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Microbiology > Week 2 > Flashcards

Week 2 Flashcards

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1
Q

What is not usually added to growing microbes and why?

A

Inorganic elements such as phosphates or sulphates because they are usually present in adequate amount as contaminants.

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2
Q

What are some growth factors and when are they added?

A

Blood, serum,vitamins may be added to sterile medium just before pouring but after heat sterilisation.

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3
Q

What are buffering agents?

A

Can use soluble phosphate to absorb change in pH produced by bacteria.

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4
Q

Name and describe the 2 possible chemical composition of a media.

A
  • Complex media: most common (don’t know exactly all the chemicals in it)
  • Defined media: for specific/sensitive purposes (know everything in it)
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5
Q

What are the 4 different types/functions a growth media can carry out?

A
  • Basal media
  • Enriched media
  • Selective media
  • Indicator/differential media
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6
Q

What is a basal media used for?

A
  • General purpose base media for growing non-fastidious microbes
  • typically complex
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7
Q

What is the purpose of enriched media?

A
  • Allow growth of fastidious microbes

- Starts as basal media then add other things. ie. growth factors

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8
Q

What is a selective media used for?

A
  • Selective agents encourage growth of specific microbes and suppress others
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9
Q

What is the purpose of an indicator media?

A
  • Contain component causing an observable change when microbes grow
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10
Q

Name 4 types of agar.

A
  • Nutrient agar
  • Horse blood agar
  • Chocolate agar
  • MacConkey agar
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11
Q

What is NA made of and what type of bacteria is it suitable for?

A
  • Made of basal media and is for non-fastidious bacteria

- Base medium for other media

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12
Q

What is HBA made of and what is its purpose?

A
  • Made of enriched media and is for fastidious bacteria.

- Indicator for haemolysis which is achieved through using high temp to lyse the blood cells.

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13
Q

What is CHA made of and what is its purpose?

A
  • Made of enriched media and is for very fastidious bacteria.
  • Very high temp lyse blood cells so all contents inside are readily available for bacteria to use.
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14
Q

What is MAC made of and what is its purpose?

A
  • Made of selective media that contains bile salts, lactose and neutral red.
  • The purpose is isolation and enumeration (counting) of coliforms (bacteria in gut) and intestinal bacterial pathogens.
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15
Q

What is the purpose of bile salts in MAC?

A
  • Selective agent for presence of coliform in bacteria.
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16
Q

What is the purpose of neutral red in MAC?

A
  • Turn pink if bacteria are lactose fermenter (produce acidic products).
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17
Q

When is an enrichment media used and how does it achieve its purpose?

A
  • If desired bacterium is only present in low numbers in a MIXED culture use this.
  • Does so by chemically inhibiting other bacteria, nutritionally favouring desired bacteria, manipulating growth environment to suit desired bacterium.
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18
Q

What happens to water activity when external salt concentration is high?

A
  • Water activity is low (chemically and structurally unavailable to bacteria).
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19
Q

What types of microbe cause problems to humans and why?

A
  • Mesophiles because it grows at 37 degrees Celsius.
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20
Q

What are anaerobes?

A
  • Microbes which cannot use oxygen.

- Obligate (strict) anaerobes are killed by oxygen.

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21
Q

What are obligate aerobes?

A
  • Require oxygen
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22
Q

What are facultative anaerobes?

A
  • Can grow without oxygen but grow better with it
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23
Q

What are microaerophiles?

A
  • Need oxygen but at lower then atmospheric concentrations.
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24
Q

Why is it that some microbes cannot grow in oxygen?

A
  • Oxygen can generate reactive oxygen species (ROS) which is toxic.
  • ROS can oxidise sulphydryl group in proteins denaturing enzyme and can damage lipids+nucleic acids
  • Only some bacteria possess enzymes (catalase, peroxidase) and pigments (carotenoids) which detoxify ROS.
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25
Q

Name the 3 types of microbes growing at different pH.

A
  • acidophiles (0-5.8)
  • neutrophiles (5.5-8)
  • alkalophiles (8.5-11.5)
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26
Q

What are biofilms?

A
  • Attached microbes in complex, slime encased communities.

- Mixed microbial community that may possess different characteristics which may benefit others in that community.

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27
Q

What is quorum sensing and how does it work?

A
  • Communication using molecular signals in density-dependent manner.
  • Depending on conc. of molecular signals, it will elicit or not elicit a response in neighbouring cells.
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28
Q

What are the tow types of method of selecting a single cell?

A
  • Streak dilution

- Limiting dilution followed by spread or pour plate

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29
Q

Describe an algae. (4)

A
  • Eukaryote
  • Spherical or filamentous
  • Photosynthesise using chlorophyll and other pigments
  • Fresh water and marine environment.
30
Q

What is a parasite? Give a few examples.

