Concatenated ScaA and TSA56 Surface Antigen Sequences Reflect Genome-Scale Phylogeny of Orientia tsutsugamushi: An Analysis Including Two Genomes from Taiwan.

Orientia tsutsugamushi is an obligate intracellular bacterium associated with trombiculid mites and is the causative agent of scrub typhus, a life-threatening febrile disease. Strain typing of O. tsutsugamushi is based on its immunodominant surface antigen, 56-kDa type-specific antigen (TSA56). However, TSA56 gene sequence-based phylogenetic analysis is only partially congruent with core genome-based phylogenetic analysis. Thus, this study investigated whether concatenated surface antigen sequences, including surface cell antigen (Sca) proteins, can reflect the genome-scale phylogeny of O. tsutsugamushi. Complete genomes were obtained for two common O. tsutsugamushi strains in Taiwan, TW-1 and TW-22, and the core genome/proteome was identified for 11 O. tsutsugamushi strains. Phylogenetic analysis was performed using maximum likelihood (ML) and neighbor-joining (NJ) methods, and the congruence between trees was assessed using a quartet similarity measure. Phylogenetic analysis based on 691 concatenated core protein sequences produced identical tree topologies with ML and NJ methods. Among TSA56 and core Sca proteins (ScaA, ScaC, ScaD, and ScaE), TSA56 trees were most similar to the core protein tree, and ScaA trees were the least similar. However, concatenated ScaA and TSA56 sequences produced trees that were highly similar to the core protein tree, the NJ tree being more similar. Strain-level characterization of O. tsutsugamushi may be improved by coanalyzing ScaA and TSA56 sequences, which are also important targets for their combined immunogenicity.

Fungal Spore Richness and Abundance of Allergenic Taxa: Comparing a Portable Impactor and Passive Trap Indoors and Outdoors in an Urban Setting.

Fungal spores are common airborne allergens, and fungal richness has been implicated in allergic disease. Amplicon sequencing of environmental DNA from air samples is a promising method to estimate fungal spore richness with semi-quantification of hundreds of taxa and can be combined with quantitative PCR to derive abundance estimates. However, it remains unclear how the choice of air sampling method influences these estimates. This study compared active sampling with a portable impactor and passive sampling with a passive trap over different durations to estimate fungal spore richness and the abundance of allergenic taxa. Air sampling was conducted indoors and outdoors at 12 residences, including repeated measurements with a portable impactor and passive traps with 1-day and 7-day durations. ITS2 amplicon sequence data were transformed to spore equivalents estimated by quantitative PCR, repeated active samples were combined, and abundance-based rarefaction was performed to standardize sample coverage for estimation of genus-level richness and spore abundance. Rarefied fungal richness was similar between methods indoors but higher for passive traps with a 7-day duration outdoors. Rarefied abundance of allergenic genera was similar between methods but some genera had lower abundance for passive traps with a 1-day duration, which differed indoors and outdoors indicating stochasticity in the collection of spores on collocated samplers. This study found that similar estimates of fungal spore richness and abundance of allergenic taxa can be obtained using a portable impactor or a passive trap within one day and that increased passive sample duration provides limited additional information.

Rickettsia felis is an emerging human pathogen associated with cat fleas: A review of findings in Taiwan.

Rickettsia felis is an emerging rickettsial agent principally associated with cat fleas (Ctenocephalides felis), formerly discovered in 1990. Since then, clinical cases of R. felis infection have been identified globally by specific DNA sequences in patients with undifferentiated febrile illness, including in Taiwan, but such evidence is limited. R. felis rickettsiosis is self-limiting and easily treated with doxycycline, but its diagnosis remains a challenge. Environmental risk factors for R. felis rickettsiosis have yet to be clearly demonstrated, and its transmission biology is incompletely understood. Cat fleas are naturally infected with R. felis at varying rates, and vector competence in the transmission of R. felis has been demonstrated in animal models, including dogs, which may serve as reservoir hosts. In northern Taiwan, despite ∼20% of cat fleas infesting companion animals consistently found to be infected with R. felis, only a few cases of potential R. felis infection have been identified through a retrospective serological investigation, though without molecular confirmation. Ecological studies have identified divergent R. felis-like organisms in different arthropod hosts, but these strains appear to serve as nonpathogenic endosymbionts. Although its association with disease is limited, we believe cat flea-borne R. felis warrants increased recognition in an aging population due to immunosenescence and the proximity of companion animals to the elderly. Adopting a One Health approach involving collaboration and communication between clinicians, veterinarians, public health practitioners, and environmental scientists will improve our knowledge about this neglected pathogen and promote the prevention and control of vector-borne diseases.

