The nucleoid protein HU positively regulates the expression of type VI secretion systems in Enterobacter cloacae.

Enterobacter cloacae is an emerging pathogen isolated in healthcare-associated infections. A major virulence factor of this bacterium is the type VI secretion system (T6SS). The genome of E. cloacae harbors two T6SS gene clusters (T6SS-1 and T6SS-2), and the functional characterization of both systems showed that these two T6SSs are not expressed under the same conditions. Here, we report that the major histone-like protein HU positively regulates the expression of both T6SSs and, therefore, the function that each T6SS exerts in E. cloacae. Single deletions of the genes encoding the HU subunits (hupA and hupB) decreased mRNA levels of both T6SS. In contrast, the hupA hupB double mutant dramatically affected the T6SS expression, diminishing its transcription. The direct binding of HU to the promoter regions of T6SS-1 and T6SS-2 was confirmed by electrophoretic mobility shift assay. In addition, single and double mutations in the hup genes affected the ability of inter-bacterial killing, biofilm formation, adherence to epithelial cells, and intestinal colonization, but these phenotypes were restored when such mutants were trans-complemented. Our data broaden our understanding of the regulation of HU-mediated T6SS in these pathogenic bacteria. IMPORTANCE: T6SS is a nanomachine that functions as a weapon of bacterial destruction crucial for successful colonization in a specific niche. Enterobacter cloacae expresses two T6SSs required for bacterial competition, adherence, biofilm formation, and intestinal colonization. Expression of T6SS genes in pathogenic bacteria is controlled by multiple regulatory systems, including two-component systems, global regulators, and nucleoid proteins. Here, we reported that the HU nucleoid protein directly activates both T6SSs in E. cloacae, affecting the T6SS-related phenotypes. Our data describe HU as a new regulator involved in the transcriptional regulation of T6SS and its impact on E. cloacae pathogenesis.

Burkholderia vietnamiensis causing infections in noncystic fibrosis patients in a tertiary care hospital in Mexico.

Burkholderia cepacia complex (Bcc) species are opportunistic pathogens widely distributed in the environment and often infect people with cystic fibrosis (CF). This study aims to determine which genomovars of the Bcc can cause infections in non-CF patients from a tertiary care hospital in Mexico and if they carry virulence factors that could increase their pathogenicity. We identified 23 clinical isolates that carry the recA gene. Twenty-two of them belongs to the genomovar V (B. vietnamiensis) and one to the genomovar II (B. multivorans). Thirteen pulsotypes were identified among 22 B. vietnamiensis isolates. All clinical isolates produced biofilm were motile and cytotoxic on murine macrophage-like RAW264.7 and in A549 human lung epithelial cells. In conclusion, B. vietnamiensis causes infections in non-CF patients in a tertiary care hospital in Mexico, rapid identification of this pathogen can help physicians to establish a better antimicrobial treatment.

The Two-Component System CpxRA Represses Salmonella Pathogenicity Island 2 by Directly Acting on the ssrAB Regulatory Operon.

The acquisition of Salmonella pathogenicity island 2 (SPI-2) conferred on Salmonella the ability to survive and replicate within host cells. The ssrAB bicistronic operon, located in SPI-2, encodes the SsrAB two-component system (TCS), which is the central positive regulator that induces the expression of SPI-2 genes as well as other genes located outside this island. On the other hand, CpxRA is a two-component system that regulates expression of virulence genes in many bacteria in response to different stimuli that perturb the cell envelope. We previously reported that the CpxRA system represses the expression of SPI-1 and SPI-2 genes under SPI-1-inducing conditions by decreasing the stability of the SPI-1 regulator HilD. Here, we show that under SPI-2-inducing conditions, which mimic the intracellular environment, CpxRA represses the expression of SPI-2 genes by the direct action of phosphorylated CpxR (CpxR-P) on the ssrAB regulatory operon. CpxR-P recognized two sites located proximal and distal from the promoter located upstream of ssrA. Consistently, we found that CpxRA reduces the replication of Salmonella enterica serovar Typhimurium inside murine macrophages. Therefore, our results reveal CpxRA as an additional regulator involved in the intracellular lifestyle of Salmonella, which in turn adds a new layer to the intricate regulatory network controlling the expression of Salmonella virulence genes. IMPORTANCE SPI-2 encodes a type III secretion system (T3SS) that is a hallmark for the species Salmonella enterica, which is essential for the survival and replication within macrophages. Expression of SPI-2 genes is positively controlled by the two-component system SsrAB. Here, we determined a regulatory mechanism involved in controlling the overgrowth of Salmonella inside macrophages. In this mechanism, CpxRA, a two-component system that is activated by extracytoplasmic stress, directly represses expression of the ssrAB regulatory operon; as a consequence, expression of SsrAB target genes is decreased. Our findings reveal a novel mechanism involved in the intracellular lifestyle of Salmonella, which is expected to sense perturbations in the bacterial envelope that Salmonella faces inside host cells, as the synthesis of the T3SS-2 itself.

