Selective Detection of Active Extracellular Granzyme A by Using a Novel Fluorescent Immunoprobe with Application to Inflammatory Diseases.

Granzymes (Gzms), a family of serine proteases, expressed by immune and nonimmune cells, present perforin-dependent and independent intracellular and extracellular functions. When released in the extracellular space, GzmA, with trypsin-like activity, is involved in the pathophysiology of different inflammatory diseases. However, there are no validated specific systems to detect active forms of extracellular GzmA, making it difficult to assess its biological relevance and potential use as a biomarker. Here, we have developed fluorescence-energy resonance-transfer (FRET)-based peptide probes (FAM-peptide-DABCYL) to specifically detect GzmA activity in tissue samples and biological fluids in both mouse and human samples during inflammatory diseases. An initial probe was developed and incubated with GzmA and different proteases like GzmB and others with similar cleavage specificity as GzmA like GzmK, thrombin, trypsin, kallikrein, or plasmin. After measuring fluorescence, the probe showed very good specificity and sensitivity for human and mouse GzmA when compared to GzmB, its closest homologue GzmK, and with thrombin. The specificity of this probe was further refined by incubating the samples in a coated plate with a GzmA-specific antibody before adding the probe. The results show a high specific detection of soluble GzmA even when compared with other soluble proteases with very similar cleavage specificity like thrombin, GzmK, trypsin, kallikrein, or plasmin, which shows nearly no fluorescence signal. The high specific detection of GzmA was validated, showing that using pure proteins and serum and tissue samples from GzmA-deficient mice presented a significant reduction in the signal compared with WT mice. The utility of this system in humans was confirmed, showing that GzmA activity was significantly higher in serum samples from septic patients in comparison with healthy donors. Our results present a new immunoprobe with utility to detect extracellular GzmA activity in different biological fluids, confirming the presence of active forms of the soluble protease in vivo during inflammatory and infectious diseases.

CAR Immunotherapy for the treatment of infectious diseases: a systematic review.

Immunotherapy treatments aim to modulate the host's immune response to either mitigate it in inflammatory/autoimmune disease or enhance it against infection or cancer. Among different immunotherapies reaching clinical application during the last years, chimeric antigen receptor (CAR) immunotherapy has emerged as an effective treatment for cancer where different CAR T cells have already been approved. Yet their use against infectious diseases is an area still relatively poorly explored, albeit with tremendous potential for research and clinical application. Infectious diseases represent a global health challenge, with the escalating threat of antimicrobial resistance underscoring the need for alternative therapeutic approaches. This review aims to systematically evaluate the current applications of CAR immunotherapy in infectious diseases and discuss its potential for future applications. Notably, CAR cell therapies, initially developed for cancer treatment, are gaining recognition as potential remedies for infectious diseases. The review sheds light on significant progress in CAR T cell therapy directed at viral and opportunistic fungal infections.

Management of patients with suspected or confirmed antibiotic allergy. Executive summary of guidance from the Spanish Society of Infectious Diseases and Clinical Microbiology (SEIMC), the Spanish Society of Allergy and Clinical Immunology (SEAIC), the Spanish Society of Hospital Pharmacy (SEFH) and the Spanish Society of Intensive Medicine and Coronary Care Units (SEMICYUC) / Resumen ejecutivo de la Guía de práctica clínica de la Sociedad Española de Enfermedades Infecciosas y Microbiología Clínica (SEIMC), la Sociedad Española de Alergología e Inmunología Clínica (SEAIC), la Sociedad Española de Farmacia Hospitalaria (SEFH) y la Sociedad Española de Medicina Intensiva Crítica y Unidades Coronarias (SEMICYUC) sobre el manejo de personas con alergia a antibióticos sospechada o confirmada

Suspected or confirmed antibiotic allergy is a frequently encountered clinical circumstance that influences antimicrobial prescribing and often leads to the avoidable use of less efficacious and/or more toxic or costly drugs than first-line antimicrobials. Optimizing antimicrobial therapy in patients with antibiotic allergy labels has become one of the priorities of antimicrobial stewardship programs (ASP) in several countries. This guidance document aims to make recommendations for the systematic approach to patients with suspected or confirmed antibiotic allergy based on current evidence. A panel of eleven members of involved Scientific Societies with expertise in the management of patients with suspected or confirmed antibiotic allergy formulated questions about the management of patients with suspected or confirmed antibiotic allergy. A systematic literature review was performed by a medical librarian. The questions were distributed among panel members who selected the most relevant references, summarized the evidence and formulated graded recommendations when possible. The answers to all questions were finally reviewed by all panel members. A systematic approach to patients with suspected or confirmed antibiotic allergy is recommended to improve antibiotic selection and, consequently clinical outcomes. A clinically oriented, 3-category risk-stratification strategy was recommended for patients with suspected antibiotic allergy. Complementary assessments should consider both clinical risk category and preferred antibiotic agent. Empirical therapy recommendations for the most relevant clinical syndromes in patients with suspected or confirmed β-lactam allergy were formulated. Recommendations on the implementation and monitoring of the impact of the guidelines were formulated. ASP and allergists should design and implement activities that facilitate the most adequate antibiotic use in these patients.(AU)

