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Microbiology > Gram + > Flashcards

Flashcards in Gram + Deck (155):
1

gram + colour?

purple/blue

2

Gram + - subgroups

1. cocci
2. Robs (bacilli)
3. branching filaments

3

gram + branching filaments - bugs (and characteristics)

1. Actinomyces - anaerobe, not acid fast
2. Nocardia - aerobe, acid fast

4

gram + robs - bugs (and characteristics)

1. Clostiridium - spore forming, anaerobe
2. Bacillus - spore forming, aerobe
3. Listeria - no spore forming, tumbling motile, aerobe
4. corynobacterium - no spore forming, non-motile, aerobe

5

gram + cocci are divided to (and characteristics)

1. staphylococcus (cat+, clusters)
2. streptococcus (cat-, chains)

6

staphylococcus - bugs (and characteristics)

ALL CAT+, CLUSTERS
1. S. aureus (coagulase +)
2. S. epidermidis (novobiosin sensitive)
3. S. saprophyticus (novobiosin resistant)

7

streptococci are divided into subgroups according to (and the meaning)

hemolysis
1. partially hemolysis (α)
2. complete hemolysis (clear) (β)
3. no hemolysis (γ)

8

β hemolytic streptococci - bugs (and characteristics)

1. S pyogens (group A, Bacitracin sensitive)
2. S. agalactiae (group B, Bacitracin resistant)

9

γ hemolytic streptococci - bugs (and characteristics)

1. enterococcus (E. faecalis, E. feacium) - Group D, growth in bile and 6.5% NaCL
2. Nonenterococcus (Streptococcus bovis) - Group D, Growth in bile, not in 6.5 NaCL

10

entrococcus - hemolysis?

either a- or γ- hemolytic

11

α hemolytic streptococci - bugs (and characteristics)

1. S. pneumoniae - Capsule, Optichin sensitive, Bile soluble (lysed by bile)
2. Viridaans streptococci (eg. S. mutans, S. sanguinis, S. mitis) - no capsule, optochin resistant, bile soluble (lysed)

12

drugs to use to differentiate gram + bugs (and how)

1. novobiocin --> staphyloccous epidermidis is sensitive, but staphylococcus saprophyticus is resistatn
2. Optichin --> Streptococcus pneumoniae is sensitive but viridans streptococci is resistant
3. Bcitracin --> S pyogenes (Group A) is sensitive but S. agalactiae (Group B) is resistant

13

α hemolytic bacteria - appearance and mechanism

Partial reduction of Hb causes greenish or broownish color without clear ring around colonies on blood agar

14

β-hemolytic bacteria - appearance and mechanism

complete lysis form clear area of surrounding colony on blood agar

15

β-hemolytic bacteria - - bugs (and characteristics)?

1. Staphylococcus aureus (cat+, coagulase +)
2. Streptococcus pyogens (cat- ,group A, Bacitracin sensitive)
3. Streptococcus agalactiae (cat-, group B, Bacitracin resistant)
4. Listeria - no spore forming, tumbling motility, aerobe

16

staphylococcus saprophyticus - characteristics

gram +, cat + coag -. UREASE + cocci in clusters, novobiocin resistance

17

staphylococcus saprophyticus - clinical manifestation

Second MCC of UNCOMPLICATED UTI in young women

18

MCC and 2nd MCC of uncomplicated UTI in young women

1. E. coli
2. staphylococcus saprophyticus

19

staphylococcus saprophyticus - area of the body

Normal flora of female genital tract + perineum

20

staphylococcus epidermidis - characteristics / area of the body (clinically relevance)

gram +, cat+, coag-, UREASE +, novobiocin sensitive
normal skin flora --> contaminates blood cultures

21

staphylococcus epidermidis - clinical manifestations

infects prosthetic valves devises (hip implant, heart valve) and intravenous catheters by producing adherent biofilms

22

staphylococcus epidermidis infects prosthetic valves devises (hip implant, heart valve) and intravenous catheters by

producing adherent biofilms

23

staphylococcus aureus - characteristics

gram +, cat+, coagulase +, β-hemol,

24

staphylococcus aureus - how to evade immune system

Protein A (virulence factor) binds Fc-IgG, inhibiting complement activation and phagocytosis

25

staphylococcus aureus - area of the body

commonly colonizes the nares

26

Staphylococcus aureus can cause (clinical manifestation) ..... (only the categories)

inflammatory disease
Toxin mediated disease
MRSA infection

27

staphylococcus aureus - inflammatory disease?

