This document discusses the laboratory diagnosis of various Streptococcus species based on their characteristics and test results. It describes how S. pneumoniae can be identified from other alpha-hemolytic streptococci based on being catalase-negative, optochin-sensitive, and bile soluble. It also discusses how S. pyogenes causing a sore throat in a child can be identified as the cause based on being a beta-hemolytic streptococcus that is catalase-negative and bacitracin-sensitive. For the patient with pneumonia, S. pneumoniae is identified as the likely pathogen from alpha-hemolytic colonies that are catalase-negative and optochin-sensitive in sputum culture.

1. Lab. Diagnosis of Streptococcus

2. Classification
Based on O2
Aerobes Anaerobes
Peptostreptococci
Growth on BA
α hemolysis β hemolysis γ hemolysis
Incomplete hemolysis
(green color)
Complete hemolysis α / β / no hemolysis
Strep. viridans
Strep. pneumoniae
Enterococcus
fecalis
Lancefield grouping
specific C carbohydrate Ag on cell wall
Group A – V (except I & J,
20 groups)
Griffith typing of Group A on MTR proteins into > 100 serotypes

3. CASE - 1
• A 5-year-old male c/o- sore throat and fever treated
symptomatically with Paracetamol but still complaining
of sore throat, fever, headache & abdominal pain. He
was an only child and neither parent was ill.
• On physical examination,
Temp.- 38.4°C.
Red- anterior pharynx, tonsillar region, soft palate.
Anterior cervical lymph nodes -enlarged and tender.
No skin lesions or rashes.
did not have a cough, runny nose, or conjunctivitis.
 Based on his clinical presentation, how to proceed your
diagnosis and what organism was most likely causing
this patient’s infection?

4. Throat swab
•
G/S CULTURE on BA
Small,Pin point, circular, β hemolytic colonies
Gpc in chain catalase
With pus cells
Negative Positive
BA with Bacitracin
Sensitive Resistant
CAMP TEST
Gr. A streptococcus Gr. B streptococcus

5. Beta hemolytic Group A
Streptococcus
(Streptococcus pyogenes)
1

6. Lab diagnosis – Strep. pyogenes
• Specimens: throat swab, pus, blood
• Microscopy:Gram stain - GPC in chains
• Culture: BA - beta hemolytic colonies
• Identification tests -
• Catalase Negative
• Bacitracin sensitive
• Penicillin sensitive B
B

7. Beta hemolytic Group B Streptococcus
1

8. Lab diagnosis – Group B Streptococci
• Specimens: CSF, blood, vaginal
smears, urine
• Microscopy :Gram stain - GPC in
chains
• Culture: BA - beta hemolytic
colonies
• Identification tests
• Catalase negative
• Bacitracin resistance
• CAMP Test +
• Penicillin sensitive
P B

9. Clinical isolate-
•G/s- GPC in short chain
•BA- Pin point, β hemolytic colonies
•Catalase- negative
•Bacitracin- sensitive
•CAMP test- negative
•Isolate ????
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10. CASE - 2
• 64-year-old presented with progressive shortness of breath, a
persistent productive cough, purulent sputum, and fever to 39.0°C 2
days prior to admission. He had a 30-year history of smoking.
• On physical examination
 Temp.- 37.3°C
 RR- 18/minute
 PR- 103 beats/min
 BP- 154/107 mm Hg and
 Po2- 92 mm Hg.
 On Chest auscultation- coarse breath sounds with fine crackles at the
left lower base.
 On chest radiograph -left lower lobe consolidation
• On admission- WBC count 13,600/μl with 92% N, and Hb- 9.4 g/dl.
 Based on his clinical presentation, how to proceed your diagnosis
and what organism was most likely causing this patient’s infection?

11. SPUTUM
•
G/S Culture on BA
Small,Pin point, circular,draughtsman shaped α hemolytic colonies
Lanceolate gram+diplococci catalase
With pus cells
Negative Positive
BA with optochin
Sensitive Resistant
Streptococcus viridans
Bile solubility
CA- bleaching effect
Pneumococcus

12. Alpha hemolytic streptococci
Streptococcus pneumoniae
1

13. Lab diagnosis
• Specimen: CSF, blood, sputum, pus,
swabs
• Microscopy: Gram stain – GPC in pairs,
capsulated, lanceolate shaped
• Culture
• BA/ CA – alpha hemolytic colonies
• CA- bleaching effect
• Identification tests
• Catalase –ve
• Optochin sensitive
• Bile solubility

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15. •Capsulated
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16. Differences between Viridans Gp & Pneumococci
Point Pneumococci Viridans Gp
Morphology Capsulated, lanceolate,
diplococci
Oval or rounded in
chains
Quellung test + -
Colonies Dome shaped
Draughtsman
Dome shaped
Growth in liquid Uniform turbidity Granular turbidity with
powdery deposits
Bile solubility + -
Inulin fermentation + -
Optochin sensitivity + -
Intraperitoneal
inoculation in mice
Fatal Infection Non-pathogenic

17. Clinical isolate-
•G/s- Lanceolate gram positive diplococci
•BA- Pin point, α hemolytic colonies
•Catalase- negative
•Optochin- sensitive
•Bile soluble
•Isolate ????
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18. Medically Important Gram Positive, catalase negative Cocci
Family, Genus, species Characteristics Clinical manifestations
Streptococcaceae Cocci in chains and in pairs,
catalase-negative
Streptococcus pneumoniae Diplococci, α-hemolysis Pneumonia, otitis media,
sinusitis
S. viridans Cocci in chains, α-hemolysis Endocarditis, dental caries
S. pyogenes Cocci in chains, Lancefield group
A, β - hemolysis
Tonsillitis, scarlet fever,
skin infections
S. agalactiae Chain-forming cocci, group antigen
B, β-hemolysis
Meningitis/sepsis in
neonates