Reproducibility of drug-induced effects on the contractility of an engineered heart tissue derived from human pluripotent stem cells.

Introduction: Engineered heart tissues (EHTs) are three-dimensional culture platforms with cardiomyocytes differentiated from human pluripotent stem cells (hPSCs) and were designed for assaying cardiac contractility. For drug development applications, EHTs must have a stable function and provide reproducible results. We investigated these properties with EHTs made with different tissue casting batches and lines of differentiated hPSC-cardiomyocytes and analyzed them at different times after being fabricated. Methods: A video-optical assay was used for measuring EHT contractile outputs, and these results were compared with results from motion traction analysis of beating hPSC-cardiomyocytes cultured as monolayers in two-dimensional cultures. The reproducibility of induced contractile variations was tested using compounds with known mechanistic cardiac effects (isoproterenol, EMD-57033, omecamtiv mecarbil, verapamil, ranolazine, and mavacamten), or known to be clinically cardiotoxic (doxorubicin, sunitinib). These drug-induced variations were characterized at different electrical pacing rates and variations in intracellular calcium transients were also assessed in EHTs. Results: To ensure reproducibility in experiments, we established EHT quality control criteria based on excitation-contraction coupling and contractile sensitivity to extracellular calcium concentration. In summary, a baseline contractile force of 0.2 mN and excitation-contraction coupling of EHTs were used as quality control criteria to select suitable EHTs for analysis. Overall, drug-induced contractile responses were similar between monolayers and EHTs, where a close relationship was observed between contractile output and calcium kinetics. Contractile variations at multiple time points after adding cardiotoxic compounds were also detectable in EHTs. Discussion: Reproducibility of drug-induced effects in EHTs between experiments and relative to published work on these cellular models was generally observed. Future applications for EHTs may require additional mechanistic criteria related to drug effects and cardiac functional outputs to be measured in regard to specific contexts of use.

The E. coli pathobiont LF82 encodes a unique variant of σ70 that results in specific gene expression changes and altered phenotypes.

LF82, an adherent invasive Escherichia coli pathobiont, is associated with ileal Crohn's disease, an inflammatory bowel disease of unknown etiology. Although LF82 contains no virulence genes, it carries several genetic differences, including single nucleotide polymorphisms (SNPs), that distinguish it from nonpathogenic E. coli. We have identified and investigated an extremely rare SNP that is within the highly conserved rpoD gene, encoding σ70, the primary sigma factor for RNA polymerase. We demonstrate that this single residue change (D445V) results in specific transcriptome and phenotypic changes that are consistent with multiple phenotypes observed in LF82, including increased antibiotic resistance and biofilm formation, modulation of motility, and increased capacity for methionine biosynthesis. Our work demonstrates that a single residue change within the bacterial primary sigma factor can lead to multiple alterations in gene expression and phenotypic changes, suggesting an underrecognized mechanism by which pathobionts and other strain variants with new phenotypes can emerge.

Glycosaminoglycans affect endothelial to mesenchymal transformation, proliferation, and calcification in a 3D model of aortic valve disease.

Calcific nodules form in the fibrosa layer of the aortic valve in calcific aortic valve disease (CAVD). Glycosaminoglycans (GAGs), which are normally found in the valve spongiosa, are located local to calcific nodules. Previous work suggests that GAGs induce endothelial to mesenchymal transformation (EndMT), a phenomenon described by endothelial cells' loss of the endothelial markers, gaining of migratory properties, and expression of mesenchymal markers such as alpha smooth muscle actin (α-SMA). EndMT is known to play roles in valvulogenesis and may provide a source of activated fibroblast with a potential role in CAVD progression. In this study, a 3D collagen hydrogel co-culture model of the aortic valve fibrosa was created to study the role of EndMT-derived activated valvular interstitial cell behavior in CAVD progression. Porcine aortic valve interstitial cells (PAVIC) and porcine aortic valve endothelial cells (PAVEC) were cultured within collagen I hydrogels containing the GAGs chondroitin sulfate (CS) or hyaluronic acid (HA). The model was used to study alkaline phosphatase (ALP) enzyme activity, cellular proliferation and matrix invasion, protein expression, and calcific nodule formation of the resident cell populations. CS and HA were found to alter ALP activity and increase cell proliferation. CS increased the formation of calcified nodules without the addition of osteogenic culture medium. This model has applications in the improvement of bioprosthetic valves by making replacements more micro-compositionally dynamic, as well as providing a platform for testing new pharmaceutical treatments of CAVD.

