The gram-negative bacteria Klebsiella, Enterobacter, and Serratia are closely related normal intestinal flora that rarely cause disease in normal hosts. Diagnosis is by culture. Treatment is with antibiotics.
Infections with Klebsiella, Enterobacter, and Serratia are often hospital-acquired and occur mainly in patients with diminished resistance. These three 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 with dark brown or red currant–jelly sputum, lung abscess formation, and empyema, is most common among people with diabetes and people with an alcohol use disorder.
Serratia, particularly S. marcescens, has greater affinity for the urinary tract.
Enterobacter most often cause nosocomial infections but can cause otitis media, cellulitis, and neonatal sepsis.
Diagnosis is by culture of blood and/or other infected tissue. 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 3rd-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 Enterobacter1).
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
