Background: Vancomycin, a glycopeptide antibiotic routinely used to treat severe Gram-positive bacterial infections, is associated with the development of drug reaction with eosinophilia and systemic symptoms (DRESS) in individuals expressing HLA-A*32:01. Previous studies have identified the potential role of T-cells using HLA-A*32:01 positive healthy donor models. However, DRESS pathogenesis remains poorly defined and a deeper mechanistic understanding is now required to aid the diagnosis and prediction of vancomycin-induced DRESS. The present study aims to elucidate CD4+ and CD8+ T-cell involvement within the pathogenesis of vancomycin-induced DRESS following the isolation and functional study of cloned T-cells from hypersensitive patients. Methods: CD4+ and CD8+ vancomycin-responsive T-cell clones (TCCs) were generated by serial dilution from PBMC samples collected from suspected vancomycin-DRESS patients. Functionality of drug-responsive TCCs was assessed using T-cell proliferation ([ 3H]-thymidine). Cytokine analysis was performed using intracellular cytokine staining (ICS), ELISpot assay and LEGENDplex immunoassays. Results: Vancomycin-responsive TCCs expressing CD4+ and CD8+ phenotypes were successfully generated from suspected vancomycin-DRESS patients (n=3). CD45RO + memory T-cells were the primary activated population, with both CD4+ and CD8+ T-cells associated with the release of IFN-γ, IL-5, IL-13, granzyme B and perforin. Vancomycin-responsive CD4+ and CD8+ T-cells are activated by direct, pharmacological interactions, with antigen presentation possible through both HLA class I and HLA class II molecules. Conclusion: This study provides in vitro evidence for the dual role of antigen-specific CD4+ and CD8+ T-cells within the pathogenesis of vancomycin-induced DRESS. This has been demonstrated following the generation of cloned T-cells with strong vancomycin specificity from patients presenting with vancomycin-DRESS and positive for expression of HLA-A*32:01.

Background Drug-induced severe cutaneous adverse reactions (SCARs) are presumed T-cell-mediated hypersensitivities associated with significant morbidity and mortality. Traditional in-vivo testing methods, such as patch or intradermal testing, are limited by a lack of standardisation and poor sensitivity. Modern approaches to testing include measurement of IFN-γ release from patient peripheral blood mononuclear cells (PBMC) stimulated with the suspected causative drug. Objective We sought to improve ex-vivo diagnostics for drug-induced SCAR by comparing enzyme-linked immunospot (ELISpot) sensitivities and flow cytometry-based intracellular cytokine staining (ICS) and cellular composition of separate samples (PBMC or blister fluid cells (BFC)) from the same donor. Methods IFN-γ release ELISpot and flow cytometry analyses were performed on donor-matched PBMC and BFC samples from four SCAR patients with distinct drug-allergies. Results Immune responses to suspected drugs were detected in both PBMC and BFC samples of two donors (Case 1 in response to ceftriaxone and Case 4 to oxypurinol), with BFC eliciting stronger responses. For two other donors, only BFC samples showed a response to meloxicam(Case 2) or sulfamethoxazole and its 4-Nitro metabolite (Case 3). Consistently, flow cytometry revealed a greater proportion of IFN-γ-secreting cells in the BFC compared to PBMC. BFC cells from Case 3 were also enriched for memory/activation/tissue-recruitment markers over PBMC. Conclusion Analysis of BFC samples for drug-allergy diagnostics offers a higher sensitivity for detecting positive responses compared to PBMC. This is consistent with recruitment (and enrichment) of cytokine-secreting cells with a memory/activated phenotype into blisters.

An 80-year-old man had a secondary prevention defibrillator in place for treatment of sustained ventricular tachycardia. After a generator replacement several years later, he developed a series of apparent pulse generator infections requiring extraction. Each purulent appearing pocket eruption was culture negative. Eventually, he was diagnosed with a delayed hypersensitivity reaction to triclosan, an antibacterial that is commonly impregnated in surgical sutures. The evaluation for this is difficult and can be misleading. This entity should be considered in the differential diagnosis of patients with culture negative CIED infections.