En la práctica clínica, un antecedente de alergia a los antibióticos, confirmada o sospechada, es frecuente y condiciona la selección de antibióticos, lo que requiere, con frecuencia, el uso de fármacos menos eficaces, más tóxicos o más caros que los antibióticos de primera línea. La optimización del uso de antibióticos en pacientes con este antecedente es una de las prioridades de los programas de optimización de uso de antibióticos (PROA) en varios países. Estas guías pretenden formular recomendaciones para evaluar de una manera sistemática a estos pacientes mediante una aproximación basada en la evidencia. Un panel multidisciplinar constituido por alergólogos, infectólogos, farmacéuticos hospitalarios e intensivistas formularon una serie de preguntas sobre el manejo de estos pacientes. Una documentalista realizó la revisión bibliográfica. Las preguntas se distribuyeron entre los miembros del grupo de trabajo, quienes seleccionaron las referencias más relevantes y formularon las correspondientes recomendaciones, que fueron revisadas y aprobadas por todos los miembros del grupo. Es necesaria una aproximación sistemática a los pacientes con antecedente de alergia a antibióticos para optimizar la selección del tratamiento antibiótico y mejorar los resultados clínicos de estos pacientes cuando precisan antibioterapia. El presente documento recomienda una estrategia de estratificación clínica del riesgo en 3 categorías. La recomendación de realizar evaluaciones complementarias se basa en el riesgo clínico y el antibiótico de primera línea necesario. Además, se formulan recomendaciones de tratamiento antibiótico empírico para los principales síndromes infecciosos en pacientes con alergia confirmada o sospechada. Finalmente se formulan recomendaciones sobre la implementación y monitorización del impacto de las recomendaciones de la guía. Los programas PROA y los alergólogos deben trabajar...(AU)

Antimicrobial stewardship in hospitals: Expert recommendation guidance document for activities in specific populations, syndromes and other aspects (PROA-2) from SEIMC, SEFH, SEMPSPGS, SEMICYUC and SEIP.

In 2012, The Spanish Societies of Infectious Diseases and Clinical Microbiology (SEIMC), Hospital Pharmacy (SEFH), and Preventive Medicine, Public Health and Healthcare Management (SEMPSGS) lead a consensus document including recommendations for the implementation of antimicrobial stewardship (AMS) programs (AMSP; PROA in Spanish) in acute care hospitals in Spain. While these recommendations were critical for the development of these programs in many centres, there is a need for guidance in the development of AMS activities for specific patient populations, syndromes or other specific aspects which were not included in the previous document or have developed significantly since then. The objective of this expert recommendation guidance document is to review the available information about these activities in these patient populations or circumstances, and to provide guidance recommendations about them. With this objective the SEIMC, SEFH, SEMPSPGS, the Spanish Society of Intensive Care Medicine (SEMICYUC) and the Spanish Pediatric Infectious Disease Society (SEIP) selected a panel of experts who chose the different aspects to include in the document. Because of the lack of high-level evidence in the implementation of the activities, the panel opted to perform a narrative review of the literature for the different topics for which recommendations were agreed by consensus. The document was open to public consultation for the members of these societies for their comments and suggestions, which were reviewed and considered by the panel.

Management of patients with suspected or confirmed antibiotic allergy. Executive summary of guidance from the Spanish Society of Infectious Diseases and Clinical Microbiology (SEIMC), the Spanish Society of Allergy and Clinical Immunology (SEAIC), the Spanish Society of Hospital Pharmacy (SEFH) and the Spanish Society of Intensive Medicine and Coronary Care Units (SEMICYUC).

