Development of a portable real-time PCR system for on-site detection of airborne bacteria

This study thoroughly examined indoor air quality in six chain stores in Isfahan, Iran and involved the measurement of air pollutants (PM2.5, PM10, NO2, SO2, CO2, bacteria and fungi), alongside noise levels and thermal comfort over four seasons (2023-2024). To address the diversity of pollutants and enhance decision-making, an indoor air quality index (IAQI) was proposed, based on the importance coefficient and pollutant duration of presence. The results revealed that concentration of PMs in the autumn was relatively higher than in other seasons, with a strong correlation (R2 = 0.926) observed between PM2.5 and PM10. For other parameters, levels remained within acceptable limits; however, noise levels in all seasons and stores exceeded standards. Airborne bacteria (312-1,007 CFU/m³), dominated by Rhodococcus and Micrococcus, and airborne fungi (639-1,332 CFU/m³), mainly represented by Aspergillus and Penicillium, were detected. Overall, most stores exhibited intermediate biological contamination levels across all seasons. The proposed IAQI for all seasons and stores, with some allowance for variability, falls into class D, corresponding to an intermediate/acceptable indoor air quality level. In conclusion, the air quality in studied stores does not pose an immediate concern for customers and visitors, continuous monitoring and the implementation of ventilation equipment are recommended to ensure the well-being of store personnel.

Simultaneous real-time estimation of airborne bacterial and fungal concentrations for indoor bioaerosol exposure surveillance via adenosine triphosphate (ATP) bioluminescence.

Indoor airborne microorganisms and particulate matter (PM) are associated with respiratory infections and non-communicable diseases, posing a significant public health concern. This study evaluated the effectiveness of non-thermal plasma (NTP) for air disinfection and PM removal under real-world conditions. Chamber experiments were conducted using air artificially contaminated with PM, and reduction rates were compared between NTP and control groups. Field investigations were performed in an unoccupied classroom and a clinic during normal operation, and airborne bacterial concentrations, PM levels, and influence of human activities and environmental factors were evaluated. The results showed that a 30-min NTP treatment reduced approximately 90% of PM2.5 concentration in the chamber, after adjustment for natural decay. Under unoccupied conditions, airborne bacterial concentrations were significantly decreased after 90min of NTP disinfection, when compared with no treatment. Under occupied conditions, although human activities increased bacterial and PM levels, both indicators declined with prolonged disinfection duration. The highest bacterial load occurred in the 1.1-2.1-µm particle-size fraction. Thus, controlling the number of occupants and minimizing unnecessary door opening during clinical procedures may enhance disinfection efficiency. Overall, NTP effectively inactivated airborne bacteria and removed PM, showing promising potential for improving indoor air quality and reducing airborne disease transmission risks.

Natural antimicrobial composite membranes for effective filtration and inactivation of airborne bacteria and viruses.

An automated air-conditioner cleaning system was developed as a retrofit solution for conventional split-type units to reduce residual moisture in the evaporator section and suppress post-shutdown microbial accumulation. The system was integrated with an 18,000 BTU h−1 air-conditioner and implemented using an Arduino-based closed-loop control platform with temperature and relative humidity monitoring. After shutdown, the indoor fan was operated under low-, medium-, or high-speed conditions to remove retained moisture from the cooling coil. System performance was evaluated in an 18 m3 test room through measurements of electrical consumption, operating cost, relative humidity, and microbial contamination in room air and on the evaporator coil before and after system installation. Low-speed operation showed the lowest current demand, power consumption, and electricity cost, with corresponding values of 0.36 ± 0.01 A, 79.2 ± 0.8 W, and 0.47 THB per 150 min. Post-shutdown humidity reduction was achieved under all tested conditions, while the high-speed mode provided the fastest drying response, reducing relative humidity to approximately 60% within 120 min. In the room air, the greatest reduction in airborne fungi after shutdown was observed at low speed, whereas the greatest reduction in airborne bacteria was observed at medium speed. On the evaporator coil, the strongest bacterial suppression was obtained at low speed, where the bacterial count after 24 h decreased from 633.33 ± 34.27 CFUs before installation to below the detection limit after installation. These results indicate that the proposed system reduced moisture retention and microbial contamination with minimal energy consumption.

