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Pathogens, Volume 5, Issue 2 (June 2016)

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Open AccessReview
Legionella pneumophila Carbonic Anhydrases: Underexplored Antibacterial Drug Targets
Pathogens 2016, 5(2), 44; https://doi.org/10.3390/pathogens5020044 - 16 Jun 2016
Cited by 28 | Viewed by 2006
Abstract
Carbonic anhydrases (CAs, EC 4.2.1.1) are metalloenzymes which catalyze the hydration of carbon dioxide to bicarbonate and protons. Many pathogenic bacteria encode such enzymes belonging to the α-, β-, and/or γ-CA families. In the last decade, enzymes from some of these pathogens, including [...] Read more.
Carbonic anhydrases (CAs, EC 4.2.1.1) are metalloenzymes which catalyze the hydration of carbon dioxide to bicarbonate and protons. Many pathogenic bacteria encode such enzymes belonging to the α-, β-, and/or γ-CA families. In the last decade, enzymes from some of these pathogens, including Legionella pneumophila, have been cloned and characterized in detail. These enzymes were shown to be efficient catalysts for CO2 hydration, with kcat values in the range of (3.4–8.3) × 105 s−1 and kcat/KM values of (4.7–8.5) × 107 M−1·s−1. In vitro inhibition studies with various classes of inhibitors, such as anions, sulfonamides and sulfamates, were also reported for the two β-CAs from this pathogen, LpCA1 and LpCA2. Inorganic anions were millimolar inhibitors, whereas diethyldithiocarbamate, sulfamate, sulfamide, phenylboronic acid, and phenylarsonic acid were micromolar ones. The best LpCA1 inhibitors were aminobenzolamide and structurally similar sulfonylated aromatic sulfonamides, as well as acetazolamide and ethoxzolamide (KIs in the range of 40.3–90.5 nM). The best LpCA2 inhibitors belonged to the same class of sulfonylated sulfonamides, together with acetazolamide, methazolamide, and dichlorophenamide (KIs in the range of 25.2–88.5 nM). Considering such preliminary results, the two bacterial CAs from this pathogen represent promising yet underexplored targets for obtaining antibacterials devoid of the resistance problems common to most of the clinically used antibiotics, but further studies are needed to validate them in vivo as drug targets. Full article
(This article belongs to the Special Issue Pathogen Legionella pneumophila)
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Open AccessCommunication
Astrocytes Enhance Streptococcus suis-Glial Cell Interaction in Primary Astrocyte-Microglial Cell Co-Cultures
Pathogens 2016, 5(2), 43; https://doi.org/10.3390/pathogens5020043 - 13 Jun 2016
Cited by 2 | Viewed by 1960
Abstract
Streptococcus (S.) suis infections are the most common cause of meningitis in pigs. Moreover, S. suis is a zoonotic pathogen, which can lead to meningitis in humans, mainly in adults. We assume that glial cells may play a crucial role in [...] Read more.
