Unit 6: Bacterial Infection

Question 1

0what are some maternal factors that can impact the developing foetal microbiome?

Answer 1

• mother’s gut microbiota
• vaginal infection
• peridontitis

Question 2

what are some postnatal factors that can impact the developing foetal microbiome?

Answer 2

• antibiotics
• breast feeding
• host genetics
• environment

Question 3

how is a healthy GIT microbiome defined?

Answer 3

a population of 10^14 bacteria of at least 1000 species and belonging to 4 major phyla, the majority (90%) of which are anaerobes

Question 4

what are some features of a dysbiosis (bad) microbiome?

Answer 4

• increase in firmicutes:bacteriodete ratio
• decrease in bacteriodes fragalis = pro-inflam
• more proteobacteria, less bifidobacteriodes

Question 5

what are the main uses of probiotics?

Answer 5

• used to maintain good/ healthy microbiota
• therapeutic restoration of the microbiome

Question 6

what are some correlations of continuous antibiotic use in early life?

Answer 6

• development of childhood asthma + milk allergies
• IBD (mouse model)
• obesity (mouse model)
• permanent alterations in microbiome

Question 7

what is the transmission sources of canine leptospirosis?

Answer 7

• contact with infected urine - both direct and indirect

Question 8

how would subclinical form of canine leptospirosis be clinically presented?

Answer 8

• inapparent, disease maintained in host
• very common form
• chronic shedding in urine

Question 9

how would peracute form of canine leptospirosis be clinically presented?

Answer 9

• acute clinical disease
• death of incidental host
• shock and internal bleeding

Question 10

how would acute form of leptospirosis be clinically presented?

Answer 10

• haemorrhage, fever, anorexia, shock, jaundice, kidney/liver failure
• reluctance to move
• death

Question 11

how would chronic form of leptospirosis be clinically presented?

Answer 11

• multisystemic organ failure, chronic hepatitis
• chronic renal damage

Question 12

what diagnostics can be used for diagnosing leptospirosis?

Answer 12

• direct leptospire detection = darkfield microscopy + culture
• molecular detection + genotyping = PCR + WGS/MLST
• serology = MAT + other immunoassays

Question 13

what is the difficulty of using culture to detect lepto infection?

Answer 13

• requires specialised media
• very rapid growth of parasite
• takes around 13 weeks to confirm infection
• many serovar, serogroups and genomospecies

Question 14

what are the pros and cons of using PCR for lepto detection?

Answer 14

• sensitive in leptospiraemic phase = early detection in acute phase
• can be used for blood and urine samples
• variable urine shedding = false neg
• costly reagents
• no identification of serovars

Question 15

what is MLST?

Answer 15

multi locus sequence typing

Question 16

what is the LIPS assay? what are good targets?

Answer 16

• luciferase immunoprecipitation assay - outer membrane proteins = LigA/LigB
  antibody binds = virulence factor that is expressed when colonising

Question 17

describe the process of the LIPS assay

Answer 17

• amplify + clone OMP gene
• subclone into expression vector (at either N or C terminal) = fusion protein
• express recombinant fusion protein - culture + lyse
• immunoprecipitate = add serum + protein A sephrarose (captures IgG + immune complexes)
• wash, add substrate + measure luminescence

Question 18

what are the current treatment options for tuberculosis?

Answer 18

• long regimen drug treatment (MDR, XDR TB)
• BCG vaccine (not effective to adult TB)

Question 19

what is different about the structure of the cell wall of mycobacteria?

Answer 19

• looks similar to g-ve (lipid-peptidoglycan-lipid) with some big differences
• long chain branched mycholic acids with glycolipids tops
• linked with lipopolysaccharides
• addition of porins

Question 20

how do mycobateria release virulence factors?

Answer 20

• ESX-1 secretion system = secretion if pore-forming toxin = EsxA = escape from phagosomal compartment

Question 21

what effects can EsxA/B have on the immune system?

Answer 21

• antagonist to TLR2
• inhibits MHCI presentation
• innate immune system still triggered

Question 22

what are some ways in which mycobacteria can inhibit phagolysosome fusion?

Answer 22

• protein and lipid secretion
• surface proteins prevent phagolysosome maturation = PI3P (maturation marker)
• PKnG = fusion inhibition

Question 23

what is being measured during a pathogen diagnostic test?

Answer 23

• growing/ cultivation of the pathogen
• nucleic acid
• surface antigens

Question 24

what is being measured during an immune response diagnostic test?

Answer 24

• antibodies
• T cell response

Question 25

what are the pros and cons of using sputum smear microscopy for AFB as a diagnostic for TB?

Answer 25

• light microscopy = inexpensive
• identifies most infectious patients
• no identification of drug resistance
• doesn’t distinguish MTB from non-TB mycobacteria

Question 26

what are the pros and cons of using urine LAM as a diagnostic for TB?

Answer 26

• inexpensive and results within 30 mins
• can be used at bedside
• only used for HIV positive patients

Question 27

what are the pros and cons of using TB-LAMP as a diagnostic for TB?

Answer 27

• simple and easy visual display
• results in an hour
• sensitivity increased as CD4 cell count decreases
• doesn’t identify drug resistance