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PubMed2005

Atmospheric nitrogen inputs to the Delaware Inland Bays: the role of ammonia.

A previous assessment of nitrogen loading to the Delaware Inland Bays indicates that atmospheric deposition provides 15-25% of the total, annual N input to these estuaries. A large and increasing fraction of the atmospheric wet flux is NH(4)(+), which for most aquatic organisms represents the most readily assimilated form of this nutrient. Particularly noteworthy is a 60% increase in the precipitation NH(4)(+) concentration at Lewes, DE over the past 20 years, which parallels the increase in poultry production on the Delmarva Peninsula over this period (currently standing at nearly 585 million birds annually). To further examine the relationship between local NH(3) emissions and deposition, biweekly-integrated gaseous NH(3) concentrations were determined using Ogawa passive samplers deployed at 13 sampling sites throughout the Inland Bays watershed over a one-year period. Annual mean concentrations at the 13 sites ranged from <0.5 microg NH(3)m(-3) to >6 microg NH(3)m(-3), with a mean of 1.6+/-1.0 microg NH(3)m(-3). At most sites, highest NH(3) concentrations were evident during spring and summer, when fertilizer application and poultry house ventilation rates are greatest, and seasonally elevated temperatures induce increased rates of microbial activity and volatilization from soils and animal wastes. The observed north-to-south concentration gradient across the watershed is consistent with the spatial distribution of poultry houses, as revealed by a GIS analysis of aerial photographs. Based on the average measured NH(3) concentration and published NH(3) deposition rates to water surfaces (5-8 mm s(-1)), the direct atmospheric deposition of gaseous NH(3) to the Inland Bays is 3.0-4.8 kg ha(-1)yr(-1). This input, not accounted for in previous assessments of atmospheric loading to the Inland Bays, would effectively double the estimated direct dry deposition rate, and is on par with the NO(3)(-) and NH(4)(+) wet fluxes. A second component of this study examined spatial differences in NO(3)(-) and NH(4)(+) wet deposition within the Inland Bays watershed. In a pilot study, precipitation composition at the Lewes NADP-AIRMoN site (DE 02) was compared with that at a satellite site established at Riverdale on the Indian River Estuary, approximately 21 km southwest. While the volume-weighted mean precipitation NO(3)(-) concentrations did not differ significantly between sites, the NH(4)(+) concentration observed at Riverdale (26.3 micromoles L(-1)) was 73% greater than at Lewes (15.2 micromoles L(-1)). More recently, a NADP site was established at Trap Pond, DE (DE 99), which was intentionally located within the region of intense poultry production. A comparison of the initial two years (6/2001-5/2003) of precipitation chemistry data from Trap Pond with other nearby NADP-AIRMoN sites (Lewes and Smith Island) reveals fairly homogeneous NO(3)(-) wet deposition, but significant spatial differences ( approximately 60%) in the NH(4)(+) wet flux. Overall, these results suggest that local emissions and below-cloud scavenging provide a significant contribution to regional atmospheric N deposition.

Air Pollutants↗

PubMed1999

[Monitoring of microbial contamination of stick wound in swine carcasses].

This study was done to evaluate the microbial contamination by Salmonella spp., Escherichia coli, fecal coliforms, and total aerobic count of the stick wound of swine carcasses. The effectiveness of trimming the stick wound in the 2 Québec slaughterhouses visited was evaluated. A bacteriological analysis was done on 276 stick wounds. Results indicated that, before trimming, 0.9% stick wounds were contaminated by Salmonella spp. Contamination by coliforms was observed in 40.6% of samples, and 27.7% were positive for E. coli. After trimming the stick wounds, 1.1% were contaminated by Salmonella spp., 34.1% were contaminated by coliforms, and 26.2% were positive for E. coli. The results showed that trimming contributes to reducing significantly the bacterial total count at the site and that the bacterial load at this site was less important than that found on the brisket.

