What is Staphylococcal Pneumonia?
Staphylococcus aureus (S. aureus) is a type of bacteria that’s been studied since the 1800s. Back then, it was mainly known for causing blood infections (sepsis) and abscesses (pockets of pus in the body). But over the past century, we’ve discovered that this bacteria is responsible for many different diseases, including a type of pneumonia.
What makes S. aureus especially problematic is its ability to produce certain enzymes and proteins, which can make it resistant to antibiotics. Specifically, it can produce substances like protease, lipase, and hyaluronidase. Moreover, it can produce a unique protein called penicillin binding protein 2A (PBP-2A) via the mecA gene. This capability is what led to the creation of a particularly stubborn strain of S. aureus known as methicillin-resistant Staphylococcus aureus (MRSA). This strain is extremely hard to treat because it’s resistant to both older and newer antibiotics.
What Causes Staphylococcal Pneumonia?
Staphylococcal pneumonia, a type of lung infection, is often seen in people who are recovering from the flu. It’s more common in very young and very old people. However, it’s important to remember that pneumococcus, a different kind of bacteria, is still the leading cause of pneumonia after a viral infection in these age groups.
People can also get this type of lung disease if they are carriers of staphylococcus bacteria on their skin or in their noses. This is true both for people in the community and for people in the hospital. This lung disease can also occur in people who misuse intravenous drugs. The bacteria can contaminate the skin or the equipment used to inject the drugs and lead to many different types of infections throughout the body. These can include infections of the heart’s tricuspid valve (a condition known as tricuspid valve endocarditis), bloodstream infections (bacteremia), and infections that travel (septically) to the lungs.
Risk Factors and Frequency for Staphylococcal Pneumonia
When we talk about S. aureus, a type of bacteria, it’s important to note that there are two different types – methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-susceptible Staphylococcus aureus (MSSA). These two types require different treatments. According to a large study, 3% of hospital patients with community-acquired pneumonia (CAP), a lung infection that can occur in normal, daily life, developed the infection because of MRSA. It was found that whether the infection was caused by MRSA or MSSA depended on where the patient lived.
- Of the S. aureus infections, 51% were due to MRSA and 49% were due to MSSA.
- In another study focused on hospital patients with CAP in the US, it was found that 1.7% of the cases were due to S. aureus.
- Out of these, 0.7% were because of MRSA, and 1% were due to MSSA.
Signs and Symptoms of Staphylococcal Pneumonia
S. aureus is a type of bacteria that can lead to many different types of infections. As a result, doctors need to perform a thorough check-up and consider multiple potential causes when patients show signs of an S. aureus infection. They need to pay attention to when symptoms began, how long symptoms have lasted, and whether there are other symptoms like fever, chills, shortness of breath, or coughing up mucus. Many people with pneumonia (around 80%) have a fever, but older people may not. Asking about recent contacts with sick people, travels, recent flu infections, jobs, and recent hospital stays can also help doctors figure out who might be more likely to get S. aureus pneumonia.
Additionally, doctors need to consider whether the patient uses intravenous drugs since this can lead to a heart infection called tricuspid valve endocarditis. This can cause septic emboli (infected blood clots) to reach the lungs and cause S. aureus pneumonia. During the physical check-up, doctors should pay special attention to the heart and lungs to spot signs of heart murmurs, difficulty breathing, rapid breathing, or abnormal sounds in the lungs. The physical exam may also include techniques like percussion and tactile fremitus if doctors suspect a condition called pleural effusion, where there is excess fluid around the lungs. However, it’s worth noting that there are no specific set of symptoms and physical findings that can confirm a diagnosis of pneumonia. These examinations can only help heighten the suspicion of pneumonia.
Testing for Staphylococcal Pneumonia
If your doctor suspects you might have pneumonia caused by a staphylococcus infection, they will start the investigation in the same manner as if they were looking for any type of community-acquired pneumonia (CAP). This usually begins with a complete blood count (CBC) test, which often shows a high number of white blood cells with a dominance of a type called neutrophils.
The most reliable method for diagnosing pneumonia, assuming there are relevant symptoms, is a chest X-ray revealing an abnormality called an infiltrate. This infiltrate can appear in a whole lobe of the lung or, in severe cases, show hollow areas or fluid-filled pockets (empyema). Sometimes, the X-ray doesn’t show anything despite pneumonia symptoms. In these instances, your doctor might order a computed tomography (CT) scan for a more detailed look at your lungs.
A CT scan can generally pick up signs of pneumonia which weren’t visible on a standard chest X-ray, like an infiltrate or hollow lesion. Your doctor might request a sample of your sputum (mucus you cough up), which can give more guidance on the best antibiotics for your treatment. However, not everyone can provide a good enough sputum sample for testing. On the other hand, when a good sample is obtained, the majority of the time it gives useful information for treatment.
