# Antibiotic Resistance in Filters from Car Air Conditioning Systems
## 3 Results and Discussion
However, studying the fungal microfloraallowed the authors to isolate seven azide-resistant fungal strains belonging to the genera _Penicillium_, _Cladosporium_, and _Aspergillus_. The combination of culture-based methods and molecular analysis of antibiotic resistance genes was also applied by [PERSON] et al. [34] during the study of dust samples from air conditioning systems in hospitals. They revealed the contamination of the samples with antibiotic resistance genes. In parallel, they obtained some isolates of resistant bacteria on media with antibiotics such as ampicillin, chloromycetin, meropenem, kanamycin, tetracycline or erythromycincin. The study confirmed the presence of both resistant bacteria and antibiotic resistance genes in the samples and the possibility of their accumulation in hospital air conditioning systems. Molecular analysis in the form of high-throughput qPCR with Illumina sequencing was used by [PERSON] et al. [33] in a study including 12 samples of dust collected from air conditioning filters from different environments: hospitals, urban and rural residences, and farms. The techniques they used allowed them to determine the antibiotic resistance profile in the samples, including the frequency of resistance genes in each type of facility. A total of 177 different antibiotic resistance determinant genes were detected, mostly in samples from farms and rural buildings. Molecular biodiversity studies revealed a predominance of Proteobacteria in dust from tested air conditioning systems. Bacteria belonging to Proteobacteria, Actinobacteria, and Chloroflexi were identified as the most common hosts of antibiotic-resistant genes, with Proteobacteria and Actinobacteria being the most frequently involved in multi-resistance. In this research, quantitative analysis of bacteria resistant to selected antibiotics showed that these microorganisms were common in filters from all analyzed car brands (Figures 3-7) and their abundance was at the level of 10\({}^{2}\)-10\({}^{3}\) CFU/g. One of the reasons for this can be the relatively high level of standardization in the production of cabin filters and the fact that a given manufacturer offers filters with similar properties but dedicated to different brands of vehicles. This makes the possible level of contamination a matter of how the vehicle is used rather than the brand. As in the case of the total number of bacteria and fungi, there were quite large differences in the concentration of antibiotic-resistant bacteria in filters from individual vehicles (Table 2). Both the total level of microbial contamination of filter materials and the content of antibiotic-resistant bacteria turned out to be a very individual matter, and in fact, each vehicle could be considered as a separate case. It is likely that much here is due to the varying conditions and locations of each vehicle's operation. In particular, it is difficult to explain the incidentally occurring exceptionally high numbers of bacteria resistant to the antibiotics tested in individual vehicles, such as for nitrofurantoin in Volkswagen 2, rifampicin in Volkswagen 1, doxycycline in Hyundai 4, or penicillin in Subaru 3. Figure 4: Numbers of nitrofurantoin-resistant bacteria in cabin filters of individual vehicles. Figure 3: Numbers of penicillin-resistant bacteria in cabin filters of individual vehicles. Figure 5: Numbers of rifampicin-resistant bacteria in cabin filters of individual vehicles. Figure 6: Numbers of doxycycline-resistant bacteria in cabin filters of individual vehicles. In some cases, these bacteria were not detected, which may have been due to the range of detection resulting from the culture technique. Such results were marked in the figures as \"not detected\", while also including the situation when the abundance of bacteria tested was below 100 CFU/g. Analysis of the percentage of antibiotic-resistant bacteria in the total number of bacteria provided interesting results (Figure 8). It showed significant differences between filters from tested car brands.