Fibrosis quística: patogenia bacteriana y moduladores del CFTR (regulador de conductancia transmembranal de la fibrosis quística).

Cystic fibrosis is an autosomal recessive inherited disease caused by mutations in the cystic fibrosis transmembrane conductance regulator gene (CFTR). CFTR is a protein that transports ions across the membrane of lung epithelial cells. Loss of its function leads to the production of thick sticky mucus, where various bacterial pathogens can establish and adapt, contributing to the gradual loss of lung function. In this review, evidence of the molecular mechanisms used by Pseudomonas aeruginosa and Burkholderia cenocepacia to survive and persist in the pulmonary environment will be provided. Additionally, new therapeutic strategies based on CFTR function modulators will be described.

La fibrosis quística es una enfermedad hereditaria autosómica recesiva que se origina por mutaciones en el gen regulador de conductancia transmembranal de la fibrosis quística (CFTR, cystic fibrosis transmembrane conductance regulator). El CFTR es una proteína que transporta iones a través de la membrana de las células epiteliales pulmonares. La pérdida de su función conlleva la producción de un moco pegajoso y espeso, donde se pueden establecer y adaptar diversos patógenos bacterianos que contribuyen a la pérdida gradual de la función pulmonar. En este artículo de revisión se dará evidencia de los mecanismos moleculares que utilizan Pseudomonas aeruginosa y Burkholderia cenocepacia para sobrevivir y persistir en el ambiente pulmonar. Adicionalmente, se describirán las nuevas estrategias de terapia a base de moduladores de la función del CFTR.

Significance of Molecular Identification of Genomic Variants of Pseudomonas aeruginosa in Children with Cystic Fibrosis.

Pseudomonas aeruginosa is a significant cause of lung infections in patients with cystic fibrosis (CF). Pseudomonas produces a chronic infection that increases the morbidity and mortality in affected individuals. The rapid identification of Pseudomonas in these individuals enables conventional antimicrobial treatment to be started. However, over the years, treatment of P. aeruginosa has become problematic and very challenging due to their intrinsic and acquired antibiotic resistance. Microbiology plays an essential role in determining the antimicrobial susceptibility/resistance profiles of isolated strains, helping to optimize antimicrobial treatment for affected patients. In addition to the conventional susceptibility analysis, whole genome sequencing has emerged as a powerful tool for determining specific genomic variants, both in specific geographic areas and globally. Thus, molecular epidemiologic surveillance could help to establish a better treatment strategy and counter the spread of high-risk, P. aeruginosa variants among CF individuals.

Fibrosis quística: patogenia bacteriana y moduladores del CFTR (regulador de conductancia transmembranal de la fibrosis quística) / Cystic fibrosis: bacterial pathogenesis and CFTR (cystic fibrosis transmembrane conductance regulator) modulators

Resumen La fibrosis quística es una enfermedad hereditaria autosómica recesiva que se origina por mutaciones en el gen regulador de conductancia transmembranal de la fibrosis quística (CFTR, cystic fibrosis transmembrane conductance regulator). El CFTR es una proteína que transporta iones a través de la membrana de las células epiteliales pulmonares. La pérdida de su función conlleva la producción de un moco pegajoso y espeso, donde se pueden establecer y adaptar diversos patógenos bacterianos que contribuyen a la pérdida gradual de la función pulmonar. En este artículo de revisión se dará evidencia de los mecanismos moleculares que utilizan Pseudomonas aeruginosa y Burkholderia cenocepacia para sobrevivir y persistir en el ambiente pulmonar. Adicionalmente, se describirán las nuevas estrategias de terapia a base de moduladores de la función del CFTR.

