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Frontiers in Cellular and Infection... 2018is a Gram-negative pathogen that has a large accessory genome of plasmids and chromosomal gene loci. This accessory genome divides strains into opportunistic,... (Review)
Review
is a Gram-negative pathogen that has a large accessory genome of plasmids and chromosomal gene loci. This accessory genome divides strains into opportunistic, hypervirulent, and multidrug-resistant groups and separates from two closely related species, and . Some strains of act as opportunistic pathogens, infecting critically ill and immunocompromised patients. These are a common cause of health-care associated infections including pneumonia, urinary tract infections (UTIs), and bloodstream infections. and are often clinically indistinguishable from opportunistic . Other strains of are hypervirulent, infecting healthy people in community settings and causing severe infections including pyogenic liver abscess, endophthalmitis, and meningitis. A third group of encode carbapenemases, making them highly antibiotic-resistant. These strains act as opportunists but are exceedingly difficult to treat. All of these groups of and related species can colonize the gastrointestinal tract, and the accessory genome may determine if a colonizing strain remains asymptomatic or progresses to cause disease. This review will explore the associations between colonization and infection with opportunistic, antibiotic-resistant, and hypervirulent strains and the role of the accessory genome in distinguishing these groups and related species. As infections become progressively more difficult to treat in the face of antibiotic resistance and hypervirulent strains, an increased understanding of the epidemiology and pathogenesis of these bacteria is vital.
Topics: Anti-Bacterial Agents; Community-Acquired Infections; Cross Infection; Drug Resistance, Bacterial; Genes, Bacterial; Genome, Bacterial; Humans; Klebsiella Infections; Klebsiella pneumoniae; Mucous Membrane; Opportunistic Infections; Virulence
PubMed: 29404282
DOI: 10.3389/fcimb.2018.00004 -
Clinical Microbiology Reviews Jan 2012Stenotrophomonas maltophilia is an emerging multidrug-resistant global opportunistic pathogen. The increasing incidence of nosocomial and community-acquired S.... (Review)
Review
Stenotrophomonas maltophilia is an emerging multidrug-resistant global opportunistic pathogen. The increasing incidence of nosocomial and community-acquired S. maltophilia infections is of particular concern for immunocompromised individuals, as this bacterial pathogen is associated with a significant fatality/case ratio. S. maltophilia is an environmental bacterium found in aqueous habitats, including plant rhizospheres, animals, foods, and water sources. Infections of S. maltophilia can occur in a range of organs and tissues; the organism is commonly found in respiratory tract infections. This review summarizes the current literature and presents S. maltophilia as an organism with various molecular mechanisms used for colonization and infection. S. maltophilia can be recovered from polymicrobial infections, most notably from the respiratory tract of cystic fibrosis patients, as a cocolonizer with Pseudomonas aeruginosa. Recent evidence of cell-cell communication between these pathogens has implications for the development of novel pharmacological therapies. Animal models of S. maltophilia infection have provided useful information about the type of host immune response induced by this opportunistic pathogen. Current and emerging treatments for patients infected with S. maltophilia are discussed.
Topics: Drug Resistance, Multiple, Bacterial; Global Health; Gram-Negative Bacterial Infections; Humans; Opportunistic Infections; Pandemics; Stenotrophomonas maltophilia
PubMed: 22232370
DOI: 10.1128/CMR.00019-11 -
Handbook of Clinical Neurology 2013Toxoplasma gondii, an Apicomplexan, is a pathogic protozoan that can infect the central nervous system. Infection during pregnancy can result in a congenial infection...
