Bacterial infection

Question 1

what is septic shock caused by

Answer 1

LPS on gram negative bacteria

Question 2

what three covalently linked regions does LPS consist of

Answer 2

lipid A, core oligosaccharide, O Ag polysaccharide

Question 3

what blocks the e. coli attachment site

Answer 3

treat cells with mannose -

Question 4

how does Vibrio cholerae cause diarrhoel diseases

Answer 4

cholera toxin binds to GM1 receptor and is trafficked in where the A1 subunit is released
cytosolic A1 diffuses towards adenyl cyclase…. producing cAMP that opens channels…

Question 5

what are the two main types of E.coli that cause non inflammatory diarrhoea

Answer 5

Enterotoxigenic e. coli (ETEC)

Enteropathogenic e. coli (EPEC)

Question 6

what are the three main types of E.coli that cause inflammatory diarrhoea

Answer 6

Enteroinvasive e. coli (EIEC)
Enteroaggregative e. coli (EAggEC)
Enterohaemorrhagic e. coli (EHEC)

Question 7

where does Ecoli 157 binds

Answer 7

large intestine in the crypts

Question 8

what’s the hallmark of ecoli0157 infection

Answer 8

pedestal production

Question 9

what cause production of ecoli0157 pedestals

Answer 9

actin rearrangement

Question 10

describe the process of Gram staining

Answer 10

fixation -> add crystal violet -> add iodine (to chemically fix violet to peptidoglycan) -> decolourise (to wash unbound stain) -> add counter stain (safranin)

Question 11

why do gram positive bacteria remain purple

Answer 11

because they have a thick peptidoglycan cell wall that is not easily penetrated by the solvent

Question 12

what is the pathogenicity island called in EHEC

Answer 12

Locus of Enterocyte Effacement (LEE)

Question 13

give features of EHEC Locus of enterocyte effacement

Answer 13

required for attaching and effacing lesions - ability to code the enterocyte efficient
acquired by horizontal gene transfer
lower GC content than the host cell/rest of dna

Question 14

what is the major difference between the mechanism of non inflammatory and inflammatory diarrhoeal ecolis

Answer 14

non inflammatory ecoli attach to intestinal mucosa

inflammatory ecoli attach to colonic enterocytes

Question 15

what characteristic structural changes do Ecoli trigger in enterocytes

Answer 15

attachment-effacement lesions (remove microvilli)

Question 16

give examples of problems caused by enterohaemorrhagic ecoli

Answer 16

diarrhoea, haemorrhagic colitis, haemolytic uraemic syndrome, acute renal failure, hemolytic anemia, thrombocytopenia

Question 17

what is the major toxin produced by EHEC

Answer 17

shiga-like toxin (Stx1&Stx2)

Question 18

what is the structure of shiga-like toxin and what is the function of each part

Answer 18

an enzymatic Alpha subunit (depurinates adenosine in 28S rRNA) and 5 identical Beta subunits (bind to ceramide host cell receptors eg Gb3)

Question 19

where do the Stx1 and Stx2 genes come from/ what are they carried by

Answer 19

Bacteriophage lysogens in the LEE of EHEC acquired by horizontal gene transfer

Question 20

what is different about the peyers patches in the mucous membrane of the intestine

Answer 20

elongated thickened areas with surface free of projections (villi) and depressions (Lieberkuhn glands)

Question 21

what major feature of EHEC does LEE encode for

Answer 21

the ability to induce attaching and effacing lesions on the host intestinal mucosa

Question 22

where do EHECs bind and how do they form A/E lesions

Answer 22

pedestals

M cells on Peyers patches in ileum of small intestine (via long polar fimbrae adhesions