Development and evaluation of a low cost IgG ELISA test based in RBD protein for COVID-19.

Serology tests for SARS-CoV-2 have proven to be important tools to fight against the COVID-19 pandemic. These serological tests can be used in low-income and remote areas for patient contact tracing, epidemiologic studies and vaccine efficacy evaluations. In this study, we used a semi-stable mammalian episomal expression system to produce high quantities of the receptor-binding domain-RBD of SARS-CoV-2 in a simple and very economical way. The recombinant antigen was tested in an in-house IgG ELISA for COVID-19 with a panel of human sera. A performance comparison of this serology test with a commercial test based on the full-length spike protein showed 100% of concordance between tests. Thus, this serological test can be an attractive and inexpensive option in scenarios of limited resources to face the COVID-19 pandemic.

Origin of modern syphilis and emergence of a pandemic Treponema pallidum cluster.

The abrupt onslaught of the syphilis pandemic that started in the late fifteenth century established this devastating infectious disease as one of the most feared in human history1. Surprisingly, despite the availability of effective antibiotic treatment since the mid-twentieth century, this bacterial infection, which is caused by Treponema pallidum subsp. pallidum (TPA), has been re-emerging globally in the last few decades with an estimated 10.6 million cases in 2008 (ref. 2). Although resistance to penicillin has not yet been identified, an increasing number of strains fail to respond to the second-line antibiotic azithromycin3. Little is known about the genetic patterns in current infections or the evolutionary origins of the disease due to the low quantities of treponemal DNA in clinical samples and difficulties in cultivating the pathogen4. Here, we used DNA capture and whole-genome sequencing to successfully interrogate genome-wide variation from syphilis patient specimens, combined with laboratory samples of TPA and two other subspecies. Phylogenetic comparisons based on the sequenced genomes indicate that the TPA strains examined share a common ancestor after the fifteenth century, within the early modern era. Moreover, most contemporary strains are azithromycin-resistant and are members of a globally dominant cluster, named here as SS14-Ω. The cluster diversified from a common ancestor in the mid-twentieth century subsequent to the discovery of antibiotics. Its recent phylogenetic divergence and global presence point to the emergence of a pandemic strain cluster.

Prevalencia de la infección por Chlamydia trachomatis y factores de riesgo de infecciones transmisibles sexualmente en estudiantes universitarios / Prevalence of Chlamydia trachomatis infection and factors with the risk of acquiring sexually transmitted infections in college students

La infección genital por Chlamydia trachomatis es considerada en la actualidad una de las causas más frecuentes de infecciones transmisibles sexualmente (ITS) a nivel mundial y afecta principalmente al grupo de jóvenes menores de 25 años. El objetivo de este estudio fue determinar la prevalencia de la infección por C. trachomatis en alumnos ingresantes a la Universidad Nacional del Sur (Bahía Blanca, Argentina) y evaluar los factores de riesgo para la adquisición de ITS. Participaron en el estudio 204 jóvenes de edad media de 19 años, que remitieron una muestra de orina de primera micción y respondieron a una encuesta anónima. La investigación de C. trachomatis se realizó sobre 114 muestras válidas mediante una técnica de amplificación génica, cuyo blanco molecular es el gen ompA. Se detectaron 4 casos de infección por C. trachomatis, lo que implicó una prevalencia del 3,5 %. Los factores de riesgo que demostraron estar asociados con la adquisición de esta ITS fueron un historial de 7 o más parejas desde el comienzo de las relaciones sexuales y el contacto con una nueva pareja sexual en los últimos 4 meses. La prevalencia de infección por C. trachomatis reflejó una moderada circulación de este microorganismo en la población estudiada. Si bien algunos aspectos revelados en las encuestas sugieren una población de bajo riesgo para la adquisición de ITS en general, otros datos evidencian lo contrario y alertan sobre la necesidad de incrementar la vigilancia y desarrollar acciones de concienciación y prevención en esta población.

Chlamydia trachomatis genital infection is nowadays considered one of the most frequent causes of sexually transmitted infections (STI) in the world, mainly affecting the group of young people under 25 years old. The aim of this study was to determine the prevalence of C. trachomatis infection in newly admitted students to Universidad Nacional del Sur, Bahía Blanca, Argentina, and to evaluate the risk factors to acquire STI. For that purpose, 204 young college students with a mean age of 19 were involved in this study. Each participant delivered a sample of first-void urine and completed a questionnaire which was then submitted anonymously. The research for C. trachomatis was done on 114 valid samples through a technique of DNA amplification, whose molecular target was the gene ompA. Four cases of infection by C. trachomatis were detected with a prevalence of 3.5 %. The risks factors associated to the infection were a history of 7 or more partners since the start of sexual activity and contact with a new sexual partner in the last 4 months. The prevalence of such infection reflects a moderate circulation of this microorganism in the studied population. This fact, along with some aspects shown by the questionnaire results, would characterize a population having a low risk profile for acquiring STIs. However, some other information obtained from the questionnaires gave some opposite evidence, which would alert us on the need of keeping watch, raising awareness and implementing preventive actions in this population.

Genetic diversity of Chlamydia among captive birds from central Argentina.

To study the occurrence of Chlamydia spp. and their genetic diversity, we analysed 793 cloacal swabs from 12 avian orders, including 76 genera, obtained from 80 species of asymptomatic wild and captive birds that were examined with conventional nested polymerase chain reaction and quantitative polymerase chain reaction. Chlamydia spp. were not detected in wild birds; however, four species (Chlamydia psittaci, Chlamydia pecorum, Chlamydia pneumoniae and Chlamydia gallinacea) were identified among captive birds (Passeriformes, n = 20; Psittaciformes, n = 15; Rheiformes, n = 8; Falconiformes n = 2; Piciformes n = 2; Anseriformes n = 1; Galliformes n = 1; Strigiformes n = 1). Two pathogens (C. pneumoniae and C. pecorum) were identified simultaneously in samples obtained from captive birds. Based on nucleotide-sequence variations of the ompA gene, three C. psittaci-positive samples detected were grouped into a cluster with the genotype WC derived from mammalian hosts. A single positive sample was phylogenetically related to a new strain of C. gallinacea. This report contributes to our increasing understanding of the abundance of Chlamydia in the animal kingdom.