Upcycling Compact Discs for Flexible and Stretchable Bioelectronic Applications.

Electronic waste is a global issue brought about by the short lifespan of electronics. Viable methods to relieve the inundated disposal system by repurposing the enormous amount of electronic waste remain elusive. Inspired by the need for sustainable solutions, this study resulted in a multifaceted approach to upcycling compact discs. The once-ubiquitous plates can be transformed into stretchable and flexible biosensors. Our experiments and advanced prototypes show that effective, innovative biosensors can be developed at a low-cost. An affordable craft-based mechanical cutter allows pre-determined patterns to be scored on the recycled metal, an essential first step for producing stretchable, wearable electronics. The active metal harvested from the compact discs was inert, cytocompatible, and capable of vital biopotential measurements. Additional studies examined the material's resistive emittance, temperature sensing, real-time metabolite monitoring performance, and moisture-triggered transience. This sustainable approach for upcycling electronic waste provides an advantageous research-based waste stream that does not require cutting-edge microfabrication facilities, expensive materials, and high-caliber engineering skills.

Shear and endothelial induced late-stage calcific aortic valve disease-on-a-chip develops calcium phosphate mineralizations.

Calcific aortic valve disease (CAVD) is an active pathobiological process leading to severe aortic stenosis, where the only treatment is valve replacement. Late-stage CAVD is characterized by calcification, disorganization of collagen, and deposition of glycosaminoglycans, such as chondroitin sulfate (CS), in the fibrosa. We developed a three-dimensional microfluidic device of the aortic valve fibrosa to study the effects of shear stress (1 or 20 dyne per cm2), CS (1 or 20 mg mL-1), and endothelial cell presence on calcification. CAVD chips consisted of a collagen I hydrogel, where porcine aortic valve interstitial cells were embedded within and porcine aortic valve endothelial cells were seeded on top of the matrix for up to 21 days. Here, we show that this CAVD-on-a-chip is the first to develop human-like calcified nodules varying in calcium phosphate mineralization maturity resulting from high shear and endothelial cells, specifically di- and octa-calcium phosphates. Long-term co-culture microfluidic studies confirmed cell viability and calcium phosphate formations throughout 21 days. Given that CAVD has no targeted therapies, the creation of a physiologically relevant test-bed of the aortic valve could lead to advances in preclinical studies.

Investigation of Bacterial Infections Among Patients Treated With Umbilical Cord Blood-Derived Products Marketed as Stem Cell Therapies.

Importance: The number of clinics marketing stem cell products for joint diseases, chronic pain, and most recently, COVID-19, has increased despite warnings from the US Food and Drug Administration that stem cell products for these and other indications have not been proven safe or effective. Objective: To examine bacterial infections in 20 patients who received umbilical cord blood-derived products marketed as stem cell treatment. Design, Setting, and Participants: This case series is a national public health investigation including case-finding, medical record review and abstraction, and laboratory investigation, including sterility testing of products and whole-genome sequencing of patient and product isolates. Participants included patients who developed bacterial infections following administration of umbilical cord blood-derived products marketed as stem cell treatment during August 2017 to September 2018. Data analysis was performed from March 2019 to September 2021. Exposures: Umbilical cord blood-derived products marketed as stem cell treatment. Main Outcomes and Measures: Data were collected on patient infections and exposures. The Centers for Disease Control and Prevention performed sterility testing on undistributed and distributed vials of product marketed as stem cell treatment and performed whole-genome sequencing to compare patient and product bacterial isolates. Results: Culture-confirmed bacterial infections were identified in 20 patients (median [range] age, 63 [2-89] years; 13 male patients [65%]) from 8 US states who sought stem cell treatment for conditions including pain, osteoarthritis, rheumatoid arthritis, and injury; all but 1 required hospitalization. The most frequently isolated bacteria from patients with infections were common enteric species, including Escherichia coli (14 patients) and Enterobacter cloacae (7 patients). Of unopened, undistributed products sampled for testing, 65% (22 of 34 vials) were contaminated with at least 1 of 16 bacterial species, mostly enteric. A patient isolate from Arizona matched isolates obtained from products administered to patients in Florida, and patient isolates from Texas matched undistributed product sent from the company in California. Conclusions and Relevance: Unapproved stem cell products can expose patients to serious risks without proven benefit. Sequencing results suggest a common source of extensive contamination, likely occurring during the processing of cord blood into product. Patients and health care practitioners who are considering the use of unapproved products marketed as stem cell treatment should be aware of their unproven benefits and potential risks, including serious infections.