1. skin infection
2. organ abscesses
3. pneumonia
4. endocarditis
5. osteomyelitis
6. septic arthritis

28

staphylococcus aureus - pneumonia?

often after virus infection

29

Staphylococcal aureus toxins

1. Toxic shock syndrome toxin (TSST-1)
2. Exfoliative
3. enterotoxin

30

Staphylococcal aureus toxins and manifestations

1. Toxic shock syndrome toxin (TSST-1) --> Toxic shock syndrome: fever, rash, shock, vomiting, desquamation, end-organ failure
2. Exfoliative --> scalded skin syndrome
3. enterotoxin --> rapid onset food poisoning

31

skin infection - staphylococcus aureus can cause

1. impetigo
2. cellulitis
3. Abscess
4. Staphylococcal scalded skin syndrome

32

cellulitis is caused by

usually S. aureus or S. pyogenes

33

impetigo is caused by

usually S. aureus or S. pyogenes

34

staphylococcal scalded skin syndrome - symptoms

1. fever
2. generalized erythematous rash with sloughing of the upper layers of the epidermis that heals completely

35

staphylococcal scalded skin syndrome - seen in

1. newborns
2. children
3. adults with renal insufficiency

36

staphylococcal scalded skin syndrome - mechanism

exotoxin (exofliative) destroys keratinocytes attachments in stratum granulosum ONLY

37

staphylococcus aureus - MRSA - infection

important cause of serious nosocomial and community-acquired infections

38

MRSA - mechanism

resistant to methicillin and nafcillin because of altered penicillin biding protein

39

staphylococcus aureus can cause .... (categories and manifestations

A. inflammatory disea: 1. skin infection 2. organ abscesses
3. pneumonia 4. endocarditis 5. osteomyelitis
B. Toxin mediated disease: 1. TSST-1 --> Toxic shock syndrome 2. Exfoliative --> scalded skin syndrome
3. enterotoxin --> rapid onset food poisoning
C. MRSA infection: serious nosocomial and community-acquired infections

40

Toxic shock syndrome toxin (TSST-1) - mechanism of action

Binds to MCH II and TCR outside of antigen binding site (polyclonal T-cel activation)to cause overwhelming release of IL-1, IL-2, INF-γ, TNF-α --> shock

41

Toxic shock syndrome - symptoms / lab

- fever, rash, shock, vomiting, desquamation, end-organ failure
- increased AST, ALT, blirirubin

42

Toxic shock syndrome - is associated with (situations)

1. S. aureus --> vaginal tampons, nasal packing
2. S. pyogenes --> painful skin infection

43

S. aureus - food poisoning is due to

ingestion of preformed toxin (enterotoxin)

44

S. aureus - food poisoning - course

short incubation period (2-6h) followed by NON-BLOODY diarrhea and emesis

45

S. aureus enterotoxin - special feature

heat stable --> not destroyed by cooking

46

S. aureus - coagulase? (relevance in manifestation)

coagulase + --> forms fibrins clot around self --> abscess

47

S. pneumoniae - characteristics

gram +, cocci, α hemolytic, Capsule, Optichin sensitive, Bile soluble (lysed by bile)

48

S. pneumoniae - appearance

Lancet-shape, gram + diplococci, encapsuled

49

S. pneumoniae - clinical manifestation

A. MCC OF: 1. Meningitis 2. Otitis media (in children)
3. Pneumonia 4. Sinusitis
B. Sepsis in sickle cell and splenectomy

50

S. pneumoniae - clinical importance of capsule

no virulence without capsule

51

S. pneumoniae - virulence factor

1. capsule
2. IgA protease

52

S. pneumoniae - sputum?

rusty

53

S. pneumoniae - sepsis in

1. sickle cell anemia
2. splenectomy

54

S pneumoniae - vaccines and structure

PCV - pneumonococcal congugate vaccine (Prevnar)
PPSV - pneumonococcal polysaccharide vaccine with no congugate protein (Pneumovax)

55

Viridans group streptococci - hemolysis? / area of the body

α / normal flora of the oropharynx

56

Viridans group streptococci - area of the body

normal flora of the oropharynx

57

Viridans group streptococci - bugs?

