Bacteriology 8: Streptococcus/Enterococcus Flashcards
Streptococcus morphology
Gram (+)
Cocci
Most arranged in chains (except S.pneumomiae)
Most members of the Streptococcus family commonly are found where?
As a normal flora of the mouth and gut EXCEPT S.pyogenes
lol
How does streptococcus differentiate from staphylococcus with the catalase test and salt test
Staphylococci = all of them are catalase (+) therefore must do a coagulase test to exclude S.aureus. All of them are also salt tolerant in the mannitol-salt test.
Streptococci = all of them are catalase (-) and not salt tolerant
Therefore we can distinguish staph and strep with a catalase test and a mannitol-salt test
How are most streptococci classified in the lancefield group
Based on a carboyhydrate antigen found on the cell wall
Group A Streptococci (GAS): Includes Streptococcus pyogenes, which causes strep throat, scarlet fever, and rheumatic fever.
Group B Streptococci (GBS): Includes Streptococcus agalactiae, which is a major cause of neonatal infections
Cell wall = peptidoglycan layer
Not all streptococci can be classified by this system, though; for example, Streptococcus pneumoniae don’t fit into the Lancefield groups.
Alpha-hemolytic streptococcus species
Can be further classified with optochin-sensitive vs. optochin-resistant
optochin-sensitive
-streptococcus pneumoniae
optochin-resistant
-Group D and viridans streptococci
Beta-hemolytic streptococcus species
Can be further classified b/w bacitracin-sensitive and bacitracin-resistant
bacitracin-sensitive
-group A streptococci (Streptococci Pyogenes)
bacitracin-resistant
-group B, C streptococci
Virulence factors- surface antigens for GAS
M-protein
More than 100 stereotypes of M protein = pathogenic
The more pathogenic forms can cause serious sequelae of strep throat like rheumatic fever (b/c autoimmune rxn)
M-protein
-inhibit phagocytosis
-inactivates the complement system
-Antigenic
sticking out of the capsule in bacteria like Protein F, protein G and the M protein and lipoteichoic acid (b/c gram (+))
Virulence factors- surface antigens for GAS
Protein G
Binds to the Fc portion of antibodies, thereby interfering with/ opsonization
sticking out of the capsule in bacteria like Protein F, protein G and the M protein and lipoteichoic acid (b/c gram (+))
Virulence factors- surface antigens for GAS
protein F
Responsible for attachment to host cells
sticking out of the capsule in bacteria like Protein F, protein G and the M protein and lipoteichoic acid (b/c gram (+))
Virulence factors- surface antigens for GAS
Hyaluronic acid capsule
Inhibits phagocytosis
(We know this… capsule = virulence factor)
Virulence factors- surface antigens (GAS)
Group A carbohydrate
Protection against lysozyme
(We know that the lysozyme is an enzyme that will cleave the peptidoglycan cell wall- specifically the glycosidic bond b/w NAG-NAM carbohydrate backbone)
Therefore group A carbohydrate surface antigen must be imbedded w/n the cell wall to protect against lysozymes.
It anchors on top of the the cytoplasmic membrane (inner membrane)
Which surface antigens (virulence factors) are found outside the capsule for possible antibody interaction on GAS?
Protein G
Protein F
M protein
The hyaluronic acid = capsule
Group A carbohydrate = from outer surface of inner membrane to top layer of cell wall (peptidoglycan layer)
Virulence factors - toxins (GAS)
Streptococcal pyrogenic exotoxins (SPE)
Erythrogenic toxins b/c they cause the skin to redden
-they cause the red rash that isass. w/ scarlet fever
-superantigen ass. w/ toxic shock syndrome**
Virulence factors - toxins (GAS)
Streptolysin O
Causes lysis of RBCs, leukocytes, and platelets but only under anaerobic conditions
Virulence factors - toxins (GAS)
Streptolysin S
Causes lysis of RBCs, leukocytes, and platelets but under both under anaerobic conditions and aerobic
Virulence factors - enzymes (GAS)
-streptokinase
Dissolves blood clots
(We know this… kinases will dissolve the blood clots created by a coagulase enzyme for virulence factor)
Virulence factors - enzymes (GAS)
C5a peptidase
Degrades C5a from the complement cascade and prevents the recruitment of neutrophils
Virulence factors - enzymes (GAS)
-hyaluronidase
The primary function of hyaluronidase is to degrade hyaluronic acid, a key component of the extracellular matrix, particularly in connective tissues.
Hyaluronidase is an enzyme produced by several types of bacteria, including Streptococcus, Staphylococcus, and Clostridium species, as well as some other organisms.
