BACTE LEC - Strep pdf Flashcards
– they grow in the
presence of oxygen but cannot use oxygen for
respiration
Aerotolerant anaerobe
types of strep based on respiration (???)
Facultative anaerobe
• Aerotolerant anaerobe
• capnophilic
taxo A positive /
bacitracin(S)
group A strep
complications of group A [2]
Complications:
- rheumatic fever
- AGN
Infections of group A [3, PPT]
Infections:
- pharyngitis / strep throat
- pyodermal infections
- toxic shock syndrome
Test: detects activity
of L-pyrrolidonyl arylamidase or
pyrrolidonyl aminopeptidase
PYR
Meaning of PYR
(Pyrrolidonyl-anaphthylamide
group A strep antigenic structure
attached to the peptidoglycan of the cell wall and
extends to the cell surface
– essential for virulence
M protein
– Best defined virulence factor of group A strep
– Resists phagocytosis
– Adherence of bacterial cell to mucosal cells
M protein
Both are adhesion molecules that mediate
adherence to host epithelial cells. [group A[
Fibronectin-binding protein (protein F)
• Lipoteichoic acid
– Group A VF weakly
immunogenic; prevents opsonized
phagocytosis by neutrophils or macrophages;
allows bacterium to mask its antigens and
remain unrecognized by its host
Hyaluronic acid capsule
– hemolysis incubated anerobically;
oxygen labile; lyzes blood cells; highly
immunogenic, ASO test
SLO
– hemolysis incubated aerobically; oxygen
stable; lyzes WBC, nonimmunogenic
• SLS
Most common DNase [grp A]
DNase A,B
Pyodermal Infections of gp A[CISE]
–
Impetigo, Erysipelas, Cellulitis, scarlet fever
• Activates plasmin, turning itself into a tissue
degrader
Impetigo Caused by Streptococcus
pyogenes
- beta hemolytic (small zone)
- taxo A (-)
- CAMP test (+) / Hippurate hydrolysis(+)
Group B
Group B Virulence Factor
– prevents phagocytosis; ineffective
after opsonization; with sialic acid w/c inhibits
activation of the alternative pathway
• Capsule
Group B Virulence Factor
– most significant component of the
capsule; critical virulence determinant
• Sialic acid
Group B - No role in virulence [5]
- Hemolysin
- CAMP factor
- Dnase
- Hyaluronidase
- protease
Group B – Clinical Infections [2]
- pneumonia or meningitis with bacetermia
• Mastitis in cattle
Small-colony-forming-
S. anginosus (Viridans)
Large-colony-forming (w/ Group A) –
pyogenic
streptococci
– S. dysgalactiae subsp. equisimilis – upper
respiratory tract, vagina, skin, spectrum of
infections – like Group A
nonenterococcus
• Opportunistic infections
Group D Streptococcus
Species of Group D Streptococcus
– S. equinus
– S. bovis
Lab ID:
- Alpha or nonhemolytic
- PYR (-)
- psuedocatalase
- Bile esculin(+)
- 6.5% NaCl (-)
Group D Streptococcus
- Group D antigen
* Same infections as group D Strep
Enterococcus spp.
Lab ID Varied hemolysis - produce acid in CHO broth - Arginine hydrolysis - Tolerate 0.04 % tellurite (E. faecalis) - Utilize pyruvate - Produce acid from methyl-a-D-glucopyranoside (MGP) - Growth around 100 ug efrotomycin disk - motile - PYR (+) - Bile esculin(+) - 6.5% NaCl(+), 45 degrees C, alkaline pH
Enterococcus spp.
1 cause of bacterial pneumonia - lobar
(especially in the elderly and in those with
underlying disease) sinusitis, otitis media (most
common isolate in
s. pneumoniae
lab ID
- alpha hemolytic, CAP, brain-heart infusion agar,
trypticase soy agar with 5% sheep RBC;
s. pneumoniae
lab ID
dome shaped if young; coin with raised rim if old
s. pneumoniae
gram variable as culture ages
- gram (+) diplococci; lancet shape
- taxo P(+) / Optochin susceptible
- Bile solubility(+)
- Capsular Swelling(+)
s. pneumoniae
No Lancefield group antigens
• green – alpha hemolytic
• fastidious, some require CO2
• oropharyngeal commensals - oppportunistic
Viridans
5 groups under Viridans
S. mitis group • S. mutans group • S. salivarius group • S. bovis • S. anginosus
– Infections:
• - oropharyngeal commensals - oppportunistic
- endocarditis with transient bacteremia
- meningitis
- dental caries
- osteomyelitis
Viridans Group
- most common cause of SBE
Viridans Group
PYR (-)
• LAP (+) leucine-B-naphthylamide, is hydrolyzed to
B-napthylamine + paradimethylaminocinnamaldehyde (DMACA) = red
• alpha or non-hemolytic
Viridans Group
• Ferments sugars, VP, B-D-glucuronidase acitivity,
hippurate hydrolysis – for species within the
viridans group
- taxo P (-)
- Bile esculin(-)
Viridans Group
biochem characteristics
• Throat swab
• Growth of most interfering respiratory
micobiota will be inhibited by SXT, but S.
