10 - infectious diseases, symptoms & culprits

Question 1

what are our defences?

Answer 1

• meniges
• nasopharynx: cilia and mucus
• airways and lungs
• skin epithelia: pores and wounds
• lysozyme
• phagocytes
• blood and lymph
• flushing

Question 2

what are symptomatic diseases?

Answer 2

infections that cause symptoms

Question 3

what are asymptomatic diseases?

Answer 3

infections that don’t cause symptoms

Question 4

what are tenacious organisms?

Answer 4

find ways through your skin

invasion through the epithelium leads to colonisation and growth

Question 5

what is a symptom?

Answer 5

the body reaction to an infectious organism

Question 6

whats inflammation?

Answer 6

• a non-specific reaction
• induced by cytokines - interleukins and TNF-alpha
• accumulation of neutrophils
• is sometimes worse than the infection itself

can either by:
• localised - at 1 point
• systemic - uses systems in the body to travel

Question 7

Vibrio cholera

Answer 7

waterborne

major symptom = rice water diarrhoea

volume out = volume in

Question 8

what is the major virulence factor in cholera?

Answer 8

cholera toxin (AB type) 1A + 5B
• encode by a phage genome
• not all strains have the toxin but its easily acquired

Question 9

secretory diarrhoea in cholera

Answer 9

1) movement of sodium ions
2) cholera toxin B attaches to the receptor
3) ATP to cAMP drives movement of ions out of the blood
4) sodium cannot be reabsorbed through the intestine

Question 10

typical organs targeted in local inflammation

Answer 10

• spleen
• kidney
• lymphatic system
• cerebral spinal fluid (CSF)

Question 11

what is bacteremia?

Answer 11

bacteria in the blood system

exploited to reach other organs

Question 12

what is septicaemia?

Answer 12

blood borne - systemic

optic shock - inflammatory responser to bacteria or their components in the blood

response often more dangerous than the infection

sometimes mistaken for flu

Question 13

Salmonella enterica

Answer 13

enterocolitis (gastroenteritis) - a localised infection

enteric fever (typhoid fever) - a systemic infection

horizontal gene transfer allows transfer of virulence factors

Question 14

timeline of S. enterica infection

Answer 14

• ingestion of S. enterica contaminated food
• T = 15 - invasion of epithelial cells
• T = 1 hour - neutrophils appear, increased vascular permeability
• T = 3 hours - neutrophil induces tissue damager and inflammatory induced fluid accumulation
• T = 8 hours - massive effusion of neutrophils and fluid into intestinal lumen
• T = 24-48 hours - evident tissue damage, diarrhoea and more fluid accumulation

Question 15

diseases of the skin

Answer 15

Staphylococcus and Streptococcus are commensals on healthy hosts but OPPORTUNISTIC pathogens

Question 16

what are opportunistic organisms?

Answer 16

an organism that causes disease in the absence of normal host resistance

Question 17

Streptococcus

Answer 17

• gram positive
• cocci - grows in chains
• can be capsulated
• S. pyogenes - group A strep

Question 18

infection sites of streptococcus

Answer 18

• throat (pharyngitis)
• mammary glands
• skin (impetigo)
• middle ear
• lungs

Question 19

associated diseases of Streptococcus

Answer 19

• pharyngitis
• scarlet fever
• streptococcal toxic shock syndrome
• pneumonia

Question 20

Staphylococcus

Answer 20

• gram positive
• cocci - in grape like clusters
• infection often from asymptomatic to susceptible person

Question 21

diseases of Staphylococcus

Answer 21

• skin - pimples, impetigo
• lungs - pneumonia
• blood - septicaemia, toxic shock syndrome
• brain - meningitis
• bones - osteomyelitis
• stomach - inflammatory food poisoning

Question 22

what is MRSA?

Answer 22

methicillin resistant staphylococcus aureus

Question 23

what is the MRSA issue?

Answer 23

wide used antibiotics promote selection of resistant strains

horizontal gene transfer of mecA

Question 24

pneumonia

Answer 24

causes by a variety if bacterial and viral pathogens

often a secondary infection in a compromised individual

inflammation of the lung parenchyma - deep lung infection

alveolar air spaces filled with exudate, inflammatory cells and fibrin

Question 25

Mycobacterium tuberculosis

Answer 25

TB or consumption - consumes lungs and is debilitating

can lie dormant for a long time

can be latent or active

infection exploites bods own immune system - grow inside activated macrophages causing a tubicle

Question 26

treatment of TB

Answer 26

3-9 months of antibiotics

untreated kills 2/3

hard to diagnose

hard to grow - 6-8 weeks to culture on egg-glycerol type agar

Question 27

Legionella pneumophila

Answer 27

grows very well in stagnant water - 35-45 degrees

high mortality rate

found in: 
• air conditioning systems 
• hot tubs 
• dead ends of plumping systems 
• cooling towers

Question 28

symptoms of Legionella pneumophila infection

Answer 28

• mild cough
• headache
• fever

develops into life threatening pneumonia

elderly, immunocompromised and smokers more at risk

Question 29

Helicobacter pylori

Answer 29

• gram negative
• motile
• spiral shaped
• related to Campylobacter
• causes infections of the stomach

Question 30

diseases of Helicobacter pylori

Answer 30

gastritis

gastric ulcers

gastric cancer

spread by close contact

Question 31

types of E. coli

Answer 31

NMEC – Neonatal Meningitis
UPEC – Uropathogenic
EHEC – Enterohaemorragic
EAEC – Enteroaggegrative
EIEC – Enteroinvasive
EPEC – Enteropathogenic
ETEC – Enterotoxigenic
DAEC – Diffusely adherent

Question 32

uropathogenic E. coli (UPEC)

Answer 32

diseases:
• acute cystitis - bladder
• pyelonephritis - kidneys
• asymptomatic bacteriuria - 55+

major virulence factor - fimbriae:
• cystitis - type 1 pilus (fim genes)
• pyelonephritis - pap genes