Proteomics-decoded capture kill mechanism of CuAgOx/UiO-66-NH2 for dark inactivation of pathogenic bacteria.

Next-generation biosensors for detecting bioaerosols: Challenges, innovations, and applications.

Engineered biopolymer-ZIF-8 composites for bacterial aerosols sampling and detection.

Asymmetric Fe3 +/Fe3⁻δ interfaces engineering in MOFs via boronic acid ligand substitution for targeted bioaerosol capture and inactivation.

Indoor microbial exposures influence respiratory health, yet how men and women respond differently to airborne bacterial communities remains unclear. This study aimed to assess sex-specific associations between indoor airborne bacteria, and lung function, and airway inflammation in adults. Airborne dust was collected from the bedrooms of 1038 adults (463 men, 575 women) across five Nordic cities as part of the European Community Respiratory Health Survey (ECRHS) III. Bacterial communities were profiled using 16S rRNA amplicon sequencing. Bacterial and endotoxin loads were quantified via quantitative PCR (qPCR) and the Limulus amebocyte lysate (LAL) assay, respectively. Multivariable linear regression models stratified by sex were used to examine associations with lung function and airway inflammation. Greater indoor bacterial diversity was associated with higher lung function in men (FEV1 β=0.17, 95% CI: 0.05 to 0.29, P=0.003) and higher FeNO levels in women (β=2.44, 95% CI: 0.73 to 4.15, P=0.005). Endotoxin load was positively associated with FeNO in women (β=0.37, 95% CI: 0.05 to 0.70, P=0.02), but not in men. Genera from Actinobacteriota and Bacilli were associated with higher lung function, while Clostridia was linked to lower lung function and reduced FeNO. In contrast, several genera from Actinobacteriota and Gammaproteobacteria were positively associated with FeNO. Indoor bacterial exposures were associated with respiratory health in a sex-specific pattern. These findings highlight the importance of microbial composition in shaping adult lung health and underscore the need for sex-specific approaches in future epidemiological research.

Abstract Background Wastewater treatment plant (WWTP) workers are exposed to biological hazards, including bacteria, fungi, and viruses with pathophysiological properties, posing a risk to workers’ health. Due to the complexity of WWTP bioaerosol composition, exposure assessment is challenging, and new methods are needed for a more holistic evaluation. Objectives (1) Characterize bacterial exposure in three Norwegian wastewater treatment plants (WWTPs), (2) Assess the bioaerosol’s and cultivated viruses’ ability to activate toll-like receptors in vitro, and (3) Elucidate adverse health effects in WWTP workers. Methods Inhalable bioaerosol fractions were collected with personal and stationary sampling, and endotoxin levels and 16S rRNA gene as a biomarker for bacteria were quantified. The inflammatory potential of the bioaerosol was assessed in vitro with HEK-Blue reporter cells, and we investigated the applicability of these cells for viral ligand detection by exposing them to cultivated Influenza A virus, Adenovirus F/40, E. coli phage MS2, and bovine Coronavirus. We used self-reported questionnaire data for an observational health assessment. Results TLR2 and TLR4 were activated in 85 and 91% of bioaerosol samples and activation correlated with airborne endotoxin levels. Airborne bacteria were present in all samples, with higher levels in personal (2.7 × 10 4 gc/m 3 ) versus stationary samples (1.3 × 10 4 gc/m 3 ). Endotoxin levels ranged from <LOD to 4800 EU/m 3 in stationary, and <LOD to 920 EU/m 3 in personal samples, with median levels of 54 and 47 EU/m 3 , respectively. Workers reported a higher prevalence of respiratory symptoms, skin dryness, diarrhea, and fever than unexposed controls. No bioaerosol sample activated TLR3 and 7, while moderate activation was observed by bovine Coronavirus. Significance Workers are continuously exposed to high levels of airborne bacteria levels of endotoxins exceeding 90 Endotoxin units/m 3 , which can induce a TLR2- or TLR4/NF-κB immune response. This exposure occurs throughout their workday, independent of workstations and workers’ tasks. Impact This study highlights the continuous exposure of WWTP workers to bioaerosols with pathophysiological properties, inducing TLR2- and TLR4-NF-κB immune responses. This effect occurs regardless of workstations and workers’ tasks, despite median endotoxin levels remaining below 90 EU/m³. The presence of airborne bacteria and bioaerosols with inflammatory potential may contribute to workers’ health symptoms, and our results highlight the importance of a holistic exposure assessment. We further demonstrate that HEK TLR reporter cell lines provide an innovative method to assess bioaerosol exposure, though they may underestimate exposure to viral-laden bioaerosols.

