BACTERIOLOGY LEC - MIDTERMS: L2 - STREPTOCOCCI Flashcards
3 genera of family Streptococcaceae Bergey’s Manual of Determinative Bacteriology)
- Streptococcus
- Enterococcus (Note: previously from genus streptococcus)
- Lactococcus
T OR F
Streptococcaceae are gram positive cocci, and catalase positive, making them differ from Staph
False
Staph - catalase positive
Strep - catalase negative
T or F
Streptococcaceae are fastidious, facultative aerobes and needs 5-10% CO2 for growth
False
- Strep areFacultative anaerobes
MOTF
Patterns of Hemolysis
1. Beta hemolytic - complete hemolysis of RBC, clear or colorless zone
EX: S. pyogenes, S. agalactiae
- Gamma hemolytic - non-hemolytic, Enterococcus spp.
- Alpha hemolytic - incomplete or partial hemolysis of RBC, green discoloration
Ex: S. pneumoniae, S. viridans
ALL TRUE
MOTF
Physiological Division
- Viridans division - salt tolerant, grow at high pH, and Temp range of 10°C to 45°C.
- Pyogenic division - includes beta hemolytic strains (A,B,C,D,E,F,&G)
- Streptococcal organisms that are able to create diseases or infections associated with pus formation - Enterococcus division - not beta hemolytic, not salt tolerant, and grow at high pH.
- Lactic division - not clinically significant & associated with dairy industry
2,4 - TRUE
1,3 - FALSE
- Viridans division - not beta hemolytic, not salt tolerant, and grow at high pH.
- Enterococcus division - salt tolerant, grow at high pH, and Temp range of 10°C to 45°C.
MOTF
Lancefield Grouping
By Rebecca Lancefield 1993
- Divides the Streptococci into serologic groups - Based on antigenic properties of carbohydrate group antigens in their cell wall
- ABCDFG - clinically significant
- Mostly associated with human infection.
- ABCDE were the first five and cuurrently at almost 20 groups (A-H)(K-T)
All true
Beta Hemolytic Streptococcus
Enumerate all
Lancefield group A - S. pyogenes
Lancefield group B
- S. agalactiae
Lancefield group C & G - S. dysgalactiae &S. Equi
Lancefield group A, C, F & G - S. anginosus
MOTF
Group A: Streptococcus pyogenes (GAS)
- Normal flora
- Most virulent for humans
- Acquired only thru direct contact - person to person contact
1,3 - false
2 - true
1 - not normal flora
3 - also by inhalation of aerosol droplets
Cell surface antigens of GAS
- This structure is antiphagocytic; it prevents organisms from being phagocytized.
- Reason for mucoid colonies
Hyaluronic acid Capsule
Cell surface antigens of GAS
- Interferes with complement activity, Precipitates fibrinogen, Clumps platelet and wbc, Inhibits migration of WBC
- Can differentiate S pyogenes
M protein (about 80 types)
Group-specific cell wall antigen of GAS
Grp.A sugar: rhamnose-N-acetylglucosamine
Allow them to act like immune cells and attach to fc portion of IgG and IgA
IgG & IgA-binding proteins
- Cleaves C5a component of complement
- Inhibits neutrophil chemotaxis in vitro
C5a protease
(C5a - important anaphylatoxin, will attach to mast cells and basophils - initiating release of histamine and start inflammatory reaction)
MOTF
- F protein - allows binding to fibronectin in pharyngeal epithelium
- Lipoteichoic acid: - attached to M protein
- may allow binding to fibronectin
BOTH T
Fibronectin - binding sites for organism on membranes on host cells or structures.