Fungal Spore Richness in School Classrooms is Related to Surrounding Forest in a Season-Dependent Manner.

Airborne fungal spores are important aeroallergens that are remarkably diverse in terms of taxonomic richness. Indoor fungal richness is dominated by outdoor fungi and is geographically patterned, but the influence of natural landscape is unclear. We aimed to elucidate the relationship between indoor fungal spore richness and natural landscape by examining the amount of surrounding forest cover. Passive sampling of airborne fungal spores was conducted in 24 schools in Taiwan during hot and cool seasons, and amplicon sequencing was used to study fungal spore (genus) richness targeting the internal transcribed spacer 2 (ITS2) region. In total, 693 fungal genera were identified, 12 of which were ubiquitous. Despite overall similarity of fungal spore richness between seasons, Basidiomycota and Ascomycota richness increased during the hot and cool seasons, respectively. Fungal spore richness in schools had a strong positive correlation with the amount of surrounding forest cover during the cool season, but not during the hot season. Fungal assemblages in schools were more similar during the hot season due to the increased ubiquity of Agaricomycetes genera. These observations indicate dispersal limitation at the kilometer scale during the cool season and increased long-distance dispersal during the hot season. Several allergenic fungi were commonly identified in schools, including some previously overlooked by conventional methods, which may be targeted as sensitizing agents in future investigations into atopic conditions. More generally, the relative importance of fungal spore richness in the development, chronicity, and severity of atopic conditions in children requires investigation.

Seroepidemiological and molecular investigation of spotted fever group rickettsiae and Coxiella burnetii in Sao Tome Island: A One Health approach.

Spotted fever group rickettsiae (SFGR) and Coxiella burnetii are intracellular bacteria that cause potentially life-threatening tick-borne rickettsioses and Q fever respectively. Sao Tome and Principe (STP), small islands located in the Gulf of Guinea, recently experienced a dramatic reduction in the incidence of malaria owing to international collaborative efforts. However, unexplained febrile illnesses persist. A One Health approach was adopted to investigate exposure to SFGR and C. burnetii in humans and examine the diversity of these bacteria in ticks parasitizing domestic ruminants. A cross-sectional human serological study was conducted in Agua Grande district in Sao Tome Island from January to March 2016, and ticks were collected from farmed domestic ruminants in 2012 and 2016. In total, 240 individuals varying in age were randomly screened for exposure to SFGR and C. burnetii by indirect immunofluorescence assay. Twenty of 240 individuals (8.3%) were seropositive for SFGR (4 for Rickettsia africae and 16 for R. conorii) and 16 (6.7%) were seropositive for C. burnetii. Amblyomma astrion were collected exclusively in 2012, as were A. variegatum in 2016 and Rickettsia spp. were detected in 22/42 (52.4%) and 49/60 (81.7%) respectively. Sequence analysis of multiple gene targets from Rickettsia spp. detected in ticks suggests the presence of a single divergent R. africae strain (Sao Tome). While no ticks were found positive for C. burnetii, Coxiella-like endosymbionts were detected in nearly all ticks. This is the first study in STP to provide serological evidence in humans of SFGR and C. burnetii and additional molecular evidence in ticks for SFGR, which may be responsible for some of the unexplained febrile illnesses that persist despite the control of malaria. Future epidemiological studies are needed to confirm the occurrence and risk factors associated with SFG rickettsioses and Q fever in both humans and animals.