The typically low concentration of airborne pathogens necessitates the collection of large air volumes coupled with effective enrichment strategies to achieve detectable levels for reliable analysis. In this study, an integrated colorimetric biosensing platform was developed that sequentially combined aerosol‑to‑hydrosol (ATH) collection, passive hydrosol‑to‑hydrosol (HTH) enrichment, and nanozyme‑amplified signal readout. Bacterial aerosols were first collected into a liquid medium using an FA-4 impinger. The collected bacterial suspension was then concentrated 20‑fold within 20 min via a self‑driven superabsorbent polymer (SAP)‑based concentrator integrated with a 0.45 μm polycarbonate track‑etched (PCTE) membrane. Following concentration, target bacteria were specifically labeled with immune Pd/Pt nanozymes. The resulting bacteria-nanozyme complexes were captured on the membrane, while unbound nanozymes were removed by washing. The immobilized nanozymes were used to catalyze the oxidation of the colorless H2O2-TMB substrate to generate the blue TMBox. A linear correlation between the absorbance of the catalysate and bacterial concentration was established for quantitative detection of bacterial aerosols. Under the optimal conditions, the platform achieved an ATH enrichment factor of 3750 and an HTH enrichment factor of 20, yielding a total enrichment capacity of 75,000. The colorimetric biosensor demonstrated a detection limit of 427 CFU/m3 air for target bacteria, with the entire process from air sampling to quantitative readout completed within 2 h. The platform was further validated by field sampling in three poultry housing systems, where it successfully detected airborne bacteria in complex environmental backgrounds, with the results consistent with conventional culture methods. This proposed platform achieves rapid, sensitive, and specific detection of bacterial aerosols, providing a novel and reliable solution for monitoring of bioaerosols.

Airborne microbes from animal confinement facilities not only amplify the risk of disease spread among livestock but also pose substantial health threats to animals and farm workers. The objective of this study was to investigate the microbial counts in cattle sheds and their relationship with meteorological factors, including temperature, relative humidity, and air velocity, as well as microbial diversity. Sampling was carried out both indoors and outdoors of two cattle sheds throughout three seasons (summer, rainy, and winter), at fortnightly intervals. Results showed that bacterial and fungi counts ranged from 0.0 to 1.60 × 103CFU/m3 inside the sheds and from 0.0 to 1.08 × 103CFU/m3 outside, with significant variation between areas and seasons. The predominant microbial count was mesophilic bacteria followed by staphylococci, fungi and Enterobacteriaceae. The mesophilic bacteria, Enterobacteriaceae and fungi showed statistically significant positive correlation with air temperature while air velocity with Enterobacteriaceae bacteria. No significant correlation exists between relative humidity and microbial concentration. The bacterial families Staphylococcaceae and Bacillaceae from the mesophilic group of bacteria were identified as the most prevalent, whereas the dominant fungi taxa in the cattle sheds were Aspergillus spp. and Penicillium spp. The microbial environment within cattle sheds under loose housing systems was found to be well-regulated, with airborne bacteria and fungi levels remaining within recommended limits.

