Klebsiella aerogenes is a species of Gram-negative bacteria in the Enterobacteriaceae family. For many years, it was known as Enterobacter aerogenes, but recent genetic analysis revealed it is more closely related to Klebsiella pneumoniae, leading to its reclassification. This bacterium is a common inhabitant of the natural environment and is also part of the normal microorganisms in the human gastrointestinal tract. In healthy individuals, K. aerogenes is harmless. It is an opportunistic pathogen, meaning it can cause infections when a person’s defenses are lowered.
Natural Habitats of Klebsiella Aerogenes
Klebsiella aerogenes is widespread in various natural settings. It can be isolated from environmental sources such as soil, sewage, and diverse water systems.
In addition to its environmental distribution, K. aerogenes has a significant role as a commensal organism in humans. It commonly resides in the gastrointestinal tract, coexisting with other gut flora without causing disease in a healthy host. This peaceful coexistence means the bacterium can be a normal part of the human microbiome. The balance can shift, however, if the host’s health is compromised, allowing the bacterium to move from a harmless resident to an infectious agent.
Common Infections and Symptoms
When Klebsiella aerogenes becomes pathogenic, it is frequently implicated in infections acquired within healthcare environments. One of the most common is a urinary tract infection (UTI), which can cause symptoms such as a frequent urge to urinate, a burning sensation during urination, and cloudy or strong-smelling urine.
The bacterium is also a notable cause of hospital-acquired pneumonia, particularly in patients who require mechanical ventilators. In these cases, symptoms often include the sudden onset of fever, chills, coughing, and difficulty breathing. Another serious condition is a bloodstream infection, or bacteremia, which can lead to sepsis. Symptoms of bacteremia may include fever, rapid heart rate, and confusion. Surgical wound infections are also a concern, characterized by redness, swelling, pain, and pus at the incision site.
Transmission and High-Risk Environments
Infections with Klebsiella aerogenes are primarily acquired in hospital and long-term care facilities. Transmission occurs through contact with contaminated objects and surfaces, such as bed rails and medical equipment. Invasive medical devices, including urinary catheters, intravenous lines, and ventilators, are common vehicles for introducing the bacteria into the body.
The hands of healthcare workers can also serve as a vector for transmitting the bacteria between patients if proper hand hygiene is not followed. The bacteria are not transmitted through the air. The individuals most susceptible to infection are those with weakened immune systems, patients in intensive care units (ICUs), and people undergoing extended courses of antibiotic treatment. The presence of indwelling medical devices substantially increases the risk of developing an infection.
Treatment and Antibiotic Resistance
The standard approach to treating infections caused by Klebsiella aerogenes is antibiotic therapy. A significant and growing challenge is the bacterium’s ability to develop resistance to many common antibiotics. Many strains are multidrug-resistant (MDR), meaning they are unaffected by several types of antibiotics.
A major public health concern is the emergence of strains resistant to a class of powerful antibiotics called carbapenems. When K. aerogenes is resistant to these drugs, it is known as carbapenem-resistant Enterobacteriaceae (CRE), making infections particularly difficult to manage. The primary mechanisms for this resistance include the production of enzymes that can inactivate the antibiotics, such as carbapenemases.
To guide effective treatment, laboratories perform susceptibility testing on the bacterial strain isolated from a patient to determine which antibiotics will be effective. The results are necessary for selecting an appropriate antibiotic regimen, which may require using older, more toxic drugs or a combination of therapies to overcome the resistance.