Abattoirs↗

PubMed2003

Comparative bioavailability of selenium to aquatic organisms after biological treatment of agricultural drainage water.

Selenium (Se) is naturally abundant in the soils of the western San Joaquin Valley, California, USA. Intense agricultural activity in this region requires irrigation which leaches Se into surface waters draining to the San Joaquin River. Se water contamination and subsequent accumulation in wildlife is a serious problem in the Central Valley of California, and the subject of increasingly intensive regulatory action. Algal-bacterial selenium reduction (ABSR) is a potential new treatment approach to reduce Se in agricultural drainage, and an ABSR demonstration facility was examined with respect to its Se removal efficiency and effect on Se bioavailability and bioaccumulation. Water samples were taken to study treatment effects on Se speciation. Invertebrate tissue Se concentrations in the ABSR ponds were monitored for 2 years. Laboratory-based algal bioaccumulation tests and in situ microcosms with a variety of invertebrates were also used to address differences in Se bioavailability before and after ABSR treatment. The ABSR system removed about 80% of the total influent Se; however, microbial and algal activity produced selenite and organic Se, the combined concentration of which increased 8-fold during treatment. As a result of the greater bioavailability of selenite and organic Se, relative to the selenate of the influent, treatment contributed to greater Se concentrations in effluent-exposed organisms. ABSR-treated water produced Se concentrations in biota 2-4 times greater than organisms exposed to untreated water. The bioavailability of Se in the treated water was 2-10 times greater than Se in the influent. The shift to more bioavailable Se forms due to biological treatment is inherent in system design, and makes it difficult to weigh the ecological benefits of a reduction in total Se loadings from a regional perspective against the greater toxicological risk to biota in the vicinity of the effluent.

Animals↗

PubMed1997

Clinical application of gastric histology to monitor treatment of dual therapy in H. pylori eradication.

This preliminary study attempted to test whether pretreatment gastric histology of H. pylori infection may affect the success of dual therapy and to identify which parameter of gastric histology could be improved after dual therapy. One hundred forty-five dyspeptic patients with H. pylori infection received a two-week course of dual therapy (Amoxicillin 500 mg every 6 hr plus omeprazole 20 mg twice a day). In each patient, three pairs of gastric biopsies, sampled from the antrum, lower body, and upper body near the cardia, were collected before treatment and four weeks after completion of dual therapy. The density of H. pylori (score 1-5) and parameters of the modified Sydney system were applied to test the severity of H. pylori-related gastric histology in each specimen. The total bacterial load (score 1-15) was a sum of the density of H. pylori sampled from three biopsies. The overall rate of H. pylori eradication rate by dual therapy is 73.1% (106/145). Univariate analysis of parameters in pretreatment histology disclosed that the presence of mucosal atrophy (P < 0.01), lymphoid follicles (P < 0.005), and higher-density H. pylori (P < 0.001) predisposed to dual therapy failure. Multivariate analysis by stepwise logistic regression further confirmed that both the density of bacteria and the presence of lymphoid follicles are the two major factors related to the outcome of dual therapy (P < 0.001). Four weeks after dual therapy was completed, only patients with successful eradication significantly improved in these gastric histology parameters: acute activity, chronic inflammation, eosinophil infiltration, and mucosal atrophy. However, the lymphoid follicle and intestinal metaplasia were not significantly improved during the study period. The eradication rates among three subgroups with different total bacterial loads (group I: 1-5; II: 6-10; III: 11-15) disclosed a downward trend (I: 89.1%; II: 73%; III: 52.7%). It is concluded that dual therapy could improve gastric histology especially among patients with successful eradication of H. pylori. Evaluating pretreatment histologic parameters, including the density of H. pylori and the presence of lymphoid follicles, is valuable in predicting the success of dual therapy.

Amoxicillin↗

PubMed2001

Carbon and nitrogen removal from a wastewater of an industrial dairy laboratory with a coupled anaerobic filter-sequencing batch reactor system.

