ceftazidime avibactam is beta lactamase inhibitor

Antimicrobial resistance continues to spread, and the emergence of carbapenem-resistant gram-negative bacteria is of particular concern. Whereas most extended spectrum beta-lactamase–producing strains of Escherichia coli, Klebsiella pneumoniae, and other Enterobacteriaceae can be treated with carbapenems, carbapenemaseproducing organisms pose severe challenges. Most patients can be treated with selected beta-lactam/beta-lactamase inhibitors such ceftazidime-avibactam (choice B is correct) or the newer agent meropenem-vaborbactam. If resistance to these agents is present, the polymyxin agent colistin may be required but is problematic because of its nephrotoxicity.

The K. pneumoniae carbapenemase (KPC) is the most clinically important broad spectrum beta-lactamase; it resides on transmissible plasmids and confers resistance to most beta-lactams, including cefepime (choice A is incorrect). In addition, resistance to multiple other antibiotics with gram-negative activity (eg, quinolones, trimethoprim-sulfamethoxazole) is frequently present among carbapenemase-resistant Klebsiella pneumoniae species, making their treatment problematic.

Metronidazole has broad activity against anaerobes via a beta-lactam independent mechanism that generates free radicals that are toxic to susceptible bacteria. K. pneumoniae, as an aerobic organism, is not susceptible (choice C is incorrect). Ceftaroline is a parenteral cephalosporin that is most useful because of its antimicrobial activity against S. aureus (including methicillinand vancomycinresistant S. aureus). It also has activity against gram-negative respiratory pathogens, such as Moraxella catarrhalis and Haemophilus influenzae but not against most Enterobacteriaceae and would be hydrolyzed by the carbapenemase produced by this patient’s infecting organism (choice D is incorrect).

The previous use of third-generation cephalosporins or carbapenems is considered a significant risk factor for the development of colonization or infection with carbapenemase-producing bacteria. (This patient was treated with meropenem for 5 days during his previous hospitalization for acute pancreatitis.) Other reported risk factors include trauma, diabetes mellitus, malignancy, organ transplantation, mechanical ventilation, indwelling urinary or central venous catheters, and overall poor functional status or severe illness.