Toxoplasma gondii, an Apicomplexan, is a pathogic protozoan that can infect the central nervous system. Infection during pregnancy can result in a congenial infection with severe neurological sequelae. In immunocompromised individuals reactivation of latent neurological foci can result in encephalitis. Immunocompetent individuals infected with T. gondii are typically asymptomatic and maintain this infection for life. However, recent studies suggest that these asymptomatic infections may have effects on behavior and other physiological processes. Toxoplasma gondii infects approximately one-third of the world population, making it one of the most successful parasitic organisms. Cats and other felidae serve as the definite host producing oocysts, an environmentally resistant life cycle stage found in cat feces, which can transmit the infection when ingested orally. A wide variety of warm-blooded animals, including humans, can serve as the intermediate host in which tissue cysts (containing bradyzoites) develop. Transmission also occurs due to ingestion of the tissue cysts. There are three predominant clonal lineages, termed Types I, II and III, and an association with higher pathogenicity with the Type I strains in humans has emerged. This chapter presents a review of the biology of this infection including the life cycle, transmission, epidemiology, parasite strains, and the host immune response. The major clinical outcomes of congenital infection, chorioretinitis and encephalitis, and the possible association of infection of toxoplasmosis with neuropsychiatric disorders such as schizophrenia, are reviewed.
Topics: Animals; Central Nervous System Diseases; Humans; Toxoplasma; Toxoplasmosis
PubMed: 23829904
DOI: 10.1016/B978-0-444-53490-3.00008-X -
Clinical Microbiology Reviews Jan 2019The ability of pathogenic bacteria to affect higher organisms and cause disease is one of the most dramatic properties of microorganisms. Some pathogens can establish... (Review)
Review
The ability of pathogenic bacteria to affect higher organisms and cause disease is one of the most dramatic properties of microorganisms. Some pathogens can establish transient colonization only, but others are capable of infecting their host for many years or even for a lifetime. Long-term infection is called persistence, and this phenotype is fundamental for the biology of important human pathogens, including , , and Both typhoidal and nontyphoidal serovars of the species can cause persistent infection in humans; however, as these two groups cause clinically distinct diseases, the characteristics of their persistent infections in humans differ significantly. Here, following a general summary of pathogenicity, host specificity, epidemiology, and laboratory diagnosis, I review the current knowledge about persistence and discuss the relevant epidemiology of persistence (including carrier rate, duration of shedding, and host and pathogen risk factors), the host response to persistence, genes involved in this lifestyle, as well as genetic and phenotypic changes acquired during prolonged infection within the host. Additionally, I highlight differences between the persistence of typhoidal and nontyphoidal strains in humans and summarize the current gaps and limitations in our understanding, diagnosis, and curing of persistent infections.
Topics: Carrier State; Humans; Risk Factors; Salmonella Infections; Salmonella enterica; Serogroup
PubMed: 30487167
DOI: 10.1128/CMR.00088-18 -
Clinical Microbiology Reviews Jan 2017Coxiella burnetii is the agent of Q fever, or "query fever," a zoonosis first described in Australia in 1937. Since this first description, knowledge about this pathogen... (Review)
Review
Coxiella burnetii is the agent of Q fever, or "query fever," a zoonosis first described in Australia in 1937. Since this first description, knowledge about this pathogen and its associated infections has increased dramatically. We review here all the progress made over the last 20 years on this topic. C. burnetii is classically a strict intracellular, Gram-negative bacterium. However, a major step in the characterization of this pathogen was achieved by the establishment of its axenic culture. C. burnetii infects a wide range of animals, from arthropods to humans. The genetic determinants of virulence are now better known, thanks to the achievement of determining the genome sequences of several strains of this species and comparative genomic analyses. Q fever can be found worldwide, but the epidemiological features of this disease vary according to the geographic area considered, including situations where it is endemic or hyperendemic, and the occurrence of large epidemic outbreaks. In recent years, a major breakthrough in the understanding of the natural history of human infection with C. burnetii was the breaking of the old dichotomy between "acute" and "chronic" Q fever. The clinical presentation of C. burnetii infection depends on both the virulence of the infecting C. burnetii strain and specific risks factors in the infected patient. Moreover, no persistent infection can exist without a focus of infection. This paradigm change should allow better diagnosis and management of primary infection and long-term complications in patients with C. burnetii infection.
