Date post: | 07-May-2015 |
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STREPTOCOCCUSSTREPTOCOCCUS
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Strepto-cocci
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Commensals or Parasites of man & animals or Saprophytes of decaying matter
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Genus Streptococcus
Gram-Positive Cocci in Pairs or Chains
v/s
Staph – gram positive cocci in clusters (grape like)
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Gram-PositiveStreptococcus
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Gram positive cocci in clusters
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Classification
On the basis of their growth characteristics on blood agar
Alpha hemolytic Beta hemolytic Gamma hemolytic
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Example –
Streptococcus viridans (Viridans = green)
Streptococcus pneumoniae
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Example – enterococcus group
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Beta hemolytic streptococciLancefield grouping Group A to Group V without I and J Divided according to differences in Cell wall
carbohydrate antigen Out of all these, those of Group A known as
streptococcus pyogenes produce majority of human infections
Group B are known as S agalactiae
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Group A beta hemolytic streptococci / strep pyogenes These are further subdivided according to sell
surface M, T and R antigens Griffith typing
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Streptococcus Pyogenes(Group A beta hemolytic)
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Description headings
Morphology Growth characteristics Biochemical reactions Resistance Pathogenicity and virulence Epidemiology Diseases caused Laboratory diagnosis Treatment
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Morphology
Cocci in long chains
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Description headings
Morphology Growth characteristics Biochemical reactions Resistance Pathogenicity and virulence Epidemiology Diseases caused Laboratory diagnosis Treatment
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Growth characteristics
Facultative anaerobe, grows best in presence of 10% CO2
Grows on enriched media only Beta hemolysis around colonies on blood
agar
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Description headings
Morphology Growth characteristics Biochemical reactions Resistance Pathogenicity and virulence Epidemiology Diseases caused Laboratory diagnosis Treatment
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Biochemical reactions
Ferment sugars – produce acid , no gas Catalase negative Catalase helps to differentiate staphylococci
from streptococci
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Catalase test
Add hydrogen peroxide to culture material
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Description headings
Morphology Growth characteristics Biochemical reactions Resistance Pathogenicity and virulence Epidemiology Diseases caused Laboratory diagnosis Treatment
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Resistance
Most are still susceptible to penicillin and erythromycin
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Description headings
Morphology Growth characteristics Biochemical reactions Resistance Pathogenicity and virulence Epidemiology Diseases caused Laboratory diagnosis Treatment
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Pathogenicity and virulence Antigenic structure
Antigens on surface of strep cross react with body proteins Capsular hyaluronic acid – human joints – autoimmune arthritis Carbohydrate antigen – cardiac valves – rheumatic heart
disease Toxins Enzymes
Streptolysin O – ASO titre for diagnosis Streptolysin S – for hemolysis around colonies Streptokinase – lysis of clots – given iv for treatment of MI DNA ase – Anti DNAase is useful for diagnosis of S.
pyogenes skin infection Hyaluronidase – breaks down tissues – helps in spread of
strep infection
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Description headings
Morphology Growth characteristics Biochemical reactions Resistance Pathogenicity and virulence Epidemiology Diseases caused Laboratory diagnosis Treatment
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Epidemiology
Source – human upper respiratory tract – throat, pharynx, nose
Transmission – direct contact, fomites
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Description headings
Morphology Growth characteristics Biochemical reactions Resistance Pathogenicity and virulence Epidemiology Diseases caused Laboratory diagnosis Treatment
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Diseases caused
Pus producing (suppurative) Respiratory infections Skin and soft tissue infections Genital infections
Non suppurative Acute rheumatic fever Rheumatic heart disease Acute glomerulonephritis (kidney)
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Respiratory infections
Tonsillitis Pharyngitis
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Skin and soft tissue infections
Skin Erysipelas – involves lymphatics – older pts Impetigo – young children Pyoderma
Soft tissue Cellulitis Necrotising fascitis
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Erysipelas
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Impetigo
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Pyoderma
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Cellulitis
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Necrotising fascitisflesh eating bacteria (anaerobes)
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Non suppurative complications
After 1-3 weeks of primary infection
Due to cross reactivity
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Acute rheumatic fever
Follows streptococcal sore throat
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Acute glomerulonephritis
Cross reaction between streptococci and kidney tissues
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Rheumatic heart disease
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Description headings
Morphology Growth characteristics Biochemical reactions Resistance Pathogenicity and virulence Epidemiology Diseases caused Laboratory diagnosis Treatment
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Suppurative infections
Examination of pus/throat swabs Microscopy, staining and culture Gram stain Blood agar
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Non suppurative infections
Demonstration of antibodies Like ASO and anti DNA ase B
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Description headings
