What is Nosocomial Pneumonia?
Nosocomial pneumonia, also known as hospital-acquired pneumonia (HAP), happens when someone gets pneumonia after being in the hospital for more than 48 hours. This condition wasn’t present when they were admitted. There is a certain type of HAP that happens in intensive care units (ICUs) called Ventilator-associated pneumonia (VAP) that develops after 48 to 72 hours of being on a breathing machine (known as tracheal intubation). It is believed to affect 10% to 20% of patients who are on a ventilator for more than 48 hours.
What Causes Nosocomial Pneumonia?
The typical bacteria that cause HAP and VAP, which are types of pneumonia caught in hospital, include types that are aerobic gram-negative bacilli (such as Pseudomonas aeruginosa, Escherichia coli, Klebsiella pneumoniae, Enterobacter, and Acinetobacter) and gram-positive cocci (like Staphylococcus aureus, which includes a drug-resistant version called MRSA, and Streptococcus). The bacteria causing the infection can vary due to the patient’s health and the types of bacteria present in a particular hospital.
Several risk factors can make a person more likely to contract VAP that is resistant to multiple medicines. These can include being in septic shock at the time VAP develops, having ARDS (a severe lung condition) before VAP starts, having used IV antibiotics in the 90 days leading up to VAP, being in the hospital for more than five days before VAP occurs, and needing kidney treatment before VAP starts.
Risk factors for getting HAP that’s resistant to many drugs include having used IV antibiotics in the 90 days leading up to HAP.
For both VAP and HAP caused by MRSA or Pseudomonas that’s resistant to multiple drugs, a major risk factor is having used IV antibiotics in the 90 days leading up to the pneumonia.
Risk Factors and Frequency for Nosocomial Pneumonia
Hospital-Acquired Pneumonia (HAP) is quite common, with 5 to 10 cases reported for every 1000 hospital admissions. This makes it the most frequent type of hospital-acquired infection in both Europe and the United States. Particularly in Intensive Care Units (ICUs), over 90% of pneumonia cases occur in patients who are intubated and on mechanical ventilation.
Signs and Symptoms of Nosocomial Pneumonia
People with this condition may display a variety of symptoms and signs. Symptoms can include coughing, producing phlegm, a rise in body temperature, chest pain, or difficulty breathing. The signs that doctors look out for are fever, rapid breathing, consolidations seen on a chest x-ray, or distinctive sounds called crackles that are heard in the lungs through a stethoscope.
- Coughing
- Producing phlegm
- Rise in body temperature
- Chest pain
- Difficulty breathing
- Fever
- Rapid breathing
- Consolidations seen on chest x-ray
- Crackles heard in the lungs
Testing for Nosocomial Pneumonia
Diagnosing hospital-acquired pneumonia (HAP) can be challenging. Nevertheless, the Infectious Diseases Society of America/American Thoracic Society’s guidelines provide some clarification. They suggest that new lung infiltration and clinical symptoms like fever, an increase in white blood cells, coughing up green or yellow mucus, and worsening oxygen levels might suggest HAP. The Clinical Pulmonary Infection Score (CPIS), which evaluates clinical symptoms and radiological (imaging) findings, can also help identify pneumonia. However, some experts raise the concern that CPIS isn’t entirely precise and might lead to overuse of antibiotics.
For patients with ventilator-associated pneumonia (VAP, a specific type of pneumonia that occurs in people on ventilators), getting cultures from the lower parts of the lungs can be essential. Several methods are available:
- Blind tracheobronchial aspiration: A flexible tube is inserted into the trachea (the windpipe) via the endotracheal tube (a tube placed in the windpipe through the mouth or nose). However, this method can yield both false positives and false negatives due to potential sample contamination and lack of specific site sampling.
- Bronchoscopy with bronchoalveolar lavage: In this process, a small camera is inserted into the lungs to wash out and sample specific lung segments, leading to less chance of a false negative. The downsides are potential contamination and possible worsening of oxygen levels in some patients.
For patients with HAP, who are not on ventilators, sputum (a mixture of saliva and mucus coughed up from the lungs) samples can be obtained through natural coughing, induced coughing, or nasotracheal suctioning (suctioning up mucus from the nose and throat) if the patient can’t cough out a sample. All samples from the respiratory tract should then be examined under a microscope and cultured.
