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Clinical Microbiology > Clinical Microbiology 1 > Flashcards

Clinical Microbiology 1 Flashcards

1
Q

Describe the features of a eukaryote

A

e. g. fungi, protozoa, plants, animals
- DNA is carried on several chromosomes within a nucleus
- Nuclear membrane
- Cytoplasm is rich in membrane bound organelles

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2
Q

Describe the features of a prokaryote

A

e. g. bacteria
- Distinct nucleus is absent
- DNA is in the form of a single chromosome
- Additional DNA is carried in plasmids

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3
Q

Describe the classification of bacteria in terms of gram staining

A
  • Gram positive = Thick cell wall retains violet stain

- Gram negative = Thin cell wall so stains pink

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4
Q

Describe the classification of bacteria according to their shape

A

Cocci - Circle
- Streptococci (chain)
- Staphylococci (cluster)
Bacilli - Rod

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5
Q

Describe the classification of bacteria according to their growth atmosphere

A
  • Obligate aerobes - Must have oxygen
  • Faculative aerobes - Can grow with or without oxygen
  • Microaerophillic - Require oxygen at a lower concentration than in the atmosphere
  • Anaerobes - Do not require oxygen
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6
Q

What are endospores?

A

Metabolically dormant forms of bacteria that are more resistant to disinfectants, drying or heating. These endospores form when there is a shortage of nutrients and can lie dormant for years. When a spore is exposed to a favourable environment it becomes active again

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7
Q

Describe the Enzyme Linked Immunosorbent Assay (ELISA) method

A

1) A virus protein is replicated and added to a mixture
2) Protein will sink to the bottom
3) Patient’s blood sample is added
4) Antibodies in the blood bind to viral protein
5) Anti-human antibodies are added to the mixture
6) Anti-human antibodies bind to the viral protein-antibody complex
7) A colour change occurs and is detected

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8
Q

Describe the four mechanisms by which bacteria can develop resistance

A
  • Alteration of Drug Target - Target of drug e.g. receptor is altered so bacteria has a low affinity for the antibiotic
  • Access to the Drug is Altered - Bacteria may become less permeable to antibiotics or may increase the activity of their efflux pumps
  • Inactivation of the Antibiotic - Bacteria may produce antibiotic altering enzymes
  • Novel Metabolic Pathway - Bacteria may develop an entirely new pathway to cause disease so bypass the antibiotic
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9
Q

By what two mechanisms can resistance spread?

A
  • Vertical gene transfer

- Horizontal gene transfer

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10
Q

Describe the process of vertical gene transfer

A

A chromosomal mutation occurs in the bacterium and is passed down to all bacteria the mutant gives rise to. This type of resistance is very stable as the mutation is found within the chromosomes

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11
Q

Describe the process of horizontal gene transfer

A

A transfer of genetic information into the bacterial cell by one of three processes;

  • Transformation
  • Conjugation
  • Transduction
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12
Q

What three types of resistance can horizontal gene transfer give rise to?

A
  • Plasmid mediated resistance
  • Transposon mediated resistance
  • Integron mediated resistance
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13
Q

Describe plasmid mediated resistance

A

Plasmids replicate and transfer resistance genes between bacterial cells. The products of these genes tend to include;

  • Enzymes that modify the drug target
  • Enzymes that modify/degrade the antibiotic
  • Molecules that modify membrane transport mechanisms
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14
Q

Describe Transposon Mediated Resistance

A

Transposons are mobile genetic elements that jump between chromosomes and plasmids. They can move resistance genes from the chromosomes to the plasmids to allow these genes to be replicated and spread to other bacteria

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15
Q

Describe Integron Mediated Resistance

A

Integrons are genetic structures that can gather multiple resistance genes and transfer them into chromosomes or plasmids. Integrons are a very effective method of spreading multidrug resistance

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16
Q

Describe the three stages of antibiotic prescribing

A

1) Emperical prescribing - Follow the guidelines to prescribe the most appropriate antibiotic and route and speed of administration
2) Simplify/switch - Narrow down the spectrum of antibiotics and think of switching from IV to oral
3) STOP

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17
Q

What is the criteria for diagnosing sepsis?

A

Symptoms and signs of infection, plus 2 or more of;

  • Heart rate >90bmp
  • Temperature >38°C or 20 per minute
  • WCC >12 or <4
18
Q

What is the criteria for the diagnosis of severe sepsis?

A

Sepsis, plus evidence of organ hypoperfusion;

  • Confusion
  • Acute kidney injury
  • Acute derangement of LFTs
  • ARDs
  • Lactic acidosis
  • Coagulopathy
  • Hypotension
19
Q

If a patient has a true penicillin allergy, what alternatives can be offered?