Morphology Growth characteristics Biochemical reactions Resistance Pathogenicity and virulence Epidemiology Diseases caused Laboratory diagnosis Treatment
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Treatment
Penicillin Erythromycin Drugs have no effect if non suppurative
complications have developed
Prophylaxis – can prevent rheumatic fever, not glomerulonephritis
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OTHER STREPTOCOCCI
BETA HEMOLYTIC - GROUP B AND GROUP D
ALPHA HEMOLYTIC (VIRIDANS GROUP)– STREPTOCOCCUS
PNEUMONIAE
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Group B Streptococcus
Streptococcus agalactiae
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Group B Streptococcus S. agalactiae
1. Infect newborns
2. Infection acquired through maternal vagina during birth
3. Presents as meningitis, pneumonia or septicemia
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Diagnostic Laboratory Tests
CAMP factor positive Hippurase positive
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CAMP (Christie, atkins, munch-peterson) Factor Test
S. aureus
(Spingomyelinase C)Group B
Streptococcus
(CAMP Factor)
Group A Streptococcus
Enhanced Zone of
Hemolysis
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Hippurase NEG
Streptococcus agalactiae not added
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Hippurase POS
Grp B Streptococci
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Viridans group
Streptococcus pneumoniae
• Commonly referred to as pneumococcus
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Description headings
Morphology Growth characteristics Biochemical reactions Resistance Pathogenicity and virulence Epidemiology Diseases caused Laboratory diagnosis Treatment
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Lancet shaped (one end broad, other pointed)
Capsulated Diplococci
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S. pneumoniae: lancet-shaped diplococcus
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S. pneumoniae
• Diplococcus
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Capsular stain
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Description headings
Morphology Growth characteristics Biochemical reactions Resistance Pathogenicity and virulence Epidemiology Diseases caused Laboratory diagnosis Treatment
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Growth characteristics
Alpha hemolysis on blood agar On further incubation, the colonies become
flat with raised edges and central elevation resembling carrom coins
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Example –
Streptococcus viridans (Viridans = green)
Streptococcus pneumoniae
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Description headings
Morphology Growth characteristics Biochemical reactions Resistance Pathogenicity and virulence Epidemiology Diseases caused Laboratory diagnosis Treatment
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Biochemical reactions
Hiss serum water – fermentation of inulin Bile solubility
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Inulin fermentation
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Description headings
Morphology Growth characteristics Biochemical reactions Resistance Pathogenicity and virulence Epidemiology Diseases caused Laboratory diagnosis Treatment
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Resistance
Pneumococcus is sensitive to optochin – used for typing
Resistance to penicillin – third generation cephalosporin like ceftriaxone
May be resistant to third gen ceph also
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Description headings
Morphology Growth characteristics Biochemical reactions Resistance Pathogenicity and virulence Epidemiology Diseases caused Laboratory diagnosis Treatment
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Pathogenicity and virulence
Capsule Toxins – pneumolysin C reactive protein
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Capsule
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Pneumolysin
Membrane damaging toxin Cytotoxic activity
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C reactive protein
Abnormal immunoglobulin against C protein of S. pneumoniae appears in serum of patients
Also seen in acute phase of infections and inflammations
CRP titre is tested in acute infections
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Description headings
Morphology Growth characteristics Biochemical reactions Resistance Pathogenicity and virulence Epidemiology Diseases caused Laboratory diagnosis Treatment
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Epidemiology
Source – respiratory tract of humans Spread – droplets Carriers – pharynx Low immunity is responsible for fulminant
infections RSV infection, pulmonary congestion, stress,
malnutrition, alcoholism Splenectomy Sickle cell disease
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Description headings
Morphology Growth characteristics Biochemical reactions Resistance Pathogenicity and virulence Epidemiology Diseases caused Laboratory diagnosis Treatment
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Diseases caused
Middle ear – otitis media Para nasal sinuses – sinusitis Respiratory tract – pneumonia, bronchitis,
empyema Meningitis is secondary to otitis media,
penumonia, sinusitis and conjunctivitis
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Description headings
Morphology Growth characteristics Biochemical reactions Resistance Pathogenicity and virulence Epidemiology Diseases caused Laboratory diagnosis Treatment
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Laboratory diagnosis
Sample sputum – pneumonia septicemia - blood culture Otitis media - fluid from middle ear Meningitis - CSF
Method Gram stain, microscopy culture
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Latex agglutination for pneumococcal antigen in serum of patients
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Description headings
Morphology Growth characteristics Biochemical reactions Resistance Pathogenicity and virulence Epidemiology Diseases caused Laboratory diagnosis Treatment
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Treatment
Penicillin Amoxycillin ceftriaxone/ceftazidime Vancomycin
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Prophylaxis
Pneumococcal conjugate vaccine is available
Given to splenectomy patients, sickle cell anemia patients and susceptible individuals
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GROUP D STREPTOCOCCI
Enterococcus faecalis Enterococcus faecium
• GI tract of humans and animals
• Group D carbohydrate cell wall antigen
• Formerly Streptococcus
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Cause UTI, wound infection Endocarditis Intra abdominal abcesses
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