MOTF
1. Streptokinase - fibrinolysin that lyses blood clots (just like staphylokinase)
- Hyaluronidase - hydrolyze or breakdown hyaluronic acid which is part of the connective tissue, important in spreading the infection
- Diphosphopyridine nucleotidase - degrades host DNA & RNA
- Streptodornase - Associated with the organism’s ability to
destroy WBCs
1,2 - true
3,4 - false
- Streptodornase - degrades host DNA & RNA
- Diphosphopyridine nucleotidase - Associated with the organism’s ability to
destroy WBCs
- Responsible for the increase in temperature and rashes (specially in Scarlet fever)
- Cause of Streptococcal TSS
Pyrogenic exotoxins/ erythrogenic toxins (A, B, C)
Most potent: Exotoxin A
NOTE: Staph TSS is more fatal
MOTF
- Streptolysin O - antigenic, oxygen labile
- Streptolysin S - oxygen stable, non-antigenic but toxic (surface hemolysin)
Both true
MOTF
Erysipelas
1. St. Anthony’s fire
2. Has pus production, but exotoxin A production
(increase temperature in the area) & rashes
3. Itchiness and hotness
1,3 - true
2 - false, has no pus production
- Inflammation of deep tissues including the skin
- Common in middle aged individuals
Cellulitis
- Begins as fluid-filled blisters that usually erupts creating weeping lesions
- Common in children
Impetigo
Red, swollen tonsils
Strep throat
- Streptococcal pharyngitis
- Made streptococcus pyogenes earn the name of “flesh-eating bacteria”
- Active component: Exotoxin A
- Destruction of tissue a rate of 2 inches per hour
Necrotizing fasciitis
- Cause Hypotension, multi-organ failure, fever,
erythema, swelling, tachycardia, acute respiratory distress, renal impairment and shock - Toxin mediated
Streptococcal toxic shock syndrome
- May occur after streptococcal pharyngitis or other infection
- Strawberry tongue, rashes, fever
Scarlet fever
- Cardiac inflammation and scarring
- Acute stage consist of pancarditis (infected entire layer of heart)
- Autoimmune response
Rheumatic heart disease
Systemic disease that affects the connective tissue around the arterioles
Acute rheumatic fever
Triggers inflammation and proliferation of
glomerular tissue that can result in damage to
the basement membrane
Acute glomerulonephritis
MOTF
GAS
1. BAP: white to gray pinpoint colonies, translucent, opalescent.
2. Wide zone of B-hemolysis
3. Contaminated (throat): BAP with SXT
(trimethoprim/sulfamethoxazole)
4. Mucoid colonies may be produced especially strains that are positive for M protein
All are true
NOTE: M protein 49 - most virulent
Differentiate staphylococcus from streptococcus
Catalase test
Staph = positive Strep = negative
BAP WITH SXT = GAS are resistant or susceptible?
Resistant (R)
Taxo A/Bacitracin Disk test of GAS:
- 0.02 to 0.04 unit used (0.04 more common)
- Only Gas is susceptible for taxo A
- Zone of inhibition = Positive for GAS
PYR Test: Pyrrolidonyl arylamidase test for GAS
- Reagent used
Reagent: L-pyrrolidonyl-2-naphthylamide
L-pyrrolidonyl-2-naphthylamide is hydrolyzed by the enzyme
Pyrrolidonyl arylamidase (produced specifically by GAS)
Hydrolization of L-pyrrolidonyl-2-naphthylamide will release _______
B-naphthylamide
Color developer acted to B-naphthylamide
p-dimethylaminocinnamaldehyde (pink color)
Serological tests for GAS:
- ASO (anti-streptolysin O)
2. Sero typing of specific M CHON
MOTF
DICK TEST - for scarlet fever
1. 0.1ml toxin (test arm) & 0.1ml toxoid (control arm)
2. Positive: (+) redness in test arm (1 cm)
Both true
MOTF
SCHULTZ-CHARLTON TEST
1. Checks out the rashes whether it is caused by scarlet fever or not
2. Inject 0.1 mL of anti-toxin subcutaneously and fading of rashes after 6 to 8 hours means positive (there is scarlet fever)
Both true
NOTE: There is neutralization of erythrogenic toxin via the anti-toxin
MOTF
Group B: Streptococcus agalactiae (GBS)
1. Normal flora of the GIT & Vaginal tract
2. Bigger beta-hemolytic compared to GAS
3. Able to mimic host molecules via its Polysaccharide capsule
1,3 true
2 - false
2 - GAS has wider beta hemolysis
MOTF
GBS Pathogenesis
1. Mostly the infections are nosocomial and manifest in immunocompromised individuals
2. Can be through neonatal infection and Adult streptococcal infection
3. Neonatal infection: infection of amniotic fluid through placental membranes and passing through birth canal
All true
NOTE:
Nosocomial infection types:
- Early-onset - first week of life
- Late-onset - first week to about 3 months after birth
CAMP test meaning of acronym:
Christie, Atkins and Munch-Peterson
MOTF
CAMP TEST