Streptococcus (S.) suis infections are the most common cause of meningitis in pigs. Moreover, S. suis is a zoonotic pathogen, which can lead to meningitis in humans, mainly in adults. We assume that glial cells may play a crucial role in host-pathogen interactions during S. suis infection of the central nervous system. Glial cells are considered to possess important functions during inflammation and injury of the brain in bacterial meningitis. In the present study, we established primary astrocyte-microglial cell co-cultures to investigate interactions of S. suis with glial cells. For this purpose, microglial cells and astrocytes were isolated from new-born mouse brains and characterized by flow cytometry, followed by the establishment of astrocyte and microglial cell mono-cultures as well as astrocyte-microglial cell co-cultures. In addition, we prepared microglial cell mono-cultures co-incubated with uninfected astrocyte mono-culture supernatants and astrocyte mono-cultures co-incubated with uninfected microglial cell mono-culture supernatants. After infection of the different cell cultures with S. suis, bacteria-cell association was mainly observed with microglial cells and most prominently with a non-encapsulated mutant of S. suis. A time-dependent induction of NO release was found only in the co-cultures and after co-incubation of microglial cells with uninfected supernatants of astrocyte mono-cultures mainly after infection with the capsular mutant. Only moderate cytotoxic effects were found in co-cultured glial cells after infection with S. suis. Taken together, astrocytes and astrocyte supernatants increased interaction of microglial cells with S. suis. Astrocyte-microglial cell co-cultures are suitable to study S. suis infections and bacteria-cell association as well as NO release by microglial cells was enhanced in the presence of astrocytes. Full article
(This article belongs to the Special Issue Streptococcus suis)
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Open AccessReview
The Use of a Recombinant Canarypox-Based Equine Influenza Vaccine during the 2007 Australian Outbreak: A Systematic Review and Summary
Pathogens 2016, 5(2), 42; https://doi.org/10.3390/pathogens5020042 - 10 Jun 2016
Cited by 11 | Viewed by 2513
Abstract
In 2007, Australia experienced the most extensive equine influenza outbreak observed in recent years. Extraordinary measures were rapidly implemented in order to control and prevent the spread of this highly contagious disease. The control strategy involved stringent movement restriction and disease surveillance, seconded [...] Read more.
In 2007, Australia experienced the most extensive equine influenza outbreak observed in recent years. Extraordinary measures were rapidly implemented in order to control and prevent the spread of this highly contagious disease. The control strategy involved stringent movement restriction and disease surveillance, seconded by emergency post-outbreak vaccination strategies. Sixteen months after the first case and 12 months following the last reported case, Australia regained its equine influenza-free OIE status. This systematic review reports and summarises information relating to the implementation of emergency vaccination during the 2007 Australian equine influenza outbreak, including the choice of vaccine and implementation strategies. Full article
(This article belongs to the Special Issue Equine Influenza)
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Open AccessArticle
Rickettsia Detected in the Reptile Tick Bothriocroton hydrosauri from the Lizard Tiliqua rugosa in South Australia
Pathogens 2016, 5(2), 41; https://doi.org/10.3390/pathogens5020041 - 08 Jun 2016
Cited by 7 | Viewed by 1672
Abstract
Rickettsiosis is a potentially fatal tick borne disease. It is caused by the obligate intracellular bacteria Rickettsia, which is transferred to humans through salivary excretions of ticks during the biting process. Globally, the incidence of tick-borne diseases is increasing; as such, there [...] Read more.
Rickettsiosis is a potentially fatal tick borne disease. It is caused by the obligate intracellular bacteria Rickettsia, which is transferred to humans through salivary excretions of ticks during the biting process. Globally, the incidence of tick-borne diseases is increasing; as such, there is a need for a greater understanding of tick–host interactions to create more informed risk management strategies. Flinders Island spotted fever rickettsioses has been identified throughout Australia (Tasmania, South Australia, Queensland and Torres Strait Islands) with possible identifications in Thailand, Sri Lanka and Italy. Flinders Island spotted fever is thought to be spread through tick bites and the reptile tick Bothriocroton hydrosauri has been implicated as a vector in this transmission. This study used qPCR to assay Bothriocroton hydrosauri ticks collected from Tiliqua rugosa (sleepy lizard) hosts on mainland South Australia near where spotted fever cases have been identified. We report that, although we discovered Rickettsia in all tick samples, it was not Rickettsia honei. This study is the first to use PCR to positively identify Rickettsia from South Australian Bothriocroton hydrosauri ticks collected from Tiliqua rugosa (sleepy lizard) hosts. These findings suggest that B. hydrosauri may be a vector of multiple Rickettsia spp. Also as all 41 tested B. hydrosauri ticks were positive for Rickettsia this indicates an extremely high prevalence within the studied area in South Australia. Full article
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Open AccessArticle
Comparison of Surface Proteomes of Adherence Variants of Listeria Monocytogenes Using LC-MS/MS for Identification of Potential Surface Adhesins
Pathogens 2016, 5(2), 40; https://doi.org/10.3390/pathogens5020040 - 17 May 2016
Cited by 4 | Viewed by 2372
Abstract
The ability of Listeria monocytogenes to adhere and form biofilms leads to persistence in food processing plants and food-associated listeriosis. The role of specific surface proteins as adhesins to attach Listeria cells to various contact surfaces has not been well characterized to date. [...] Read more.
