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General > Principles microbiology > Flashcards

Principles microbiology Flashcards

1
Q

Describe the basic structure of bacteria.

A

Bacteria are generally small, single celled prokaryotes. They have a cell wall containing peptidoglycan

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2
Q

What colour do gram negative bacteria stain?

A

Gram negative bacteria stain pink.

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3
Q

What colour do gram positive bacteria stain?

A

Gram positive bacteria stain purple.

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4
Q

What does penicillin target?

A

Penicillin targets the peptidoglycan in cell walls of bacteria.

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5
Q

What are the 3 common shapes of bacteria?

A

Cocci (spheres), bacilli (rods) and spiral-shaped.

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6
Q

Describe streptococcus.

A

Streptococci are gram positive bacteria. They grow in chains. Classified based on their haemolytic properties.

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7
Q

What are the 3 haemolytic categories of streptococci?

A

alpha, beta and gamma haemolytic strep.

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8
Q

what are the effects of alpha, beta and gamma haemolytic strep on blood agar?

A

alpha: turns blood agar green (partial haemolysis).
Beta: complete haemolysis = clear. Most pathogenic.
Gamma: no haemolysis.

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9
Q

Give 4 examples of gram positive bacteria.

A

Streptococci
Staphylococci
Enterococci
Clostridium

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10
Q

Give two examples of pathogenic gram negative cocci.

A

Neisseria meningitides.
Neisseria gonorrhoeae.
They appear as diplococci on gram film.

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11
Q

Define the term coliform.

A

Coliform is the term used to describe gram negative bacteria resembling e. coli on gram film and blood agar. They grow best aerobically, but also grow anaerobically. Many are part of normal bowel flora.

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12
Q

What is the first line antibiotic in the treatment of coliforms?

A

Gentamicin is the 1st line antibiotic used for coliform infection.

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13
Q

What type of toxins do gram negative bacteria release?

A

Gram-negative bacteria release endotoxin.

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14
Q

What is sepsis?

A

Sepsis is a response to severe infection. Small blood vessels leak fluid into tissues, causing a low blood volume and increased heart rate. Organs begin to shut down and there is an increased risk of haemorrhage.

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15
Q

Give two examples of aerobic gram-negative bacilli.

A

Pseudomonas aeruginosa

Legionella pneumophilia.

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16
Q

An aerobic gram-negative bacilli that is a common cause of chest infection, and may be controlled by vaccinations.

A

Haemophilus influenzae.

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17
Q

Describe Group A streptococci.

A

Group A streptococci are the most significant pathogenic streptococci. They are beta-haemolytic. They may cause scarlet fever, invasive disease, puerperal sepsis.

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18
Q

Describe pneumonia.

A

Pneumonia is the acute inflammation of the lungs, typically due to inhalation of Strep. pneumonia. This causes the alveoli and bronchioles to become filled with a fibrous exudate.

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19
Q

Describe strep. pneumonia.

A

Strep. pneumonia is a gram-positive alpha haemolytic cocci. It is part of the normal URT in many people, and is the most common cause of pneumonia.

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20
Q

Which non-haemolytic streptococcal bacteria is a common cause of urinary tract infection?

A

Enterococci are non-haemolytic streptococci, which are part of normal bowel flora, but may cause UTIs. They are mostly sensitive to amoxicillin.

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21
Q

Describe staphylococci.

A

Staphylococci are gram positive, immotile, and shaped in irregular grape-like clusters. They are usually catalase positive and oxidase negative.

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22
Q

Give 2 examples of staphylococci.

A

Staph. aureus.

Staph. epidermidis.

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23
Q

Which staphylococcus is associated with foreign devices, e.g. catheters.

A

Staph. epidermidis.

24
Q

Describe staph. aureus infection.

A

Staph. aureus is the most common cause of skin, soft tissue, wound, bone and joint infection. It may cause abscesses throughout the body.

25
Q

Describe clostridium.

A

Clostridium are gram positive anaerobic bacilli that are part of the normal bowel flora. They produce spores and exotoxins that cause severe tissue damage.

26
Q

Describe pseudomembranous colitis.

A

Pseudomembranous colitis is antibiotic-associated diarrhoea. It may cause nausea, fever, abdo. pain, diarrhoea, rectal bleeding or vomiting.

27
Q

What are the 5 methods of spreading infection?