A set of two reactors, an Anaerobic Filter (AF) of 12 m3 and a Sequencing Batch Reactor (SBR) of 28 m3, coupled in series, were used to treat the wastewaters from an industrial milk analysis laboratory. The characteristics of these effluents are similar to those discharged by dairy factories (average values around 10 kg COD/m3 and 0.20 kg N/m3). These wastewaters were produced as the result of the final mixture of the analysed milk samples, with a very high organic load, and other low strength effluents, such as sewage and other minor liquid streams generated in the laboratory. Two microbial growth inhibitors, sodium azide and chloramphenicol, were systematically added to the milk before its analysis. Preliminary results have shown that these compounds did apparently not inhibit the methanogenic activity of the anaerobic sludge. Toxicity determination, using the Microtox method, resulted in EC50 values for the wastewaters of 20 g/L, whereas the final effluent from the SBR was non toxic. A maximum OLR of 8 kg COD/m3.d was treated in the AF, being the maximum OLR in the SBR around 1.5-2 kg COD/m3.d. During operation, the soluble COD of the final effluent from the SBR was usually below 200 mg/L, and total nitrogen (mainly nitrate) below 10 mg N/L. Assimilation of nitrogen for growth and nitrification-denitrification were the main mechanisms of nitrogen removal from the wastewater. In the anaerobic system between 50-85% of the organic matter was converted into methane, being the remaining COD and most of the nitrogen removed in the suspended culture system. Overall COD removal in the treatment system was 98% and the nitrogen removal up to 99%. The combination of the AF and the SBR was advantageous resulting in a lower energy consumption and sludge generation in the treatment system.

Anaerobiosis↗

PubMed2006

Potential of the marine sponge Hymeniacidon perleve as a bioremediator of pathogenic bacteria in integrated aquaculture ecosystems.

The aim of this article is to investigate the potential of using sponges as a bioremediator to remove pathogenic bacteria in integrated aquaculture ecosystems. Using the inter-tidal marine sponge Hymeniacidon perleve as a model system, the ability of removing the most common pathogens Escherichia coli and Vibrio anguillarum II in aquaculture waters was screened in laboratory tests. In sterilized natural seawater (SNSW) supplemented with E. coli at (7.0-8.3) x 10(6) cells/mL, H. perleve can remove an average 96% of E.coli within 10.5 h at a filter rate of ca. (7.53-8.03) x 10(7) cells/h x g of fresh sponge in two independent tests. Despite the removal efficiency and filter rate are similar; the clearance rates (CR) vary significantly among individual sponge specimens and between two batches. For the tests on V. anguillarum II in SNSW, about 1.5 g fresh sponges can keep the pathogen growth under control at a lower initial density 3.6 x 10(4) cells/mL of 200 mL water volume. Further tests were done for 24 h using about 12 g fresh sponge in 2-L actual seawater collected from two aquaculture sites that have ca. eightfold difference in pathogenic bacteria load. The concentrations of E. coli, Vibrio, and total bacteria at 24 h in treatment groups were markedly lower, at about 0.9%, 6.2%-34.5%, and 13.7%-22.5%, respectively, of those in the control. Using a fluoresce stain 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate, E. coli, and V. anguillarum II cells were stained and fed to sponges in two independent tests. The confocal microscope observation confirmed that the sponges filtering-retained and digested these bacteria by phagocytosis.

Animals↗

PubMed1996

The influence of Pseudomonas aeruginosa on liposomes.

The interaction of liposomes loaded with Ponceau red (used as a marker) with Pseudomonas aeruginosa cells was observed and it resulted in marker leakage. The marker leakage from liposomes was low in physiological fluids. The interaction was independent of secreted phospholipase C level and the serotype of the tested strain. Six of 37 examined isolates did not cause any release of the marker from the liposomes. Marker release of over 50% of total encapsulated material was observed only for ten of the strains tested.

