The gram-negative bacteria Klebsiella, Enterobacter, and Serratia are closely related normal intestinal flora that rarely cause disease in immunocompetent hosts. Diagnosis is by culture. Treatment is with antibiotics.
Klebsiella, Enterobacter, and Serratia are members of the Enterobacterales (formerly Enterobacteriaceae) family.
Infections with these 3 bacteria are often hospital-acquired and occur mainly in patients with diminished resistance to infection (eg, underlying medical conditions, indwelling catheters and devices). These bacteria can cause a wide variety of infections, including bacteremia, surgical site infections, intravascular catheter infections, and respiratory or urinary tract infections that manifest as pneumonia, cystitis, or pyelonephritis and that may progress to lung abscess, empyema, bacteremia, and sepsis, as in the following:
Klebsiella pneumonia, a rare and severe disease often with dark brown or red currant–jelly sputum, lung abscess formation, and empyema, is most common among people with diabetes and people with alcohol use disorder. It can also cause primary community-acquired liver abscess.
Serratia, particularly S. marcescens, has greater affinity for the urinary tract but also is frequently isolated from the respiratory tract and wounds.
Enterobacter most often cause nosocomial infections (respiratory, urinary, and bloodstream) but can cause otitis media, cellulitis, and neonatal sepsis.
Diagnosis is by culture of blood and/or other infected tissue or fluid collections. Susceptibility testing is also done.
Treatment
Antibiotics based on results of susceptibility testing
KlebsiellaK. pneumoniae
Enterobacter strains may become resistant to most beta-lactam antibiotics, including third-generation cephalosporins; the beta-lactamase enzyme they produce (AmpC beta-lactamase) is not inhibited by the usual beta-lactamase inhibitors (clavulanate, tazobactam, sulbactam). However, these Enterobacterceftazidime/avibactam, meropenem/vaborbactam, imipenem/relebactameravacycline, cefiderocol, and perhaps colistin may be the only available active antibiotics (1).
(See also the Infectious Diseases Society of America's 2023 Guidance on the Treatment of Antimicrobial Resistant Gram-Negative Infections.)
Treatment reference
1. Thaden JT, Pogue JM, Kaye KS: Role of newer and re-emerging older agents in the treatment of infections caused by carbapenem-resistant Enterobacteriaceae. Virulence 8(4):403–416, 2017. doi: 10.1080/21505594.2016.1207834
More Information
The following English-language resource may be useful. Please note that THE MANUALS is not responsible for the content of this resource.
Infectious Diseases Society of America (IDSA): Guidance on the Treatment of Antimicrobial Resistant Gram-Negative Infections (2023)