Abstract Cystic fibrosis is an autosomal recessive inherited disease caused by mutations in the cystic fibrosis transmembrane conductance regulator gene (CFTR). CFTR is a protein that transports ions across the membrane of lung epithelial cells. Loss of its function leads to the production of thick sticky mucus, where various bacterial pathogens can establish and adapt, contributing to the gradual loss of lung function. In this review, evidence of the molecular mechanisms used by Pseudomonas aeruginosa and Burkholderia cenocepacia to survive and persist in the pulmonary environment will be provided. Additionally, new therapeutic strategies based on CFTR function modulators will be described.

SARS-CoV-2: Evolution and Emergence of New Viral Variants.

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the etiological agent responsible for the coronavirus disease 2019 (COVID-19). The high rate of mutation of this virus is associated with a quick emergence of new viral variants that have been rapidly spreading worldwide. Several mutations have been documented in the receptor-binding domain (RBD) of the viral spike protein that increases the interaction between SARS-CoV-2 and its cellular receptor, the angiotensin-converting enzyme 2 (ACE2). Mutations in the spike can increase the viral spread rate, disease severity, and the ability of the virus to evade either the immune protective responses, monoclonal antibody treatments, or the efficacy of current licensed vaccines. This review aimed to highlight the functional virus classification used by the World Health Organization (WHO), Phylogenetic Assignment of Named Global Outbreak (PANGO), Global Initiative on Sharing All Influenza Data (GISAID), and Nextstrain, an open-source project to harness the scientific and public health potential of pathogen genome data, the chronological emergence of viral variants of concern (VOCs) and variants of interest (VOIs), the major findings related to the rate of spread, and the mutations in the spike protein that are involved in the evasion of the host immune responses elicited by prior SARS-CoV-2 infections and by the protection induced by vaccination.

Regulatory Evolution of the phoH Ancestral Gene in Salmonella enterica Serovar Typhimurium.

One important event for the divergence of Salmonella from Escherichia coli was the acquisition by horizontal transfer of the Salmonella pathogenicity island 1 (SPI-1), containing genes required for the invasion of host cells by Salmonella. HilD is an AraC-like transcriptional regulator in SPI-1 that induces the expression of the SPI-1 and many other acquired virulence genes located in other genomic regions of Salmonella. Additionally, HilD has been shown to positively control the expression of some ancestral genes (also present in E. coli and other bacteria), including phoH. In this study, we determined that both the gain of HilD and cis-regulatory evolution led to the integration of the phoH gene into the HilD regulon. Our results indicate that a HilD-binding sequence was generated in the regulatory region of the S. enterica serovar Typhimurium phoH gene, which mediates the activation of promoter 1 of this gene under SPI-1-inducing conditions. Furthermore, we found that repression by H-NS, a histone-like protein, was also adapted on the S. Typhimurium phoH gene and that HilD activates the expression of this gene in part by antagonizing H-NS. Additionally, our results revealed that the expression of the S. Typhmurium phoH gene is also activated in response to low phosphate but independently of the PhoB/R two-component system, known to regulate the E. coli phoH gene in response to low phosphate. Thus, our results indicate that cis-regulatory evolution has played a role in the expansion of the HilD regulon and illustrate the phenomenon of differential regulation of ortholog genes. IMPORTANCE Two mechanisms mediating differentiation of bacteria are well known: acquisition of genes by horizontal transfer events and mutations in coding DNA sequences. In this study, we found that the phoH ancestral gene is differentially regulated between Salmonella Typhimurium and Escherichia coli, two closely related bacterial species. Our results indicate that this differential regulation was generated by mutations in the regulatory sequence of the S. Typhimurium phoH gene and by the acquisition by S. Typhimurium of foreign DNA encoding the transcriptional regulator HilD. Thus, our results, together with those from an increasing number of studies, indicate that cis-regulatory evolution can lead to the rewiring and reprogramming of transcriptional regulation, which also plays an important role in the divergence of bacteria through time.

