MODULE 4 (UNIT 2) Flashcards
(113 cards)
1
Q
smith and brown’s classification is based on hemolysis on
A
5% sheep blood agar medium
2
Q
- incomplete lysis of erythrocytes
- reduction of hemoglobin
- formation of green pigment
- '’green streptococci’’
A
alpha hemolysis
3
Q
- complete disruption of erythrocytes
- results in clearing of blood around the bacterial growth
A
beta hemolysis
4
Q
- absence of hemolysis
- no change seen in the medium surrounding bacterial growth
- '’indifferent streptococci’’
A
Gama hemolysis
5
Q
- a small zone of intact erythrocytes immediately adjacent to bacterial colony
- surrounded with a zone of complete erythrocyte hemolysis
- confused with beta hemolysis
A
Alpha prime analysis
6
Q
- discovered by rebecca lancefield in the 1930s
- based on group specific antigens [stimulates the formation of antibodies with differing specificities]
A
Lancefield classification
7
Q
Group specific antigens which are cell wall polysaccharides or c substance
-typing with specific antiserum causing agglutination is generally done for these groups
A
A, B, C, F, G streptococci
8
Q
Group specific antigens which are lipotheichoic
A
Group D streptococci and Enterococcus species
9
Q
Classification based on temperature for growth particularly at 10 degrees to 45 degrees celsius
A
Academic or Bergey’s classification
10
Q
Consist of streptococci that do not grow at both 10 degrees and 45 degrees celsius
A
Pyogenic group
11
Q
Includes streptococci which still to grow at 10 degrees but can be recovered at temperatures up to 45 degrees celsius
A
Viridans group
12
Q
Streptococci that grow at both 10 degrees and 45 degrees celsius
A
Enterococcus group
13
Q
Consist of streptococci that are frequently recovered in dairy products and can grow at 10 degrees celsius but fail to grow at 45 degrees celsius
A
Lactic group
14
Q
S. Pyogenes
- lancefield classification
- hemolysis on ship BAM
- 10 degrees celsius
- 45 degrees celsius
A
- alpha
- beta
- negative
- negative
15
Q
S. Agalactiae
- lancefield classification
- hemolysis on ship BAM
- 10 degrees celsius
- 45 degrees celsius
A
- beta
- beta
- negative
- negative
16
Q
S. Pneumoniae
- lancefield classification
- hemolysis on ship BAM
- 10 degrees celsius
- 45 degrees celsius
A
- none
- alpha
- negative
- negative
17
Q
S. Mitis
S. Mutans
S. Salivarius
- lancefield classification
- hemolysis on ship BAM
- 10 degrees celsius
- 45 degrees celsius
A
- none
- alpha, gamma
- negative
- positive
18
Q
S. Anginosus
S. Intermedius
S. Constellatus
- lancefield classification
- hemolysis on ship BAM
- 10 degrees celsius
- 45 degrees celsius
A
- F (A, C, G) and untypeable
- alpha, beta, gamma
- negative
- positive
19
Q
S. Bovis/enquinus
-non enterococci
- lancefield classification
- hemolysis on ship BAM
- 10 degrees celsius
- 45 degrees celsius
A
- D
- gamma, occ. Alpha, rarely beta
- positive
- positive
20
Q
Group A - Beta hemolytic streptococci (GAS): Streptococcus pyogenes
- Habitat
- Transmission
A
- human throat and skin
2. respiratory droplets or contact with cutaneous lesions
21
Q
Group A - Beta hemolytic streptococci (GAS): Streptococcus pyogenes
PATHOGENESIS AND CLINICAL MANIFESTATIONS
- most common infection caused by S. pyogenes
- may occur at any age (5 to 15 yrs)
- acute sore throat, malaise, fever, and headache
- involves the tonsillar pillars, uvula, and soft palate, which become red, swollen, and covered with a yellow White exudate.
- the cervical lymph nodes that drain this area may also become swollen and tender
- In cellulitis, the lesion is not raised, and the line between the involved and uninvolved tissue is indistinct
A
Pharyngitis or streptococcal sore throat
22
Q
Group A - Beta hemolytic streptococci (GAS): Streptococcus pyogenes
PATHOGENESIS AND CLINICAL MANIFESTATIONS
- Consists of extensive and very rapidly spreading necrosis of the skin, tissues, and fascia.
- Organism enters at the site of localized trauma or previous surgery, or via hematogenous seeding of subcutaneous muscles and soft tissue.
- Affected tissues become gangrenous, with sloughing of devitalized tissues and extensive subcutaneous tissue necrosis.
- Group A streptococci that cause necrotizing fasciitis are termed “flesh-eating bacteria”.
- Bacteria other than S pyogenes can also cause necrotizing fasciitis
A
Necrotizing fasciitis (streptococcal gangrene)
23
Q
Group A - Beta hemolytic streptococci (GAS): Streptococcus pyogenes
PATHOGENESIS AND CLINICAL MANIFESTATIONS
- Occurs in women following child birth (either by vaginal or abdominal/C section) or abortion.
