Microbiology: Bacteria Flashcards Preview

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Flashcards in Microbiology: Bacteria Deck (70):
1

Peptidoglycan

Gives rigid support, protects against osmotic pressure

  • Sugar backbone with peptide side changes crosslinked with transpeptidase

2

Cell wall/ cell membrane

Major surface antigen

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

3

Outer membrane

(gram negative)

Site of endotoxin

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

4

Plasma membrane

Site of oxidative and transport enzymes

  • Phospholipid bilayer

5

Ribosome

  • Protein synthesis
  • 50s and 30s

6

Periplasm

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

  • Contains many hydrolytic enzymes 
  • B-lactamase

7

Capsule

Protects against phagocytes

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

8

Pilus/ Fimbria

mediate adherence of bacteria to cell surface

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

9

Flagellum

Motility

  • made of protein

10

Spore

Resistant to dehydration, heat and chemicals

  • keratin-like coat, dipicolinic acid,
  • peptidoglycan

11

Plasmid

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

  • Made of DNA

12

Glycocalyx

Mediate adherance to surfaces

  • made of polysaccharides

13

Cell wall of Gram negative

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

14

Cell wall of gram positive

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

15

Bacterial Morphology:

Coccus

Gram (+)

  • Staphylococcus
  • Streptococcus

Gram (-)

  • Neisseria

16

Bacterial Morphology:

Bacillus

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

17

Bacterial Morphology:

Branching Filamentous

G (+)

  • Actinomyes
  • Norcadia

18

Bacterial Morphology:

Pleomorphic

G (-)

  • Rickettsiae
  • Chlamydiae

19

Bacterial Morphology:

Spiral

G (-)

  • Borrelia
  • Leptospira
  • Treponema

20

Bacterial Morphology:

No cell wall

Mycoplasma

  • does not gram stain

21

Mycoplasma cell membrane

Contains sterols and have no cell wall

22

Mycobacteria Cell wall

Contain mycolic acid

High lipid content

23

Bugs that do not gram stain well

  • 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

24

Giemsa Stain

  • Chlamydia
  • Borrelia
  • Rickettsiae
  • Trypanosomes
  • Plasmodium

25

PAS (periodic acid-schiff)

  • Stains glycogen
  • Whipple disease (tropheryma whipplei)

26

Ziehl-Neelsen (carbol fuscin)

Acid fast organisms

  • Norcadia
  • mycobacterium

27

India Ink

Cryptococcus neoformans

  • Mucicarmine can also be used to stain polysaccharide capsule red

28

Silver Stain

  • Fungi ( pneumocystis)
  • Legionella
  • H. pylori

29

Special Cultures:

N. Influenzae

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

30

Special Cultures:

N. gonorrhoea

N. Meningitidis

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

31

Special Cultures:

B. pertussis

Bordet-Gengou (Potato) agar

[ Bordet for Bordetella]

32

Special Cultures:

C diptheriae

Tellurite agar

Loffler medium

33

Special Cultures:

M. tuberculosis

Lowenstein-jensen agar

34

Special Cultures:

M. pneumoniae

Eaton agar

requires cholesterol

35

Special Cultures:

Lactose fermenting enterics

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

36

Special Cultures:

E. coli

Eosin-methylene blue (EMB)

colonies with metallic green sheen

37

Special Cultures:

Legionella

Charcoal yeast extract agar buffered with cysteine and iron

38

Special Cultures:

Fungi

Sabourad agar

39

Obligate Aerobes

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

Obligate anaerobes

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

Intracellular bugs

Rickettsia, Chlamydia

  • cant make own ATP

42

Facultative Intracellular

  • Salmonella
  • Neisseria
  • Brucella
  • Mycobacterium
  • Listeria
  • Franciscella
  • Legionella
  • Yersina pestis

43

Encapsulated bugs

  • 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

Catalase positive

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

Encapsulated Bacteria vaccines

  • 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

Urease positive bugs

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

47

Pigment producing bacteria

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

48

Virulence Factor:

Protein A

Binds Fc region of IgG

  • Prevents opsonization and phagocytosis
  • Expressed by S. aureus

49

Virulence Factor:

IgA protease

Enzyme that cleaves IgA to colonize respiratory mucosa

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

50

Virulence Factor:

M protein

Helps prevent phagocytosis

  • Expressed by group A strep

51

Exotoxins

  • 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

Endotoxins

  • 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

Bacteria with Exotoxins:

Inhibit protein synthesis

  • 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

Bacteria with Exotoxins:

Increase fluid secretions

  • 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

Bacteria with Exotoxins:

Inhibit phagocytic ability

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

Bacteria with Exotoxins:

Inhibit release of neurotransmitter

  • 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

Bacteria with Exotoxins:

Lyse cell membranes

  • 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

Bacteria with Exotoxins:

Superantigens causing shock

 

  • 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

Endotoxin Manifestations

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

Transformation

Ability to take up naked DNA from environment

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

61

Conjugation

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

Hfr x F-

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

Transposition

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

Transuduction- generalized

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

Tranduction- specialized

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

Lactose Fermenting Enteric bacteria

Grow pink colonies on MacConkey agar

  • Citrobacter
  • Klebsiella
  • E. coli
  • Enterobacter
  • Serratia (weak)
  •  

67

68

Argyll Robertson pupil

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

 

69

VDRL false positives

  • 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

Jarisch-Herxheimer reaction

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