We propose that severe RSV infection in very young infants is associated with poor blood proinflammatory cytokine production, low counts of CD8+ T cells and with a greater activity of a group of NK cells, that are independent of the major histocompatibility complex class Ib recognition system.

Artículo de publicación ISIBackground Adult community-acquired pneumonia (CAP) is a relevant worldwide cause of morbidity and mortality, however the aetiology often remains uncertain and the therapy is empirical. We applied conventional and molecular diagnostics to identify viruses and atypical bacteria associated with CAP in Chile. Methods We used sputum and blood cultures, IgG/IgM serology and molecular diagnostic techniques (PCR, reverse transcriptase PCR) for detection of classical and atypical bacteria (Mycoplasma pneumoniae, Chlamydia pneumoniae, Legionella pneumoniae) and respiratory viruses (adenovirus, respiratory syncytial virus (RSV), human metapneumovirus, influenza virus, parainfluenzavirus, rhinovirus, coronavirus) in adults >18 years old presenting with CAP in Santiago from February 2005 to September 2007. Severity was qualified at admission by Fine’s pneumonia severity index. Results Overall detection in 356 enrolled adults were 92 (26%) cases of a single bacterial pathogen, 80 (22%) cases of a single viral pathogen, 60 (17%) cases with mixed bacterial and viral infection and 124 (35%) cases with no identified pathogen. Streptococcus pneumoniae and RSV were the most common bacterial and viral pathogens identified. Infectious agent detection by PCR provided greater sensitivity than conventional techniques. To our surprise, no relationship was observed between clinical severity and sole or coinfections. Conclusions The use of molecular diagnostics expanded the detection of viruses and atypical bacteria in adults with CAP, as unique or coinfections. Clinical severity and outcome were independent of the aetiological agents detected

Some respiratory tract infections remain unexplained despite extensive testing for common pathogens. Nasopharyngeal aspirates (NPAs) from 120 Chilean infants from Santiago with acute lower respiratory tract infections were analysed by viral metagenomics, revealing the presence of nucleic acids from anelloviruses, adenovirus-associated virus and 12 known respiratory viral pathogens. A single sequence read showed translated protein similarity to cycloviruses. We used inverse PCR to amplify the complete circular ssDNA genome of a novel cyclovirus we named CyCV-ChileNPA1. Closely related variants were detected using PCR in the NPAs of three other affected children that also contained anelloviruses. This report increases the current knowledge of the genetic diversity of cycloviruses whose detection in multiple NPAs may reflect a tropism for human respiratory tissues.Cycloviruses, members of a proposed genus within the family Circoviridae, have a circular ssDNA genome of approximately 2 kb (Li et al., 2010). Genetically highly diverse cycloviruses were initially found in the faeces of Pakistani children with and without acute flaccid paralysis (Victoria et al., 2009), in wild chimpanzees (Li et al., 2010) and in tissues of farm animals including cows, goats, bats and chickens (Ge et al., 2011;Li et al., 2010Li et al., , 2011. Unexpectedly, other cyclovirus species have also been detected in insects, namely dragonflies and cockroaches (Dayaram et al., 2013;Padilla-Rodriguez et al., 2013;Rosario et al., 2011). In 2013, a cyclovirus species (CyCV-CN) was found initially using viral metagenomics and then by PCR in 4 % of cerebrospinal fluid (CSF) specimens from Vietnamese children with unexplained central nervous system disorder, but not in CSF from patients with non-neurological problems, as well as in 4.2 % of faeces from healthy Vietnamese children (Tan et al., 2013). CyCV-CN DNA was also detected in a throat swab (Tan et al., 2013). In this study, 58 % of faecal specimens from pigs and poultry in Vietnam were also positive for the same cyclovirus, suggesting possible sources of human infection (Tan et al., 2013). A related cyclovirus was also detected in 10 % of CSF samples and 15 % of serum samples from adult patients with paraplegia (leg paralysis) from Malawi (Smits et al., 2013). Nasopharyngeal aspirates (NPAs) from Chilean children less than 2 years old with acute lower respiratory infections were tested for respiratory syncytial virus (RSV), adenovirus, parainfluenza virus 1-3 and influenza A and B viruses by indirect immunofluorescence assays and virus isolation (Avendaño et al., 2003). From 1998 to 2000, a mean of 29 % of acute lower respiratory infections samples were positive for RSV (Avendaño et al., 2003). To initiate the characterization of the viruses in non-reactive NPA samples, viral particles were enriched by filtration, and unprotected DNA and RNA were digested using a combination of nuclease enzymes (Victoria et al., 2009). The remaining nucleic acids were then extracted using a MagMAX Viral RNA Iso...

