Stress modulation as a means to improve yeasts for lignocellulose bioconversion.

The second-generation (2G) fermentation environment for lignocellulose conversion presents unique challenges to the fermentative organism that do not necessarily exist in other industrial fermentations. While extreme osmotic, heat, and nutrient starvation stresses are observed in sugar- and starch-based fermentation environments, additional pre-treatment-derived inhibitor stress, potentially exacerbated by stresses such as pH and product tolerance, exist in the 2G environment. Furthermore, in a consolidated bioprocessing (CBP) context, the organism is also challenged to secrete enzymes that may themselves lead to unfolded protein response and other stresses. This review will discuss responses of the yeast Saccharomyces cerevisiae to 2G-specific stresses and stress modulation strategies that can be followed to improve yeasts for this application. We also explore published -omics data and discuss relevant rational engineering, reverse engineering, and adaptation strategies, with the view of identifying genes or alleles that will make positive contributions to the overall robustness of 2G industrial strains. KEYPOINTS: • Stress tolerance is a key driver to successful application of yeast strains in biorefineries. • A wealth of data regarding stress responses has been gained through omics studies. • Integration of this knowledge could inform engineering of fit for purpose strains.

Weak Decay of Magnetized Pions.

The leptonic decay of charged pions is investigated in the presence of background magnetic fields. In this situation, Lorentz symmetry is broken, and new fundamental decay constants need to be introduced, associated with the decay via the vector part of the electroweak current. We calculate the magnetic field dependence of both the usual and a new decay constant nonperturbatively on the lattice. We employ both Wilson and staggered quarks and extrapolate the results to the continuum limit. With this nonperturbative input, we calculate the tree level electroweak amplitude for the full decay rate in strong magnetic fields. We find that the muonic decay of the charged pion is enhanced drastically by the magnetic field. We comment on possible astrophysical implications.

Small dense LDL cholesterol in human subjects with different chronic inflammatory diseases.

BACKGROUND AND AIMS: Chronic inflammatory diseases (CID) are associated with a profound increase in cardiovascular (CV) risk resulting in reduced life expectancy. However, LDL-cholesterol is reported to be low in CID patients which is referred to as the "LDL paradoxon". The aim of the present study was to investigate whether LDL-particles in CID exhibit an increased content of the highly atherogenic small-dense LDL subfraction (sdLDL). METHODS AND RESULTS: In this prospective, single center, observational study we enrolled 141 patients with CID (RA n = 59, inflammatory bowel disease (IBD) n = 35, ankylosing spondylitis (SpA) n = 25, Psoriasis n = 22) in 2011 through 2013 to evaluate sdLDL levels before as well as 6 and 26 weeks after initiation of different anti-cytokine therapies (anti-TNFα, anti-IL-6R antibodies). sdLDL levels were compared to 141 healthy individuals in a case control design. Compared to healthy controls, all CID patients displayed a significantly higher sdLDL content within the LDL cholesterol fraction: RA 35.0 ± 9.2% (p < 0.001), SpA 42.5 ± 10.5% (p < 0.001), IBD 37.5 ± 7.1% (p < 0.001), Psoriasis 33.6 ± 4.6% (p < 0.01). Furthermore, the sdLDL/LDL ratio was significantly higher in male compared to female RA subjects (p < 0.05). Neither anti-TNFα nor anti-IL6R medication altered sdLDL levels despite a significant improvement of disease activity. CONCLUSION: In several different chronic inflammatory disease entities, LDL-cholesterol is shifted toward a pro-atherogenic phenotype due to an increased sdLDL content which might in part explain the LDL paradoxon. Since premature CV disease is a major burden of affected patients, specifically targeting lipid metabolism should be considered routinely in clinical patient care. CLINICAL TRIALS: Registration at German Clinical Trial Register (DRKS): DRKS00005285.

Fetal Brain MRI: Novel Classification and Contribution to Sonography.

