The installation of HVAC systems in building is meant to enhance indoor air quality as well as increase comfort to occupants. However, HVAC systems have also become a vehicle of contamination of indoor air with potentially pathogenic microorganisms. DNA was extracted from ten HVAC filter dust samples collected from two buildings and subjected to high throughput sequencing analysis to determine the bacterial community structure. Further, the Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt2) software was used to predict the potential functional capabilities of the bacterial communities. Sequencing analysis led to the identification of five major bacterial phyla, including Proteobacteria, Cyanobacteria, Actinobacteria, Firmicutes and Bacteroidetes. At genus level, Mycobacterium, Bacillus, Cupriavidus, Hyphomicrobium and Mesorhizobium were the most dominant. With the exception of the later two bacterial genera, the first three are potential pathogens whose presence in HVAC systems poses a significant public health risk, especially among immunocompromised individuals. Nine pathways associated with antibiotics resistance and bacterial pathogenicity were identified, including polymyxin resistance and peptidoglycan biosynthesis pathways. Further, investigation of the relationship between the detected bacterial meta-communities and predicted potential virulence factors (antibiotic resistance and pathogenic genes) led to the detection of 350 positive associations among 43 core bacteria, 2 pathogenic genes (sitA and uidA) and 14 resistance genes. Overall, the heterogeneous nature of microorganisms found in HVAC systems observed in this study shows that HVAC systems are the origin of airborne infections in indoor environments, and must be periodically cleaned and disinfected to avoid the build-up of pathogens, and the subsequent exposure of human occupants of these pathogens.

在建筑物中安装 HVAC 系统旨在提高室内空气质量并增加居住者的舒适度。然而，HVAC 系统也已成为潜在病原微生物污染室内空气的媒介。从两座建筑物收集的十个 HVAC 过滤器灰尘样本中提取 DNA，并进行高通量测序分析以确定细菌群落结构。此外，通过重建未观察状态（PICRUSt2）软件对群落的系统发育调查用于预测细菌群落的潜在功能能力。测序分析导致鉴定出五个主要细菌门，包括变形菌门、蓝细菌门、放线菌门、厚壁菌门和拟杆菌门。在属水平上，分枝杆菌属、芽孢杆菌属、嗜铜菌属、细小菌属和中根瘤菌属是最占主导地位的。除了后两个细菌属之外，前三个是潜在的病原体，它们在 HVAC 系统中的存在会构成重大的公共健康风险，尤其是在免疫功能低下的个体中。确定了与抗生素耐药性和细菌致病性相关的九种途径，包括多粘菌素耐药性和肽聚糖生物合成途径。此外，对检测到的细菌元群落与预测的潜在毒力因子（抗生素耐药性和致病基因）之间关系的调查导致在 43 个核心细菌、2 个致病基因（sitA和uidA ）之间检测到 350 个正相关。) 和 14 个抗性基因。总体而言，本研究中观察到的 HVAC 系统中发现的微生物的异质性表明，HVAC 系统是室内环境中空气传播感染的源头，必须定期清洁和消毒以避免病原体的积聚，以及随后暴露于这些病原体的人类居住者。