-
What is the general characteristics of streptococci and enterococci (G(-/+), oxygen requirement, catalase, oxidase, non-motile)
- G (+) cocci in chains or diplococci
- facultative anaerobes
- requires enriched media with blood or serum
- catalase (-)
- oxidase (-)
- non motile
-
streptococcus antigen (lancefield groupings)
- applies only to B hemolytic strep
- strep antigens are grouped in A, B, C, F, and G
- enterococci share D group with D group strep but are non hemolytic
-
what are a hemolytic strep also called
viridans
-
what are the viridian's group
- anginosus
- mitis
- mutans
- salivarius
- bovis
-
what are examples of B hemolytic streptococci (2)
- s. progenies: group A
- S. agalactiae: group B
- S.anginosus
- S. dysgalactiae
-
what are some examples of viridans streptococci
- s. pneumoniae: encapsulated
- anginosus, minis, mutans, salivarius, bovis groups
-
what are some examples of enterococcus (2)
-
aerococcus is similar to what group of strep and why
-
what is the blood growth of streptococcus pyogenes
- optimal growth on blood agar
- small colonies with large B hemolytic zones
-
what is the antigenic determinants on the cell surface of streptococcus pyogenes
- Group A antigen
- M protein: differs between strains
- lipoteichoic acid and F protein: facilitate binding to host cells.
-
what are the virulence factors of S. pyogenes (3)
- hyaluronic acid capsule: imitates hyaluronic acid in connective tissue and masks the bacteria from immune system
- M proteins: interfere with phagocytosis
- C5a peptidase: protects bacteria from early clearance from infected tissues
-
what are the molecules involved with attachment and invasion of host cells for S. pyogenes
- lipoteichoic acid: binds to fibronectin and epic cells
- M proteins and F protein: adhesions binding to specific host cell receptors
-
what kind of antigens are streptococcal pyrogenic exotoxins (SpeA, SpeB, SpeC, SpeF)
superantigens
-
what are the toxins and enzymes released by s. pyogenes
- streptolysin S
- streptolysin O
- streptokinase A and B
- DNAses A to D
-
what is the function of streptolysin S and where is it produced
- oxygen stable, nonimmunogenic, hemolysin
- stimulates release of lysosomal contents after engulfment, causing death of phagocyte
- produced in presence of serum (hence "S")
-
what is the function of streptolysin O
- oxygen sensitive hemolysin
- lyses RBC, leukocytes, platelets
-
what inhibits streptolysin O
cholesterol in skin lipids, prevents ASO antibodies do not form in skin infections
-
what antibody is used to detect streptolysin O
antistreptolysin O (ASO) antibodies
-
what is the function of streptokinase A and B
- destroys blood clots and fibrin deposits.
- spreading factor for s. pyogenes
-
function of DNAse A to D
cleave DNa in pus
-
what group is s. pyogenes
Group A strep
-
where is group A strep found in the body
- oropharynx by transient colonization
- not considered part of a healthy, stable microbiome
-
what are the noninvasive diseases caused by s. pyogenes and how are they caused
- pharyngitis: "strep throat"pyoderma: skin infection
- infections caused before immune system produces antibodies or before normal microbiome organisms out compete them through respiratory droplets/ skin
-
what are diseases caused by s. pyogenes that affects the throat
- pharyngitis: strep throat
- scarlet fever: complication of pharyngitis
-
how does scarlet fever present itself
- occurs when infecting s. pyogenes train is lysogenized by bacteriophage that mediates production of a pyrogenic (fever inducing) exotoxin
- rash
- strawberry tongue: yellow white coat on tongue
-
what are the skin infections caused by s. pyogenes
- pyoderma
- impetigo
- erysipelas
- cellulitis
-
what is pyoderma
- any pyogenic (pus producing) skin disease
- pyoderma=impetigo
-
what is impetigo
- confined infection of the superficial layer of skin, with papules that can get crusty
- rarely leads to systemic infection
-
what is erysipelas
- infection of epidermis and involves the lymphatic system
- bright red, salmon colored skin
- includes pain, inflammation, and lymph node enlargement
-
what is cellulitis
- skin infection involving subcutaneous layers of skin and produces systemic symptoms of fever, chills, malaise
- can develop into necrotizing fasciitis
-
what is necrotizing fasciitis
- infection of deep layers of skin including fascia (connective tissue).
- includes late stage infections that spreads into fat, fascia, and muscle tissue
-
what are the hallmarks of necrotizing fasciitis
- toxicity
- multi organ failure
- death
-
what is the treatment to necrotizing fasciitis
extensive surgical intervention, cutting dead infected tissue
-
what is the difference between streptococcal TSS from staphylococcal TSS
streptococcal TSS has bacteremia and necrotizing fasciitis
-
what is the difference between strains of s. pyogenes that cause TSS and pharyngitis
strains that cause TSS have mucopolysaccharide acid capsules and pyrogenic exotics (SpeA and SpeC)
-
what kind of fever is a complication of pharyngitis
- rheumatic fever: involving inflammation of heart, joints, blood vessels.