Topics: Animals; Coxiella burnetii; Genome, Bacterial; Humans; Q Fever; Virulence; Zoonoses
PubMed: 27856520
DOI: 10.1128/CMR.00045-16 -
Clinical Microbiology and Infection :... Jan 2016Aerococci have often been misidentified as streptococci in microbiology laboratories, leading to an underestimation of these bacteria as causes of human infections. An... (Review)
Review
Aerococci have often been misidentified as streptococci in microbiology laboratories, leading to an underestimation of these bacteria as causes of human infections. An increased awareness of aerococci and the introduction of matrix-assisted laser desorption ionization time-of-flight mass spectrometry, has led to an increased isolation of Aerococcus urinae and Aerococcus sanguinicola from human urine and blood. The two species are found in human urine and can cause urinary tract infections (UTI). Aerococcus urinae can, in older males with underlying urinary tract conditions, cause invasive infections such as urosepsis or infective endocarditis. The prognosis of invasive aerococcal infections appears to be relatively favourable despite the old age of patients and their many comorbidities. Though clinical breakpoints are still not in place, aerococci seem to be sensitive to penicillins, carbapenems and vancomycin. There is synergy between penicillin and aminoglycosides against some A. urinae isolates and this combination is often used in aerococcal infective endocarditis. The treatment of complicated aerococcal UTI is not obvious as many isolates are resistant to fluoroquinolones. In addition, A. urinae is resistant to sulphamethoxazole, and there are methodological problems in the determination of trimethoprim sensitivity. In complicated UTI, ampicillin is probably a safe treatment option, whereas nitrofurantoin is probably effective in uncomplicated UTI. Treatment studies in aerococcal infections are needed as is a better understanding of the natural niches for aerococci and the pathogenesis and clinical course of aerococcal infections.
Topics: Aerococcus; Anti-Bacterial Agents; Blood; Endocarditis, Bacterial; Gram-Positive Bacterial Infections; Humans; Microbial Sensitivity Tests; Sepsis; Urinary Tract Infections; Urine
PubMed: 26454061
DOI: 10.1016/j.cmi.2015.09.026 -
Microbiology Spectrum Oct 2018Fulminant staphylococcal infection indicates an explosive, intense, and severe infection occurring in a patient whose previous condition and antecedent would never have... (Review)
Review
Fulminant staphylococcal infection indicates an explosive, intense, and severe infection occurring in a patient whose previous condition and antecedent would never have caused any anticipation of life-threatening development. This includes necrotizing pneumonia, necrotizing fasciitis, and to some extent toxic shock syndrome and infective endocarditis. In the three former diseases, toxin production plays a major role whereas in the latter (fulminant presentation of infective endocarditis), association with any particular toxinic profile has never been demonstrated. This article reviews the clinical, pathophysiological, and therapeutic aspects of these diseases.
Topics: Bacteremia; Endocarditis; Fasciitis, Necrotizing; Humans; Pneumonia, Necrotizing; Shock, Septic; Staphylococcal Infections; Staphylococcus aureus
PubMed: 30291703
DOI: 10.1128/microbiolspec.GPP3-0036-2018 -
Proceedings of the National Academy of... Jun 2018Novel reassortant avian influenza H7N9 virus and pandemic 2009 H1N1 (H1N1pdm) virus cause human infections, while avian H7N2 and swine H1N1 virus mainly infect birds and...
Novel reassortant avian influenza H7N9 virus and pandemic 2009 H1N1 (H1N1pdm) virus cause human infections, while avian H7N2 and swine H1N1 virus mainly infect birds and pigs, respectively. There is no robust in vitro model for assessing the infectivity of emerging viruses in humans. Based on a recently established method, we generated long-term expanding 3D human airway organoids which accommodate four types of airway epithelial cells: ciliated, goblet, club, and basal cells. We report differentiation conditions which increase ciliated cell numbers to a nearly physiological level with synchronously beating cilia readily discernible in every organoid. In addition, the differentiation conditions induce elevated levels of serine proteases, which are essential for productive infection of human influenza viruses and low-pathogenic avian influenza viruses. We also established improved 2D monolayer culture conditions for the differentiated airway organoids. To demonstrate the ability of differentiated airway organoids to identify human-infective virus, 3D and 2D differentiated airway organoids are applied to evaluate two pairs of viruses with known distinct infectivity in humans, H7N9/Ah versus H7N2 and H1N1pdm versus an H1N1 strain isolated from swine (H1N1sw). The human-infective H7N9/Ah virus replicated more robustly than the poorly human-infective H7N2 virus; the highly human-infective H1N1pdm virus replicated to a higher titer than the counterpart H1N1sw. Collectively, we developed differentiated human airway organoids which can morphologically and functionally simulate human airway epithelium. These differentiated airway organoids can be applied for rapid assessment of the infectivity of emerging respiratory viruses to human.
