Last updated: Aug 5, 2025Published on: Aug 5, 2025
Table of Contents
Introduction
Pneumonia is one of the leading causes of mortality in the world, making it a global health concern1. It is a serious infection that affects your lungs by causing inflammation and fluid or pus accumulation in the alveoli (air sacs) of your lungs2. Bacterial pneumonia, especially from Streptococcus pneumoniae or Haemophilus influenzae type b, is a common cause of pneumonia-related deaths. However, viral pneumonia, caused by viruses like respiratory syncytial virus (RSV) and influenza, also contributes significantly to pneumonia cases and fatalities1,3.
What Is Bacterial Pneumonia?
Bacterial pneumonia, as the name suggests, is caused by various bacteria that invade your lungs. Your body’s natural defence system tries to fight these bacteria as a part of the immune response, leading to inflammation of the air sacs of your lungs and the accumulation of fluid and pus in them4. Inflammation occurs as part of the immune response, but sometimes pathogenic bacterial factors also directly damage tissue, e.g., inflammation caused by the toxin pneumolysin from S. pneumoniae5. Bacterial pneumonia can be of different types, including3:
Community-acquired Pneumonia: Occurs in individuals who acquire the infection outside of hospital settings or within 48 hours of admission.
Hospital-acquired Pneumonia: This type of pneumonia occurs in individuals who develop the infection 48 hours after admission to any hospital.
Atypical Pneumonia: This type of pneumonia is generally caused by bacteria that are less commonly associated with pneumonia, e.g., Mycoplasma pneumoniae, Chlamydia pneumoniae, and Legionella spp. These organisms are not generally identified by the traditional staining methods (Gram stain), but the pneumonia often presents with symptoms that occur outside the lungs. Though atypical bacterial pneumonia is mostly bacterial in origin, it may not be categorised as typical bacterial pneumonia6.
Ventilator-associated Pneumonia: This type of pneumonia occurs 48 hours or more after a person has been placed on a ventilator to help them breathe.
Community-acquired Pneumonia: The main organisms that cause this infection include S. pneumoniae, H. influenzae, M. pneumoniae, Legionella spp., Moraxella catarrhalis, and Staphylococcus aureus (especially methicillin-resistant S. aureus), which is commonly associated with severe cases or following a viral infection like influenza.
Hospital-acquired Pneumonia: The main organisms that cause this infection include S. aureus, Pseudomonas aeruginosa, and Acinetobacter baumannii.
Atypical Pneumonia: The main organisms that cause this infection include M. pneumoniae, C. pneumoniae, or Legionella pneumophila.
Ventilator-associated Pneumonia: The main organisms that cause this infection include S. aureus, P. aeruginosa, enterobacter species (such as Klebsiella, E. coli) and gram-negative bacilli8.
In 50% of pneumonia cases, the etiological factor remains unknown. Identifying the causative organism is essential for appropriate treatment7.
How Does Bacterial Pneumonia Spread?
Bacterial pneumonia is contagious and can spread from person to person. This infection is transmitted through contact with infected surfaces. It can also spread when the droplets released when an infected person coughs or sneezes are inhaled by another person3,7.
It is always recommended to avoid close contact with infected individuals, wear a mask and practice proper hand hygiene to reduce your risk of infection9.
Who Is More Likely to Get Bacterial Pneumonia?
While bacterial pneumonia can affect anyone, certain groups of people, including the following, are more likely to develop bacterial pneumonia3,7,10:
Children (under 5 years of age) or older adults (over 65 years of age).
Chronic conditions (such as diabetes, chronic lung disease, and heart disease).
Weakened immune system.
Smoking and alcohol consumption.
Poor oral hygiene
Use of certain medications (e.g., proton pump inhibitors like omeprazole and pantoprazole).
Symptoms of Bacterial Pneumonia
The signs and symptoms of bacterial pneumonia include3,7:
Productive cough with mucus that can be clear, yellow/green, or contain blood. Dry cough is more common with viral and atypical pneumonia6,11.
