10 - infectious diseases, symptoms & culprits Flashcards
what are our defences?
- meniges
- nasopharynx: cilia and mucus
- airways and lungs
- skin epithelia: pores and wounds
- lysozyme
- phagocytes
- blood and lymph
- flushing
what are symptomatic diseases?
infections that cause symptoms
what are asymptomatic diseases?
infections that don’t cause symptoms
what are tenacious organisms?
find ways through your skin
invasion through the epithelium leads to colonisation and growth
what is a symptom?
the body reaction to an infectious organism
whats inflammation?
- 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
Vibrio cholera
waterborne
major symptom = rice water diarrhoea
volume out = volume in
what is the major virulence factor in cholera?
cholera toxin (AB type) 1A + 5B
• encode by a phage genome
• not all strains have the toxin but its easily acquired
secretory diarrhoea in cholera
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
typical organs targeted in local inflammation
- spleen
- kidney
- lymphatic system
- cerebral spinal fluid (CSF)
what is bacteremia?
bacteria in the blood system
exploited to reach other organs
what is septicaemia?
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
Salmonella enterica
enterocolitis (gastroenteritis) - a localised infection
enteric fever (typhoid fever) - a systemic infection
horizontal gene transfer allows transfer of virulence factors
timeline of S. enterica infection
- 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
diseases of the skin
Staphylococcus and Streptococcus are commensals on healthy hosts but OPPORTUNISTIC pathogens
what are opportunistic organisms?
an organism that causes disease in the absence of normal host resistance
Streptococcus
- gram positive
- cocci - grows in chains
- can be capsulated
- S. pyogenes - group A strep
infection sites of streptococcus
- throat (pharyngitis)
- mammary glands
- skin (impetigo)
- middle ear
- lungs
associated diseases of Streptococcus
- pharyngitis
- scarlet fever
- streptococcal toxic shock syndrome
- pneumonia
Staphylococcus
- gram positive
- cocci - in grape like clusters
- infection often from asymptomatic to susceptible person
diseases of Staphylococcus
- skin - pimples, impetigo
- lungs - pneumonia
- blood - septicaemia, toxic shock syndrome
- brain - meningitis
- bones - osteomyelitis
- stomach - inflammatory food poisoning
what is MRSA?
methicillin resistant staphylococcus aureus
what is the MRSA issue?
wide used antibiotics promote selection of resistant strains
horizontal gene transfer of mecA
pneumonia
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
Mycobacterium tuberculosis
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
treatment of TB
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
Legionella pneumophila
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
symptoms of Legionella pneumophila infection
- mild cough
- headache
- fever
develops into life threatening pneumonia
elderly, immunocompromised and smokers more at risk
Helicobacter pylori
- gram negative
- motile
- spiral shaped
- related to Campylobacter
- causes infections of the stomach
diseases of Helicobacter pylori
gastritis
gastric ulcers
gastric cancer
spread by close contact
types of E. coli
NMEC – Neonatal Meningitis UPEC – Uropathogenic EHEC – Enterohaemorragic EAEC – Enteroaggegrative EIEC – Enteroinvasive EPEC – Enteropathogenic ETEC – Enterotoxigenic DAEC – Diffusely adherent
uropathogenic E. coli (UPEC)
diseases:
• acute cystitis - bladder
• pyelonephritis - kidneys
• asymptomatic bacteriuria - 55+
major virulence factor - fimbriae:
• cystitis - type 1 pilus (fim genes)
• pyelonephritis - pap genes
