Non-canonical start codons confer context-dependent advantages in carbohydrate utilization for commensal E. coli in the murine gut.

Resource competition is a driver of gut microbiota composition. Bacteria can outcompete metabolically similar rivals through the limitation of shared growth-fuelling nutrients. The mechanisms underlying this remain unclear for bacteria with identical sets of metabolic genes. Here we analysed the lactose utilization operon in the murine commensal Escherichia coli 8178. Using in vitro and in vivo approaches, we showed that translation of the lactose utilization repressor gene lacI from its native non-canonical GTG start codon increases the basal expression of the lactose utilization cluster, enhancing adaptation to lactose consumption. Consequently, a strain carrying the wild type lacI GTG start codon outperformed the lacI ATG start codon mutant in the mouse intestine. This advantage was attenuated upon limiting host lactose intake through diet shift or altering the mutant frequency, emphasizing the context-dependent effect of a single nucleotide change on the bacterial fitness of a common member of the gut microbiota. Coupled with a genomic analysis highlighting the selection of non-ATG start codons in sugar utilization regulator genes across the Enterobacteriaceae family, our data exposed an unsuspected function of non-canonical start codons in metabolic competition.

Commensal E. coli limits Salmonella gut invasion during inflammation by producing toxin-bound siderophores in a tonB-dependent manner.

The gastrointestinal tract is densely colonized by a polymicrobial community known as the microbiota which serves as primary line of defence against pathogen invasion. The microbiota can limit gut-luminal pathogen growth at different stages of infection. This can be traced to specific commensal strains exhibiting direct or indirect protective functions. Although these mechanisms hold the potential to develop new approaches to combat enteric pathogens, they remain far from being completely described. In this study, we investigated how a mouse commensal Escherichia coli can outcompete Salmonella enterica serovar Typhimurium (S. Tm). Using a salmonellosis mouse model, we found that the commensal E. coli 8178 strain relies on a trojan horse trap strategy to limit S. Tm expansion in the inflamed gut. Combining mutants and reporter tools, we demonstrated that inflammation triggers the expression of the E. coli 8178 antimicrobial microcin H47 toxin which, when fused to salmochelin siderophores, can specifically alter S. Tm growth. This protective function was compromised upon disruption of the E. coli 8178 tonB-dependent catecholate siderophore uptake system, highlighting a previously unappreciated crosstalk between iron intake and microcin H47 activity. By identifying the genetic determinants mediating S. Tm competition, our work not only provides a better mechanistic understanding of the protective function displayed by members of the gut microbiota but also further expands the general contribution of microcins in bacterial antagonistic relationships. Ultimately, such insights can open new avenues for developing microbiota-based approaches to better control intestinal infections.

Endogenous Nodal switches Wnt interpretation from posteriorization to germ layer differentiation in geometrically constrained human pluripotent cells.

The Wnt pathway is essential for inducing the primitive streak, the precursor of the mesendoderm, as well as setting anterior-posterior coordinates. How Wnt coordinates these diverse activities remains incompletely understood. Here, we show that in Wnt-treated human pluripotent cells, endogenous Nodal signaling is a crucial switch between posteriorizing and primitive streak-including activities. While treatment with Wnt posteriorizes cells in standard culture, in micropatterned colonies, higher levels of endogenously induced Nodal signaling combine with exogenous Wnt to drive endoderm differentiation. Inhibition of Nodal signaling restores dose-dependent posteriorization by Wnt. In the absence of Nodal inhibition, micropatterned colonies undergo spontaneous, elaborate morphogenesis concomitant with endoderm differentiation even in the absence of added extracellular matrix proteins like Matrigel. Our study shows how Wnt and Nodal combinatorially coordinate germ layer differentiation with AP patterning and establishes a system to study a natural self-organizing morphogenetic event in in vitro culture.

Characterization of 58 STRs and 94 SNPs with the ForenSeq™ DNA signature prep kit in Mexican-Mestizos from the Monterrey city (Northeast, Mexico).

BACKGROUND: STR allele frequency databases from populations are necessary to take full advantage of the increased power of discrimination offered by massively parallel sequencing (MPS) platforms. MATERIAL AND METHODS: For this reason, we sequenced 58 STRs (aSTRs, X-STRs, and Y-STRs) and 94 identity informative SNPs (iiSNPs) on 105 Mestizo (admixed) individuals from Monterrey City (Northeast, Mexico), with the Primer Set-A of the ForenSeq™ DNA Signature Prep Kit. RESULTS: Most of the STR markers were in Hardy Weinberg equilibrium, with a few exceptions. We found 346 different length-based alleles for these 58 STRs; nevertheless, they became 528 alleles when the sequence was assessed. The combined power of discrimination from autosomal STRs (aSTRs) was -virtually- 100% in both length and sequence-based alleles, while the power of exclusion was 99.9999999976065 and 99.9999999999494%, respectively. Haplotypes based on X-STRs and Y-STRs showed 100% of discriminatory capacity. CONCLUSIONS: These results provide -for the first time- forensic genomic population data from Mexico necessary for interpretation in kinship and criminal analyses.

Low Incidence and Mortality by SARS-CoV-2 Infection Among Healthcare Workers in a Health National Center in Mexico: Successful Establishment of an Occupational Medicine Program.

