSION: ST with BL should therefore be performed as a screening test, before DPT, and testing only the suspected drug may be sufficient when dealing with children.

Definition of the Nature and Hapten Threshold of the ß-Lactam Antigen Required for T Cell Activation In Vitro and in Patients.

Covalent modification of protein by drugs may disrupt self-tolerance, leading to lymphocyte activation. Until now, determination of the threshold required for this process has not been possible. Therefore, we performed quantitative mass spectrometric analyses to define the epitopes formed in tolerant and hypersensitive patients taking the ß-lactam antibiotic piperacillin and the threshold required for T cell activation. A hydrolyzed piperacillin hapten was detected on four lysine residues of human serum albumin (HSA) isolated from tolerant patients. The level of modified Lys541 ranged from 2.6 to 4.8%. Analysis of plasma from hypersensitive patients revealed the same pattern and levels of modification 1-10 d after the commencement of therapy. Piperacillin-responsive skin-homing CD4+ clones expressing an array of Vß receptors were activated in a dose-, time-, and processing-dependent manner; analysis of incubation medium revealed that 2.6% of Lys541 in HSA was modified when T cells were activated. Piperacillin-HSA conjugates that had levels and epitopes identical to those detected in patients were shown to selectively stimulate additional CD4+ clones, which expressed a more restricted Vß repertoire. To conclude, the levels of piperacillin-HSA modification that activated T cells are equivalent to the ones formed in hypersensitive and tolerant patients, which indicates that threshold levels of drug Ag are formed in all patients. Thus, the propensity to develop hypersensitivity is dependent on other factors, such as the presence of T cells within an individual's repertoire that can be activated with the ß-lactam hapten and/or an imbalance in immune regulation.

Short and extended provocation tests have similar negative predictive value in non-immediate hypersensitivity to beta-lactams in children.

INTRODUCTION AND OBJECTIVES: Drug provocation tests (DPTs) are the gold-standard method to diagnose non-immediate hypersensitivity reactions (NIHSR) to beta-lactam antibiotics (BL) in children. Our aim was to compare the negative predictive value (NPV) of one-day (short) DPT versus 3-7 days (extended) DPT for the diagnosis of NIHSR to BL in paediatric age. A secondary aim was to compare confidence on drug re-exposure after short and extended negative DPTs. METHODS: The occurrence of HSR on drug re-exposure and drug refusal after negative diagnostic DPTs were evaluated in children/adolescents with a history of NIHSR to BL using a questionnaire performed six months to ten years after DPT. Patients were divided into two groups according to the protocol performed: short DPT vs. extended DPT. RESULTS: We enrolled 212 children and adolescents (86 females, 126 males, mean age at DPT 5.52 years, p25=3 years, p75=7.25 years): 69 tested with short DPT, and 143 with extended DPT. The NPV of both types of DPT together was 95.2%. The NPV of short DPT was 97.5% and the NPV of extended DPT was 93.8% (p=0.419). After negative DPT, beta-lactams were refused by carers in 14.75% of the children requiring subsequent treatment, 6.98% in the short DPT group and 18.99% in the extended DPT group (p=0.074). CONCLUSIONS: In our paediatric sample, prolonging drug administration did not increase the NPV of diagnostic DPT for NIHSR to BL or reduce drug refusal. Altogether, the data here reported suggest that, however intuitive, prolonging DPT is not beneficial in the parameters analysed.

Anaphylaxis to beta-lactam antibiotics at pediatric age: Six-year survey.

INTRODUCTION: Beta-lactams are the most frequently used antibiotics in pediatric age. Anaphylactic reactions may occur and need to be properly studied, but studies in children are scarce. OBJECTIVE: Characterization of case reports of anaphylaxis in children referred to an allergy department with suspected beta-lactams hypersensitivity. MATERIALS AND METHODS: Retrospective analysis of all children referred to our Drug Allergy Center with suspected beta-lactams hypersensitivity between January 2011 and December 2016. Description of the drug allergy work-up performed studied according to standardized diagnostic procedures of ENDA/EAACI, including specific-IgE assay, skin prick and intradermal tests and diagnostic/alternative drug challenge tests. RESULTS: 146 children with suspected beta-lactams hypersensitivity were studied, and in 21 (14.4%) the diagnosis was confirmed. In all of them, except for three children, an alternative beta-lactam was found. In seven children (33.3% of those with confirmed beta-lactams hypersensitivity) anaphylaxis was confirmed, and all of them described reactions with cutaneous and respiratory or gastrointestinal involvement. The culprit drug was amoxicillin in six and flucloxacillin in one. In this sample, we also performed oral challenge with cefuroxime, being negative in all cases. Almost all cases of confirmed anaphylaxis (six from seven cases) were IgE mediated, with positive skin tests despite negative serum specific-IgE. CONCLUSIONS: Allergic reactions to beta-lactams, although rare in children, require a detailed clinical history and a specialized drug allergy work-up to allow a correct diagnosis as well as to avoid the possibility of a potential life-threatening reaction and provide alternative drugs.

