What is Enterobacter Infections?
Enterobacter is a type of bacteria that are mainly related to infections received in healthcare settings. There are 22 types of Enterobacter, but not all of them cause diseases in humans. Due to these bacteria, hospital-acquired and less commonly, community-acquired infections can occur. These can lead to varying conditions such as urinary tract infections, respiratory infections, soft tissue infections, bone infections, and heart valve infections, among others. Some types of Enterobacter reside naturally in the digestive system of mammals, while others can be found on human skin surfaces, in water, certain foods, soil, and sewage.
From the 1970s, it was understood that Enterobacter could cause in-hospital infections. The National Infection Surveillance System identifies Enterobacter as a common bacteria found in samples taken from respiratory mucus, surgical wounds, and blood, specifically in intensive care units.
The growing issue is that Enterobacter has become increasingly resistant to many previously effective antibiotics. In fact, in 2017, the World Health Organization placed certain resistant types of these bacteria on a critical list, signifying an urgent need to develop new antibiotics.
What Causes Enterobacter Infections?
Enterobacter is a type of bacteria that is part of the Enterobacteriaceae family. This bacteria is rod-shaped and can live with or without oxygen. It doesn’t produce spores, has whiplike tails called flagella for movement, produces an enzyme called urease, and can ferment lactose, a type of sugar.
Enterobacter can cause illnesses depending on various factors. Similar to other types of bacteria found in the gut, Enterobacter uses adhesins, substances that help them stick to cells in the host. It also has a special outer cover called a lipopolysaccharide (LPS) capsule which helps it to avoid being ingested and destroyed by the body’s immune cells. This LPS cover can also trigger intense inflammation in the host cell and may even progress to a serious condition called sepsis where the body’s response to infection causes injury to its own tissues and organs.
Enterobacter species have a specific way of resisting antimicrobial treatments. They produce an enzyme called beta-lactamases that can break down antibiotics like penicillin and cephalosporins which possess a structure called a beta-lactam ring. This ability of the bacteria has led to an increase in the number of Enterobacter pathogens that are resistant to antibiotics.
Risk Factors and Frequency for Enterobacter Infections
According to various studies, Enterobacter, a type of bacteria, was responsible for roughly five to seven percent of infections caught in hospitals in the United States from 1976 to 1989. This bacteria was particularly common in intensive care units (ICUs), where it was found to be one of the top five most common causes of infection in several areas including the respiratory tract, surgical wounds, the urinary tract, and the bloodstream.
Between 1995 and 2002, a project called the Surveillance and Control of Pathogens of Epidemiologic Importance (SCOPE) looked at around 24,179 cases of infections caught in hospitals in the United States. In this study, Enterobacter was found in 4.7% of infections in the ICU and 3.1% of infections in other hospital wards. It was the fifth most common bacteria found in ICU and the eighth most common in other wards.
- Enterobacter was responsible for about 5-7% of infections caught in hospitals in the U.S from 1976-1989.
- It was one of the top five most common causes of infection in ICUs, affecting areas like the respiratory tract, surgical wounds, urinary tract, and bloodstream.
- From 1995-2002, Enterobacter was found in 4.7% of infections in the ICU and 3.1% of infections in non-ICU wards, making it one of the most common hospital-acquired bacteria.
Signs and Symptoms of Enterobacter Infections
Enterobacter infections can lead to a variety of health problems. The most common issues include bloodstream infections, lung infections, urinary tract infections, infections at surgical sites, and infections linked to intravascular devices. Less commonly, these bacteria can cause hospital-acquired meningitis, sinusitis, and bone infections. Symptoms can be very similar to other infections caused by certain types of bacteria, making them hard to distinguish.
A bloodstream infection with Enterobacter, also known as bacteremia, is commonly accompanied by fever. Other signs can include body-wide inflammation, low blood pressure, shock, and an increase in white blood cells, similar to other types of bloodstream infections.
Pneumonia caused by Enterobacter often presents with a cough and shortness of breath. These symptoms might be accompanied by noticeable changes in a chest X-ray. Urinary tract infections caused by Enterobacter may result in painful urination, as well as frequent and urgent urination, and might be detected through a urine test showing signs of infection.
There are certain risk factors that may increase the chances of getting an Enterobacter infection. These include:
- Long-term use of antibiotics
- Weak immune systems, especially due to conditions like cancer or diabetes
- Having invasive medical devices implanted
- Being admitted to the intensive care unit
- Recent hospitalization or underwent invasive medical procedures
Testing for Enterobacter Infections
The best way to diagnose Enterobacter infections, a type of bacterial infection, is through culture tests. Doctors usually recommend getting two sets of these cultures – one for testing the presence of organisms that need air to grow (aerobic), and another for those that don’t need air (anaerobic). MacConkey agar, a kind of growth medium, is used to find out if the bacteria can break down lactose, a type of sugar.
Additionally, indole tests can be done. These tests can tell the difference between certain types of bacteria that can’t produce indole, like Klebsiella and Enterobacter, and those that can, like E. Coli. It’s worth noting that Enterobacter bacteria can move around, unlike Klebsiella bacteria that stay still.
Other important lab tests that can help with the diagnosis include:
- Gram stain: This test helps in rapid identification of bacteria before the results of culture tests are available.
- Complete blood count: This test gives an overall picture of your health by measuring different components in your blood.
- Complete metabolic panel: This test checks for any problems with your body’s metabolism, which is the process of converting food into energy.
- Urinalysis with culture: This test looks for bacteria or other signs of disease in your urine.
