What is Klebsiella Pneumonia?
In 1882, a scientist named Carl Friedlander was the first to talk about a bacteria called Klebsiella pneumoniae. He found this bacterium in the lungs of people who had passed away from pneumonia, and originally, it was called Friedlander’s bacillus. It took four more years for this bacteria to be renamed as Klebsiella.
Klebsiella pneumoniae is a type of bacteria that can’t move on its own, is surrounded by a ‘shell’, and appears red under a microscope – a characteristic we call gram-negative. This bacterium is usually found in the natural environment and is sometimes seen in individuals with a history of heavy alcohol use or diabetes, often causing pneumonia. The bacterium usually settles on the moist surfaces of the throat and the digestive system. But once inside the body, it can cause serious illnesses and is often resistant to antibiotics.
Today, pneumonia caused by Klebsiella pneumoniae is the most frequently seen type of pneumonia contracted in hospitals in the United States. This bacterium is responsible for 3% to 8% of all bacterial infections acquired in a health care setting.
What Causes Klebsiella Pneumonia?
Klebsiella pneumoniae is a type of bacteria from the Enterobacteriaceae family. It is described as being ‘gram-negative’, meaning it doesn’t retain a certain stain used in lab tests, ‘encapsulate’, meaning it’s surrounded by a protective barrier, and ‘non-motile’, meaning it doesn’t move on its own. The harmfulness, or ‘virulence’, of the bacterium comes from several factors which can lead to infection and antibiotic resistance.
The protective barrier surrounding the bacteria, known as the capsular structure, is their most important defense mechanism. It lets the bacteria avoid defenses of the host organism, essentially protecting them from being engulfed and killed by the host’s immune system. There are as many as 77 different types of these capsular structures and the bacteria without them tend to be less harmful. Another major harmful factor is something called lipopolysaccharides, which cover the outer surface of the bacteria. The presence of lipopolysaccharides can trigger an inflammation response in the host, which is a major cause of complications in conditions like sepsis and septic shock.
Two other harmful factors include something called fimbriae, which allows the bacterium to latch onto host cells. In addition, the bacterium has a unique mechanism to obtain iron from the host body for its own growth with the help of siderophores, which is another factor causing the infection.
Klebsiella pneumoniae is also one of several bacteria experiencing a high rate of resistance to antibiotics. This happens when changes occur in the central genetic material of the bacteria. This resistance was first discovered in gram-negative organisms by Alexander Fleming in 1929. Since then studies showed that K. pneumoniae has developed an enzyme, known as beta-lactamase, which breaks down the component of certain antibiotics rendering them ineffective. Because of this resistance, other classes of antibiotics like carbapenems became a treatment choice. Unfortunately, 80% of the 9000 bacterial infections reported as resistant to carbapenem to the Centers for Disease Control and Prevention (CDC) in 2013 turned out to be K. pneumoniae.
This carbapenem resistance is connected to the increased activity in moving out harmful substances, changes in the outer membrane of the bacterium, and increased production of the beta-lactamase enzymes in the bacterium.
Risk Factors and Frequency for Klebsiella Pneumonia
Humans are the main carriers of K. pneumoniae, which is present in the stool and nasopharynx of 5% to 38% and 1% to 6% of the population, respectively. The bacteria are mostly found in a patient’s digestive tract or on the hands of hospital staff, and can cause outbreaks in hospitals. People of Chinese heritage and chronic drinkers are more likely to carry the bacteria. Among hospitalised patients, the rate of those carrying K. pneumoniae is much higher than in the general community. In certain studies, up to 77% of hospitalised patients were found to carry the bacteria in their stool, with the number increasing in correlation to the number of antibiotics prescribed.
Pneumonia caused by K. pneumoniae can be acquired in the community or in a hospital setting. While K. pneumoniae is a rare cause of pneumonia caught outside hospitals, it is responsible for an estimated 3%-5% of community-acquired pneumonia in Western countries. However, in developing regions such as Africa, it can be responsible for up to 15% of all pneumonia cases. Internationally, K. pneumoniae is accountable for roughly 11.8% of all hospital-acquired pneumonia. And among patients using a ventilator, between 8% and 12% get pneumonia from K. pneumoniae, compared to 7% of patients who aren’t on ventilators. Fatalities from this bacteria range from 50% to 100% in patients with alcoholism and blood infection.
Signs and Symptoms of Klebsiella Pneumonia
Pneumonia caused by K. pneumoniae shows similar symptoms to pneumonia that occurs naturally in the community. These symptoms include a cough, fever, chest pain that worsens while breathing (pleuritic chest pain) and difficulty in breathing. An interesting difference between pneumonia caused by Streptococcus pneumoniae and K. pneumoniae is the kind of sputum, or mucus, produced. If it’s Streptococcus pneumoniae, it’s usually “blood-tinged” or “rust-colored,” but K. pneumoniae results in a “currant jelly” like sputum. This is due to the significant inflammation and tissue damage that K. pneumoniae causes.
Klebsiella pneumonia typically affects the upper parts of the lungs, but it can also extend to the lower parts. During an examination, the doctor usually notices signs of lung consolidation (when the tiny air spaces in the lungs fill with sputum). These signs might include crackling sounds, bronchial breathing, and increased vocal resonance, mainly in the upper lung. It’s particularly important to look for burn sites, wounds, and invasive devices that might be a source of infection in hospital-acquired cases.
