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First Aid > Microbiology: Bacteria > Flashcards

Microbiology: Bacteria Flashcards

1
Q

Peptidoglycan

A

Gives rigid support, protects against osmotic pressure

  • Sugar backbone with peptide side changes crosslinked with transpeptidase
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2
Q

Cell wall/ cell membrane

A

Major surface antigen

  • Peptidoglycan for support
  • Lipoteichoic acid induces TNF and IL-1
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3
Q

Outer membrane

(gram negative)

A

Site of endotoxin

  • Lipopolysaccharide (LPS)
  • major surface antigen
  • Lipid A induces TNF and IL1
  • O polysaccharide is the antigen
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4
Q

Plasma membrane

A

Site of oxidative and transport enzymes

  • Phospholipid bilayer
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5
Q

Ribosome

A
  • Protein synthesis
  • 50s and 30s
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6
Q

Periplasm

A

Space between the cytoplasmic membrane and outer membrane in gram negative bacteria

  • Contains many hydrolytic enzymes
  • B-lactamase
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7
Q

Capsule

A

Protects against phagocytes

  • Polysaccharide ( except in B. anthracis, which contains D-glutamate)
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8
Q

Pilus/ Fimbria

A

mediate adherence of bacteria to cell surface

  • Sex pilus: attachment between 2 bacteria during conjugation
  • Glycoprotein
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9
Q

Flagellum

A

Motility

  • made of protein
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10
Q

Spore

A

Resistant to dehydration, heat and chemicals

  • keratin-like coat, dipicolinic acid,
  • peptidoglycan
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11
Q

Plasmid

A

Contains a variety of genes for antibiotic resistance, enzymes and toxins

  • Made of DNA
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12
Q

Glycocalyx

A

Mediate adherance to surfaces

  • made of polysaccharides
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13
Q

Cell wall of Gram negative

A
  • Cytoplasmic membrane
  • Periplasm*
  • Peptidoglycan
  • Outer membrane (endotoxin, LPS) *
  • Capsule
  • Flagellum/ pillus
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14
Q

Cell wall of gram positive

A
  • Cytoplasmic membrane
  • cell wall with peptidoglycan
  • capsule
  • Lipoteichoic acid (G+ only)
  • pillus/ flagellum
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15
Q

Bacterial Morphology:

Coccus

A

Gram (+)

  • Staphylococcus
  • Streptococcus

Gram (-)

  • Neisseria
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16
Q

Bacterial Morphology:

Bacillus

A

Gram (+)

  • Clostridium
  • cornyebacterium
  • bacillus
  • listeria
  • mycobacterium

Gram (-)

  • E. Coli, Shigella, Salmonella, Klebsiella, Proteus, Enterobacter, Serratia, vibrio, campylobacter, helicobacter, pseudomonas, bacteroides
  • Haemophlius, legionella, bordetella
  • Grancisella, Brucella, Bartonella
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17
Q

Bacterial Morphology:

Branching Filamentous

A

G (+)

  • Actinomyes
  • Norcadia
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18
Q

Bacterial Morphology:

Pleomorphic

A

G (-)

  • Rickettsiae
  • Chlamydiae
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19
Q

Bacterial Morphology:

Spiral

A

G (-)

  • Borrelia
  • Leptospira
  • Treponema
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20
Q

Bacterial Morphology:

No cell wall

A

Mycoplasma

  • does not gram stain
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21
Q

Mycoplasma cell membrane

A

Contains sterols and have no cell wall

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22
Q

Mycobacteria Cell wall

A

Contain mycolic acid

High lipid content

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23
Q

Bugs that do not gram stain well

A
  • Treponema: too thin to be visualized
  • Mycobacteria: high lipid content in cell wall (acid fast)
  • Mycoplasma: no cell wall
  • Legionella pneumophilia: primarily intracellular
  • Rickettsia: intracellular parasite
  • Chlamydia: intracellular parasite
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24
Q

Giemsa Stain

A
  • Chlamydia
  • Borrelia
  • Rickettsiae
  • Trypanosomes
  • Plasmodium
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25
Q