The ability of Listeria monocytogenes to adhere and form biofilms leads to persistence in food processing plants and food-associated listeriosis. The role of specific surface proteins as adhesins to attach Listeria cells to various contact surfaces has not been well characterized to date. In prior research comparing different methods for surface protein extraction, the Ghost urea method revealed cleaner protein content as verified by the least cytoplasmic protein detected in surface extracts using LC-MS/MS. The same technique was utilized to extract and detect surface proteins among two surface-adherent phenotypic strains of L. monocytogenes (i.e., strongly and weakly adherent). Of 640 total proteins detected among planktonic and sessile cells, 21 protein members were exclusively detected in the sessile cells. Relative LC-MS/MS detection and quantification of surface-extracted proteins from the planktonic weakly adherent (CW35) and strongly adherent strains (99-38) were examined by protein mass normalization of proteins. We found that L. monocytogenes 99-38 exhibited a total of 22 surface proteins that were over-expressed: 11 proteins were detected in surface extracts of both sessile and planktonic 99-38 that were ≥5-fold over-expressed while another 11 proteins were detected only in planktonic 99-38 cells that were ≥10-fold over-expressed. Our results suggest that these protein members are worthy of further investigation for their involvement as surface adhesins. Full article
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Open AccessReview
A Cellular GWAS Approach to Define Human Variation in Cellular Pathways Important to Inflammation
Pathogens 2016, 5(2), 39; https://doi.org/10.3390/pathogens5020039 - 26 Apr 2016
Cited by 4 | Viewed by 1816
Abstract
An understanding of common human diversity in innate immune pathways should be beneficial in understanding autoimmune diseases, susceptibility to infection, and choices of anti-inflammatory treatment. Such understanding could also result in definition of currently unknown components of human inflammation pathways. A cellular genome-wide [...] Read more.
An understanding of common human diversity in innate immune pathways should be beneficial in understanding autoimmune diseases, susceptibility to infection, and choices of anti-inflammatory treatment. Such understanding could also result in definition of currently unknown components of human inflammation pathways. A cellular genome-wide association studies (GWAS) platform, termed Hi-HOST (High-throughput human in vitro susceptibility testing), was developed to assay in vitro cellular phenotypes of infection in genotyped lymphoblastoid cells from genetically diverse human populations. Hi-HOST allows for measurement of multiple host and pathogen parameters of infection/inflammation including: bacterial invasion and intracellular replication, host cell death, and cytokine production. Hi-HOST has been used to successfully define a significant portion of the heritable human diversity in inflammatory cell death in response to Salmonella typhimurium. It also led to the discovery of genetic variants important to protection against systemic inflammatory response syndrome (SIRS) and protection against death and bacteremia in individuals with SIRS. Our laboratory is currently using this platform to define human diversity in autophagy and the NLPR3 inflammasome pathways, and to define new components that can impact the expression of phenotypes related to these pathways. Full article
(This article belongs to the Special Issue Molecular Aspects of Urinary Tract Infection)
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Open AccessConference Report
The Paradigm Shift to Non-Treatment of Asymptomatic Bacteriuria
Pathogens 2016, 5(2), 38; https://doi.org/10.3390/pathogens5020038 - 19 Apr 2016
Cited by 21 | Viewed by 2691
Abstract
Asymptomatic bacteriuria, also called asymptomatic urinary infection, is a common finding in healthy women, and in women and men with abnormalities of the genitourinary tract. The characterization and introduction of the quantitative urine culture in the 1950s first allowed the reliable recognition of [...] Read more.