Cytotoxic activity of Staphylococcus aureus isolates from a cohort of Mexican children with cystic fibrosis.

BACKGROUND: Cystic fibrosis (CF) is a genetic disease in which thick, sticky mucus is produced in the lungs (and other organs) that impairs ciliary clearance, leading to respiratory problems, increased chronic bacterial infections, and decreased lung function. Staphylococcus aureus is one of the primary bacterial pathogens colonizing the lungs of CF patients. This study aimed to characterize the genetic relatedness of S. aureus, its presence in children with CF, and its cytotoxic activity in THP1 cell-derived macrophages (THP1m). METHODS: Genetic relatedness of S. aureus isolates from a cohort of 50 children with CF was determined by pulsed-field gel electrophoresis (PFGE). The VITEK 2 automated system was used to determine antimicrobial susceptibility, and methicillin-resistance S. aureus (MRSA) was determined by diffusion testing using cefoxitin disk. The presence of mecA and lukPV genes was determined by the polymerase chain reaction and cytotoxic activity of S.aureus on THP1m by CytoTox 96® assay. RESULTS: From 51 S. aureus isolates from 50 children with CF, we identified 34pulsotypes by PFGE. Of the 50 children, 12 (24%) were colonized by more than one pulsotype, and 5/34 identified pulsotypes(14.7%) were shared between unrelated children. In addition, 3/34 pulsotypes (8.8%) were multidrug-resistant (MDR), and2/34 (5.9%) were MRSA. Notably, 30/34 pulsotypes (88.2%) exhibited cytotoxicity on THP1m cells and 14/34 (41.2%) alteredTHP1m monolayers. No isolate carried the lukPV gene. CONCLUSIONS: Although a low frequency of MRSA and MDR wasfound among clinical isolates, most of the S. aureus pulsotypes identified were cytotoxic on THP1m.

INTRODUCCIÓN: La fibrosis quística (FQ) es una enfermedad genética en la que se produce moco espeso y pegajoso en los pulmones (y otros órganos), lo que conduce a problemas respiratorios, incremento de las infecciones bacterianas crónicas y disminución de la función pulmonar. Staphylococcus aureus es uno de los principales patógenos que colonizan los pul-mones de los pacientes con FQ. El objetivo de este trabajo fue caracterizar la relación genética de S. aureus, su presencia en niños con FQ y su actividad citotóxica en macrófagos derivados de células THP1 (THP1m). MÉTODOS: La relación gené-tica de los aislados de S. aureus provenientes de una cohorte de 50 pacientes con FQ fue determinada por electroforesis en gel de campo pulsado (PFGE). La sensibilidad a los antimicrobianos se determinó mediante el sistema automatizado VITEK 2, y la resistencia a la meticilina (SARM) mediante la prueba de difusión utilizando discos de cefoxitina. La presen-cia de los genes mecA y lukPV se determinó mediante reacción en cadena de la polimerasa, y la actividad citotóxica de S. aureus sobre células THP1m mediante el ensayo CytoTox96®. RESULTADOS: A partir de 51 aislados de S. aureus provenientes de 50 niños con FQ se identificaron 34 pulsotipos por PFGE. De los 50 niños, 12 (24%) estaban colonizados por más de un pulsotipo y 5 de los 34 pulsotipos (14.7%) los compartían niños que no estaban relacionados. De los 34 pulsotipos, 3 (8.8%) presentaron multirresistencia (MDR) y 2 (5.9%) fueron SARM. Además, 30 pulsotipos (88.2%) fueron citotóxicos sobre células THP1m y 14 (41.2%) alteraron su monocapa. Ninguno de los pulsotipos presentó el gen lukPV. CONCLUSIONES: Aunque se encontró una baja frecuencia de SARM y MDR en los aislados, la mayoría de los pulsotipos de S. aureus identificados fueron citotóxicos para células THP1m.

cAMP Receptor Protein Positively Regulates the Expression of Genes Involved in the Biosynthesis of Klebsiella oxytoca Tilivalline Cytotoxin.