Suspected or confirmed antibiotic allergy is a frequently encountered clinical circumstance that influences antimicrobial prescribing and often leads to the avoidable use of less efficacious and/or more toxic or costly drugs than first-line antimicrobials. Optimizing antimicrobial therapy in patients with antibiotic allergy labels has become one of the priorities of antimicrobial stewardship programs (ASP) in several countries. This guidance document aims to make recommendations for the systematic approach to patients with suspected or confirmed antibiotic allergy based on current evidence. A panel of eleven members of involved Scientific Societies with expertise in the management of patients with suspected or confirmed antibiotic allergy formulated questions about the management of patients with suspected or confirmed antibiotic allergy. A systematic literature review was performed by a medical librarian. The questions were distributed among panel members who selected the most relevant references, summarized the evidence and formulated graded recommendations when possible. The answers to all questions were finally reviewed by all panel members. A systematic approach to patients with suspected or confirmed antibiotic allergy is recommended to improve antibiotic selection and, consequently clinical outcomes. A clinically oriented, 3-category risk-stratification strategy was recommended for patients with suspected antibiotic allergy. Complementary assessments should consider both clinical risk category and preferred antibiotic agent. Empirical therapy recommendations for the most relevant clinical syndromes in patients with suspected or confirmed ß-lactam allergy were formulated. Recommendations on the implementation and monitoring of the impact of the guidelines were formulated. ASP and allergists should design and implement activities that facilitate the most adequate antibiotic use in these patients.

Executive summary of the consensus document of the Spanish Society of Infectious Diseases and Clinical Microbiology (SEIMC) on the diagnosis and antimicrobial treatment of infections due to carbapenem-resistant Gram-negative bacteria.

Infections caused by multidrug resistant Gram-negative bacteria are becoming a worldwide problem due to their increasing incidence and associated high mortality. Carbapenem-resistant bacteria such as Klebsiella pneumoniae, Pseudomonas aeruginosa and Acinetobacter baumannii are the most important in clinical practice. The objective of these guidelines is to update the recommendations for the diagnosis and treatment of infections caused by these multidrug resistant bacteria. Although 'old' antibiotics such as aminoglycosides, colistin, or tigecycline are frequently used for therapy of these bacteria, the 'new' beta-lactams such as ceftazidime-avibactam, ceftolozane-tazobactam, meropenem-vaborbactam, imipenem-cilastatin-relebactam or cefiderocol are progressively becoming the first-line therapy for most of these microorganisms. The Spanish Society of Infectious Diseases and Clinical Microbiology (Sociedad Española de Enfermedades Infecciosas y Microbiología Clínica) designated a panel of experts in the field to provide evidence-based recommendations in response to common clinical questions. This document is primarily focused on microbiological diagnosis, clinical management, and targeted antimicrobial therapy of these infections, with special attention to defining the role of the new antimicrobials in the treatment of these bacteria.

Study protocol for a randomized clinical trial to assess 7 versus 14-days of treatment for Pseudomonas aeruginosa bloodstream infections (SHORTEN-2 trial).

BACKGROUND: Research priorities in Antimicrobial Stewardship (AMS) have rapidly evolved in the last decade. The need for a more efficient use of antimicrobials have fueled plenty of studies to define the optimal duration for antibiotic treatments, and yet, there still are large areas of uncertainty in common clinical scenarios. Pseudomonas aeruginosa has been pointed as a priority for clinical research, but it has been unattended by most randomized trials tackling the effectiveness of short treatments. The study protocol of the SHORTEN-2 trial is presented as a practical example of new ways to approach common obstacles for clinical research in AMS. OBJECTIVE: To determine whether a 7-day course of antibiotics is superior to 14-day schemes for treating bloodstream infections by P. aeruginosa (BSI-PA). METHODS: A superiority, open-label, randomized controlled trial will be performed across 30 Spanish hospitals. Adult patients with uncomplicated BSI-PA will be randomized to receive a 7 versus 14-day course of any active antibiotic. The primary endpoint will be the probability for the 7-day group of achieving better outcomes than the control group, assessing altogether clinical effectiveness, severe adverse events, and antibiotic exposure through a DOOR/RADAR analysis. Main secondary endpoints include treatment failure, BSI-PA relapses, and mortality. A superiority design was set for the primary endpoint and non-inferiority for treatment failure, resulting in a sample size of 304 patients. CONCLUSIONS: SHORTEN-2 trial aligns with some of the priorities for clinical research in AMS. The implementation of several methodological innovations allowed overcoming common obstacles, like feasible sample sizes or measuring the clinical impact and unintended effects. TRIAL REGISTRATION: EudraCt: 2021-003847-10; ClinicalTrials.gov: NCT05210439.