Topics: Humans; Influenza A Virus, H1N1 Subtype; Influenza A Virus, H7N2 Subtype; Influenza, Human; Organoids; Respiratory System
PubMed: 29891677
DOI: 10.1073/pnas.1806308115 -
Infection Apr 2021SARS-CoV-2 is a recently emerged ß-coronavirus. Here we present the current knowledge on its epidemiologic features. (Review)
Review
PURPOSE
SARS-CoV-2 is a recently emerged ß-coronavirus. Here we present the current knowledge on its epidemiologic features.
METHODS
Non-systematic review.
RESULTS
SARS-CoV-2 replicates in the upper and lower respiratory tract. It is mainly transmitted by droplets and aerosols from asymptomatic and symptomatic infected subjects. The consensus estimate for the basis reproduction number (R) is between 2 and 3, and the median incubation period is 5.7 (range 2-14) days. Similar to SARS and MERS, superspreading events have been reported, the dispersion parameter (kappa) is estimated at 0.1. Most infections are uncomplicated, and 5-10% of patients are hospitalized, mainly due to pneumonia with severe inflammation. Complications are respiratory and multiorgan failure; risk factors for complicated disease are higher age, hypertension, diabetes, chronic cardiovascular, chronic pulmonary disease and immunodeficiency. Nosocomial and infections in medical personnel have been reported. Drastic reductions of social contacts have been implemented in many countries with outbreaks of SARS-CoV-2, leading to rapid reductions. Most interventions have used bundles, but which of the measures have been more or less effective is still unknown. The current estimate for the infection's fatality rate is 0.5-1%. Using current models of age-dependent infection fatality rates, upper and lower limits for the attack rate in Germany can be estimated between 0.4 and 1.6%, lower than in most European countries.
CONCLUSIONS
Despite a rapid worldwide spread, attack rates have been low in most regions, demonstrating the efficacy of control measures.
Topics: Age Distribution; Basic Reproduction Number; COVID-19; Cross Infection; Humans; Incidence; Infectious Disease Incubation Period; Mortality; Risk Factors; SARS-CoV-2
PubMed: 33034020
DOI: 10.1007/s15010-020-01531-3 -
Microbiology and Immunology Jun 2022Secondary bacterial infection following influenza type A virus (IAV) infection is a major cause of morbidity and mortality during influenza epidemics. Streptococcus... (Review)
Review
Secondary bacterial infection following influenza type A virus (IAV) infection is a major cause of morbidity and mortality during influenza epidemics. Streptococcus pneumoniae has been identified as a predominant pathogen in secondary pneumonia cases that develop following influenza. Although IAV has been shown to enhance susceptibility to the secondary bacterial infection, the underlying mechanism of the viral-bacterial synergy leading to disease progression is complex and remains elusive. In this review, cooperative interactions of viruses and streptococci during co- or secondary infection with IAV are described. IAV infects the upper respiratory tract, therefore, streptococci that inhabit or infect the respiratory tract are of special interest. As many excellent reviews on the co-infection of IAV and S. pneumoniae have already been published, this review is intended to describe the unique interactions between other streptococci and IAV. Both streptococcal and IAV infections modulate the host epithelial barrier of the respiratory tract in various ways. IAV infection directly disrupts epithelial barriers, though at the same time the virus modifies the properties of infected cells to enhance streptococcal adherence and invasion. Mitis group streptococci produce neuraminidases, which promote IAV infection in a unique manner. The studies reviewed here have revealed intriguing mechanisms underlying secondary streptococcal infection following influenza.
Topics: Coinfection; Humans; Influenza A virus; Influenza, Human; Orthomyxoviridae Infections; Streptococcal Infections; Streptococcus pneumoniae
PubMed: 35088451
DOI: 10.1111/1348-0421.12965