Bacteria

Alpha Hemolytic Streptococci

Viridans Group Streptococci & Pneumococci.
• Department of Microbiology
• College of Medicine
• University of Baghdad
• Lec3, 2013-2014
• Dr.Sarmad M. Zeiny

Objectives: Upon completion of this lecture, the student will:

• Analyze the diseases & pathogenicity for viridans & pneumococci.
• Demonstrate the epidemiology/transmission for viridans & pneumococci.
• Outline the laboratory diagnosis for viridans & pneumococci.
• State the drug of choice and prophylaxis where regularly used.

Alpha hemolysis (green discoloration)

Viridans Streptococcus

• Viridans Streptococcus is eating heart valves slowly, while Staphylococcus aureus is eating fast .

• Question?

• Why patient with abnormal heart valve should take antibiotic prophylaxis before tooth extraction?

S.pneumoniae (Pneumococci, Diplococcus pneumoniae)

Distinguishing Features:
α-hemolytic, capsulated G+ve diplococci.
Lancet-shaped diplococci (cat’s eye).
Optochin sensitive.
Lysed by bile.


Typed to 84 serotypes according to the nature of capsular polysaccharide antigen.

Capsular polysaccharide

Gram +VE diplococcus

Reservoir: human upper respiratory tract.

Transmission:
By respiratory droplets:
- Not considered highly communicable.
- Often colonizes the nasopharynx without causing disease.


Predisposing Factors:
• Antecedent influenza or measles infection.
• Chronic obstructive pulmonary disease (COPD).
• Congestive heart failure (CHF).
• Alcoholism.
• Asplenia.

Virulent factors & Pathogenesis:

Polysaccharide capsule is the major virulence factor  anti-phagocytosis
lgA protease  Breakdown IgA
Teichoic acid.  Rigid cell wall
Pneumolysin O: hemolysin/cytolysin
- Damages respiratory epithelium
- Inhibits leukocyte respiratory burst and
- Inhibits classical complement fixation

• The "pneumococcal warrior." He is a mighty foe, with "capsule" armor, a lung emblem on his shield, and a lancet-shaped diplococcus lance. The lung emblem on his shield shows the severe lobar pneumonia caused by this organism.

Diseases:

TYPICAL PNEUMONIA:
- Most common cause (especially adult & elderly)
Shaking chills, high fever, lobar consolidation, blood-tinged, "rusty" sputum.
Pneumococcus is to Parents while group B streptococcus is to Babies.
ADULT MENINGITIS:
- Common cause.
- CSF reveals high WBCs (neutrophils), low glucose and high protein.
OTITIS MEDIA AND SINUSITIS IN CHILDREN:
• - most common cause


Prevention: by Vaccine
- Pediatric (PCV, pneumococcal capsular vaccine):
Seven of the most common serotypes
Conjugated to diphtheria toxoid
- Adult (PPV, pneumococcal polysaccharide vaccine):
23 of the most common capsular serotypes
Recommended for all adults >65 years of age and any at-risk individuals

CHARACTER

PNEUMOCOCCI
VIRIDANS STREPTOCOCCI
Morphology
Ovoid or lanceolate diplococci
Rounded cocci in short or long chains.
Capsule
Present
Absent
Optochin sensitivity
+ve
-ve
Bile solubility
+ve
-ve
Capsular swelling test (Quelling reaction)
+ve
-ve
Virulence in mice
+ve
-ve
Differences between Viridans & Pneumococci


Q: Answer with true or false
• Pneumococci is uncapsulated.
• Pneumococci is α-hemolytic.
• No vaccine for pneumococci.
• Pneumococci is bile soluble.
• Pneumococci can’t be differentiated from viridans streptococci.

Lab Dx

Optochin disc for S.pneumococci

India ink slide, see the Quelling reaction

Gram slide, see the diplococci

Question? Name this test

summary
• Alpha haemolytics streptococci causing greenish discoloration on chocolate agar.
• Viridans causes SBE in suspected individuals. AB prophylaxis needed.
• Pneumococci is capsulated and typed accordingly to 84 serotyped.
• Pneumococci is the leading cause of adult pneumonia.
• Pneumococci present in carrier state in 40-70% of healthy humans.
• Pneumococci & viridans can be differentiated by Optochin sensitivity, arrangement, bile solubility, Capsular swelling test (Quelling reaction) and serologically.
• Pneumococci can be prevented by a Vaccine  causing Ab against capsular Ag.

THANKS