BACTE LEC - Strep pdf Flashcards by Carmina Mislang

– they grow in the
presence of oxygen but cannot use oxygen for
respiration

Aerotolerant anaerobe

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types of strep based on respiration (???)

Facultative anaerobe
• Aerotolerant anaerobe
• capnophilic

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taxo A positive /

bacitracin(S)

group A strep

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complications of group A [2]

Complications:

rheumatic fever
AGN

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Infections of group A [3, PPT]

Infections:

pharyngitis / strep throat
pyodermal infections
toxic shock syndrome

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Test: detects activity
of L-pyrrolidonyl arylamidase or
pyrrolidonyl aminopeptidase

PYR

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Meaning of PYR

(Pyrrolidonyl-anaphthylamide

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group A strep antigenic structure
attached to the peptidoglycan of the cell wall and
extends to the cell surface
– essential for virulence

M protein

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– Best defined virulence factor of group A strep
– Resists phagocytosis
– Adherence of bacterial cell to mucosal cells

M protein

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Both are adhesion molecules that mediate

adherence to host epithelial cells. [group A[

Fibronectin-binding protein (protein F)

• Lipoteichoic acid

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– 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

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– hemolysis incubated anerobically;
oxygen labile; lyzes blood cells; highly
immunogenic, ASO test

SLO

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– hemolysis incubated aerobically; oxygen

stable; lyzes WBC, nonimmunogenic

• SLS

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Most common DNase [grp A]

DNase A,B

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Pyodermal Infections of gp A[CISE]

–

Impetigo, Erysipelas, Cellulitis, scarlet fever

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• Activates plasmin, turning itself into a tissue

degrader

Impetigo Caused by Streptococcus

pyogenes

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beta hemolytic (small zone)
taxo A (-)
CAMP test (+) / Hippurate hydrolysis(+)

Group B

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Group B Virulence Factor
– prevents phagocytosis; ineffective
after opsonization; with sialic acid w/c inhibits
activation of the alternative pathway

• Capsule

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Group B Virulence Factor
– most significant component of the
capsule; critical virulence determinant

• Sialic acid

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Group B - No role in virulence [5]

Hemolysin
CAMP factor
Dnase
Hyaluronidase
protease

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Group B – Clinical Infections [2]

pneumonia or meningitis with bacetermia

• Mastitis in cattle

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Small-colony-forming-

S. anginosus (Viridans)

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Large-colony-forming (w/ Group A) –

pyogenic
streptococci
– S. dysgalactiae subsp. equisimilis – upper
respiratory tract, vagina, skin, spectrum of
infections – like Group A

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nonenterococcus

• Opportunistic infections

Group D Streptococcus

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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

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

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