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Biomedicine 1 > Infectious Disease > Flashcards

Infectious Disease Flashcards

1
Q

Infection

A

Infection refers to invasion of a host by a pathogen causing disease

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2
Q

Infection occurrence

A

Infections may occur in:
* Single individuals
* Larger groups = epidemic
* Worldwide = pandemic
* Restricted to an area = endemic

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3
Q

Infections common terms; Vector

A
  • Vector = intermediate carrier, transporting pathogens from reservoir to host
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4
Q

Infection common terms; Reservoir

A
  • Reservoir = location the pathogen exists, reproduces and spreads to new hosts
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5
Q

Infections common terms; Carrier

A
  • Carrier = infected individuals who are asymptomatic
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6
Q

Infections common terms; Host

A
  • Host = an infected person or animal
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7
Q

Infection transmission

A

Any communicable disease, transmitted from;
* Human to human
* Animal to human
Transmitted by;
* Direct contact, e.g. hand-to-hand touching
* Indirect contact, e.g. hand to a surface to a person

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8
Q

Infection transmission pathways

A

Infection can be transmitted by:
* Droplet transmission, e.g. coughing with flu, scarlet fever
* Direct contact, e.g. via faeces
* Indirect contact, e.g. via food, transport
* Vectors: carried by an insect or animal
* Nosocomial: acquired from a medical setting (hospital or care facility); e.g. surgical site, UTIs, pneumonia, ulcers

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9
Q

Infection;
acquired by

A

Infection may be acquired by”
* Ingestion = ingest microbes / faeces, larva eggs. Etc.
* Direct to blood stream = injection, open wounds, bites
* Sexual intercourse
* Inhalation
* Touch
* Placental

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10
Q

Infection stages

A

There are four infection stages:
1. Incubation period
2. Prodroma period
3. Acute period
4. Chronic infection

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11
Q

Infection stages; incubation period

A

Time interval between initial exposure to the infecting organism and the appearance of the first signs or symptoms it produces

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12
Q

Infection stages; Prodromal period

A

Interval from non-specific symptoms (malaise, fever, fatigue) to more specific acute symptoms

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13
Q

Infection stages; Acute period

A

The pathogen peaks in population.
Associated with very pronounced symptoms specific to the disease

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14
Q

Infection stages; Chronic infection

A

Infection with insidious or slow onset of long duration

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15
Q

Infectious agents

A

Disease may be caused by;
1. Micro-organisms (microbes)
* Bacteria
* Viruses
* Fungi
* Protozoa

  1. Multi-cellular organisms
    Protozoa = single-celled organsisms
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16
Q

Microorganisms – Non pathogenic

A

Microorganisms are either non-pathogenic or pathogenic
1. Non-pathogenic:
* Not disease-causing
* Many microbes are ‘symbiotic’ (live together).
However these can become pathogenic
* Commensal bacteria live on our skin and mutualistic bacteria in our intestines
* There are around 10 times as many bacterial cells as human cells in the body

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17
Q

Microorganisms - Pathogenic

A

Microorganisms are either non-pathogenic or pathogenic
2. Pathogenic:
* Disease-causing microbes (i.e. ‘pathogens’)
Patho = suffering

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18
Q

Microbe relationships; commensal

A

A symbiotic relationship between organisms whereby one benefits and the other is unaffected; e.g. microbes on your skin, candida

Symbiotic = relationship between organisms

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19
Q

Microbe relationships; mutualistic

A

A symbiotic relationship between organisms, whereby both benefit; e.g. E.coli make vitamin K for humans

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20
Q

Microbe relationships; parasitic

A

A symbiotic relationship between organisms whereby one benefits at the other’s expsense; e.g. head lice

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21
Q

Microbe relationships; opportunistic

A

A symbiotic relationship between organisms which is initially commensal / mutualistic then becomes parasitic; e.g. candida

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22
Q

Microbe history

A
  1. Anton van Leewenhoek (1670’s):
    Invesnted the microscope – documented microbes
  2. Dr Ignaz Philipp Semmelweis (1847):
    Washing hands reduces disease spread in hospitals
  3. Louis Pasteur v. Antoine Bechamp (1860s):
    Pasteur; ‘germ theory of disease’ – he said “germs are all bad and cause disease”. Developed pasteurization
    Bechamp; “Germs are ‘opportunistic’ in nature and live with us symbiotically”. He proposed the ‘terrain theory’. To prevent illness, he advocated not to kill germs but to promote health (i.e. through diet, exercise)
  4. Alexander Fleming (1900s):
    Founder of antibiotics incidentally in his lab – penicillin
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23
Q

Identifying microbes

A

Microbes are identified and characterisd so the causative agent of a disease can be identified. This allows for appropriate treatment and applying appropriate infection controls to inhibit disease spread.