Hydra amphiphiles: Using three heads and one tail to influence aggregate formation and to kill pathogenic bacteria.

Hydra amphiphiles mimic the morphology of the mythical multi-headed creatures for which they are named. Likewise, when faced with a pathogenic bacterium, some hydra derivatives are as destructive as their fabled counterparts were to their adversaries. This report focuses on eight new tricephalic (triple-headed), single-tailed amphiphiles. Each amphiphile has a mesitylene (1,3,5-trimethylbenzene) core, two benzylic trimethylammonium groups and one dimethylalkylammonium group with a linear hydrophobe ranging from short (C8H17) to ultralong (C22H45). The logarithm of the critical aggregation concentration, log(CAC), decreases linearly with increasing tail length, but with a smaller dependence than that of ionic amphiphiles with fewer head groups. Tail length also affects antibacterial activity; amphiphiles with a linear 18 or 20 carbon atom hydrophobic chain are more effective at killing bacteria than those with shorter or longer chains. Comparison to a recently reported amphiphilic series with three heads and two tails allows for the development of an understanding of the relationship between number of tails and both colloidal and antibacterial properties.

The Re-Emergence and Emergence of Vector-Borne Rickettsioses in Taiwan.

Rickettsial diseases, particularly vector-borne rickettsioses (VBR), have a long history in Taiwan, with studies on scrub typhus and murine typhus dating back over a century. The climatic and geographic diversity of Taiwan's main island and its offshore islands provide many ecological niches for the diversification and maintenance of rickettsiae alike. In recent decades, scrub typhus has re-emerged as the most prevalent type of rickettsiosis in Taiwan, particularly in eastern Taiwan and its offshore islands. While murine typhus has also re-emerged on Taiwan's western coast, it remains neglected. Perhaps more alarming than the re-emergence of these rickettsioses is the emergence of newly described VBR. The first case of human infection with Rickettsia felis was confirmed in 2005, and undetermined spotted fever group rickettsioses have recently been detected. Taiwan is at a unique advantage in terms of detecting and characterizing VBR, as it has universal health coverage and a national communicable disease surveillance system; however, these systems have not been fully utilized for this purpose. Here, we review the existing knowledge on the eco-epidemiology of VBR in Taiwan and recommend future courses of action.

Colloidal and antibacterial properties of novel triple-headed, double-tailed amphiphiles: exploring structure-activity relationships and synergistic mixtures.

Two novel series of tris-cationic, tripled-headed, double-tailed amphiphiles were synthesized and the effects of tail length and head group composition on the critical aggregation concentration (CAC), thermodynamic parameters, and minimum inhibitory concentration (MIC) against six bacterial strains were investigated. Synergistic antibacterial combinations of these amphiphiles were also identified. Amphiphiles in this study are composed of a benzene core with three benzylic ammonium bromide groups, two of which have alkyl chains, each 8-16 carbons in length. The third head group is a trimethylammonium or pyridinium. Log of critical aggregation concentration (log[CAC]) and heat of aggregation (ΔHagg) were both inversely proportional to the length of the linear hydrocarbon chains. Antibacterial activity increases with tail length until an optimal tail length of 12 carbons per chain, above which, activity decreased. The derivatives with two 12 carbon chains had the best antibacterial activity, killing all tested strains at concentrations of 1-2µM for Gram-positive and 4-16µM for Gram-negative bacteria. The identity of the third head group (trimethylammonium or pyridinium) had minimal effect on colloidal and antibacterial activity. The antibacterial activity of several binary combinations of amphiphiles from this study was higher than activity of individual amphiphiles, indicating that these combinations are synergistic. These amphiphiles show promise as novel antibacterial agents that could be used in a variety of applications.

Complete Genome of Bacillus pumilus Siphophage Blastoid.

Phage Blastoid is a siphophage that infects Bacillus pumilus. B. pumilus is widely used in agriculture but has recently been linked to cases of food poisoning. Here, we report the complete genome of Blastoid and discuss unique genomic characteristics.