- Organisms colonizing the genital tract or from an obstetrical personnel invade the upper genital tract, causing endometritis, lymphangitis, bacteremia, necrotizing fasciitis, and streptococcal toxic shock syndrome.
- Intrapartum (occuring during pregnancy) transmission of group A streptococci, may lead to severe and often fatal group A streptococcal disease in the neonate.
- Manifestations in the neonate include septicemia, jaundice, and cellulitis, or stillbirth
A
Puerperal fever
24
Q
Group A - Beta hemolytic streptococci (GAS): Streptococcus pyogenes
PATHOGENESIS AND CLINICAL MANIFESTATIONS
- May result from streptococcal infection of traumatic or surgical wounds.
- Can be rapidly fatal.
- Can also occur with skin infections, such as cellulitis and rarely pharyngitis
A
Bacteremia or Sepsis
25
Group A - Beta hemolytic streptococci (GAS): Streptococcus pygogenes
PATHOGENESIS AND CLINICAL MANIFESTATIONS
Are non-suppurative sequelae that occur weeks after GAS infection in the throat and/or skin
Post Streptococcal Diseases
26
Group A - Beta hemolytic streptococci (GAS): Streptococcus pygoenes
PATHOGENESIS AND CLINICAL MANIFESTATIONS
- Inflammation of the glomeruli of the kidneys caused by the M strains of S. pygogenes (nephritogenic).
- Begins 1 to 4 weeks after streptococcal pharyngitis or 3 to 6 weeks after skin infection; primarily a disease of childhood.
- May be initiated by deposition and accumulation of antigen–antibody complexes on the glomerular basement membrane -Signs symptoms: dark, smoky urine (due to blood and proteins) edema, hypertension, and urea nitrogen retention. -Majority recover completely while some develop chronic glomerulonephritis with kidney failure, and a few die
Acute Glomerulonephritis (AGN)
27
Group A - Beta hemolytic streptococci (GAS): Streptococcus pygogenes
PATHOGENESIS AND CLINICAL MANIFESTATIONS
-Considered as the most serious sequela of S. pyogenes because it results in damage to heart muscle and valves.
-Occurs 1–4 weeks after S. pyogenes pharyngitis
- Is an autoimmune disease, i.e., antibodies formed against streptococcal antigens cross react with the molecules of the host that trigger inflammation and injury of tissues (of the heart, joints, CNS)
-Signs and symptoms: fever, malaise, arthritis, carditis, chorea (neurologic disorder characterized by involuntary jerky movements), and skin nodules
-Pathologic processes of S. pyogenes infection can extend to the heart. The cross-reaction between streptococcal-induced antibodies and heart proteins have a gradual destructive effect on atrioventricular valve. Scarring and deformation change the capacity of the valves to close and shine the blood properly leading to Rheumatic Heart Disease.
-Has a marked tendency to be reactivated by recurrent
streptococcal infections in contrast with nephritis.
-Occur more frequently in tropical countries and is the most important cause of heart disease in young people in developing countries.
Rheumatic fever (RF)
28
* Elaborated by lysogenic S. pyogenes that contain genes from temperate bacteriophage.
* Act as superantigens which stimulate monocytes and T cells. When activated, these cells proliferate and produce tumor necrosis factor, which in high quantities leads to damage of the plasma membrane of blood capillaries.
* Responsible for the manifestations of scarlet fever
Erythrogenic Toxin
29
is a skin test for scarlet fever that uses antitoxin to the erythrogenic toxin of Streptococcus pyogenes subcutaneously: a positive reaction is blanching of the rash in the area around the injection site.
Schultz-Charlton Test
30
is a skin test performed to determine an individual’s susceptibility to scarlet fever. It consists of intradermal injection of diluted scarlet fever toxin on the arm of a suspected patient. Development of a red rash with a diameter of 10 mm or greater indicates lack of immunity to the disease
Dick Test
31
•S. pyogenes elaborates two hemolytic exotoxins, proteins that not only lyse the membranes of erythrocytes but also damage a variety of other cell types
Streptolysins
32
• The “O” refers to this hemolysin being oxygen labile. It is active only in the reduced form.
•Is responsible for hemolysis on sheep blood agar (SBA) plates incubated anaerobically or subsurface hemolysis when growth occurs in cuts
(stabs) made deep into the blood agar plates
•It lyses a variety of host cells including leukocytes, platelets, as well as
RBCs.
•It is highly immunogenic, and infected individuals readily form antibodies against it known as anti-streptolysin O (ASO) which blocks hemolysis caused by streptolysin O.
•ASO combines quantitatively with streptolysin O and is measured in the Anti-streptolysin O Test
Streptolysin O (SLO)
33
Which virulence factor is a major virulence factor of S. pyogenes (those that lack M protein are not virulent)
M Protein
34
M protein is found on the bacterial cell surface associated with
fimbriae
35
There are more than 200 types of S. pyogenes M proteins;
1. immunity to infection with GAS is related to the production or presence of (1) against M protein;
2. subsequent infections may occur with different (2)
1. type specific antibodies
| 2. M serotypes
36
M protein inhibits activation of the
complement pathway
37
A cutaway view of group A Streptococcus
The (1) consists of fimbriae composed in part of M-protein, group specific substance.