Anti-Bacterial Agents↗

PubMed2000

HIV-1 genotypic zidovudine drug resistance and the risk of maternal--infant transmission in the women and infants transmission study. The Women and Infants Transmission Study Group.

OBJECTIVES: Although the treatment of pregnant women and their infants with zidovudine (ZDV) has been remarkably effective in preventing the perinatal transmission of human HIV-1, many potentially preventable infections still occur. To examine whether the risk of perinatal infection is increased among women who carry ZDV-resistant HIV-1, the role of genotypic ZDV resistance in perinatal transmission was evaluated. METHODS: The reverse transcriptase (RT) region of clinical isolates from culture supernatants of 142 HIV-1-infected women enrolled in the Women and Infants Transmission Study (WITS), who had been treated with ZDV during pregnancy was sequenced. Results from genotypic sequencing were linked to demographic, laboratory, and obstetrical databases, and the magnitude of association of having consensus drug-resistant HIV-1 RT mutations with transmission was estimated. RESULTS: Twenty-five per cent (34/142) of maternal isolates had at least one ZDV-associated resistance mutation. A lower CD4 cell percentage and count (P= 0.0001) and higher plasma HIV-1 RNA (P=0.006) were associated with having any ZDV resistance mutation at delivery. Having any RT resistance mutation [odds ratio (OR): 5.16; 95% confidence interval (CI): 1.40, 18.97; P=0 0.01], duration of ruptured membranes [OR: 1.13 (1.02, 1.26) per 4 h duration; P= 0.02], and total lymphocyte count [OR: 1.06 (1.01, 1.10) per 50 cells higher level; P=0.009] were independently associated with transmission in multivariate analysis. CONCLUSION: Maternal ZDV resistant virus was predictive of transmission, independent of viral load, in these mothers with moderately advanced HIV-1 disease, many of whom had been treated with ZDV before pregnancy.

Anti-HIV Agents↗

PubMed2005

Diffuse and point pollution impacts on the pathogen indicator organism level in the Geum River, Korea.

The pathogens originating from diffuse pollution have raised much concern recently. In many countries, pathogen levels are monitored in surface water by measuring the pathogen indicator organism level, which indicates the concentration of pathogen associated microorganisms to determine contamination. Among indicator organisms, total coliform, fecal coliform, and Escherichia coli were selected for study, and their concentration as well as their flow rate were monitored at monitoring stations from October, 2001 to April, 2003. Monitoring stations include six sampling stations in the Geum River, two small watersheds used for forestry and agricultural land, one large wastewater treatment plant, one separate sewer overflow site, and one separate sewer overflow site in the Geum River basin. The coliform concentration of the combined sewer overflow was the highest, followed by the runoff from agricultural land use, the separate sewer overflow, and the runoff from forestry land use. The Pearson correlation coefficient for flow rate against total coliform concentration was 0.71 and was significant at 0.01 level, while the Pearson coefficient for other water quality constituents showed weak correlation (-0.36 to +0.37) against flow rate. Coliform concentration showed higher correlation against suspended solid concentration or flow rate during storm flow condition than during low flow condition. Two different relationship lines could explain the relationships between the flow rate and coliform loadings. Load duration curve technique was presented to assess the relative contributions of diffuse and point source pollution to the pathogen level at monitoring sites in the Geum River.

Colony Count, Microbial↗

PubMed2003

Methylmercury in rivers draining cultivated watersheds.