- affects mainly adults>children
-
what are some clinical diseases associated with s. pyogenes
- streptococcal toxic shock syndrome
- rheumatic fever
- acute glomerulonephritis
-
what are the lab tests used to ID s. pyogenes
- immunoassays: from throat swabs
- nucleic acid amplification: sensitive, test of choice
- antibody detection: ASO
- physiological test: bacitracin susceptibility
-
what is the effectiveness of gram stains for detecting s. pyogenes
- gram stains are useful for s. pyogenes soft tissue infections
- not useful for throat specific because there are too many various strains of streptococci in the normal throat microbiome
-
what is the antibiotic treatment of s. pyogenes
- penicillin/ amoxicillin
- cephalosporin/ macroslide for ppl with penicillin allergies
-
what type of group strep are not normally found in healthy microbiomes
group A
-
what is the treatment for s. pyogenes
- antibiotics
- surgical removal
- intravenous antibiotics
-
what group is streptococcus agalactiae
group B antigen
-
what are the identifying serological markers
- group specific cell wall polysaccharide B antigen
- specific capsular polysaccharides
- surface proteins (most common is c antigen)
-
what is the virulence factor of s. alagactiae and how does it commonly infect the type of people
- contains polysaccharide capsule
- neonates take longer to develop antibodies so they are most affected by S. Agalactiae infections
- genital colonization has been associated with increased risk of premature delivery
-
describe s. agalactiae induced early onset neonatal disease
- acquired in utero/first week in life
- bacteremia, pneumonia, meningitis
- mortality rate <5%
- <30% of infants who survive meningitis have severe neurological disorders: blindness, deafness, mental retardation
-
what is the required test for suspected s. agalactiae early onset neonatal disease
examination of CSF (cerebral spinal fluid) for suspected meningitis
-
describe late onset neonatal disease induced by s. agalactiae
- develops between 1 week and 3 months of age
- bacteremia with meningitis
- low mortality rate <3%
- neurological complications common 25-50%
-
what is the treatment of S. Agalactiae
- GBS susceptible to penicillin
- pregnant women are screen for colonization at 35-37 wks gestation
- prophylactic antibiotics are administered to colonized pregnant women
-
what are the general characteristics of streptococcus pneumoniae
- polysaccharide capsules
- G(+) cocci, in pairs or chains
- a- hemolytic
- colonies are mucoid, large and green
- phosphorylcholine: unique to S. Pneumoniae cell walls and plays a role inc ell wall hydrolysis
-
what are the enzymes S. Pneuomoniae release pathogenesis
- secretory IgA protease and Pneumolysin: similar to streptolysin O, prevents envelopment and clearing
- amidase, peptidolygcan, teichoic acids, pneumolysin: attract inflammatory immune cells to site of pneumococcal infection
-
what are the virulence factors of S. Pneumoniae
- surface protein adhesins
- secretary IgA protease
- pneumolysin
- amidase
- phosphorylcholine
- H2O2
- capsules
-
what is phosphorylcholine
molecule in cell wall that binds to receptors on host cells which allows pneumococci to enter cells and protects from opsonization
-
what part of the body is pneumococci in the normal flora
nasopharynx and throat
-
what are the common clinical disease pneumococci can cause
- sinusitis
- otitis: ear infection
- meningitis
- pneumonia
- bacteremia
-
how can s. pneumoniae be tested
- gram stain of sputum
- immunoassays: for C polysaccharide
- soluble in bile
- difficult to culture
- optochin sensitivity: to ID s. pneumoniae from other G(+) cocci
-
what antibiotics are S. Pneumoniae resistant to
-
what are the general characteristics of virdans streptococci
- majority are non hemolytic and a-hemolytic
- G (+)
- highly antibiotic resistant
- rarely found on skin surface
- need 5-10% CO2 for growth
-
what are the five sub groups of virdans
- anginosus
- mitis
- salivarius
- mutans
- bovis
-
enterococcus general characteristics
- initially Group D strep
- G(+) cocci in pairs/ chains
- non hemolytic
- grow aerobically and anerobically
- wide pH range (4.6-9.9)
- grows in high salt and bile concentrations
- highly antibiotic resistant
- infections are nosocomial
-
what part of the body are enterococcus a part of the normal microbiome
gut and genitourinary tract
-
what are the virulence factors for enterococcus
- not many virulence factors
- surface proteins
- membrane glycolipids
- gelatinase
- pili
-
what are clinical diseases caused by enterococcus
- UTI
- peritoneal infections: caused by trauma or other disease
- bacteremia
- endocarditis
-
what are some of the tests used to differentiate enterococcus
nucleic acid test
|
|