Hospital indoor air is contaminated with multidrug-resistant bacteria, and this contributes to their spread. However, there is limited information linking environmental and atmospheric factors to the levels of these resistant bacteria in indoor hospital air. Hence, this study assessed the levels of multi-drug resistant bacteria in the indoor air of a tertiary hospital and the contributing environmental and atmospheric factors. This cross-sectional study observed hygiene practices, sanitary conditions, occupancy ratio, activity rates, temperature and humidity levels in selected indoor areas of University College Hospital, Ibadan. Airborne bacteria were sampled with their loads via a volumetric sampler, and they were tested for susceptibility against 13 antibiotics via the disk diffusion method. Data was collected twice daily, thrice weekly for two weeks, and analyzed using SPSS version 26. The hygiene practices observed varied across the sampled areas with the office area (10.00 ± 0.00) and psychiatry (9.17 ± 0.41) wards showing best practices, and the laundry area (6.00 ± 0.00) with the worst, sanitary conditions also followed a similar pattern. The study identified 93 bacterial isolates from the MacConkey agar, Staphylococcus aureus (33.3%), Bacillus species (31.18%), Klebsiella pneumoniae (15.05%), Escherichia coli (10.75%), and Coagulase-negative Staphylococcus (9.68%). The mean bacterial load (CFU/m3) varied significantly across sampled areas (p < 0.01): Laundry (2962.96 ± 547.59) > Children Emergency Ward (2537.03 ± 551.67) > Neurosurgery (2310.19 ± 560.31) > Psychiatry (1828.70 ± 431.93) > Office (421.30 ± 311.09), with the exception of office area, the loads were above the WHO acceptable limit of 1000CFU/m3. Bacterial load correlated negatively with hygiene practices and sanitary conditions, but positively with occupancy ratio, activity levels, humidity and temperature, all p < 0.01. The identified bacteria exhibited a high multidrug resistance, this includes the identification of Methicillin Resistant Staphylococcus aureus and extended spectrum beta lactamases producing Escherichia coli and Klebsiella pneumoniae. Healthcare environments, particularly indoor air remains highly contaminated with multidrug-resistant bacteria, with environmental factors like hygiene, sanitation, occupancy, activity, and atmospheric factors like temperature and humidity contributing to their spread. Therefore, improved environmental practices, routine indoor air surveillance and antimicrobial stewardship is advocated.

The levels of airborne bacteria and fungi in the environment of a tertiary hospital in Makurdi, North-Central Nigeria were assessed within 10 selected areas/conditions: theatre at rest (TAR), electrosurgery (ES), inhalational anesthetics (IA), electrosurgery + inhalational anesthetics (ESIA), back of the hospital (BACK), front of the hospital (FRONT), generator house area of the hospital (GEN-H), accident and emergency ward (A&amp;E), intensive care unit (ICU), and microbiology lab (M-LAB). Measurements of the temperature and relative humidity of the sampled areas were also taken. The results were then compared with international microbial air quality guidelines. Mean relative humidity exceeded limits in TAR, ES, ESIA, FRONT, A&amp;E, and M-LAB. Mean bacterial total viable counts (TVCs) exceeded acceptable limits in 5 of the areas assessed (ES, IA, A&amp;E, M-LAB, and GEN-H) while mean fungal TVCs also exceeded acceptable limits in 5 areas (ES, A&amp;E, M-LAB, FRONT, and GEN-H). The most commonly found bacteria were Staphylococcus aureus and Cyanobacterium, while the most commonly found fungal species were species of Aspergillus and Candida albicans. The presence and exceedance of both bacterial and fungal species may result from high relative humidity, the number and activities of occupants in such environments, ineffective disinfecting agents, cleaning frequencies or methods, and/or resistance to their antimicrobial activity. It is recommended that hospital management ensure that the operating theatre (OT) and other departments have adequate air conditioning and ventilation, and regularly assess and evaluate their air to ensure that it is healthy for hospital occupants.

Current culture-based bioaerosol monitoring fails to provide the species-specificity and real-time capabilities essential for indoor air quality and disease surveillance. We developed a culture-free electrochemical aptasensor for rapid, species-specific detection of airborne bacteria. Targeting Moraxella osloensis, a prevalent indoor species identified through next-generation sequencing, we generated a high-affinity aptamer (Kd = 118.9 nM) for M. osloensis and immobilized it on screen-printed gold electrodes. The label-free electrochemical impedance spectroscopy-based sensor achieved near single-cell sensitivity (5.6 CFU/μL detection limit), log-linear quantification (R2 = 0.98), and robust selectivity against six nontarget species, maintaining stability under PM2.5-equivalent dust loads (15-75 μg/m3). In aerosol chamber tests, the sensor successfully quantified airborne M. osloensis with signals correlating to delivered cell numbers and plate counts, demonstrating specificity even in complex microbial and dust conditions. This platform reduces detection time from days to minutes, enabling multiplexed, field-deployable bioaerosol surveillance for indoor air quality and infectious disease monitoring.