Your doctor might also test for MRSA, a type of staph bacteria, using a swab to check if you’re a carrier. This information can help support their suspicion of pneumonia being caused by this bug. Another test that may be done at the start of treatment is procalcitonin. This can give an idea of how effective the antibiotics are and also help in controlling unnecessary antibiotic use, which can be harmful.
Treatment Options for Staphylococcal Pneumonia
When treating pneumonia caused by the staph bacteria, doctors will determine whether the infecting bacteria is MRSA (a type that is resistant to many antibiotics) or MSSA (a more common type which is not resistant to most antibiotics).
If it turns out to be MRSA, doctors will usually prescribe either vancomycin or linezolid at the start of treatment which will be stopped if it’s later found that MRSA isn’t present. Both of these antibiotics work equally well, and the final choice depends on what the patient can tolerate, whether they have any allergies to antibiotics, their kidney function, and their ability to internally process the drug.
If the patient has trouble with intravenous access (getting medication through a vein), linezolid is preferred as it is effective in its oral form (as a pill). On the other hand, vancomycin is a better choice if the patient has low levels of certain blood cells or if they are already taking medications called selective serotonin reuptake inhibitors (SSRIs), which are often used to treat depression.
There are other options (like ceftaroline and clindamycin) if vancomycin or linezolid can’t be used, although they are not approved for certain types of pneumonia caught while in hospital and might be less effective.
If test results show that MSSA is the cause of pneumonia (and no other bacteria are present), doctors would then ‘de-escalate’ the treatment, meaning they would switch to less powerful antibiotics like nafcillin, oxacillin, or cefazolin.
In addition to antibiotics, other types of supportive measures can also help to manage pneumonia caused by the staph bacteria. For example, bronchodilation (using medication to open up airways) can help those with existing lung diseases like asthma or COPD manage their symptoms. Some patients might require additional oxygen due to restricted lung function caused by pneumonia. This can be given through a nasal tube, but in severe cases, a breathing machine (mechanical ventilator) may be necessary.
What else can Staphylococcal Pneumonia be?
If lung conditions like staphylococcal pneumonia are suspected, the symptoms can often be broad and quite general. This makes it important to consider various other conditions that may be responsible. The list of other possible causes of the symptoms could include:
- Other types of pneumonia due to various bacteria and viruses such as:
- Streptococcal pneumonia
- Haemophilus influenza
- Mycoplasma pneumonia
- Chlamydia pneumonia
- Legionella
- Gram-negative bacilli
- Group A Streptococcus
- Anaerobic infection
- Mycobacterium tuberculosis
- Viral infection
- Fluid in the lungs due to congestive heart failure (pulmonary edema)
- Bleeding in the lungs (pulmonary hemorrhage)
- Partial collapse of the lung (atelectasis)
- Inflammation of the lungs due to inhaling foreign substances or chemicals (Pneumonitis)
- Diseases that affect the tissue and space around the air sacs of the lungs (Interstitial lung disease)
- Adverse reaction to a drug
- A blockage in one of the pulmonary arteries in the lungs (pulmonary embolism)
What to expect with Staphylococcal Pneumonia
The outlook for someone with staphylococcal pneumonia largely depends on their overall health, any pre-existing lung conditions they have, and complications related to this disease. The prognosis may become more serious if the infection enters the bloodstream. This emphasizes the importance of timely detection and accurate treatment with suitable antibiotics.
Possible Complications When Diagnosed with Staphylococcal Pneumonia
One serious issue that can come up with staphylococcal pneumonia, a type of pneumonia caused by a staph infection, is that it could lead to severe necrotizing pneumonia. This grave condition can sometimes be found in cases of a specific type of staph infection, known as community associated-MRSA (CA-MRSA). If health professionals suspect this, they might use a chest CT scan to look deeper into the problem.
However, it’s important to stress that a chest CT is not the first step for diagnosing pneumonia. Initially, doctors should order a simple chest x-ray to start their evaluation of pneumonia. Staphylococcal pneumonia can lead to severe health problems including sepsis, a serious infection that spreads through the body, septic shock, a potentially deadly condition where your blood pressure drops dangerously low, an infection in the blood known as bacteremia, and respiratory failure that would necessitate the use of a machine to help you breathe.
The common complications include:
- Serious necrotizing pneumonia
- Sepsis – a severe body-wide infection
- Septic shock – a life-threatening condition linked to low blood pressure
- Bacteremia – bacteria present in the bloodstream
- Respiratory failure which may require mechanical ventilation
Preventing Staphylococcal Pneumonia
It’s important that patients understand how community-acquired pneumonia (CAP) – a type of lung infection – might appear when they’re not in hospital. Understanding the signs of this infection can help them get a quicker diagnosis and treatment, especially if they might have staphylococcal pneumonia – an intense form of pneumonia caused by a specific bacteria. Quick and early treatment with antibiotics can help fight off this infection before it causes serious health problems like sepsis (the body’s extreme response to an infection), bacteremia (bacteria in the bloodstream), or respiratory failure (when lungs can’t give the body the oxygen it needs).