# Antibiotic Resistance in Filters from Car Air Conditioning Systems
## 3 Results and Discussion
For example, penicillin-resistant bacteria accounted for 0.02% in filters from Toyota cars to as much as 4.83% in filters from Subaru, while it should be noted that the observed differences were mainly due to the difference in the total number of bacteria and not to a higher number of resistant microorganisms. It is also confirmed by comparing the filters from Subaru with those from Hyundai and Volkswagen, where the abundance of penicillin-resistant bacteria was similar, while their percentage differed even several times. A similar relationship was also observed for bacteria resistant to other \begin{table}
\begin{tabular}{c c c c c c c} \hline  & & \multicolumn{5}{c}{**Bacteria Resistant to Antibiotic (CFU/g)**} \\ \cline{3-6}  & & **Penicillin** & **Nitrofurantoin** & **Rifampicin** & **Doxycycline** & **Gentamicin** \\ \hline Toyota & Average & \(5.30\times 10^{2}\) & \(4.58\times 10^{2}\) & \(1.11\times 10^{3}\) & \(3.50\times 10^{2}\) & \(4.98\times 10^{2}\) \\  & standard deviation & \(4.82\times 10^{2}\) & \(3.43\times 10^{2}\) & \(1.04\times 10^{3}\) & \(2.64\times 10^{2}\) & \(4.58\times 10^{2}\) \\ Hyundai & Average & \(1.23\times 10^{3}\) & \(1.26\times 10^{3}\) & \(7.25\times 10^{2}\) & \(1.78\times 10^{3}\) & \(5.80\times 10^{2}\) \\  & standard deviation & \(1.52\times 10^{3}\) & \(0.39\times 10^{3}\) & \(1.50\times 10^{2}\) & \(1.93\times 10^{3}\) & \(2.14\times 10^{2}\) \\ Subaru & Average & \(2.06\times 10^{3}\) & \(9.40\times 10^{2}\) & \(4.53\times 10^{2}\) & \(1.10\times 10^{3}\) & \(7.70\times 10^{2}\) \\  & standard deviation & \(2.60\times 10^{3}\) & \(6.55\times 10^{2}\) & \(2.40\times 10^{2}\) & \(0\) & \(4.67\times 10^{2}\) \\  & Average & \(2.17\times 10^{3}\) & \(2.45\times 10^{3}\) & \(1.79\times 10^{3}\) & \(1.53\times 10^{3}\) & \(1.10\times 10^{3}\) \\  & standard deviation & \(0.61\times 10^{3}\) & \(2.23\times 10^{3}\) & \(2.17\times 10^{3}\) & \(0.45\times 10^{3}\) & \(0.36\times 10^{3}\) \\ Suzuki & Average & \(9.47\times 10^{2}\) & \(7.70\times 10^{2}\) & \(1.61\times 10^{3}\) & \(1.48\times 10^{3}\) & \(6.53\times 10^{2}\) \\  & standard deviation & \(4.97\times 10^{2}\) & \(8.40\times 10^{2}\) & \(1.11\times 10^{3}\) & \(0.67\times 10^{3}\) & \(3.74\times 10^{2}\) \\ \hline \end{tabular}
\end{table} 
Table 2: Average abundance of antibiotic-resistant bacteria in cabin filters of vehicles of different brands. Figure 7: Numbers of gentamicin-resistant bacteria in cabin filters of individual vehicles. antibiotics. This may suggest that in some situations, despite the limited abundance of bacteria in the filter material as a result of the technical solutions used, we may still have to deal with relatively abundant bacteria showing antibiotic-resistant characteristics. As confirmed by numerous literature data, filter materials used in air conditioning systems can harbor a diverse bacterial microflora including representatives of Proteobacteria, Firmicutes, Bacteroidetes, Actinobacteria, and Cyanobacteria [31]. Bacterial taxa that are indicated to be associated with air conditioning systems include the genera _Sphingomonas_, _Burkholderia_, _Bacillus_, _Alamivorax_, _Stenotrophomonas_[26], _Pseudomonas_[39], and _Bacillus_[31]. The latter, due to their relatively large size, can be effectively retained and accumulated in the filter material [29]. Studies of the indoor air of vehicles confirm the presence of a diverse microflora, with bacteria from the genera _Microoccus_, _Kocuria_, _Staphylococcus_, and _Bacillus_ appearing as constant bioaerosol components [30], as well as Gram-negative bacteria from the genera _Comamonas_, _Pseudomonas_, and _Serratia_[29]. [PERSON] et al. [8] found that bacteria of the genus _Pseudomonas_ were the dominant microflora in dust from the air conditioning system. This is consistent with the results obtained in the present study, where identification using biochemical tests and molecular analysis confirmed that the isolated antibiotic-resistant bacteria belonged to the genera _Pseudomonas_ and _Brevundimonas_.