1. In BAP, in the middle are the unknown and perpendicular to it are the SAU
2. Do not incubate anaerobically or with increase CO2 to prevent false reaction
3. Contains synergistic hemolysis of SAU and GAS
4. Positive result: arrowhead zone of hemolysis
1,3 - false
2,4 - true
1 - In bap: middle - sau, perpendicular - unknown
3 - Sau and GBS
SODIUM HIPPURATE HYDROLYSIS
Reagent used:
0.4 ml 1% Na hippurate
If GBS is present, it will hydrolyze sodium hippurate into ______
Benzoic
acid and glycine
MOTF
- Ferric chloride - detect benzoic acid producing purple color
- Ninhydrin - detect glycine
BOTH TRUE
NOTE: Purple color = positive for SHH > meaning GBS is present
Characteristics of Group C, F & G: Miscellaneous Beta Hemolytic Streptococcus
- beta-hemolytic streptococci
- Normal microbiota: skin, nasopharynx, GIT, GUT
- Contains Endogenous strain: gain access to the sterile site and
cause infections - Direct contact: person to person
Differentiate Group C F G (On a 5% SBA)
Group C - Grayish white, glistening; (F and G are matte)
Group F - has narrow to wide zone of B-hemolysis ( C and G are wide)
Group G - matte, wide zone
Enumerate Group C and G and Group F
Group C&G - S. equi subsp. zooepidemicus, - S. equi subsp. equi - S. dysgalactiae subsp. equisimilis, - S. dysgalactiae subsp. dysgalactiae - S. anginosus (They cause infection similar to Group A)
Group F
- S. anginosus
Group C, F & G: Identification
Test differentiate them from group B
CAMP and Hippurate
Group C, F & G: Identification
Test differentiate them from group A
PYR - Pyrrolidonyl arylamidase test
Group C, F & G: Identification
Test differentiate them from group D
Bile esculin
Group C, F & G: Identification
SXT: resistant or susceptible?
Susceptible (unlike A and B)
Group C, F & G: Identification
Vogues-Proskaur
S. dysgalactiae subsp. equisimilis = Vp (-)
S. anginosus (C,G,F) = Vp(+)
MOTF Streptococcus pneumoniae 1. Formerly Diplococcus pneumoniae 2. Beta-hemolytic 3. Capnophilic - 5-10% CO2 4. Encapsulated, facultative anaerobe, fastidious
1,3,4 - true
2 - false
2 - alpha-hemolytic
Major virulence factors of Streptococcus pneumoniae (Enumerate)
- CAPSULAR ANTIGENS: Resist phagocytosis and antigenic
- M-CHON
- PNEUMOLYSIN - released in cell lysin
- Autolysin - aids in the release of pneumolysin
Pathogenesis of Streptococcus pneumoniae
Respiratory Tract ➞ sinuses and middle ear ➞ sinusitis and otitis media
Streptococcus pneumoniae can cause what diseases:
- pneumonia, bacteremia, & meningitis
- community-acquired bacterial pneumonia; common in US
NOTE: Rusty sputum - sputum characteristic
MOTF
Streptococcus pneumoniae
1. Gram(+) lancet-shaped diplococci
2. Mucoid, dome shape, transparent colonies
Both true
Streptococcus pneumoniae colonies later develop a _____
appearance after 48 hours of incubation
crater-like
Streptococcus pneumoniae test - Optochin Test/ Taxo P
- Optochin (antibiotic) also known as
ethylhydrocupreine hydrochloride
Streptococcus pneumoniae test - Optochin Test/ Taxo P
- Sensitivity testing, inoculating the specimen using lawn technique
- Use of 5ug - Ethylhydrocupreine HCl
- POSITIVE: (+) ≥14 mm (susceptible for S. pneumoniae)
All true
S. pneumoniae are susceptible to Optochin test
T or F
Pneumococcus are bile soluble
True
Differentiates the Pneumococcus (bile soluble) from other alpha-hemolytic Streptococci (non bile soluble)
Bile Solubility Test:
Examples of bile salts used:
(Na deoxycholate; Na taurocholate)
Positive result of bile solubility test
POSITIVE: has autolysis (clear solution because it dissolves the bile)
- CLEAR SOLUTION = Presence of S. Pneumococcus
NEGATIVE: TURBID
Test of S. pneumococcus which makes use of an antisera and causes a change on the refractive index of the capsule, making it more swollen and visible
Quellung Test:
Quellung Test positive result:
Counterstain - methylene blue (usually)
Positive: swollen capsules, meaning it has ag-ab reaction
MOTF
- S. pneumococcus treatment: Penicillin, ceftriaxone/cefotaxime, Trimethoprim/sulfamethoxazole - tmp/smx (STX)
- S. pneumococcus is also susceptible to penicillin, macrolides, & cephalosporins
- Prevention: Pneumococcal conjugate vaccine
1,3 - true
2 - false, SP acquired resistant to penicillin, macrolides, & cephalosporins
T OR F Streptococcus bovis group 1. Group D non-enterococcus 2. Bile esculin + and PYR - 3. Unable to grow in 6.5% Nacl 4. Alpha, gamma hemolytic
True
Bacteremia caused by Streptococcus bovis has been associated with the presence of