Total mercury (THg) concentrations in streams draining cultivated watersheds in Minnesota, USA are strongly correlated with total suspended sediment (TSS) concentrations, varying widely in response to precipitation-driven inputs of soil-derived suspended sediments. Methylmercury (MeHg) concentrations in these waterways have not been studied, and little is known about mercury uptake mechanisms in resident fish populations. To begin to identify factors influencing MeHg concentrations and loadings in these streams, we measured THg and MeHg concentrations in unfiltered whole water samples from the Minnesota River and two of its major tributaries, the Blue Earth and Le Sueur Rivers. Land use in the watersheds of these rivers is over 90% row-crop agriculture, and extensive artificial drainage systems deliver runoff and associated solids quickly to local streams and rivers. THg concentrations were elevated (>10 ng/l) during much of Spring 2000 and part of the summer when runoff from precipitation events increased stream discharge and carried soil materials into the streams. Reduced precipitation resulted in low flow conditions from August through October, and THg concentrations decreased to <4.0 ng/l in all three rivers. MeHg concentrations in the Le Sueur River ranged from 0.07 to 0.42 ng/l between June and December. Higher MeHg concentrations (>0.2 ng/l) were measured during summer months when THg and TSS concentrations were high after precipitation events. Elevated MeHg concentrations were also observed in late October after leaf litter inputs. Conditions on the Blue Earth River were different, with elevated MeHg concentrations (>0.5 ng/l) observed during low flow in August and September. These higher concentrations coincided with a period of enhanced microbial growth stimulated by high late-summer temperatures. A late-October increase in MeHg concentration attributed to leaf litter inputs was also observed in this river. MeHg concentration trends in the Minnesota River were similar to those in the Blue Earth River. Indicators of biological productivity (chlorophyll a, volatile suspended solids, and total Kjeldahl nitrogen) were higher in the Blue Earth and Minnesota Rivers compared to the Le Sueur River, which may signal a connection between higher biological activity and increased MeHg concentrations.

Agriculture↗

PubMed2006

Role of biological activity and biomass distribution in air biofilter performance.

The effects of temporal and spatial changes in biological activity and biomass amount on biofilter performance were investigated in a lab-scale trickle-bed air biofilter at a toluene loading of 46.9gm(-3)h(-1) under two different experimental strategies, namely, periodic backwashing at a rate of 1h once a week and 2d starvation. Analysis of the overall reaction for toluene metabolism revealed that cell synthesis was relatively favored over toluene oxidation in the inlet section of the biofilter, but over time its oxidation became favored throughout the biofilter bed. Periodic in situ backwashing with media fluidization effectively made even spatial distribution of biomass along the bed media, by which consistent high removal performance in the biofilter has been attained. After 2d starvation, the ratio of the biofilm EPS to the total biomass increased along the media bed depth, while the total biomass in the media bed subsequently decreased. The presence of sufficient biomass and microbial activity favorably influenced biofilter reacclimation after restart-up following starvation.

Air Pollution↗

PubMed2003

Potential for broad applications of flow cytometry and fluorescence techniques in microbiological and somatic cell analyses of milk.

Monitoring the quality and safety of milk requires careful analysis of microbial and somatic cell loading. Our aim was to demonstrate proof of the principle that flow cytometry (FCM), coupled with fluorescence techniques for distinguishing between cell types, could potentially be employed in a wide variety of biological assays relevant to the dairy industry. To this end, we studied raw milk samples and ultraheat-treated milk, into which known numbers of bacteria or mouse cells were inoculated. For bacterial analyses, protein and lipids were removed, whereas only centrifugal lipid clearing was needed for somatic cell analyses. Cleared samples were stained with fluorescent dyes or with bacterial-specific fluorescent-labeled oligonucleotides and analyzed by FCM. A fluoresceinated peptide nucleic acid probe enabled efficient enumeration of bacteria in milk. Dual staining of samples with fluorescent dyes that indicate live (5-cyanol-2,3-ditolyl tetrazolium chloride, CTC or SYTO 9) or damaged cells (oxonol or propidium iodide, PI) enabled determination of viable bacteria in milk. Gram-positive and -negative bacteria were distinguished using hexidium iodide and SYTO 13 in dual staining of cleared milk samples. An FCM-based method gave a good correlation (r=0.88) with total microscopic counts of somatic cells in raw milk. The FCM method also correlated strongly (r=0.98) with the standard Fossomatic method for somatic cell detection. We conclude that FCM, coupled with fluorescence staining techniques, offers potentially diverse and rapid approaches to biological safety and quality testing in the dairy industry. Potential application of flow cytometers to a broad range of assays for milk biological quality should make this instrumentation more attractive and cost effective to the dairy industry and indeed the broader food industry.

