Infectious Disease: Airborne Pathogens Flashcards Preview

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Flashcards in Infectious Disease: Airborne Pathogens Deck (23):
1

Which of the following sites would be colonised in a normal healthy person?
-Blood
-Intestinal tract
-Lymph
-Nervous system
-oral cavity
-respiratory tract
-urogenital tract

-intestinal tract
- oral cavity
-respiratory tract
-urogenital tract

2

What are the two main locations of bacterial infection?

1. Mucosal infections : colonisation of mucosal surfaces, requires adhesions, respiratory tract/gut
2. Invasion: requires colonisation, mucosal barrier breached, access to sub mucosal tissue and blood stream

3

Explain airborne transmission.
- wtr to the kind of bacteria that participant in this

- many respiratory pathogens: often gram + bacteria, resistant to drying, also viruses, human often sole reservoir

4

What are the virulence factors.

- factors that allow the organism to cause disease
1. colonisation of the niche
2. avoidance of the immune response
3. acquisition of nutrients
4. damage to the host
5. dispersal

5

Lets talk about Streptococcus pneumoniae.

- gram + diplocococcus
- found in nasopharynx of 20-40% of children
- most common causes of:
- bacterial meningitis
- problem in young and old
- community acquired pneumonia
- bacteraemia
- otitis media (ear infection )

6

Streptococcus pneumoniae:
- capsule and toxins?

- capsule : resist phagocytosis
- toxins: pneumolysin and autolysin A
L> pore forming toxins

7

Meningitis - describe it.

- inflammation of the meninges, protective membranes of the CNS
- may resolve on its own(viral meningitis)
- may be life threatening: increased pressure on brain stem, neurological damage, apnoea (stop breathing) and death

8

What are the symptoms of Meningitis ?

- 87% start with a headache
- the classic triad of diagnostic signs ( stiff neck, fever, altered menta status)
- other signs:
- sensitivity to light/sound
- irritability and delirium
- seizures
- rash in meningococcal meningitis

9

NHS bacteria associated with meningitis???????

- Neisseria meningitidis (meningococcus)
L> children and young adults
L> always penicillin sensitive
- Haemophilis influenzae
L> young children
L> often B lactamase positive (resistant to penicillin)
-Streptococcus pneumoniae (young and old, sometimes penicillin resistant, person to person spread is RARE)

10

Meningitis:
- Neisseria meningitidis?

- usually airborne
- attaches to cells of the nasopharynx
- invasive: accesses the blood stream (bacteriemia, respiratory tract infection, meningitis)

11

Meningitis:
- Neisseria meningitidis virulence factors.

- polysaccharid capsule
(protects against phagocytosis, serum resistance)
- Lipopolysaccharide (endotoxin)
L> serum resistance (innate immune system)
L> release of LPS causes toxic shock
-Adhesins: pili and opa proteins, attachment to nasopharynx

12

Explain the treatment plan of meningitis.

- treat first, diagnose later
L> give dose of benzylpenicillin immediately if meningooccal infection suspected
- a broad spectrum cephalosporin is usually given as empirical treatment of bacterial meningitis until the pathogen has been isolated and sensitivities are known
L> then rationalised to as cheap and narrow spectrum an agent as possible
- chemoprophylaxis given to kissing contacts of meningococcal infection

13

Give the stats of tuberculosis and what causes it.

- in 2007 approx 13.7 million chronic active cases, 9.3 million new cases and 1.8 million death
- 1/2 million new cases of multidrug resistant TB
- infection usually of the lungs
L> can affect other organs
L> caused by Mycobacterium tuberculosis
- most infections asymptomatic or latent
L> approx 10% lead to active disease

14

Actinobacteria: Mycobacterium :
- describe their characteristics

- rod shaped organisms, can be somewhat pleomorphic
- obligate aerobe
- facultative intracellular parasite (can live within macrophages)
- complex cell wall
- Mycobacterium tuberculosis
L> causes TB
L> some species grow very slowly (gen time of 15-20h)

15

Describe the mycobacterial cell wall.

- plasma membrane
- peptidoglycan
-arabinogalactan
- Mycolic acids
-gram positive (although it doesnt stain as one)

16

Describe the pathology of TB.

-usually infects the lungs
- cough with haemoptysis, plus quartet of fever, malaise, night sweats, weight loss
- if untreated it is often fatal

17

Describe the disease course of TB.

- primary infection
- asymptomatic or non-specific symptoms:
L> fever, malaise, weight loss, night sweats
- inhalation of droplets contaiing M.tb
L> leading to lung infection
L> delayed hypersensitivity rxn
L> formation of tubercles (aggregates of macrophage)
L> M. tuberculosis can grow in macrophage
- can progress to acute infection
L> extensive destruction of lung tissue
- infection can reactivate : immune suppression (HIV)

18

What are the virulence factors of Mycobacterium tuberculosis?

- thick complex lipid-rich cell walls (acid-fast bacilli, grows very slowly, causes chronic infections)
- intra-cellular pathogen (thrives inside macrphages, forming granulomas, antibodies have no effect, cell-mediated immune response needed for protection, controls vesicular trafficking in mammalian cells)

19

Describe the treatment of TB.

- multi-drug regimens used (prevent the emergence of resistance during therapy and more effective)
- drugs specific to TB: ethambutol, isoniazid, pyrazinamide, rifampicin, streptomycin
- drug regime: initial phase- three drugs for two months. Continuation phase - 2 drugs for 4 months

20

Explain viruses wrt respiratory tract infections.

- very common cause of respiratory infection
- usually acute self limiting infections
- cold
L> short duration, mild symptoms
- influenza: outbreaks occur annually, epidemics and pandemics occur periodically
- common childhood infections: measles, mumps, rubella and chickenpox

21

Explain symptoms, complications and acute resolving infections for Measles.

- acute, resolving infections: highly infections, can cause epidemics, paramyxovirus (encode a haemagglutinin), negative strand RNA virus
- symptoms: nasal, discharge, redness of eyes, cough, fever, cough and fever intensify and rash appears
-complications: inner ear infection, pneumonia, measles encephalomyelitis

22

Describe the measles virus.
L> envelope
L>importance in virulence

- glycoproteins in envelope: haemagglutinin (H) and fusion (F) proteins
- important in virulence: bind to host cell receptors, allow fusion with host cell and viral uptake, vary between measles strains

23

Infection process. Where are microorganisms most commonly found?

- mucous membranes
L> coated with a protective layer of viscous soluble glycoproteins called mucus