A

Inhalation, ingestion, inoculation, mother to infant and intercourse.

28
Q

What are black bags, and orange bags used for?

A

Black bags are for domestic waste, orange bags are for clinical waste.

29
Q

What is an antiseptic?

A

An antiseptic is an antimicrobial agent that can safely be applied to the surface of the body or exposed tissues.

30
Q

Define disinfection.

A

Disinfection is the removal or destruction of pathogenic microorganisms.

31
Q

Define sterilisation.

A

Sterilisation is the process of killing or removing all microorganism to render an object incapable of causing infection.

32
Q

What is a virus composed of?

A

A virus consists of protein spikes, a protein coat, a nucleic acid and an envelope.

33
Q

What may adenoviruses cause?

A

Sore throats, conjunctivitis, gastroenteritis and rarely pneumonia.

34
Q

How do non-enveloped viruses enter cells?

A

Non-enveloped viruses enter cells by endocytosis.

35
Q

How may viruses be released from cells?

A

Reversal of phagocytosis, budding, lysis.

36
Q

What may antibiotics target?

A

bacterial ribosomes. cell wall, bacterial structures/enzymes.

37
Q

What may antivirals target?

A

Antivirals can target viral nucleic acid polymerases, viral enzymes, viral coat, receptors.

38
Q

What component of the immune system recognises viral proteins expressed on cell surfaces and instructs that cell to undergo apoptosis?

A

Cytotoxic T lymphocytes.

39
Q

Which neutralising antibodies prevent viruses from binding to cellular receptors?

A

IgM and IgG.

40
Q

give examples of viruses that may reactivate.

A

Herpes simplex virus and varicella-zoster virus.

41
Q

Give 2 examples of viruses causing chronic infection.

A

HIV and Hepatitis C.

42
Q

Describe antibody response with reference to titre and time.

A

Initially, IgM is the first antibody to respond at high titres. Then as time increases, titre of IgM decreases, and IgG titre increases.

43
Q

How may viral infection be detected?

A

PCR or antigen detection.

44
Q

Differentiate between the terms bacteriostatic and bacteriocidal.

A

Bacteriostatic is the inhibition of bacterial growth.

Bacteriocidal is the killing of bacteria.

45
Q

Which antibiotics target cell walls?

A

beta-lactams (penicillins and cephalosporins) and glycopeptide antibiotics target bacterial cell walls.

46
Q

How are penicillins excreted?

A

Penicillins are rapidly excreted from the body by the kidneys,

47
Q

Flucloxacillin is used to target which bacteria?

A

Flucloxacillin is a narrow spectrum antibiotic used to target staphylococci and streptococci.

48
Q

What makes up co-amoxiclav?

A

Co-amoxiclav is the combination of amoxicillin and clavulanic acid.

49
Q

What form of penicillin acts largely on coliforms?

A

Temocillin is an IV only penicillin which acts on gram negative organisms. Its activity is largely restricted to coliforms.

50
Q

Describe cephalosporins.

A

Cephalosporins are broad spectrum, and inhibit cell wall synthesis and are bacteriocidal. Excreted via kidneys in the urine. They allow the overgrowth of C. Diff.

51
Q

Describe the glycopeptide group of antibiotics.

A

Vancomycin and Teicoplanin both IV administration. Act on gram positive bacteria only.. Excreted via the kidneys, in patients with kidney failure vancomycin may reach toxic levels.

52
Q

Give an example of an aminoglycoside.

A
  1. Gentamicin is an aminoglycoside, i.e. it targets bacterial protein synthesis. Must be administered via IV. Acts mainly against gram-negative bacteria.
  2. Tetracyclines (e.g. doxycycline). They stop chain elongation by preventing tRNA attaching to acceptor sites.
53
Q

What are the side effects of tetracyclines?

A

Tetracyclines destroy normal intestinal flora causing secondary infection, stain and impair structure of bone and teeth.

54
Q

Describe the macrolide group of antibiotics.

A

Erythromycin, clarithromycin and azithromycin. They are excreted via the liver.

55
Q

which antibiotics inhibit nucleic acid synthesis?

A

Metronidazole, trimethoprim, fluoroquinolones and rifampicin.

56
Q

What are “the four C’s” associated with increased risk of C. Diff infection?

A

Cephalosporins, co-amoxiclav, ciprofloxacin and clindamycin.

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