PURPOSE: 1) To evaluate and classify the indications for fetal brain MRI in a tertiary referral center. 2) To assess the contribution of fetal brain MRI to fetal neurosonography. MATERIALS AND METHODS: A retrospective study in a tertiary medical center during a two-year period (2011 - 2012) included pregnant women who underwent fetal brain MRI. MRI was implemented at 32 weeks of gestation unless a severe abnormality possibly requiring earlier medical intervention was suspected. RESULTS: 633 patients were included, 40 (6.3%) underwent repeated examinations with a total of 733 fetal MRI scans. Patients were classified to three main indication cohorts: Suspected primary brain anomaly (52.9%), non-CNS disorders (32.5%) and obstetrical complications (14.6%). These cohorts were further divided into 16 separate groups with lateral ventricle abnormalities being the most common (23.7%), followed by exposure to TORCH (17.5%) and cerebral cortex abnormalities (13%). 149 (19.3%) fetal MRI scans demonstrated additional findings. Repeated examinations were commonly implemented in complicated monochorionic-biamniotic (MCBA) twin pregnancies (34.6%) and in cases of supra-tentorial cysts (19%). The average gestational age for MRI scan in the MCBA group was 26 ±â€Š5 weeks in comparison to ≥ 31st weeks in all other groups (p < 0.001). CONCLUSION: The current study describes a detailed picture of fetal brain MRI indications. Most patients were referred because of CNS anomalies. The impressive diversity of 16 separate entities emphasizes the expanding use of fetal brain MRI. Complicated MCBA pregnancies, which may have dramatic events, constitute a unique challenge due to early and repetitive MRI examinations and may serve as a role model for the contribution of fetal MRI during antenatal evaluation. The contribution of MRI to prenatal evaluation in various indications is discussed.

The effect of propidium monoazide treatment on the measured bacterial composition of clinical samples after the use of a mouthwash.

OBJECTIVES: The use of an anti-microbial mouthwash results not only in a reduction of the number of viable cells in dental plaque but potentially also in a shift in the oral microbiome. DNA-based techniques may be appropriate to monitor these shifts, but these techniques amplify DNA from both dead and living cells. Propidium monoazide (PMA) has been used to overcome this problem, by preventing the amplification of DNA from membrane-damaged cells. The aim of this study was to evaluate the use of PMA when measuring compositional shifts in clinical samples after mouthwash use. MATERIALS AND METHODS: On two consecutive days, baseline samples from buccal surfaces, tongue, and saliva were obtained from six volunteers, after which they used a mouthwash (Meridol, GABA, Switzerland) twice daily for 14 days. Subsequently similar samples were obtained on two consecutive days. The microbial composition of the samples, with or without ex vivo PMA treatment, was assessed with 16S rRNA gene amplicon sequencing. RESULTS: Data showed a clear effect of mouthwash usage on the tongue and saliva samples. PMA treatment enhanced the observed differences only for the saliva samples. Mouthwash treatments did not affect the composition of the plaque samples irrespective of the use of PMA. CONCLUSION: The necessity to use a PMA treatment to block the DNA from dead cells in clinical studies aimed at measuring compositional shifts after the use of a mouthwash is limited to salivary samples. CLINICAL RELEVANCE: Measuring shifts in the oral microbiome could be hampered by the presence of DNA from dead cells.

Intra- and postoperative catumaxomab in patients with epithelial ovarian cancer: safety and two-year efficacy results from a multicentre, single-arm, phase II study.

BACKGROUND: This is the first study investigating the safety and efficacy of the trifunctional antibody catumaxomab administered i.p. at the end of cytoreductive surgery and postoperatively prior to standard chemotherapy in patients with primary epithelial ovarian cancer (EOC). METHODS: Patients received i.p. catumaxomab 10 µg intraoperatively and 10, 20, 50 and 150 µg on days 7, 10, 13 and 16, respectively, postoperatively. After the study, patients received standard chemotherapy and were followed for 23 months. The primary endpoint was the rate of postoperative complications. RESULTS: Forty-one patients entered the study and were evaluable for safety and 34 were alive at 24 months. Complete tumour resection rate was 68%. Postoperative complications were observed in 51%, the most common anastomotic leakage (7%) and wound infections (5%). The most common catumaxomab-related adverse events were abdominal pain, nausea, vomiting and pyrexia. Thirty-nine percent discontinued catumaxomab therapy, and 98% received chemotherapy post study. Kaplan-Meier estimates of disease-free and overall survival after 24 months were 56% and 85%, respectively. CONCLUSIONS: Intra- and close postoperative catumaxomab seems feasible, but efficacy and safety were limited by postsurgical complications. In the future prospective trials are needed to investigate the best schedule of integration of catumaxomab into current treatment strategies for EOC.

Calcium isotope composition in serum and urine for the assessment of bone mineral balance (BMB) - The Osteolabs post-market follow-up study.