A
  • Any organism which benefits at the cost of the host.

- Caused by bacteria, viruses, fungi and algae, protozoa, helminths, arthropods

31
Q

What are some advantages of parasitism?

A
  • nutrients, protection from environment
32
Q

What are some disadvantages of parasitism?

A
  • immune response (attacks by antibodies, phagocytic cells)
33
Q

What is a definite host and an intermediate host?

A
  • Definite host is the host in which sexual reproduction of the parasite occurs.
  • Intermediate host is the host that serves as a temporary but essential environment for development of a parasite and completion of its life cycle.
34
Q

What is a transmission vector?

A
  • a living organism (usually arthropod or other animal) that transfers an infective agent between hosts.
35
Q

Describe a protozoa.

A
  • Unicellular eukaryote
  • Usually motile
  • Obtains food by ingesting other organisms.organic material (uses vacuoles)
  • Mostly free living but some are human parasites.
36
Q

What are some modes of transmissions in protozoa?

A
  • Through insect (plasmodium spp.)
  • Ingestion of infective stages (toxoplasma gondii)
  • Sexual transmission (STIs)
37
Q

What is are 4 diseases caused by protozoa.

A
  • Malaria caused by plasmodium spp (single celled protozoan parasite.
  • Giardiasis caused by giardia lamblia (a diarrhoeal disease)
  • Helminths can also cause disease
  • Hookworms can cal cause disease
38
Q

What are some symptoms of malaria?

A
  • Acute: fever and anaemia (due to lysis of RBCs), headache, diarrhoea, vomitting
  • Chronic: anaemia, swelling of spleen and liver (working too much to remove abnormal RBCs)
  • Celebral malaria: responsible for almost all deaths (caused only by P.falciparum). Infected RBCs adhere to vascular epithelial cell (so don;t go through spleen to be removed)
39
Q

How is malaria diagnosed?

A
  • Through patient history, symptoms, blood smears (peripheral blood, smears prepared and stained with Giesmsa stain then use light microscopy)
40
Q

What are treatment and prevention options for malaria?

A
  • Anti malarial drugs

- Prevention can include use of chemoprophylaxis (drug), insect repellent, bed nets

41
Q

How does giardiasis spread?

A
  • A water borne disease transmitted through faecal-oral route (ingestion of contaminated water)
42
Q

How does malaria spread?

A
  • Vary in severity: P.falciparum (most malignant infection) and P.knowlesi (rare human nfections)
  • Spread by female mosquitoes genus Anopheles. Goes through two distinctive life cycles (liver and blood).
43
Q

What are some symptoms of giardiasis and when do they show?

A
  • Diarrhoea –> weight loss, dehydration
  • greasy stool, stomach cramps, farting, nausea
  • appears 1-2 weeks after infection
44
Q

What is the life cycle of giardiasis? (4)

A
  • Cyst and trophozoite
  • It has 2 nuclei, 8 flagella and a ventral sucking disc (mechanical sucker) to attach to intestinal wall
  • Lives in intestine and passed in faeces
  • Cyst is dormant and trophozoite die in external environment so must become cyst again
45
Q

What do treatments and prevention include for giardiasis?

A
  • Drinking fluids (metronidazole)

- Good hygiene, avoid contaminated water sources (cyst resistant to chlorine), boil water or filter it

46
Q

What are helminths and what are the 3 main groups?

A
  • Multicellular parasitic worms
  • Tapeworm (cestodes), flukes (trematodes & digenea), roundworms (nematodes- cylindrical bodies, lack specialised attachment organs)
  • Tapeworm and flukes are platyhelminths (flat bodies, muscular suckers/hooks)
47
Q

What is the life cycle of helminths?

A
  • Larval stage and adult stage
48
Q

How are helminths spread?

A
  • Via intermediate host: accidental ingestion of larvae in tissue of another host
  • Faecal-oral route: accidental ingestion of eggs or larvae from faeces of infected host
  • Active skin penetration: larval stage invade skin
  • Injection by blood-sucking insect
49
Q

How are hookworms transmitted?

A
  • Begins and ends in small intestine
  • Eggs hatch in soil and larvae penetrate skin
  • It is carried to the lunch and swallowed so it can reach the small intestine
  • It grows and attaches to intestinal wall and suck blood
  • It produces eggs which are passed in stools
50
Q

What are some symptoms of hookworm disease?

A
  • Rash, itch
  • Light infection: mild diarrhoea and cramps
  • Heavy infection: anaemia, abdominal pain, weight loss, diarrhoea
  • Heavy, chronic infection: stunted growth and mental development
51
Q

What are some treatment and prevention of hookworm disease?

A
  • Treatment by mebendazole, pyrantel

- Prevent by avoiding contact with contaminated soil, improved hygiene and sanitation.