A phage-encoded nucleoid associated protein compacts both host and phage DNA and derepresses H-NS silencing.

Nucleoid Associated Proteins (NAPs) organize the bacterial chromosome within the nucleoid. The interaction of the NAP H-NS with DNA also represses specific host and xenogeneic genes. Previously, we showed that the bacteriophage T4 early protein MotB binds to DNA, co-purifies with H-NS/DNA, and improves phage fitness. Here we demonstrate using atomic force microscopy that MotB compacts the DNA with multiple MotB proteins at the center of the complex. These complexes differ from those observed with H-NS and other NAPs, but resemble those formed by the NAP-like proteins CbpA/Dps and yeast condensin. Fluorescent microscopy indicates that expression of motB in vivo, at levels like that during T4 infection, yields a significantly compacted nucleoid containing MotB and H-NS. motB overexpression dysregulates hundreds of host genes; ∼70% are within the hns regulon. In infected cells overexpressing motB, 33 T4 late genes are expressed early, and the T4 early gene repEB, involved in replication initiation, is up ∼5-fold. We postulate that MotB represents a phage-encoded NAP that aids infection in a previously unrecognized way. We speculate that MotB-induced compaction may generate more room for T4 replication/assembly and/or leads to beneficial global changes in host gene expression, including derepression of much of the hns regulon.

Effect of testosterone and estrogen supplementation on the resistance to systemic Candida albicans infection in mice.

Candida species are the 4th leading cause of nosocomial infections in the US affecting both men and women. Since males of many species can be more susceptible to infections than females, we investigated whether male mice were more susceptible to systemic Candida albicans (C. albicans) infection and if sex hormones were responsible for sex-dependent susceptibility to this infection. Non-gonadectomized or gonadectomized mice were supplemented with sustained release 5α-dihydrotestosterone (5αDHT) or 17-ß-estradiol (E2) using subcutaneous pellet implantation. Mice were challenged intravenously with 5 × 105 C. albicans/mouse seven days after pellet implantation and monitored for survival and weight change. We observed that male mice were more susceptible to systemic C. albicans infection than female mice while gonadectomized male mice were as resistant to the C. albicans infection as female mice. 5αDHT supplementation of gonadectomized female or male mice increased their susceptibility to the yeast infection while E2 supplementation of gonadectomized male mice did not increase their resistance to the infection. Overall, our results strongly suggest that testosterone plays an important role in decreasing resistance to systemic C. albicans infection.

No place like home: A national study on firearm-related injuries in the American household.

BACKGROUND: We aimed to examine the prevalence of, and describe factors associated with, firearm-related injuries in American households. METHODS: Using the 2010-2016 ACS-TQIP database, all ICD-9/10 external causes of injury for firearm-related injuries were queried with the place of occurrence designated as "home". Causes of injury were identified as assault, intentional self-injury, and unintentional injury. Univariate then multivariable regression analyses were performed to identify factors associated with each injury type. RESULTS: 12,657 firearm-related injuries in households were identified. Of those, 49.9% were victims of assault, 35.7% were intentional self-injury, and 14.4% were unintentional. Mortality was highest among self-inflicted injuries (52.4%), followed by assault (12.9%), and unintentional injuries (5.9%). On multivariable analysis, age <45 years, African-American race, and drug use were independently associated with an injury secondary to assault. Age >65 years, White race, psychiatric illness, and alcohol use disorder were independently associated with intentional self-injury. White and American-Indian race were independently associated with unintentional injuries. CONCLUSIONS: Assault is the most common cause of home-related firearm injury requiring hospitalization, while intentional self-injury is the most lethal.

The Bacteriophage T4 MotB Protein, a DNA-Binding Protein, Improves Phage Fitness.

The lytic bacteriophage T4 employs multiple phage-encoded early proteins to takeover the Escherichia coli host. However, the functions of many of these proteins are not known. In this study, we have characterized the T4 early gene motB, located in a dispensable region of the T4 genome. We show that heterologous production of MotB is highly toxic to E. coli, resulting in cell death or growth arrest depending on the strain and that the presence of motB increases T4 burst size 2-fold. Previous work suggested that motB affects middle gene expression, but our transcriptome analyses of T4 motBam vs. T4 wt infections reveal that only a few late genes are mildly impaired at 5 min post-infection, and expression of early and middle genes is unaffected. We find that MotB is a DNA-binding protein that binds both unmodified host and T4 modified [(glucosylated, hydroxymethylated-5 cytosine, (GHme-C)] DNA with no detectable sequence specificity. Interestingly, MotB copurifies with the host histone-like proteins, H-NS and StpA, either directly or through cobinding to DNA. We show that H-NS also binds modified T4 DNA and speculate that MotB may alter how H-NS interacts with T4 DNA, host DNA, or both, thereby improving the growth of the phage.