Klebsiella oxytoca is a resident of the human gut. However, certain K. oxytoca toxigenic strains exist that secrete the nonribosomal peptide tilivalline (TV) cytotoxin. TV is a pyrrolobenzodiazepine that causes antibiotic-associated hemorrhagic colitis (AAHC). The biosynthesis of TV is driven by enzymes encoded by the aroX and NRPS operons. In this study, we determined the effect of environmental signals such as carbon sources, osmolarity, and divalent cations on the transcription of both TV biosynthetic operons. Gene expression was enhanced when bacteria were cultivated in tryptone lactose broth. Glucose, high osmolarity, and depletion of calcium and magnesium diminished gene expression, whereas glycerol increased transcription of both TV biosynthetic operons. The cAMP receptor protein (CRP) is a major transcriptional regulator in bacteria that plays a key role in metabolic regulation. To investigate the role of CRP on the cytotoxicity of K. oxytoca, we compared levels of expression of TV biosynthetic operons and synthesis of TV in wild-type strain MIT 09-7231 and a Δcrp isogenic mutant. In summary, we found that CRP directly activates the transcription of the aroX and NRPS operons and that the absence of CRP reduced cytotoxicity of K. oxytoca on HeLa cells, due to a significant reduction in TV production. This study highlights the importance of the CRP protein in the regulation of virulence genes in enteric bacteria and broadens our knowledge on the regulatory mechanisms of the TV cytotoxin.

TBC1D10C is a cytoskeletal functional linker that modulates cell spreading and phagocytosis in macrophages.

Cell spreading and phagocytosis are notably regulated by small GTPases and GAP proteins. TBC1D10C is a dual inhibitory protein with GAP activity. In immune cells, TBC1D10C is one of the elements regulating lymphocyte activation. However, its specific role in macrophages remains unknown. Here, we show that TBC1D10C engages in functions dependent on the cytoskeleton and plasma membrane reorganization. Using ex vivo and in vitro assays, we found that elimination and overexpression of TBC1D10C modified the cytoskeletal architecture of macrophages by decreasing and increasing the spreading ability of these cells, respectively. In addition, TBC1D10C overexpression contributed to higher phagocytic activity against Burkholderia cenocepacia and to increased cell membrane tension. Furthermore, by performing in vitro and in silico analyses, we identified 27 TBC1D10C-interacting proteins, some of which were functionally classified as protein complexes involved in cytoskeletal dynamics. Interestingly, we identified one unreported TBC1D10C-intrinsically disordered region (IDR) with biological potential at the cytoskeleton level. Our results demonstrate that TBC1D10C shapes macrophage activity by inducing reorganization of the cytoskeleton-plasma membrane in cell spreading and phagocytosis. We anticipate our results will be the basis for further studies focused on TBC1D10C. For example, the specific molecular mechanism in Burkholderia cenocepacia phagocytosis and functional analysis of TBC1D10C-IDR are needed to further understand its role in health and disease.

Bacterial Subversion of Autophagy in Cystic Fibrosis.

Cystic fibrosis (CF) is a genetic disease affecting more than 70,000 people worldwide. It is caused by a mutation in the cftr gene, a chloride ion transporter localized in the plasma membrane of lung epithelial cells and other organs. The loss of CFTR function alters chloride, bicarbonate, and water transport through the plasma membrane, promoting the production of a thick and sticky mucus in which bacteria including Pseudomonas aeruginosa and Burkholderia cenocepacia can produce chronic infections that eventually decrease the lung function and increase the risk of mortality. Autophagy is a well-conserved lysosomal degradation pathway that mediates pathogen clearance and plays an important role in the control of bacterial infections. In this mini-review, we describe the principal strategies used by P. aeruginosa and B. cenocepacia to survive and avoid microbicidal mechanisms within the autophagic pathway leading to the establishment of chronic inflammatory immune responses that gradually compromise the lung function and the life of CF patients.