Other layers making up the cell envelope are the (2), (3),(4)
1. outermost fringe
| 2. capsule, protein antigens, and C-carbohydrate antigens
38
* A polysaccharide capsule, which is composed of hyaluronic acid
* Prevents opsonized phagocytosis by neutrophils or macrophages.
* Is non-immunogenic; it is chemically similar with the hyaluronic acid in the host's connective tissue ground substance
* Allows the bacterium to mask its antigens and remain unrecognized by its host’s immune system
Capsule
39
* Formerly called streptococcal pyrogenic exotoxins (Spe)
* There are four antigenically distinct streptococcal pyrogenic exotoxins — SpeA, SpeB, SpeC, and SpeF.
* SpeA has been most widely studied
Erythrogenic Toxin
40
is a test performed to determine whether an individual has had a recent infection with S. pyogenes.
Anti-Streptolysin O Test (ASTO or ASOT)
41
Anti-Streptolysin O Test (ASTO or ASOT)
* It involves detection and quantitation of (1) in the serum
* An abnormally high serum titer suggests either (2a) with S. pyogenes or persistently high antibody levels caused by an (2) to an earlier exposure in a hypersensitive person.
* ASTO is also related to the retro-diagnosis of (3) (to check whether rheumatic fever is caused by a previous streptococcal infection or by other etiologies)
1. Anti-Streptolysin O antibodies
2. recent infection; exaggerated immune response
3. rheumatic fever
42
* Is responsible for hemolysis seen around colonies (surface hemolysis) incubated aerobically
* It is oxygen stable, lyses leukocytes, and is non-immunogenic — does not stimulate antibody production in the host
Streptolysin S (SLS)
43
STREPTOKINASE
* Transforms the (1) of human plasma into (2), an active proteolytic enzyme that digests fibrin and other proteins allowing bacteria to escape from blood clots.
* Its action is blocked by (3A) and (3B)
1. plasminogen
2. plasmin
3. non-specific serum inhibitors; anti-streptokinase antibody.
44
[1]
* Liquefies [2] by hydrolyzing DNA which promotes spread of the pathogen into the tissues.
* Are [3] and an antibody develops after streptococcal infections (especially after skin infections)
1. Streptodornase
2. purulent discharges
3. antigenic
45
[1]
•Dissolves hyaluronic acid, an important component of the
ground substance of [2].
•Aids in spreading the pathogen (3) into
the host’s tissues.
•Are [4] and antibodies produced are specific for each bacterial or tissue source.
1. Hyaluronidase
2. host’s connective tissue
3. spreading factor
4. antigenic
46
•Causes lysis of host’s white blood cells
Leukocidin
47
has been given intravenously for treatment of pulmonary emboli, coronary artery, and venous thromboses
Streptokinase
48
Mixtures of [1] and [2] are used in “enzymatic debridement” which help to liquefy exudates and facilitate removal of pus and necrotic tissue thereby allowing [3] gain better access, and infected surfaces recover more quickly
1. streptokinase
2. DNases
3. antimicrobial drugs
49
Laboratory diagnosis
Group B β-hemolytic streptococci (GBS): Streptococcus agalactiae
HABITAT AND TRANSMISSION
•Part of the [1] in approximately 5–30% of women; may also colonize [2].
•Transmission is during [3] by passage through the colonized birth canal (vertical transmission)
1. normal vaginal flora
2. lower gastrointestinal tract
3. birth
50
Laboratory diagnosis
Group B β-hemolytic streptococci (GBS): Streptococcus agalactiae
PATHOGENESIS AND CLINICAL MANIFESTATIONS
[1]
•GBS remains as a significant cause of [2] disease in the newborn
•A predisposing factor in the acquisition of disease is the [3] of neonates as antibody production does not begin until several months after birth.
•Neonatal GBS disease is associated with two clinical syndromes:
A. Early onset infection
-Occurs during the first [4] of life, however, in more than half the cases, infants become ill within the first [5] after birth.
-Acquired either by ascending infection before delivery, through [6], or during passage through a [7]
1. Neonatal meningitis and septicemia
2. invasive
3. immunologic immaturity
4. 5 to 6 days
5. 12 to 20 hours
6. ruptured fetal membranes
7. birth canal
51
[1]
Pathogen invades the [2], and gains access to the bloodstream.
-The disease spectrum includes bacteremia, pneumonia, meningitis, septic shock, and neutropenia
1. Enterococcus species and Group D streptococci (nonenterococcus)
2. pulmonary endothelial and epithelial cells
52
b. Late onset infection
- Becomes clinically evident [1] (average 3 to 4 weeks) after birth.