Systemic symptoms of bacterial pneumonia may include3,7:
Headache
Sweaty and clammy skin or chills
Altered mental status or confusion
Hypotension
Cyanosis due to low oxygen levels
Increased heart rate (tachycardia). Decreased heart rate (bradycardia) is uncommon and may be associated with pneumonia caused by Chlamydia sp, Legionnaire’s disease, and typhoid12.
In children under 5 years of age, the signs and symptoms of bacterial pneumonia may include rapid breathing, chest pain, abdominal pain, and pale colour of the face3,7.
Diagnosis of Bacterial Pneumonia
After a careful assessment of your symptoms, your doctor will be able to diagnose your condition with the help of3,7:
Chest X-ray: If you present with symptoms of pneumonia, your chest X-ray serves as a first-line imaging tool for the diagnosis of bacterial pneumonia. Your chest X-ray may show pulmonary infiltrates and may suggest the type of pneumonia present (for example, lobar or interstitial pneumonia). However, it cannot accurately distinguish between bacterial and non-bacterial pneumonia (such as viral pneumonia).
Computed Tomography: Helpful in unclear cases or when other conditions may be present.
Blood Tests: Your doctor may recommend laboratory tests such as:
Complete blood count: Creatinine levels and complete white blood cell count (for the diagnosis and detection of severity of infection)
Liver function tests: Abnormalities on the liver function tests may be observed in cases of severe or complicated pneumonia or Legionella infections13.
Inflammatory biomarkers (e.g., erythrocyte sedimentation rate and C-reactive protein): Supportive markers for inflammation and severity. Elevated levels of C-reactive protein are suggestive of bacterial pneumonia. However, this result is not definitive, and these tests cannot distinguish between bacterial and viral pneumonia.
Arterial blood gases: Used in severe cases where hypoxia (low oxygen supply to tissues) and respiratory acidosis (acidic blood due to the presence of carbon dioxide) are present.
Sputum Culture: May be advised in severe cases or hospitalised cases to identify the bacteria causing your illness.
Gram Staining: To identify the bacteria and guide your treatment. For example, Gram-positive cocci, such as S. pneumoniae, and Gram-negative bacilli like H. influenzae.
Respiratory Viral Panel (including influenza): Done by collecting a sample from your respiratory tract (nasopharyngeal swab) to check for viral pathogens such as influenza, RSV or SARS-CoV-2. The results may indicate a secondary bacterial infection, which is common after a viral infection.
Based on these tests, your doctor will be able to diagnose your condition accurately and will suggest the appropriate treatment for your condition. A definitive diagnosis, especially in hospitalised cases or complicated cases will always require identification of the organism.
Bacterial vs. Viral Pneumonia
While bacterial and viral pneumonia are two common types of lung infections that share similar symptoms, the table below highlights the key differences between the two types of pneumonia3,7,11.
Bacterial Pneumonia
Viral Pneumonia
Aetiology
Bacterial (e.g., Streptococcus pneumoniae, Haemophilus influenzae, and Staphylococcus aureus)
Viral (for example, Respiratory syncytial virus or RSV, influenza virus, adenovirus and coronaviruses like SARS-CoV-2)
Onset
Sudden onset and more severe symptoms
Gradual onset and symptoms may not be severe initially
Nasal or throat swab (PCR), Chest X-ray, and patient’s history
Treatment
Antibiotics
Supportive care (rest, fluids, fever control); antivirals in some cases (e.g., influenza)
Complications
Abscess, empyema, and sepsis
Respiratory failure, liver failure, heart failure, and secondary bacterial infection
If you are suffering from any lung infection and are unsure whether it is a bacterial or viral infection, it is best to consult your doctor and get appropriate medical treatment.
Bacterial Pneumonia Treatment
The main treatment of bacterial pneumonia involves the use of antibiotics. If you are healthy and do not have any other chronic medical conditions, the treatment may include antibiotics like3,7:
If you have any chronic medical conditions such as diabetes or heart disease, the treatment may include combination treatments like3,7:
Amoxicillin/clavulanate or cephalosporins (such as cefpodoxime or cefuroxime) along with a macrolide (such as azithromycin or clarithromycin) or doxycycline.