Name all the virulence factors describes as toxins, enzymes, and surface antigens under a streptococcus bacteria (GAS)
Surface antigens
-M protein
-Protein G
-Protein F
-Hyaluronic acid capsule
-Group A carbohydrate
toxins
-SPE
-streptolysin O
-Streptolysin S
enzymes
-streptokinase
-C5a peptidase
-hyaluronidase
URS infection caused by streptococcus group A (GAS)
Strep. Pharyngitis
GAS = S.pyogenes
Skin infection caused by streptococcus group A (GAS)
Impetigo
Soft tissue infections caused by streptococcus group A (GAS)
Skin trauma/infection spreads into surrounding lymph nodes and tissues
Erysipelas
-involves the epidermis and upper dermis
cellulitis
-involves both the superficial and deep layers of the skin (dermis and subcutaneous fat)
can progress to deeper tissues or sepsis in the very young, very old, and immunocompromised
Necrotizing Fasciitis
-“flesh-eating disease”
-necrotizing fasciitis is a severe and rapidly progressing soft tissue infection. It primarily affects the fascia, which is a layer of connective tissue that surrounds muscles, nerves, and blood vessels.
-starts as a minor infection or break in the skin, then progresses rapidly in the fascia, resulting in the destruction of muscle/fat tissue due to a variety of enzymes and toxins.
therefore it invades the CT and muscle
Streptocococcal toxic shock syndrome (STSS)
Can begin at the site of any S.pyogenes infection, often ass. w/ necrotizing fasciitis.
-this is a systemic condition that spreads rapidly leading to septic shock (patients die often w/n 2-3 days) if you survive = multiple amputations
-caused by superantigen
Toxic shock syndrome can be caused by what bacteria and what virulence factors
-streptococcal pyogenes (GAS)
- staphlylococcus aureus
=superantigen
=hypotension, fever, rash, desquamation of skin (palms and soles) multiple organ failure = TSS
S.aureus
-TSST-1 is a toxin = (virulence factor) that is produced by 15% of S.aureus bacteria.
-TSST-1 = superantigen. Bacteria stays local while toxin goes to bloodstream = systemic
-use of tampons, nasal surgery
streptococcal pyogenes (GAS)
-streptococcal pyrogenic exotoxins (SPE) = virulence factor that is produced by S.pyogenes
-SPE = superantigen.
Group B of streptococcus (GBS)
S.agalactiae
General characteristic of GBS
-found where
-commonly causes
-capsule made of vs. in GAS
-can it cause homlysin? What about GAS?
-resistant or sensitive ?
-enzyme?
-normal flora of the GI tract and vagina
-serous neonatal diseases - newborns
-Sialic acid capsule vs. Hyaluronic acid capsule (both inhibit phagocytosis b/c that’s the effect of having a capsule as a virulence factor)
-both GAS/GBS are ass. w/ Beta-hemolytic.
-Bacitracin resistant
-Hyaluronidase = degrade hyaluronic acid = a key component of the ECM, particularly in CT.
Diseases caused by GBS
-neonates
-infants
-pregoo
-men/non-pregoo
neonates
-bacteremia —> sepsis —> meningitis
infants
-bacteremia —> meningitis
preggo women
-UTI
Men/non-preggo
-bacteria —> pneumonia, bone/joint infections
S.pneumonia
-lancefield group?
Streptococcus pneumoniae, also known as the pneumococcus, does not belong to any of the Lancefield groups (A, B, C, etc.), as it lacks the specific carbohydrate antigens used in the Lancefield classification system. Instead, it is classified based on its biochemical properties and capsular serotypes.
S.pneumoniae (pneumococcus)
-hemolytic?
-shape?
-found?
-transmission?
-Alpha-hemolytic
-diplococci
-normal flora
-person-to-person (40% infections)
-endogenous (healthcare-ass.)
S.pneumoniae virulence factor
-capsule
Inhibits phagocytosis
S.pneumoniae virulence factor
-Phosphocholine
Part of the cell wall that facilitates entry into respiratory cells and into the bloodstream
Therefore part of the peptidoglycan cell call of bacteria
S.pneumoniae virulence factor
-Pneumolysin
Pore-forming toxin that lyses pulmonary cells which facilitates the movement of bacteria into alveoli therefore disrupting cilia of the respiratory tract
S.pneumoniae virulence factor
-IgA protease
Cleaves IgA
Lobar pneumonia
-bacteria
-organ affecting
-clinical manifestations
-S.pneumoniae
-fast onset
-affects one/more lobes of the lungs
-fever, chills, congestion, productive cough, chest pain, short/rapid breathing, blood in sputum
Vaccine for Streptococcus
S.pneumoniae
-prevnar (13 valent)
Infants
-pneumovax (23 valent)
Young adults who smoke cigarettes
adults >65
S.pneumoniae infections
URS
-sinusitis
-Ottis media
nervous system
-bacteremia —> meningitis
CVS
-acute endocarditis
Viridans streptococci
four groups
-S.mutans
-S.salivarius
-S.mitis
-S.anginosus
General characteristic of viridans streptococci
-hemolytic?
