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Journal: Applied and environmental microbiology


Hot air hand dryers in multiple men’s and women’s bathrooms in 3 basic science research areas in an academic health center were screened for their deposition on plates of: i) total bacteria, some of which were identified; and ii) a kanamycin resistantBacillus subtilisstrain, PS533, spores of which are produced in large amounts in one basic science research laboratory. Plates exposed to hand dryer air for 30 seconds averaged 18-60 colonies/plate but interior hand dryer nozzle surfaces had minimal bacterial levels, plates exposed to bathroom air for 2 minutes with hand dryers off averaged ≤1 colony, and plates exposed to bathroom air moved by a small fan for 20 minutes had averages of 15 and 12 colonies/plate in two buildings tested. Retrofitting hand dryers with HEPA filters reduced bacterial deposition by hand dryers ∼4-fold, and potential human pathogens were recovered from plates exposed to hand dryer air whether or not a HEPA filter was present, and from bathroom air moved by a small fan. Spore-forming colonies, identified asB. subtilisPS533 averaged ∼2.5-5% of bacteria deposited by hand dryers throughout basic research areas examined regardless of distance from the spore forming laboratory, and these were almost certainly deposited as spores. Comparable results were obtained when bathroom air was sampled for spores. These results indicate that many kinds of bacteria, including potential pathogens and spores, can be deposited on hands exposed to bathroom hand dryers, and that spores could be dispersed throughout buildings and deposited on hands by hand dryers.ImportanceWhile there is evidence that bathroom hand dryers can disperse bacteria from hands or deposit bacteria on surfaces, including recently washed hands, there is less information on: i) the organisms dispersed by hand dryers; ii) if hand dryers provide a reservoir of bacteria or simply blow large amounts of bacterially contaminated air; and iii) if bacterial spores are deposited on surfaces by hand dryers. Consequently, this study has implications for the control of opportunistic bacterial pathogens and spores in public environments including healthcare settings. Within a large building, potentially pathogenic bacteria including bacterial spores may travel between rooms, and subsequent bacterial/spore deposition by hand dryers is a possible mechanism for spread of infectious bacteria including spores of potential pathogens if present.

Concepts: Bacteria, Microbiology, Research, Pathogen, Spore, Pathogenic bacteria, HEPA, Hand dryer


The development and continuous improvement of high-throughput sequencing platforms has stimulated interest in the study of complex microbial communities. Currently, the most popular sequencing approach to study microbial community composition and dynamics is targeted 16S rRNA gene metabarcoding. To prepare samples for sequencing, there are a variety of processing steps, each with the potential to introduce bias at the data analysis stage. In this short review, key information from the literature pertaining to each processing step is described and consequently, general recommendations for future 16S rRNA gene metabarcoding experiments are made.

Concepts: Archaea, Microbiology, Species, Ribosomal RNA, Biotechnology, 16S ribosomal RNA, 30S


In recent years, a greater appreciation for the microbes inhabiting human body sites has emerged. In the female mammary gland, milk has been shown to contain bacterial species, ostensibly from the skin. We decided to investigate whether there is a microbiome within the mammary tissue. Using 16S rRNA sequencing and culture, we analysed breast tissue from 81 women with and without cancer in Canada and Ireland. A diverse population of bacteria were detected within tissue collected from sites all around the breast in women aged 18 to 90, not all of whom had a history of lactating. The principal phylum was Proteobacteria. The most abundant taxa in the Canadian samples were Bacillus (11.4%), Acinetobacter (10.0%), unclassified Enterobacteriaceae (8.3%), Pseudomonas (6.5%), Staphylococcus (6.5%), Propionibacterium (5.8%), unclassified Comamonadaceae (5.7%), unclassified Gammaproteobacteria (5.0%) and Prevotella (5.0%). In the Irish samples the most abundant taxa were unclassified Enterobacteriaceae (30.8%), Staphylococcus (12.7%), Listeria welshimeri (12.1%), Propionibacterium (10.1%) and Pseudomonas (5.3%). None of the subjects had signs or symptoms of infection, but the presence of viable bacteria was confirmed in some samples by culture. The extent to which these organisms play a role in health or disease remains to be determined.