PAS (periodic acid-schiff)

A
  • Stains glycogen
  • Whipple disease (tropheryma whipplei)
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26
Q

Ziehl-Neelsen (carbol fuscin)

A

Acid fast organisms

  • Norcadia
  • mycobacterium
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27
Q

India Ink

A

Cryptococcus neoformans

  • Mucicarmine can also be used to stain polysaccharide capsule red
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28
Q

Silver Stain

A
  • Fungi ( pneumocystis)
  • Legionella
  • H. pylori
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29
Q

Special Cultures:

N. Influenzae

A

Chocolate agar with factor V and X ( NAD+ and Hematin)

30
Q

Special Cultures:

N. gonorrhoea

N. Meningitidis

A
  • Thayer-Martin (VPN) media
    • Vancomycin ( inhibits G+)
    • Polymyxin (inhibits G-, except Neisseria)
    • Nystatin (inhibits fungi)
31
Q

Special Cultures:

B. pertussis

A

Bordet-Gengou (Potato) agar

[Bordet for Bordetella]

32
Q

Special Cultures:

C diptheriae

A

Tellurite agar

Loffler medium

33
Q

Special Cultures:

M. tuberculosis

A

Lowenstein-jensen agar

34
Q

Special Cultures:

M. pneumoniae

A

Eaton agar

requires cholesterol

35
Q

Special Cultures:

Lactose fermenting enterics

A

Pink colonies on MacConkey agar ( fermentation makes acid that turns colonies pink)

36
Q

Special Cultures:

E. coli

A

Eosin-methylene blue (EMB)

colonies with metallic green sheen

37
Q

Special Cultures:

Legionella

A

Charcoal yeast extract agar buffered with cysteine and iron

38
Q

Special Cultures:

Fungi

A

Sabourad agar

39
Q

Obligate Aerobes

A

use an oxygen dependent system to generate ATP

  • Norcadia
  • Pseudomonas aeruginosa
  • MycoBacterium TB

P. aeruginosa

  • burn wounds, complication of diabetes, nosocomial pneumonia, pneumo in CF

TB

  • Reactivation of TB has predilection for apices of lung (highest O2)
40
Q

Obligate anaerobes

A

Lack catalase or superoxide dismutase making them susceptible to oxidative damage

  • foul-smelling
  • difficult to culture
  • producegas in tissue (CO2 and H2)
  • aminoglycosides are inffective

Examples:

  • Clostridium
  • Bacteroides
  • Actinomyces
41
Q

Intracellular bugs

A

Rickettsia, Chlamydia

  • cant make own ATP
42
Q

Facultative Intracellular

A
  • Salmonella
  • Neisseria
  • Brucella
  • Mycobacterium
  • Listeria
  • Franciscella
  • Legionella
  • Yersina pestis
43
Q

Encapsulated bugs

A
  • Streptococcus pneumoniae
  • Haemophilus Influenzae type B
  • Neisseria meningitidis
  • E. Coli
  • salmonella
  • Klebsiella pneumoniae
  • Group B Strep

Opsonized and cleared by the spleen

  • asplenic–> increased risl for infections
  • give S. pneumoniae, H. influenzae, N. meningitidis vaccines
44
Q

Catalase positive

A

Catalase degrades H2O2 before it can be converted to microbicidal products by Myeloperoxidase

  • NADPH oxidase deficiency= chronic granulomatous disease have recurrent infections with catalase + organisms

organisms

  • Pseudomonas
  • Listeria
  • Aspergillus
  • Candida
  • E. Coli
  • S. aureus
  • Serratia
45
Q

Encapsulated Bacteria vaccines

A
  • Some vaccines containing polysaccharide capsule antigens are conjugated to a carrier protein
  • enhances immunogenicity by increasing T cell activation and class switching
  • Pneumococcal vaccine (PV- prevnar)
  • Pneumococcal polysaccharide vaccine with no conjugated protein (PPSV= pneumovax)
  • HiB: conjugate vaccine
  • Meningococcal vaccine (conjugate)
46
Q