Asymptomatic bacteriuria, also called asymptomatic urinary infection, is a common finding in healthy women, and in women and men with abnormalities of the genitourinary tract. The characterization and introduction of the quantitative urine culture in the 1950s first allowed the reliable recognition of asymptomatic bacteriuria. The observations that a substantial proportion of patients with chronic pyelonephritis at autopsy had no history of symptomatic urinary infection, and the high frequency of pyelonephritis observed in pregnant women with untreated asymptomatic bacteriuria, supported a conclusion that asymptomatic bacteriuria was harmful. Subsequent screening and long term follow-up programs for asymptomatic bacteriuria in schoolgirls and women reported an increased frequency of symptomatic urinary tract infection for subjects with asymptomatic bacteriuria, but no increased morbidity from renal failure or hypertension, or increased mortality. Treatment of asymptomatic bacteriuria did not decrease the frequency of symptomatic infection. Prospective, randomized, comparative trials enrolling premenopausal women, children, elderly populations, patients with long term catheters, and diabetic patients consistently report no benefits with antimicrobial treatment of asymptomatic bacteriuria, and some evidence of harm. Several studies have also reported that antimicrobial treatment of asymptomatic bacteriuria increases the short term risk of pyelonephritis. Current investigations are exploring the potential therapeutic intervention of establishing asymptomatic bacteriuria with an avirulent Escherichia coli strain to prevent symptomatic urinary tract infection for selected patients. Full article
(This article belongs to the Special Issue Molecular Aspects of Urinary Tract Infection)
Open AccessArticle
Impact of Sub-Inhibitory Concentrations of Amoxicillin on Streptococcus suis Capsule Gene Expression and Inflammatory Potential
Pathogens 2016, 5(2), 37; https://doi.org/10.3390/pathogens5020037 - 19 Apr 2016
Cited by 7 | Viewed by 1994
Abstract
Streptococcus suis is an important swine pathogen and emerging zoonotic agent worldwide causing meningitis, endocarditis, arthritis and septicemia. Among the 29 serotypes identified to date, serotype 2 is mostly isolated from diseased pigs. Although several virulence mechanisms have been characterized in S. suis [...] Read more.
Streptococcus suis is an important swine pathogen and emerging zoonotic agent worldwide causing meningitis, endocarditis, arthritis and septicemia. Among the 29 serotypes identified to date, serotype 2 is mostly isolated from diseased pigs. Although several virulence mechanisms have been characterized in S. suis, the pathogenesis of S. suis infections remains only partially understood. This study focuses on the response of S. suis P1/7 to sub-inhibitory concentrations of amoxicillin. First, capsule expression was monitored by qRT-PCR when S. suis was cultivated in the presence of amoxicillin. Then, the pro-inflammatory potential of S. suis P1/7 culture supernatants or whole cells conditioned with amoxicillin was evaluated by monitoring the activation of the NF-κB pathway in monocytes and quantifying pro-inflammatory cytokines secreted by macrophages. It was found that amoxicillin decreased capsule expression in S. suis. Moreover, conditioning the bacterium with sub-inhibitory concentrations of amoxicillin caused an increased activation of the NF-κB pathway in monocytes following exposure to bacterial culture supernatants and to a lesser extent to whole bacterial cells. This was associated with an increased secretion of pro-inflammatory cytokines (CXCL8, IL-6, IL-1β) by macrophages. This study identified a new mechanism by which S. suis may increase its inflammatory potential in the presence of sub-inhibitory concentrations of amoxicillin, a cell wall-active antibiotic, thus challenging its use for preventive treatments or as growth factor. Full article
(This article belongs to the Special Issue Streptococcus suis)
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Open AccessReview
Non-Antibiotic Prophylaxis for Urinary Tract Infections
Pathogens 2016, 5(2), 36; https://doi.org/10.3390/pathogens5020036 - 16 Apr 2016
Cited by 25 | Viewed by 4963
Abstract
Increasing antimicrobial resistance has stimulated interest in non-antibiotic prophylaxis of recurrent urinary tract infections (UTIs). Well-known steps in the pathogenesis of UTIs are urogenital colonization and adherence of uropathogens to uroepithelial cell receptors. To prevent colonization in postmenopausal women, vaginal, but not oral, [...] Read more.