To further explore the clinical applicability of the calcium (Ca) isotope marker (CIM), we determined the 44Ca/42Ca isotope ratio in blood serum and urine. This ratio is expressed in the conventional δ-notation (as defined in the text below) specifically as CIM-serum for serum and as CIM-urine for urine. Our study tested the hypothesis that CIM values can differentiate between positive and negative bone mineral balance (BMB) across a diverse clinical population considering variables such as age, gender, and diet. The threshold values (CIM-serum: -0.85 ±â€¯0.06 ‰ and CIM-urine: 0.23 ±â€¯0.06 ‰) established in the OsteoGeo study (NCT02967978, Eisenhauer et al., 2019) were evaluated in 2320 participants as part of a surveillance study referred to as Osteolabs study. The earlier study revealed women with osteoporosis had an average CIM-serum value of -0.91 ±â€¯0.21 ‰ (N = 24) and a CIM-urine value of 0.18 ±â€¯0.33 ‰ (N = 71) that are significantly below the threshold values (p = 0.02 for urine, one-sided Wilcoxon rank test, p < 0.001 for serum, one-sided Student's t-test). Diseases affecting BMB such as osteoporosis, acute and chronic kidney disease (CKD), hyperthyroidism, breast cancer, prostate cancer, and myeloma were associated with significantly lower average CIM values, falling below the equilibrium thresholds and indicating negative BMB. In contrast, patients receiving osteoprotective treatments such as denosumab, Romosozumab, bisphosphonates, or hormone replacement therapy for certain diseases, had CIM values above the equilibrium thresholds indicating a positive BMB. Additionally, Ca supplements taken by some of the patients ((N = 22 (serum), N = 49 (urine), median dose: 500 mg) showed a Ca isotope composition approximately 1 ‰ higher than that from a normal diet. Consequently, their CIM values need to be adjusted to account for the amount and duration of supplementation to be comparable to those with a normal diet. Participants taking vitamin D (237 women; 58 men) showed no significant difference from the average values of the study group. Counterintuitively, the possible impact of malnutrition on individual BMB was most pronounced in vegans, who exhibited the highest average CIM-urine values compared to patients on a normal diet (p < 0.001, N = 17). The results of this study were consistent with the registered OsteoGeo study (NCT02967978) and other earlier published Ca isotope-based studies on BMB. We confirm that the CIM threshold values determined in the OsteoGeo study are generally valid for this much larger and diverse surveillance study group covering a diverse population encompassing various medical conditions and therapies.

Different mechanisms preserve translation of programmed cell death 8 and JunB in virus-infected endothelial cells.

OBJECTIVE: Translation initiation of eukaryotic mRNAs typically occurs by cap-dependent ribosome scanning mechanism. However, certain mRNAs are translated by ribosome assembly at internal ribosome entry sites (IRESs). Whether IRES-mediated translation occurs in stressed primary human endothelial cells (ECs) is unknown. METHODS AND RESULTS: We performed microarray analysis of polyribosomal mRNA from ECs to identify IRES-containing mRNAs. Cap-dependent translation was disabled by poliovirus (PV) infection and confirmed by loss of polysome peaks, detection of eukaryotic initiation factor (eIF) 4G cleavage, and decreased protein synthesis. We found that 87.4% of mRNAs were dissociated from polysomes in virus-infected ECs. Twelve percent of mRNAs remained associated with polysomes, and 0.6% were enriched ≥2-fold in polysome fractions from infected ECs. Quantitative reverse transcription-polymerase chain reaction confirmed the microarray findings for 31 selected mRNAs. We found that enriched polysome associations of programmed cell death 8 (PDCD8) and JunB mRNA resulted in increased protein expression in PV-infected ECs. The presence of IRESs in the 5' untranslated region of PDCD8 mRNA, but not of JunB mRNA, was confirmed by dicistronic analysis. CONCLUSIONS: We show that microarray profiling of polyribosomal mRNA transcripts from PV-infected ECs successfully identifies mRNAs whose translation is preserved in the face of stress-induced, near complete cessation of cap-dependent initiation. Nevertheless, internal ribosome entry is not the only mechanism responsible for this privileged translation.

Microbial Indicators of Dental Health, Dysbiosis, and Early Childhood Caries.

