Microbial communities related to volatile organic compound emission in automobile air conditioning units

Jung

et al. 2020

mSphere

Microbial communities in the evaporator core (EC) of automobile air-conditioning systems have a large impact on indoor air quality, such as malodor and allergenicity. DNA-based microbial population analysis of the ECs collected from South Korea, China, the United States, India, and the United Arab Emirates revealed the extraordinary dominance of Methylobacterium species in EC biofilms. Mixed-volatile organic compound (VOC) utilization and biofilm-forming capabilities were evaluated to explain the dominance of Methylobacterium species in the ECs. The superior growth of all Methylobacterium species could be possible under mixed-VOC conditions. Interestingly, two lifestyle groups of Methylobacterium species could be categorized as the aggregator group, which sticks together but forms a small amount of biofilm, and the biofilm-forming group, which forms a large amount of biofilm, and their genomes along with phenotypic assays were analyzed. Pili are some of the major contributors to the aggregator lifestyle, and succinoglycan exopolysaccharide production may be responsible for the biofilm formation. However, the coexistence of these two lifestyle Methylobacterium groups enhanced their biofilm formation compared to that with each single culture. IMPORTANCE Air-conditioning systems (ACS) are indispensable for human daily life; however, microbial community analysis in automobile ACS has yet to be comprehensively investigated. A bacterial community analysis of 24 heat exchanger fins from five countries (South Korea, China, the United States, India, and the United Arab Emirates [UAE]) revealed that Methylobacterium species are some of the dominant bacteria in automobile ACS. Furthermore, we suggested that the predominance of Methylobacterium species in automobile ACS is due to the utilization of mixed volatile organic compounds and their great ability for aggregation and biofilm formation.

Section: Resultssupporting

confidence: 89%

Section: Discussionmentioning

confidence: 99%

Dominance of Gas-Eating, Biofilm-Forming Methylobacterium Species in the Evaporator Cores of Automobile Air-Conditioning Systems

Jung

et al. 2020

mSphere

“…Opportunistic pathogens such as nontuberculous mycobacteria (NTM) and legionellae may enter cars via biofilms in car heaters/air conditioners (AC) (11,12) and in windshield washer reservoirs (13), as well as other sources (14)(15)(16). Even though many types of NTM are increasingly recognized as human pathogens (17)(18)(19), there is virtually no information on their recovery from inside the family car.…”

Section: Discussionmentioning

confidence: 99%

Airborne Pathogens inside Automobiles for Domestic Use: Assessing In-Car Air Decontamination Devices Using Staphylococcus aureus as the Challenge Bacterium

Sattar

Zargar

Wright

et al. 2017

Appl Environ Microbiol

Family cars represent ∼74% of the yearly global output of motorized vehicles. With a life expectancy of ∼8 decades in many countries, the average person spends >100 min daily inside the confined and often shared space of the car, with exposure to a mix of potentially harmful microbes. Can commercial in-car microbial air decontamination devices mitigate the risk? Three such devices (designated devices 1 to 3) with HEPA filters were tested in the modified passenger cabin (3.25 m) of a four-door sedan housed within a biosafety level 3 containment facility. (ATCC 6538) was suspended in a soil load to simulate the presence of body fluids and aerosolized into the car's cabin with a 6-jet Collison nebulizer. A muffin fan (80 mm by 80 mm, with an output of 0.17 m/min) circulated the air inside. Plates (150 mm diameter) of Trypticase soy agar (TSA), placed inside a programmable slit-to-agar sampler, were held at 36 ± 1°C for 18 to 24 h and examined for CFU. The input dose of the test bacterium, its rate of biological decay, and the log reductions by the test devices were analyzed. The arbitrarily set performance criterion was the time in hours a device took for a 3-log reduction in the level of airborne challenge bacterium. On average, the level of challenge in the air varied between 4.2 log CFU/m and 5.5 log CFU/m, and its rate of biological decay was -0.0213 ± 0.0021 log CFU/m/min. Devices 1 to 3 took 2.3, 1.5, and 9.7 h, respectively, to meet the performance criterion. While the experimental setup was tested using as an archetypical airborne pathogen, it can be readily adapted to test other types of pathogens and technologies. This study was designed to test the survival of airborne pathogens in the confined and shared space of a family automobile as well as to assess claims of devices marketed for in-car air decontamination. The basic experimental setup and the test protocols reported are versatile enough for work with all major types of airborne human pathogens and for testing a wide variety of air decontamination technologies. This study could also lay the foundation for a standardized test protocol for use by device makers as well as regulators for the registration of such devices.

Journal of Environmental and Public Health

“…Biofilms formed in car heaters/air conditioners [11, 12] as well as those in windshield washer reservoirs [13] and other areas of the car may release microbes such as legionellae and possibly environmental or nontuberculous mycobacteria (NTM) as well as airborne opportunistic pathogens. Such pathogens may also come from road dust and water in road puddles [14].…”

Section: Sources Of Microbes Their Allergens and Toxinsmentioning

confidence: 99%

“…An investigation on malodors associated with air-conditioning systems in automobiles found the heat exchanger fins of 45 evaporators from seven different regions of the world to be coated with biofilms [11]. The biofilms were analyzed and found to contain a wide variety of bacteria including potential human pathogens such as members of the genera Sphingomonadales, Burkholderiales, Bacillales, and Stenotrophomonas .…”

Section: Infectious Agents Of Concernmentioning

confidence: 99%

Airborne Infectious Agents and Other Pollutants in Automobiles for Domestic Use: Potential Health Impacts and Approaches to Risk Mitigation

Sattar

Wright

Zargar

et al. 2016

The world total of passenger cars is expected to go from the current one billion to >2.5 billion by 2050. Cars for domestic use account for ~74% of the world's yearly production of motorized vehicles. In North America, ~80% of the commuters use their own car with another 5.6% travelling as passengers. With the current life-expectancy of 78.6 years, the average North American spends 4.3 years driving a car! This equates to driving 101 minutes/day with a lifetime driving distance of nearly 1.3 million km inside the confined and often shared space of the car with exposure to a mix of potentially harmful pathogens, allergens, endotoxins, particulates, and volatile organics. Such risks may increase in proportion to the unprecedented upsurge in the numbers of family cars globally. Though new technologies may reduce the levels of air pollution from car exhausts and other sources, they are unlikely to impact our in-car exposure to pathogens. Can commercial in-car air decontamination devices reduce the risk from airborne infections and other pollutants? We lack scientifically rigorous protocols to verify the claims of such devices. Here we discuss the essentials of a customized aerobiology facility and test protocols to assess such devices under field-relevant conditions.