- Results from [2] of the organism acquisition from the mother, other caregivers, or nosocomially
- Bacteremia is the predominant clinical presentation, and about 25% of these infants also develop
1. 7 days to 3 months
2. postnatal acquisition
3. group B streptococcal meningitis
53
[1]
* GBS were known for many years as the cause of [2] in cattle.
* It was not until Lancefield defined [3] in the 1940s that their role in human disease was recognized. [4] was identified in the 1970s as a significant cause of invasive disease in the newborn
1. Bovine mastitis
2. mastitis
3. streptococcal classification
4. S. agalactiae
54
Enterococcus species and Group D streptococci (nonenterococcus)
VIRULENCE FACTORS
[1] is the major virulence factor for GBS
•A polysaccharide capsule consisting primarily of [2] •Responsible for the resistance to clearance by innate immune defenses in the bloodstream as a consequence of molecular mimicry because sialic acid is present on human cells.
•Promotes resistance to [3] by inhibiting deposition of C3b on the bacterial cell surface
1. Capsule
2. sialic acid
3. opsonin-mediated phagocytosis
55
Enterococcus species and Group D streptococci (nonenterococcus)
VIRULENCE FACTORS
[1]
•A diffusible, heat-stable, pore-forming protein
•Promotes [2] of host’s cell by formation of pores on the cell membrane
•Binds to [3] of immunoglobulins preventing opsonin-mediated phagocytosis
1. Christie-Atkins-Munch-Peterson (CAMP) Factor
2. lysis
3. Fc region
56
Enterococcus species and Group D streptococci (nonenterococcus)
VIRULENCE FACTORS
[1]
•Acts on [2] that causes lysis of a variety of host cells.
•Together with CAMP factor, produces [3]
1. β-hemolysin
2. sphingomyelin
3. synergistic hemolysis
57
[1]
- Were previously termed "[2]", but now reclassified into new genus Enterococcus
- Are part of the normal enteric microbiota and are transmitted by direct contact with [3] materials; urethra and female genital tract can be colonized.
- Are important agents of nosocomial infections; may enter the bloodstream during [4]
- May cause [5a] in adults, and [5b] in neonates.
- Less than one third are associated with human diseases. [6] is the most common and causes 85–90% of enterococcal infections; [7] causes 5–10%.
- Show resistance to [8] and other antimicrobial agents to which other streptococci are generally susceptible; [9] is usually much more antibiotic-resistant than E. faecalis
1. Enterococcus species
2. enterococcal group D streptococci
3. fecally-contaminated
4. GIT or GUT manipulation
5. endocarditis; meningitis and bacteremia
6. Enterococcus faecalis
7. Enterococcus faecium
8. penicillin
9. E. faecium
58
[1]
- Termed the "[2]" that remain in the genus Streptococcus
- Compose only a small part of the [3] of humans and animals
- Implicated in UTI, endocarditis, and septicemia.
- [4] is the most important species to humans (animal species in the bovis group have been assigned to the species Streptococcus equinus)
1. Group D streptococci
2. nonenterococcal Group D streptococci
3. enteric flora
4. Streptococcus bovis
5.
59
Streptococcus pneumoniae
Common name: Pneumococcus
HABITAT AND TRANSMISSION
•A normal colonizer of the [1] of 5–40% of humans.
•Disease develops by [2] of the organism from its habitat, esp. among individuals with weakened respiratory defenses.
•Person-to-person transmission rarely occurs by [3], usually from a healthy carrier
1. upper respiratory tract
2. endogenous spread
3. respiratory droplets
60
Streptococcus pneumoniae
PATHOGENESIS AND CLINICAL MANIFESTATIONS
[1]
•S. pneumoniae is the most common cause (about 80%) of community-acquired bacterial pneumonia esp. the elderly (after [2]), but also in infants.
•Entrance of bacteria into the lungs initiates [3] inflammatory response that fills the lungs (and bronchioles) with fluid; consolidation of fluid leads to lobar pneumonia.
•Produces a [4] with symptoms that include high fever, chills, rapid breathing, chest pain, and rust-colored sputum from blood coughed up from the lungs
•Predisposing conditions for pneumonia:
. Antecedent [5] infection: damage to mucociliary elevator
. [7] disorders
. Congestive [8]
. [9]
. Asplenia predisposes to [10]
•[11] is present in 10–20% of cases particularly evident early in the disease, when the fever is high
1. Pneumococcal pneumonia
2. 65 years
3. acute and massive
4. lobar pneumonia
5. influenza or measles
6. Chronic obstructive pulmonary
8. heart failure
9. Alcoholism
10 septicemia
11.Bacteremia
61
Streptococcus pneumoniae
PATHOGENESIS AND CLINICAL MANIFESTATIONS
[1]
•Occuring readily in children, bacteria gain access to the [2] causing sinusitis; or into the chamber of the [3] by way of the eustachian tube and cause middle ear infection called [4]
1. Sinusitis and otitis media
2. paranasal sinuses
3. middle ear
4. otitis media
62
Streptococcus pneumoniae
PATHOGENESIS AND CLINICAL MANIFESTATIONS
[1]
•Most common cause of [2] among adults, when organisms from the [3] reach the CNS; may also [4a] and [4b]
1. Systemic complications / Other infections
2. meningitis
3. respiratory tract
4. endocarditis; septic arthritis
63
Streptococcus pneumoniae
VIRULENCE FACTORS
[1]
•Classifies pneumococci into more than [2] serotypes
•The primary virulence factor of pneumococci, with some [3] more virulent than the others. In adults, 4] are responsible for about 75% of cases of pneumococcal pneumonia and for more than half of all fatalities in pneumococcal bacteremia; in children, [5] are frequent causes of infection; no virulence if without capsule.