Concepts: Bacteria, Prolactin, Milk, Lactation, Breast, Mammary gland


This paper introduces a novel method for sampling pathogens in natural environments. It uses fabric boot socks worn over walkers' shoes allowing collection of composite samples over large areas. Wide area sampling is better suited to studies focussing upon human exposure to pathogens (e.g. recreational walking). This sampling method is implemented using a Citizen Science approach: groups of three walkers wearing boot socks undertook one of six routes, 40 times over 16 months in the North West (NW) and East Anglian (EA) regions of England. To validate this methodology we report the successful implementation of this Citizen Science approach, the observation that Campylobacter was detected on 47% of boot socks, and the observation that multiple boot socks from individual walks produced consistent results. Findings indicate elevated Campylobacter presence in the livestock dominated NW in comparison to EA (55.8% vs 38.6%). Seasonal variation in Campylobacter presence was found between regions, with indications of winter peaks in both regions, but a spring peak in NW. Campylobacter presence on boot socks was negatively associated with ambient temperature (p=0.011) and positively associated with precipitation (p<0.001), results which are consistent with our understanding of Campylobacter survival and the probability of material adhering to boot socks. C. jejuni was the predominant species found, with C. coli largely restricted to the livestock dominated NW. Source attribution analysis indicated that the potential source of C. jejuni was predominantly sheep in NW and wild birds in EA but did not vary between peak and non-peak periods of human incidence.Importance There is debate in the literature on the pathways through which pathogens transfer from the environment to humans. We report on the success of a novel method for sampling human-pathogen interactions using boot socks and citizen science techniques, which enable us to sample human-pathogen interactions that may occur through visits to natural environments. This contrasts with traditional environmental sampling, which is based upon spot sampling techniques and does not sample human-pathogen interactions. Our methods are of practical value to scientists trying to understand transmission of pathogens from the environment to people. Our findings provide insight into the risk of Campylobacter from recreational visits and an understanding of how these risks vary seasonally and the factors behind these patterns. We highlight the Campylobacter species predominantly encountered and the potential sources of the C. jejuni.

Concepts: Sample, Human, Sample size, Sampling, Environment, Natural environment, Nature, Campylobacter


In this study differences in the placental microbiota of term and preterm deliveries from a large UK pregnancy cohort were studied using 16S targeted amplicon sequencing. The impact of contamination from DNA extraction, PCR reagents, as well as those from delivery itself were also examined. A total of 400 placental samples from 256 singleton pregnancies were analysed and differences investigated between spontaneous preterm, non-spontaneous preterm, and term delivered placenta. DNA from recently delivered placenta was extracted, and screening for bacterial DNA was carried out using targeted sequencing of the 16S rRNA gene on the Illumina MiSeq platform. Sequenced reads were analysed for presence of contaminating operational taxonomic units (OTUs) identified via sequencing of negative extraction and PCR blank samples. Differential abundance and between sample (beta) diversity metrics were then compared. A large proportion of the reads sequenced from the extracted placental samples mapped to OTUs that were also found in negative extractions. Striking differences in the composition of samples were also observed, according to whether the placenta was delivered abdominally or vaginally, providing strong circumstantial evidence for delivery contamination as an important contributor to observed microbial profiles. When OTU and genus level abundances were compared between the groups of interest, a number of organisms were enriched in the spontaneous preterm cohort, including organisms that have been previously associated with adverse pregnancy outcomes, specifically Mycoplasma spp., and Ureaplasma spp.. However, analyses of overall community structure did not reveal convincing evidence for the existence of a reproducible ‘preterm placental microbiome’.IMPORTANCE Preterm birth is associated with both psychological and physical disabilities and is the leading cause of infant morbidity and mortality worldwide. Infection is known to be an important cause of spontaneous preterm birth, and recent research has implicated variation in the ‘placental microbiome’ with preterm birth risk. Consistent with previous studies, the abundance of certain clinically relevant species differed between spontaneous preterm and non-spontaneous preterm or term delivered placenta. These results support the view that a proportion of spontaneous preterm births have an intra-uterine infection component. However, an additional observation from this study was that a substantial proportion of reads sequenced were contaminating reads, rather than DNA from endogenous, clinically relevant species. This observation warrants caution in the interpretation of sequencing output from such low biomass samples as the placenta.


