Enterobacter is a genus of bacteria that includes multiple species, many of which are commonly found throughout the environment. They inhabit soil, water, and sewage, and are also a normal part of the intestinal microbial community in humans and animals. These bacteria are typically harmless in healthy individuals. However, some Enterobacter species are recognized as opportunistic pathogens, meaning they can cause infections when a person’s defenses are lowered. This makes them a subject of interest in healthcare environments, where they can pose a risk to vulnerable individuals.
Sources and Transmission
Enterobacter species are widespread in nature, thriving in both terrestrial and aquatic environments. While they exist as commensal organisms, meaning they live in the human gut without causing harm, they can become a source of infection if they move to other parts of the body. This is particularly common in healthcare settings.
Hospital-acquired, or nosocomial, infections are the most frequent type of Enterobacter infections. The bacteria can contaminate various surfaces and medical equipment within these facilities. Items such as ventilators, which assist with breathing, or catheters used for urinary drainage or intravenous access, can become reservoirs for the bacteria. The primary mode of transmission in hospitals is often through the hands of healthcare workers who may inadvertently carry the bacteria from a contaminated surface or one patient to another.
Common Infections and Symptoms
When Enterobacter bacteria move from the gut or environment into a susceptible part of the body, they can cause a range of infections. One of the more frequent types of infection is a urinary tract infection (UTI). Individuals may experience pain or a burning sensation during urination, an increased urge to urinate, and sometimes fever and flank pain if the infection spreads to the kidneys.
These bacteria are also a notable cause of hospital-acquired pneumonia, particularly in patients who are on mechanical ventilators. The symptoms of Enterobacter pneumonia include a productive cough, shortness of breath, chest pain, and fever. The presence of the bacteria in the lungs triggers an inflammatory response, leading to the accumulation of fluid and the characteristic symptoms of pneumonia.
Bloodstream infections, also known as bacteremia, can occur when Enterobacter enters the circulatory system. This can happen through a contaminated intravenous line or as a complication of another infection, such as a UTI or pneumonia. The symptoms of bacteremia can be severe and escalate quickly, including high fever, chills, a rapid heart rate, and a dangerous drop in blood pressure, a condition known as septic shock.
Surgical site and wound infections are another common manifestation of Enterobacter. After a surgical procedure, the incision site can become contaminated with the bacteria, leading to signs of infection. These symptoms are typically localized to the wound area and include redness, swelling, pain, warmth, and the production of pus. A fever may also develop, indicating a more systemic response to the infection.
Populations at Risk
Certain groups of people are more susceptible to Enterobacter infections due to underlying health conditions or medical treatments. Individuals who have a prolonged stay in a hospital, especially in an intensive care unit (ICU), are at a higher risk. Extended exposure to a hospital environment increases the chances of colonization and infection.
The use of invasive medical devices creates a direct pathway for bacteria to enter the body. Devices like urinary catheters, central venous catheters (lines placed in large veins), and endotracheal tubes for ventilation bypass the body’s natural physical barriers. This makes it easier for Enterobacter to establish an infection.
A person’s immune status also plays a part in their vulnerability. Patients with a compromised immune system, such as those undergoing cancer chemotherapy, individuals with HIV, or organ transplant recipients taking immunosuppressive drugs, have a reduced ability to fight off infections.
Other factors that increase risk include recent surgical procedures, which create a wound that can become infected, and prior or long-term use of broad-spectrum antibiotics. These antibiotics can also disrupt the normal balance of gut flora. This disruption can allow more resistant bacteria like Enterobacter to overgrow, increasing the risk of an infection.
Treatment and Drug Resistance
The primary approach to treating Enterobacter infections is the use of antibiotics. However, a challenge in managing these infections is the bacteria’s ability to resist many common antibiotics. Enterobacter species possess intrinsic resistance to certain types of antibiotics and can also acquire resistance through genetic mutations or by obtaining resistance genes from other bacteria.
This resistance is a major public health concern, particularly with the emergence of strains resistant to a class of powerful antibiotics called carbapenems. These strains are often referred to as Carbapenem-resistant Enterobacteriaceae (CRE), and infections with these organisms are difficult to treat, leaving limited therapeutic options.
Due to this widespread resistance, laboratory testing is an important part of treatment. Once Enterobacter is identified as the cause of an infection, susceptibility testing is performed. This process involves exposing the specific bacterial isolate to a panel of different antibiotics to see which ones are effective. The results guide the physician in selecting the most appropriate and effective antibiotic for that particular infection.