Lecture 6 Flashcards
What are some characteristics of Streptococcus bacteria?
gram+; grow in pairs/chains; catalase negative, some anaerobic and some need high amounts of CO2 to grow
How are streptococcus bacterium classified based on?
hemolytic patterns, serological reactions to cell wall antigens, DNA sequencing, metabolic/biochemical profile
What is the difference between enterococcus and streptococcus?
Enterococcus IS streptococcus! Location is different = enterococcus is in GI tract
How are streptococcus bacterium classified based on hemolytic patterns?
beta vs. alpha/gamma patterns
Which Streptococcus species makes a beta hemolytic pattern and which group do they belong to?
S. pyogenes, Group A Streptococcus (GAS)
Which Streptococcus species makes a beta and gamma hemolytic pattern and which group do they belong to?
S. agalactiae, Group B Streptococcus (GBS)
Which Streptococcus species makes an alpha, beta and gamma hemolytic pattern and which group do they belong to?
E. faecalis and E. faecium, Group D Enterococci
Which Streptococcus species makes an alpha hemolytic pattern and which group do they belong to?
S. pneumoniae, no group
Which hemolytic pattern signifies a negative result?
gamma hemolytic pattern
What disease are S. pyogenes associated with?
strep throat, wound infections, and scarlet fever
What diseases are S. agalactiae (GBS) associated with?
(“B” for “baby”) infant meningitis & pneumonia, sepsis
Signature disease of S. pyogenes?
Strep throat
Signature disease of S. agalactiae?
diseases in infants
What diseases are E. faecalis and E. faecium associated with?
UTI and bacteremia
Signature disease of E. faecalis/faecium?
UTI
What diseases are S. pneumoniae associated with?
respiratory tract infections, bacteremia, meningitis
Signature disease of S. pneumoniae?
respiratory tract infections (ie: pneumonia)
Where are S. pyogenes found?
mouth, skin, throat
Where are S. agalactiae found?
GI tract, female genital tract
Where are E. faecalis/faecium found?
colon
Where are S. pneumoniae found?
mouth and throat
What are the 3 modes of transmission of streptococcal diseases?
direct contact, aerosols, fomites
How do these Streptococcus microbes (found in their normal areas) cause a disease?
when they get to sterile parts or other parts of the body that is other than their native place
Characteristics of S. pyogenes?
spherical cocci, 1.5µm , pairs/chains, optimal growth on enriched-blood agar media, can survive on dry surfaces
What are more virulent S. pyogenes strains characterized by?
presence of a capsule
What are 3 identification tests for S. pyogenes?
catalase (–); PYR (+); bactracin susceptible (–)
What is strep throat (acute pharyngitis)?
infection of the pharynx/tonsils usually in kids less than 3yo
What is scarlet fever?
skin rash; diffuse erythematous rash starts on the chest, spreads to extremities; common in kids
How to test for strep throat?
rapid strep test
What are skin wound infections (pyoderma)?
localized infection; preshcool kids
What is cellulitis?
infection of skin involving subcutaneous tissue
What is necrotizing fasciitis (gangrene)?
deep infection of skin involving destruction of muscle/fat layers; aka “flesh-eating bacteria”; 25% mortality rate
How does S. pyogenes cause gangrene/why can it be called a “flesh-eating bacteria”?
gets into subcutaneous tissue and begins to “eat away” at it = gangrene
What is a protein that is unique to Streptococcus?
M-protein
What is M-protein?
adhesin with anti-phagocytic activity; asissts in infection; can bind to blood proteins
What are the hemolytic toxins S. pyogenes secrete?
Streptolysins S and O
What is a group of exotoxins that S. pyogenes secrete that act as super-antigens?
streptococcal pyrogenic exotoxins (Spes)
What do streptokinase exotoxins that S. pyogenes do?
A and B; cleave plasminogen and lyse blood clots
What does the capsule of S. pyogenes do to act as a virulence factor?
hyaluronic-acid capsule = prevents phagocytosis
What are the 2 anitbiotics prescribed against S. pyogenes?
penicillin and erythromycin (protein synthesis 50S inhibitor)
Characteristics of S. agalactiae?
beta or non-hemolytic, asymptomatic colonization of upper respiratory tract and genitourinary tract
What are 3 identification tests for S. agalactiae?
catalase (–), CAMP and hippurate hydrolysis reactions
What would happen during child delivery if the mother has an infection in her genitourinary tract system?
infection can be passed onto neonate = congenital disease
Diseases associated with S. agalactiae?
neonatal sepsis and meningitis post-delivery; infections acquired during pregnancy or at birth
What virulence factors are associated with S. agalactiae??
polysaccharide capsule
What 2 antibiotics are prescribed against S. agalactiae?
