Anaerobes in Pleuropulmonary Infections: An Overview

Introduction:

Anaerobic bacteria are normal components of human flora but can change into opportunistic pathogens that can cause serious infections. Pleuropulmonary infections play a significant role in these infections. This article mainly focuses on the anaerobes in pleuropulmonary infections.

What Are Anaerobes?

Anaerobic bacteria are organisms that can grow and survive without oxygen. Anaerobic bacteria are normally present in the body, particularly in the mouth, stomach, and respiratory tract. They are usually harmless and may even help prevent dangerous bacteria from colonizing. Under certain conditions, the same anaerobic bacteria have the potential to become pathogenic and cause respiratory infections. These conditions may include the following.

• Smoking.

• Alcohol abuse.

• Bad oral hygiene.

• Prolonged hospitalization.

• Weakened immune system.

• Cancer.

• Long-term lung diseases.

• Aspiration of oropharyngeal contents (material from mouth and throat inhaled into lungs leads to infection)

• Inappropriate antibiotic use.

Anaerobic bacteria are the major contributors to respiratory infections such as lung abscesses, empyema, and pneumonia.

What Are Pleuropulmonary Infections?

Pleuropulmonary infections refer to various diseases affecting the lungs (pulmonary) and the lining around the lungs (pleural cavity). Anaerobic bacteria cause these diseases. Some examples of pleuropulmonary infection are:

1. Aspiration Pneumonia: Aspiration pneumonia occurs when a significant quantity of material (food, saliva, or vomit) is inhaled into the lungs through the mouth or throat. This inhaled material can cause infection in the lungs. Patients with aspiration pneumonia may show evidence of alcoholism, pharyngeal dysfunction (trouble swallowing), or gum disease.

Symptoms: Symptoms usually take longer to appear. Cough with mucus containing pus (purulent sputum) and fever are common symptoms of aspiration pneumonia.

Complications: If the infection lasts longer than seven to ten days, lung abscess and empyema may develop.

Prognosis: Aspiration pneumonia can be treated better if appropriate antibiotics are taken early; they prevent infection and prevent complications.

2. Necrotizing Pneumonia: Necrotizing pneumonia is a severe lung infection characterized by necrosis (tissue death) and pus formation in the lung parenchyma (the functional tissue of the lung). Risk factors include gum disease and a weakened immune system.

Symptoms: Patients may present severe symptoms such as:

• High fever.
• High white blood cell count.
• Purulent sputum.
• Weight loss.
• Anemia.

Complications: Infection may start in one lung area ( localized involvement) but frequently spreads to involve multiple lobes(multilobular involvement). Emphysema or accumulation of pus surrounding the lung is another complication of necrotizing pneumonia.

Prognosis: Even with antibiotic use, the death rate from necrotizing pneumonia is high, up to 20 percent. This indicates a significant number of people with this infection do not survive even with treatment.

3. Lung Abscess: A lung abscess is a localized collection of pus within the lung tissue. Individuals who have untreated anaerobic pneumonitis are at increased risk of developing lung abscesses. Most lung abscesses are polymicrobial, indicating that different kinds of bacteria are involved. On the other hand, they can also be caused by single bacteria such as Klebsiella species, streptococcus, and Staphylococcus aureus.

Symptoms: Patients with lung abscesses may present the following symptoms:

• Fever that comes and goes.

• Weight loss.

• Anemia.

• Foul-smelling mucus.

• Occasionally coughing up blood.

Prognosis: The condition can be serious. Some studies have shown that even with appropriate care, there is a 20 percent death rate.

4. Empyema: Empyema is the collection of pus in the pleural cavity, the area between the lungs and chest wall. Various bacteria, including anaerobic bacteria alone or a combination of anaerobic and aerobic bacteria, can cause it.

Symptoms: It may present symptoms similar to lung abscesses and develop over at least two weeks.

• Cough.

• Fever.

• Weight loss.

• Difficulty breathing.

• Chest pain.

Prognosis: Depending on host factors, the mortality rate of patients diagnosed with empyema ranges from two percent to 70 percent.

How Are Anaerobic Pleuropulmonary Infections Diagnosed?

Diagnosis of anaerobic pleuropulmonary infections is challenging due to the difficulty in obtaining reliable samples and the limitations of some tests.

1. Sputum Examination: Sputum or regular coughed-up mucus is not a suitable option because it typically contains oral bacteria, some of which are anaerobic and are usually harmless. This makes it difficult to determine whether the anaerobic bacteria in sputum are the source of infection. Although not ideal, a sputum gram stain can be useful; the stain may show a high number of neutrophils (white blood cells), suggesting the presence of infection. A foul smell in sputum can also indicate anaerobic bacteria may be present in sputum.

2. Invasive Technique: To diagnose anaerobic lung infections, a doctor needs to identify the exact type of bacteria causing them. A sample of the lower respiratory tract (lungs) free of oral bacteria is needed for this.

• Transtracheal Aspiration: The sample is obtained by inserting a needle through the trachea (windpipe). The sample obtained using this method is uncontaminated by pharyngeal, nasal, and oral secretions. Although effective, there are some potential risks, and a highly skilled technician is required.

• Bronchoscopy Brushing: The current recommended technique for taking samples from lower airways. A small flexible tube with a camera is inserted through the mouth or nose to visualize the airways and collect lung tissue or fluid samples using a brush or lavage.

• Thoracentesis: It is a procedure to remove fluid from the area surrounding the lungs. The pleural space is reached by passing a needle through the chest wall. Pleural space is a narrow space that exists between the inner chest wall and the pleura (double layer of membrane that surrounds the lungs) of the lungs.

• Blood Culture: A blood sample is taken to detect anaerobic bacteria that may have entered the bloodstream from the lungs.

• Surgical Lung Biopsy: In real cases, tissue samples from the lung may be removed surgically for examination and culture.

What Is the Treatment of Anaerobic Pleuropulmonary Infections?

• Penicillin is a common antibiotic used for the treatment of lung infections. However, it is becoming less effective due to the development of resistance by bacteria.

• Clindamycin is currently the recommended first-line antibiotic for lung infections suspected to involve anaerobic bacteria because of high rates of Penicillin resistance.

• Penicillin is still administered to critically ill patients. It should be combined with another antibiotic, such as Clindamycin or Metronidazole, to target the resistant strain.

• Fluoroquinolone, such as Moxifloxacin, is effective against some anaerobic bacteria but requires further study.

Depending on how complicated the infection is, antimicrobial therapy has varying duration. Complicated cases of aspiration pneumonia may only need seven to ten days of therapy. In contrast, more complex cases such as necrotizing pneumonia, lung abscess, or empyema may require four to eight weeks of treatment.

Conclusion:

Anaerobic bacteria present a significant challenge in managing lung infections. However, with increased awareness, enhanced diagnostic methods, and a wider range of antibiotics, doctors are prepared to tackle these hidden threats. The patient outcome has improved by knowing the risks, symptoms, and treatment options.