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Gram Positive Bacteria Flashcards

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1
Q

3 medically important genus for gram cocci

A

Staphylococcus
Streptococcus

Gram (-)
Neisseria

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2
Q

Gram positive cocci that is positive in catalase testing

A

Family: Micrococcaea
Genus: Micrococcus &
Staphylococcus

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3
Q

Gram positive cocci that is negative in catalase testing

A

Family: Streptococcaceae
Genus: Streptococcus

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4
Q

Gram positive cocci that is oxidation positive for glucose degradation test

A

Micrococcus (asaccharolytic)

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5
Q

Gram positive cocci that is fermentation/ oxidation positive for glucose degradation test

A

Staphylococcus (fermentative)

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6
Q

Glucose degradation test

A

It tests an organism’s ability to ferment the sugar glucose as well as its ability to convert the end product of glycolysis, pyruvic acid into gaseous byproducts.

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7
Q

Catalase test

A

used to detect the presence of cytochrome oxidase enzyme

-differentiates family micrococcaceae/ staphylococcus (catalase +) from streptococcus(catalase -)

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8
Q

Main reagent in Catalase testing

A

Hydrogen Peroxide

  • Agua oxinada
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9
Q

Procedure for catalase testing

A
  • Add drop of 3% H2O2 solution on glass lside

- then add small amount of bacterial growth from culture medium

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10
Q

Positive reaction for Catalase testing

A

Bubbling/ Bubbles

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11
Q

Reaction during catalase testing

A

H2O2 ———> H2O + O2

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12
Q

Test used to differentiate Staphylococcus from Micrococci

A

Oxidative/ Fermentative test

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13
Q

Another test used to differentiate Staphylococcus from Micrococci

A

Microdase (modified oxidase) test

(+) blue

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14
Q

Bacteria that is positive in Microdase testing

A

Micrococcus

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15
Q

Antibiotics that are effective in differentiating Micrococcus and Staphylococcus

A

Bacitracin (most commonly used)
Furazolidone
Lysostaphin

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16
Q

________ is resistant to bacitracin

A

Staphylococcus

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17
Q

________ is susceptible/ sensitive to bacitracin

A

Micrococcus

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18
Q

General characteristics of Staphylococcus species

A
  • gram positive
  • catalase positive
  • grow best in anaerobic conditions
  • facultative anaerobes
  • non-motile
  • non-sporeforming
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19
Q

5 medically important staphylococcus species

A 
S- saprophyticus 
H- haemolyticus 
A- aureus 
L- lugdunensis
E- epidemidis
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20
Q

The most pathogenic Staphylococcus species

A

Staphlycoccus aureus

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21
Q

MRSA

A

Methicillin Resistant Staphylococcus aureus

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22
Q

Mode of transmission for Staphylococcus

A
  • Person to person transmission by fomites, air. etc.

- From infected skin lesions such as impetigo, cellulitis, boils (matagtiki)

