Streptococcus pneumoniae bacteria

Streptococcus pneumoniae

Streptococcus pneumoniae picture pneumococcus

Streptococcus pneumoniae in clinical material occurs in two distinctive forms. Encapsulated, virulent strains isolated e.g., from sputum in patients with acute pneumonia, often forming highly mucoid, glistening colonies (production of capsular polysaccharide) surrounded by a zone of alpha-hemolysis. After prolonged cultivation (48 hours in an aerobic atmosphere enriched with 5-10% carbon dioxide) they are often able to form colonies about 5 mm in diameter.
In throat swabs Streptococcus pneumoniae can occur in its avirulent form (oropharyngeal carriage of pneumococci is common and they are considered to be part of normal flora). The colonies are only 0.5-2 mm in diameter, surrounded by zone of alpha-hemolysis and due to autolysis, often develop a dimpled rather a craterlike appearance. These colonies are someties morphologically indistinguishable from those of viridans streptococci but unlike viridas streptococci are sensitive to optochin and soluble in sodium desoxycholate (bile salts).

Streptococcus pneumoniae is a significant human pathogenic bacterium. S.pneumoniae was recognized as a major cause of pneumonia in the late 19th century and is the subject of many humoral immunity studies. Despite the name, the organism causes many types of pneumococcal infection other than pneumonia, including acute sinusitis, otitis media, meningitis, bacteremia, sepsis, osteomyelitis, septic arthritis, endocarditis, peritonitis, pericarditis, cellulitis, and brain abscess. S.pneumoniae is the most common cause of bacterial meningitis in adults and children, and is one of the top two isolates found in ear infection, otitis media. Pneumococcal pneumonia is more common in the very young and the very old. S.pneumoniae can be differentiated from viridans streptococci, some of which are also alpha hemolytic, using an optochin test, as S.pneumoniae is optochin sensitive. S.pneumoniae can also be distinguished based on its sensitivity to lysis by bile. The encapsulated, gram-positive coccoid bacteria have a distinctive morphology on gram stain, the so-called, "lancet shape". It has a polysaccharide capsule that acts as a virulence factor for the organism; more than 90 different serotypes are known, and these types differ in virulence.

Abbreviated from Wikipedia.

Streptococcus pneumoniae basic characteristics


Identification of Streptococcus pneumoniae

  • The optochin test (sensitive to optochin)
  • The bile solubility test (positive)
  • Capsular swelling reaction

Antibiotic treatment of Streptococcus pneumoniae infections

Should be always guided by in vitro susceptibility tests!!
Selection of appropriate antibiotics depends on diagnosis!!

  • penicillin
  • ampicillin
  • amoxicillin

  • cephalosporins I, II

  • macrolides

  • cephalosporins III (e.g., cefotaxime, ceftriaxone)


Streptococcus pneumoniae colonies on blood agar

Streptococcus pneumoniae (pneumococcus) growing on blood agar plate virulent strain of Streptococcus pneumoniae (pneumococcus), mucoid Streptococcus pneumoniae, alpha-hemolysis on blood agar, avirulent strain virulent strains of Streptococcus pneumoniae (pneumococcus), pneumococcus mucoid form, M phase colonies virulent and avirulent forms of Streptococcus pneumoniae, mucoid and rough form of pneumococci Streptococcus pneumoniae colonies compared with colonies of viridans streptococci pneumococcus on blood agar, appearance of colonies Streptococcus pneumoniae colony morphology, anaerobic cultivation and colony appearance pneumococci cultivated anaerobically on blood agar Streptococcus pneumoniae colonies. Colonies characteristic of pneumococci, R form of pneumococcus colonies of pneumococci, cololony morphology of S.pneumoniae autolysis of Streptococcus pneumoniae colonies on agar small colonies of Streptococcus pneumoniae with depresses centers alpha-hemolysis of Streptococcus pneumoniae on blood agar Streptococcus pneumoniae R form (R phase) colonies in detail mucoid colonies of Streptococcus pneumoniae. M form (mucoid) Streptococcus pneumoniae mucoid form mucoid form of pneumococcus. Dome shaped colonies of virulent pneumococci smooth form of peumococci, S form, S phase

Streptococcus pneumoniae alpha-hemolysis

mucoid pneumococci, mucoid form of Streptococcus pneumoniae on blood agar virulent mucoid colonies of Streptococcus pneumoniae pneumococcus colonies surrounded by a zone of alpha-hemolysis streptococcus pneumoniae type of hemolysis

Streptococcus pneumoniae; the optochin test

the optochin test with Streptococcus pneumoniae the optochin test with pneumococcus

Streptococcus pneumoniae; the bile solubility test

the bile solubility test with Streptococcus pneumoniae the bile solubility test, positive test result

Streptococcus pneumoniae susceptibility testing

the disk diffusion susceptibility tests with pneumococci testing of antibiotic susceptibility of pneumococci with Kirby-Bauer test

Streptococcus pneumoniae Gram stain

streptococcus pneumoniae appearance in sputum s.pneumoniae in sputum, Gram stain encapsulated pneumococci in sputum, Gram, pneumococcus capsule

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