Imaging tests that focus on the specific organ system involved could also provide valuable information that can guide treatment.
Treatment Options for Enterobacter Infections
Bacteria becoming resistant to antibiotics is a growing concern, especially regarding Enterobacter infections. However, there are several options for treatment, which include medicines such as carbapenems, beta-lactams, beta-lactamase inhibitors, fluoroquinolones, aminoglycosides, and sulfamethoxazole/trimethoprim.
First and second-generation cephalosporins are usually not successful in treating Enterobacter infections. Treatment with a third-generation cephalosporin might work in some cases, but use of this drug category can lead to stronger, multi-resistant infections. This is because these drugs often trigger Enterobacter to produce more of an enzyme called AmpC beta-lactamase, making the bacteria more resistant. Based on this, third-generation cephalosporins are not recommended for severe Enterobacter infections especially for certain strains like Enterobacter cloacae and Enterobacter aerogenes.
Fourth-generation cephalosporins, which are another class of antibiotics, are seen as an acceptable treatment option if the bacterium hasn’t developed a resistance mechanism known as Extended-Spectrum beta-lactamase or ESBL. ESBL is a type of enzyme that can break down certain antibiotics, making them ineffective.
Carbapenems, another group of antibiotics, are generally very effective against serious, multi-drug resistant Enterobacter infections. That being said, recently there’s been an increase in resistance to these antibiotics too due to certain enzymes in the bacteria.
If a patient has an infection resistant to carbapenems (known as CRE), there are other treatment options that include polymyxins, tigecycline, fosfomycin, and even a double dose of different carbapenems. Due to increases in resistance, combining two or more different antibiotics is often more effective than just one, particularly in severe cases such as septic shock or rapidly progressing disease.
For serious CRE bloodstream infections, a treatment plan including colistin has been found to be useful. However, the use of colistin is also seeing an increase in resistance. Therefore, for colistin-resistant CRE, treatments including tigecycline or a combination of two different carbapenems are recommended. It is important to note, however, that medications like colistin and aminoglycosides can be harmful for those with kidney disease.
In cases of CRE Urinary Tract Infections (UTIs) where patients are not critically ill, aminoglycosides and fosfomycin can be used. However, for critical cases, a combination therapy of carbapenem, along with colistin or aminoglycoside, can be used.
After the patient has improved, intravenous antibiotics can be replaced with oral antibiotics like fluoroquinolones or sulfamethoxazole/trimethoprim, and the patient can continue the treatment at home. Nevertheless, the treatment for CRE is complicated and highly variable, often requiring multiple different medications. Researchers are still studying experimental drugs as resistance continues to be an issue.
What else can Enterobacter Infections be?
When diagnosing an Enterobacter infection, doctors also consider other health conditions that could cause similar symptoms. These include:
- Sepsis, which can be caused by other types of bacteria
- Acute Respiratory Distress Syndrome (ARDS)
- Pneumonia or lung inflammation due to inhaling food, stomach acid, or saliva into the lungs
- Pneumonia caused by viruses or other bacteria
- Excess fluid around the lungs, also known as parapneumonic pleural effusion
- Abscess in the lung
- Empyema, which is pus in the space between the lung and the chest wall
- Urinary tract infections
- Bacterial prostatitis, which is an infection in the prostate gland
- Cellulitis, a common skin infection
- Osteomyelitis, an infection in the bone
What to expect with Enterobacter Infections
The death rate for Enterobacter infections, a type of bacterial infection, is generally high. According to a research study by Kang and his colleagues, even among those who received the correct antibiotics, just under a quarter (24.6%) unfortunately died. In individuals who had particularly tough strains of Enterobacter that were resistant to common antibiotics like cephalosporin, the death rate was even higher, at 34.7%.
Similar death rates have been observed in Enterobacter infections where the bacteria led to conditions like pneumonia (a serious lung infection), urinary tract infections (infections in parts of the body that make, store, or get rid of urine), and soft tissue infections (infections in tissues that connect, support, or surround other structures and organs of the body).
Possible Complications When Diagnosed with Enterobacter Infections
Infections caused by Enterobacter species can lead to dangerous complications like sepsis and septic shock, which are conditions of severe infection that can affect the entire body. If Enterobacter infects the lungs, it can cause pneumonia and possibly even a lung abscess, a pocket of pus inside the lung tissue. It may also lead to parapneumonic pleural effusion, a condition where excess fluid builds up between the layers of tissues that line the lungs and chest cavity. Empyema, a collection of pus in the space between the lung and the chest wall, is another potential complication. These infections can also result in ARDS, which stands for Acute Respiratory Distress Syndrome, a serious condition that can cause breathing difficulty.
Conditions from Enterobacter Infections:
- Sepsis, when infection spreads throughout the body
- Septic shock, a life-threatening condition that happens when blood pressure drops to a dangerously low level after infection
- Pneumonia, a lung infection
- Lung abscess, a pus-filled cavity in the lung
- Parapneumonic pleural effusion, an accumulation of excess fluid in the chest cavity
- Empyema, a collection of pus between the lung and chest wall
- ARDS (Acute Respiratory Distress Syndrome), a severe lung condition causing shortness of breath
Preventing Enterobacter Infections
It’s often helpful to steer clear of certain risk factors whenever possible, like avoiding the unnecessary use of medical devices or antibiotics when they’re not needed. These precautions might assist in preventing infections caused by Enterobacter from taking hold or getting worse. Enterobacter is a type of bacteria that can cause infections.
