Given the task definition and input, reply with output. In this task, you are given an abstract of article. Your task is to generate title for this article. Preferred titles are under thirty words.

-Lactamase evolution presents to the infectious disease community a major challenge in the treatment of infections caused by multidrug-resistant gram-negative bacteria. Because over 1,000 of these naturally occurring -lactamases exist, attempts to correlate structure and function have become daunting. Although new enzymes in the extended-spectrum -lactamase (ESBL) families are frequently identified, the older CTX-M-14 and CTX-M-15 enzymes have become the most prevalent ESBLs in global surveillance. Carbapenemases with either serine-based or zinc-facilitated hydrolysis mechanisms are posing some of the most critical problems. Most geographical regions now report KPC serine carbapenemases and the metallo--lactamases VIM, IMP, and NDM-1, even though NDM-1 was only recently identified. The rapid emergence of these newer enzymes, with multiple -lactamases appearing in a single organism, makes the design of new -lactamase inactivators or -lactamase-stable -lactams all the more difficult. Combination therapy will likely be required to counteract the continuing evolution of these insidious enzymes in multidrug-resistant pathogens.
Epidemiological expansion, structural studies, and clinical challenges of new -lactamases from gram-negative bacteria.