pyogenes and S. agalactiae will grow. – may
have variable results – do PYR
Bacitracin susceptibility
biochem characteristics
• B-lysin producing strain of S. aureus
• Disk impregnated with the B-lysin
CAMP test
biochem characteristics
– a drop of
extracted B-lysin on a colony enhanced
hemolysis
Rapid CAMP test (spot CAMP)
biochem characteristics
• Hippuricase / hippurate hydrolase hydrolyzes
sodium hippurate to form sodium benzoate
and glycine
• Nihydrin
• Deep purple
Hippurate Hydrolysis
biochem characteristics
hydrolyzes sodium hippurate to form sodium benzoate
and glycine
Hippuricase / hippurate hydrolase
biochem characteristics
Detects activity of L-pyrrolidonyl arylamidase
or pyrrolidonyl aminopeptidase
• PYR impregnated disks serve as the substrate
to produce a-naphthylamine which is detected
in the presence of Ddimethylaminocinnamaldehyde (DMCA)
red
PYR Hydrolysis
biochem characteristics
• Hydrolyzes peptide bonds adjacent to a free
amino group
• The substrate, leucine-B-naphthylamide, is
hydrolyzed to B-napthylamine + paradimethylaminocinnamaldehyde (DMACA)
red
LAP
biochem characteristics
• Small colony forming B-hemolytic anginosus
group with groups A or C antigens vs. large
colony forming pyogenic strains with the same
antigens
• Detects acetoin production from glucose
• 5% a-naphthol + 40 % KOH; RT x 30 mins
red or pink color
VP
biochem characteristics
• Enzyme in large colony forming B-hemolytic
Groups C and G Strep
• (-) in small colony forming B-hemolytic
anginosus group
B-D-Glucoronidase
biochem characteristics
• cfb gene – encodes CAMP-factor protein
• ptsI (phosphotransferase) – Group A, C and G
can be distinguished
Nucleic Acid Probes
biochem characteristics
• Autocatalytic enzyme amidase
• Organism’s cell wall lyses during cell division
• Suspension in solution of Na deoxycholate
lyses solution becomes clear
Bile Solubility
biochem characteristics
• Incubate overnight at 35 degrees C in a CO2
incubator
• Zone of inhibition > 14 mm with a 6 mm disk
or >16 mm with a 10 mm disk
• Do bile solubility if zone is smaller
Optochin Susceptibility
biochem characteristics
• For non hemolytic, catalase (-), g(+) cocci
• 40 % bile; ability to hydrolyze esculin (for
Group D and Enterococcus)
• Enterococcus and Aerococcus grow in 6.5%
NaCl broth
Bile Esculin and Salt Tolerance
A-naphthylamine detected in the lresence of
Dimethylcinnamaldehyde
DMCA meaning
Dimethylcinnamaldehyde
Uncommon human pathogens
Group C and G strep
VF of e faecalis
Extracellularw serine protease
Gelatinase
VF of e faecalis which contribute to colonization and adherence to heart valves
Extracellularw serine protease
Gelatinase
Enterococcus with cytolysin
E faecalis
SBE meaning
Subacute bacterial endocarditis
Chemical reaction of s pneumoniae
CRP + C substance = ppt
Treatment for strep pneumoniae
Penicillin
Treatment for strep pneumoniae if penicillin resistant
Erythromycin and chloramphenicol
Strep with antigen c similar to c carbohydrate of lancefield grouping
S pneumoniae
How manu serotypes are there for strep pneumoniae based on capsular antigens
82
Sterile pleural effusion
Empyema
Opportunistic, oropharyngeal commensals
Viridans
CM for strep pneumoniae
CAP
BHI
TSA with 5% sheep RBC
Colonial characteristic of spneumon if young
Dome shaped
Colonial characteristic of spneumon if old
Coin with raised rim
Lancet shape strep
Pneumoniar
Group of strep
Fastidious
Some require CO2
Viridans
DMACA
Dimethylaminocinnamaldehyde
5 classif schemes [HPCBS]
Hemolytic pattern on BAP Physiologic characteristics Serologic grouping [lancefield] Capsular polysaccharide Biochemical characteristics
Meaning of LAP
Leucine Aminopeptidase
Motility of strep
Nonmotile
Motility of enterococcus
Motile
C carbohydrate present in all except
Viridans group
Lancefield classif based on
Cell wall structure
AGN meaning
Acute glomerular nephritis
Large colony isolates
S. dysgalactiae subspecies equisimilis
VP detects —
Acetoin
