The key difference between Streptococcus pneumoniae and Diplococcus pneumoniae is that Streptococcus pneumoniae exists as chains of paired cocci cells while Diplococcus pneumoniae exists as pairs of cocci.
Pneumonia is an acute respiratory disease that affects the lungs. A healthy lung is made up of small sacs called alveoli, where the exchange of gases takes place. During pneumonia, these alveoli get filled with pus and fluid, blocking the gas exchange pathway and causing severe breathing difficulties and eventually death. The causative bacteria for pneumonia are Streptococcus pneumoniae and Diplococcus pneumoniae. Both bacteria cause pneumonia, but with differences in the context of severity.
CONTENTS
1. Overview and Key Difference
2. What is Streptococcus Pneumoniae
3. What is Diplococcus Pneumoniae
4. Similarities – Streptococcus Pneumoniae and Diplococcus Pneumoniae
5. Streptococcus Pneumoniae vs Diplococcus Pneumoniae in Tabular Form
6. Summary – Streptococcus Pneumoniae vs Diplococcus Pneumoniae
What is Streptococcus Pneumoniae?
Streptococcus pneumoniae is a round-shaped chain bacteria. It is a facultative anaerobic, gram-positive bacterium that causes pneumococcal infections and diseases. They are encapsulated and coccoid bacteria that contain a distinctive morphology on gram stains. This bacterium contains a polysaccharide capsule that acts as a virulence factor for the organism. The genome of S. pneumoniae is a closed, circular DNA structure and contains about 2.0 to 2.1 million base pairs depending on the strain.
Figure 01: Streptococcus pneumoniae
S. pneumoniae is present asymptomatically in the respiratory tract, nasal cavity, and sinuses in healthy humans. In susceptible humans with the weak immune system, the bacterium becomes pathogenic, spreads, and causes diseases. Such diseases are common among the elderly and young children. The bacterium spreads easily by direct contact from person to person through respiratory droplets. S. pneumoniae is considered the main cause of community-acquired pneumonia and meningitis in both elderly and children. This bacterium causes pneumococcal infections such as pneumonia, bronchitis, rhinitis, conjunctivitis, acute sinusitis, meningitis, sepsis, septic arthritis, endocarditis, pericarditis, osteomyelitis, cellulitis, and brain abscess. Differentiation of S. pneumoniae is carried out by optochin tests using viridans streptococci, which are alpha-haemolytic. This bacterium is also distinguished based on the sensitivity to lysis using the bile solubility test.
What is Diplococcus Pneumoniae?
Diplococcus pneumoniae is a gram-positive bacterium that causes pneumonia. The term diplococcus refers to a round bacterium that typically occurs in the form of two joined cells. D. pneumoniae is a bacterium that requires catalase to grow on agar plates. Such bacteria are usually identified since they are catalase-negative, sensitive to optochin, go through lysis by bile salts and use alpha-hemolysis on blood agar.
Figure 02: Diplococcus pneumoniae
D. pneumoniae commonly colonizes the human respiratory tract and spreads through airborne droplets. Their capsule consists of complex polysaccharides that determine different serologic types. They contribute to virulence and pathogenicity. Virulency varies with serologic types due to genetic diversity. Patients who are susceptible to diseases and infections of D. pneumoniae are those with chronic illnesses such as diabetes, cardiorespiratory disease, and liver disease, those with immunodeficiency or immunosuppression, sickle cells diseases, functional or anatomic asplenia, and those addicted to alcohol and smoking.
What are the Similarities Between Streptococcus pneumoniae and Diplococcus pneumoniae?
- Streptococcus pneumoniae and Diplococcus pneumoniae are gram-positive bacteria.
- Moreover, they both take a round shape morphology.
- They cause pneumococcal infections and diseases.
- They are differentiated by the optochin test and bile solubility test.
- Both commonly reside in the respiratory tract.
What is the Difference Between Streptococcus pneumoniae and Diplococcus pneumoniae?
Streptococcus pneumoniae consists of chains of paired cocci cells, while Diplococcus pneumoniae consists of pairs of cocci. Thus, this is the key difference between Streptococcus pneumoniae and Diplococcus pneumoniae. Moreover, Diplococcus pneumoniae consists of an intracytoplasmic membrane system while Streptococcus pneumonia does not. While Streptococcus pneumoniae causes high severity infections, diplococcus pneumoniae causes comparatively low severity infections.
The below infographic presents the differences between Streptococcus pneumoniae and Diplococcus pneumoniae in tabular form for side-by-side comparison.
Summary – Streptococcus pneumoniae vs Diplococcus pneumoniae
Pneumonia is an acute respiratory disease that affects the lungs. The causative bacteria for pneumonia are Streptococcus pneumoniae and Diplococcus pneumoniae. Streptococcus pneumoniae exists as chains of paired cocci cells, while Diplococcus pneumoniae exists as pairs of cocci. So, this is the key difference between Streptococcus pneumoniae and Diplococcus pneumoniae. Both organisms are Gram-positive, and they take a general morphology of round shape. They commonly reside in the respiratory tract.
Reference:
1. Bush, Larry M., and Maria T. Vazquez-Pertejo. “Pneumococcal Infections – Infectious Diseases.” MSD Manual Professional Edition, MSD Manuals.
2. “Streptococcus Pneumoniae a (Diplococcus Pneumoniae).” SpringerReference.
Image Courtesy:
1. “DiplococcusCSF” By J3D3 – Own work (CC BY-SA 4.0) via Commons Wikimedia
2. “Streptococcus pneumoniae – A causative bacteria of meningitis” By Scientific Animations. (CC BY-SA 4.0) via Commons Wikimedia