•Delays [6] thereby promoting multiplication of the organism in the tissues of the host
1. Polysaccharide capsule
2. 90
3. capsular types
4. capsular types 1–8
5. types 6, 14, 19, and 23
6. ingestion by phagocytes
64
•Enzyme that cleaves IgA, allowing bacteria to adhere to and colonize mucous membranes
IgA protease
65
[1]
•Exhibits toxicity for [2] and direct effect on cilia that contributes to the disruption of endothelial barrier.
•Facilitates the access of pneumococci to the [3] and eventually their spread beyond into the bloodstream.
•Lyses phagocytes and suppresses host [4]
1. Pneumolysin O
2. pulmonary endothelial cells
3. alveoli
4. inflammatory and immune functions
66
[1]
•Also referred to as spreading factor
•It hydrolyses [2], an important component of mucus that covers cells of the respiratory tract and protects them from bacterial attachment
2. neuraminic acid
67
•Is an autolysin that causes lytic dispersal of pneumolysin and hemolysin
Amidase
68
•Causes dermal hemorrhage in experimental animals
Purpura-producing principle
69
[1]
The most prevalent members of the normal microbiota of the
oropharynx.
•The most frequent cause of (SBE) in individuals with damaged (or prosthetic) heart valve.
•May enter the blood stream through [4a] procedure (tooth
extraction, or dental prophylaxis) or by simply [4b]; form [5] that bind vegetations (consist of fibrin, platelets, blood cells, and bacteria) on the damaged heart valves; the clinical course of the diseases is [6a] , but is [6b] in untreated cases
1. Viridans streptococci
2. bacterial endocarditis
3. subacute
4. denta; brushing the teethl
5. biofilm
6. gradual; invariably fatal
70
Viridans streptococci
[1] is a normal flora of the oral cavity and is responsible
for dental caries (tooth decay) due to the following activities of bacteria when they are not removed regularly through brushing and flossing:
-[2] --- S. mutans synthesizes large
polysaccharides, dextrans, that build up on the surfaces of the teeth, entrap bacteria and food debris. The combination of dextrans, bacteria, and debris is known as dental plaque, which fosters dental caries.
-[3] --- S. mutans and other bacteria in plaque produce large amounts of acids that will break down the enamel of the teeth
1. S. mutans
2. Biofilm formation
3. Carbohydrate fermentation
71
LABORATORY DIAGNOSIS OF STREPTOCOCCI
Specimens
Specimens to be obtained for culture depend on the nature of the streptococcal infection.
What are the 5 specimen
* Throat swab
* Pus
* Cerebrospinal fluid
* Blood
* Other sterile body fluid
72
LABORATORY DIAGNOSIS OF STREPTOCOCCI
Procedure Notes
G. Microscopy
[1]
•G+ cocci in chains
-[2a], however, [2b] forms are occasionally seen.
-Tend to appear as chains of [3a] rather than as chains of [3b.
-[4] will show more chaining than those made from agar plates
1. Streptococcus and Enterococcus
2. Spherical or oval-shaped; rod-like
3. diplococcal cells; individual cells
4. Broth cultures
73
LABORATORY DIAGNOSIS OF STREPTOCOCCI
Procedure Notes
G. Microscopy
[1]
•G+ cocci in pairs
-Cells have slightly [2]or lancet-shaped morphology
-"[3]” may be observed surrounding the organism pairs, indicating the presence of the polysaccharide capsule
-[4] are also seen in direct smears
1. Streptococcus pneumoniae
2. elongated "lanceolate"
3. Halo
4. Single cocci or chains
74
H. Cultural method
•Culture media
[1]
[2]
[3]
- 5% Sheep BAM
- Columbia CNA
- PEA
75
H. Cultural method
Inoculation and Incubation
[1] technique
‣ Technique for inoculating throat swab for S. pyogenes: [2] the inoculating loop into the agar after streaking the blood agar plate forces some inoculum under the agar, thereby creating a relatively [3] environment.
‣ Allows [4] to display h e m o l y s i s c a u s e d b y [5].
‣ Other methods: [6 - 2]
1. Streak-stab
2. stabbing
3. anaerobic
4. subsurface colonies
5. O2 - l a b i l e streptolysin O
6. pour-plate, agar-overlay
76
Inoculation and Incubation
-Growth is enhanced [1].
