Various pathogens, including many different bacteria, can cause CAP. Streptococcus pneumoniae is the most frequently isolated bacterial pathogen, detected in up to 15% of cases of patients who require hospitalization.1,2 Bacterial pathogens that cause CAP can be classified as either Gram-positive, Gram-negative or atypical.
Streptococcus pneumoniae is the most commonly identified cause of CAP, still implicated in 5–15% of cases requiring hospitalization in the US, despite declining in frequency.1,2
Drug-resistant Streptococcus pneumoniae has been classified by CDC as a serious threat based on the current rates of resistance to commonly used antibiotics.3
This illustration depicts a three-dimensional (3D), computer-generated image, of a group of Gram-positive, Streptococcus pneumoniae bacteria. The artistic recreation was based upon scanning electron microscopic (SEM) imagery. Image courtesy of the Antibiotic Resistance Coordination and Strategy Unit - Medical Illustrator, via the Public Health Image Library of the Centers for Disease Control and Prevention.
Staphylococcus aureus is an important cause of CAP. Methicillin-resistant Staphylococcus aureus (MRSA) can occur in the setting of recent or concurrent influenza infection and may cause severe disease in previously healthy patients.4
This illustration depicts a three-dimensional (3D) computer-generated image of a group of methicillin-resistant Staphylococcus aureus (MRSA) bacteria, which were arranged in a cluster. The artistic recreation was based upon scanning electron microscopic (SEM) imagery. Image courtesy of the Antibiotic Resistance Coordination and Strategy Unit - Medical Illustrator, via the Public Health Image Library of the Centers for Disease Control and Prevention.
Haemophilus influenzae and Klebsiella pneumoniae often cause CAP in patients with underlying structural lung disease such as chronic obstructive pulmonary disease (COPD) or bronchiectasis.1 Patients with alcohol use disorders are also at risk of infection with Klebsiella pneumoniae.5
Approximately one third of H. influenza bacteria produce β-lactamase (conferring resistance to amoxicillin, penicillin, aminopenicillin, and first generation cephalosporins).1
This digitally colorized scanning electron microscopic (SEM) image, depicts a blue-colored neutrophil interacting with two pink-colored, rod-shaped, multidrug-resistant (MDR), Klebsiella pneumoniae bacteria, which can also cause CAP. Image courtesy of the National Institute of Allergy and Infectious Diseases (NIAID), via the Public Health Image Library of the Centers for Disease Control and Prevention.
The atypical bacteria are intracellular pathogens that are difficult to detect with routine cultures and do not respond to treatment with β-lactam antibiotics.1,6 Mycoplasma pneumoniae and Chlamydophila pneumoniae are associated with milder disease that is often self-limiting in younger adults and children.1,7
CAP caused by Legionella spp. may be severe and associated with outbreaks from contaminated water sources.1
This illustration depicts a three-dimensional (3D), computer generated image, of a group of Mycoplasma pneumoniae bacteria. The artistic recreation was based upon scanning electron microscopic (SEM) imagery. Image courtesy of Sarah Bailey Cutchin, via the Public Health Image Library of the Centers for Disease Control and Prevention.
