Acinetobacter lwoffii is a widespread bacterium belonging to the Acinetobacter genus. It is classified as a Gram-negative bacillus, meaning its cell wall structure prevents it from retaining the crystal violet stain used in the Gram staining procedure. It is a non-fermentative microbe that relies strictly on aerobic respiration for energy. A. lwoffii is ubiquitous, found across numerous environments outside the human body.
Classification and Natural Habitat
The taxonomic identity of this bacterium places it within the Phylum Proteobacteria, Class Gammaproteobacteria, Order Pseudomonadales, and Family Moraxellaceae. Acinetobacter lwoffii is a non-motile organism, though some members of the genus can exhibit twitching motility. It requires oxygen for growth and does not ferment carbohydrates.
In the environment, A. lwoffii is widespread and highly resilient, demonstrating an ability to survive in various ecological niches. It is commonly isolated from soil, fresh water, and sewage systems, where it acts as a saprophyte. Its ability to survive on both moist and dry surfaces allows it to persist for extended periods in diverse settings, including food products like frozen goods, pasteurized milk, and fish.
Relationship with the Human Body
For most people, Acinetobacter lwoffii is a commensal organism, living on or within the human body without causing harm. It is considered part of the normal human flora, or microbiome, especially of the skin and mucous membranes. The bacterium colonizes areas such as the oropharynx and the perineum, sometimes residing in up to a quarter of healthy individuals.
The presence of the organism on the body is referred to as colonization, which differs fundamentally from an infection. Colonization means the microbe is established and growing, but the host’s immune system or the organism’s low virulence prevents disease symptoms. An infection occurs when the organism multiplies and invades host tissues, leading to inflammation, tissue damage, and clinical symptoms. In healthy people, A. lwoffii rarely transitions from a harmless colonizer to an infectious agent.
Clinical Significance and Associated Infections
A. lwoffii becomes medically significant when it acts as an opportunistic pathogen, typically in compromised host settings. Infections are infrequent and overwhelmingly found in individuals with weakened immune systems, severe underlying illnesses, or those who have undergone invasive medical procedures. The presence of indwelling medical devices, such as urinary catheters or central venous lines, provides a pathway for the organism to bypass the body’s natural defenses.
As a result, the infections caused by this bacterium are often classified as nosocomial, or hospital-acquired. A. lwoffii has been implicated in several types of serious infections, including bacteremia (bloodstream infection) often linked to catheter use. It may also cause respiratory conditions like pneumonia, urinary tract infections, meningitis, and infections of surgical sites or wounds.
It is important to contrast A. lwoffii with its more notorious relative, Acinetobacter baumannii, known for its high virulence and drug resistance. While both species can cause similar infections, A. lwoffii has low virulence, and infections caused by it are associated with a substantially lower mortality rate. This lower risk is partly due to A. lwoffii’s reduced ability to form strong biofilms and its general susceptibility to common antibiotics.
Management and Antibiotic Susceptibility
The management of an A. lwoffii infection typically involves the use of appropriate antimicrobial agents once the organism has been identified as the cause of disease. Unlike many other species in the genus, A. lwoffii isolates are often sensitive to a variety of standard, broad-spectrum antibiotics. This general susceptibility is a factor in the favorable outcomes observed with these infections.
Effective treatment often includes broad-spectrum beta-lactam antibiotics, such as piperacillin-tazobactam or certain cephalosporins like ceftazidime. Other effective classes include aminoglycosides, such as amikacin, and fluoroquinolones, like ciprofloxacin. The bacterium possesses fewer genes for antibiotic resistance and efflux pumps compared to A. baumannii, which contributes to its lower rates of acquired drug resistance. While resistance can still emerge, management remains less complicated than that of its highly drug-resistant relatives.