-Most will grow on agar media at [2a] oC within [2b] of
incubation
1. 5% to 10% CO2
| 2a. 35-37; 48 hours
77
About 0.5 mm in diameter, grayish white, convex, entire, transparent to translucent, matte or glossy; large zone of β︎-hemolysis, 2x-4x the diameter of the colony
Group A ︎streptococci
78
Larger than group A streptococci; translucent to opaque; flat, glossy; narrow zone of β︎-hemolysis
Group B ︎streptococci
79
Grayish white, glistening; wide zone of β︎
Group C ︎streptococci
80
Grayish white, small, matte; narrow to wide zone of ︎β
Group F ︎streptococci
81
Grayish white, matte; wide zone of ︎β
Group G ︎streptococci
82
Small, gray, glistening; young (18-24 h) are dome-shaped, later (after 24-48 h) developing central depression with elevated margin (umbilicated) giving the characteristic "checker piece", "nail-head" or "draughtsman" appearance; if organism has a polysaccharide capsule, colony may be mucoid; α︎-hemolytic
S. pneumoniae
83
Minute to small, gray, domed, smooth or matte; ︎α- or gamma hemlysis
Viridans streptococci
84
Small, cream or white, smooth, entire; ︎α-, beta-, or gamma-hemolysis
Enterococcus spp
85
More intense β-hemolysis is noted in areas where the medium has been “stabbed,” pushing some of the bacteria under the medium surface. The hemolysis in these areas is due to the combined activities of streptolysin O and streptolysin S, the principal hemolysins of group A streptococci. Streptolysin O is oxygen-labile and does not show maximal activity on the surface of the agar; the surface β-hemolysis is largely due to streptolysin S, which is oxygen-stable
β-Hemolytic streptococci on sheep blood agar.
86
Partial hemolysis of the erythrocytes results in a “greening” of the agar medium surrounding the colonies (α-hemolysis). Streptococci that are α-hemolytic include S. pneumoniae, the viridans group of streptococci, and occasionally Enterococcus species
⍶-Hemolytic streptococci on sheep blood agar.
87
Colonies of Enterococcus species cultivated on sheep blood, 24 hours in an aerobic atmosphere, 37°C, typically exhibits γ-hemolysis on sheep's blood agar, but some strains are α-hemolytic or even β-hemolytic. Other ɣ-hemolytic streptococci include group D streptococci (S. bovis), and sometimes viridans streptococci
γ-Hemolytic streptococci on sheep blood agar
88
Two characteristics of S. pneumoniae can be used for presumptive identification. On the left is shown a typical α-hemolytic, dome-shaped, mucoid strain of S. pneumoniae growing on sheep blood agar. Its appearance is due to the production of large amounts of capsular polysaccharide. On the right is a close-up photograph illustrating the collapse of the central portion of the colonies owing to organism autolysis, resulting in the so-called checker-piece and nail-head colony morphologies shown here
Streptococcus pneumoniae colonies on sheep blood agar
89
I. Identification tests
[1]
[2]
1. Catalase test
| 2. Identification tests
90
Identification of ︎β-hemolytic
•Used for presumptive identification of group A β-hemolytic
streptococci (bacitracin-susceptible)
•Principle: Based on the selective inhibition of the growth of
group A β-hemolytic streptococci by low concentration of bacitracin (0.04 U
1. Bacitracin (Taxo A) test
91
Only [1] should be tested, because many α-hemolytic streptococci are susceptible to low concentrations of bacitracin
β-hemolytic streptococci
92
•Used for presumptive identification of groups C, F, or G β
emolytic streptococci; it must be performed in conjunction with bacitracin test because groups C, F, and G streptococci are also inhibited by bacitracin.
•Principle: Based on the selective inhibition of the growth of non
and non-B β-hemolytic streptococci by trimethoprim (1.25 ug) and sulfamethoxazole (23.75 ug).
SXT (Trimethoprim-sulfamethoxazole) test
93
SXT (Trimethoprim-sulfamethoxazole) test
Positive result [susceptible (S)]: [1]
Negative result [resistant (R)]: [2]
1. Any zone of inhibition around the disk
| 2. No zone of inhibition
94
SXT (Trimethoprim-sulfamethoxazole) test
```
Group A streptococcus:
[1]
Group B streptococcus:
[2]
Groups C, F, or G streptococcus:
[3]
```
A - Bacitracin (S), SXT (R)
B - Bacitracin (R), SXT (R)
C, F, G - Bacitracin (S or R), SXT (S)
95
[1]
•The test was first described in 1944 by Christie, Atkins, and
Munch–Petersen, and it is their names that provide the acronym (CAMP) for the test.
•Used for presumptive identification of bacitracin-resistant Group
[2]
•Principle: Based on the production of extracellular substance,
CAMP factor, by group B streptococci that enhances the hemolytic activity of the β-hemolysin-producing strain of Staphylococcus aureus causing "[3]" observed as a arrow-head shaped zone of clearing in the area on BAM where the two organisms intersect.