European society of clinical microbiology and infectious diseases guidelines for coronavirus disease 2019: an update on treatment of patients with mild/moderate disease.

SCOPE: Despite the large availability of vaccines, coronavirus disease 2019 (COVID-19), induced by severe acute respiratory syndrome coronavirus 2, continues to be a major threat for health-care providers and fragile people. A number of options are now available for outpatients with mild-to-moderate COVID-19 at the risk of disease progression for the prevention of deaths or hospitalization. METHODS: A European Society of Clinical Microbiology and Infectious Diseases COVID-19 guidelines task force was established by the European Society of Clinical Microbiology and Infectious Diseases Executive Committee. A small group was established, half appointed by the chair and the remaining selected based on an open call. Each panel met virtually once a week. For all decisions, a simple majority vote was used. A long list of clinical questions using the population, intervention, comparison, outcome format was developed at the beginning of the process. For each population, intervention, comparison, outcome, two panel members performed a literature search, with a third panelist involved in case of inconsistent results. Voting was based on the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach. RECOMMENDATIONS: In this update, we focus on anti-viral agents, monoclonal antibodies (mAbs) and other treatment options proposed for patients with mild or moderate COVID-19 who are at the risk of hospitalization or death. Although the use of anti-virals is recommended, especially nirmatrelvir/ritonavir and remdesivir or, alternatively, molnupirarvir, the administration of mAbs against the spike protein strictly depends on circulating variants or the ability to test timely for variants and sub-variants. At the time of writing (April-June 2022), the only active mAb was tixagevimab/cilgavimab given the predominance of the Omicron BA.2, BA.3, BA.4 and BA.5 sub-lineages in Europe. However, considering that the epidemiological scenario is extremely dynamic, constant monitoring of variants of concern is mandatory.

Serological evidence of SARS-CoV-2 and co-infections in stray cats in Spain.

A new coronavirus known as SARS-CoV-2 emerged in Wuhan in 2019 and spread rapidly to the rest of the world causing the pandemic disease named coronavirus disease of 2019 (COVID-19). Little information is known about the impact this virus can cause upon domestic and stray animals. The potential impact of SARS-CoV-2 has become of great interest in cats due to transmission among domestic cats and the severe phenotypes described recently in a domestic cat. In this context, there is a public health warning that needs to be investigated in relation with the epidemiological role of this virus in stray cats. Consequently, in order to know the impact of the possible transmission chain, blood samples were obtained from 114 stray cats in the city of Zaragoza (Spain) and tested for SARS-CoV-2 and other selected pathogens susceptible to immunosuppression including Toxoplasma gondii, Leishmania infantum, feline leukaemia virus (FeLV) and feline immunodeficiency virus (FIV) from January to October 2020. Four cats (3.51%), based on enzyme-linked immunosorbent assay (ELISA) using the receptor binding domain (RBD) of Spike antigen, were seroreactive to SARS-CoV-2. T. gondii, L. infantum, FeLV and FIV seroprevalence was 12.28%, 16.67%, 4.39% and 19.30%, respectively. Among seropositive cats to SARS-CoV-2, three cats were also seropositive to other pathogens including antibodies detected against T. gondii and FIV (n = 1); T. gondii (n = 1); and FIV and L. infantum (n = 1). The subjects giving positive for SARS-CoV-2 were captured in urban areas of the city in different months: January 2020 (2/4), February 2020 (1/4) and July 2020 (1/4). This study revealed, for the first time, the exposure of stray cats to SARS-CoV-2 in Spain and the existence of concomitant infections with other pathogens including T. gondii, L. infantum and FIV, suggesting that immunosuppressed animals might be especially susceptible to SARS-CoV-2 infection.

ESCMID COVID-19 living guidelines: drug treatment and clinical management.

