MIDTERM: Streptococcus & Enterococcus Flashcards
Upper respiratory tract and skin lesions
S. pyogenes
Upper respiratory microbiota
S. pneumoniae
Streptococcus is differentiated from micrococcaeceae through?
Catalase Test
The most clinically important Lancefield group A
Group A S. pyogenes
One of the most aggressive pathogens encountered in clinical microbiology laboratories
Group A S. pyogenes
An oxygen-stable, nonimmunogenic hemolysin capable of lysing erythrocytes, leukocytes, and platelets in the
presence of room air. (20-22C)
Streptolysin S
Permits the bacterial adherence to the respiratory epithelium
Lipotechoic acid
Immunogenic, capable of lysing the same cells and cultured cells, is broken down by oxygen, and will produce hemolysis only in the absence of room air.
Streptolysin O
This is inhibited by the cholesterol in skin lipids, resulting in the absence of the development of protective antibodies associated with skin infection
Streptolysin O
Prone to progression with involvement of deeper tissues and organs, a characteristic that has earned the designation in general publications as the “flesh-eating bacteria.”
S. pyogenes
These are erythrogenic toxins produced by lysogenic strains. They are heat labile and rarely found in group C and
G streptococci.
Streptococcal Pyrogenic Exotoxins (SPEs)
When these organisms gain access to normally sterile sites they can cause life-threatening infections.
S. pyogenes and S. pneumoniae
Lancefield group:
Group B
S. agalactiae
Lancefield group:
Group C
S. dysgalactiae
Lancefield group:
Group D
Enterococcus spp. & Streptococcus bovis complex
These are responsible for the beta hemolytic pattern on blood agar plates which is used as a guide to identify this species
Streptolysin O and S
This is may be released and produce scarlet fever, which occurs in association with streptococcal pharyngitis and is manifested by a rash of the face and upper trunk.
Streptococcal Pyrogenic Exotoxins (SPEs)
Act as superantigens activating macrophages and T-helper cells and inducing the release of powerful immune
mediators
Streptococcal Pyrogenic Exotoxins (SPEs)
What are the powerful immune
mediators induced by SPEs
- interleukin (IL)-1, IL-2, IL-6
- tumor necrosis factor (TNF)-alpha
- TNF-beta
- interferons
- Cytokine
Similar to Staphylococcus toxic shock syndrome except that it’s not from tampons but rather it’s from streptococcal infection, usually through the mouth
Streptococcal toxic shock syndrome
This is typified by multi system involvement including renal and respiratory failure, rash, and diarrhea, is a serious disease mediated by production of potent SPE
Streptococcal toxic shock syndrome
The most important virulence factor of Streptococcus pyogenes
anti-phagocytic cell wall- M protein antibodies
_______ protein is associated with rheumatic fever, and ________ is typically associated with glomerulonephritis
Class 1M and class I or II, respectively
Manifested by fever, endocarditis (inflammation of heart muscle), subcutaneous nodules, and polyarthritis
Rheumatic fever
Characterized by edema, hypertension, hematuria, and proteinuria
Acute Glomerulonephritis
This usually follows respiratory tract infections and is believed to be mediated by antibodies produced against S. pyogenes M protein that cross-react with human heart tissue.
Rheumatic fever
Follow respiratory or cutaneous infections and is mediated by antigen-antibody complexes that deposit in glomeruli, where they initiate damage.
Acute Glomerulonephritis
Promotes fibrinolytic activity by converting plasminogen to plasmin
Streptokinase
This elaborates about 20 extracellular products, including enzymes (streptolysins, hyaluronidase, streptokinase, deoxyribonucleases {DNases}, and nicotamide adenine dinucleotidase {NADase} and pyrogenic (erythrogenic toxins)
S. pyogenes
Enhance the spread of the organism through connective
tissues which breakdowns the connective tissue in order to penetrate the deeper tissues
Hyaluronidase
Their pathogenic significance is unknown
DNase and NADase
These are produced by isolates of Streptococcus pyogenes that was infected with a specific temperate bacteriophage
pyrogenic and erythrogenic toxins (has serotypes A, B, and C)
In order to produce pyrogenic toxin they must be infected first by?
temperate bacteriophage (similar to cranial
bacterium)
Infections usually are associated with neonates and are acquired before or during the birthing process
Group B S. agalactiae
Group B S. agalactiae is known to cause what diseases in newborns?