Whole Genome Sequencing of Pediatric Klebsiella pneumoniae Strains Reveals Important Insights Into Their Virulence-Associated Traits.

Klebsiella pneumoniae is recognized as a common cause of nosocomial infections and outbreaks causing pneumonia, septicemia, and urinary tract infections. This opportunistic bacterium shows an increasing acquisition of antibiotic-resistance genes, which complicates treatment of infections. Hence, fast reliable strain typing methods are paramount for the study of this opportunistic pathogen's multi-drug resistance genetic profiles. In this study, thirty-eight strains of K. pneumoniae isolated from the blood of pediatric patients were characterized by whole-genome sequencing and genomic clustering methods. Genes encoding ß-lactamase were found in all the bacterial isolates, among which the bla SHV variant was the most prevalent (53%). Moreover, genes encoding virulence factors such as fimbriae, capsule, outer membrane proteins, T4SS and siderophores were investigated. Additionally, a multi-locus sequence typing (MLST) analysis revealed 24 distinct sequence types identified within the isolates, among which the most frequently represented were ST76 (16%) and ST70 (11%). Based on LPS structure, serotypes O1 and O3 were the most prevalent, accounting for approximately 63% of all infections. The virulence capsular types K10, K136, and K2 were present in 16, 13, and 8% of the isolates, respectively. Phylogenomic analysis based on virtual genome fingerprints correlated with the MLST data. The phylogenomic reconstruction also denoted association between strains with a higher abundance of virulence genes and virulent serotypes compared to strains that do not possess these traits. This study highlights the value of whole-genomic sequencing in the surveillance of virulence attributes among clinical K. pneumoniae strains.

Emergence of GES-19-producing Pseudomonas aeruginosa exoU+ belonging to the global high-risk clone ST235 in cystic fibrosis infection.

The emergence of high-risk clones of priority pathogens exhibiting convergence of antimicrobial resistance and virulence is a critical issue worldwide. In a previous study, an extensively drug-resistant Pseudomonas aeruginosa was isolated from a chronically colonized pediatric patient with cystic fibrosis (CF). In this study, we analyzed genomic data of this strain (CF023-Psa42), extracting clinically and epidemiologically relevant information (i.e., the antimicrobial resistome, virulome, and sequence type). In this regard, we report the emergence of GES-19 (extended-spectrum ß-lactamase)-producing P. aeruginosa with genotype exoU+. The CF023-Psa42 strain exhibited a broad resistome, belonging to the international high-risk clone sequence type ST235. The blaGES-19 gene was located on a class 1 integron, along to aac(6')-33, aac(6')-Ib-cr, blaOXA-2, aadA1, sul1, and qacEΔ1 resistance genes. Relevant virulence genes such as lasA (proteolysis and elastolysis), toxA (exotoxin A), alg (alginate biosynthesis operon), and exoU (toxin of type III secretion systems) were predicted. Our findings reveal the convergence of broad resistome and virulome in P. aeruginosa ST235. Genomic surveillance is essential to monitor the emergence and dissemination of priority pathogens with epidemiological success.

An incoherent feedforward loop formed by SirA/BarA, HilE and HilD is involved in controlling the growth cost of virulence factor expression by Salmonella Typhimurium.

