introduction

Question 1

clinical manifestation of pharyngitis

Answer 1

1) can be viral or bacterial or chemical
2) bacterial
- group a streptococci

Question 2

pneumonia

Answer 2

1) m. pneumonia
2) s. pneumonia
3) influenza

Question 3

streptococci

Answer 3

1) A heterogeneous group of bacteria, Gram (+), facultative
anaerobes
2) Cocci arranged in pairs or chains
3) Catalase-negative (unlike Staphylococcus spp.)
4) Bacteria colonize and infect humans
5) Example of diseases caused by Streptocci:
Streptococcal pharyngitis (“strep throat”), pneumonia, cellulitis,
neonatal meningitis, brain abscess, endocarditis, toxic shock
syndrome and necrotizing fasciitis (flesh-eating disease)

Question 4

classification of streptococci and enterococci

Answer 4

Hemolytic pattern: When streptococci (and enterococci) are
grown on blood agar media in the clinical laboratory, the
colonies may be surrounded by an area of:
1) partial hemolysis that appears greenish (α-hemolysis),
2) a clear zone of complete hemolysis (β-hemolysis), or
3) the absence of a zone (γ-hemolysis or nonhemolysis).
Streptococci & Enterococci

Question 5

Lancefield classification

Answer 5

serological reactivity to extract cell wall antigens
from various streptococci/enterococci to divide them into groups
lettered A through V.
Note:
Many streptococcal species cannot be assigned to any group
because there are no antisera that react to their cell wall antigens.

Question 6

group A streptococcus: s. pyogenes clinical manifestation

Answer 6

1) strepthroat and scarlet fever
- Both conditions are self-limited diseases.
However, physicians always treat these conditions pharmacologically
- has to be treated with antibiotics

Question 7

s. pyogenes characteristics

Answer 7

β-hemolytic
1) Transient colonization in upper respiratory tract and
skin
2) Person-to-person spread by respiratory droplets
(pharyngitis) or through breaks in skin after direct contact
with infected person, or fomite.
3) Most common cause of bacterial pharyngitis
- Children from 5 to 15 years old: high risk group
- Most common in the cold months; no seasonal
incidence for soft-tissue infections
Group A Streptococcus: S. pyogenes

Question 8

GAS virulence factors

Answer 8

Just remember (from this slide) that:
-Many virulence factors
-Playing a role in establishing infection
- modify host cell and immune resistance for example

Question 9

anti-phagocytosis

Answer 9

1) M protein
2) Hyaluronic acid capsule hides bacteria from leukocytes
3) Streptolysins (SLO & SLS) lyse phagocytic cells
4) Streptococcal pyrogenic exotoxins B (SpeB) cleaves
IgG bound to GAS (no opsonization)
5) Interfering with ingestion and killing by phagocytes
Group A Streptococcus: S. pyogenes

Question 10

M protein

Answer 10

1) Anti-phagocytic
- Inhibition of alternative pathway activation by:
- Binding to complement control proteins
- can’t access important bacterial structure
2) Adherence to the surface of human epithelial cells
3) molecular mimicry
- >200 serotypes
- M3 and M18 similar to myosin, keratin, laminin

Question 11

why must s. pyogenes be limited pharmocologically?

Answer 11

1) prevent more serious infection

Question 12

facilitating GAS spreading

Answer 12

1) Deoxyribonucleases (DNases)
- Degrade NETs (5/17/24, slide #s41 & 42)
2) C5a peptidase
- Breaks down complement protein C5a (chemokine)
- Decreases movement of white blood cells to the infection
site (**C5a functions as chemotaxis)
3) Hyaluronidase
- Degrade hyaluronic acid in ECM
4) streptokinase
- break down blood clots (fibrin)