1. Streptococcus mutans
2. Streptococcus sanguinis

58

Viridans group streptococci - clinical manifestation

1. Streptococcus mutans + mitis --> dental carries
2. Streptococcus sanguinis --> sabacute bacterial endocarditis at damages heart valves
(It makes dextrans, which bind to fibrin-plaelet aggregates on damaged heart valve)

59

Viridans group streptococci - characteristics

a-hemolytic, no capsule, optochin resistant, bile insoluble (no lysed)

60

α hemolytic streptococci - bugs (and characteristics)

1. S. pneumoniae - Capsule, Optichin sensitive, Bile soluble (lysed by bile)
2. Viridaans streptococci (eg. S. mutans, s mutis, S. sanguinis) - no capsule, optochin resistant, bile soluble (lysed)

61

Streptococcus pyogenes - characteristics

cat- ,group A, Bacitracin sensitive, β-hemolytic

62

Streptococcus pyogenes can cause ...... (categories)

1. pyogenic
2. toxigenic
3. immunologic

63

Streptococcus pyogenes - pyogenic

1. pharyngitis
2. cellulitis
3. impetigo
4. erysipellas

64

Streptococcus pyogenes - toxigenic

1. scarlet fever
2. toxic shock like syndrome
3. necrotizing fascitis

65

necrotizing fascitis - definition and causes / aka / appearance / sensation

deeper tissue injury, usually from anaerobic bacteria or S. pyogenes. aka: flesh eating bacteria
appearance: bullae and purple color to the skin
sensation: crepitus (methane and CO2 production)

66

Streptococcus pyogenes - immunologic

1. rheumatic fever
2. acute glumorelonephritis

67

Scarlet fever - manifestation / caused by

blanching, sandpaper-like body rash, strawberry tongue and circumoral pallor in the setting of group A streptococcal pharyngitis (erytrhogenic toxin)

68

how to detect recent Streptococcus pyogenes infection

ASO titer
pyrrolidonyl arylamidase +

69

Streptococcus pyogenes - exotixins

1. exotoxin A
2. Streptolysin O
3. erythrogenic toxin

70

Streptococcus pyogenes - M antibodies

enchance host defence againste S. pyogenes
can give rise to rheumatic fever

71

Streptococcus pyogenes - M antibodies can give rise to

rheumatic fever

72

Pyrrolidonyl Arylamidase (PYR) test is / + in

a rapid test which is used for the presumptive identification of group A beta-hemolytic Streptococci adn entercocci

73

Major criteria for acute rheumatic fever

1. polyarthritis
2. carditis
3. subcutaneous nodules
4. erythema marginatum
5. Sydenham chorea

74

streptococcal pharyngitis can result in
streptococcal impetigo can result in

Pharyngitis: 1. rheumatic fever 2. glomerulonephritis
Impetigo: glomerulonephritis

75

glomerulonephritis is preceded by

streptococcal pharyngitis or impetigo
(MORE COMMONLY IMPETIGO)

76

Streptococcus agalactiae - characteristics

group (-), group B, Bacitracin resistant, β- hemolytic

77

Streptococcus agalactiae colonizes

vagina

78

Streptococcus agalactiae causes

1. pneumonia
2. Meningitis
3. Sepsis
MAINLY IN BABIES

79

test to detect Streptococcus pyogenes

Pyrrolidonyl Arylamidase (PYR) test

80

test to detect Streptococcus agalactiae

1. Hippurate test
2. CAMP test
3. PYR -

81

Streptococcus agalactiae - CAMP test

CAMP factor enlarges the area of hemolysis by S. aureus

82

Screen pregnant women for Streptococcus agalactiae at

35-37 weeks of gestation

83

patients with + culture of Streptococcus agalactiae -->

receive intrapartum penicillin for prophylaxis

84

Enterococci - bugs and characteristics

E. faecalis
E. faecium
gram +, cat -, Group D, growth in bile and 6.5% NaCL
α or γ hemolysis

85

Enterococci - area of the body

normal flora of the colon

86

Enterococci are resistant to / test to detect

penicillin G
PYR +

87

Enterococci can cause

I. UTI
2. biliary tract infection
3. sabacute endocarditis
(following GI/GU procedures)

88

Enterococci can cause UTI, biliary tract infection and sabacute endocarditis following

GI/GU procedures

89

group D streptococci - bugs (and characteristics)

1. enterococcus (E. faecalis, E. feacium) - Group D, growth in bile and 6.5% NaCL, γ hemolytic
2. Nonenterococcus (Streptococcus bovis) - Group D, Growth in bile, not in 6.5 NaCL, γ hemolytic

90

Lancefield grouping is based on

differences in the C carbohydrate on the bacterial cell wall

91

VRE are important cause of (and means)

nosocomial infection (Vancomycin-resistant enterococci)

92

Streptococcus bovis - clonizes the

gut

93

Streptococcus bovis biotype 1

Streptococcus gallolyticus

94

Streptococcus gallolyticus (Streptococcus bovis biotype 1) can cause

bacteremia and sabacute endocarditis and is associated with colon cancer

95

Streptococcus gallolyticus (Streptococcus bovis biotype 1) can cause bacteremia and sabacute endocarditis and is associated with

colon cancer (or polyps)