This study aimed at assessing the dynamics of lactic acid bacteria and other Firmicutes associated with durum wheat organs and processed products. 16S rRNA gene-based high-throughput sequencing approaches and culture-independent analyses showed that Lactobacillus, Streptococcus, Enterococcus and Lactococcus were the main epiphytic and endophytic genera among lactic acid bacteria. Bacillus, Exiguobacterium, Paenibacillus and Staphylococcus completed the picture of the core genera microbiome. The relative abundance of each lactic acid bacteria genus was affected by cultivars, phenological stages, other Firmicutes genera, environmental temperature and water activity (aw) of plant organs. Lactobacilli, showing the highest sensitivity to aw, markedly decreased during milk development (Odisseo) and physiological maturity (Saragolla). At these stages, Lactobacillus was mainly replaced by Streptococcus, Lactococcus and Enterococcus. However, a key sourdough species such as Lactobacillus plantarum was associated to plant organs during the life cycle of Odisseo and Saragolla wheat. The composition of the sourdough microbiota and the overall quality of leavened baked goods is also determined throughout the phenological stages of wheat cultivation, with variations depending on environmental and agronomic factors. Based on the adaptability of lactic acid bacteria on wheat plant, future research has to assess the potential of these bacteria for biocontrol and plant growth promotion.

Concepts: Bacteria, Microbiology, Streptococcus, Wheat, Lactobacillus, Firmicutes, Lactic acid bacteria, Lactobacillales


The food-borne pathogen Listeria (L) monocytogenes is able to survive a variety of stress conditions leading to the colonization of different niches like the food processing environment. This study focuses on the hypervariable genetic hotspot lmo0443-lmo0449 haboring three inserts: the stress survival islet 1 (SSI-1), the single-gene insert LMOf2365_0481 and two homologous genes of the non-pathogenic species L. innocua: lin0464, a putative transcriptional regulator and lin0465, an intracellular PfpI protease. Our prevalence study revealed a different distribution of the inserts between human and food-associated isolates. The lin0464-lin0465 insert was predominantly found in food-associated strains of sequence type (ST) 121. Functional characterization of this insert showed that the putative PfpI protease Lin0465 is involved in alkaline and oxidative stress response, but not in acidic, gastric, heat, cold, osmotic and antibiotic stress. In parallel, deletion of lin0464 decreased the survival under alkaline and oxidative stress. The expression of both genes increased significantly under oxidative stress conditions independently of the alternative sigma factor σ(B) Furthermore, we showed that the expression of the protease lin0465 is regulated by the transcription factor lin0464 under stress conditions, suggesting that lin0464 and lin0465 form a functional unit.In conclusion, we identified a novel stress survival islet 2 (SSI-2), predominantly present in L. monocytogenes ST121 strains, beneficial for survival under alkaline and oxidative stress, potentially supporting adaptation and persistence of L. monocytogenes in food processing environments.IMPORTANCEListeria (L.) monocytogenes strains of ST121 are known to persist for months and even years in food processing environments, thereby increasing the risk of food contamination and listeriosis. However, the molecular mechanism underlying this remarkable niche-specific adaptation is still unknown. Here, we demonstrate that the genomic islet SSI-2, predominantly present in L. monocytogenes ST121 strains, is beneficial for survival under alkaline and oxidative stress conditions, which are routinely encountered in food processing environments. Our findings suggest that SSI-2 is part of a diverse set of molecular determinants contributing to niche-specific adaptation and persistence of L. monocytogenes ST121 strains in food processing environments.