SCOPE: In January 2021, the ESCMID Executive Committee decided to launch a new initiative to develop ESCMID guidelines on several COVID-19-related issues, including treatment of COVID-19. METHODS: An ESCMID COVID-19 guidelines task force was established by the ESCMID Executive Committee. A small group was established, half appointed by the chair, and the remaining selected with an open call. Each panel met virtually once a week. For all decisions, a simple majority vote was used. A long list of clinical questions using the PICO (population, intervention, comparison, outcome) format was developed at the beginning of the process. For each PICO, two panel members performed a literature search with a third panellist involved in case of inconsistent results. Voting was based on the GRADE approach. QUESTIONS ADDRESSED BY THE GUIDELINE AND RECOMMENDATIONS: A synthesis of the available evidence and recommendations is provided for each of the 15 PICOs, which cover use of hydroxychloroquine, bamlanivimab alone or in combination with etesevimab, casirivimab combined with imdevimab, ivermectin, azithromycin and empirical antibiotics, colchicine, corticosteroids, convalescent plasma, favipiravir, remdesivir, tocilizumab and interferon ß-1a, as well as the utility of antifungal prophylaxis and enoxaparin. In general, the panel recommended against the use of hydroxychloroquine, ivermectin, azithromycin, colchicine and interferon ß-1a. Conditional recommendations were given for the use of monoclonal antibodies in high-risk outpatients with mild-moderate COVID-19, and remdesivir. There was insufficient evidence to make a recommendation for use of favipiravir and antifungal prophylaxis, and it was recommended that antibiotics should not be routinely prescribed in patients with COVID-19 unless bacterial coinfection or secondary infection is suspected or confirmed. Tocilizumab and corticosteroids were recommended for treatment of severe COVID-19 but not in outpatients with non-severe COVID-19. SCOPE: The aim of the present guidance is to provide evidence-based recommendations for management of adults with coronavirus disease 2019 (COVID-19). More specifically, the goal is to aid clinicians managing patients with COVID-19 at various levels of severity including outpatients, hospitalized patients, and those admitted to intensive care unit. Considering the composition of the panel, mostly clinical microbiologists or infectious disease specialists with no pulmonology or intensive care background, we focus only on pharmacological treatment and do not give recommendations on oxygen supplement/support. Similarly, as no paediatricians were included in the panel; the recommendations are only for adult patients with COVID-19. Considering the current literature, no guidance was given for special populations such as the immunocompromised.

Absence of SARS-CoV-2 Antibodies in Natural Environment Exposure in Sheep in Close Contact with Humans.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the zoonotic causative agent of coronavirus disease 2019 (COVID-19) that has caused a pandemic situation with millions of infected humans worldwide. Among domestic animals, there have been limited studies regarding the transmissibility and exposure to the infection in natural conditions. Some animals are exposed and/or susceptible to SARS-CoV-2 infection, such as cats, ferrets and dogs. By contrast, there is no information about the susceptibility of ruminants to SARS-CoV-2. This study tested the antibody response in 90 ovine pre-pandemic serum samples and 336 sheep serum samples from the pandemic period (June 2020 to March 2021). In both cases, the animals were in close contact with a veterinary student community composed of more than 700 members. None of the serum samples analyzed was seroreactive based on an enzyme-linked immunosorbent assay (ELISA) using the receptor-binding domain (RBD) of the spike antigen. In this sense, no statistical difference was observed compared to the pre-pandemic sheep. Our results suggest that it seems unlikely that sheep could play a relevant role in the epidemiology of SARS-CoV-2 infection. This is the first study to report the absence of evidence of sheep exposure to SARS-CoV-2 in natural conditions.

Determination of the Concentration of IgG against the Spike Receptor-Binding Domain That Predicts the Viral Neutralizing Activity of Convalescent Plasma and Serum against SARS-CoV-2.

Several hundred millions of people have been diagnosed of coronavirus disease 2019 (COVID-19), causing millions of deaths and a high socioeconomic burden. SARS-CoV-2, the causative agent of COVID-19, induces both specific T- and B-cell responses, being antibodies against the virus detected a few days after infection. Passive immunization with hyperimmune plasma from convalescent patients has been proposed as a potentially useful treatment for COVID-19. Using an in-house quantitative ELISA test, we found that plasma from 177 convalescent donors contained IgG antibodies specific to the spike receptor-binding domain (RBD) of SARS-CoV-2, although at very different concentrations which correlated with previous disease severity and gender. Anti-RBD IgG plasma concentrations significantly correlated with the plasma viral neutralizing activity (VN) against SARS-CoV-2 in vitro. Similar results were found using an independent cohort of serum from 168 convalescent health workers. These results validate an in-house RBD IgG ELISA test in a large cohort of COVID-19 convalescent patients and indicate that plasma from all convalescent donors does not contain a high enough amount of anti-SARS-CoV-2-RBD neutralizing IgG to prevent SARS-CoV-2 infection in vitro. The use of quantitative anti-RBD IgG detection systems might help to predict the efficacy of the passive immunization using plasma from patients recovered from SARS-CoV-2.

Proof-of-concept trial of the combination of lactitol with Bifidobacterium bifidum and Lactobacillus acidophilus for the eradication of intestinal OXA-48-producing Enterobacteriaceae.