An intricate regulatory network controls the expression of Salmonella virulence genes. The transcriptional regulator HilD plays a central role in this network by controlling the expression of tens of genes mainly required for intestinal colonization. Accordingly, the expression/activity of HilD is highly regulated by multiple factors, such as the SirA/BarA two-component system and the Hcp-like protein HilE. SirA/BarA positively regulates translation of hilD mRNA through a regulatory cascade involving the small RNAs CsrB and CsrC, and the RNA-binding protein CsrA, whereas HilE inhibits HilD activity by protein-protein interaction. In this study, we show that SirA/BarA also positively regulates translation of hilE mRNA through the same mentioned regulatory cascade. Thus, our results reveal a paradoxical regulation exerted by SirA/BarA-Csr on HilD, which involves simultaneous opposite effects, direct positive control and indirect negative control through HilE. This kind of regulation is called an incoherent type-1 feedforward loop (I1-FFL), which is a motif present in certain regulatory networks and represents a complex biological problem to decipher. Interestingly, our results, together with those from a previous study, indicate that HilE, the repressor component of the I1-FFL reported here (I1-FFLSirA/BarA-HilE-HilD), is required to reduce the growth cost imposed by the expression of the genes regulated by HilD. Moreover, we and others found that HilE is necessary for successful intestinal colonization by Salmonella. Thus, these findings support that I1-FFLSirA/BarA-HilE-HilD cooperates to control the precise amount and activity of HilD, for an appropriate balance between the growth cost and the virulence benefit generated by the expression of the genes induced by this regulator. I1-FFLSirA/BarA-HilE-HilD represents a complex regulatory I1-FFL that involves multiple regulators acting at distinct levels of gene expression, as well as showing different connections to the rest of the regulatory network governing Salmonella virulence.

Pseudomonas Aeruginosa: Genetic Adaptation, A Strategy for its Persistence in Cystic Fibrosis.

Cystic fibrosis (CF) is a progressive autosomal recessive genetic disease that principally affects the respiratory and digestive systems. It is a chronic disease that has no cure. Symptoms often include chronic cough, lung infections, and shortness of breath. Children with cystic fibrosis present failure to thrive as manifested by low weight and height for age. CF is caused by mutations in the cystic fibrosis transmembrane conductance regulator (cftr) gene that codes for a cell membrane protein of epithelial tissues and affects multiple organ systems in the human body. Mutations on the CFTR causes dysfunctional electrolyte regulation affecting intracellular water content. Defective CFTR function in airways produce a dehydrated and sticky mucus that leads the establishment of bacterial chronic infection that ultimate decrease the lung function. During the first decade of life, affected individuals are colonized principally by non typable Haemophilus influenzae and Staphylococcus aureus. During the second decade, Pseudomonas aeruginosa becomes the most dominant pathogen and persists throughout the remainder of their lives. In this work, we describe the mechanisms used by P. aeruginosa to adapt and persist in lungs of individuals with cystic fibrosis.

Interferon-gamma-activated macrophages infected with Burkholderia cenocepacia process and present bacterial antigens to T-cells by class I and II major histocompatibility complex molecules.

Burkholderia cenocepacia is an emerging opportunistic pathogen for people with cystic fibrosis and chronic granulomatous disease. Intracellular survival in macrophages within a membrane-bound vacuole (BcCV) that delays acidification and maturation into lysosomes is a hallmark of B. cenocepacia infection. Intracellular B. cenocepacia induce an inflammatory response leading to macrophage cell death by pyroptosis through the secretion of a bacterial deamidase that results in the activation of the pyrin inflammasome. However, how or whether infected macrophages can process and present B. cenocepacia antigens to activate T-cells has not been explored. Engulfed bacterial protein antigens are cleaved into small peptides in the late endosomal major histocompatibility class II complex (MHC) compartment (MIIC). Here, we demonstrate that BcCVs and MIICs have overlapping features and that interferon-gamma-activated macrophages infected with B. cenocepacia can process bacterial antigens for presentation by class II MHC molecules to CD4+ T-cells and by class I MHC molecules to CD8+ T-cells. Infected macrophages also release processed bacterial peptides into the extracellular medium, stabilizing empty class I MHC molecules of bystander cells. Together, we conclude that BcCVs acquire MIIC characteristics, supporting the notion that macrophages infected with B. cenocepacia contribute to establishing an adaptive immune response against the pathogen.

Pseudomonas aeruginosa Isolates From a Cohort of Mexican Children With Cystic Fibrosis Show Adaptation to a Chronic Phenotype.