Microscopic analysis helps identify possible disease-causing organisms and guide the choice of antibiotics until the culture results are known. The presence of a high number of neutrophils (a type of white blood cell) and the form and structure of bacteria can hint at the likely culprit organism.
Diagnostic “thresholds” or levels have been established for different types of samples: 1,000,000 colony forming units (CFU) per milliliter (mL) for endotracheal aspirates, 10,000 CFU/mL for bronchoscopic samples, and 1,000 CFU/mL for protected specimen brushings.
There are also new molecular tests, such as the multiplex polymerase chain reaction assay that can identify numerous bacterial pathogens and numerous antibiotic resistance genes. This can help in quickly identifying the infectious organism and guiding the appropriate choice of antibiotic treatment.
Treatment Options for Nosocomial Pneumonia
The initial treatment for hospital-acquired pneumonia (HAP) and ventilator-associated pneumonia (VAP) should include medication that can fight off bacteria such as Staphylococcus aureus (a bacteria that can cause skin infections) and Pseudomonas aeruginosa (a bacteria that can cause severe illnesses), as well as other similar types of bacteria. The specific antibiotic used should be chosen based on the most common diseases and how receptive they are to different antibiotics. This selection should also take into account the risk of antibiotic resistance due to factors specific to the healthcare facility and patient.
Patients with HAP who are at risk of getting a MRSA (Methicillin-resistant Staphylococcus aureus) infection, such as those who have recently been given intravenous antibiotics, or are being treated in a unit with a high prevalence of MRSA, may require specific antibiotics like vancomycin or linezolid. This is particularly important for patients at high risk of death such as those needing mechanical ventilation due to pneumonia or who have a severe infection.
For HAP patients without risk factors for MRSA and not at high risk of death, doctors prescribe an antibiotic that treats Methicillin-sensitive Staphylococcus aureus (MSSA) like piperacillin-tazobactam, cefepime, levofloxacin, imipenem, or meropenem.
If a patient with HAP is at a high risk for Pseudomonas or other gram-negative bacterial infection, doctors often prescribe antibiotics from two different classes to fight P. aeruginosa. On the other hand, patients who aren’t at a high risk may be given a single antibiotic effective against P. aeruginosa such as piperacillin-tazobactam, cefepime, ceftazidime, levofloxacin, ciprofloxacin, imipenem, meropenem, amikacin, gentamicin, and aztreonam.
Patients with HAP or VAP need to be assessed again after the initial antibiotic therapy to see how they’re responding to the treatment. The decision to continue, narrow, or expand the antibiotic therapy depends upon the patient’s response to the treatment and the specific bacteria causing the infection.
The duration of antibiotic therapy usually doesn’t exceed seven days for most patients with HAP or VAP as it has been found equally effective as longer durations and can limit the development of drug-resistant bacteria. However, patients with severe illness, bloodstream infection, slow response to treatment, weakened immune system, and complications like empyema (pus in lungs) or lung abscess may need a longer duration of treatment.
What else can Nosocomial Pneumonia be?
Here are some conditions and infections that a doctor may consider when examining a patient, and they include:
- Acinetobacter infection
- Adenovirus infection
- Bacterial sepsis
- Burn wound infections
- Clostridioides infection
- Colitis
- Croup
- Enterobacter infections
- Enterococcal infections
- E-coli infections
What to expect with Nosocomial Pneumonia
Many research studies have shown a link between Hospital-Acquired Pneumonia (HAP) and a higher risk of death. When looking at all causes of death related to Ventilator-Associated Pneumonia (VAP), the rates vary between 20% and 50% in different studies.
There are a number of factors that can increase the risk of death, these include:
- The seriousness of the patient’s illness at the time they are diagnosed. This could include things like shock, coma, respiratory failure, or Acute Respiratory Distress Syndrome (a severe lung condition that causes low oxygen levels in the blood).
- Bacteremia, which is a condition where bacteria is present in the bloodstream.
- Any underlying health conditions the patient may have.