Question 13

streptokinase

Answer 13

1) lyse fibrin clots and restore blood flow
2) for MI

Question 14

streptolysins

Answer 14

1) Two distinct hemolysin
- Streptolysin O (SLO): immunogenic, oxygen labile.
- reversibly inhibited by oxygen.
- SLO exerts its hemolytic effect in anaerobic cultures.
- SLS: non-immunogenic, oxygen stable
2) Functions:
- Lyse red blood cells (β-hemolysis by SLS), white blood cells
(anti-phagocytic, slide# 17) , and platelets (SLO & SLS)
- Promote apoptosis in keratinocytes (SLS)

Question 15

streptococcal pyrogenic exotoxin

Answer 15

1) damaging the
plasma membrane of blood capillaries in scarlet fever.
- Superantigens
- They also appear to be involved in the pathogenesis of severe
infection.
2) Streptococcal toxic shock syndrome

Question 16

GAS diseases

Answer 16

1) pharyngitis
2) scarlet fever which can lead to
- acute rheumatic fever
- post streptococcal glomerulonephritis
3) strep throat

Question 17

Post streptococcal glomerulonephritis (PSGN): Type III
hypersensitivity

Answer 17

1) glomerular deposition of immune complexes triggered by
nephritogenic strains of GAS (such as M-49) causes PSGN.
- 1-3 weeks after a
streptococcal throat infection
- or 3-6 weeks in cases of skin infection.
2) Clinical manifestations:
- hematuria, proteinuria, hypertension, edema, and elevation in
serum creatinine.
- Adults may suffer irreversible kidney damage
Group A Streptococcus: S. pyogenes

Question 18

invasive GAS

Answer 18

1) necrotizing fasciitis flesh eating disease

Question 19

diagnosis

Answer 19

1)Skin infections diagnosed by the presence of Gram-positive bacteria
in short chains or pairs
- Rapid strep test used to diagnose respiratory infections
2) Treatment
- Penicillin is effective (for non-invasive lesions)
- Surgical debridement plus penicillin and clindamycin (for invasive
lesions: necrotizing fasciitis and STSS)

Question 20

GBS (s. agalactiae)

Answer 20

1) Pathogenicity
- Often infects newborns (often inoculated at birth) without specific antibodies
- Neonatal bacteremia, meningitis, and pneumonia
- Older immunocompromised patients are also at risk
- Produces enzymes whose roles are not yet understood
2) normally doesn’t affect healthy people

Question 21

CAMP test

Answer 21

1) CAMP factor enhances hemolysis of staphlococcus aureus

Question 22

viridans streptococci

Answer 22

1) lack group-specific carbohydrates
- Cannot be grouped by Lancefield system
- Inhabit mouth, pharynx, GI tract, genital tract, and urinary tract
2) Opportunistic pathogens
3) Can cause meningitis (rare) and endocarditis if it enters the blood
4) Cariogenic bacteria
- lactic acid

Question 23

s. penumoniae (pneummococcus)

Answer 23

1) ⍺-hemolytic cocci that most commonly form pairs (diplococcus)
- Lacks Lancefield antigens
2) Closely related to mitis group of Viridans Streptococci
3) Part of the normal bacterial flora of upper respiratory system

Question 24

polysaccharide capsule

Answer 24

1) playing a critical role in anti-phagocytosis
- Serotype-determining antigen on the organism.
- The basis for antigenic differences among serotypes lies in
the chemical structure of the capsular polysaccharide
2) Target of pneumococcal vaccine
- PPSV23
- PCV (mixing plus conjugating)

Question 25

quellung test

Answer 25

1) identify serotype of polysaccharide capsule
2) Ab is added and reacts with capsular Ag
- flow of medium changes
- swelling of capsule

Question 26

s. pneumoniae surface proteins

Answer 26

1) Psp (Pneumococcal surface protein)
- PspA: antiphagocytic (by inhibiting activation of C3 convertases in
classical and alternative complement pathways)
- PspC: antiphagocytic (by inhibiting C3 convertase formation)
2) PsaA (Pneumococcal surface antigen A)
- Mediates binding of cells to epithelial cells of pharynx
3) Secretory IgA protease
- Destroys IgA

