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The aerodynamic sizes of bioaerosols may significantly affect their behaviors, respiratory deposition and biodiversity. The respirable bacterial size, biodiversity, and human-associated bacteria (HAB) related bioaerosols were evaluated at three kindergartens in Taiwan. Kindergartens A, B, and C were in urban, semi-urban, and rural areas, respectively. A six-stage viable Andersen cascade impactor was used to collect bioaerosols and to determine their size distributions. The geometric mean diameter (GMD), geometric standard deviation (GSD), heat maps, and uniformity were used to evaluate the association of bacteria characteristics. A BD Phoenix-100 automated interpretation system was used to identify the airborne bacteria species. The results revealed that 1425 colonies of the sampled airborne bacteria contained 63 species in 29 genera, and overall, 63.0% were HABs. The most abundant phylum was Actinobacteria (56.6 ± 22.2%) and Firmicutes (31.6 ± 22.3%), and from the taxonomic analysis, both airborne Micrococcus and the Staphylococcus aureus are the dominant genus. All the bacteria aerodynamic particle size distributions were polydisperse distributions. The heat map and uniformity analysis had revealed most of the sampled bioaerosols distributed between 1.1-3.3 µm, and most of the polydisperse airborne Streptococcus spp. had a size in the respirable range, due to urbanization, they have potentially contributed to respiratory risk in the kindergartens. The Shannon diversity index (H) and inverse Simpson diversity index (D) of the bioaerosols in urban kindergarten were negatively correlated with GMD and GSD. The Pearson correlations revealed that the kindergarten in the rural area, with a higher temperature, a lower relative humidity, and a lower CO2 concentration than the others, tended to have the largest H and D values (P < 0.05). Multiple and stepwise regression revealed that bioaerosol aerodynamic size was statistically significantly correlated with H (P = 0.001) and D values (P = 0.002). This study sheds light on the characteristics of bioaerosols and their associations with microbiome.

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Humans and plants have evolved in the near omnipresence of a microbial milieu, and the factors that govern host-microbe interactions continue to require scientific exploration. To better understand if and to what degree patterns between microbial genomic features and host association (i.e., human and plant) exist, I analyzed the genomes of select Burkholderia strains-a bacterial genus comprised of both human and plant-associated strains-that were isolated from either humans or plants. To this end, I uncovered host-specific, genomic patterns related to metabolic pathway potentials in addition to convergent features that may be related to pathogenic overlap between hosts. Together, these findings detail the genomic associations of human and plant-associated Burkholderia strains and provide a framework for future investigations that seek to link host-host transmission potentials.

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Airborne bacteria in hospitals have been implicated in nosocomial infections. This investigation studied the characteristics of airborne bacteria and the effect of patient visitation on the bacteria profile in intensive care units (ICUs). Air at a medical ICU and surgical ICU was sampled for one year. Airborne bacteria before and during visits to patients in ICUs were collected using a Six-Stage Viable Andersen Cascade Impactor to analyze the concentration and size distribution of airborne bacteria and the percentage thereof that were antibiotic-resistant. During patient visitation in the ICUs in this study, the number of visitors was 20-80. Airborne bacteria concentration during visiting hours (total averaging 168.5 CFU/m3) was three to four times than before visiting hours (p = 0.043). With increasing the visitors, most of the airborne human-associated bacteria (HAB) concentrations during visitations were higher than before visitations in each season. The two-way ANOVA of HAB concentration before and during visitation (p = 0.028) of combining MICU and SICU in various season (p = 0.007) all revealed statistical agreement. The proportion of particles, from 1.1 to 4.7 µm, during the visits was almost 1-2.4 times that before the visits in most sampling periods (p = 0.028). In addition, the opportunistic pathogens such as Micrococcus spp., Staphylococcus spp. and Acinetobacter spp. were found in the air during visiting times. Small proportions of some environmental strains with a high antibiotic-resistance percentage (42-78%), including Brevundimonas spp., Elizabethkingia spp. and others, were detected during patient visitation. Patient visitation activities affect the bacterial profile in air in ICUs. During the visitation, visitors might bring or generate bacteria into ICUs. Limiting the number of patient visitors to ICUs, wearing respirators and gowns or increasing ventilation rate during and after patient visitation is required to maintain indoor air quality and probably decrease the risk of patient infection.

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Akiyoshi-do Cave is one of the oldest and the largest show caves in Japan. Environmental alterations induced by tourism impacts have been suggested; however, only a few previous studies have investigated the impacts of tourism on the cave. In this study, enrichment culture procedures were applied to detect human-associated bacteria (HAB) including Escherichia coli, Staphylococcus aureus, and thermo-tolerant Bacillus spp. in cave water. Physical and bacterial parameters of water including total nitrogen, ammonia, phosphate, total number of bacteria, and total number of viable bacteria were collected as environmental factors. Escherichia coli was absent at all sites, but increased levels of total bacteria, viable bacteria, S. aureus, and thermo-tolerant Bacillus spp. were present at high-impact sites. Examination of the origin tracking of HAB suggested that cave tourists could be a source of HAB contamination, but other causes related to the surface land use could also contribute to HAB contamination. © 2020 Water Environment Federation PRACTITIONER POINTS: Detection of HAB was performed for the first time in Japanese show caves to consider tourism impacts. The greater number of HAB was detected from the tourist area than the nontourist area in the cave. It was suggested that the origin of HAB may not be limited to tourists, but may also include the surface.

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Anthropogenic influences in the southern polar region have been rare, but lately microorganisms associated with humans have reached Antarctica, possibly from military bases, fishing boats, scientific expeditions, and/or ship-borne tourism. Studies of seawater in areas of human intervention and proximal to fresh penguin feces revealed the presence of Escherichia coli strains least resistant to antibiotics in penguins, whereas E. coli from seawater elsewhere showed resistance to one or more of the following antibiotics: ampicillin, tetracycline, streptomycin, and trim-sulfa. In seawater samples, bacteria were found carrying extended-spectrum ß-lactamase (ESBL)-type CTX-M genes in which multilocus sequencing typing (MLST) showed different sequence types (STs), previously reported in humans. In the Arctic, on the contrary, people have been present for a long time, and the presence of antibiotic resistance genes (ARGs) appears to be much more wide-spread than was previously reported. Studies of E coli from Arctic birds (Bering Strait) revealed reduced susceptibility to antibiotics, but one globally spreading clone of E. coli genotype O25b-ST131, carrying genes of ESBL-type CTX-M, was identified. In the few years between sample collections in the same area, differences in resistance pattern were observed, with E. coli from birds showing resistance to a maximum of five different antibiotics. Presence of resistance-type ESBLs (TEM, SHV, and CTX-M) in E. coli and Klebsiella pneumoniae was also confirmed by specified PCR methods. MLST revealed that those bacteria carried STs that connect them to previously described strains in humans. In conclusion, bacteria previously related to humans could be found in relatively pristine environments, and presently human-associated, antibiotic-resistant bacteria have reached a high global level of distribution that they are now found even in the polar regions.