•Positive result: [4] at the
juncture of the two organisms.
Negative result: [5].
•Group B streptococcus: [B]
Group A streptococcus: [A]:
1. CAMP test
2. B β-hemolytic streptococci
3. synergistic hemolysis
4. Arrowhead-shaped zone of β-hemolysis
5. No arrowhead-shaped zone of β-hemolysis
B - CAMP-positive
A - CAMP-negative
96
* Used for presumptive identification of bacitracin-resistant Group B β-hemolytic streptococci.
* Principle: Based on the hippuricase activity of Group B streptococci that hydrolyzes hippurate to its components, benzoate and glycine
Sodium hippurate hydrolysis test
97
[1]:
Benzoic acid is precipitated by [2] (FeCl3) that persists after 10 minutes.
If the precipitate clears within 10 minutes, it is due to [3] and other proteins which are also precipitated by FeCl3 but are more readily soluble than benzoate in excess FeCl3
1. Test for benzoic acid
2. ferric chloride
3. non-specific reaction of hippurate
98
Test for benzoic acid
Positive result: [1] that persists for 10 minutes or longer.
Negative result: [2] that clears within 10 minutes.
1. Heavy precipitation
| 2. Precipitation
99
[1]:
Ninhydrin, a strong oxidizing agent, d e a m i n a t e s a l p h a - a m i n o compounds (glycine) with the release of ammonia and carbon dioxide. The released ammonia reacts with the residual ninhydrin to form a purple or deep blue color.
Positive result: [2]
Negative result: [3]
Group B streptococcus: [B]
Group A streptococcus: [A]
1. Test for glycine
2. deep blue or purple color
3 colorless or slightly yellow- pink color
B - Hippurate-positive
A - Hippurate-negative
100
[1]
The tests described here are used to differentiate Streptococcus pneumoniae from the viridans streptococci and group D enterococci
Identification of ︎α-hemolytic streptococci
101
[1]
•Principle: [2] a
quinine derivative, selectively inhibits the growth of S. pneumoniae at very low concentrations (5 ug/mL or less).
```
Positive result (optochin-susceptible): A zone of inhibition of [3] (>16 mm with 10-mm disc)
Negative result (optochin-resistant): No zone of inhibition or a zone of inhibition [4] (or <16 mm)
```
•Streptococcus pneumoniae: [5]
Viridans streptococci and group D enterococci:
1. Optochin (Taxo P) susceptibility test
2. Optochin (ethylhydrocupreine hydrochloride),
3. >14 mm with 6-mm disc
4. <14 mm
5. Optochin (S)
6. Optochin (R)
102
[1]
•Principle: S. pneumoniae produces an [2] that is activated by bile, desoxycholate, causing the organisms to undergo rapid autolysis
```
Plate test:
Positive result (bile-soluble): [3] on which the reagent was placed; an imprint of the lysed colonies may remain within the zone
```
Negative result (bile-insoluble): Colonies where the reagent was placed remains [4]
S. pneumoniae: [5a]
Viridans streptococci and group D enterococci: [5b]
1. Bile solubility test
2. autolytic, intracellular amidase enzyme
3. Disappearance of colonies
4. intact and visible
5a. Bile-soluble
5b. Bile-insoluble
103
Other methods to distinguish between Streptococcus pneumoniae and viridans streptococci
[1]
Principle: Based on the reaction of [2] with polysaccharide capsule (in S. pneumoniae, or other encapsulated bacteria) causing a [3] reaction on the surface of the organism and a change in the refractive index of the capsule itself. Microscopically, the capsule appears to swell
[4a]: Quellung (+)
[4b]: Quellung (-)
S. pneumoniae Quellung reaction: A small amount of growth is mixed with [5a] against the capsule polysaccharide, and [5b] After incubation at room temperature for 1 hour, the reaction is observed under the microscope. The organisms are outlined in light blue. A positive reaction shows lumping because of cross-linking of the antibodies and pneumococci. The halo effect around the pneumococci is apparent
1. Quellung (or Neufeld) reaction
2. specific anticapsular antibodies
3. microprecipitation
4. S. pneumoniae; Viridans streptococci
5. saline, antisera; methylene blue stain
6. capsular swelling
104
Other methods to distinguish between Streptococcus pneumoniae and viridans streptococci
[3]
Principle: Based on the ability of S. pneumoniae to ferment [1] with acid and gas production.
[2a] : Inulin (+)
[2b]: Inulin (-)
1. inulin
2. S. pneumoniae; Viridans streptococci
3. Inulin fermentation test
105
Other methods to distinguish between Streptococcus pneumoniae and viridans streptococci
[1]
Principle: Based on the sensitivity of white mouse to [2], that intraperitoneal injection of even a few of organisms (in [3]) will result in death of the mouse, usually within 1-2 days.
