Author(s): John P Quinn [*] 1
carbapenemases; carbapenems; Klebsiella pneumoniae; KPC enzymes; metallobetalactamases; OXA enzymes
[beta]-lactam antibiotics remain one of our workhorse classes for serious infection due to their usually broad activity and attractive safety profile. [beta]-lactamases are the most important determinants of resistance to the class. The carbapenems are particularly valuable as they are often the last ditch option for patients infected with organisms resistant to older classes. Therefore, the recent worldwide expansion of carbapenem hydrolyzing enzymes is of great clinical concern.
In this issue of Expert Reviews of Anti Infective Therapy, Maya et al . working with collaborators throughout Latin America, review the emerging data on the spread of carbapenemases in this region  . They found abundant evidence of wide dissemination of various enzymes from multiple classes, especially Klebsiella pneumoniae carbapenemase (KPC), metallo [beta]-lactamases (MBLs) and, among Acinetobacter , OXA type enzymes.
Although this review, by local investigators, focused on Latin America, similar data are available in Europe and the USA  . There are fewer data in Asia, with the exception of the special case of NDM enzymes on the Indian subcontinent  .
The molecular classification of carbapenemases is of scientific interest but not clinically important, so will not be discussed here. Instead I will focus my comments on a few of the more common and clinically important enzymes. I will briefly review the epidemiology, detection and treatment options, where data exist, in each case.
These were first described in the USA, where they seemed to be limited to the east coast at first, but have now spread nationwide. Although first detected in Klebsiella (hence the name, Klebsiella pneumoniae carbapenemase), they are now widespread in other enterics and in Pseudomonas aeruginosa . They are usually seen in sick, hospitalized patients who have been exposed to antibiotics. In the USA, long-term care facilities have been an important source of colonized or infected patients  . Often these organisms contain multiple enzymes and have other resistance determinants, usually leading to an extremely broad resistance profile, typically remaining susceptible in vitro only to tigecycline and colistin, neither of which is ideal for therapy. Much of the global expansion...