52
Q

Describe a fungi. (6)

A
  • Eukaryote
  • Cell wall of chitin
  • Heterotrophic
  • Saprophytic (breakdown organic material via secreted enzymes and then uptake by absorption-osomotrophic)
  • 7 major fungal group (ending in ..mycota)
  • Divided into moulds (filamentous) and yeasts (unicellular)
53
Q

What are 4 distinct structures in fungi?

A
  • Thallus: body or vegetative structure devoid of root, stem or leaf (single cell in yeasts, multicellular masses in moulds- made of hyphae in moulds)
  • Spores: non-motile, useful for fungal identification
  • Hyphae: vegetative organs that grow when fungal spores germinate (long filaments)
  • Mycelium: tangled mass of hyphae
54
Q

Describe yeast.

A
  • Unicellular fungi that reproduce asexually by budding/fission or sexually by spores
55
Q

Describe mould.

A
  • Usually multi-cellular fungi that reproduce sexually by fusion of hyphae or asexually by despersion of spores.
56
Q

What are some roles good fungi play?

A
  • decomposers, fermenters, producers, research tools
57
Q

What are some roles evil fungi play?

A
  • disease, bio-deterioration, mycotoxins
58
Q

What does Asperigillus Flavus do?

A
  • Fungi that produce mycotoxins.
  • Contaminates food (heat stable aflatoxins are produced and ingested with food which can cause liver disease and cancer)
59
Q

What does Claviceps Purpura do?

A
  • Fungi that produce mycotoxins.
  • Parasitizes rye and other grasses (toxin ingested with grass/grain which can cause Ergot disease, psychotic delusion, abortion)
60
Q

What are 3 ways to identify fungi?

A
  • Macroscopically: colony characteristics, media, colour, texture
  • Microscopically: presence and arrangement of fruiting or sporing bodies (wet mounts, slide culture technique)
  • Biochemically: fermentation products
61
Q

What types of media can be used to grow fungi?

A
  • Sabouraud’s agar (SAB): glucose, peptone, agar, water, ~pH5, +/- antibiotics
  • Malt extract agar (MEA): malt extract, agar, water, ~pH5, +/- antibiotics
  • All in slightly acidic, low moisture conditions
62
Q

What are the 3 types of mycoses?

A
  • Superficial (can be cutaneous: involves epidermis or subcutaneous: involves dermis, muscle and fascia)
  • Systematic: involves major body systems
  • Opportunistic: targets immunocompromised patients (cryptococcosis)
63
Q

What is a fungal infection associated with cutaneous mycoses and how is it diagnosed?

A
  • Tinea and ringworm

- Diagnosed by microscopic examination, cultured on SAB

64
Q

Describe Candidiasis fungal disease. (3)

A
  • Caused by Candida albicans and aerobic fungus
  • Part of normal microbiota of GIT, RT, vaginal area and mouth
  • Can grow as yeast or mould depending on temp
65
Q

How is Candidiasis transmitted and what are some symptoms?

A
  • Spread through STI or can be nosocomial infection (acquired in hospital)
  • Symptoms present in immunocompromised people by disrupting normal microbiota.
66
Q

How is Candidiasis diagnosed and what are the treatment options?

A
  • Diagnosed through symptoms, patient history and culture

- Treatment can be topical, systematic or in general

67
Q

Describe Aspergillosis. (2)

A
  • Caused by Aspergillus sp. an aerobic filamentous fungus.

- Present in soil, dust, some foods and water

68
Q

How is Aspergillosis transmitted and what are some symptoms?

A
  • Spread by inhaling fungal spores, ingestion of contaminated food or water
  • Symptoms include allergic response, ingestion of contaminated food –> alfatoxins, pulmonary infection (A.fumigatus), A.flavus cause superficial and invasive disease (dissemination to brain, kidney, liver)
69
Q

How is Aspergillosis diagnosed and what are some symptoms?

A
  • diagnosed by direct examination of specimen (hyphae or sporing bodies), culture, detection of antigen
  • Treatment includes use of voriconazole or itraconazole
70
Q

Describe Histoplasmosis. (2)

A
  • Cause by Histoplasma capsulatum an intracellular funcgus.

- Found in soil rich in bird/bat droppings (only bats and humans become diseased.

71
Q

How is Histoplasmosis and what are some symptoms?

A
  • Transmitted by inhalation of spores (dimorphic growth)

- Symptoms include 10 days of incubation, fever, cough, muscle aches (infects lung macrophages)

72
Q

What are some treatment and prevention options for Histoplasmosis?

A
  • Treatment include anti-fungal drugs but can resolve on its own.
  • Prevention include wearing protective clothing/mask, soil decontamination.

Microbiology (8 decks)

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