Streptococcaceae and Other Related Genera Flashcards
When comparing staph and strep colonies, what are the differences?
- Staph is opaque
- Strep is “transparent” (or at least not as opaque)
Alpha (or gamma) hemolytic Streps
- Group D
- S. pneumoniae
- Enterococcus sp.
- Alpha Strep (not Group D)
Beta hemolytic Streps
- Group A
- Group B
- Group D (rarely beta hemolytic)
- Enterococcus spp. (rarely beta hemolytic)
- Beta Strep (not Group A, B, or D)
S. pneumoniae characteristic features on a plate
- Colonies are often depressed in center (autolysis) or mucoid (encapsulated)
Throat cultures (strep screens) must be incubated ____?
Anaerobically
Streptolysin O is ____ ____
Oxygen labile
Streptolysin S is ____ ____
Oxygen stable
Principle of the Lancefield grouping test
Grouped by “C substance” in cell wall
Streptococci
- Catalase (pos/neg)
Catalase negative
Bile Esculin hydrolysis
- Principle
To determin an organism’s ability to hydrolyze esculin to esculetin in presence of bile. Esculetin reacts w/ Fe citrate in medium to form black ppt
Bile Esculin agar
- What do pos/neg tests look like?
Pos: blackening of medium
Neg: no blackening
LAP
- Principle
To determine organism’s ability to produce the enzyme leucine aminopeptidase, which will hydrolyze leucine-a-naphthylamide disk
LAP
- What do pos/neg tests look like?
Pos: red
Weak pos: pink
Neg: yellow
- 5% NaCl
- Principle
To determine an organism’s ability to grow in a high salt environment (6.5%)
- 5% NaCl
- What do pos/neg tests look like?
Pos: turbid
Neg: clear, no change
PYR
- Principle
To determine an organism’s ability to produce the enzyme pyrrolidonyl peptidase
PYR
- What do pos/neg tests look like?
Pos: red
Neg: no color change
Optochin susceptibility test
- Principle
To determine an organism’s susceptibility to the chemical optochin (ethylhydrocupreine hydrochloride)
Optochin susceptibility test
- What do pos/neg tests look like?
Pos: zone of inhibition >= 14 mm
Neg: no zone of inhibition
Bile solubility
- Principle
To determine the ability of organisms to lyse in presence of bile salt (sodium desoxycholate)
- Plate and tube method
Bile solubility
- What do pos/neg tests look like?
Plate
- Pos: disintegration of colony under desoxycholate drop (flat hemolyzed area remains)
- Neg: no visible change under desoxycholate drop
Tube
- Pos: clearing of “test” but “control” remains turbid (cloudy)
- Neg: both tubes (“test” and “control”) remain turbid (cloudy)
Quellung test
- Principle
To determine the ability of the organism’s capusle Ags to bind to known Abs forming a precipitate. Visualized w/ the addition of methylene blue to the slide
Quellung test
- What do pos/neg tests look like?
Pos: capsule looks opaque and appears to enlarge around dark blue-stained cell
Neg: no appearance of a clear, enlarged halo surrounding stained cell
Bacitracin
- Principle
To detect an oganism’s susceptibility to the anitmicrobial agent bacitracin. Filter paper disks impregnated w/ bacitracin are sued to determine susceptibility or resistance
Bacitracin
- What do pos/neg tests look like?
Pos: zone of inhibition
Neg: no zone of inhibiton
CAMP test
- Principle
To detect presence of CAMP factor produced by certain organisms that will enhance the beta-hemolytic activity of S. aureus on SBA
Sodium Hippurate
- Principle
Hippuric acid is hydrolyzed to benzoic acid and glycine by hippuricase. Glycine end product is detected by addition of ninhydrin reagent
Sodium Hippurate
- What do pos/neg tests look like?
Pos: dark blue to purple color
Neg: no color change
Other grouping tools for determining Streptococcus and Enterococcus
- Ag testing (in/direct)
- Fluorescent Ab (esp. Group A)
- Kit systems (API, Vitek, etc.)
Latex agglutination
- Principle
To dtect certain Ags or Abs in a variety of bodily fluids (blood, saliva, urine, CSF). Sample to be tested is sent to the lab where it’s mixed w/ latex beads coated w/ a specific Ag or Ab.
Coagglutination
- Principle
Method used for organism identification using specific, known commercial Abs taht have been attached to a dead bacterium, most often Staphylococcus. Dead Staphylococcus act similarly to a latex bead, allowing Ag-Ab reaction to be visible to the naked eye
Coagglutination
- What do pos/neg tests look like?