Evaluation and Management of Penicillin Allergy: A Review.

IMPORTANCE: ß-Lactam antibiotics are among the safest and most effective antibiotics. Many patients report allergies to these drugs that limit their use, resulting in the use of broad-spectrum antibiotics that increase the risk for antimicrobial resistance and adverse events. OBSERVATIONS: Approximately 10% of the US population has reported allergies to the ß-lactam agent penicillin, with higher rates reported by older and hospitalized patients. Although many patients report that they are allergic to penicillin, clinically significant IgE-mediated or T lymphocyte-mediated penicillin hypersensitivity is uncommon (<5%). Currently, the rate of IgE-mediated penicillin allergies is decreasing, potentially due to a decreased use of parenteral penicillins, and because severe anaphylactic reactions to oral amoxicillin are rare. IgE-mediated penicillin allergy wanes over time, with 80% of patients becoming tolerant after a decade. Cross-reactivity between penicillin and cephalosporin drugs occurs in about 2% of cases, less than the 8% reported previously. Some patients have a medical history that suggests they are at a low risk for developing an allergic reaction to penicillin. Low-risk histories include patients having isolated nonallergic symptoms, such as gastrointestinal symptoms, or patients solely with a family history of a penicillin allergy, symptoms of pruritus without rash, or remote (>10 years) unknown reactions without features suggestive of an IgE-mediated reaction. A moderate-risk history includes urticaria or other pruritic rashes and reactions with features of IgE-mediated reactions. A high-risk history includes patients who have had anaphylaxis, positive penicillin skin testing, recurrent penicillin reactions, or hypersensitivities to multiple ß-lactam antibiotics. The goals of antimicrobial stewardship are undermined when reported allergy to penicillin leads to the use of broad-spectrum antibiotics that increase the risk for antimicrobial resistance, including increased risk of methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococcus. Broad-spectrum antimicrobial agents also increase the risk of developing Clostridium difficile (also known as Clostridioides difficile) infection. Direct amoxicillin challenge is appropriate for patients with low-risk allergy histories. Moderate-risk patients can be evaluated with penicillin skin testing, which carries a negative predictive value that exceeds 95% and approaches 100% when combined with amoxicillin challenge. Clinicians performing penicillin allergy evaluation need to identify what methods are supported by their available resources. CONCLUSIONS AND RELEVANCE: Many patients report they are allergic to penicillin but few have clinically significant reactions. Evaluation of penicillin allergy before deciding not to use penicillin or other ß-lactam antibiotics is an important tool for antimicrobial stewardship.

Das Kreuz mit der Kreuzallergie: Betalaktamantibiotika-Allergie.

Hypersensitivity reactions to betalactam antibiotics are the most commonly mentioned drug allergies. Up to 10 percent of patients report to suffer from a penicillin allergy. However, classical side effects of antibiotics are often misdiagnosed as an allergy. Many of these patients with suspected betalactam allergy tolerate betalactam antibiotics well. Therefore, a thorough allergy workup is essential to confirm a suspected allergy or to enable again a treatment with betalactam antibiotics. Most important is a good documentation as skin- and in-vitro tests have a reduced sensitivity. Gold standard is the provocation test to help exclude a supposed allergy or to test alternative, potential cross reactive betalactam antibiotics. Cross-reactions between penicillins and cephalosporins, especially cephalosporins of the third and fourth generation are unusual. Cross reactions to carbapenem antibiotics are rare.

Drug allergy evaluation for betalactam hypersensitivity: Cross-reactivity with cephalosporines, carbapenems and negative predictive value.

BACKGROUND: There are no studies on cross-reactivity of betalactams among patients allergic to penicillin, or on the negative predictive value (NPV) of penicillin allergy evaluation from Arabian Gulf countries. OBJECTIVE: We aimed to assess the role and NPV of drug provocation test (DPT) for betalactam hypersensitivity reactions in patients referred for allergy evaluation in Kuwait. METHODS: Skin test (ST) was performed for all patients with a history of betalactam hypersensitivity, other than anaphylaxis. Patients with a negative ST were challenged with a DPT containing phenoxymethyl penicillin or the culprit drug. Patients with anaphylaxis or who tested positive to betalactams were then challenged with a DPT containing cefuroxime, meropenem or ceftriaxone. Patients who tested negative were contacted by phone to evaluate subsequent betalactam intake. RESULTS: A total of 214 patients were tested for betalactam hypersensitivity. We had 91(42.5%) positive cases. Among positives, there were 78 (85.7%) patients with an initial reaction to penicillin and 13 (14.3%) who reacted to cephalosporin. DPT with alternative betalactam was performed in fifty who tested positive for betalactam hypersensitivity and 45 (90%) tolerated alternative antibiotics. Phone calls to 113 (59.8%) patients with negative betalactam testing showed that among 40(35.4%) patients who were successfully contacted; 17 (15%) took betalactams and 23 (20%) did not. Among the 17 patients who took betalactams, our calculated NPV for penicillin testing range from 88.2 to 100%, as the 2 patients who reported a reaction refused confirmatory retesting. CONCLUSION: Carbapenems and cephalosporines can be safely given to penicillin allergic patients by means of skin testing and if negative, proceeding with a graded challenge. Our calculated NPV for penicillin testing is similar to other studies.

