lec 5-6 - clinical microbiology

Question 1

mucous

Answer 1

solution containing glycoproteins and proteins

MALT is found in most mucous membranes

Question 2

MALT

Answer 2

mucosa-associated lymphoid tissue

Question 3

primary lymphoid organs

Answer 3

thymus

bone marrow

Question 4

mechanical protection of mucous

Answer 4

hairs

skin

Question 5

bacteria in blood

Answer 5

septicemia

Question 6

what type of bacteria has outer phospholipid bilayer

Answer 6

gram -ve

Question 7

antimicrobial secretions in GI tract - stomach

Answer 7

• gastric acid
• acidic pH2
  helicobacter pylor causes stomach ulcers

Question 8

paneth cells

Answer 8

secrete lysozyme
found at the end of the crypts of Lieberkühn
intestinal glands

Question 9

natural bacteria that colonize mucous membranes

Answer 9

have their own antimicrobial peptides so are more effective

interfere with membranes
form pores
enter cells and affect RNA

Question 10

why do antimicrobial peptides attach better to bacteria

Answer 10

acidic on outside of membrane

no cholesterol

Question 11

leukocidin

Answer 11

cytotoxin produced by bacteria to kill macrophages

Question 12

exotoxins

Answer 12

formed and secreted by bacteria
most are gram +ve
split into 3 groups
very potent

Question 13

3 groups of exotoxins

Answer 13

neurotoxins
enterotoxins
cytotoxins

Question 14

neurotoxin

Answer 14

exotoxin that is destructive to nerve tissue

causes lockjaw/tetanus

Question 15

enterotoxin

Answer 15

exotoxin produced in and affecting the intestines

causes vomiting and diarrhoea

Question 16

cytotoxin

Answer 16

exotoxin or antibody

has specific toxic actions causing cell death

Question 17

endotoxin

Answer 17

normally gram -ve
not secreted - released when cells are disrupted
heat stable
less potent and less specific than exotoxins

Question 18

capsules

Answer 18

important in preventing phagocytosis
allows infection process to continue
proteinaceous components of cell not seen

Question 19

4 requirements for disease

Answer 19

portals of entry
establishment (adherence factors)
avoiding host defences
damaging host

Question 20

mucous membranes

Answer 20

form protective covering that resists penetration and traps microbes
bathed in antimicrobial secretions

Question 21

how do we protect our mucous membranes

Answer 21

wash with secretions - e.g. saliva, tears, mucous, urine
filter hairs in nasal passage
cilia in respiratory tract

Question 22

skin

Answer 22

keratinised
tough mechanical barrier
slightly acidic pH - fatty acid chains
high NaCl conc.
subject to periodic drying

Question 23

lactenin

Answer 23

proteins in breast milk
protect against mastitis
bacteriocidal against streptococcys pyogenes

Question 24

antimicrobial secretion sin GI tract - intestines

Answer 24

pancreatic/intestinal enzymes
bile
GALT (Gut associated lymphoid tisue)
secretory IgA
paneth cells - produce lysozymes, cryptins

Question 25

genitourinary tract

Answer 25

low pH of urine and vaginal epithelia
toxic metabolites (urea) present in urine
hypertonic kidney medulla
flushing with urine and mucous

Question 26

3 types of antimicrobial peptides

Answer 26

defensins
cationic peptides
bacteriocins

Question 27

defensins

Answer 27

antimicrobial peptides
rich in arginine and cysteine

function:

• defend from pathogens
• shape microbiota
• protect stem cells

Question 28

bacteriocins

Answer 28

antimicrobial peptides

lethal to closely related species

e.g. colicins, sakacins

Question 29

peyer’s patches

Answer 29

patches of lymphatic tissue

monitor intestinal bacteria and prevent growth of pathogenic bacteria in small intestine

Question 30

coagulate mechanisms for evading host defence systems

Answer 30

cause fibrin clots in blood of host

fibrin walls off the infection

Question 31

anatomical structures outside bacterial cell wall

Answer 31

glycocalyx
fimbriae and pili
flagella and axial filaments

Question 32

glycocalyx

Answer 32

polysaccharides and proteins
thin surrounding slime layer
can form a capsule

Question 33

fimbriae and pili

Answer 33

involved in adherence
found on gram -ve
aids motility

Question 34

flagella and axial filametns

Answer 34

protrudes beyond cell wall and glycocalyx
aids movement to distal tissues
can produce rotational movement of whole organism

Question 35

4 main types of HCAIs

Answer 35

UTIs
surgical site infections
bloodstream infections
pneumonia

Question 36

5 ways to determine the cause of an infection

Answer 36

rapid tests and immunoassays
molecular testing
biochemical tests
culture
microscopy

Question 37

3 types of stain based microbiology

Answer 37

gram stain
acid fast stain
PAS

Question 38

gram stain

Answer 38

differentiates between gram +ve and -ve

gram +ve stains purple

Question 39

acid fast stain

Answer 39

ziehl-neelson stain
specific
no need for culture
performed directly on sputum

Question 40

sputum

Answer 40

saliva/mucous coughed up and used to test for infection

Question 41

PAS

Answer 41

periodic acid schiff

stains for polysaccharides and glyoproteins
disadvantage - high background

Question 42

selective media

Answer 42

support growth of one type of organism while inihbiting growth of another

e.g. mannitol salt agar

Question 43

agglutination assays

Answer 43

uses immune system to tell us what weve got
doesnt require a culture
detection of viral infections
lack of agglutination can be used as the measure of infection

Question 44

mass spectrometric methods

Answer 44

MALDI TOF
ESI

cheaper than sequencing
reliant on databases of known patterns

Question 45

NAATs

nucleic acid amplification techniques

Answer 45

doesnt detect live or dead
cheap
sensitive
no standard for comparison
prone to error in set up