Alternatively, your doctor may recommend a single stronger antibiotic like levofloxacin or moxifloxacin.
If you are admitted to the hospital but your pneumonia is not too severe, your doctors may recommend3,7:
A beta-lactam antibiotic (such as ceftriaxone) along with a macrolide (such as azithromycin or doxycycline).
Alternatively, a single respiratory fluoroquinolone (such as levofloxacin) may be used. However, it is important to note that overuse of these respiratory fluoroquinolones may lead to resistance to the antibiotic and an increased risk of Clostridium difficile infection14.
If you are admitted to the hospital and your pneumonia is severe, your treatment will be more aggressive and usually includes3,7:
A beta-lactam antibiotic plus a macrolide
Alternatively, your doctor may recommend a beta-lactam antibiotic along with a respiratory fluoroquinolone.
Prevention of Bacterial Pneumonia
Certain tips that you can follow to reduce your risk of pneumonia include3,7,9:
Ensure good hand hygiene by washing your hands regularly with warm water and soap.
Avoid smoking and alcohol consumption.
Maintain good oral hygiene, as poor oral hygiene is a risk factor for bacterial pneumonia.
Ensure prompt medical care if you have chronic conditions such as asthma.
Consult your doctor regarding the following vaccinations for infants and children to prevent pneumonia:
H. influenzae type b vaccination (Hib Vaccination): Recommended for infants and children under 5 years of age. The vaccination schedule can be a 3-dose series with doses taken at 2, 4, and 6 months plus a booster dose at 12-15 months or a 2-dose series with doses taken at 2 and 4 months plus a booster dose)15,16
Pertussis vaccination (DTaP / Tdap Vaccination): The DTaP vaccine is administered during childhood, while the Tdap booster is advised for adolescents and adults, especially for pregnant women. However, this vaccination does not directly prevent bacterial pneumonia17.
Pneumococcal vaccination (PCV 15/PCV20 and PPSV23): Helps protect against S. pneumoniae. This vaccination is recommended for all children under 5 years of age and for children and adults with chronic conditions like diabetes and chronic lung disease18.
By following these steps, you can reduce your risk of developing bacterial pneumonia and improve your overall health3,7.
Complications of Untreated Bacterial Pneumonia
If left untreated, bacterial pneumonia can lead to complications like7:
Fluid buildup around the lungs (pleural effusion)
Pus collection in the lung area (empyema)
Infection in the lung (lung abscess)
Breathing difficulty due to lung damage
Residual lung scarring after severe pneumonia or acute respiratory distress syndrome (ARDS)19
Widespread infection in the body (sepsis)
Bacteria in the bloodstream (bacteraemia)
Low oxygen levels in the blood (hypoxemia)
Early diagnosis and proper treatment of bacterial pneumonia can help prevent serious and potentially life-threatening complications7.
When to See a Doctor
You should consult a doctor for bacterial pneumonia if you experience symptoms like a persistent cough, chest pain, difficulty breathing, or a high fever3,7.
You should seek immediate medical attention if you are at an increased risk of developing bacterial pneumonia (if you are an adult over 65 years of age, a child under 5 years of age, or if you are facing any other chronic medical conditions)3,7.
Conclusion
Bacterial pneumonia is a serious infection that continues to pose a major global health challenge. Understanding its causes, risk factors, symptoms, and the importance of timely diagnosis and appropriate antibiotic treatment is key to improving outcomes. Preventive measures such as good hygiene, vaccination, and lifestyle modifications play a crucial role in reducing the risk of bacterial pneumonia. Most importantly, early medical attention, especially for high-risk individuals, can significantly lower the chances of complications and ensure better recovery.
Frequently Asked Questions (FAQs)
Can bacterial pneumonia recur after treatment?
Yes, bacterial pneumonia can recur after treatment. The chances of recurrence are increased in individuals with underlying health conditions, weakened immunity, or poor lung function. Recurrence may also happen if the initial infection wasn’t completely treated3,7.
When will my symptoms start to improve?
