Posts filed under ‘Biología Molecular’

Tailoring Antimicrobial Susceptibility Testing to Individual Species of Coagulase-Negative Staphylococci: Next Up, Staphylococcus epidermidis

Journal of Clinical Microbiology December 2019 V.57 N.12

Accurate detection of methicillin resistance among staphylococci is vital for patient care. Methicillin resistance is most commonly mediated by acquisition of the mecA gene, which encodes an altered penicillin binding protein, PBP2a.

Application of phenotypic methods to detect mecA-mediated beta-lactam resistance in staphylococci is becoming more complex as species-specific differences are identified among coagulase-negative staphylococci (CoNS).

Previously, interpretative criteria and antimicrobial susceptibility testing (AST) methods specific to the CoNS group were used to evaluate Staphylococcus epidermidis.

A manuscript by S. N. Naccache, K. Callan, C.-A. D. Burnham, M. A. Wallace, et al. (J Clin Microbiol 57:e00961-19, 2019, details experiments revealing that S. epidermidis, the most common clinically isolated CoNS, requires tailored use of previously described methods and interpretive criteria to reliably identify the presence of mecAmediated methicillin resistance.





November 23, 2019 at 10:30 am

Perspective – Eastern Equine Encephalitis Virus — Another Emergent Arbovirus in the United States

NEJM November 21, 219 V.381 P.1989-1992

David M. Morens, M.D., Gregory K. Folkers, M.S., M.P.H., and Anthony S. Fauci, M.D.

Humans have always lived in intimate association with arthropods that transmit pathogens between humans or from animals to humans. About 700,000 deaths due to vectorborne diseases occur globally each year, according to World Health Organization estimates. In the summer and fall of 2019, nine U.S. states have reported 36 human cases (14 of them fatal) of one of the deadliest of these diseases: eastern equine encephalitis (EEE), an arthropod-borne viral (arboviral) disease transmitted by mosquitoes. In recent years, the Americas have witnessed a steady stream of other emerging or reemerging arboviruses, such as dengue, West Nile, chikungunya, Zika, and Powassan, as well as increasing numbers of travel-related cases of various other arboviral infections. This year’s EEE outbreaks may thus be a harbinger of a new era of arboviral emergences……



November 21, 2019 at 8:06 am

Efficacy of a Tetravalent Dengue Vaccine in Healthy Children and Adolescents

NEJM November 21, 219 V.381 P.2009-2019

Shibadas Biswal, M.D., Humberto Reynales, M.D., Ph.D., Xavier Saez-Llorens, M.D., Pio Lopez, M.D., Charissa Borja-Tabora, M.D., Pope Kosalaraksa, M.D., Chukiat Sirivichayakul, M.D., Veerachai Watanaveeradej, M.D., Luis Rivera, M.D., Felix Espinoza, M.D., LakKumar Fernando, M.D., Reynaldo Dietze, M.D., et al., for the TIDES Study Group*


Dengue, a mosquito-borne viral disease, was designated a World Health Organization top 10 threat to global health in 2019.


We present primary efficacy data from part 1 of an ongoing phase 3 randomized trial of a tetravalent dengue vaccine candidate (TAK-003) in regions of Asia and Latin America in which the disease is endemic. Healthy children and adolescents 4 to 16 years of age were randomly assigned in a 2:1 ratio (stratified according to age category and region) to receive two doses of vaccine or placebo 3 months apart. Participants presenting with febrile illness were tested for virologically confirmed dengue by serotype-specific reverse-transcriptase polymerase chain reaction. The primary end point was overall vaccine efficacy in preventing virologically confirmed dengue caused by any dengue virus serotype.