A

IV vancomycin or IV gentamicin

20
Q

Describe the Sepsis Six

A

Within one hour;

1) Perform blood cultures
2) Administer antibiotics according to guidelines
3) High flow oxygen
4) Measure lactate and Hb
5) Give IV fluid
6) Monitor urinary output

21
Q

What is vertebral discitius?

A

Infection of the disc space and adjacent vertebral end plate. This can be very destructive and cause deformity of the spine which may lead to spinal cord compression and therefore disability

22
Q

Describe the treatments used for dermatophyte mould infections

A
  • Terbinafine
  • Griseofulvin
  • Itraconazole

These drugs affect the structure of the cell wall

23
Q

What are dermatophyte moulds and what are the main types?

A

Specialised moulds that invade the keratin in the hair, skin and nails;

  • Tinea capitis - Fungal scalp infections
  • Tinea unguium - Fungal nail infections
  • Tinea corporis - A circular pattern
  • Tinea barbae - Lumps/boils in males
  • Tinea pedis - Athlete’s foot
24
Q

What are the main types of non-dermatophyte moulds?

A 
Aspergillus species;
- Aspergillus fumigatus
- Aspergillus flavus
Mucoraceous moulds;
- Rhizopus
- Absidia
25
Q

Describe the treatment of non-dermatophyte moulds

A
  • Amphoterian B (Abisome)
  • Azoles (Itraconazole, posaconazole)
  • Caspofungin
26
Q

What are the two main types of yeast infection?

A
  • Candida - kidneys, hart, GI tract, lungs
  • Cryptococcus - Meningitis, chest pain, cough
    • Neoformans (pigeon droppings)
    • Gattii (gum tree)
27
Q

Describe the treatment of yeast infections

A 
SUPERFICIAL
- Fluconazole
- Itraconazole 
- Nystatin
- Clotrimazole
INVASIVE
- Amphotericin B
- Fluconazole
- Caspofungin
- Flucytosine
28
Q

What are the two main types of parasite?

A 
Protozoa
- Amoeba
- Flagellate
- Cilate
- Sporozoa e.g. malaria
Helminths
- Nematodes
- Trematodes e.g. schistosomes 
- Cestodes
29
Q

What are the five types of malaria? And for each type, what is the time between episodes of fever?

A 
P. Falciparum - Irregular (fatal)
P. Vivax - Every 2 days
P. Ovale - Every 2 days
P. Malariae - Every 3 days
P. Knowlesi - Extremely rare but can be fatal
30
Q

What is the treatment for malaria?

A
  • Malarone
  • Deoxycycline
  • Chloroquine and proguanil in combination
  • Mefloquine
31
Q

What are the two main types of schistosomes?

A
  • S. mansoni

- S. haemotobium

32
Q

What treatment is used for schistosomiasis?

A

A single tablet of prazinquantel which paralyses the worm. There are no known side effects, however it has no effect on immature worms or eggs so infection could occur again. It is effective for all species

33
Q

What is Toxoplasma Gondii?

A

A common infection that is spread from the stools of cats and birds, rodents and cattle. It is possible to become infected after ingesting undercooked meat of animals harbouring tissue cysts

34
Q

What is the treatment of toxoplasma gondii?

A

Pyrimethamine

35
Q

What are the two types of HIV?

A

HIV-1 - Related to the Simian Immunodeficiency Virus (SIV) found in chimpanzees and gorillas in West Africa
HIV-2 - Closely related to SIV in other primates known as the Sooty Mangabey

36
Q

Describe the classification of the HIV-1 virus

A

Major group - M (pandemics)

Minor groups - O and N (West Africa)

37
Q

What are the four phases of HIV infection?

A
  • Primary HIV infection (CD4 count 500-1200)
  • Asymptomatic phase (CD4 count 500+)
  • Symptomatic phase (CD4 count 200-500)
  • AIDS (CD4 count below 200)
38
Q

What is HAART?

A

Highly Active Anti-Retroviral Drug Therapy

A combination of three different ARVs prescribed when an HIV sufferer’s CD4 count falls below 350

39
Q

What are the four mechanisms by which ARVs can work?

A
  • Reverse Transcriptase Inhibitors - Prevents genetic material entering the CD4 cell’s nucleus
  • Protease Inhibitors - Inhibits the production of a new protein capsule
  • Fusion Inhibitors - Prevent the virus from binding to CCR5 and CD4 receptors
  • Integrase Inhibitors - Inhibits action of integrase enzyme
40
Q

Describe the treatment used for typhoid fever

A
  • Quinolones (however resistance is increasing)
  • 3rd gen cephalosporins
  • Azithromycin

Clinical Microbiology (2 decks)

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