Animals↗

PubMed2006

Salmonella prevalence and total microbial and spore populations in spices imported to Japan.

A total of 259 samples of 40 types of spices were tested for Salmonella prevalence and total microbial and spore populations. Salmonella enterica serotypes Weltevreden and Senftenberg were isolated from a black- and red-pepper sample, respectively. Because Salmonella was not detected by the most-probable-number method, it indicated that at least one cell of the microorganism was present in 25 g of sample. The mean aerobic bacterial count was greater than 5.39 log CFU/g in turmeric, garam masala, curry powder, and paprika. The mean bacterial spore counts were greater than 4.33 log CFU/g in turmeric and curry powder. The mean aerobic bacterial count in the two Salmonella-isolated samples was 6.93 log CFU/g. These results indicate that spices can be a source of contamination in the products where they are used as ingredients, and methods to reduce the microbial load in spices should be used.

Bacteria, Aerobic↗

PubMed2001

Accumulation of organic matter fractions in a gravel-bed constructed wetland.

The function of a gravel-bed wetland in treating wastewaters is dependent on the turn-over rate of organic matter (OM) fractions in accumulated solids. Organic deposits from a gravel-bed planted (Schoenoplectus tabernaemontani) wetland, which had experienced pore clogging after 5 years of receiving farm dairy wastewater were therefore collected and determined for labile (water-soluble) and stable (humic acid, fulvic acid and humin) OM fractions, total carbon (C), microbial biomass and microbial respiration rate. Over 90% of the accumulated organic solids was present as stable fractions, with humic compounds at least 2-fold higher in surface deposits and the top 100 mm of the gravel bed than the lower gravel substratum. Clogging of the gravel pore spaces over a 5-year wetland operation was probably due to the accumulation of refractory (stable) organic solids, particularly in the top 100 mm of the gravel bed. Microbial respiration rate and microbial biomass were significantly correlated with stable OM fractions, suggesting that these microbial parameters may be used to predict the nature of accumulated OM fractions. Further research is required to evaluate the use of these parameters as indicators of labile and stable fractions in wetlands with a range of OM loadings and accumulation.

Agriculture↗

PubMed2005

Determination of total aerobic and indicator bacteria on some raw eaten vegetables from wholesalers in Ankara, Turkey.

The aim of this study was to investigate the bacteriological quality of some raw eaten salad vegetables obtained from wholesalers in Ankara, Turkey. A total of 180 samples including lettuces, cos lettuce, iceberg lettuce, parsley, dill and carrots were analyzed for total aerobic bacteria, total coliform bacteria and E. coli between January 2004 and April 2004. Compact Dry media (Nissui Pharmaceutical Co. Ltd., Japan) were used for bacteriological analysis. Outer leaves of lettuce, cos lettuce and iceberg-lettuce samples had higher bacterial loads (3.3-7.4 log(10)CFU(-1)) than inner leaves. Neither total aerobic and coliform bacteria nor E .coli were isolated from seven inner leaves (two cos and five iceberg-lettuce samples). E. coli was significantly more often detected on parsley (21/30) and dill samples (12/30) (p<0.05). Consequently, we showed that fresh salad vegetables (especially parsley, dill and cos lettuce) might contain pathogenic microorganisms and represent a risk for consumers regarding foodborne disease. The importance of adequate measures throughout the farm-to-table food chain was emphasized.

Colony Count, Microbial↗

PubMed2004

Rapid enumeration of virus-like particles in drinking water samples using SYBR green I-staining.

