Microbes 1 and 2

Question 1

Lipopolysaccharide is found on the outer membrane of the cell wall in a gram ___ bacteria, which causes:

Answer 1

gram negative bacteria, causes a strong inflammatory response. IL-1, TNF, NO induction, causes fever and hypotension.

Complement causes neutrophil recruitment, hypotension.

TF –> coagulation cascade.

Question 2

if stains red, it is gram ____ and has ____.

if stains purple, it is gram ____ and has ____ acids

Answer 2

red= negative = Lipopolysaccharide
purple = positive = peptidoglycan and lipoteichoic acid

Question 3

gram positive cocci in a clump or cluster

Answer 3

staphyloCOCCUS aureus

Question 4

gram positive cocci in pairs and chains

Answer 4

streptoCOCCUS– S. pneumonia, s..pyogenes, enterococcus

Question 5

gram positive bacilli that forms SPORES

Answer 5

clostridium, bacillus

Question 6

gram positive bacilli that DO NOT form spores

Answer 6

listeria

corynebacterium

Question 7

T/F CDif produces spores

Answer 7

true. it is a gram positive bacilli.

Question 8

Gram negative cocci/diplococci

Answer 8

neisseria (N. gonorrhoea, N. meningitides)

Question 9

Gram negative bacilli

Answer 9

E. coli/eterobacteriales. salmonella, shigella, yersinia.

pseudomonas aeruginosa
bacteria fragilis (normal gut flora)

Question 10

CURVED gram NEGATIVE bacilli

Answer 10

campylobacter
h. pylori
vibriocholeae

Question 11

species that poorly gram stain

Answer 11

mycobacterium

spirochetes (syphilis, Lyme disease)

Question 12

All Bacilli are Gram negative except the gram positive ones (ABCDLMNOP)

Answer 12

Actinomyces
Bacillus
Clostridium (spores, gram positive)
Diptheria/Corynebacterium
Listeria (no spores, but gram positive)
Mycobacterium (no stain)
Nocardia
Oh no, what's the last one
Propionibacterium

Question 13

All cocci are gram positive except the gram negative ones NMV

Answer 13

Neisseria
Moaxellla
Veillonella

Question 14

is clostridium anaerobic

Answer 14

yes

Question 15

primary pathogen

Answer 15

one that regular causes disease even in an INTACT immune defence system.

Question 16

commensal pathogen

Answer 16

organisms that are part of the normal human flora or environment that do not usually cause infection

Question 17

opportunistic pathogen

Answer 17

organisms that have the ability to cause an infection when the immune defences are impaired.

Question 18

superantigen

Answer 18

Non-specific stimulation of T cells  uncontrolled cytokine release (IL- 1, TNF)
i.e. Toxic Shock Syndromes of Group A Streptococcus, S.aureus

type of exotoxin

Question 19

ways of overtly overcoming our immune system

Answer 19

-overwhelmign it through toxin and enzymes, T cell infection

Question 20

ways of covertly overcoming our immune system

Answer 20

• immune modulation
• capsules: some pathogens have such a large capsule its hard to eat them. Disables phagocytosis.
• biofilm production
• antigenic variation: modifying their antigens so immune system cannot recognize them. or like mimicry (ex/ schistosome H. Adult worm in the host venous system coats itself wit host antigens to evade the immune response)

Question 21

what type of bacteria takes the longest to culture

Answer 21

mycobacteria. (10d-7weeks).

most gram positive and negative bacteria takes 18-48 hours to culture

Question 22

what is susceptibility testing

Answer 22

determines whether a pathogen is susceptible or resistant to a panel of antibiotics

Question 23

minimum inhibitory concentration

Answer 23

minimum concentration of an antibiotic required to inhibit microbial growth

MIC ≤ 0.06 ug/ml are sensitive MIC = 0.12-0.5 ug/ml is intermediate MIC ≥ 1 ug/ml are resistant

Question 24

differences between IgM, IgG.

What is window period and seroconversion?

Answer 24

IgM: usually indicates an acute infection
IgG: indicates a past infection or immunity.

Window Period: patient is infected, but antibody levels not developed to levels detectable.
Seroconversion: patient’s serology changes from negative to positive.

Question 25

virulence factors of streptococcus pyogenes (strep throat)

Answer 25

1. capsulated; prevents phagocytosis
2. toxins an enzymes aid evasion of immune system and can move through tissues
3. pili M protein type antigen: prevents phagocytosis and ocmplement activation
4. lipoteichoic acid (promotes adhesion to pharynx mucosa)

Question 26

cause of acute rheumatic fever (seen in strep infection)

Answer 26

it’s an autoimmune response- cross reaction of antibodies against organisms direced against self proteins. associated complication of M-type strains tha cause pharyngitis (like strep)

Question 27

hypersenstivity reactions (types 1-4)

Answer 27

1. immediate hypersensitivity: mast cell IgE response, usually anaphylaxis
2. cytotic: Ab binds to cell surface Ag mediating cytotoxicity. Cell necrosis
3. Immune complexes: post-streptococcal glomerulonephritis. immune complexes form with host antibodies and GAS antigens. these complexes deposit in the kidney aand generate inflammation.
4. delayed type. t cell mediated. Granuloma formation.

Question 28

is enterobacteriaceae gram positive or negative

Answer 28

gram negative.

Question 29

outline the enterobacteriaceae classes

Answer 29

YES, PECKSS

yersinia, EHEC/Ecoli, Salmonella, Proteus, enterobacter, citrobacter, klebsiella, shigella, serratia.

Question 30

which type of Ecoli is seen in small bowerl? Which one produced shiga toxin?

Answer 30

ETEC: Small Bowerl.
EHEC: large bowel, shiga-toxin producing.

Question 31

what is the major virulence factor that EHEC uses to cause disease? (Ecoli 0157:H7)

Answer 31

produces exotoxin (shiga toxin) Shiga toxin causes bloody diarrhea because it dirsupts protein syntehsis of mucosa. can also damage the endothelial cells causing HUS.

Question 32

treating EColi (EHEC)

Answer 32

it’s gram negative

• carbapenems
• FQ/ ciprofloxacin (broad)
• aztreonams
• aminoglycosides like tobramycin, gentamycin
• monobactams
• 4th gen cephalosporins like (ceftrixaone)
• SEPTRA (TMP-SXT)

BUT: FIRST LINE IS TO NOT DO ANYTHING. just give oral rehydration and IV fluids.