Week 2 Flashcards
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.
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.
3
Q
What are buffering agents?
A
Can use soluble phosphate to absorb change in pH produced by bacteria.
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)
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
6
Q
What is a basal media used for?
A
- General purpose base media for growing non-fastidious microbes
- typically complex
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
8
Q
What is a selective media used for?
A
- Selective agents encourage growth of specific microbes and suppress others
9
Q
What is the purpose of an indicator media?
A
- Contain component causing an observable change when microbes grow
10
Q
Name 4 types of agar.
A
- Nutrient agar
- Horse blood agar
- Chocolate agar
- MacConkey agar
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
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.
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.
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.
15
Q
What is the purpose of bile salts in MAC?
A
- Selective agent for presence of coliform in bacteria.
16
Q
What is the purpose of neutral red in MAC?
A
- Turn pink if bacteria are lactose fermenter (produce acidic products).
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.
18
Q
What happens to water activity when external salt concentration is high?
A
- Water activity is low (chemically and structurally unavailable to bacteria).
19
Q
What types of microbe cause problems to humans and why?
A
- Mesophiles because it grows at 37 degrees Celsius.
20
Q
What are anaerobes?
A
- Microbes which cannot use oxygen.
- Obligate (strict) anaerobes are killed by oxygen.
21
Q
What are obligate aerobes?
A
- Require oxygen
22
Q
What are facultative anaerobes?
A
- Can grow without oxygen but grow better with it
23
Q
What are microaerophiles?
A
- Need oxygen but at lower then atmospheric concentrations.
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.
25
Name the 3 types of microbes growing at different pH.
- acidophiles (0-5.8)
- neutrophiles (5.5-8)
- alkalophiles (8.5-11.5)
26
What are biofilms?
- Attached microbes in complex, slime encased communities.
| - Mixed microbial community that may possess different characteristics which may benefit others in that community.
27
What is quorum sensing and how does it work?
- 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.
28
What are the tow types of method of selecting a single cell?
- Streak dilution
| - Limiting dilution followed by spread or pour plate
29
Describe an algae. (4)
- Eukaryote
- Spherical or filamentous
- Photosynthesise using chlorophyll and other pigments
- Fresh water and marine environment.
30
What is a parasite? Give a few examples.
- Any organism which benefits at the cost of the host.
| - Caused by bacteria, viruses, fungi and algae, protozoa, helminths, arthropods
31
What are some advantages of parasitism?
- nutrients, protection from environment
32
What are some disadvantages of parasitism?
- immune response (attacks by antibodies, phagocytic cells)
33
What is a definite host and an intermediate host?
- 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
What is a transmission vector?
- a living organism (usually arthropod or other animal) that transfers an infective agent between hosts.
35
Describe a protozoa.
- Unicellular eukaryote
- Usually motile
- Obtains food by ingesting other organisms.organic material (uses vacuoles)
- Mostly free living but some are human parasites.
36
What are some modes of transmissions in protozoa?
- Through insect (plasmodium spp.)
- Ingestion of infective stages (toxoplasma gondii)
- Sexual transmission (STIs)
37
What is are 4 diseases caused by protozoa.
- 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
What are some symptoms of malaria?
- 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
How is malaria diagnosed?
- Through patient history, symptoms, blood smears (peripheral blood, smears prepared and stained with Giesmsa stain then use light microscopy)
40
What are treatment and prevention options for malaria?
- Anti malarial drugs
| - Prevention can include use of chemoprophylaxis (drug), insect repellent, bed nets
41
How does giardiasis spread?
- A water borne disease transmitted through faecal-oral route (ingestion of contaminated water)
42
How does malaria spread?
- 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
What are some symptoms of giardiasis and when do they show?
- Diarrhoea --> weight loss, dehydration
- greasy stool, stomach cramps, farting, nausea
- appears 1-2 weeks after infection
44
What is the life cycle of giardiasis? (4)
- 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
What do treatments and prevention include for giardiasis?
- Drinking fluids (metronidazole)
| - Good hygiene, avoid contaminated water sources (cyst resistant to chlorine), boil water or filter it
46
What are helminths and what are the 3 main groups?
- 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
What is the life cycle of helminths?
- Larval stage and adult stage
48
How are helminths spread?
- 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
How are hookworms transmitted?
- 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
What are some symptoms of hookworm disease?
- 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
What are some treatment and prevention of hookworm disease?
- Treatment by mebendazole, pyrantel
| - Prevent by avoiding contact with contaminated soil, improved hygiene and sanitation.
52
Describe a fungi. (6)
- 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
What are 4 distinct structures in fungi?
- 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
Describe yeast.
- Unicellular fungi that reproduce asexually by budding/fission or sexually by spores
55
Describe mould.
- Usually multi-cellular fungi that reproduce sexually by fusion of hyphae or asexually by despersion of spores.
56
What are some roles good fungi play?
- decomposers, fermenters, producers, research tools
57
What are some roles evil fungi play?
- disease, bio-deterioration, mycotoxins
58
What does Asperigillus Flavus do?
- Fungi that produce mycotoxins.
- Contaminates food (heat stable aflatoxins are produced and ingested with food which can cause liver disease and cancer)
59
What does Claviceps Purpura do?
- Fungi that produce mycotoxins.
- Parasitizes rye and other grasses (toxin ingested with grass/grain which can cause Ergot disease, psychotic delusion, abortion)
60
What are 3 ways to identify fungi?
- Macroscopically: colony characteristics, media, colour, texture
- Microscopically: presence and arrangement of fruiting or sporing bodies (wet mounts, slide culture technique)
- Biochemically: fermentation products
61
What types of media can be used to grow fungi?
- 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
What are the 3 types of mycoses?
- Superficial (can be cutaneous: involves epidermis or subcutaneous: involves dermis, muscle and fascia)
- Systematic: involves major body systems
- Opportunistic: targets immunocompromised patients (cryptococcosis)
63
What is a fungal infection associated with cutaneous mycoses and how is it diagnosed?
- Tinea and ringworm
| - Diagnosed by microscopic examination, cultured on SAB
64
Describe Candidiasis fungal disease. (3)
- 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
How is Candidiasis transmitted and what are some symptoms?
- Spread through STI or can be nosocomial infection (acquired in hospital)
- Symptoms present in immunocompromised people by disrupting normal microbiota.
66
How is Candidiasis diagnosed and what are the treatment options?
- Diagnosed through symptoms, patient history and culture
| - Treatment can be topical, systematic or in general
67
Describe Aspergillosis. (2)
- Caused by Aspergillus sp. an aerobic filamentous fungus.
| - Present in soil, dust, some foods and water
68
How is Aspergillosis transmitted and what are some symptoms?
- 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
How is Aspergillosis diagnosed and what are some symptoms?
- diagnosed by direct examination of specimen (hyphae or sporing bodies), culture, detection of antigen
- Treatment includes use of voriconazole or itraconazole
70
Describe Histoplasmosis. (2)
- Cause by Histoplasma capsulatum an intracellular funcgus.
| - Found in soil rich in bird/bat droppings (only bats and humans become diseased.
71
How is Histoplasmosis and what are some symptoms?
- Transmitted by inhalation of spores (dimorphic growth)
| - Symptoms include 10 days of incubation, fever, cough, muscle aches (infects lung macrophages)
72
What are some treatment and prevention options for Histoplasmosis?
- Treatment include anti-fungal drugs but can resolve on its own.
- Prevention include wearing protective clothing/mask, soil decontamination.