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23
Q

Staphylococcus specie responsible for 80% suppurative infection in human

A

Staphylococcus aureus

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24
Q

Dominant site of colonization of Staphylococcus aureus

-site best used to get sample for culture

A

anterior nares, axilla, perineum, and 10-15% human skin

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25
Principal virulence factor for S. aureus
Coagulase enzyme
26
Staphylococcus aureus morphology
- gram-positive cocci - grape like or irregular clusters - produce lipochrome - Beta- hemolytic - haloduric
27
What causes the golden-yellow pigment of S. aureus on BAP
- production of lipochrome a naturally occurring fat-soluble pigment
28
3 major components of S. aureus cell wall PEPTIDOGLYCAN
- elicits production of interleukin 1 (causes fever) and opsonic antibodies - provide rigid exoskeleton - a chemoattractant (attracts polymorphonuclear cells causing inflammations) - activate complement pathway.
29
3 major components of S. aureus cell wall TEICHOIC ACID
- polymer of ribitol phosphate - regulate the cationic environment of the cell thus control the activity of autolytic enzyme responsible for growth of cell wall
30
Antiteichoic antibodies are detectable through
Gel diffusion
31
Antiteichoic antibodies are found generally in patients with __________
- active endocarditis due to S. aureus
32
3 major components of S. aureus cell wall PROTEIN A
- major protein component of Staphylococcus - major antigenic determinant unique to S. aureus - antiphagocytic by binding thru FC portions of IgG except for IgG 3.
33
Antiphagocytic
preventing the action of phagocytes or the occurrence of phagocytosis.
34
PATHOGENICITY
This term refers to the ability of tan organism to induce a local and systemic infection
35
S. aureus pathogenicity | intracellular PROTEIN RECEPTORS
- allows organism to adhere to tissue surfaces
36
S. aureus pathogenicity | intracellular POLYSACCHARIDE CAPSULE
- protect organism from complement mediated attack of polymorphonuclear (PMN) macrophages, leukocyte and etc.
37
S. aureus pathogenicity | extracellular COAGULASE
- this enzyme reacts with blood factor in the plasma to initiate clot formation - enhance deposition of fibrin around organism to protect from phagocytosis
38
S. aureus pathogenicity | extracellular LIPASE
- helps in colonization of organism on oily skin surfaces | - important in survival of organism on sebaceous area of the body
39
S. aureus pathogenicity | extracellular HYALURONIDASE
- promote invasion of organism by digesting the intracellular ground substance "glue" (hyaluronic acid) that binds connective tissue in host tissue.
40
S. aureus pathogenicity | extracellular STAPHYLOKINASE
- degradation of fibrin clot (dissolution of clot to spread infection further) - also known as fibrinolycin
41
S. aureus pathogenicity | extracellular NUCLEASE (DNAse)
- heat resistant protein - degrade nucleic acid (DNA) - lowers viscosity of exodates promoting further motility
42
S. aureus pathogenicity HEMOLYSINS - CYTOTOXINS
- lyse rbc by destroying membrane thus inducing tissue damage - chromosomal mediated - causes anemia and make iron available for growth of organism
43
S. aureus pathogenicity Alpha hemolysin
- most powerful toxin that lyses RBC, platelets, and macrophages thus inducing tissue damage. - disrupts smooth muscle in blood vessels
44
S. aureus pathogenicity Beta hemolysin
- degrades sphingomyelin, and is therefore toxic to rbcs around nerves and many kinds of cells. - Heat labile
45
S. aureus pathogenicity Delta toxin
- disrupts biologic membranes and may have a role in S. aureus diarrheal diseases. - cytolytic to erythrocytes
46
S. aureus pathogenicity Gamma toxin
- a leukocidin that lyses white blood cells | - composed of two proteins designated S and F which may interact with two proteins of Panton- Valentin leukocidin.
47
PANTON-VALENTINE LEUKOCIDINE
- composed two protein components that kills white blood cells and incapacitate phagocytic line of defense of the host. (necrosis and severe inflammation) - responsible for various skin, wound, and deep tissue infection. - encoded on a mobile phage.
48
S. aureus pathogenicity ENTEROTOXINS
- heat- stable resistant to the action of gut enzymes - produced when S. aureus grows in carbohydrate and protein foods. - responsible for food poisoning caused by S. aureus
49
Most frequently food poisoning associated enterotoxins
- Enterotoxin A& D
50
Enterotoxin associated with hospital acquired infection
- Enterotoxin B
51
Enterotoxin associated with toxic shock syndrome
- Enterotoxin F
52
S. aureus pathogenicity EXFOLIATIVE TOXINS
Responsible for: - Exfoliative dermatitis - Bullous Impetigo - Staphylococcal Scarlet fever
53
S. aureus pathogenicity TOXIC SHOCK SYNDROME TOXIN TSST - 1 (SUPERANTIGEN )
- the same with enterotoxin F - binds to MHC class II mol. yielding t-cell stimulation, which promotes manifestations of TOXIC SHOCK SYNDROME - associated with: fever, shock, multisystem involvement, including desquamative skin rash.
54
What causes food poisoning in patients with S. aureus infection?
Enterotoxins produced by the organism not by the organism itself.
55
Incubation period for food poisoning caused S. aureus
2-6 hrs. followed by abdominal cramps, nausea, vomiting, and diarrhea.
56
Food poisoning caused by S. aureus
- self-limiting | - rapid recovery which takes place within 24hrs.
57
Toxic shock syndrome is characterized by
Fever, hypotension, scarlatiniform rashes particularly in the palm and sole which desquamate. - common among women using vaginal tampoons.
58
Also referred as pyrogenic Exotoxin C
Toxic shock syndrome
59
A skin condition caused by exfoliative toxins produced by S. aureus that is common in babies/ neonates.
Staphylococcal Scalded Skin syndrome / Ritter's Disease
60
Staphylococcal Scalded Skin Syndrome is characterized by
- diffuse erythematous skin rashes involving the entire body with sloughing off the epidermal layer of the skin.
61
Skin infections caused by S. aureus
FOLLICULITIS - inflammation in hair follicle FURUNCLE - spreads to the tissue causing boils CARBUNCLE - if there is multiple foci and tissue involvement IMPETIGO - most common manif. in newborn and young children less than 5 yrs. old that is highly communicable.
62
S. aureus Diagnosis Gram Stain (presumptive)
Gram positive cocci in clusters
63
S. aureus Diagnosis Culture and Isolation BAP
- beta hemolytic pattern | - golden-yellow pigment
64
S. aureus Diagnosis Culture and Isolation Mannitol Salt Agar
- contains 7.5 % to 10% NaCl - only S. aureus grow - pH indicator is phenol red - turns medium from pink to yellow
65
Staphylococcus spp. Diagnosis Culture and Isolation Phenyl Ethyl Alcohol Colistin Nalidix Acid agar (CNA)
- inhibits gram negative organism
66
S. aureus Diagnosis Culture and Isolation Chrom Agar
- selective and differential for isolation of MRSA | - (+) mauve/ pink colonies
67
CONS coagulase negative staphylococci
S. saprophyticus | S. epidermidis
68
Coagulase
is an enzyme that converts soluble fibrinogen into soluble fibrin.
69
The only significant human pathogen that possesses the coagulase enzyme
S. aureus
70
Two types of coagulase
Cell bound and free coagulase
71
Two methods for coagulase testing
Method: Tube - free coagulase (Confirmatory) slide - cell bound coagulase
72
Positive reaction for coagulation testing
(+) White fibrin clots | (-) smooth suspension
73
For tube method in coagulase testing, for how many hrs. will you incubate the tube?
4hrs - check reaction every 30 mins. -do not extend beyond 4hrs.
74
Factors that may contribute to coagulase testing of Staphylococcus spp.
- presence of STAPHYLOKINASE enzyme which may lyse the fibrin clot thus may cause a false negative result.
75
In coagulase testing what type of Plasma is used
Rabbit Plasma/ (Anticoagulated with EDTA)
76
S. aureus Diagnosis Biochemical: THERMONUCLEASE TEST
- Staphylococcus contains heat-stable thermonuclease and coagulase negative staphylococcus does not
77
Positive reaction for Thermonuclease test
(+) Pink zone of clearing at the edge of the well with a darker blue ring at the outer periphery zone.
78
The only Staphylococci spp. that ferments mannitol
S. aureus

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