96

Corynobacterium diptheria causes diptheria via exotoxin encoded by

β-prophage

97

Diptheria toxin - mechanism of action

ADP-ribosilation of E2F --> INACTIVATION OF E2F ELONGATION --> inhibition of tRNA translocation --> inhibition of protein synthesis

98

diptheria - symptoms

1. pseudomembranous pharyngitis (grayish-white membrane)
2. Lymphadenopathy (bull neck)
3. myocaridits
4. arrhythmia
5. demyelination/paralysis of peripheral nerves

99

diptheria prevention?

toxoid vaccine

100

Corynobacterium diptheriae - lab diagnosis

1. gram + rob with metachromatic (blue and red) granules
2. Elek test for toxin
3. Black colonies on cystein-tellurite agar

101

test for diptheria toxin

Elek test

102

Special culture requirements - Corynebacterium diphtheriae - media ?

Tellurite agar and Loffler medium

103

Corynobacterium diptheriae - granules

metachromatic (blue and red)

104

spores - bacteria - (when)

some bacteria can form spores at the end of the stationary state when nutrients are limited

105

bacterial spore - characteristics / chemical composition

resistant to dehydration, heat and chemicals
chemical composotion: 1. keratin like - coat
2. dipicolinic acid
3. peptidoglycan

106

how to kill spores

must autoclave to potentially kill spores (as done in surgical equipment) by steaming at 121c for 15 minutes

107

spore forming bacteria - bacteria groups

1. Bacillus
2. Closturidium
3. Coxiella burnetti

108

spore forming bacteria - bugs and diseases

1. Bacillus antrhacis --> antrax
2. Bacillus cereus --> Food poisoning
3. Clostiridium botulinum --> botulism
4. Clostiridium difficile --> Antibiotic associated colitis
5. Clostiridium perfingess --> gas gangrene, food poisoning
6. Clostiridium tetani --> tetanus
6. Coxiella burnetii --> Q fever

109

Clostiridia - characteristics

gram +, spore forming, anaerobe

110

Clostiridia - bugs and characteristics

gram +, spore forming, obligate anaerobe
1. Clostiridium tetani
2. Clostiridium botulinum
3. Clostiridium perfringens
4. Clostiridium difficile

111

Clostiridia - toxins

1. Clostiridium tetani --> tetanospasmin
2. Clostiridium botulinum --> Botulinum toxin
3. Clostiridium perfringens --> Alpha toxin, head labile enterotoxin
4. Clostiridium difficile --> Toxin A (eneterotoxin), Toxin B (cytotoxin)

112

tetanospasmin blocks release of ...(from)

inhibitory neurotransmitters, GABA and glycine, from Renshaw cells in spinal cord

113

tetanospasmin - manifestations

1. spasticity
2. risus sardonicus (raised eyebrows and open grin)
3. Lockjaw (trismus)

114

tetanus is

tetanic paralysis

115

C. tetani - therapy / prevention

Prevent with tetanus vaccine
treat with antitoxin +/- vaccine booster and diazepam (for muscle spasms) and wound debridement

116

Botulinum toxin inhibit the releiase of ....(where)

ACh at neuromuscular junction (causing botulism)

117

botulism treatment

antitoxin

118

Botiulism is caused by ....

adults: ingestion of preformed toxin
babies: ingestion of spores in honey (floopy baby syndrome)

119

botulism vs tetanus according paralysis

botulism --> flaccid paralysis
tetanus --> spastic paralysis

120

classic symptoms of botulism

flaccid paralysis, including diplopia, ptosis, dysphagia, symmetric, descending motor paralysis, death due to respiratry failure

121

MC form of botulism in USA
botulism - death due to

- floopy baby syndrome
- respiratory failure

122

Clostiridium perfringens toxin and its mechanism of action

Alpha toxin: Phospholipase (lecithinase) that degrades tissue and cell membranes
enterotixin --> food poisoning

123

Clostiridium perfringens - manifestations

A. lalpha TOXIN: 1. myonecrosis (gas gangrene) 2. hemolysis (double zone of hemolyisis on blood agar)
B. spores can survie in undercooked food --> ingested, bacteria can release heat labile enetrotoxin --> food poisoning

124

Clostiridium perfringens - food poisoning

spores can survie in undercooked food --> ingested, bacteria can release heat labile enetrotoxin --> food poisoning

