Streptococcus Flashcards
Catalase test for streptococcai
Negative
One of the most important characteristics for identification of streptococci is
the type of
hemolysis: Ι-hemolysis, Ξ²-Hemolysis, & non- hemolytic (Ξ³-hemolysis).
Diagnostic feature of streptococcai pyogenesis
Bactriacin sensitivity
Diagnostic feature of streptococcai agalactia
Bactriacin resistance
Diagnostic feature of streptococcai pneumonia
Inhibited by optician, sensitivity
two important antigens of Ξ²-hemolytic streptococci:
C carbohydrates
M protein
most important virulence factor of S. pyogenes
M protein
Transmission of streptococcai occur when
They gain access to tissue and blood
(they are part of the normal flora )
Viridans streptococci and S. pneumoniae are located in the
Oropharynx
S. pyogenes located in the
Skin and orophaynx in small number
S.agalactia located in the ?
Vagina and colon
Entercoccai and anaerobic coccai are located in the ?
Colon
Group A streptococci B- hemolysis (S. pyogenes ) cause disease by three
mechanisms:
1-pyogenic inflammation
2-exotoxin production
3- immunologic
Group A streptococci (S. pyogenes)
Three important inflammation-related enzymes:
Hylurandase
Sterptokinase
DNAase
What toxin related to Group A streptococci (S. pyogenes) causes the rash in scarlet fever
Erythrogenic toxin
What toxin related to group A s.pyogenes important in the diagnosis of
rheumatic fever?
Streptolysin O
What toxin related to group A s.pyogenesis a flesh-eatingβ
streptococci that cause necrotizing fasciitis
Exotoxin B
toxin responsible for most cases of
streptococcal toxic shock syndrome (superantigen)
Pyrogenic exotoxin A
most common
bacterial cause of pharyngitis (sore throat)
Streptococcus pyogenes (group A streptococcus)
3 years old patients suffer from fever. Slapped cheeks rash, strawberry tongue and a sand paper appearance in skin, what is the cause of this condition
Erythrogenic toxin of s.pyogeneis
neonatal sepsis and meningitis. Caused by
Group B streptococci
Caused organism of Endometritis (puerperal fever) and sepsis ξ¨ a
serious infection of pregnant women
Group A streptococci
most common cause of infective
endocarditis. They enter the bloodstream (bacteremia) from the
oropharynx, typically after dental surgery.
Viridans streptococci (s.smiths)
urinary tract infections, especially in hospitalized patients
with urinary catheter.
Caused by which organism
Enterococci
Immunologic cross reaction between antibodies formed against )proteins of S. pyogenes and proteins on the surface of joint, heart and brain tissue
Rheumatic mitral stenosis
β’ Children 5 - 15 years old
2 weeks after a group A streptococ infection usually pharyngitis.
β’ fever, migratory polyarthritis, and carditis. The carditis damages myocardial and endocardial tissue, especially the mitral and aortic valves, resulting in vegetations on the valves.
Acute rheumatic fever
Caused by accumulation of antigen-antibody complexes on the gloumnat basement membrane
Occur after 2-3weeks skin infection by group A streptococci in children
Most common with skin infection (impetigo, cellulitis)
Characterized by hypertension, edema of the face and ankle, and smoky urine
Acute Glomerulonephritis
First choice treatment of Gram positive infections
Penicillin G or amoxicillin,
can be eradicated only by a penicillin or
vancomycin combined with an aminoglycosides.
Enterococcal endocarditis
most common cause of community-acquired
pneumonia, meningitis, sepsis in splenectomized individuals, otitis media, and sinusitis
Streptococcus pneumoniae
On blood agar, they produce Ξ±-hemolysis.
Growth inhibited by optochin
Streptococcus pneumoniae
Infection spreaded by Droplet transmission
Streptococcus pneumoniae
most important virulence factor is the capsular polysaccharide,
and anticapsular antibody is protective.
Streptococcus pneumonia
which activates complement and induces
inflammatory cytokine production in streptococcal pneumonia
Lipoteichoic acid
enhances the organismβs (pneumococci) ability to colonize the mucosa of the upper respiratory tract by
cleaving IgA
IgA protease
sudden chill, fever, cough, and pleuritic pain. Sputum is a
red or brown βrustyβ color.
Caused by a-hemolysis organism
What is the organisim ?
Streptococci pneumonia
the leading cause of sepsis in patients without a
functional spleen
Pneumococci
Laboratory diagnosis results for sputum in streptococcipneumonia
pneumococci are seen as lancet-shaped grampositive
diplococci in Gram-stained smear
drug of choice for the penicillin-resistant
pneumococci.