- septicemia
- pneumonia
- meningitis
As per CDC, all pregnant women at ________ of
gestation should have vaginal or rectal specimens collected
and processed for detection of GBS
36 to 37 weeks
In this patient population, GBS infection manifests itself as skin and softmtissue infections, intraabdominal abscess, bacteremia, or pneumonia
elderly person with a serious underlying disease or immunodeficiency
What are the two pneumococcal vaccines currently available?
- 13-valent Conjugated pneumococcal vaccine (PCV13)
- 23-valent pneumococcal polysaccharide vaccine (PPSV23)
Streptococcus pneumoniae is seen in the normal flora of the upper respiratory tract about:
- 25% to 50% of preschool children
- 36% of primary school age children and
- nearly 20% of adults (carriers of streptococcus pneumonia)
Pneumococcal vaccine used for infants (2 months of age) and children
13-valent
Conjugated vaccine or PCV13
Pneumococcal vaccine used for adults especially 65 years older
23-valent pneumococcal polysaccharide vaccine or PPSV23
Pneumococcal vaccine used for immunosuppressed
individuals
Both PCV13 and PPSV23
A viridans streptococci, bacteremia has been associated with malignancies of the gastrointestinal tract
S. bovis
The main virulence factor of Streptococcus pneumoniae
Streptococcus anti-phagocytic polysaccharide capsule
It evades phagocytosis and is capable of mobilizing inflammatory cells mediated by its cell wall structure, including peptidoglycan, teichoic acids, and a pneumolysin
S. pneumoniae
Activates the classic complement pathway. The
pneumolysin mediates suppression of the oxidative
burst in phagocytes, providing for effective
evasion of immune clearance.
Pneumolysin
A viridans streptococci isolated from the oral cavity and blood
S. salivarius
A viridans streptococci. Etiologic agent of dental carries
S. mutans
Found within the cell wall, which binds receptors
for platelet-activating factor in endothelial cells,
leukocytes, platelets, and tissue cells of the lungs
and meninges providing for entry and spread of
the organism.
Phosphorylcholine
Formerly milleri group. Most common viridans streptococci responsible for liver, spleen, and brain abscesses.
S. anginosus
One of the subtypes of S. bovis and is isolated from blood cultures of patients with colonic cancer
Streptococcus
gallolyticus subsp. gallolyticus
A viridans streptococci that is commonly associated with endocarditis
S. mitis
These are not highly invasive; however, they enter tissue during dental or surgical procedures, which could lead to tooth abscesses, abdominal infections, bacteremia, or valve endocarditis and late-onset prosthetic
valve endocarditis
Viridan streptococci
Organisms in the _________ typically demonstrate no hemolysis or alpha-hemolysis (greening) on sheep blood agar and smell like butterscotch, especially from _______.
streptococcus viridan group and S. anginosus, respectively
This includes a large and complex group of human streptococci that are not groupable by Lancefield serology
viridans group
Presents as small colony-forming beta-hemolytic strains
with groups A, C, F, and G antigens.
S. anginosus group
The viridian streptococci that can produce beta hemolysis
S. anginosus group
Common cause of urinary tract infection in
hospitalized persons
Enterococcus
This genus is the first clinically relevant group of gram-positive cocci to acquire and disseminate resistance to vancomycin, thus the name vancomycin-resistant Enterococcus (VRE)
Enterococcus
They are not known to secrete toxins; however, they’re resistant to multiple antibiotics. Causing them to survive and proliferate, especially in patients receiving multiple antimicrobials, causing superinfection.
Enterococcus
Enterococcus are especially resistant to all currently available?
cephalosporins and aminoglycosides
Unidentified Enterococci
- Vagococcus fluvialis
- Lactococcus garvieae
- Lactococcus lactis
These are susceptible to vancomycin and fail to form gas in Mann, Rogoša, and Sharpe (MRS) broth
lactococci and vagococci
Are sometimes misidentified as enterococci, often called unidentified enterococci.
- Vagococcus fluvialis
- Lactococcus garvieae
- Lactococcus lactis
To differentiate the two Vagococcus is ______ but Lactococcus is ______
motile and nonmotile, respectively
These commercial kits have been reported to be very specific, but false negative results may occur if specimens contain low numbers of S. pyogenes
Antigen Detection
In two throat swabs, If the first swab yields a positive result by a direct antigen method, the second swab can be?
discarded
In two throat swabs, if those specimens in which the rapid antigen test yielded a negative result, what is the next step?