125

Clostiridium difficile - toxins and their action

1. Toxin A (eneterotoxin) --> binds to the brush borders of the gut --> diarrhea
2. Toxin B (cytotoxin) --> causes cytoskeletal disruption via actin depolymerization --> pseudomembranous colitis --> diarrhea

126

pseudomembranous colitis - appearance on endoscopy

yellow membrane

127

pseudomembranous colitis is often secondary to

antibiotic use, especially clidamycin or ampicillin
associated with PPI use

128

pseudomembranous colitis - diagnosis

detection of one or both toxins in stool by PCR

129

pseudomembranous colitis - treatment

metronidazole or oral vancomycin
For recurrent cases, consider repeating prior regimen, fidaxomicin, or fecal microbiota transplant

130

Bacillus anthracis - characteristics

gram +, spore forming, aerobe

131

Bacillus anthracis produce

edema toxin (anthrax toxin)

132

edema toxin - mechanism of action and manifestation

mimics the adenylate cyclase enzyme --> increases cAMP --> likely responsible for characteristic edematous borders of black eschar in cutaneous antrhax

133

Bacillus anthracis - unique structural characteristic

The only bacterium with a polypeptide capsule (contains D-glutamate)

134

Bacillus anthracis causes

Antrhax (cutaneous and pulmonary)

135

cutaneous antrhax?

painless, papule surrounded by vesicle --> ulcer with black eschar, (painless, pencrotic) --> uncommonly progress to bactremia and death

136

pulmonary antrhax? / aka?

inhalation of spores --> flu like symptoms that rapidly progress to fever, pulmonary hemorrhage, mediastinitis and shock. aka: woolsorter's disease

137

Bacillus - bugs?

1. Bacillus anthracis
2. Bacillus cereus

138

Bacillus cereus causes

foot poisoning (reheated rice syndrome)

139

Bacillus cereus poisoning - mechanism

Keeping rice warm results in germination of spores and enterotoxin formation

140

Bacillus cereus - types (and causes)

1. emetic type (preoformed heat-labile toxin, cereulide, same mechanism as cholera toxin): nausea and vomiting within 1-5 h
2. diarrheal type (heat stable toxin): watery, nonbloody diarrhea and GI pain within 8-18

141

Bacillus cereus - emetic type usually seen with

pasta and rice

142

Bacillus cereus - emetic type is caused by

cereulide, a preformed toxin

143

Bacillus cereus food poisoning - course

emetic type --> nausea and vomiting within 1-5 hrs
Diarrheal type --> watery and, nonblody diarrhea and GI pain within 8-18 hrs

144

Listeria monocytogenes - characteristics

gram (+) rob, no spore forming, tumbling motile, faculty intracellular

145

Listeria monocytogenes - intra- or extracelullar

faculty intracellular

146

Listeria monocytogenes - acquired by

1. ingestion of unpasteurized dairy products
2. ingestion of cold deli meats
3. tranplacental transmission
4. vaginal transmission

147

Listeria monocytogenes is the only gram (+) that

produce endotoxin

148

Listeria monocytogenes - mechanism of action

Forms rocket tails (via actin polymerization) that allow intracellular movement and cell-to-cell spread accross cell membranes, thereby avoiding antibody --> characteristic tumbling motility in broth

149

Listeria monocytogenes can cause

1. in pregnant --> amnionitis, septicemia, spontaneous abortion
2. newborns --> granulomatosis infantiseptica, neonatal meningitis
3. immunocompromised patients --> meningitis
4. healthy individuals --> mild gastroenteritis

150

Listeria monocytogenes - treatment

1. gastroenteritis is self limited
2. ampicillin in infants, immunocompromised, and the elderly as empirical treatment of meningitis

151

bacteria resembling fungi - bags and characteristics

1. Actinomyces - anaerobe, not acid fast, GRAM +
2. Nocardia - aerobe, acid fast, GRAM +

152

actinomyces vs Nocardia according to location

Acinomyces --> normal oral, reproductive, and GI flora
Nocardia --> found in soil

153

actinomyces vs Nocardia according to treatment

MNEMONIC: SNAP --> Sulfa - Nocardia / Actinom - Penicillin
Acinomyces --> penicillin
Nocardia --> sulfonamides

154

actinomyces vs Nocardia according to clinical manifestations

Acinomyces --> oral/facial abscess that drain through sinus tracts, PID with intrauterine device
Nocardia --> pulmonary infections in immunocompromised and cutaneous infection after trauma in immunocompoment

155

actinomyces vs Nocardia according to pigmented

Actinomyces israelli - yellow sulfur granules which are composed of filaments of bacteria