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Microbiology and immunology > Medically important Microorganisms > Flashcards

Medically important Microorganisms Flashcards

1
Q

Define a Pathogen

A

An organism capable of causing disease in it’s host

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2
Q

List the many infections in humans caused by Bacterial pathogens

A

–Nuisance – recovery without treatment – sore throats, food poisoning, skin infections.

–Deadly – Small chance of recovery without treatment - TB, Plague, Anthrax, MRSA, Cl. difficile

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3
Q

Most commonly pathogens are seen to infect?

A

respiratory system

nervous system

urogenital tract,

cardiovascular system

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4
Q

Define Pathogenesis

A

The mechanism by which a pathogen causes disease

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5
Q

Define Virulence

A

The relative ability of a pathogen to cause disease

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6
Q

Define Virulence factors

A

Properties of pathogens which contribute to disease

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7
Q

Define a Toxin

A

A microbial product able to cause host cell and tissue damage

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8
Q

How much bacteria is expelled during a sneeze?

A

10,000 to 100,000 bacteria

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9
Q

Explain the Primary infection of TB (Mycobacterium Tuberculosis)?

A

localised lung infection causing the production of aggregates (tubercles)may:spread (Miliary TB) - fatal or become dormant (immunity)

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10
Q

Explain the PostPrimary infection of TB (Mycobacterium Tuberculosis)?

A

reactivation related to aging, malnutrition, overcrowding, chronic infection

destruction of lung tissue, calcification, gradual spread

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11
Q

What is known Habitat of Streptococcus pyogenes (Sore Throat)?

A

Commonly isolated from upper respiratory tract and skin of adults

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12
Q

What is known Frequency of Streptococcus pyogenes (Sore Throat)?

A

Strep. pyogenes counts ~50% all throat infections (rest are viral)

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13
Q

What kinds of diseases can Streptococcus pyogenes cause?

A

Streptococcal pharyngitis - “strep throat” (tonsillitis)

severe sore throat,

enlarged tonsils (exudate),

mild fever

malaise

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14
Q

If untreated what can Streptococcus pyogenes lead too?

A

Scarlet fever - erythrogenic toxin ( exotoxin ), damages small blood vessels - rash

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15
Q

Explain infection with Corynebacterium diphtheriae (Diphtheria)

A

Usually infects children

The bacterium is inhaled and lodges in the throat and tonsils

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16
Q

Explain the effects of infection of Corynebacterium diphtheriae (Diphtheria)

A

Produce and exotoxin known as diphtheria toxin which kills the host cells.

Damaged host cells and replicated pathogen produce a Pseudomembrane

Toxin cause systemic damage to heart, kidneys and liver

A combination of partial suffocation and organ damage can prove fatal (5-10% death rate)

17
Q

Explain the treatments used for Corynebacterium diphtheriae (Diphtheria).

A

rare in UK and USA (DTaP/Polio/Hib immunisation: Diphtheria, Tetanus, Pertussis / Polio / - Haemophilus influenzae type b )

although ~50,000 cases occur annually world wide

Penicillin, gentomycin, erythromycin

18
Q

What is the Casusative Agent of Meningococcal Disease?

A

Neisseria meningitidis (meningococcus)

Gram -ve, encapsulated diplococcus up to 30% adults are carriers

(Bacterial / viral / fungal)

19
Q

Explain transmission/Pathogenesis with central nervous system infections

A

airborne -> nasopharynx -> bloodstream

->bacteraemia
transient appearance of bacteria in blood

20
Q

Briefly explain Meningococcemia

A

septicaemia (pathogens proliferate in blood) vascular coagulation shock -> death 17% cases

21
Q

Briefly explain Meningitis

A

meninges inflammation (membranes lining the brain) death (3%)

22
Q

Explain Primary syphilis

A

painless red ulcer, hard chancre disappears with or without treatment 4-6 weeks

23
Q

Explain Secondary syphilis

A

-runny nose,watery eyes, aches and pains, rash on palms and soles

24
Q

Explain Tertiary syphilis

A
  • Gumma formation
  • damage to large blood vessels
  • eyes (blindness),

central nervous system

(madness)

25
Q

Explain the difference between male and female symptoms with Gonorrhoea (Neisseria gonorrhoea)

A

Men -pain during urination, thick pus-containing discharge

Women-painful urination and discharge
asymptomatic or mild

26
Q

What the symptoms of Disseminated Gonococcal infection?

A

– not usually preceded by urogenital symptoms

  • rash
  • arthritis
  • heart valve infection
27
Q

What are the treatments for Disseminated Gonococcal infection?

A

Initially sensitive to penicillin

1944, 100,000 units - 4.8 million ‘70s

(chromosomal mutation, penicillinase production)

tetracyline, spectinomycin, semisynthetic cephalosporins

28
Q

Briefly explain the symptoms of Genital Chlamydial infections

A

Appear 7-14 days after exposure

Grey-white discharge males/females(abdominal pain females)

Females may be asymptomatic pelvic inflammatory disease (PID), ectopic pregnancy and infertility

29
Q

What is used to treat Genital Chlamydial infections?

A

Tetracycline or erythromycin

30
Q

What organs in the body are infected by Urinary tract infections?

A

kidneys (upper UT)

bladder (lower UT)

31
Q

UT protected from infection by?

A

– downward flushing by urine

–antimicrobial urine constituents (organic acids, antibodies)

32
Q

The interruption of urine flow causes?

A

Predispostion to paralysis of the lower body

33
Q

What are Bladder infections usually caused by?

A

90% caused by normal faecal flora

Usually originating from the patient’s own intestinal bacteria

34
Q

Explain what causes heart disease

A

Normal flora of oral cavity - enter blood during dental work, tooth brushing

In an abnormal heart, small blood clots form and are trapped in turbulent flow near defective valves

These clots trap circulating bacteria - eventually break-up and may:

block blood vessels causing tissue damage (infarction)

lodge in other body parts, skin, eyes, kidney

35
Q

How is heart disease prevented?

A

Prophylactic administration antibiotics during dentistry

36
Q

What is Subacute Bacterial Endocarditis?

A

infection of heart inner lining - heart valve

37
Q

What are the symptoms of Subacute bacterial Endocarditis?

A

fatigue, slight fever (condition gradually deteriorates over months)

38
Q

What organism causes Subacute bacterial Endocarditis?

A

Viridans streptococci Staphylococcus epidermidis

39
Q

What is Acute Bacterial Endocarditis?

A

SBE sudden and acute

Pathogenesis similar to SBE, except
- organisms more virulent

Staph. aureus, Strep. pneumoniae

Microbiology and immunology (17 decks)

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