Dental caries lesions are a clinical manifestation of disease, preceded by microbial dysbiosis, which is poorly characterized and thought to be associated with saccharolytic taxa. Here, we assessed the associations between the oral microbiome of children and various caries risk factors such as demographics and behavioral and clinical data across early childhood and characterized over time the salivary and dental plaque microbiome of children before clinical diagnosis of caries lesions. Children (N = 266) were examined clinically at ~1, 2.5, 4, and 6.5 y of age. The microbiome samples were collected at 1, 2.5, and 4 y. Caries groups consisted of children who remained caries free (International Caries Detection and Assessment System [ICDAS] = 0) at all time points (CFAT) (n = 50); children diagnosed with caries (ICDAS ≥ 1) at 6.5 y (C6.5), 4 y (C4), or 2.5 y of age (C2.5); and children with early caries or advanced caries lesions at specific time points. Microbial community analyses were performed on zero-radius operational taxonomic units (zOTUs) obtained from V4 of 16S ribosomal RNA gene amplicon sequences. The oral microbiome of the children was affected by various factors, including antibiotic use, demographics, and dietary habits of the children and their caregivers. At all time points, various risk factors explained more of the variation in the dental plaque microbiome than in saliva. At 1 y, composition of saliva of the C4 group differed from that of the CFAT group, while at 2.5 y, this difference was observed only in plaque. At 4 y, multiple salivary and plaque zOTUs of genera Prevotella and Leptotrichia were significantly higher in samples of the C6.5 group than those of the CFAT group. In conclusion, up to 3 y prior to clinical caries detection, the oral microbial communities were already in a state of dysbiosis that was dominated by proteolytic taxa. Plaque discriminated dysbiotic oral ecosystems from healthy ones better than saliva.

Long-lived states to sustain hyperpolarized magnetization.

Major breakthroughs have recently been reported that can help overcome two inherent drawbacks of NMR: the lack of sensitivity and the limited memory of longitudinal magnetization. Dynamic nuclear polarization (DNP) couples nuclear spins to the large reservoir of electrons, thus making it possible to detect dilute endogenous substances in magnetic resonance spectroscopy (MRS) and magnetic resonance imaging (MRI). We have designed a method to preserve enhanced ("hyperpolarized") magnetization by conversion into long-lived states (LLS). It is shown that these enhanced long-lived states can be generated for proton spins, which afford sensitive detection. Even in complex molecules such as peptides, long-lived proton states can be sustained effectively over time intervals on the order of tens of seconds, thus allowing hyperpolarized substrates to reach target areas and affording access to slow metabolic pathways. The natural abundance carbon-13 polarization has been enhanced ex situ by almost four orders of magnitude in the dipeptide Ala-Gly. The sample was transferred by the dissolution process to a high-resolution magnet where the carbon-13 polarization was converted into a long-lived state associated with a pair of protons. In Ala-Gly, the lifetime T(LLS) associated with the two nonequivalent H(alpha) glycine protons, sustained by suitable radio-frequency irradiation, was found to be seven times longer than their spin-lattice relaxation time constant (T(LLS)/T(1) = 7). At desired intervals, small fractions of the populations of long-lived states were converted into observable magnetization. This opens the way to observing slow chemical reactions and slow transport phenomena such as diffusion by enhanced magnetic resonance.

C21orf91 genotypes correlate with herpes simplex labialis (cold sore) frequency: description of a cold sore susceptibility gene.

BACKGROUND: Herpes simplex virus type 1 (HSV-1) infects >70% of the United States population. We identified a 3-megabase region on human chromosome 21 containing 6 candidate genes associated with herpes simplex labialis (HSL, "cold sores"). METHODS: We conducted single nucleotide polymorphism (SNP) scans of the chromosome 21 region to define which of 6 possible candidate genes were associated with cold sore frequency. We obtained the annual HSL frequency for 355 HSV-1 seropositive individuals and determined the individual genotypes by SNPlex for linkage analysis and parental transmission disequilibrium testing (ParenTDT). RESULTS: Two-point linkage analysis showed positive linkage between cold sore frequency and 2 SNPs within the C21orf91 region, 1 of which is nonsynonymous. ParenTDT analysis revealed a strong association between another C21orf91 SNP, predicted to lie in the 3' untranslated region, and frequent HSL (P = .0047). C21orf 91 is a predicted open reading frame of unknown function that encodes a cytosolic protein. CONCLUSIONS: We evaluated candidate genes in the cold sore susceptibility region using fine mapping with 45 SNP markers. 2 complementary techniques identified C21orf91 as a gene of interest for susceptibility to HSL. We propose that C21orf91 be designated the Cold Sore Susceptibility Gene-1 (CSSG1).

Subgingival Microbiota during Healthy Pregnancy and Pregnancy Gingivitis.

