Rare brain and pulmonary abscesses caused by oral pathogens started with acute gastroenteritis diagnosed by metagenome next-generation sequencing: A case report and literature review.

Odontogenic brain and pulmonary abscesses are extremely rare infectious diseases. It is mainly caused by the upward or downward transmission of local infection or blood-borne spread. In recent years, with the wide application of some novel testing methods in clinical practice, the diagnosis of unexplained infections such as odontogenic abscesses in different organs has gradually become clear. We report a case of a 21-year-old male who was healthy and had not received any oral treatment before onset. He started with acute gastroenteritis-related symptoms, then developed meningitis-related symptoms seven days later with septic shock. No obvious abscess lesions were found on head computed tomography (CT) at admission, and the etiology was not clear by routine examination, which was very easy to misdiagnose as a serious infection caused by intestinal pathogens. But odontogenic pathogens were found both in his blood and cerebrospinal fluid through metagenomic next-generation sequencing (mNGS) analysis. Subsequently, rechecked imaging examination displayed multiple brain and pulmonary abscesses. Finally, it was diagnosed as an odontogenic brain and pulmonary abscess. After an extremely lengthy anti-infection course (13 weeks of intravenous antibiotics plus 2 weeks of oral antibiotics) and surgery, the patient was improved and discharged from the hospital. From this case, we could see that the development of new diagnostic technologies such as mNGS plays an important role in the early and confirmed diagnosis of diseases previously difficult to diagnose such as odontogenic polymicrobial infections and ultimately helps to improve the prognosis of these patients.

Heavy metal enrichment characteristics in ash of municipal solid waste combustion in CO2/O2 atmosphere.

This paper investigated the behavior of six heavy metals (Cd, Pb, Cu, Cr, Ni and Zn) in the bottom ashes of recycled polyvinyl chloride pellets (PVC), wood sawdust (WS) and paper mixture (PM), representing the common components of municipal solid waste (MSW), obtained during combustion in CO2/O2 atmosphere in a lab-scale electrically heated tube furnace. Replacement of N2 by CO2 did not obviously change the shape of relative enrichment factor (RE) curves and subsequent order of heavy metals, but increased enrichment of these heavy metals in bottom ashes of WS, PM and PVC. The increment of O2 concentration in CO2/O2 atmosphere further increased RE values. It was only when the temperature was higher than or equal to 700°C that the increment of the combustion temperature reduced the RE values of heavy metals. The effect of temperature on heavy metals evaporation was the most pronounced for the medium volatile metal Pb, and the least for the low volatiles Cr and Ni. The effect of temperature was more pronounced for PVC ash than for WS and PM ashes. This paper contributes to the control of heavy metals during MSW incineration and management of MSW oxy-fuel residues.

Thermogravimetric analyses of combustion of lignocellulosic materials in N2/O2 and CO2/O2 atmospheres.

The combustion of paper, fruit waste and plant residue mixtures representing the lignocellulosic materials of municipal solid waste (MSW) in different atmospheres (80N(2)/20O(2), 70N(2)/30O(2), 60N(2)/40O(2), 50N(2)/50O(2), 80CO(2)/20O(2), 70CO(2)/30O(2), 60CO(2)/40O(2), 50CO(2)/50O(2)) was analyzed thermogravimetrically. Replacement of 80% N(2) by 80% CO(2) resulted in a slightly later ignition, a lower maximum weight loss rate and a change in reactions occurring above 600°C; however, as the oxygen concentration increased from 20% to 50% in CO(2)/O(2) atmosphere, the ignition temperature decreased from 318.5 to 310.8°C and the maximum weight loss rate increased from 20.82% to 23.57%/min. An oxygen content of 30% in the CO(2)/O(2) atmosphere achieved a similar combustion performance as a 80N(2)/20O(2). The fruit waste mixture had the least residual weight (about 5%) and the earliest ignition (about 220°C). This work contributes to the comprehensive understanding of lignocellulosic materials combustion and development of MSW oxy-fuel combustion.

Thermogravimetric analysis of the combustion of microalgae and microalgae blended with waste in N2/O2 and CO2/O2 atmospheres.

The combustion of microalgae and municipal solid waste (MSW) under N2/O2 and CO2/O2 atmospheres was analyzed using a thermogravimetric instrument. The onset temperature of volatile release (Tv), maximum rate of weight loss (Rmax) and the temperature at the maximal peak (Tmax) were measured. As the blending ratio of microalgae was increased from 10% to 70% under N2/O2 atmosphere, Tv decreased from 269.4 to 247.4 °C, Tmax decreased from 310.8 to 288.0 °C, Rmax decreased from 11.94% to 7.88% and residual weight decreased from 30% to 20%. Thus, blending with microalgae can improve MSW combustion. The type of atmosphere did not affect Tv and Tmax, but replacement of N2 by CO2, resulted in the later appearance of the small humps (>600 °C) in the mass loss and rate of weight loss curves, burnout was less complete, and Rmax was lower, thus some improvement measures, such as an increase in oxygen concentration, are required under CO2/O2 atmosphere to achieve the same combustion performances in air.