Multidrug-resistant and extensively drug-resistant Mycobacterium tuberculosis strains are spreading globally, and thus, new antituberculosis drugs are urgently needed. The M. tuberculosis L,D-transpeptidase LdtMt2 is directly involved in peptidoglycan formation, bacterial virulence and β-lactam resistance. This enzyme is a potential antituberculosis target that can be inhibited by carbapenems, FDA-approved drugs that are used in the treatment of tuberculosis. Two different intermediate states, states I and II, have been reported for LdtMt2 interacting with carbapenems, such as ertapenem, imipenem and meropenem. State I was proposed as an initial adduct formation state, whereas state II was proposed as a stable protein-ligand interaction state accompanied by local conformational arrangements of both carbapenem and the protein. Here, we report a new LdMt2-ertapenem interaction state, I-plus, with the same carbapenem conformation as state II and a similar local protein conformation to state I. This new state was proposed as an intermediate state for the transition from state I to state II, in which the ertapenem molecule, but not the protein, undergoes a conformational change. Our work helps elucidate the changes that occur after carbapenem acts on LdtMt2 and, together with the other reported state, demonstrates how the L,D-transpeptidase interacts with carbapenems.