Concepts: DNA, Genetics, Gene expression, Transcription, Oxidative stress, Listeria monocytogenes, Listeria, Listeriosis


The South China Sea (SCS), the largest marginal sea in the Western Pacific Ocean, is a huge oligotrophic water body with very limited influx of nitrogenous nutrients. This suggests that sediment microbial N(2) fixation plays an important role in the production of bioavailable nitrogen. To test the molecular underpinning of this hypothesis, the diversity, abundance, biogeographical distribution, and community structure of the sediment diazotrophic microbiota were investigated at 12 sampling sites, including estuarine, coastal, offshore, deep-sea, and methane hydrate reservoirs or their prospective areas by targeting nifH and some other functional biomarker genes. Diverse and novel nifH sequences were obtained, significantly extending the evolutionary complexity of extant nifH genes. Statistical analyses indicate that sediment in situ temperature is the most significant environmental factor influencing the abundance, community structure, and spatial distribution of the sediment nifH-harboring microbial assemblages in the northern SCS (nSCS). The significantly positive correlation of the sediment pore water NH(4)(+) concentration with the nifH gene abundance suggests that the nSCS sediment nifH-harboring microbiota is active in N(2) fixation and NH(4)(+) production. Several other environmental factors, including sediment pore water PO(4)(3-) concentration, sediment organic carbon, nitrogen and phosphorus levels, etc., are also important in influencing the community structure, spatial distribution, or abundance of the nifH-harboring microbial assemblages. We also confirmed that the nifH genes encoded by archaeal diazotrophs in the ANME-2c subgroup occur exclusively in the deep-sea methane seep areas, providing for the possibility to develop ANME-2c nifH genes as a diagnostic tool for deep-sea methane hydrate reservoir discovery.

Concepts: Archaea, Bacteria, Water, Hydrogen, Pacific Ocean, Ocean, South China Sea, East China Sea


Evaluating different swabbing materials for spore recovery efficiency (RE) from steel surfaces, we recorded the maximum RE (71%) of 10(7) Bacillus subtilis spores with Tulips cotton buds, followed by Johnson’s cotton buds and standard Hi-Media cotton, polyester, nylon, and foam (23%) swabs. Among cotton swabs, instant water-absorbing capacity or the hydrophilicity index appeared to be the major indicator of RE, as determined by testing three more brands. Tulips swabs worked efficiently across diverse nonporous surfaces and on different Bacillus spp., registering 65 to 77% RE.

Concepts: Cotton, Spore, Bacillus, Asexual reproduction, Bacillus subtilis, Endospore, American inventions, Cotton swab


Recent studies suggest the involvement of water in the epidemiology of Cyclospora cayetanensis and some microsporidia. A total of 223 samples from four drinking water treatment plants (DWTPs), seven wastewater treatment plants (WWTPs), and six locations of influence (LI) on four river basins from Madrid, Spain, were analyzed from spring 2008 to winter 2009. Microsporidia were detected in 49% of samples (109/223), Cyclospora spp. were detected in 9% (20/223), and both parasites were found in 5.4% (12/223) of samples. Human-pathogenic microsporidia were detected, including Enterocytozoon bieneusi (C, D, and D-like genotypes), Encephalitozoon intestinalis, Encephalitozoon cuniculi (genotypes I and III), and Anncaliia algerae. C. cayetanensis was identified in 17 of 20 samples. To our knowledge, this is the first study that shows a year-long longitudinal study of C. cayetanensis in drinking water treatment plants. Additionally, data about the presence and molecular characterization of the human-pathogenic microsporidia in drinking water, wastewater, and locations of influence during 1 year in Spain are shown. It is noteworthy that although the DWTPs and WWTPs studied meet European and national regulations on water sanitary quality, both parasites were found in water samples from these plants, supporting the idea that new and appropriate controls and regulations for drinking water, wastewater, and recreational waters should be proposed to avoid health risks from these pathogens.

Concepts: Water, Water pollution, Sociology, Sewage treatment, Cultural studies, Wastewater, Water treatment, Microsporidiosis