Preference assessment training via self-instruction: A replication and extension.

We examined the effects of a self-instructional and feedback package on participants' implementation of a paired-stimulus preference assessment. Specifically, in Experiment 1, we used a multiple baseline design across participants to replicate and extend the results of Graff and Karsten (2012) by evaluating the effectiveness of their self-instructional manual. A majority of the participants (i.e., 5 of 7 undergraduate students and 4 of 5 in-home behavior technicians) achieved mastery with the self-instructional package. The remaining participants met the mastery criterion after brief modeling and feedback sessions. In Experiment 2, we identified the most effective component of the feedback condition from Experiment 1 when a self-instructional package was not sufficient. Brief feedback sessions in which participants received a list of the targeted responses plus information regarding accuracy of emitted responses was sufficient for 5 of 6 participants to achieve mastery.

Quantifying Physical Activity Levels and Sleep in Hemodialysis Patients Using a Commercially Available Activity Tracker.

BACKGROUND/AIMS: Hemodialysis (HD) patients are less active than their healthy counterparts and frequently experience poor sleep. Our aims were to objectively quantify activity and sleep quality in HD patients of an urban population and to determine the effect of providing feedback on activity. METHODS: Activity parameters and sleep parameters were collected by a commercially available activity tracker in 29 chronic HD patients. Patients in the feedback group were provided with their activity and sleep data during each HD treatment. Questionnaires were administered at the beginning and at the end of the study. RESULTS: On average, patients walked 8,454 steps/day and slept 349 min/night. Only 28% of the patients were sedentary, defined as walking <5,000 steps/day. Providing feedback did not increase the activity in this urban population. Patients walked significantly less on Sundays compared to other days of the week: 7,024 steps on Sundays vs. 8,633 steps on HD days and 8,732 on non-HD days. It was also found that patients experienced poor sleep quality. HD treatments during shift 1 (6 a.m. to 10 a.m.) interfered with sleep patterns. Most patients reported that physical activity became more important to them after the 5-week period. The tracking device was very well accepted. CONCLUSION: Interventions to increase physical activity on Sundays could improve physical activity levels overall. Prospective studies are necessary to further explore the use of tracking devices to identify patients at risk and to implement targeted interventions.

Esclerodermia localizada: serie de casos en un hospital general y revisión de la literatura / Localized scleroderma: cases report in a general hospital and literature review

La esclerodermia localizada o morfea es una entidad inflamatoria que se caracteriza por fibrosis de la piel y tejido subyacente, se manifiesta clínicamente por zonas induradas y delimitadas con un halo eritematovioláceo, que luego se tornan hipopigmentadas o hiperpigmentadas. Se recolectaron 11 casos de esclerodermia localizada en el periodo de 1990 a 2014 en el Hospital Nacional Dos de Mayo de los cuales se excluyeron 4 por no presentar registros fotográficos. De Los 7 casos estudiados, uno correspondió a morfea circunscrita; cinco a morfea lineal, dentro de Los cuales se incluyeron dos casos de síndrome de Parry-Romberg que fueron seguidos desde el inicio de su enfermedad; una a morfea mixta y una a morfea panesclerótica. Correspondieron al sexo femenino 71 % de todos los casos, el rango de edad de los pacientes fue de 10 a 23 años y el tiempo promedio de evolución de su enfermedad desde el momento del diagnóstico fue de 3,9 años. Cinco (5) de Los pacientes presentaron evolución favorable, con remisión parcial de la enfermedad, y dos (2) pacientes, con síndrome de Parry-Romberg, fallecieron por complicaciones asociadas a la afectación neurológica.

