Fig. 2

Bubble chart depicting the number of Tn records containing resistance genes against different types of antibiotic classes. Antibiotic classes were sorted according to the year of introduction on the Y-axis. Tn records were grouped into 5 groups on the X-axis according to the previously published lists [3,4,5], and before and after the allocation by the Tn registry (starting at Tn6000). The number of Tn records is represented by the bubble size and also indicated on the right of each bubble. * year of discovery as approval never received