Gram positive cocci Arrangement : chains or pairs Part of normal flora Causes pathogenic infections also Non spore forming Non motile Catalase negative

2. Introduction
 Gram positive cocci
 Arrangement : chains or pairs
 Part of normal flora
 Causes pathogenic infections also
 Non spore forming
 Non motile
 Catalase negative

5. Gram positive cocci under microscope

6. Human Streptococcal Pathogens
S. Pyogenes
S. agalactiae
S. Viridans
S. Pneumoniae
S. Faecalis

7. Streptococci A groups(GAS) S. pyogenes
Most serious streptococcal pathogen. It a parasite and
inhabits throat, nasopharynx, can cause skin infection.
Morphology
 Gram-positive
 Spherical/ovoid cocci arranged in long chains.
 Nonmotile.
 Can form capsules.

9. Cultural character
 Aerobe and Facultative anaerobes.
 Best growth achieved at pH 7.4-7.6 and
temperature 37⁰C.
 Required enriched media.
 It grows on blood agar producing small colonies β-
haemolysis Antigens, semi transparent
β hemolysis

10. Biochemical reactions and properties
No gas
Catalase negative
PYR test (Pyrolidonyl beta naphthylamide) positiv e
 Not bile soluble
virulence factors of S. Pyogenes
 Protein antigens (M protein) and other ( T and B)
proteins
 Capsule(Hyaluronic acid) : inhibits phagocytosis

11. Toxins and enzymes
 Pyrogenic exotoxin :scarlet fever ,typical red
rash
Streptolysin (O ,S) Antigenic, stimulates the
production of anti-streptolysin O (ASO) Abs that
can be measured in patients serum. b.
Streptolysin S - Not antigenic Pyrogenic
exotoxin
 Streptokinase
 Streptodornase(DNAses)
 Hyaluronidase

12. Pathogenicity
Suppurative diseases:
Respiratory infection e.g. throat infection
Skin and soft tissue infections e.g. impetigo – skin
lesions
Genital infections
Non suppurative diseases :
Acute rheumatic fever
Acute glomerulonephritis

13. Post streptococcal diseases
Rheumatic fever
 autoimmune disease involving heart valves, joints, nervous
system. of S. pyogenes .Complication of pharyngitis due to
specific M protein types
Characterized by aschoff nodules (sub cutaneous nodule)
 Causes inflammatory myocardial lesion of connective tissue
degeneration of heart valves
 Results in chronic and progressive damage to heart valves,
arthritis
Complement Level unchanged

14. Acute glomerulonephritis
-inflammatory disease of renal glomeruli and structures involved in
blood filter of kidney. Glomerulonephritis
 symptoms : edema – decreased urination, hematuria,
hypertension, proteinuria
 provoke inflammatory response, interferes with normal kidney
function
 young children: self-limiting –adolescents /adults: rare
permanent kidney damage, chronic glomerulonephritis due to
deposition of Ag/Ab complexes.
 associated with M types producing URI & skin infections
 Complement level -lowered

16. Laboratory diagnosis
 S. pyogenes is frequently isolated from samples such
as skin, throat, sputum, urine, and blood.
 Different methods for laboratory diagnosis of S.
pyogenes are:
• Gram staining
• Culture :the organism is cultured on blood agar with
an added bacitracin antibiotic disk to show beta-
hemolytic colonies and sensitivity (zone of inhibition
around the disk) for the antibiotic.

17. • Catalase test: negative result is no bubbles
• ASO titre

18. Group B beta hemolytic Streptococci
(GBS)Streptococcus agalactiae
Neonatal infection . Most common cause of neonatal
meningitis
Source – from the maternal vagina during birth
 Diagnostic markers – Hippurate hydrolysis,
CAMP test Christie, Atkins and Munch-Peterson
when S.agalactiae is inoculated perpendicular to a
streak of S.aureus grown on blood agar an accentuated
zone of hemolysis occurs

20. Differentiation of β-hemolytic
streptococci
Lanciefield Classification
Bacitracin susceptibility Test
Specific for S. pyogenes (Group A)
CAMP test
Specific for S. agalactiae (Group B)

21. Streptococcus pneumoniae
Morphology
gram-positive
lancet-shaped diplococci
In sputum or pus, single cocci or chains are also
seen.
Capsulated
the growth of pneumococci is inhibited around a disk
of Optochin

22. Cultural character
• Culture requires blood or chocolate agar.
• Growth improved by 5-10% CO2.
• Facultative anaerobes.
• Best growth achieved temperature 25 - 40⁰C.
• Colonies are surrounded by greenish hemolysis under
aerobic conditions.

23. Pathogenesis
• 5-50% of all people carry it as normal flora in the
nasopharynx.
 Young children, elderly, immune compromised,
those with other lung diseases or viral infections, are
at risk.
 Pneumococci multiply and induce an inflammatory
 The virulence of the organism is a function of its
capsule, which prevents or delays ingestion by
phagocyte response..
Pneumococci diseases
Pneumonia : infection of lung.
Otitis media : infection of middle ear.

24. Biochemical properties
No significant toxin is produced in
pneumococci.
Presence of some of the extra cellular products
• Haemolysin
• Neuraminidase
• Hyaluronidase
Lack catalase and peroxidases.
Ferment glucose, lactose and sucrose with
production of acid.

25. Laboratory diagnosis
 S. Pneumococci is frequently isolated from samples
such as sputum, blood, CSF.
 Different methods for laboratory diagnosis of S.
Pneumococci are:
• Gram staining
• Quellung test
• Culture
• Catalase test

26. Viridans group
• Streptococci normally resident in oral and upper
respiratory tract
• α hemolytic on blood agar
Causes dental caries
• non-groupable.
• includes S. mutans
– Occassional endocarditis after tooth extraction

27. Enterococci
e.g S. Faecalis
• It is also known as enterococci.
• It is a Gram-positive
• Oval cocci in pairs or short chains.
• It can grow in the range of 10 to 45°C and survive at
temperatures of 60°C for 30 min.
• It is non-motile, facultative anaerobic microbe.
• It ferments glucose and does not produce a catalase.
• It is associated with urinary tract infections, biliary tract
infections, septicemia, endocarditis

29. N
Characteristics Staphylococcus Streptococcus
1 Arrangement Grape-like clusters. A chain of round cells.
2 Pathogenesis
Most of the
staphylococcal
species are non-
pathogens.
Streptococcus cause many
diseases.
3
&
Catalase Test
Species
differentiation
Positive (Catalase is an
enzyme to converts
hydrogen peroxide to
water and
oxygen gas).
Coagulase test
Negative
Type of hemolysis, Bile solubility test,
CAMP Test and Optochin
4
Enriched Media
Staph does not need
enriched media (not
fastidious).
Strep needs enriched media
(fastidious).
5 Common Diseases
Food poisoning, skin
Surgical Site
Infection, Wound
infection diseases,
Strep throat, Scarlet fever,
Cellulitis and necrotizing fasciitis
,blood infections, pneumonia,
meningitis in newborns,Impetigo
6 Hemolysis
No hemolysis or beta
hemolysis.
Either alpha, or beta or gamma
hemolysis.