Morphea or localized scleroderma is an inflammatory entity characterized by fibrosis of the skin and underlying tissue, is clinically manifested by areas thickened and delimited with a halo erythematous becoming then hypopigmented and hyperpigmented. Eleven cases of scleroderma in the period of 1990 to 2014 in the Hospital Nacional Dos de Mayo from which we excluded 4 by not showing photographic records were collected. Of the 7 cases studied, one corresponded to circumscribed morphea; five a linear morphea, within which included two cases of Parry-Romberg syndrome who were followed from the beginning of his illness; a mixed morphea and one to pansclerotic morphea; 71 % of all cases corresponded to the female sex, the age of the patients ranged from 10 to 23 years and the average time of evolution of his disease from the time of diagnosis was 3,9 years. Five of the patients presented a positive evolution with partial remission of the disease and two patients, with Parry-Romberg syndrome, died of complications associated with the neurological compromise.

It's a non-dialysis day Do you know how your patient is doing? A case for research into interdialytic activity.

Hemodialysis (HD) patients are less active than their healthy counterparts; this is associated with higher mortality. Healthcare workers observe their patients only during HD, which accounts for about 7% of the week. Knowing more about what occurs in between sessions, particularly with respect to physical activity, may improve patient care and prognosis. Yet without a standard method to measure interdialytic activity, it is difficult to compare the effect of interventions. However, it is unclear how interdialytic activity can be accurately measured. Since activity associated with quality of life is multi-dimensional, objective and subjective tools should be used in conjunction. While commercially available tracking devices can be seamlessly incorporated into everyday life and can increase awareness of user's activity, their validation is needed in the HD population. Fertile topics for research should include the relationship between objective and subjective measures in HD patients, and the investigation of physical activity in non-ambulatory HD patients.

Manifestaciones cutáneas de enfermedades asociadas a infección por HTLV-1 / Cutaneous manifestations of diseases associated with HTLV-I infection

Se presentan siete casos, cuatro mujeres y tres varones. La edad promedio de los pacientes fue 29,5 años, incluido un niño. Todos fueron seropositivos a HTLV-l; y, dos de ellos también lo fueron para el VIH. Solo en dos casos se planteó inicialmente como posible diagnóstico de infección por HTLV-l. El diagnóstico clínico e histopatológico correspondió a dermatitis infectiva, uno; estrongiloidiasis sistémica, dos; sarna costrosa, dos; leucemia/linfoma de células T del adulto, uno; y, una presentación atípica de carcinoma escamoso infiltrante. Se concluye que existe una baja sospecha clínica inicial de diagnóstico de enfermedades sistémicas con manifestaciones cutáneas asociadas a la infección por HTLV-l, no obstante, que se realiza la práctica médica en un área endémica...

Seven cases, four women and three men, are presented. The average age was 29,5 year-old, including a child. All were seropositive to HTLV-l and two of them were also for HN. Only in two cases was initially raised a possible diagnosis of HTLV-l infection. The clinical and histopathological diagnosis corresponded to infective dermatitis, one; systemic strongyloidiasis, two; crusted scabies, two; adult T-cell leukemia/lymphoma, one; and, an atypical presentation of invasive squamous cell carcinoma. lt is concluded that there is a low initial suspicion for clinical diagnosis of cutaneous manifestations of generalized diseases associated to HTLV-l infection despite of we live in an endemic area...

Effect of Delta-9-tetrahydrocannabinol on mouse resistance to systemic Candida albicans infection.

Delta-9-tetrahydrocannabinol (Δ9-THC), the psychoactive component of marijuana, is known to suppress the immune responses to bacterial, viral and protozoan infections, but its effects on fungal infections have not been studied. Therefore, we investigated the effects of chronic Δ9-THC treatment on mouse resistance to systemic Candida albicans (C. albicans) infection. To determine the outcome of chronic Δ9-THC treatment on primary, acute systemic candidiasis, c57BL/6 mice were given vehicle or Δ9-THC (16 mg/kg) in vehicle on days 1-4, 8-11 and 15-18. On day 19, mice were infected with 5×10(5) C. albicans. We also determined the effect of chronic Δ9-THC (4-64 mg/kg) treatment on mice infected with a non-lethal dose of 7.5×10(4) C. albicans on day 2, followed by a higher challenge with 5×10(5) C. albicans on day 19. Mouse resistance to the infection was assessed by survival and tissue fungal load. Serum cytokine levels were determine to evaluate the immune responses. In the acute infection, chronic Δ9-THC treatment had no effect on mouse survival or tissue fungal load when compared to vehicle treated mice. However, Δ9-THC significantly suppressed IL-12p70 and IL-12p40 as well as marginally suppressed IL-17 versus vehicle treated mice. In comparison, when mice were given a secondary yeast infection, Δ9-THC significantly decreased survival, increased tissue fungal burden and suppressed serum IFN-γ and IL-12p40 levels compared to vehicle treated mice. The data showed that chronic Δ9-THC treatment decreased the efficacy of the memory immune response to candida infection, which correlated with a decrease in IFN-γ that was only observed after the secondary candida challenge.

