International audience

Background. Most healthcare-associated infections (HAI) develop due to a colonization of patients and healthcare workers by hospital strains of pathogens. The aim to study was to assess whether the dust within the health facilities can harbor microorganisms acting as a reservoir of HAIs.Materials and methods. Dust samples collected in the air ducts and ventilation grilles of health facilities underwent a detailed physicochemical analysis by means of scanning electron microscopy, dynamic light scattering, energy-dispersive X-ray spectroscopy, and high-temperature catalytic oxidation. Bacterial and viral diversity was investigated using an automated biochemical analyzer and polymerase chain reaction, respectively. Investigation of the microenvironment included detection of biofilms using a catalase indicator and quantification of viable microorganisms per 1 m3 air.Results. Dust from the hospital ventilation grilles and air ducts was contaminated with microorganisms in 71.13% of cases. Strikingly, multidrug-resistant and biofilm-forming strains have been found in 69.4% and 48.0% of samples, respectively. The total viable count before and after opening doors and windows was 276 and 462 colony-forming units/m3 respectively (p = 0.046). Biodiversity was represented by 21 genera of microorganisms which were consistently detected upon 6 months of follow-up. All samples contained a nanosized particulate matter. Chemical elements comprising dust were carbon (16.26–50.69%), oxygen (20.02–37.50%), nitrogen (1.59–25.03%), hydrogen (2.03–6.67%), sulfur (0.15–2.38%), calcium (0.19–7.49%), silicon (0.21–4.64%), chlorine (0.05–2.83%), sodium (0.07–1.86%), aluminum (0.36–1.78%), iron (0.08–1.61%), magnesium (0.11–1.40%), potassium (0.04–0.85%), and phosphorus (0.04–0.81%).Discussion. A wide range of multidrug-resistant strains of bacteria, detected in a hospital particulate matter with a diverse chemical composition, indicates the persistence of HAI-causing pathogens in the hospital environment.Conclusion. Dust from the ventilation grilles and adjacent air ducts should be considered as an additional reservoir of multidrug-resistant strains of bacteria in the healthcare settings.

Humanity has been facing the threat of a variety of infectious diseases. Airborne microorganisms can cause airborne infectious diseases, which spread rapidly and extensively, causing huge losses to human society on a global scale. In recent years, the detection technology for airborne microorganisms has developed rapidly; it can be roughly divided into biochemical, immune, and molecular technologies. However, these technologies still have some shortcomings; they are time-consuming and have low sensitivity and poor stability. Most of them need to be used in the ideal environment of a laboratory, which limits their applications. A biosensor is a device that converts biological signals into detectable signals. As an interdisciplinary field, biosensors have successfully introduced a variety of technologies for bio-detection. Given their fast analysis speed, high sensitivity, good portability, strong specificity, and low cost, biosensors have been widely used in environmental monitoring, medical research, food and agricultural safety, military medicine and other fields. In recent years, the performance of biosensors has greatly improved, becoming a promising technology for airborne microorganism detection. This review introduces the detection principle of biosensors from the three aspects of component identification, energy conversion principle, and signal amplification. It also summarizes its research and application in airborne microorganism detection. The new progress and future development trend of the biosensor detection of airborne microorganisms are analyzed.

Quaternary volcanic activities exert effects on microbial community compositions and structures, but the influences on typical steppes remain poorly understood. The aim of this study was to explore the influences of Quaternary volcanic activity on soil microorganisms in a typical steppe. The α-diversity results showed that the disturbance scope of volcanism is limited; once a certain distance from a volcano is reached, volcanism no longer affects soil microorganisms. Compared to bacterial communities, soil fungal communities seem to exhibit a stronger anti-interference ability under conditions of volcanic perturbation. A total of seven keystone taxa were identified by using analyses of co-occurrence networks and included six bacteria and one fungus, which suggested that soil bacteria may play a more significant role in the overall community structure and function than soil fungi. Compared to volcanic areas, typical steppes were enriched with more core soil microorganisms and had more highly modular networks (modularity: 0.296 vs 0.626), simpler community correlations (links: 369 vs 269) and stronger competitive relationships (positive/negative link ratio: 3.06 vs 1.89) among soil microbial communities. However, the volcanic area was enriched with arbuscular mycorrhizal fungi and showed improved bacterial metabolism. Multivariate regression tree (MRT) analyses indicated that the key potential drivers in volcanic areas and typical steppes were soil available phosphorus (AP) contents and C/N ratios, respectively. Structural equation models (SEMs) indicated that the same keystone taxa in different ecological environments are able to assume different functions, and that the causal relationships between the same keystone taxa and different environmental variables also differ. These results may provide crucial implications for understanding the effects of volcanic activity on the ecosystems of typical steppes.

Bisphenol-A (BPA) is a constituent of polycarbonate plastics and epoxy resins, widely applied on food packaging materials. As BPA exposure results in health hazards, its efficient removal is of crucial importance. In our study five potentially probiotic microorganisms, namely Lactococcus lactis, Bacillus subtilis, Lactobacillus plantarum, Enterococcus faecalis, and Saccharomyces cerevisiae, were tested for their toxicity tolerance to BPA and their BPA removal ability. Although BPA toxicity, evident on all microorganisms, presented a correlation to both BPA addition time and its concentration, all strains exhibited BPA-removal ability with increased removal rate between 0 and 24 h of incubation. BPA degradation resulted in the formation of two dimer products in cells while the compounds Hydroquinone (HQ), 4-Hydroxyacetophenone (HAP), 4-Hydroxybenzoic acid (HBA) and 4-Isopropenylphenol (PP) were identified in the culture medium. In the proposed BPA degradation pathways BPA adducts formation appears as a common pattern, while BPA decomposition as well as the formation, and the levels of its end products present differences among microorganisms. The BPA degradation ability of the tested beneficial microorganisms demonstrates their potential application in the bioremediation of BPA contaminated foods and feeds and provides a means to suppress the adverse effects of BPA on human and animal health.