You inoculate the second swab on a blood agar plate or selective streptococcal blood agar plate
This is used to increase recovery for diagnosing streptococcal pharyngitis
two-plate culture method
What culture medias are recommended to be used for two-plate culture method
sheep blood agar and trimethoprim-sulfamethoxazole (SXT) blood agar
Serologic tests to detect a Streptolysin O and DNase B antibodies in acute and convalescent serum samples are used primarily to diagnose?
Acute rheumatic fever and Acute glomerulonephritis following infection with GAS
In terms of cultivation, Streptococci grow well in?
blood or chocolate agar
This agar is preferred because it is a differential media that can present the hemolytic properties of the organism unlike chocolate agar
Blood agar plate
These will not grow on blood or chocolate agars unless pyridoxal (vitamin B6 ) is supplied either by placement of a pyridoxal disk, by cross streaking with Staphylococcus, or by inoculation of vitamin B6 – supplemented culture media.
Abiotrophia and Granulicatella
These are nutrient variable pyridoxal- dependent streptococcus
- Streptococcus mitior
- Abiotrophia or
- Granulicatella bacteremia
For isolating group A streptococci from throat swabs, what is the most common medium used? and what is it supplemented with to suppress the growth of normal microbiota?
5% sheep blood agar supplemented with trimethoprimsulfamethoxazole
(SXT)
To detect genital carriage of group B streptococci during pregnancy, a vaginal or rectal swab is inoculated into?
ToddHewitt broth, such as LIM
Contain antimicrobials (gentamicin, nalidixic acid, or colistin and nalidixic acid), which suppresses the growth of normal vaginal microbiota and allows growth of group B S. agalactiae (GBS).
Todd-Hewitt broths
When LIM broth is subculture to this medium Strep B would produce a mauve color
CHROMagar
Urine can also be used for Group B Strep infection but it must have _______in a pregnant female to be use as a marker for the possibility of GBS by vaginal carriage
> 10^4 CFU/ml
A selective differential medium based on the esculin hydrolysis and is also selective by incorporation of inhibitory oxgall (bile salts) to inhibit the growth of other gram-positive organisms
Enterococcosel agar
These are used for a primary screening to detect vancomycin-resistant enterococci
Bile esculin agar and enterococcosel agar with vancomycin
Used to detect GBS directly in vaginal rectal specimen or can be used to detect GBS in LIM or Carrot broth culture
Nucleic Acid Amplification test
In this chromogenic broth media, colonies of beta hemolytic Group B Strep will convert the color of the tube from clear to yellow or orange
Carrot broth media
These Lancefield group would not change the tube color of Carrot broth media and when used a negative broth, they would still need to be planted into a solid media for the recovery of their strains.
nonhemolytic GBS
A selective nonchromogenic enrichment broth
can be subcultured unto the ________ in which colonies
of GBS appear yellow to orange for detection.
Granada agar
Laboratories typically incubate blood or chocolate agar plates in
5% to 10% carbon dioxide
A disk (Taxo A) is impregnated with a small amount of bacitracin (0.04 units) is placed on an agar plate.
Bacitracin Test
What are the positive and negative result for Bacitracin Test
Positive: Any zone of inhibition greater than10mm; susceptible
Negative: No zone of inhibition; resistant
What is the enzyme that hydrolyzes the l-pyrrolidonyl-b-naphthylamide substrate to produce a b-naphthylamine?
l-pyrrolidonyl arylamidase
Positive and negative results in L-Pyrrolidonyl arylamidase (PYR) test
Positive: Bright red (PINK) color within 5 minutes
Negative: No color change or an orange color
The reagent in L-Pyrrolidonyl arylamidase (PYR) test
N,N-methylamino-cinnamaldehyde
Beta hemolysis is enhanced by anaerobic conditions and because of ______________
Streptolysin O
This agar should be inoculated by stabbing the inoculating loop into the agar several times so that you would be able to observe sub surface hemolysis.
Blood agar plates (BAP)
Identify the test: Certain organisms (including group B streptococci)produce a diffusible extracellular hemolytic protein (CAMP factor) that acts synergistically with the beta-lysin of Staphylococcus aureus to cause enhanced lysis of red blood cells
Christie, Atkins, and Munch-Peterson(CAMP) test
In CAMP test, the ____________ are streaked perpendicular to a streak of __________on sheep blood agar
group B streptococci and S. aureus , respectively
Positive and negative results in CAMP test
Positive: Enhanced hemolysis is indicated by an arrowhead shaped zone of beta-hemolysis at the
juncture of the two organisms
Negative: No enhancement of hemolysis
These also produces a positive CAMP reaction.