Question 27

pneumolysin

Answer 27

1) A cholesterol-dependent, pore-forming toxin
- Pulmonary, nasal, and tracheobronchial epithelial cells are
damaged as a result of pore-forming activity.
- Breaks down hemoglobin into a green pigment

Question 28

s .pneumoniae disease

Answer 28

Pneumococcal Diseases
* Pneumococcal pneumonia
* Most common disease caused by S. pneumoniae
* Sinusitis and otitis media
* Sometimes occur following viral infections
* Bacteremia and endocarditis
* S. pneumoniae can enter the blood through lacerations or tissue
damage
* Pneumococcal meningitis
* Mortality rate higher than other causes of meningitis

Question 29

s. pneumoniae diagnosis

Answer 29

Diagnosis
* Gram stain of sputum smears
* Differentiation methods of S. pneumoniae from
other viridans streptococci
- Susceptibility to optochin
- An optochin (ethylhydrocupreine hydrochloride) disc
is placed on S. pneumoniae culturing agar plate.
There is the zone of inhibition around the disk 24 hours
after incubation at 37°C.
Ø Solubility in bile salts
o S. pneumoniae: bile soluble

Question 30

s. pneumoniae treatment

Answer 30

1) penicillin
-resistant strains have emerged
2) prevention
- vaccine

Question 31

staphylococci characteristic

Answer 31

Structure and Physiology
* G(+), catalase positive facultative anaerobes
* Cells occur in grapelike clusters
* Non-motile
* Extraordinary capacity to adapt and survive in a great variety of
environments.
* Tolerant of desiccation/heat
* Salt-tolerant
* Tolerate salt deposited on human skin by sweat gland
Staphylococcus: Characteristic

Question 32

staph aureus

Answer 32

primarily found only in moist skin folds
* More virulent strain, most often spread to others by direct contact
* Variety of conditions depending on site of infection

Question 33

staph epidermidis

Answer 33

Normal microbiota of human skin
* Device-related infections, Urinary tract infection (UTI)

Question 34

staph aureus

Answer 34

Producing toxins-mediated diseases
* Exfoliative toxin: Staphylococcal scalded skin syndrome (SSSS)
* Toxic shock syndrome toxin: Staphylococcal toxic shock syndrome
* Enterotoxins produced by the bacteria that colonize food/beverage: Food
intoxication

Question 35

staph aureus structural defenses

Answer 35

1) protein A
- binds IgG
- inhibit opsonin
2) bound coagulase (clumping factor)
-Converts fibrinogen into fibrin molecules
-Fibrin clots hide the bacteria from phagocytic cells
- Synthesize polysaccharide slime layers (capsules)
- Inhibit phagocytosis

Question 36

enzymes staph aureus

Answer 36

1) free coagulase
2) hyaluronidase
3) staphylokinase
4) lipases
5) beta-lactamase

Question 37

staph aureus toxins

Answer 37

1) cytolytic toxins
2) exfoliative toxins
3) TSS
4) enterotoxins

Question 38

staph aureus diseases

Answer 38

1) Noninvasive Disease
* Food poisoning
* Due to ingestion of enterotoxin-contaminated food
2) Cutaneous Diseases
* Various skin conditions
* Staphylococcus scalded skin syndrome (SSSS), impetigo, folliculitis
3) TSS
4) meningitis

Question 39

staph aureus diagnosis

Answer 39

Diagnosis
* Detect Gram-positive bacteria in grapelike arrangements
* Coagulase test

Question 40

staph aureus treatment

Answer 40

Anti-staphylococcal penicillins (nafcillin, oxacillin, and dicloxacillin)
* They were so designated since their R side chains have bulky residues
that prevent binding by the staphylococcal β-lactamases.
* Vancomycin used to treat methicillin-resistant S. aureus (MRSA)
infections