Point-of-Care ß-Lactam Allergy Skin Testing by Antimicrobial Stewardship Programs: A Pragmatic Multicenter Prospective Evaluation.

Background: ß-lactam allergy skin testing (BLAST) is recommended by antimicrobial stewardship program (ASP) guidelines, yet few studies have systematically evaluated its impact when delivered at point of care. Methods: We conducted a pragmatic multicenter prospective evaluation of the use of point-of-care BLAST by ASPs. In staggered 3-month intervals, ASP teams at 3 hospitals received training by allergists to offer BLAST for eligible patients with infectious diseases receiving nonpreferred therapy due to severity of their reported allergy. The primary outcome was the proportion of patients receiving the preferred ß-lactam therapy. Results: Of 827 patients with reported ß-lactam allergy over 15 months, ß-lactam therapy was preferred among 632 (76%). During baseline periods, 50% (124/246) received preferred ß-lactam therapy based on history, compared with 60% (232/386) during the intervention periods (P = .02), which improved further to 81% (313/386) upon provision of BLAST (P < .001) without any increase in incidence of adverse drug reactions (4% vs 3%; P = .4). After adjusting for patient variables and the correlation between hospitals, the intervention period was associated with a 4.5-fold greater odds of receiving preferred ß-lactam therapy (95% confidence interval, 2.4-8.2; P < .0001). Conclusions: The use of BLAST at the point of care across 3 hospital ASPs resulted in greater use of preferred ß-lactam therapy without increasing the risk of adverse drug reactions. Longer-term studies are needed to better assess the safety and clinical impact of this ASP intervention.

Detection of drug-responsive B lymphocytes and antidrug IgG in patients with ß-lactam hypersensitivity.

BACKGROUND: Delayed-type ß-lactam hypersensitivity develops in subset of patients. The cellular immunological processes that underlie the drug-specific response have been described; however, little is known about involvement of the humoral immune system. Thus, the aim of this study was to utilize piperacillin hypersensitivity as an exemplar to (i) develop cell culture methods for the detection of drug-specific B-cell responses, (ii) characterize drug-specific IgG subtypes and (iii) assess reactivity of IgG antibodies against proteins modified to different levels with piperacillin haptens. METHODS: IgG secretion and CD19+ CD27+ expression on B cells were measured using ELISPOT and flow cytometry, respectively. A piperacillin-BSA adduct was used as an antigen in ELISA antibody binding studies. Adducts generated using different ratios of drug to protein were used to determine the degree of conjugation required to detect IgG binding. RESULTS: B cells from hypersensitive patients, but not controls, were stimulated to secrete IgG and increase CD27 expression when cultured with soluble piperacillin. A piperacillin-BSA adduct with cyclized and hydrolysed forms of the hapten bound to eight lysine residues was used to detect hapten-specific IgG 1-4 subclasses in patient plasma. Hapten inhibition and the use of structurally unrelated hapten-BSA adducts confirmed antigen specificity. Antibody binding was detected with antigens generated at piperacillin/BSA ratios of 10:1 and above, which corresponded to a minimum epitope density of 1 for antibody binding. CONCLUSION: These data show that antigen-specific B lymphocytes and T lymphocytes are activated in piperacillin-hypersensitive patients. Further work is needed to define the role different IgG subtypes play in regulating the iatrogenic disease.

Amoxicillin haptenates intracellular proteins that can be transported in exosomes to target cells.

BACKGROUND: Allergic reactions to ß-lactams are among the most frequent causes of drug allergy and constitute an important clinical problem. Drug covalent binding to endogenous proteins (haptenation) is thought to be required for activation of the immune system. Nevertheless, neither the nature nor the role of the drug protein targets involved in this process is fully understood. Here, we aim to identify novel intracellular targets for haptenation by amoxicillin (AX) and their cellular fate. METHODS: We have treated B lymphocytes with either AX or a biotinylated analog (AX-B). The identification of protein targets for haptenation by AX has been approached by mass spectrometry and immunoaffinity techniques. In addition, intercellular communication mediated by the delivery of vesicles loaded with AX-B-protein adducts has been explored by microscopy techniques. RESULTS: We have observed a complex pattern of AX-haptenated proteins. Several novel targets for haptenation by AX in B lymphocytes have been identified. AX-haptenated proteins were detected in cell lysates and extracellularly, either as soluble proteins or in lymphocyte-derived extracellular vesicles. Interestingly, exosomes from AX-B-treated cells showed a positive biotin signal in electron microscopy. Moreover, they were internalized by endothelial cells, thus supporting their involvement in intercellular transfer of haptenated proteins. CONCLUSIONS: These results represent the first identification of AX-mediated haptenation of intracellular proteins. Moreover, they show that exosomes can constitute a novel vehicle for haptenated proteins, and raise the hypothesis that they could provide antigens for activation of the immune system during the allergic response.