module 2 rememebr

Question 1

give examples of: sporadic infection, endemic, epidemic, and pandemics. can any of these become something else and why

Answer 1

sporadic: measles – can become epidemic if low vaccination rates
endemic: rhinovirus – can become epidemic
epidemic: syphilis, monkeypox
pandemic: plague, spanish flu

Question 2

give examples of: asymptomatic, acute, chronic, and latent infections

Answer 2

asymptomatic: salmonella
acute: salmonella
chronic: salmonella
latent: varicella zoster virus

Question 3

describe characteristics of salmonella

Answer 3

causes an acute infection. can develop into a chronic, asymptomatic infection where patient shows no symptoms but can always transmit + virus is always replicating.

Question 4

describe characteristics of varicella zoster virus

Answer 4

this is a latent infection. acute infection causes disease. there is latency in neurons, and can reactivate when there is loss of immune control. reactivation means it can cause disease and spread.

Question 5

describe pathogen strategies of influenza

Answer 5

this is an acute infection with a human reservoir. it causes disease in the patient, with symptoms being cough, chills, headache, muscle ache etc.. symptoms aid in spread.

Question 6

describe pathogen strategies of candida albicans

Answer 6

this grows at many mucosal sites and on the skin. antibiotics and immunosuppression favour the overgrowth of candida. carriage, chronic, acute, asymptomatic. disease. causes symptoms which likely do not aid in its tranmission

Question 7

describe pathogen strategies of cryptosporidium parvum

Answer 7

self limiting disease in the immunocompetent and severe in the immunocompromised. it causes diarrhoea, weight loss, abdominal pain etc.. outbreak once due to contaminated water source. disease does aid in its transmission, as diarrhoea can contaminate water sources

Question 8

describe pathogen strategies of mycobacterium tuberculosis

Answer 8

this is spread by respiratory droplets. it can cause disease and spread to others. can cause acute, chronic, and latent infections. human reservoir. disease aids in transmission

Question 9

types of subtyping

Answer 9

serotyping, phage typing, RFLP, AFLP, pulse field gel electrophoresis, multi locus sequence typing, whole genome sequencing

Question 10

describe serotyping

Answer 10

tests for surface antigens.
H = flagella
K = capsule
O = LPS
latex beads are coated with antibody –> bacterial sample is mixed in –> antibody:antigen complex formation will result in agglutination
tests if isolate belongs to a particular serogroup

Question 11

describe phage typing

Answer 11

each phage has a different mechanism, and thus a different molecular target. this means variations in isolates will result in different susceptibilities to phages.
agar plate with bacterial lawn is divided up into squares –> each square is inoculated with a unique bacteriophage –> zone of lysis indicates susceptibility to that phage.
common test for S. aureus

Question 12

describe RFLP

Answer 12

restriction fragment length polymorphism.
isolate and purify DNA isolate –> digest with restriction enzymes that cut often –> separate fragments by gel electrophoresis –> transfer to a filter membrane –> probe for insertion sequences, or other highly repetitive regions –> examine.
differences in cleavage sites will result in different bands appearing. this tests if bacteria have the same/different variations – BUT DO NOT KNOW THE SPECIFIC GENETIC VARIATIONS

Question 13

describe AFLP

Answer 13

digest bacterial sample with restriction enzymes which cut often –> ligate with end specific adapters –> amplification of fragments by PCR –> analyse using gel electrophoresis.
differences in bands show variations between isolates.
DO NOT KNOW SPECIFIC VARIATIONS OR WHAT GENES THEY ARE IN

Question 14

describe PFGE

Answer 14

pulse field gel electrophoresis. treat bacterial sample with restriction enzymes which do not cut often –> separate fragments using a PFGE, which uses an alternating current to separate the large fragments.
polymorphisms/variations between isolates will show a loss of bands. tests how closely related isolates are.
COMMON FOR FOODBORNE BACTERIA

Question 15

describe MLST

Answer 15

multi locus sequence typing. looks for mutations in housekeeping genes – however these are usually synonymous.
amplification of highly conserved genes –> sanger sequencing –> identify alleles –> assignment of allele sequence type.
USE OF HIGHLY CONSERVED GENES OFTEN FAILS TO DETECT VARIABILITY BETWEEN CLOSELY RELATED ISOLATES.
SEQUENCING OF 7 HK GENES IS USUALLY TIME CONSUMING AND COSTLY

Question 16

pros and cons of WGS

Answer 16

pros:
- know exact polymorphism and what gene it is in
detects how closely related isolates are
higher resolution than other subtyping methods
cons:
- relatively slow and expensive