Staphylococcus strains with mecA are resistant to lactam antibiotics and frequently have multi-drug resistance, which may represent a serious health and economic concern [37,38]. Therefore, it is highly important to detect mecA, especially in Staphylococcus samples. In recent years, increasing numbers of reports have shown that the mecA gene is present in CNS strains, including hospital-acquired infections, neighborhoods [39,40], animal epidermis [41] and beaches [42], amongst others. To date, no reports have described the detection or discovery of mecA in airborne bacteria isolated from public transportation systems. Our research has shown that the presence of mecA from Staphylococcus was not as high as in strains from patients who have used antibiotics for long periods, which can reach over 90% in China [43]. Nevertheless, the metro is an important part of the Shanghai public transport system and should warrant closer inspection.