Addressing Beta-lactam Allergy: A Time for actionElizabeth J. Phillips, MD, FIDSA, FAAAAI, Pascal Demoly, MD, PhD, Maria J Torres, MD, PhD1 Department of Medicine, Center for Drug Safety and Immunology, Vanderbilt University Medical Center, Nashville Tennessee USA, 2Institute for Immunology & Infectious Diseases, Murdoch University, Murdoch Australia, 3Division of Allergy, Department of Pulmonology, University Hospital of Montepellier, and IDESP, Univ. Montpellier – Inserm, Montpellier France,4Allergy Unit, Hospital Regional Universitario de Malaga-IBIMA-BIONAND-ARADyAL, and Departmento de Medicina, Universidad de Malaga, Malaga, SpainCorrespondence:Elizabeth J. Phillips, MD, FIDSA, FAAAAICenter for Drug Safety and ImmunologyVanderbilt University Medical Center1161 – 21st Avenue SouthNashville, TN 37232(615) 322-9174 (tel)Elizabeth.j.phillips@vumc.orgIt is now 93 years since the discovery of penicillins, and over 75 years since the first use of penicillin. We have entered yet another wave of challenges plagued with antibiotic resistance accelerating at a rate that well exceeds that of new antibiotic development. In the face of these uphill battles, 8-15% of a global population who has had access to care is labeled as penicillin allergic.1 In the United States (US) there are at maximum 6000 specialists who practice allergy out of a total of 700,000 practicing physicians, and not all allergists are proficient in and practice drug allergy. Conservatively out of 30,000,000 who are labeled as penicillin allergic at any one time in the US, this would mean that each allergist would need to delabel a minimum of 6000 patients. In Europe and the United Kingdom, the figures are proportionately identical, with some differences between countries. Even if all patients had equal access to care, this type of scalability remains impossible. This overwhelming burden that threatens to negatively impact healthcare through delays in treatment, higher healthcare utilization and cost, less effective treatment and increased antibiotic resistance and Clostridioides difficile infection, demands a risk-based approach that simplifies the penicillin allergy delabeling process and establishes bridges with non-allergists.1, 2What have we learned that now makes the population level goal of penicillin delabeling achievable? First off, prevention is better than cure. We should critically examine pediatric populations for antibiotic use to address over-prescription of antibiotics including penicillins for viral infections. We should avoid labeling children with benign delayed exanthems that occur in the setting of a likely viral infection as penicillin allergic. When continued treatment is necessary we should in fact encourage “treating through” such reactions. When a label of penicillin allergy seems inevitable in a child we should address this label early and pay particular attention to antibiotic stewardship. New data on serum sickness-like reaction suggests that many of these are likely virally mediated and do not reproduce on ingestion challenge.3 Community based education programs can help disseminate timely information on penicillin allergy to dispel myths and alleviate fears. A label of penicillin allergy should be both viewed and approached as a threat to both individual and public health. On a public health level addressing penicillin allergy should be seen as a broad stewardship tool that provides a level of herd protectiveness against antibiotic resistance. On an individual level a label of penicillin allergy should be approached with the same routineness as any other preventative health check, and primary care physicians and providers should be trained to understand and manage low-risk penicillin allergy labels.4 Patients should regularly discuss their drug allergy passport with their healthcare providers such as pharmacists and physicians. Allergy passports should enable interoperability, high traceability and time-stamped information solving the problem of frequent unavailability and inaccuracy of drug allergy information.5 Risk stratification should occur and if in a low-risk category a patient should be given the option of direct oral challenge and delabeling. Risk stratification to identify by clinical history the low-risk penicillin allergic patients who would be appropriate for simple procedures is key. Several mechanisms now exist to risk stratify those labeled as penicillin allergic in routine clinical practice. These clinical prediction rules provide an evidence base to identify the majority of low-risk penicillin allergy labeled patients who are at low risk for rechallenge reactions.6, 7 In current practice it is likely that less than 1% of such low-risk patients will be at risk for a reaction on ingestion challenge.1, 8To make widespread penicillin allergy delabeling an achievable and scalable goal we must be convinced of the safety of direct ingestion challenges. A randomized study allocated children 5 years or older with low-risk cutaneous reaction to penicillin skin testing followed by amoxicillin challenge versus 2 step direct oral challenge with amoxicillin with tolerance of amoxicillin of 96% of those with direct challenge and only minor reactions in the remainder.9These results have recently been confirmed in an European population of children.10 Aside from the inconvenience and potential need for specialty assessment, for very low-risk patients, the use of skin testing would be expected to perform poorly considering their low pre-test probability of a reaction. Several other studies have demonstrated that a single or two-step direct ingestion challenge with penicillins such as amoxicillin is a safe and practical strategy to remove a label of penicillin allergy.11 Although there is evidence to support the use of risk stratification tools to delabel penicillin allergy under allergist guidance, we require an educational program on drug allergy for primary care physicians as well validation of these risk stratification tools, to show that low-risk penicillin delabeling can be achieved in this setting.Even in the face of risk stratification and safety of direct ingestion challenge, populations are not equal in terms of their medical risk or antibiotic needs. Intuitively populations that serve to benefit from penicillins and other beta lactams have been shown to have inferior outcomes when labeled as penicillin allergic that would benefit from a delabeling intervention. This includes the association of penicillin allergy label and use of an alternative antibiotic with post-operative surgical site infections.12 Other settings where research has shown feasibility in delabeling include children in the emergency department, critically ill populations with high antibiotic needs, and pregnant women where the high rates of surgical delivery and group B Streptococcal colonization in pregnancy create a high demand for penicillin and cephalosporins as safe firstline drugs.1, 13, 14 Increasingly, assessment of unverified penicillin allergy has been recognized as an antibiotic stewardship intervention in immunocompromised states such as transplant and cancer where populations have much to gain by being delabeled.15There is a “time for action” for removal of penicillin allergy labels on a population level but how do we achieve widespread implementation (Figure 1)? Policy changes should be driven by collaboration with Infectious diseases specialists and allergists who should join forces to pair antibiotic allergy management with antibiotic stewardship. In the community we need to educate parents and pediatricians to make them aware of the hazards of both unnecessary antibiotics and penicillin allergy labels for mild rashes that are often related to a viral infection and unlikely to recur. Primary healthcare providers should be given greater incentives to delabel penicillin allergic patients at the point-of-care and armed with decision support tools to facilitate risk stratification. For those whose history is not consistent with allergy this could include direct delabeling without testing. In the future, evidence may support that routine direct ingestion challenge with a penicillin and delabeling is safe in the primary care setting. Finally, by off-loading low-risk reactions to primary care providers we can then prioritize care of the patients with a higher-risk allergy and/or medical history by engagement with specialists who can provide more in-depth assessments and give them the best antibiotic options.Figure 1: Addressing Beta-lactam Allergy: An Implementation Roadmap: There are currently many missed opportunities for community members and healthcare providers to take action forward on the “penicillin allergy delabeling” movement. This includes not only active measures to delabel patients by history and direct oral challenge and to identify high risk patients for prioritized penicillin allergy delabeling but also preventive measures to avoid unnecessary use and exposure to antibiotics and avoidance of unnecessary labeling in those with mild rashes of likely viral origin.