Most patients show improvement in 48 to 72 hours. If there is no improvement, an alternative cause should be suspected3.
Can bacterial pneumonia develop as a complication of viral pneumonia?
Yes, bacterial pneumonia can often develop as a secondary infection following viral illnesses like COVID-19 or influenza, often worsening the clinical outcome11.
What benefits does walking have for individuals with bacterial pneumonia?
Mild physical activity like walking can aid recovery; however, strenuous exercise should be avoided until your doctor confirms full recovery and lung function is stable. Consult your doctor to understand if exercises are suitable for your condition20.
References
Troeger C, Blacker B, Khalil IA, Rao PC, Cao J, Zimsen SRM, et al. Estimates of the global, regional, and national morbidity, mortality, and aetiologies of lower respiratory infections in 195 countries, 1990–2016: a systematic analysis for the Global Burden of Disease Study 2016. The Lancet Infectious Diseases [Internet]. 2018 Nov;18(11):1191–210. Available from: https://pmc.ncbi.nlm.nih.gov/articles/PMC6202443/
Miyashita N. Atypical pneumonia: Pathophysiology, diagnosis, and treatment. Respiratory Investigation [Internet]. 2021 Nov;60(1). Available from: https://pubmed.ncbi.nlm.nih.gov/34750083/
Pahal P, Rajasurya V, Sharma S. Typical Bacterial Pneumonia [Internet]. National Library of Medicine. StatPearls Publishing; 2023. Available from: https://www.ncbi.nlm.nih.gov/books/NBK534295/
Kohbodi GA, Rajasurya V, Noor A. Ventilator-associated Pneumonia [Internet]. PubMed. Treasure Island (FL): StatPearls Publishing; 2023. Available from: https://www.ncbi.nlm.nih.gov/books/NBK507711/
Ostergaard L, Huniche B, Andersen PL. Relative bradycardia in infectious diseases. The Journal of Infection [Internet]. 1996 Nov 1;33(3):185–91. Available from: https://pubmed.ncbi.nlm.nih.gov/8945708/
Patterson CM, Loebinger MR. Community acquired pneumonia: assessment and treatment. Clinical Medicine [Internet]. 2012 Jun;12(3):283–6. Available from: https://pmc.ncbi.nlm.nih.gov/articles/PMC4953496/
Shea KM, Hobbs ALV, Jaso TC, Bissett JD, Cruz CM, Douglass ET, et al. Effect of a Health Care System Respiratory Fluoroquinolone Restriction Program To Alter Utilization and Impact Rates of Clostridium difficile Infection. Antimicrobial Agents and Chemotherapy [Internet]. 2017 Jun;61(6). Available from: https://journals.asm.org/doi/10.1128/aac.00125-17
Gilsdorf JR. Hib Vaccines: Their Impact on Haemophilus influenzae Type b Disease. The Journal of Infectious Diseases [Internet]. 2021 Sep 30;224(Supplement_4):S321–30. Available from: https://pmc.ncbi.nlm.nih.gov/articles/PMC8482018/
Matthay MA, Zemans RL, Zimmerman GA, Arabi YM, Beitler JR, Mercat A, et al. Acute Respiratory Distress Syndrome. Nature Reviews Disease Primers [Internet]. 2019 Mar 14;5(1). Available from: https://pmc.ncbi.nlm.nih.gov/articles/PMC6709677/
Ikeda T, Inoue S, Konta T, Murakami M, Fujimoto S, Iseki K, et al. Can Daily Walking Alone Reduce Pneumonia-Related Mortality among Older People? Scientific Reports [Internet]. 2020 May 22;10. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7244731/
Disclaimer: The information provided here is for educational/awareness purposes only and is not intended to be a substitute for medical treatment by a healthcare professional and should not be relied upon to diagnose or treat any medical condition. The reader should consult a registered medical practitioner to determine the appropriateness of the information and before consuming any medication. PharmEasy does not provide any guarantee or warranty (express or implied) regarding the accuracy, adequacy, completeness, legality, reliability or usefulness of the information; and disclaims any liability arising thereof.
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