Antibiotic Resistance Genes in Urban Air

Antibiotic Resistance Genes in Urban Air

Author: Marek Czykanski

Genes for antibiotic resistance are not only found in soils and waters, they also float in the air. It is known that bacteria pass on their resistance to their own offspring. The corresponding genes can also be transferred to other strains and species, among other things by bacteria taking up the free genetic material of dead cells. Such material is found, for example, in the form of so-called plasmids in the environment.

Jing Li, Peking University, China, and colleagues have studied the air in 19 cities worldwide in 2016 and 2017. They searched for 30 known antibiotic resistance genes in airborne particulate matter, which are responsible for resistance to seven different antibiotic classes (quinolones, β-lactams, macrolides, tetracyclines, sulfonamides, aminoglycosides, and vancomycins). For the Chinese town Xi’an, the scientists were also able to access data from the previous years and thus document the concentration of the resistance genes over a period of ten years.

The results show that almost everywhere resistance genes in the form of plasmids and other bacterial genomic particles flow around in the air. Overall, the most common gene was blaTEM, which makes bacteria resistant to β-lactam antibiotics such as penicillin. The second most common was quinolone, such as the ciprofloxacin-resistant gene qepA.

Which and how many resistance genes were to be found in the air differed significantly from city to city. In Beijing, the researchers found the largest variety of genes with 18 subtypes; in Zurich, Switzerland, for example, they found only six subtypes in particulate matter. The highest total concentration of resistance genes was detected in San Francisco, USA. There, the relative abundance of such genes in airborne particulate matter samples was 5.6, while in the Indonesian city of Bandung it was almost 100 times smaller. Also very low contaminated in comparison was the air in Hong Kong as well as in Zurich.

Data from Xi’an also showed clearly that the problem of resistance has intensified in recent years: The relative frequency of the blaTEM gene has increased by 178 % between 2004 and 2014, and that of the qepA gene by 26 %. The concentration of all resistance genes was always highest in summer and lowest in autumn.

The concentration of such genes should be taken into account in assessing air quality in the future, the researchers suggest.

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