Strep

Question 1

Strep Pyogenes, group A, morphology

Answer 1

Gram-positive coccus in chains

Beta hemolytic colonies

Question 2

Strep Pyogenes, group A etiologic agent of?

Answer 2

1. Skin and Tissue infections
2. Necrotizing Fascitis
3. Acute exudative pharyngitis
4. Post streptococcal complications
   a) Rheumatic Fever
   b) Acute glomerulonphritis

Question 3

1. numerous invasive enzymes
2. capsule of hyaluronic acid
3. cell wall ‘M; protein is antiphagocytic
4. Erythrogenic toxin - scarlet fever rash
5. Strepolysin O and S- cytotoxic, basis of ASO titer and related tests

Answer 3

Strep Pyogenes, group A

Question 4

Strep Pyogenes, group A, laboratory diagnosis

Answer 4

1. culture and biochemical identification
2. Antigen detection/identification
   a) direct throat swab-low sensitivity
   b) culture formation-very accurate
3. antimicrobic susceptibility tests usually not needed

Question 5

Scarlet fever of strep pyogenes, group A

Answer 5

skin rash due
to erythrogenic toxin
** Antibody to toxin prevents rash in future infections

Question 6

strep pyogenes, group A, necrotizing fascitis

Answer 6

(streptococcal gangrene,
invasive cellulitis, “flesh- eating
bacteria”) and Streptococcal
Toxic Shock Syndrome
(a) Acute toxic and necrotic invasion of tissue – super-antigen effects
(b) Necrotizing fascitis – characterized by the rapid destruction of muscle and fat tissue
with high fever and prominent pain; highly invasive and life threatening
(c) Treatment – Aggressive antimicrobic therapy (penicillin) and surgicalintervention
(debridement of affected tissue to remove toxin)

Question 7

strep pyogenes, group A, acute exudative pharyngitis

Answer 7

(a) 2-4 days incubation
(b) Sudden onset of fever, sore throat, and exudative tonsillitis or pharyngitis with
enlarged and tender cervical lymph nodes
(c) Symptoms last a few days (3-5) without antibiotic treatment
(d) Predominantly occurs in children 5-15 years of age and during the colder months
(transmission easier due to the effect of crowding and to dry nasal passages)
(e) Major problem is the possibility of post-streptococcal complications

Question 8

Post streptococcal complications?

Answer 8

autoimmune reaction of Ag-Ab complexes on the
basal membranes of the affected organs [No live bacteria in heart or kidney tissue.] –
Specific antigenic types are responsible.

(a) Rheumatic fever – Ag-Ab complexes attack heart tissue – specific antigenic types;
especially follows throat infections

(b) Acute glomerulonephritis – Ag-Ab complexes attack kidney tissue – specific
antigenic types; usually follows throat or skin infections

Question 9

Group B streptococcus key points?

Answer 9

Causes pneumonitis and meningitis in neonates due to inoculation from vaginal flora;
infection can be quite severe in newborns and leave permanent damage or cause death.

Expectant mothers are screened around 35th week to determine if bacteria is present.

Question 10

Streptococcus Pneumoniae, Morphology

Answer 10

a. Gram-positive coccus in pairs

b. Large, mucoid, alpha-hemolytic colonies

Question 11

Strep Pneumoniae secondary info

Answer 11

Multiple antigenic types (>90); about 6 are frequently recovered and highly infectious

Normal flora of upper respiratory tract in 30 to 60% of population (esp. when children are in
the household). Infection usually results from transmission of normal flora into adjacent sites.

Question 12

Strep Pneumoniae, etiologic agent of?

Answer 12

1. lobar and bronchial pneumonia (#1)
2. sinusitis
3. otitis media
4. meningitis

Question 13

Strep Pneumoniae, virulence factors?

Answer 13

(1) Antiphagocytic capsule
(2) IgA protease
(3) Increase in penicillin resistance (about 30% are resistant to penicillin & 15% are resistant
to 2nd or 3rd antimicrobic)
(4) Some strains are invasive

Question 14

Strep Pneumoniae, laboratory diagnosis?

Answer 14

(1) Culture (alpha hemolytic) and biochemical identification

(2) Antigenic identification from cerebrospinal fluid

Question 15

Strep Pneumoniae, lobar and bronchial pneumonia?

Answer 15

(a) Causes 50-90% of pneumonias; esp. in children under 5 yr and elderly
(b) Invasive strains may lead to empyema, bacteremia, and/or meningitis
(c) Mortality: about 5-10%; esp. in children under 5 yr and elderly

Question 16

Other Streptococci of human significance?

Answer 16

1. other beta-hemolytic Strep in groups, C, F, G

2. Viridians Streptococci (group of alpha-hemolytic and non-hemolytic species)

Question 17

Enterococcus faecalis, morphology?

Answer 17

Gram-positive cocci in chains (formerly a member of group D Streptococcus)

Question 18

(1) Frequent cause of nosocomial infections - surgical wounds and urinary tract
(2) Occasional cause of bacteremia (~9%)

Answer 18

Enterococcus faecalis

Question 19

Enterococcus faecalis, drug resistance?

Answer 19

Multi-drug resistant strains exist with increased frequency, including vancomycin resistance
(Vancomycin Resistant Enterococcus = VRE)

Question 20

Streptococcus Pneumoniae etiologic agent of mnemonic?

Answer 20

MOPS:
Meningitis
Otitis Media
Pneumonia
Sinusitis

Question 21

Gram-positive coccus in pairs?

Answer 21

Strep Pneumoniae