Background: Coronavirus disease 2019 (COVID-19) is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Healthcare workers (HCWs) constitute a population which is significantly affected by SARS-CoV-2 infection worldwide. In Mexico, the Instituto Nacional de Enfermedades Respiratorias (INER) is the principal national reference of respiratory diseases. Aim: To evaluate the efficiency of the INER-POL-TRAB-COVID19 program to mitigate the SARS-CoV-2 infection risk among the INER-healthcare workers (INER-HCW). Methods: Currently, the INER has 250 beds and 200 respiratory ventilators to support COVID-19 patients in critical condition. On March 1st, 2020, the INER-POL-TRAB-COVID19 program was launched to mitigate the SARS-CoV-2 infection risk among the INER-HCW. Findings: From March 1st to October 1st, 2020, 71.5% of INER-HCWs were tested for SARS-CoV-2 infection, and 77% of them were frontline workers. Among the tested INER-HCWs, 10.4% were positive for SARS-CoV-2 infection. Nonetheless, nosocomial infection represented only 3.8% of the cases and the mortality was null. Fifty-three of INER-HCWs positive to SARS-CoV-2 had a negative test 42-56 days post-diagnosis and were returned to service. Finally, although a change in the PPE implemented on May 11th, 2020, the incidence of SARS-CoV-2 infection was not affected. Conclusion: INER has a lower incidence of HCWs infected with SARS-CoV-2 as compared to the mean of the national report. The implementation of the INER-POL-TRAB-COVID19 program is efficient to decrease the risk of infection among the HCWs. Our findings suggest that the implementation of a similar program at a national level can be helpful to provide a safe environment to HCWs and to prevent the collapse of health institutions.

Effect of Content and Surface Modification of Fique Fibers on the Properties of a Low-Density Polyethylene (LDPE)-Al/Fique Composite.

This work presents the physical-thermal and mechanical characterization of a low-density polyethylene (LDPE)-Al matrix composite material that was obtained from reinforcing recycled (post-consumer) long-life Tetra Pak packages with fique natural fibers from southwestern Colombia. The fique was subjected to three chemical treatments to modify its surface (alkalinization, silanization and pre-impregnation with polyethylene) to increase the quality of its interfaces. Additionally, panels with 10%, 20%, and 30% v/v of fiber were manufactured by the hot compression molding. The mechanical properties of the different composite materials showed that the pre-impregnation treatment promoted a significant increase in the tensile and flexural properties with respect to the fiber-reinforced composite without surface modification. Additionally, in materials with 30% fibers that were treated with pre-impregnation, there was a decrease in the water absorption capacity of 53.15% when compared to composites made with 30% native fibers. Finally, increases in the fiber content mainly caused better mechanical performances, which increased as a direct function of the amount of fique incorporated.

Undertreatment of human immunodeficiency virus in psychiatric inpatients: a cross-sectional study of seroprevalence and associated factors.

BACKGROUND: The aims of this study were to evaluate the prevalence of HIV and its associated demographic and clinical factors among psychiatric inpatients of a general hospital. METHODS: This was a single-center, observational, cross-sectional study that included patients consecutively admitted to our unit aged 16 years or older and with no relevant cognitive problems. The patients were evaluated using a semistructured interview and an appropriate test for HIV infection. RESULTS: Of the 637 patients who were screened, 546 (86%) who consented to participate were included in the analyses. Twenty-five (4.6%, 95% confidence interval [CI] 3.0-6.8) patients were HIV-positive. The prevalence was higher among patients with substance misuse (17.4%, 95% CI 9.7-28.8). All except one of the 25 patients knew of their seropositive condition prior to participation in the study. Only 14 (56%) of the 25 seropositive patients had previously received pharmacological treatment for their infection. According to the multiple logistic regression analysis, the likelihood of HIV infection was lower in patients with higher levels of education and higher among patients who were single, had history of intravenous drug use, and had an HIV-positive partner, particularly if they did not use condoms. Among the patients with HIV infection, 18 (72%) had a history of suicide attempts compared with 181 (34.7%) of the patients without HIV infection (relative risk 2.1, 95% CI 1.6-2.7; P<0.001). CONCLUSION: HIV infection is highly prevalent in patients admitted to a psychiatric unit, especially those with a diagnosis of substance misuse. Seropositive patients show very poor treatment adherence. The risk of suicide seems to be very high in this population. Implementing interventions to reduce the suicide risk and improve adherence to antiretroviral therapy and psychotropic medications seems crucial.

Lifetime sexual behavior of psychiatric inpatients.

INTRODUCTION: Sexual life of psychiatric patients, including risk behaviors related to sexually transmitted diseases, remains a poorly studied area, especially in those with severe mental illnesses. AIMS: To assess some aspects of lifetime sexual behavior of psychiatric inpatients. METHODS: Patients consecutively admitted to a psychiatric unit in a general hospital were interviewed about partner-related lifetime sexual behavior. MAIN OUTCOME MEASURES: A semi-structured interview developed by the authors was used to collect information concerning their general sexual experience throughout life, homosexual and heterosexual relations, and relations with partners who were intravenous drug users (IVDU), HIV carriers or suffering from AIDS, and with sex workers. In each of these areas, time elapsed since last sexual contact; number of partners in previous year, frequency of these relations and condom use were investigated. RESULTS: Five hundred forty-six patients (306 men and 240 women) were assessed, and 87.7% of them reported sexual relations at some point during their life. Of these, 90% reported heterosexual and 10% homosexual or bisexual sexual contacts. Further, 11.06% had had at least one partner who was an IVDU; 8.1% an HIV-positive partner, and 32.4% (50% of the men) had paid for sex. Overall 49.79% of the total sample reported never using condoms in their sexual relations, with similar percentages for those with HIV-positive (46%) and IVDU (47%) partners. Of those who paid for sex, 29% never used condoms. CONCLUSIONS: Psychiatric patients admitted to a general hospital psychiatric unit have sexual experience close to the general population, with a higher percentage of homosexual contacts and lower rates of condom use, even in higher risk situations, such as men having sex with men, and partners who are HIV-positive or IVDUs. This information obliges clinicians to systematically explore the sexual behavior of psychiatric patients, evaluate risk behaviors, and adopt measures to promote safe sex practices in this population.