Gastrointestinal tumors
Enumerate Streptococcus bovis group
S. bovis & S. equinus → single species
Others: S. gallolyticus, S. infantarius, S. alactolyticus
Enumerate Enterococcus group
E. faecalis - causes about 80-90% cases of human enterococcal infection; widely isolated
E. faecium, E. durans, E. avium, E. casseliflavus, E.
gallinarum, E. dispar, & E. canis
- Both Enterococcus and non-Enterococcus are positive for this test
- Differentiate Group D from other Streptococcal groups
BILE ESCULIN HYDROLYSIS
The differentiation is based on the Group D’s ability to ______
To grow in 40% bile and hydrolyze esculin producing the product esculetin
Esculetin reacts with ferric chloride produce
brown-black precipitate
Esculin is hydrolyzed to ____
Esculetin and dextrose
Differentiates Enterococcal and non- Enterococcal groups
5% SALT BROTH OR SALT TOLERANCE TEST
MOTF 5% SALT BROTH OR SALT TOLERANCE TEST 1. If growth is present in both broth (w/ salt & w/o salt), the organism is salt tolerant - true for Enterococcal group 2. Turbid = presence of enterococcus 3. Clear = non-enterococcus
All true
MOTF
1. Enterococcus has intrinsic resistance to beta-lactam antibiotics (penicillin, cephalosporins, and aminoglycosides)
2. Use of combination treatment : beta-lactam (penicillin or
vancomycin) with aminoglycosides
3. Vancomycin-resistant Enterococci (VRE) → first reported
in 1986
All true
NOTE: It is important to perform first sensitivity testing
Enumerate Viridans Group:
S. mutans S. salivarus S. mitis S. sanguinis S. constellatus S. intermedius
- Heterogenous group of Streptococcus. They do not have a Lancefield Antigen Classification
- Normal flora of the human oropharynx, GIT, and the female genital tract
Viridans Group
Diseases caused by Viridans group:
Subacute bacterial endocarditis - cause infection in people with damaged heart valves or those with prosthetic heart valves implanted in their endocardial surfaces
Bacteremia and Septicemia - Transiently enters the blood following dental or genitourinary procedures
Dental caries - Acids are the ones that destroy the enamel
Viridans group produce the enzyme ____ which can breakdown sucrose and binds to glucose to form complex polysaccharides like glucans and dextrans
Glucosyltransferase - Facilitates the attachment of Viridans groups such as S. mutans to tooth enamel, ferment sugar and release acid as by-product (destroy enamel)
Viridans group laboratory diagnosis:
- Resistant to bile (sodium deoxycholate), & optochin
- Negative to most presumptive tests for Streptococcus
- Positive to mannitol and sorbitol
- Positive to urease and VP (Vouges-Proskouer) reaction
NUTRITIONALLY VARIANT STREPTOCOCCI (NVS)
NVS - Appears to mimic the Viridans group
What is its main difference from the Viridans group
Requires cysteine or pyridoxal (Vitamin B6) for growth
NVS - Also known to grow well beside Staphylococcus aureus because it releases _____
pyridoxal
NVS - given the new genus
Abiotrophia and Granulicatella
Other Catalase (-) Streptococcal Like Organisms - commonly mistaken as Streptococci
- Aerococcus viridans = Rare cause of endocarditis and meningitis ICH
- Leuconostoc spp = Rarely isolated in clinical sites
-Pediococcus = NF of LGIT, isolated occasionally from
abscesses
-Lactococcus and Gemella = Very rare human pathogens