Of the 20,071 participants who were given at least one dose of vaccine or placebo (safety population), 19,021 (94.8%) received both injections and were included in the per-protocol analysis. The overall vaccine efficacy in the safety population was 80.9% (95% confidence interval [CI], 75.2 to 85.3; 78 cases per 13,380 [0.5 per 100 person-years] in the vaccine group vs. 199 cases per 6687 [2.5 per 100 person-years] in the placebo group). In the per-protocol analyses, vaccine efficacy was 80.2% (95% CI, 73.3 to 85.3; 61 cases of virologically confirmed dengue in the vaccine group vs. 149 cases in the placebo group), with 95.4% efficacy against dengue leading to hospitalization (95% CI, 88.4 to 98.2; 5 hospitalizations in the vaccine group vs. 53 hospitalizations in the placebo group). Planned exploratory analyses involving the 27.7% of the per-protocol population that was seronegative at baseline showed vaccine efficacy of 74.9% (95% CI, 57.0 to 85.4; 20 cases of virologically confirmed dengue in the vaccine group vs. 39 cases in the placebo group). Efficacy trends varied according to serotype. The incidence of serious adverse events was similar in the vaccine group and placebo group (3.1% and 3.8%, respectively).


TAK-003 was efficacious against symptomatic dengue in countries in which the disease is endemic. (Funded by Takeda Vaccines; TIDES number, NCT02747927. opens in new tab.)



November 21, 2019 at 8:05 am

Omadacycline as a promising new agent for the treatment of infections with Mycobacterium abscessus.

Omadacycline: A Potential New Treatment for Mycobacterium abscessus


J Antimicrob Chemother. October 1, 2019 V.74 N.10 P.2930-2933.

Bax HI1,2, de Vogel CP2, Mouton JW2, de Steenwinkel JEM2.

Author information

1 Department of Internal Medicine, Division of Infectious Diseases, Erasmus University Medical Centre, Rotterdam, The Netherlands.

2 Department of Medical Microbiology and Infectious Diseases, Erasmus University Medical Centre, Rotterdam, The Netherlands.



Despite intensive treatment regimens, the outcome of Mycobacterium abscessus infections is extremely poor and thus novel treatment regimens are needed. Although tigecycline seems to be one of the best options currently available, its long-term use is hampered by severe toxic side effects as well as the need for intravenous administration and the relatively high concentrations required for efficacy.


To assess the in vitro activity of omadacycline against M. abscessus and compare it with the activity of tigecycline.


The concentration- and time-dependent killing capacities of omadacycline and tigecycline against M. abscessus subspecies abscessus were determined using a time-kill kinetics assay. Time-kill curves as well as concentration-effect curves were generated.


Time-kill curves showed strong concentration-dependent antimicrobial activity for both omadacycline and tigecycline. Omadacycline showed inhibition of mycobacterial growth at 4 mg/L and mycobacterial killing at concentrations ≥16 mg/L. Tigecycline showed mycobacterial killing at concentrations ≥4 mg/L, achieving elimination at concentrations ≥16 mg/L. The concentration-effect curves after 7 days of exposure showed stasis, 1 log mycobacterial killing and 2 log mycobacterial killing at 3.3, 4.0 and 4.8 mg/L for omadacycline and 2.2, 2.7 and 3.4 mg/L for tigecycline, respectively.


The results of this in vitro study on omadacycline activity, together with its favourable (pharmacokinetic) properties, suggest that omadacycline is a potential new agent for the treatment of M. abscessus infections



November 18, 2019 at 7:07 pm

Measles virus infection diminishes preexisting antibodies that offer protection from other pathogens.

Measles Virus Infection Negatively Affects Host Immune Status

New evidence shows that measles infection decreases the breadth and titers of preexisting antibodies to a wide variety of pathogens


Science. November 1, 2019 V.366 N.6465 P.599-606.

Mina MJ1,2,3, Kula T4,2, Leng Y4, Li M2, de Vries RD5, Knip M6,7, Siljander H6,7, Rewers M8, Choy DF9, Wilson MS9, Larman HB10, Nelson AN11, Griffin DE11, de Swart RL5, Elledge SJ1,2,12.

Author information

1 Division of Genetics, Brigham and Women’s Hospital, Howard Hughes Medical Institute, Boston, MA 02115, USA.

2 Department of Genetics, Harvard Medical School, Boston, MA 02115, USA.

3 Department of Pathology, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA 02115, USA.

4 Division of Genetics, Brigham and Women’s Hospital, Howard Hughes Medical Institute, Boston, MA 02115, USA.

5 Department of Viroscience, Postgraduate School of Molecular Medicine, Erasmus MC, University Medical Centre Rotterdam, 3015 CN, Rotterdam, Netherlands.