[The gold standard in diabetic foot treatment: total contact cast]. / Estándar de oro en el manejo del pie diabético: yeso de contacto total.

In patients with diabetes, foot complications remain one of the main health issues, with ulcers representing one of the most common. These ulcerations originate from repetitive trauma on a foot with neuropathy. Inadequate care of the diabetic foot may lead to one of the gravest complications of the diabetic foot: amputation. The key to the treatment of the diabetic foot is the control of comorbidities (glucose levels and vascular disease), debridement, exudate control with the available modern dressings, treatment of infection, and offloading the affected foot. A common error in this basic treatment is the method used for offloading, leading to delayed healing as a result, and maybe even amputation. For this purpose we propose the total contact cast considered the "gold standard" in diabetic foot offloading. The objective of the present review is to present the existing evidence in the medical literature on the effectiveness of its use for healing diabetic foot ulcers and hence preventing amputations.

Nivel de conocimientos sobre la influenza A H1N1 en los trabajadores de salud del Hospital Nacional Arzobispo Loayza, Perú / Level of knowledge of the influenza A H1N1 in health workers of the Hospital Nacional Arzobispo Loayza, Peru

Introducción: La influenza pandémica A H1N1 se ha diseminado por todo el mundo y ha cobrado numerosas vidas en un corto período de tiempo. Por ello, es necesario que el personal de salud tenga los conocimientos suficientes para prevenir una alta mortalidad por dicha enfermedad. Objetivo: Determinar el nivel de conocimientos acerca de la transmisión, cuadro clínico, diagnóstico, tratamiento y prevención de la influenza A H1N1 y los factores asociados a un nivel adecuado de conocimientos. Material y métodos: Se desarrolló un estudio transversal en médicos asistentes, médicos residentes, licenciados en enfermería e internos de medicina del Hospital Nacional Arzobispo Loayza (HNAL), los cuales fueron seleccionados mediante un muestreo por cuotas y a quienes se les aplicó un cuestionario autoadministrado. Resultados: El nivel de conocimientos fue adecuado en 60.6% de los trabajadores. El análisis bivariado mostró como factores asociados al adecuado conocimiento, el ser médico asistente [OR=2.33 (1.42-3.82); p=0.0009] o médico residente [OR=2.75 (1.5-5.04); p=0.001]. El análisis multivariado mostró que no había asociación alguna entre las variables estudiadas y el adecuado conocimiento, sin embargo los factores asociados a un nivel de conocimientos inadecuado fueron haber tenido como principal fuente de información a la prensa [OR=2.15 (1.32-4.78); p=0.005] y ser enfermera (p=0.029). Conclusiones: El 60.6% de los profesionales de salud del HNAL tienen un buen nivel de conocimientos acerca de la influenza A H1N1 y el ser médico asistente o residente está asociado a ello.

Background: Pandemic influenza A H1N1 has had a rapid worldwide spread and has killed many people so far. For these reasons, it is necessary that health professionals have enough knowledge to prevent high mortality for this overwhelming pandemic. Objective: To determine the level of knowledge about transmission, clinical presentation, diagnosis, treatment and preventive measures in health professionals and to identify factors that can be associated with an adequate level of knowledge. Methods: A transversal study was performed in physicians, residents, nurses and medical interns working at Hospital Nacional Arzobispo Loayza (HNAL), whom were selected by a quota sampling and responded a self administer questionnaire. Results: The level of knowledge was adequate in a 60.6% of workers. The bivariate analysis showed that the associated factors to adequate knowledge were being physician [OR=2.33 (1.42- 3.82); p=0.0009] or resident [OR=2.75 (1.5-5.04); p=0.001]. Multivariate analysis showed that none of the factors was associated with an adequate level of knowledge, however the associated factors with an inadequate level of knowledge were: having selected press media as the main source of information [OR=2.15 (1.32-4.78); p=0.005] and working as a nurse [OR=2.603 (1.105 - 6.129); p=0.029]. Conclusions: 60.6% of the health professionals from HNAL have an adequate level of knowledge about influenza A H1N1 and being a physician o a resident is associated with this.