Certain risk factors can make someone more susceptible to a K. pneumoniae infection, including:
- Being admitted to an intensive care unit
- Long-term use of invasive devices
- Inefficient infection control practices
- Weakened immune systems, especially in people who are alcoholics or have diabetes
- Long-term use of broad-spectrum antibiotics
The bacteria typically get into the host either directly (as in a wound) or through aspiration, which is when substances such as food or saliva accidentally enter the airways.
Testing for Klebsiella Pneumonia
In simpler terms, when your doctor suspects you might have pneumonia, they’ll conduct a series of laboratory tests. Often, they look for a higher than normal white blood cell count, which usually suggests an infection. However, this information alone doesn’t tell them what specific organism like bacteria or virus, caused the infection.
Another way to diagnose pneumonia is by using chest X-rays. This can help your doctor further narrow down the possible causes of your pneumonia. For example, pneumonia caused by a specific bacteria called Klebsiella pneumoniae typically shows up as a certain pattern of infection in the back area of your right upper lung.
Klebsiella pneumoniae pneumonia hardly ever results in lung abscesses (pockets of pus), but it can often be linked with empyema, a condition where pus fills the space between the lung and the chest wall. On a chest X-ray, another sign that might point towards this type of pneumonia is the “bulging fissure sign”. This refers to a specific X-ray feature caused by a large amount of infection and inflammation. However, these specific X-ray findings are not exclusive to Klebsiella pneumoniae pneumonia and can be seen in pneumonia caused by other organisms too.
In the end, to confirm whether your pneumonia is caused by Klebsiella pneumoniae, the doctors will need to do a sputum (mucus from the lungs) or blood culture test. These tests allow them to identify the specific bacteria in your system.
Treatment Options for Klebsiella Pneumonia
When a person gets pneumonia, doctors usually follow standard guidelines for antibiotic treatment. However, if there’s a suspicion or confirmation of the bacteria, Klebsiella pneumoniae, involved, the treatment becomes more specific and is based on local antibiotic suitability. Klebsiella pneumoniae is not common outside of hospital settings.
Typically, a 14-day course of specific antibiotics, like a third or fourth-generation cephalosporin, or a respiratory quinolone, is used. Sometimes, this treatment is combined with another antibiotic called an aminoglycoside. For those who are allergic to penicillin, aztreonam or a respiratory quinolone can be substituted. If the pneumonia was acquired in a hospital environment (nosocomial infection), a different antibiotic called carbapenem might be used initially until further test results are available.
Things get more complicated if the Klebsiella pneumoniae is an ESBL or CRE type. ESBL stands for Extended-Spectrum Beta-Lactamases and CRE stands for Carbapenem-Resistant Enterobacteriaceae. These are scientific terms for strains of bacteria that are resistant to many antibiotics, making them harder to treat. If the infecting bacteria is an ESBL type, carbapenem is usually the chosen antibiotic because it is mostly effective for it globally. On the other hand, if the bacteria is a CRE type, the treatment has to be guided by an infectious disease specialist. Several options may be considered, including antibiotics from the polymyxin class, tigecycline, fosfomycin, aminoglycosides, or dual therapy carbapenems. In some cases, using a combination of two or more of these antibiotics might lead to a better outcome than using just one.
What else can Klebsiella Pneumonia be?
When a doctor is diagnosing pneumonia caused by K. pneumoniae, they should also consider the possibility of the following conditions:
- Community-acquired and hospital-acquired pneumonia caused by other organisms, such as Staphylococcus, Pneumococcus, Pseudomonas, Acinetobacter, and Legionella
- Tuberculosis
- Aspergillus infection
- Cancer in the lungs (Malignancy)
- Acute respiratory distress syndrome (ARDS)
- Lung abscess
- Empyema and other infections in the pleura and lungs
It’s important that doctors consider all of these potential diseases when diagnosing a patient.
Surgical Treatment of Klebsiella Pneumonia
In some patients suffering from lung abscess, empyema (a condition where pus collects in the space between the lungs and the inner surface of the chest wall), and lung gangrene (death of lung tissue), there may be a need for surgical intervention. This often comes in the form of surgical debridement or drainage. Debridement is a procedure to remove dead, damaged, or infected tissue to improve the healing potential of the remaining healthy tissue. Drainage refers to a procedure to remove excess fluid, such as pus from an infected area.
What to expect with Klebsiella Pneumonia
The outlook for Klebsiella pneumonia, a type of lung infection, tends to be quite unfavorable. Particularly, patients who have issues with alcohol use, diabetes, hospital-acquired infections, or bloodstream infections tend to have poorer outcomes. Over 50% of people with this type of pneumonia unfortunately don’t survive.
Possible Complications When Diagnosed with Klebsiella Pneumonia
Pneumonia due to K. pneumoniae is not a simple condition. It can lead to several complications including:
- The bacteria entering the blood, a condition called bacteremia
- Formation of an abscess, or a pocket of pus, in the lungs
- Creating a condition called empyema, which is a collection of pus in the space between the lungs and the inner surface of the chest wall.
