Chapter 17

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1

Most streptococci that contain cell wall antigens of Lacefield group A are known as

Streptococcus pyogenes

2

Members of streptococcus are almost always

beta hemolytic

3

S. progenes is the most common causative agent of

pharyngitis

resultant disorder scarlett fever, skin infection: impetigo

4

In terms of human morbidity and mortality worldwide s. progenies plays an important role in the subsequent development of complications such as

acute rheumatic fever

post streptococcal glomerulonephritis

5

Necrotizing fasciitis is a

rare bacterial infection that can destroy skin and soft tissues beneath it included fat and tissue covering the muscles (fascia)

6

A person with necrotizing fasciitis is sometime said to be infected with

flesh-eating bacteria

7

The most commun type of bacteria causing necrotizing fasciitis is

streptococcus pyogenes

8

a cell protein found in association with hyaluronic capsule is a major virulence factor of s. pyogenes

M protein

9

Strains of S progenies that lack M protein cannot cause

infection

10

M protein inhibits

phagocytosis, and antibody syntheziesed against M protein provides type specific immunity to group A streptococci

11

m protein is the basis for the subclassifications

group A streptococci into more then 60 M serotypes

12

SLO

Streptolysin O an oxygen labile enzyme binds to

sterols in the red blood cells causing stearic rearrangement

13

The arrangement produces

submicroscopic holes in the RBC membrane and hemoglobin diffuses from the cells.

14

SLO is antigenic

the antibody response to it is the most frequently used serologic indicator of recent streptococcal infection

15

Streptolysin S

oxygen stable enzyme, responsible for

beta hemolysis (clear appearing) on the surface of a blood agar culture plate.

16

Streptomycin S disrupts the

selective permeability of the RBC membrane causing sermonic lysis

not antigenic

17

In addition to throat cultures in patients with pharyngitis, antibodies bacterial toxins and other extracellular products that display measurable activity can be tested

antistreptolysin O- ASO

ADN-B

both are standard serological tests.

18

Serological testing should compare

acute and convalescent sera collected 3 weeks apart

19

M protein contributes to invasiveness through its ability

to impede phagocytosis of streptococci by human polymorphonuclear neutrophil PMN leukocytes.

20

Mortality following an outbreak of S progenies that progresses to toxic shock can be as high as

70%

21

toxic shock syndorme is classified as

rare condition because it only affects about 300 people annually.

22

STSS almost never follows a simple

streptococcus throat infection

23

The case definition of streptococcal toxic shock syndrome and necrotizing fasciitis includes serologic confirmation of

group A streptococcal infection by fourfold rise against SLO DNase B. The mean percentage of immature neutrophils can reach 40 to 50%

Blood cultures are positive in 60%of cases.

24

Streptococcus pyogenes

group A strep

beta hemolytic

25

s pyogenes causes

pharyngitis (sore throat)

scarlet fever (sore throat plus rash)

skin infection (impendigo)

acute rheumatic fever

post streptococcal glumerulonephritis

flesh eating infections

toxic shock

26

Strep pyogenes has

m and r antigens

structurally similar but immunological distinct

found on the fimbriae of the bacterial cell and his a major virulence factor

27

strains of s pyognes that do not haveM protein cannot

cause infection

28

M protein inhibits

phagocytosis and is the basis for subclassificaiton infection group A strep into more then 60 serotypes

29

Streptolysin O

oxygen labile antigenic

30

Streptolysin S

oxygen stable not antigenic

dont test for

31

Hyaluronidase

spreading factor, breaks down hyaluronic acid in host connective tissues

32

DNAses

degrade DNA

33

streptokinase-

dissolves clots

34

erythrogenic toxin

elaborated by scarlet fever associated strains, responsible for characteristic rash

35

Immunological test for strep

anti-streptolysin O

anti-DNAase b antibody titer

antihyaluronidase titers

antistreptokinase titers

pcr

36

antistreptolysin o-

an elevated level indicates a relatively recent infection with strep

37

anti-DNAase b antibody titer indicates

recent strep skin infection

38

A recent infection is indicated by a fourfold rise in titer between

acute and convalescent specimens

3 weeks apart

39

False positive results ASO

beta lipoprotein

bacterial contamination for serum sample

oxidation of ASO