We present the first comprehensive comparison of polyurethane foam disk passive air samplers (PUF–PASs) and active high-volume air samplers (Hi-Vol) for bioaerosol monitoring in side-by-side deployments. Using qPCR, 16S rRNA gene sequencing, and multivariate analysis, we demonstrated that the PUF–PASs detected higher bacterial biomass, as evidenced by significantly elevated gene copy numbers and estimated bacterial cells per m3 of air volume, but exhibited lower diversity compared to Hi-Vol samplers. Hi-Vol samplers recovered a more taxonomically diverse community, including transient and rare taxa, during sampling periods of 1 day and 1 week. Hi-Vol detected genera not detected in long-term PUF–PAS sampling, while PUF–PAS detected species not observed in short-term Hi-Vol. PUF–PAS samples were enriched with environmental and spore-forming persistent genera. Hi-Vol samples were enriched with opportunistic and human-associated episodic spikes in a range of bacterial species. PCoA analysis confirmed a substantial divergence in bacterial community structure by sampler type and duration. Temporal analysis results showed a progressive shift in bacterial community composition with increasing sampling duration in PUF–PAS. The findings highlight the complementary benefits of both sampler types: active air sampling for capturing short-lived human-associated bioaerosols and taxonomic richness, while passive air samplers favor biomass accumulation and chronic exposure profiling, enabling exposure assessment and ecological surveillance.

Bioaerosols containing pathogenic microorganisms contribute to the transmission of infectious diseases and pose public health risks. Traditional culture-based detection methods require long incubation times (typically 24-48 h) and often underestimate the microbial concentrations. In this study, we present a femtomolar-level sensitivity biosensor leveraging fluorescence resonance energy transfer (FRET) for detecting adenosine triphosphate (ATP) derived from airborne bacteria. This biosensor utilizes a fluorophore-labeled cDNA (DNA) strand, an unlabeled ATP-specific aptamer, and graphene oxide (GO) that preferentially adsorbs single-stranded DNA over double-stranded DNA. An indirect hybridization approach was employed to avoid the structural interference often observed with directly labeled aptamers, thus improving hybridization efficiency and fluorescence contrast. Under optimized conditions, the biosensor achieved a regression-based analytical limit of detection (LOD) of 0.52 fM ATP while experimentally enabling the detection of airborne bacteria down to 2.4 colony-forming units (CFU) per 1 mL. Importantly, the analytical assay time per measurement was approximately 15 min, which is markedly shorter than that of conventional culture-based methods. The effectiveness and sensitivity of the biosensor were validated through indoor field tests, demonstrating the ability to detect airborne bacteria at concentrations below 102 CFU per 1 m3 of air. This culture-independent method provides a rapid and practical approach for airborne bacterial monitoring and is directly applicable to indoor air quality evaluation and infectious disease management.

Airborne microorganisms significantly contribute to hospital-associated infections (HAIs), particularly causing respiratory tract infections (RTIs). The spread of Multi-Drug Resistant (MDR) airborne bacteria further complicates disease prevention, challenging existing infection control strategies. Current air decontamination technologies are found to have limitations, necessitating novel approaches. In this study, we demonstrated the utility of zeta potential, a natural physicochemical electro-kinetic property of bacteria as a key target, which can be exploited to trap and eliminate MDR airborne bacteria. Multiple respiratory pathogens were included in the study, harbouring various resistance phenotypes. Zeta potentials of these clinical isolates were measured and compared against corresponding ATCC strains. Clinical isolates were aerosolized in a certified BSL-2 setting containing a ZeBox-powered air sterilization device. Viable bacteria were enumerated at various time points, before and after exposure to the air decontamination device. Our analyses revealed that Zeta potential is relatively independent of the origin and antibiotic susceptibility of the tested isolates. Exposure to ZeBox powered device for 5 min resulted in a minimum of 5 log reduction (99.999%) among majority of the isolates, irrespective of their genus and origin. Zeta potential measurements correlated to the kill kinetics of ZeBox technology. The current study underscores the reliability of zeta potential based air decontamination technologies such as ZeBox for potential elimination of diverse, airborne respiratory pathogens in healthcare and domestic settings, offering a promising strategy to combat HAIs in post antibiotic and post pandemic era.