Pos: visible agglutination w/in 1-2 minutes
Neg: remain smooth
2 types of Ag testing for Streptococcus and Enterococcus sp.
Latex agglutination and coagglutination
Who is/are PYR positive?
- Group A
- Enterococcus spp.
Who is/are NaHippurate positive?
- Group B
Who is bacitracin susceptible?
Group A
What Strep are LAP positive?
All of them we work with in the lab
What test did we use coagglutination on in the lab?
Group B
Who is/are quellung test positive?
S. pneumoniae
Name all of the ALPHA and gamma hemolytic Strep
- S. pneumoniae
- Enterococcus sp.
- Alpha Streptococci (Group D)
- Alpha Streptococci (not Group D)
Who is/are CAMP positive?
Group B
Tests to run on when you have catalase negative GPCs that are alpha/gamma hemolytic
- Esculin
- NaCl
- PYR
- Bile solubility
- Optochin
Name all of the BETA hemolytic Strep
- Enterococcus sp (rare)
- Beta Streptococci (Group D) (rare)
- Beta Streptococci (Group A)
- Beta Streptococci (Group B)
- Beta Streptococci (not Group A, B, D)
Who is/are bile solubility positive?
S. pneumoniae
Tests to run when you have catalase negative GPCs that are beta hemolytic?
- PYR
- Esculin
- Bacitracin
- CAMP
- NaHippurate
- Coagglutination (not specific for group B but that’s what we used it for)
Who can be a pseudocatalase (weak catalase positive)?
Enterococcus sp.
Who is/are positive for bile esculin?
- Enterococcus sp
- Alpha Streptococci (Group D)
Who is/are optochin susceptible?
S. pneumoniae
Who is/are NaCl positive?
- Group B
- Enterococcus sp
Group A/S. pyogenes
- Hemolysis
- 2 positive/susceptible tests
- Beta
- Bacitracin susceptible
- PYR positive
Group B/S. agalactiae
- Hemolysis
- 3 positive tests
- Beta
- CAMP pos
- NaCl pos
- NaHippurate pos
Not Group A, B, or D are otherwise known as…?
Group C, G
Group D/S. bovis
- Hemolysis
- 1 positive test
- Usually alpha or gamma (rarely beta)
- Esculin pos
S. pneumoniae
- Hemolysis
- 3 positive tests
- Alpha
- Optochin susceptible
- Bile solubility pos
- Quellung pos
Enterococcus sp
- Hemolysis
- 3 positive tests
- Alpha (rarely beta)
- Esculin pos
- NaCl pos
- PYR pos
Virulence factors of Group A
- M protein
- Pyrogenic/erythrogenic toxin
- Streptokinase/fibrinolysin
- Hyaluronidase
M protein
Major virulence factor in Group A Strep; resistant to phagocytosis
Pyrogenic/erythrogenic toxin
Causes the rash of scarlet fever
Streptokinase/fibrinolysin
Fibrinolysin is the breakdown of fibrin; allows infection to spread (cellulitis, erysipelas)
Hyaluronidase
Break down of ground substance; allows infections to spread
Pyogenic streptococci
“pus forming”
- Group A
- Group B
- Groups C, G
Common infections caused by Group A Strep
Throat and wound
- “Strep throat”, tonsillitis
- Scarlet fever
- Impetigo
- Erysipelas
- Cellulitis
- Necrotizing fasciitis
What type of toxin is a pyrogenic toxin?
Exotoxin
Group A Strep
- Lacefield group
- ____ colonies w/ ____ zone of beta hemolysis
- Lancefield group A
- Large colonies; large zone
Streptococcal Toxic Shock Syndrome
- Cause by which group of strep?
Group A
Group A Post streptococcal diseases
- Acute glomerulonephritis
- Rheumatic fever
Acute Glomerulonephritis
- Caused by…
- Time of infection?
- Ag-Ab complexes causes inflammation of glomeruli (NOT an infection of the kidneys)
- Occurs 1-2 weeks following pharyngitis or skin infection w/ Group A
Acute Rheumatic Fever
- Cause
- Location of disease
- Patient population
- Time of infection?
- Cross-reaction b/w strep Ag and cardiac tissue
- Results in damage to heart valves
- Most frequent in 5-15 year olds
- Occurs 2-4 weeks after pharyngitis
Oxygen requirements for Streptococcus Genera
Aerobic or facultative anaerobic
Throat cultures are usually ordered for what group of strep?