Streptococcus pneumoniae: [4a] w/in 1-2 days
Viridans streptococci: [4b]
1. Mouse virulence test
2. S. pneumoniae
3. sputum or CSF
4. death of the mouse; negative
106
N.B. Additional tests are performed for identifying [1] within the viridans group of streptococci
1. “typical” individual species
107
Identification of ︎Group D streptococci (ɣ-hemolytic) and Enterococcus species (︎and Enterococcus species (︎α︎-, ︎β-, or ɣ-hemolytic)
The tests are used for presumptive identification of [1] , and to distinguish them from other [2]
1. group D streptococci (nonenterococci ) and enterococci
| 2. ɣ-hemolytic streptococci
108
[1]
•Principle: Based on the ability of certain bacteria, notably group
D streptococci and Enterococcus species to grow in the presence of [2] and hydrolyze [3] into glucose and esculetin. [4], in turn, reacts with [5] (supplied by inorganic medium component ferric citrate) to form black diffusible complex.
•Positive result: [6a] of the medium.
Negative result: [6b] of the medium.
Group D streptococci / Enterococcus spp: [7a]
Viridans streptococcus, not group D: [7b]
1. Bile-esculin test
2. 40% bile (or 4% bile salts)
3. esculin
4. Esculetin
5. ferric ions
6. Blackening; No blackening
7. Bile-esculin-positive; Bile-esculin-negative
109
[1]
Principle: Based on the specific ability of Enterococcus species
to grow in the presence of [2] incorporated in either a broth or agar medium.
```
Positive result (salt-tolerant): [3a] in broth with or
without color change from purple to yellow.
Negative result (non-salt-tolerant): [3b] and no color change .
```
```
Enterococcus species (E. faecalis, E. faecium): [4a]
Group D streptococci (S. bovis and S. equinus): [4b]
```
1. Salt Tolerance Test
2. 6.5% NaCl
3. Visible turbidity; No turbidity
4. salt-tolerant; non-salt-tolerant
110
Other methods to distinguish between group D streptococci (nonenterococcal) and Enterococcus species
[1]
•Principle: Based on the hydrolysis of PYR Test ([2]) by a specific aminopeptidase enzyme, pyrrolidonyl arylamidase. Release of free β-naphthylamide is then detected by addition of the diazo dye coupler, N, N- dimethylaminocinnamaldehyde to form a [3]
Enterococcus species: [4a] Also used and is now a standard assay for the presumptive identification of group A β- hemolytic streptococci.
Group D streptococci: [4b]
1. Pyrrolidonyl Arylamidase (PYR) Test
2. L-pyrrolidonyl-β-naphthylamide
3. red Schiff base
4. PYR-positive; PYR-negative
111
Other methods to distinguish between group D streptococci (nonenterococcal) and Enterococcus species
[1]
•Enterococcus species: [2a]
•Group D streptococci (nonenterococcus): [2b]
1. Susceptibility to penicillin
| 2. penicillin-resistant; penicillin-susceptible
112
PREVENTION AND CONTROL
* Prevention of the non-suppurative sequelae of [1] infection requires detection and early antimicrobial therapy of respiratory and skin infections caused by the organism.
* Individuals who have suffered an attack of rheumatic fever are recommended to undergo [2].
* Control of [3]also consists of eradication of S. pyogenes from carriers in medical facilities such as delivery rooms, operating rooms, and nurseries.
* Screen pregnant women at 35 to 37 weeks of gestation with [4] Patients with positive culture should receive intrapartum prophylaxis to prevent infection to the newborn.
* For individuals with damaged heart valves, chemoprophylactic use of penicillin and gentamicin prior to intestinal or urinary tract manipulations is effective in the prevention of [5] associated with enterococci and nonenterococci; also, of endocarditis associated with [6] prior to dental work.
1. S. pyogenes
2. anti-streptococcal prophylaxis
3. hospital-acquired GAS infections
4. rectal and vaginal swabs
5. endocarditis
6. viridans streptococci
113
PREVENTION AND CONTROL
Two types of vaccines are now available for the prevention of disease due to S. pneumoniae: [1a] and [1b].
- PSV-23 ([2]) contains 23 types of pneumococcal capsular antigen. It is recommended for (a) persons who are aged [3a], (b) persons aged [3b] with chronic or immunosuppressing medical conditions, (c) those who have functional or anatomic [3c] (e.g., sickle cell disease, splenectomy).
- PCV-7([4]) contains 7 types of capsular polysaccharides conjugated to inert [5]. It is recommended for all children ages 2–23 months to help prevent [6] and for selected children aged 24–59 months.
- PCV-13 ([7]), contains the polysaccharide conjugates of the serotypes found in the PCV-7 vaccine plus 6 more serotypes. It is recommended for all children as a four-dose series at [8] of age
1. pure polysaccharide vaccines; polysaccharide-protein conjugate vaccines
2. pneumococcal polysaccharide vaccine
3. 65 years or greater; 2–64 years; asplenia
4. pneumococcal conjugate vaccine 7
5. diphtheria toxin protein
6. invasive infections
7. pneumococcal conjugate vaccine 13
8. 2, 4, 6, and 12–15 months