BACKGROUND: The major reservoir of carbapenemase-producing Enterobacteriaceae (CPE) is the gastrointestinal tract of colonized patients. Colonization is silent and may last for months, but the risk of infection by CPE in colonized patients is significant. METHODS: Eight long-term intestinal carriers of OXA-48-producing Enterobacteriaceae (OXA-PE) were treated during 3 weeks with daily oral lactitol (Emportal®), Bifidobacterium bifidum and Lactobacillus acidophilus (Infloran®). Weekly stool samples were collected during the treatment period and 6 weeks later. The presence of OXA-PE was investigated by microbiological cultures and qPCR. RESULTS: At the end of treatment (EoT, secondary endpoint 1), four of the subjects had negative OXA-PE cultures. Three weeks later (secondary endpoint 2), six subjects were negative. Six weeks after the EoT (primary endpoint), three subjects had negative OXA-PE cultures. The relative intestinal load of OXA-PE decreased in all the patients during treatment. CONCLUSIONS: The combination of prebiotics and probiotics was well tolerated. A rapid reduction on the OXA-PE intestinal loads was observed. At the EoT, decolonization was achieved in three patients.Clinical Trials Registration: NCT02307383. EudraCT Number: 2014-000449-65.

Neumonía adquirida en la comunidad en un hospital terciario español: ¿cómo se comporta en pacientes provenientes de residencia? / Community acquired pneumonia in a Spanish tertiary hospital: how does it work in patients from residence?

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Performance Assessment of Software to Detect and Assist Prescribers with Antimicrobial Drug Interactions: Are all of them Created Equal?

BACKGROUND: Detecting and managing antimicrobial drug interactions (ADIs) is one of the facets of prudent antimicrobial prescribing. Our aim is to compare the capability of several electronic drug-drug interaction (DDI) checkers to detect and report ADIs. METHODS: Six electronic DDI checking platforms were evaluated: Drugs.com®, Medscape®, Epocrates®, Medimecum®, iDoctus®, and Guía IF®. Lexicomp® Drug Interactions was selected as the gold standard. Ten ADIs addressing different mechanisms were evaluated with every electronic DDI checker. For each ADI, we assessed five dimensions and calculated an overall performance score (maximum possible score: 10 points). The explored dimensions were sensitivity (capability to detect ADI), clinical effect (type and severity), mechanism of interaction, recommended action(s), and documentation (quality of evidence and availability of references). RESULTS: The electronic DDI checkers did not detect a significant proportion of the ADI assessed. The overall performance score ranged between 4.4 (Medimecum) and 8.8 (Drugs.com). Drugs.com was the highest ranked platform in four out of five dimensions (sensitivity, effect, mechanism, and recommended action). CONCLUSIONS: There is significant variability in the performance of the available platforms in detecting and assessing ADI. Although some ADI checkers have proven to be very accurate, others missed almost half of the explored interactions.

Young doctors' perspectives on antibiotic use and resistance: a multinational and inter-specialty cross-sectional European Society of Clinical Microbiology and Infectious Diseases (ESCMID) survey.

BACKGROUND: Postgraduate training has the potential to shape the prescribing practices of young doctors. OBJECTIVES: To investigate the practices, attitudes and beliefs on antibiotic use and resistance in young doctors of different specialties. METHODS: We performed an international web-based exploratory survey. Principal component analysis (PCA) and bivariate and multivariate [analysis of variance (ANOVA)] analyses were used to investigate differences between young doctors according to their country of specialization, specialty, year of training and gender. RESULTS: Of the 2366 participants from France, Greece, Italy, Portugal, Slovenia and Spain, 54.2% of young doctors prescribed antibiotics predominantly as instructed by a mentor. Associations between the variability of answers and the country of training were observed across most questions, followed by variability according to the specialty. Very few differences were associated with the year of training and gender. PCA revealed five dimensions of antibiotic prescribing culture: self-assessment of knowledge, consideration of side effects, perception of prescription patterns, consideration of patient sickness and perception of antibiotic resistance. Only the country of specialization (partial η2 0.010-0.111) and the type of specialization (0.013-0.032) had a significant effect on all five identified dimensions (P < 0.01). The strongest effects were observed on self-assessed knowledge and in the perception of antibiotic resistance. CONCLUSIONS: The country of specialization followed by the type of specialization are the most important determinants of young doctors' perspectives on antibiotic use and resistance. The inclusion of competencies in antibiotic use in all specialty curricula and international harmonization of training should be considered.