Diagnosis of pneumonia caused by Mycoplasma pneumoniae in adults is hampered by a lack of rapid and standardized tests for detection. This prospective study was conducted to compare the diagnostic values of an indirect immunofluorescence assay and a 16S rRNA gene PCR for the diagnosis of M. pneumoniae pneumonia in adults. From February 2005 to January 2008, 357 patients (53.8 % males, median age 63 years, range 18-94) admitted for community-acquired pneumonia (CAP) to two hospitals in Santiago, Chile, were enrolled in the study. Thirty-two patients (9.0 %) met the criteria of current or recent M. pneumoniae infection, and laboratory diagnosis was definitive in 26 cases (81.2 %) and presumptive in six cases (18.8 %). Among the 32 M. pneumoniae infections, the PCR assay was positive in 23 (71.9 %) and the serology in 27 (84.4 %) of the cases. IgM was positive in acute-phase serum specimens in 13 cases (40.6 %) of M. pneumoniae infections. Using serology as the gold standard, the sensitivity, specificity, and positive and negative predictive values of the PCR were 66.7, 98.5, 78.3 and 97.3 %, respectively, whereas the global agreement of the methods was 343/357 (96.1 %). The frequency of M. pneumoniae CAP cases declined significantly during the second year of study, suggesting the end of an epidemic period. In conclusion, although good global agreement was found between PCR and serology, the lower sensitivity of the PCR leads us to recommend the use of both procedures in parallel to confirm M. pneumoniae in CAP in adults. INTRODUCTIONCommunity-acquired pneumonia (CAP) is a relevant worldwide cause of morbidity and mortality. In spite of technological advances in microbial diagnosis, the aetiology usually remains uncertain and the therapy is empirical, based on the clinical and epidemiological features (Niederman et al., 1993;Fine et al., 1997). Mycoplasma pneumoniae is a common cause of CAP, mainly in children and young adults (Foy, 1993;Waites & Talkington, 2004). During epidemic periods, it also accounts for a significant proportion of acute respiratory tract infections in all age groups (Rastawicki et al., 1998;Layani-Milon et al., 1999). Furthermore, around 25 % of people infected with M. pneumoniae may experience extrapulmonary complications (Waites & Talkington, 2004). M. pneumoniae infections cannot be distinguished clinically from infections caused by viral or other bacterial agents (Foy, 1993;Waites & Talkington, 2004). Thus a rapid and accurate laboratory diagnosis is relevant for an effective therapy and for limiting the spread of infection in the community. The diagnosis of M. pneumoniae infection is currently based principally on serology. The detection of IgM provides an early and sensitive diagnosis in children (Waris et al., 1998;Petitjean et al., 2002). However, several studies have shown that adults fail to respond with IgM, probably as a result of re-infections (Sillis, 1990;Uldum et al., 1992;Jacobs, 1993). As IgG during the acute infection may represent persistent antibodies from past infection...

In very young infants, RSV cause more severe disease than HRV. Co-infection does not increase the severity of illness. NA1 RSV genotype was associated with major frequency of hospitalization, severe respiratory disease and higher viral load.