Urease positive bugs

A
  • Cryptococcus
  • H. pylori
  • Proteus
  • Ureaplasma
  • Norcadia
  • Klebsiella
  • S. epidermidis
  • S. Saphrophyticus
47
Q

Pigment producing bacteria

A
  • Actinomyces isrealii: yellow sulfur granules
  • S. aureus: yellow pigment
  • Pseudomonas aeruginosa: blue-green pigment
  • Serratia marcescens: red pigment
48
Q

Virulence Factor:

Protein A

A

Binds Fc region of IgG

  • Prevents opsonization and phagocytosis
  • Expressed by S. aureus
49
Q

Virulence Factor:

IgA protease

A

Enzyme that cleaves IgA to colonize respiratory mucosa

  • S. peneumoniae
  • H. influenzae type B
  • Neisseria
50
Q

Virulence Factor:

M protein

A

Helps prevent phagocytosis

  • Expressed by group A strep
51
Q

Exotoxins

A
  • Secreted from cell
  • polypeptide
  • genes are located on plasmid or bacteriophage
  • High toxicity
  • Induces high titer antibodies
  • Toxoids are used as vaccines
  • Destroyed at 60* (except staphylococcoal toxin)
  • Disease: tetanus, botulism, diptheria
52
Q

Endotoxins

A
  • Source: outer membrane of most gram negative bacteria
  • Lipopolysaccharide
  • Genes are on bacterial chromosome
  • Low in toxicity
  • Fever, shock, hypotension, DIC
  • Induces TNF, IL1, IL6
  • Poorly antigenic
  • no toxoids-> no vaccine
  • Stable at 100* for 1 hour
  • Disease: Meningococcemia, sepsis by gram (-) rods
53
Q

Bacteria with Exotoxins:

Inhibit protein synthesis

A
  • C. diptheriae
    • Diptheria toxin: inactivates EF-2
    • pharyngtitis
  • P. aeruginosa
    • Exotoxin A: inactivates EF-2
    • causes host cell death
  • Shigella
    • Shiga toxin: inactivates 60S
    • GI mucosal damage–> dysentary, HUS
  • EHEC (0157:H7)
    • Shiga like toxin: inactivates 60S
    • enhances cytokine release causing HUS
54
Q

Bacteria with Exotoxins:

Increase fluid secretions

A
  • ETEC
    • Heat labile toxin: overactivates adenylate cyclase–> inc. cAMP –> Cl- secretion to cause watery diarrhea
    • Heat Stable toxin: overactivates guanylate cycle–> inc. cGMP–> decrease reabsorption of NaCl and water in gut
  • B. antracis
    • Edema factor: mimics adenylate cyclase enzyme to increase cAMP
    • edematous borders of black eschar in cutaneous anthrax
  • Vibrio Cholerae
    • Cholera toxin: overactivates adenlate cyclase (inc. cAMP) by permanantly activating Gs to increase Cl- secretion in gut
    • Rice water diarrhea
55
Q

Bacteria with Exotoxins:

Inhibit phagocytic ability

A

Bordetella pertussus

  • Pertussis toxin
    • overactivates adenylate cyclase (cAMP) by disabiling Gi
    • impairs phagocytosis
  • Whooping cough
    • child coughs on expiration and whoops on inspiration
    • 100 day cough in adults
56
Q

Bacteria with Exotoxins:

Inhibit release of neurotransmitter

A
  • Clostridium tetani
    • Tetanospasmin: protease that cleaves SNARE proteins required for neurotransmitter release
    • Spasticity, lock jaw
    • toxin prevents release of inhibitory (GABA and glycine) nt from Renshaw cells in spinal cord
  • Clostridium botulinum
    • Botulinum toxin: protease that cleaves SNARE
    • flaccid paralysis, floppy baby
    • toxin prevents stimulatory (ACh) signals at NMJ
57
Q

Bacteria with Exotoxins:

