Carbapenems are a class of very effective antibiotic agents most commonly used for the treatment of severe bacterial infections. This class of antibiotics is usually reserved for known or suspected multidrug-resistant (MDR) bacterial infections. Similar to penicillins and cephalosporins, carbapenems are members of the beta lactam class of antibiotics, which kill bacteria by binding to penicillin-binding proteins, thus inhibiting bacterial cell wall synthesis. However, these agents individually exhibit a broader spectrum of activity compared to most cephalosporins and penicillins. Furthermore, carbapenems are typically unaffected by emerging antibiotic resistance, even to other beta-lactams. Carbapenem antibiotics were originally developed at Merck & Co. from the carbapenem thienamycin, a naturally derived product of Streptomyces cattleya. Concern has arisen in recent years over increasing rates of resistance to carbapenems, as there are few therapeutic options for treating infections caused by carbapenem-resistant bacteria (such as Klebsiella pneumoniae and other carbapenem-resistant Enterobacteriaceae). Medical uses Intra-abdominal infections The carbapenem ertapenem is one of several first-line agents recommended by the Infectious Disease Society of America for the empiric treatment of community-acquired intra-abdominal infections of mild-to-moderate severity. Agents with anti-pseudomonal activity, including doripenem, imipenem, and meropenem, are not recommended in this population. Doripenem, imipenem, and meropenem are recommended for high-risk community-acquired abdominal infections and for abdominal infections that are hospital-acquired. Complicated urinary tract infections A 2015 systematic review found little evidence that would support the identification of a best antimicrobial regimen for complicated urinary tract infections, but identified three high-quality trials supporting high cure rates with doripenem, including in patients with levofloxacin-resistant E. coli infections. Pneumonia The carbapenems imipenem and meropenem are recommended by the American Thoracic Society and the Infectious Disease Society of America as one of several first-line therapy options for people with late-onset hospital-acquired or ventilator-associated pneumonia, especially when Pseudomonas, Acinetobacter, or extended spectrum beta-lactamase producing Enterobacteriaceae are suspected pathogens. Combination therapy, typically with an aminoglycoside, is recommended for Pseudomonas infections to avoid resistance development during treatment. Carbapenems are less commonly used in the treatment of community-acquired pneumonia, as community-acquired strains of the most common responsible pathogens (Streptococcus pneumoniae, Haemophilus influenazae, atypical bacteria, and Enterobactericeace) are typically susceptible to narrower spectrum and/or orally administered agents such as fluoroquinolones, amoxicillin, or azithromycin. Imipenem and meropenem are useful in cases in which P. aeruginosa is a suspected pathogen. Bloodstream Infections A 2015 meta analysis concluded that the anti-pseudomonal penicillin-beta lactamase inhibitor combination piperacillin-tazobactam gives results equivalent to treatment