Vancomycin
Drug of choice in penicillin sensitivity cases
Erythromycin
Drug of choice in severe pneumococcal infection ?
Penicillin G
Drug of choice in moderate pneumococcal infection
Oral penicillin v
An outbreak of serious pneumococcal pneumonia and sepsis among inmates in an overcrowded prison has occurred. Laboratory analysis determined that one serotype was involved. The prison physician said that the pneumococcal vaccine might have limited the outbreak. Which one of the following structures of the pneumococcus is responsible for determining the serotype and is also the immunogen in the vaccine?
- (A) Capsule
(B) Flagellar protein
(C) O antigen
(D) Peptidoglycan
(E) Pilus protein
Capsule
Which one of the following best describes the pathogenesis of rheumatic fever?
(A) An exotoxin produced by Streptococcus pyogenes that acts as a superantigen damages cardiac muscle.
(B) An exotoxin produced by Streptococcus pyogenes that ADP-ribosylates a G protein damages joint tissue.
(C) Antibody to the capsular polysaccharide of Streptococcus pyo-genes cross-reacts with joint tissue and damages it.
- (D) Antibody to the M protein of Streptococcus pyogenes cross-reacts with cardiac muscle and damages it.
(E) Endotoxin produced by Streptococcus pyogenes activates macrophages to release cytokines that damage cardiac muscle.
D) Antibody to the M protein of Streptococcus pyogenes cross-reacts with cardiac muscle and damages it.
Which one of following laboratory tests is the most appropriate to distinguish Streptococcus pyogenes from other B-hemolytic streptococci?
(A) Ability to grow in 6.5% NaCI
(B) Activation of C-reactive protein
(C) Hydrolysis of esculin in the presence of bile
- (D) Inhibition bv bacitracin
(E) Inhibition by optochin
Inhibition bv bacitracin
A 20-year-old sexually active woman reports dysuria and other symptoms of a urinary tract infection. Gram stain of the urine reveals gram-positive cocci. Which one of the following sets of bacteria is most likely to cause this infection?
(A) Staphylococcus aureus and Streptococcus pyogenes
(B) Staphylococcus saprophyticus and Enterococcus faecalis
(C) Streptococcus agalactiae and Staphylococcus epidermidis
(D) Streptococcus pneumonia and Enterococcus faecalis
(E) Streptococcus progenes and Streptococcus pneumonia
Staphylococcus saprophyticus and Enterococcus faecalis
Your patient is a 2-week-old infant who was well until 2 days ago, when she stopped feeding and became irritable. She now has a fever to 38Β°C, developed a petechial rash all over her body, and is very difficult to arouse. In the emergency room, a blood culture and a spinal tap were done. Gram stain of the spinal fluid showed gram-positive cocci in chains. Culture of the spinal fluid on blood agar revealed B-hemolytic colonies that grew in the presence of bacitracin and hydrolyzed hippurate. Which one of the following is the most likely causative organism?
(A) Staphylococcus aureus
(B) Streptococcus agalactiae
(C) Streptococcus mutans
(D) Streptococcus pneumoniae
(E) Streptococcus pyogenes
Streptococcus agalactiae
Infections by which one of the following bacteria are typically treated with penicillins such as amoxicillin, because they exhibit neither low-level resistance nor high-level resistance and synergy with an aminoglycoside is not required in order for penicillins to be effective?
(A) Enterococcus faecalis
(B) Staphylococcus aureus
(C) Staphylococcus epidermidis
(D) Streptococcus pneumoniae
(E Streptococcus pyogenes
Streptococcus pyogenes
Your patient in the emergency room has a 5-cm ulcer on her leg that is surrounded by a red, warm, and tender area of inflam-mation. You do a Gram stain on pus from the ulcer and see gram-positive cocci in chains. Culture of the pus grows small B-hemolytic colonies that are catalase-negative and are inhibited by bacitracin. These results indicate that the organism causing her lesion is most likely:
(A) Enterococcus faecalis.
(B) Staphylococcus aureus.
(C) Streptococcus agalactiae.
(D) Streptococcus pneumoniae.
(E) Streptococcus pyogenes.
Streptococcus pyogenes.
Your patient is a 70-year-old man with endocarditis caused by Enterococcus faecalis. Which one of the following is the best combination of antibiotics to treat the infection?
(A) Azithromycin and trimethoprim-sulfamethoxazole
(B) Chloramphenicol and rifampin
(C) Doxycycline and levofloxacin
(D) Metronidazole and clindamycin
(E) Penicillin G and gentamicin
Penicillin G and gentamicin
