Morganella

Morganella is a genus of Gram-negative, rod-shaped bacteria in the family Morganellaceae, within the order Enterobacterales. The most clinically significant species is Morganella morganii, which can be a component of the normal intestinal microbiota but also acts as an opportunistic pathogen.

Ecology and clinical relevance: Morganella morganii is found in the human gut and in environmental sources. It is associated with opportunistic infections, particularly in hospitalized or immunocompromised individuals. Infections can include urinary tract infections, wound and soft-tissue infections, bacteremia, intra-abdominal infections, and, less commonly, meningitis or pneumonia.

Laboratory identification and characteristics: Morganella morganii is detected by routine bacterial culture from clinical specimens. It is a Gram-negative, rod-shaped bacillus commonly identified by standard biochemical tests or modern methods such as matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry. Like other Enterobacterales, it is typically oxidase-negative.

Antimicrobial susceptibility and treatment: Susceptibility patterns for Morganella morganii are variable and can differ by strain and setting. Some isolates show resistance to commonly used antibiotics, and acquired resistance mechanisms, including extended-spectrum beta-lactamases in rare cases, have been reported. Appropriate therapy is guided by antimicrobial susceptibility testing. In moderate to severe infections, options often include third-generation cephalosporins, fluoroquinolones, or carbapenems, depending on the susceptibility profile of the isolate.