Penicillin G, and vancomycin
Why is CAMP reaction assay the best way to identify S. agalactiae or GBS?
S. aureus enhances GBS hemolysis
Characteristics of Enterococci?
lacks autolysin gene = penicillin only bacteriostatic in these bacteria,
How do enterococcus species cause a UTI if they are normally found in the colon?
can get accidentally passed through the genitourinary tract system = cause infection
Because enterococci strains are becoming more resistant to antibiotics, how do we go about this?
antibiotic combinations
Characteristics of S. pneumoniae?
1 µm gram+ encapsulated diplococcus; alpha-hemolysis (aerobic) and beta-hemolysis (anaerobic)
About how many different serotypes are there with the polysaccharide capsules of S. pneumonia?
~90
What does serotypes mean?
composed of different antigens that will react with different antibodies due to different epitopes (on antigen)
Why is it important to know if we have more than one different S. pneumoniae strain that reacts with different antibodies?
important for vaccine development; need to include different serotypes in vaccine
What are the 5 diseases associated with S. pneumoniae?
otitis media, bacterial sinusitis, chronic bronchitis, bacterial pneumonia, pneuomococcal meningitis
What is otitis media?
middle-ear infection in kids, self-limited disease; not serious infection and goes away w/o antibiotic interference
What is bacterial sinusitis?
acute infection of the paranasal sinuses (patients of all ages)
What is chronic bronchitis?
long-term inflammation of the bronchi in the lungs (supposed to be sterile = but if S. pneumoniae resides area = infection)
What is bacterial pneumonia?
infection of alveoli (sterile) can result into sepsis; high death rate if not treated
What is pneumococcal meningitis?
S. pneumoniae can escape respiratory tract and cause infection in the membrane that surrounds the brain; common in kids
What species of bacteria is the cause of most respiratory tract infections?
S. pneumoniae
What are the 4 virulence factors associated with S. pneumoniae
pneumolysin toxin, adhesins, capsule, cell wall components (peptidoglycan and LTA)
What does the capsule of S. pneumoniae do to act as a virulence factor?
anti-phagocytic activity
What do the adhesins of S. pneuominae do to act as a virulence factor?
binds to IgA antibodies and inactivates them
What do the cell wall components of S. pneumoniae do to act as a virulence factor?
contribute to inflammation
What does the pneumolysin exotoxin of S. pyogenes do to act as a virulence factor?
forms cell pores (Type II exotoxin) contributes to lung damage
How serious is bacterial pneumoniae?
500K cases/yr USA; 1M+ deaths worldwide/yr
When do bacteria usually migrate from their original reservoir to infect another area?
usually when there’s another infection taking place = easier for other microbes to migrate (via macrophages) and infect
If bacteria utilizes macrophages to migrate and spread/infect, how does the macrophages not kill these bacteria?
the capsule protects the bacteria well
What is one diagnostic of S. pneumoniae damage to the lungs?
X-ray = helps physically see the damage of the lungs
How can otitis media happen if S. pneumoniae resides in throat and mouth?
it can move up and colonize nose = gives opportunity for access to the middle ear
What are common symptoms associated with S. pneumoniae infections?
severe shaking chills, high fever, productive cough w/ bloody sputum, CP (chest pain)
What are the 5 antibiotics prescribed against S. pneumoniae?
penicillin, vancomycin, cephalosporins, chroramphenicol, erythromycin
What is the pneumococcal vaccines currently in use for kids?
7-valent (and 13-) pneumococcal conjugative vaccine (PCV-13)
What is the pneumococcal vaccines currently in use for adults?
23-valent pneumococcal polysaccharide vaccine (PPSV-23)
When refering to the pneumococcal vaccines, what does “valent” stand for and the numbers associated with it and why?
stands for the different serological types since S. pneumoniae has ~90 different serological capsule types
Why must there be a different vaccine for kids?
current pneumococcal vaccines uses carbohydrate as part of the antigen = kids immune systems do not yet respond to polysaccharide agents = need to attach protein to polysaccharide antigen so kids’ immune systems can recognize it
How many doses of the PCV vaccine is required for kids?
4 doses within 15 months