BACKGROUND: Long-term persistence of Pseudomonas aeruginosa in the lung of individuals with cystic fibrosis (CF) is associated with progressive selection of diverse genotypes and phenotypes. This bacterial adaptation leads to chronic infection and increased morbidity and mortality. The aim of this study was to establish the prevalence, clonal relatedness, antimicrobial susceptibility and virulence-associated phenotypes of P. aeruginosa isolates in a cohort of 50 Mexican children with CF-associated chronic lung infection. METHODS: Clonal relatedness of P. aeruginosa isolates was verified by pulsed-field gel electrophoresis. The antimicrobial susceptibility was determined by an automated system that performs bacterial identificación and antibiotic susceptibility testing (VITEK 2) and/or broth microdilution method. Biofilm formation was quantified with the crystal violet method; swarming motility was measured on soft agar, and susceptibility to normal human serum determined by reduction of colony formed units (CFUs). RESULTS: High prevalence of P. aeruginosa colonization among Mexican children with CF was confirmed; 20% (10/49) of clones identified showed a multidrug-resistant phenotype and 8.2% (4/49) an extensive drug resistance phenotype; 26.5% (13/49) of the isolates were resistant to colistin, 42.9% (21/49) presented a phenotype of adaptation associated with chronic infection and 79.6% (39/49) showed increased ability to survive in normal human serum. CONCLUSIONS: This cohort of children with CF reveals that colonizing P. aeruginosa strains predominantly display resistance to several first-line antibiotics, although most isolates were susceptible to meropenem and tobramycin; 42.9% of isolates showed a phenotype consistent with adaptation to chronic lung infection.

Draft Genome Sequence of a Pseudomonas aeruginosa Sequence Type 3351 Strain Exhibiting High-Level Resistance to Polymyxins in a Pediatric Patient with Cystic Fibrosis in Mexico.

Here, we present the draft genome sequence of a Pseudomonas aeruginosa isolate (strain CF16053) belonging to a novel sequence type (ST), ST3351, isolated from a pediatric patient with cystic fibrosis (CF). CF16053 shows high-level resistance to polymyxins associated with mutations in the pmrB gene. Biofilm, pyoverdine, exotoxin A, and type III secretion system (T3SS) genes were identified.

Clinical pathology, diagnostic and treatment in SARS-CoV-2 infection. / Patología clínica, diagnóstico y tratamiento en la infección por SARS-CoV-2.

SARS-CoV-2 is a new virus causing an infection and illness referred to as COVID-19. As of July 7th of 2020, this virus has been associated worldwide with over 12 million of infections and more than 550,000 deaths. Transmission rate of SARS-CoV-2 in the population is high, and the origin of this coronavirus appears to be related to some species of the bat. However, scientific information related to the pathogenesis, and immune response to COVID-19 changes rapidly, which is why the aim of this work is to provide recent information related to an exacerbated inflammatory immune response which causes multiorgan failure and patient death. The timely identification of infected individuals will be key to stop the spread of infection and in severe cases to establish optimal strategies to reduce the risk of death in critically ill patients. In this review, we have considered the latest findings collected from the clinical studies, diagnostic tests, and treatment for COVID-19. Information presented here will help to the better understanding of this disease.

El SARS-CoV-2 es un nuevo virus que causa la enfermedad denominada COVID-19. Este virus ha generado hasta el 7 de julio de 2020 12 millones de contagios y más de 550 000 muertes en todo el mundo. Se sabe que la tasa de transmisión es muy alta y su origen está relacionado con una especie del murciélago. Sin embargo, la información científica relacionada con la COVID-19 cambia rápidamente, por lo que este trabajo tiene como objetivo aportar información reciente y relacionada con el desarrollo de la respuesta inflamatoria exacerbada, que con frecuencia causa falla orgánica múltiple y muerte del paciente. La rápida identificación de los individuos infectados es clave para detener la propagación de esta enfermedad y en los casos más graves establecer estrategias que permitan la reducción de la infección y del riesgo de muerte. En esta revisión, hemos considerado los últimos hallazgos recopilados de los estudios clínicos, pruebas diagnósticas y de tratamiento para COVID-19. La información presentada en este trabajo contribuirá al entendimiento de esta enfermedad.