We studied the suitability of SYBR green I-staining for determining total counts of virus-like particles and bacteria in drinking water. Low background fluorescence and lack of unspecific staining made drinking water samples an excellent matrix for SYBR green I-staining. Direct microscopic count method is a rapid and economical tool for assessing the total number of virus-like particles in aquatic samples, compared to culture-dependent or molecular biology methods. We applied this method to show the efficiency of a large-scale drinking water purification process in the removal of virus-like particles and bacteria from lake water.

Benzothiazoles↗

PubMed1991

Determination of totalcoliform and faecalcoliform bacteria from bathing water with FLUOROCULT-BRILA-broth.

The BRILA-MUG one-tube-test in connection with the MPN-method can be used successfully to determine with sufficient reliability the number of indices of total coliforms and faecal coliforms according to the EC-Directive for bathing waters. Using the one-tube-test and determination of gas production, fluorescence and indole production is, from the hygienic point of view for surface waters, equal in value to subculture and biochemical identification. The test needs only a minimum of material and laboratory staff. Differences between this test and other more extensive tests with several biochemical identification steps are negligible. The work load for bathing water monitoring would not be justified in this case. Due to the occurrence of Aeromonas, the values for total coliforms compared to a determination with biochemical identification are higher in some cases. A high contamination with Aeromonas indicates a high polluted surface water with a high degree of eutrophication. This is an important additional criterion for the evaluation of bathing waters, even when a direct dependence on faecal contamination does not exist in every case. The degree of an up-to-date faecal contamination can be estimated by the pollution with faecal coliforms.

Aeromonas↗

PubMed2026

Association Between the Root Canal Microbiome and Apical Lesion Size: An Observational Shotgun Metagenomic Study.

AIM: The aim was to characterize the taxonomic and functional composition of the microbiome involved in primary endodontic infections and to evaluate their association with the periapical lesion size using shotgun metagenomic sequencing. METHODOLOGY: Samples from primary root canal infections diagnosed with apical periodontitis were analysed with shotgun sequencing. Samples were classified according to the lesion size as small (< 3 mm) or large (> 7 mm). The bacterial DNA copies in each group were quantified by qPCR. Taxonomic and functional annotations were made using Bracken/Kraken2 and HUMAnN3 software. Species richness, Shannon, Simpson and Pielou indices were used to measure alpha diversity. The similarity of the bacterial communities between study groups was evaluated by Principal Coordinate Analysis based on Bray-Curtis distances. The ALDEx2 package was used to infer the differences between species, and the edgeR package for KEGG pathways. For all statistical analyses, p < 0.05 was considered as significant. RESULTS: A total of 49 samples were analysed, 27 with small lesions and 22 with large lesions. Species richness and Shannon indices showed differences between both groups, whereas no differences were seen according to Simpson and Pielou indices. A different community composition (PERMANOVA, p = 0.0019) was observed between the two groups. Three species were significantly enriched in the large lesion samples, Filifactor alocis, Lachnospiraceae bacterium oral taxon 500 and Olsenella uli, while three others were enriched in small lesion samples, Acinetobacter baumannii, Acinetobacter pittii and Cutibacterium acnes. Functionally, benzoate, flavonoid and steroid degradation, the sphingolipid signalling pathway and proteasome function were enriched in samples with large lesions. Monoterpenoid biosynthesis, phospholipase D signalling, the sulphur relay system and staurosporine biosynthesis were enriched in small lesions. CONCLUSIONS: Teeth with large periapical lesions harbour greater bacterial loads and exhibit a more diverse microbial community than those with small lesions. Differences in species-level taxonomic composition were observed between both groups. Functionally, large lesions are enriched in pathways associated with immune evasion and pro-inflammatory activity, whereas small lesions are characterized by pathways related to apoptosis, metabolic adaptation and anti-inflammatory processes. These findings suggest that lesion severity is also shaped by the functional potential of the microbiome to modulate host inflammation.

Humans↗