Increasing antimicrobial resistance has stimulated interest in non-antibiotic prophylaxis of recurrent urinary tract infections (UTIs). Well-known steps in the pathogenesis of UTIs are urogenital colonization and adherence of uropathogens to uroepithelial cell receptors. To prevent colonization in postmenopausal women, vaginal, but not oral, estrogens have been shown to restore the vagina lactobacilli flora, reduce vaginal colonization with Enterobacteriaceae, and reduce the number of UTIs compared to placebo. Different lactobacilli strains show different results in the prevention of recurrent UTIs. Intravaginal suppositories with Lactobacillus crispatus in premenopausal women and oral capsules with Lactobacillus rhamnosus GR-1 and Lactobacillus reuteri RC-14 in postmenopausal women are promising. Ascorbic acid (vitamin C) cannot be recommended for the prevention of UTIs. Cranberries are thought to contain proanthocyanidins that can inhibit adherence of P-fimbriated E. coli to the uroepithelial cell receptors. Cranberry products decreased UTI recurrences about 30%–40% in premenopausal women with recurrent UTIs, but are less effective than low-dose antimicrobial prophylaxis. However, the optimal dose of cranberry product has still to be determined. Initially OM-89, a vaccine with 18 heat-killed E. coli extracts, seemed promising, but this was not confirmed in a recently randomized trial. Full article
(This article belongs to the Special Issue Molecular Aspects of Urinary Tract Infection)
Open AccessArticle
Combination of Heat Shock and Enhanced Thermal Regime to Control the Growth of a Persistent Legionella pneumophila Strain
Pathogens 2016, 5(2), 35; https://doi.org/10.3390/pathogens5020035 - 15 Apr 2016
Cited by 12 | Viewed by 2322
Abstract
Following nosocomial cases of Legionella pneumophila, the investigation of a hot water system revealed that 81.5% of sampled taps were positive for L. pneumophila, despite the presence of protective levels of copper in the water. A significant reduction of L. pneumophila [...] Read more.
Following nosocomial cases of Legionella pneumophila, the investigation of a hot water system revealed that 81.5% of sampled taps were positive for L. pneumophila, despite the presence of protective levels of copper in the water. A significant reduction of L. pneumophila counts was observed by culture after heat shock disinfection. The following corrective measures were implemented to control L. pneumophila: increasing the hot water temperature (55 to 60 °C), flushing taps weekly with hot water, removing excess lengths of piping and maintaining a water temperature of 55 °C throughout the system. A gradual reduction in L. pneumophila counts was observed using the culture method and qPCR in the 18 months after implementation of the corrective measures. However, low level contamination was retained in areas with hydraulic deficiencies, highlighting the importance of maintaining a good thermal regime at all points within the system to control the population of L. pneumophila. Full article
(This article belongs to the Special Issue Pathogen Legionella pneumophila)
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Open AccessReview
The Role of Autophagy-Related Proteins in Candida albicans Infections
Pathogens 2016, 5(2), 34; https://doi.org/10.3390/pathogens5020034 - 29 Mar 2016
Cited by 10 | Viewed by 2856
Abstract
Autophagy plays an important role in maintaining cell homeostasis by providing nutrients during periods of starvation and removing damaged organelles from the cytoplasm. A marker in the autophagic process is the reversible conjugation of LC3, a membrane scaffolding protein, to double membrane autophagosomes. [...] Read more.
Autophagy plays an important role in maintaining cell homeostasis by providing nutrients during periods of starvation and removing damaged organelles from the cytoplasm. A marker in the autophagic process is the reversible conjugation of LC3, a membrane scaffolding protein, to double membrane autophagosomes. Recently, a role for LC3 in the elimination of pathogenic bacteria and fungi, including Candida albicans (C. albicans), was demonstrated, but these organisms reside in single membrane phagosomes. This process is distinct from autophagy and is termed LC3-associated phagocytosis (LAP). This review will detail the hallmarks of LAP that distinguish it from classical autophagy and review the role of autophagy proteins in host response to C. albicans and other pathogenic fungi. Full article
(This article belongs to the Special Issue Candida Albicans Infections)
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