Lyse cell membranes

A
  • Clostridium pefringens
    • Alpha toxins: phospholipase that degrades tissue and cell membranes
    • Myonecrosis (gas gangrene)
    • Hemolysis (double zone on blood agar)
  • Streptococcus Pyogenes
    • Streptolysin O: Protein that degrades cell membrane
    • Lyses RBCs contributes to beta hemolysisi
    • Host antibodies against toxin (ASO) used to diagnose rheumatic fever
58
Q

Bacteria with Exotoxins:

Superantigens causing shock

A
  • Staphylococcus aureus
    • Toxic Shock syndrome Toxin: Bring MCH II and TCR in proximity outside of antigen binding to cause overwhelming release of INF-y and IL2
    • Toxic shock syndrome: fever, rash, shock
    • other toxins: Scalded skin syndrome (exfoliative toxins), Enterotoxin (food poisoning)
  • Streptococcus Pyogenes
    • Exotoxin A: causes overwhelming relase of INF-y and IL2 leading to shock
    • Toxic shock syndrome: fever, rash, shock
59
Q

Endotoxin Manifestations

A

LPS found in outer membrane of gram (-) bacteria

  • Activates macrophages
    • IL-1: fever
    • TNF: fever & hypotension
    • NO: hypotension
  • Activates complement
    • C3a: hypotension, edema
    • C5a: Neutrophil and chemotaxis
  • Activates tissue factor
    • Coagulation cascade–> DIC
60
Q

Transformation

A

Ability to take up naked DNA from environment

  • S. pneumoniae
  • H. influenzae type B
  • Neisseria
61
Q

Conjugation

A

F+ x F-

  • F+ plasmid contains genes required for sex pillus and conjugation
  • Plasmid (dsDNA) is replicated and transferred through pilus from F+ cell
  • no transfer of chromosomal genes
62
Q

Hfr x F-

A

F+ plasmid can become incorporated into bacterial chromosomeal DNA ( high frequency recombination)

  • Replication of recombinant DAN may include some flanking chromosomal DNA
  • transfer of plasmid and chromosomal genes
63
Q

Transposition

A

Segment of DNA ( transposons) that can jump from one location to another

  • Can transfer genes from plasmid to chromosome and vice versa
  • When excision occurs, may include some flanking chromosomal DNA which can be incorporated into plasmid and trasferred to another bacterim (antibiotic resistance genes)
64
Q

Transuduction- generalized

A

Packaging event

  • lytic phage infects bacterium
  • leads to cleavage of bacterial DNA
  • parts of bacterial chromosomeal DNA may become packaged into viral capside
  • phage infects another bacterium transferring genes
65
Q

Tranduction- specialized

A

Excision event

  • Lysogeic phage infects bacterium
  • viral DNA incorporated into bacterial chromosome
  • when phage DNA is excised, flanking bacterial genes may be excised with it
  • DNA is packaged into phage capsid and vira phage can infect another bacterium
  • Bacterial toxins that are encoded in a lysogenic phage
    • ShigA- like toxin
    • Botulinum toxin
    • Cholera toxin
    • Diptheria toxin
    • Erythrogenic toxins of S. pyogenes
66
Q

Lactose Fermenting Enteric bacteria

A

Grow pink colonies on MacConkey agar

  • Citrobacter
  • Klebsiella
  • E. coli
  • Enterobacter
  • Serratia (weak)
    *
67
Q
A
68
Q

Argyll Robertson pupil

A
  • constricts with accommodation but is not reactive to light
  • associated with tertiary syphilis
69
Q

VDRL false positives

A
  • VDRL detects nonspecific antibody that reacts with beef cardiolipin
  • test for syphilis
  • sensitive but not specific
  • many false positives
    • Viruses (mono, hepatitis)
    • Drugs
    • Rheumatic fever
    • Lupus and leprosy
70
Q

Jarisch-Herxheimer reaction

A

Flu-like syndrome after antibiotics are started due to killed bacteria releasing pyrogen

First Aid (8 decks)

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