An intensive study, applied to a site characterized by multiple sources of microorganisms, was aimed at understanding the best approach to study bioaerosol. Culture-based, molecular biological, and chemical methods were applied to Particulate Matter (PM) samples collected in a livestock facility, during spring and autumn seasons, in two different outdoor areas. The first one was close to a place where feed was stored and handled and the second next to an open cowshed. Qualitative analysis of bacteria was performed by sequencing techniques applied to DNA extracted from both isolated culturable bacteria and particulate matter samples. Quantification of microorganisms was achieved through three distinct approaches. Microorganism colonies were counted, after incubation at 28 °C, and expressed as colony-forming units (CFU) per m³. Chemical method consisted in the identification of individual biomarkers, and their conversion to number of microorganisms per m³, using proper conversion factors. Finally, qPCR was applied to DNA extracted from PM samples, and the results were expressed as total amount of bacteria present in the bioaerosol (UG/m³). The presence of airborne sterols was also studied to broaden the knowledge of bioaerosol components in atmosphere. Small seasonal differences and major sampling site differences occurred. Obviously, culture-dependent method identified less and different bacteria, than culture-independent approach. The chemical approach and the culture independent metagenomic method were in good agreement. As expected, CFU/m³ accounted for not more than 0.3% of bacteria calculated as the average of chemical and culture independent metagenomic methods. The complexity of the obtained results shows that the different approaches are complementary to obtain an exhaustive description of bioaresol in terms of concentration, speciation, viability, pathogenicity.

Doctoral

Pathogenic microorganisms in water pose a great risk to human health.Therefore, it is necessary to find an efficient, environmentally friendly, and economicallyacceptable solution for their removal from polluted and wastewater. This paper presentsthe efficiency of a biological system with floating islands in the removal of pathogenicmicroorganisms from the water of a polluted urban river. The modified floating treatmentwetland consisted of a collection tank, 4 calls with floating islands and 1 cell with algae,which enabled additional water polishing. The results of the research showed that thebiological system constructed on the bank of this river had a high efficiency in reducing thenumber of various groups of pathogenic microorganisms. Within the cells with the floatingislands, 100% efficiency in the removal of coliform bacteria of faecal origin was achieved,and the reduction of pathogens was continued within the cell with algae. The realisedefficiency of removal of total coliform bacteria was 100% in all cells, except in the cell 4with decorative aquatic macrophytes, in which the efficiency was 97%. The number ofintestinal enterococci was reduced in the range of 92 to 97% in cells with plants, and up to98% in the cells with algae. The floating islands and algae also enabled a high reduction inthe number of aerobic heterotrophs and facultative oligotrophs. In addition, the ratio ofthese microorganisms had a value above 1 during the entire period of water treatment,which indicated that natural processes of self-purification of polluted water ran smoothly in the floating treatment wetland. Due to the reduction of pathogenic microorganisms, waterthat belonged to class V, i.e., III, after the discharge from the biological system, had thecharacteristics of water with excellent ecological status (class I)

There are a large number of active cold-adapted microorganisms in the perennial cold environment. Due to their high-efficiency and energy-saving catalytic properties, cold-adapted microorganisms have become valuable natural resources with potential in various biological fields. In this study, a series of cold response strategies for microorganisms were summarized. This mainly involves the regulation of cell membrane fluidity, synthesis of cold adaptation proteins, regulators and metabolic changes, energy supply, and reactive oxygen species. Also, the potential of biocatalysts produced by cold-adapted microorganisms including cold-active enzymes, ice-binding proteins, polyhydroxyalkanoates, and surfactants was introduced, which provided a guidance for expanding its application values. Overall, new insights were obtained on response strategies of microorganisms to cold environments in this review. This will deepen the understanding of the cold tolerance mechanism of cold-adapted microorganisms, thus promoting the establishment and application of low-temperature biotechnology.

Reducing fuel cells electrical losses is achieved by the use of a catalyst. Being inexpensive and renewable, biocathodes have an advantage over synthetic and chemical ones. Here the microbial fuel cell (MFC)-utilizing biocathode based on the acidophilic chemolythotrophic microorganisms (ACM) mixed culture has been studied. The Leptospirillum sp., Acidithiobacillus sp., Ferroplasma sp. consortium has been used as a cathode biocatalyst. Pyrite enrichment tails of a mining and processing enterprise served as the catholyte substrates. It is experimentally demonstrated that ACM mixed culture Leptospirillum sp., Acidithiobacillus sp., Ferroplasma sp. introduced into the catholyte leads to MFC electrical characteristics increase by approximately two times. With the selected external load (30 Ω) Cathodic bioagents increased the MFC electric power four-fold (from 137 to 579 µW). Catholyte redox potential increased from 431 to 581 mV during 11 d in the presence of acidophilic iron-oxidizing microorganisms. At 33 d, this value increased up to 695 mV. This is an indirect evidence for active processes of iron oxidation. The analysis results for the Fe³⁺ content in the medium also support this assumption. Thus, in a course of a 33-d experiment Fe³⁺ concentration increased from 0 to 1.5 g/l. The redox processes intensification in the studied systems also confirmed by the cyclic voltammetry (CV). Under pyrite utilization conditions in the presence of ACM mixed culture cyclic voltammograms show an increase in the reduction current at the cathodic potentials region. The results obtained herein suggest that the studied biochemical system is a perspective catholyte for MFC capable to reduce a cathodic overpotential.