-shape
-lancefield?
-catalase?
-found?
-alpha hemolytic
-short and long chains
-no lancefield
-catalase (-) = ALL STREPTOCOCCUS
-oral microbiota
some are opportunistic pathogens causing subacute infective endocarditis
Which Streptococci bacteria is found mainly in dental plaque and is one of the main causative agents of enamel and root surface caries?
S.mutans group
Dental plaque found in tooth decay or w/ caries
(Viridans streptococci)
Which Streptococci contributes to biofilm formation in the oral cavity and how?
S.mutans
Scavenge dietary sugars efficiently and convert them into acids (lactate)
Make extracellular soluble and insoluble polysaccharides from sucrose
This contributes to biofilm formation
S.sobrinus
Ass. w/ human dental caries
S.salivarius
Preferentially colonize mucosal surfaces, especially the tongue. Produces large quantities of an unusual extracellular fructan from sucrose
S.vestibularis
Part of the S.salivarius group
Isolated from vestibular mucosa of the mouth
DOES NOT produce extracellular polysaccharides from sucrose like the S.mutans group (S.mutans/S.sobrinus)
Instead they have urease to generate ammonia and raise the local pH.
H2O2: stop the growth of competing bacteria
S.mitis group
S.sanguinis
S.gordonii
S.mitis
S.oralis
What are the 2 most common streptococcal species in the mouth?
S.oralis
S.mitis
Some but not all strains produce extracellular glucan from sucrose
Which Streptococci removes sialic acid from oligosaccharide side chains of salivary mucins?
S.oralis (part of the S.mitis group = viridans strep)
S.oralis produce Neuraminidase and IgA protease potentially promoting bacterial adhesion and colonization in the mouth.
Salivary mucins are glycoproteins found in saliva that play an important role in maintaining oral health.
Sialic acid is often the terminal sugar on glycoproteins like mucins. By removing it, Streptococci can access underlying carbohydrates, which they can then metabolize for energy.
This process is important for the bacteria’s ability to colonize and persist in the oral cavity, as it allows them to utilize components of saliva as a nutrient source.
Which streptococci does not produce extracellular polysaccharides from sucrose?
-S.vestibularis (from S.salivarius group)
-S.anginosus
-S.constellatus (from S.anginosus group)
-S.intermedius (from S.anginosus group)
Which streptococci produces extracellular polysaccharides from sucrose?
-S.mutans group (S.mutans and S.sobrinus)
S. salivarius does produce extracellular polysaccharides, but it is less known for this compared to S. mutans and S. sobrinus. Its polysaccharides are typically less involved in caries formation. They produce large quantities of fructan from sucrose
Some species within the S. mitis group, such as Streptococcus oralis, are known to produce extracellular polysaccharides from sucrose. These polysaccharides can contribute to plaque formation but are generally less cariogenic compared to those produced by Streptococcus mutans and Streptococcus sobrinus.
Which streptococci is the causative agents of serious, purulent diseases and abscesses of internal organs?
S.anginosus group (S.anginosus, S.constellatus, S.intermedius)
DO NOT** produce extracellular polysaccharides from sucrose instead they are the causative agents of purulent diseases and abscesses of internal organs
Enterococcus morphology
-gram +/-
-shape
-enzyme
-catalase
-anaerobic/aerobic
-found in
Gram (+)
Short chains/diplococci
Gelatinase: allows adhesion to dentin
Catalase negative But yet SALT TOLERANT
ONLY GRAM (+) BACTERIA THAT IS SALT TOLERANT
Catalase (-) like all Streptococci
-Faculative anaerobic
-normal microbiota of intestinal tract, urethra, female genital tract
*can also grow in low and high pH)
s.pneumoniae is also Diplococci
Which is the only gram (+) bacteria that is catalase (-) and salt tolerant?
Enterococcus = only gram (+) bacteria that grows in salt
All streptococcus are catalase (-)
All staphylococcus are catalase (+) only these are salt tolerant
All of them are gram (+)
Which bacteria are the most common for being catalase (-) and gram (+)
Enterococcus and streptococcus
Where are enterococcus bacteria commonly isolated from
Patients in ICUs
Enterococcus bacteria is a major cause of infection in hospitals
Ass. w/ abdominal surgery, catheters, peritoneal dialysis and nosocomial UTIs, bacteremia, soft tissue, and intra-abdominal infections
Which bacteria is a common nosocomial infection?
Enterococcus
major cause of infection in hospitals
Enterococcal infections
-opportunistic UTI
-Bacteremia
-secondary endodontic infections (E.faecalis can invade dentinal tubules)
Which bacteria is common found in infected root canals, periodontal pockets that fail to respond to therapy and can invade dentinal tubules?
Enterococcus
Which enterococcus bacteria is most frequently isolated in low numbers from different oral sites?
Enterococcus