Group A; other beta strep aren’t often treated
SXT plate
Inhibits normal flora allowing Group A to grow
SBA is incubated ____ for Group A “strep screens”
Anaerobically
Throat “rapid strep screens”
- Direct Ag detection of Group A strep
- ____ specificity, ____ sensitivity
- Ag-Ab interaction b/w Ag in specimen and Ab in test kit
- High; Low → conclusive for pos tests; if patient is symptomatic and direct Ag test is negative, culture should be performed
Group A strep treatment
GROUP A STREP IS UNIVERSALLY SUSCEPTIBLE TO PENICILLIN
Group B strep
- Lancefield group
- ____ colonies, ____ hemolytic zone compared to Group A
- Lancefield Group B
- Large; smaller
Group B strep may be part of normal ____ flora
Urogenital
Infections caused by Group B
- Meningitis/septicemia in newborns
- Female genital and UTIs
- Post-partum infections
CDC guidelines for Group B strep culture during pregnancy
- Should be done for all pregnant women at 35-37 weeks gestation
- Culture/screen should include vaginal and rectal collection
- LIM broth (has antibiotics) suppresses GN normal flora
- If screen/culture is positive, moms need to be treated w/ penicillin
Group B Strep
- Post partum infections
- Early onset disease of Group B
- Late onset disease of Group B
Early onset disease of Group B
- Baby is < 7 days old
- Results from vertical transmission (during delivery)
- High mortality
Late onset disease of Group B
- Baby is 1 week to 3 months old
- More than often from parents, caretakers, nosocomial infections
Group B
- Gram stain
- GP
- Tiny, round diplococci
Groups C, G strep
S. dysgalactiae
Groups C, G
- Infections
- Differentiation
May cause pharyngitis (not usually treated)
- Lower incidence of post streptococcal diseases
- Not differentiated unless found in blood or CSF (reported as beta streptococci not Group A, B, or D)
S. pneumoniae
- Clinical infections
- Community acquired bacterial cause of pneumonia
- Meningitis, otitis media (ear infection)
- Carriers asymptomatic (esp in young children)
S. pneumoniae
- Treatment and prevention
- Becoming more resistant to antimicrobials
- Vaccinations available for young and older
S. pneumoniae
- Gram stain
- Colonial morphology
- Growth requirement
- GP diplococci (football, lancet shaped) or chains
- Mucoid (encapsulated) or dipped (autolysis) → virulence, typing
- Capnophilic
Viridans Streptococci
- 5 major groups (each w/ multiple species)
- S. salivarius group
- S. anginosus group
- S. mitis group
- S. mutans group
- S. bovis group
Viridans strep
- Causes…
- Subacute endocarditis
- Oral infections (gingivitis and cavities)
Which of the 5 major Viridans strep groups has the D Ag?
S. bovis
Viridans strep
- Hemolysis
- LAP pos/neg
- Bile esculin pos/neg
- NaCl pos/neg
- Optochin pos/neg
- Alpha/gamma hemolytic (less commonly beta hemolytic)
- Not usually further identified unless from blood or CSF cultures
- All are LAP +
- Bile esculin neg (except for S. bovis)
- NaCl neg
- Optochin neg
- Reported as either: alpha Streptococci (Gp D) or (not Gp D)
Group D Strep
- Normal flora
- Causes…
- Gastrointestinal flora
- Septicemia (positive blood cultures)
Viridans Strep
- Normal flora
Oral, GI, skin
Enterococcus sp
- Normal flora
- Infections
- Most common species
- Gastrointestinal
- Mainly UTI, septicemia, abdominal wounds
- E. faecalis (more common), E. faecium (more resistant)
Enterococcus sp
- Gram stain
- Drug resistance to…
- GPC, often elongated
- Multiple drug resistance (VRE → vancomycin drug resistance)
Abiotrophia
- Found in ____ and ____
- Culture ____ endocarditis
- Media
- Bacteremia; endocarditis
- Negative
- Chocolate agar or S. aureus satellitism
Aerococcus sp
- Gram stain
- Culture morphology
- Lap pos/neg
- GPC tetrads or clusters (like Staph)
- Alpha/gamma hemolysis (like Strep)
- Lap neg
Vancomycin Resistant “Lactic Acid Bacteria”
- 2 species
- produces which CHO?
- Similar in appearance to ____
- Leuconostoc species, Pediococcus species
- Produces only lactic acid from glucose fermentation (as do Strep)
- Similar in appearance to “viridans Streptococci”