Listeria monocytogenes
Positive and negative results in Hippurate Hydrolysis Test
Positive: deep blue/violet color in 30 minutes
Negative: Colorless or slightly yellow pink color
This is a glycine conjugate of benzoic acid and when hydrolysed by an organism
glycine and benzoic acid are formed
Hippurate
Limitations of Hippurate Hydrolysis Test
A false-positive result may occur if incubation with ninhydrin exceeds 30 minutes
Positive and negative results in Optochin test
Positive: Zone of inhibition at least 14 mm in diameter, with 6-mm disk
Negative: No zone of inhibition
Used to differentiate group B streptococci (Streptococcus agalactiae– positive) from other
streptococcal species
Christie, Atkins, and Munch-Peterson(CAMP) test
Other term for Optochin
ethylhydroxycupreine hydrochloride or P disk
An antibiotic that interferes with the ATPase and production of adenosine triphosphate(ATP) in microorganisms
Optochin
This lower the surface tension between the bacterial cell membrane and the medium, thus accelerating the organism’s natural autolytic process.
Bile salts
This rapidly lyses pneumococcal colonies. Lysis depends on the presence of an intracellular autolytic enzyme, amidase.
Bile or bile salt solution (sodium deoxycholate)
Positive and negative results in Bile solubility test
Positive: Suspension clears
Negative: Suspension remains turbid
Considered the gold standard technique for serotyping Streptococcus pneumoniae
Quellung test or Newfeld Reaction
A microscopic precipitin test that is used to identify pneumococci or to determine the capsular serotype of individual pneumococcal isolates
Quellung test or Newfeld Reaction
Counterstain used in Quellung test that stain the pneumococcal cells dark blue
Methylene Blue
If the organism is susceptible to optochin it is presumed that this organism is?
Streptococcus pneumoniae
This test differentiates Streptococcus pneumoniae (positive; soluble) from alpha-hemolytic streptococci (negative; insoluble
Bile solubility test
This test is used to detect the capsule of pneumococcus
Quellung reaction
Positive Quellung reaction
Single cells, pair, chains, and clumps of cells
This test is used to determine the ability of an organism to grow in high concentrations of salt. It is used to differentiate enterococci (positive) from nonenterococci (negative).
Salt tolerance test
What is the test medium used in Salt tolerance test?
heart infusion broth containing 6.5% NaCl
Indicator for acid production in Salt tolerance test
small amount of glucose and bromocresol purple
This test is used for the presumptive identification of enterococci and organisms in the Streptococcus bovis group. The test differentiates enterococci and group D streptococci from non–group D viridans streptococci
Bile Esculin Test
Positive and negative results in Bile Esculin Test
Positive: Growth and blackening of the agar slant
Negative: Growth and no blackening of medium
Identify:
- Susceptible to bacithracin
- Beta-hemolytic
- PYR positive
Group A (S. pyogenes)
Identify:
- Susceptibility to optochin
- Positive for bile solubility
- Alpha hemolytic
- Colonies are mucoid of flattened with a depressed center
- Quellung test
S.pneumoniae
Identify:
- Alpha hemolytic streptococci that are optochin resistant and PYRase negative
- Gamma hemolytic streptococci that are PYRase negative and do not grow in 6.5% NaCl
Viridans
Identify:
- PYRase positive
- Grow in the presence of 6.5% NaCl
- Bile esculin hydrolysis positive
Enterococcus
Identify:
- Beta-hemolytic
- Hippurate hydrolysis positive
- Positive CAMP test
Group B (S. agalactiae)
These resemble viridans streptococci on culture but are microscopically similar to staphylococci in that they occur as tetrads or clusters.
Aerococci
These organisms sometimes show a weak catalase or pseudo catalase reaction. They grow in the presence of 6.5% NaCl and can easily be confused with enterococci
Aerococci
Their susceptibility pattern can also resemble that of the enterococci. Some strains of these organisms are bile esculin positive and PYR positive.
Aerococci
Enumerate the streptococcus groups that are susceptible to penicillin
Groups A, B, C, and G streptococcus
In cases of penicillin allergy, what other tests must be performed?
macrolides, clindamycin, and the tetracyclines
Test performed if erythromycin resistant
a D zone test
Clindamycin and erythromycin disks be separated by _________ instead of the 15 to 16mm recommended for testing S. aureus
12 mm
These are Plasmid-borne
van genes
Confers high level resistance and predominance to E. faecium and less frequently to E.faecalis
vanA, vanB
Intrinsic and lower-level in resistance in yellow, motile Enterococcus
vanC