6 Children’s Hospital, University of Helsinki and Helsinki University Hospital, 00290 Helsinki, Finland.

7 Research Program for Clinical and Molecular Metabolism, University of Helsinki, 00014 Helsinki, Finland.

8 Barbara Davis Center for Diabetes, University of Colorado School of Medicine, Denver, CO 80045, USA.

9 Genentech Inc., South San Francisco, CA 94080, USA.

10 Department of Pathology, Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA.

11 W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21205, USA.

12Program in Virology, Harvard Medical School, Boston, MA 02115, USA.


Measles virus is directly responsible for more than 100,000 deaths yearly. Epidemiological studies have associated measles with increased morbidity and mortality for years after infection, but the reasons why are poorly understood. Measles virus infects immune cells, causing acute immune suppression. To identify and quantify long-term effects of measles on the immune system, we used VirScan, an assay that tracks antibodies to thousands of pathogen epitopes in blood. We studied 77 unvaccinated children before and 2 months after natural measles virus infection. Measles caused elimination of 11 to 73% of the antibody repertoire across individuals. Recovery of antibodies was detected after natural reexposure to pathogens. Notably, these immune system effects were not observed in infants vaccinated against MMR (measles, mumps, and rubella), but were confirmed in measles-infected macaques. The reduction in humoral immune memory after measles infection generates potential vulnerability to future infections, underscoring the need for widespread vaccination.



November 18, 2019 at 7:04 pm

Diagnosis and Treatment of Adults with Community-acquired Pneumonia. An Official Clinical Practice Guideline of the American Thoracic Society and Infectious Diseases Society of America.

Am J Respir Crit Care Med. October 1, 2019  V.200 N.7  e45-e67.

Metlay JP, Waterer GW, Long AC, Anzueto A, Brozek J, Crothers K, et al.


This document provides evidence-based clinical practice guidelines on the management of adult patients with community-acquired pneumonia.


A multidisciplinary panel conducted pragmatic systematic reviews of the relevant research and applied Grading of Recommendations, Assessment, Development, and Evaluation methodology for clinical recommendations.


The panel addressed 16 specific areas for recommendations spanning questions of diagnostic testing, determination of site of care, selection of initial empiric antibiotic therapy, and subsequent management decisions. Although some recommendations remain unchanged from the 2007 guideline, the availability of results from new therapeutic trials and epidemiological investigations led to revised recommendations for empiric treatment strategies and additional management decisions.


The panel formulated and provided the rationale for recommendations on selected diagnostic and treatment strategies for adult patients with community-acquired pneumonia.


Este documento proporciona pautas de práctica clínica basadas en evidencia sobre el manejo de pacientes adultos con NAC.


Un panel multidisciplinario realizó revisiones sistemáticas pragmáticas de la investigación relevante y aplicó la metodología de calificación de recomendaciones, evaluación, desarrollo y evaluación para recomendaciones clínicas.


El panel abordó 16 áreas específicas para recomendaciones que abarcan preguntas sobre pruebas de diagnóstico, determinación del sitio de atención, selección de terapia ATB empírica inicial y decisiones de manejo posteriores. Aunque algunas recomendaciones permanecen sin cambios con respecto a la guía de 2007, la disponibilidad de resultados de nuevos ensayos terapéuticos e investigaciones epidemiológicas condujo a recomendaciones revisadas para estrategias de tratamiento empírico y decisiones de manejo adicionales.


El panel formuló y proporcionó la justificación de las recomendaciones sobre estrategias seleccionadas de diagnóstico y tratamiento para pacientes adultos con NAC.



November 15, 2019 at 7:59 am

Control and Elimination of Extensively Drug-Resistant Acinetobacter baumanii in an Intensive Care Unit

Emerging Infectious Diseases November 2019 V.25 N.10 P.1928-1931

We decreased antimicrobial drug consumption in an intensive care unit in Lebanon by changing to colistin monotherapy for extensively drug-resistant Acinetobacter baumanii infections.

We saw a 78% decrease of A. baumanii in sputum and near-elimination of blaoxa-23-carrying sequence type 2 clone over the 1-year study.

Non–A. baumanii multidrug-resistant infections remained stable.



November 13, 2019 at 7:02 am

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