INTRODUCTION: Previous studies have largely explored the microbial composition and pathogenesis of pregnancy gingivitis. However, the patterns of microbial colonization during pregnancy in the absence of pregnancy gingivitis have rarely been studied. Characterization of the oral microbiome in pregnant women with healthy gingiva is an important initial step in understanding the role of the microbiome in progression to pregnancy gingivitis. OBJECTIVES: In this study, we compared the oral microbiome of pregnant women without gingivitis (healthy pregnancy) with pregnant women having gingivitis and nonpregnant healthy women to understand how pregnancy modifies the oral microbiome and induces progression to pregnancy gingivitis. METHODS: Subgingival plaque samples were collected from Chinese pregnant women with gingivitis (n = 10), healthy pregnant women (n = 10), and nonpregnant healthy women (n = 10). The Illumina MiSeq platform was used to perform 16S rRNA gene sequencing targeting the V4 region. RESULTS: The alpha and beta diversity was significantly different between pregnant and nonpregnant women, but minimal differences were observed between pregnant women with and without gingivitis. Interestingly, the oral bacterial community showed higher abundance of pathogenic taxa during healthy pregnancy as compared with nonpregnant women despite similar gingival and plaque index scores. However, when compared with overt pregnancy gingivitis, pathogenic taxa were less abundant during healthy pregnancy. PICRUSt analysis (phylogenetic investigation of communities by reconstruction of unobserved states) also suggested no difference in the functional capabilities of the microbiome during pregnancy, irrespective of gingival disease status. However, metabolic pathways related to amino acid metabolism were significantly increased in healthy pregnant women as compared with nonpregnant women. CONCLUSION: The presence of pathogenic taxa in healthy pregnancy and pregnancy gingivitis suggests that bacteria may be necessary for initiating disease development but progression to gingivitis may be influenced by the host environmental factors. More efforts are required to plan interventions aimed at sustaining health before the appearance of overt gingivitis. KNOWLEDGE TRANSFER STATEMENT: The results of this study draw attention to the importance of oral health maintenance during pregnancy, as women without any prenatal oral conditions are predisposed to the risk of developing pregnancy gingivitis. Hence, it is important to incorporate comprehensive assessment of oral health in the prenatal health care schedules. Pregnant woman should be screened for oral risks, counseled on proper oral hygiene and expected oral changes, and referred for dental treatment, when necessary.

IgA-dependent, monocyte-mediated, antibacterial activity.

IgA purified from the sera of patients convalescing from disseminated group C meningococcal disease induced human monocyte-mediated anti-meningococcal activity in vitro in the absence of complement. Both IgA- and IgG-dependent activity were directed against the group C meningococcal polysaccharide (Csss) capsule. The amount of IgA that was effective bound less than 1 ng of Csss. Antibacterial activity was dependent upon the length and the temperature of the test incubation and on the concentration of monocytes. The implications of this mechanism for local cell-mediated antibacterial immunity are discussed.

Hyperpolarizing gases via dynamic nuclear polarization and sublimation.

A high throughput method was designed to produce hyperpolarized gases by combining low-temperature dynamic nuclear polarization with a sublimation procedure. It is illustrated by applications to 129Xe nuclear magnetic resonance in xenon gas, leading to a signal enhancement of 3 to 4 orders of magnitude compared to the room-temperature thermal equilibrium signal at 7.05 T.

Home sampling is a feasible method for oral microbiota analysis for infants and mothers.

OBJECTIVES: Large longitudinal cohort studies in infants are needed to understand oral microbiome maturation in relation to general health. The logistics of such studies are complex and costs involved high. Methods like home sampling by caretakers might be a solution to these issues. This study aimed to evaluate feasibility of home sampling by caretakers and to assess which oral niche provides the most reliable sample. METHODS: In this cross-sectional study 30 mothers and their infants aged 2-15 months participated. Swabs of the tongue, buccal mucosa, saliva, and dental plaque of the mother and the infant were collected by the mother after watching an instruction video. Thereafter, the trained researcher repeated the sample collection. Variations on the sampling protocol were listed. Bacterial DNA was quantified and microbial composition was assessed using 16S rDNA amplicon sequencing. RESULTS: None of the sampled niches appeared to be unfeasible based on interviews and observed variations on protocol. No significant differences in bacterial DNA concentration between operators (mother and researcher) were found. In infant's saliva, Shannon diversity of samples collected by the researcher was significantly higher than those collected by mothers (p = 0.0009) and the bacterial composition was influenced by variations on sampling protocol (p = 0.01). CONCLUSIONS: Home sampling by caretakers is a feasible method for oral sample collection in infants and mothers. Oral samples collected by mothers resemble samples collected by a trained researcher, with the tongue sample being the most similar and saliva the least. CLINICAL SIGNIFICANCE: Home sampling can simplify longitudinal oral microbiota collection.

Impact of the early-life skin microbiota on the development of canine atopic dermatitis in a high-risk breed birth cohort.

Canine atopic dermatitis (CAD) is a prevalent inflammatory skin disease of dogs worldwide. Certain breeds such as the West Highland White Terriers (WHWT) are predisposed to suffer from CAD. Microbial dysbiosis is known to play a significant role in the pathogenesis of the disease, which is similar to its human counterpart, atopic dermatitis (AD). To date, no large cohort-study has been conducted in a predisposed dog breed to study the impact of the early-life microbiota on the development of CAD, as well as the possible implication of factors such as hygiene and access to the outdoors. In this study skin samples of 143 WHWT, including 109 puppies up to three weeks old and 34 parent dogs, from 17 breeders, were subjected to 16S rRNA gene and ITS2 amplicon sequencing to disclose the bacterial and fungal oral and skin microbiota, respectively. The oral samples served as a control group to confirm differences between haired and mucosal surfaces. The cutaneous microbiota differed between sample sites and age of the dogs. The season of sampling, geographical origin as well as hygiene status of the household and the access to the outdoors shaped the skin microbiota of the puppies significantly. However, we found that the individual early-life microbiota did not predispose for the later development of CAD.

Maturation of the Oral Microbiome in Caries-Free Toddlers: A Longitudinal Study.

Understanding the development of the oral microbiota in healthy children is of great importance to oral and general health. However, limited data exist on a healthy maturation of the oral microbial ecosystem in children. Moreover, the data are biased by mislabeling "caries-free" populations. Therefore, we aimed to characterize the healthy salivary and dental plaque microbiome in young children. Caries-free (ICDAS [International Caries Detection and Assessment System] score 0) children (n = 119) and their primary caregivers were followed from 1 until 4 y of child age. Salivary and dental plaque samples were collected from the children at 3 time points (T1, ~1 y old; T2, ~2.5 y old; and T3, ~4 y old). Only saliva samples were collected from the caregivers. Bacterial V4 16S ribosomal DNA amplicons were sequenced using Illumina MiSeq. The reads were denoised and mapped to the zero-radius operational taxonomic units (zOTUs). Taxonomy was assigned using HOMD. The microbial profiles of children showed significant differences (P = 0.0001) over time. Various taxa increased, including Fusobacterium, Actinomyces, and Corynebacterium, while others showed significant decreases (e.g., Alloprevotella and Capnocytophaga) in their relative abundances over time. Microbial diversity and child-caregiver similarity increased most between 1 and 2.5 y of age while still not reaching the complexity of the caregivers at 4 y of age. The microbiome at 1 y of age differed the most from those at later time points. A single zOTU (Streptococcus) was present in all samples (n = 925) of the study. A large variation in the proportion of shared zOTUs was observed within an individual child over time (2% to 42% of zOTUs in saliva; 2.5% to 38% in dental plaque). These findings indicate that the oral ecosystem of caries-free toddlers is highly heterogeneous and dynamic with substantial changes in microbial composition over time and only few taxa persisting across the 3 y of the study. The salivary microbiome of 4-y-old children is still distinct from that of their caregivers.

Dental aerosols: microbial composition and spatial distribution.

Background: High-speed dental instruments produce aerosols, which can contribute to the transmission of pathogenic microorganisms. The aim of this study is to describe the microbial load and - composition and spatial distribution of aerosols in dental clinics. Methods: In four dental clinics active and passive sampling methods were used before, during and after treatment and at different locations. Retrieved colony forming units (CFU) were sequenced for taxon identification. Results: The samples contained up to 655 CFU/plate/30 minutes and 418 CFU/m3/30 minutes during dental treatment for active and passive sampling, respectively. The level of contamination after treatment and at 1.5 m distance from the patient's head was similar to the start of the day. The highest contamination was found at the patient's chest area. The aerosols consisted of 52 different taxa from human origin and 36 from water. Conclusion: Contamination in dental clinics due to aerosols is mainly low, although high level of contamination with taxa from both human and water origin was found within 80 cm around the head of the patient. Our results stress the importance of infection control measures on surfaces in close proximity to the head of the patient as well as in dental water lines.