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24
Q

Bacteria cell structure

A

Bacteria are prokaryotic cells. This means the cell structure is simple and has no nucleus or membrane –bound organelles.
The ‘control centre’ of bacteria is a single loop of DNA

25
Q

Bacteria; classification – shape

A

Bacteria have three different shapes:
* Bacilli: Rod-shaped, e.g. e.coli
* Cocci: Spherical, e.g. streptococci, staphylococci
* Spirochetes: spiral shapes e.g. syphilis, borrelia

26
Q

Bacteria; classification – cell wall

A

Bacteria have two types of cell wall:
* Gram-positive; thick mesh like cell wall made of peptideoglycan (made of protein and carbohydrates). Stains purple with Gram’s method.
* Gram-negative; thinner cell wall layer (made up of lipopolysacchardides (LPS) (made of fat and carbohydrate), with an additional outer lipid-rich membrane. Stains pink with Gram’s method. (When gram-negative bacteria die they release LPS from the cell wall, which can cause harmful effects that bacteria can produce).

27
Q

Bacterial growth

A

Reproduction is asexual by ‘binary fission’.
This type of cell division is rapid. For example E.coli can divide in as little as 20 mins. Binary fission enables bacteria to reproduce in high numbers at a rapid rate. This enhances the ability of the bacteria to cause disease
‘Spore’ formation – a structure that is extremely resistant to hostile physical and chemical conditions such as heat and disinfectants
Spores also form part of the lifecycle of many fungi and protozoan’s. Spores are a dormant life form.

28
Q

Bacterial Toxins and Enzymes; Exotoxins

A

Exotoxins:
* Gram-positive and negative bacteria
* Released by a living microbe
* Very toxic, protein toxins
* Have a variety of effects on bodily functions
* Example; Dipheria (inhibits protein synthesis), E.coli, C.Tetani

29
Q

Bacterial Toxins and Enzymes; Endotoxins

A

Endotoxins:
* Gram-negative bacteria only (LPS)
* Released after organism death from cell wall
* Often cause fever / malaise (signs and symptoms of infection)
* Stimulate inflammatory cascade
* Usually less toxic
* Example; Salmonella

30
Q

Bacterial Toxins and Enzymes; Invasive Enzymes

A

Some bacteria produce enzymes to help them invade a host; e.g. haemolytic streptococci produce enzymes that break down RBCs

31
Q

Resident and transient microflora - inc where it is and is not

A

The ‘microflora’ encompasses naturally occurring micro-organisms inhabiting the healthy human body – mostly bacteria:
* Present; Nasal cavity, skin, mouth, small and large intestine, vagina and perineum
* Absent; Blood, cerebrospinal fluid (CFS), lungs, stomach, uterus, fallopian tubes, ovaries, bladder and kidneys
Organisms within the microflora can become pathogenic if the local environment changes of if the immune system becomes compromised (‘opportunistic’)

32
Q

Antibiotics

A
  • Conventional drugs that destroy bacteria
  • Can be broadly categorized as being either broad or narrow spectrum. Broad spectrum antibiotics possess no specificity for the bacteria they kill and instead can have devastating effects on the body’s microflora
  • Are often overprescribed. This accompanied by the presence of antibiotics in some foods, has led to more adverse effects and antibiotic resistance
  • Is also linked to a higher risk of diseases including asthma and IBD.
  • Do not work against viruses; e.g. cold, flu, cold sores
  • Other adverse effects include; impaired immunity, Candida (yeast) overgrowth (due to loss of friendly flora), diarrhoea
33
Q

Viruses

A

Are obligate intracellular parasites – needing a living host for survival and replication
* They are not cells but rather consist of a strand of RNA or DNA in a hard protein coat – ‘capsid’. Protein coat is unique for each virus
* Smallest microbes – too small to be seen with light microscopy.
* Infect only certain cells–express specificity due to surface viral proteins
* When a virus binds with a cell, it only allows entry of genetic material and the capsid remains outside
* A virus will generally burst its host cell as it leaves

34
Q

Viruses;
DNA and RNA

A
  • DNA viruses (mostly double stranded) inc. varicella zoster, herpes, smallpox
  • RNA viruses inc. measles, mumps, HIV
  • They reproduce by injecting their RNA or DNA strand into a living host cell and use the host cell’s apparatus for reproduction
35
Q

Virus structure –immune system evading

A

Viruses are more difficult both for the body and for anti-viral agents and drugs to identify and destroy. This is because;
1. They hide inside the host cells (can be latent)
2. They do not have a metabolism of their own – hence anti-microbial agents cannot be targeted towards enzymes
3. They do not have many structures of their own
4. Able to mutate – this allows them to change their surface antigens and avoid host immune response

36
Q

Viral replication - 3 types

A
  • Viral lysis: viral particles burst cell out of the host cell into the extracellular space, resulting in the death of the host cell
  • Viral budding: process by which a virus exits a cell and acquires an envelope (outer membrane) of its own from the host cell membrane and usually leads to cell death. Used in viruses which need an envelope; e.g. HIV
  • Latent stage: Stage of infection where the disease is present but hidden and inactive. Viruses can remain in a latent stage for years and become reactivated; e.g. herpes simplex
37
Q

Fungi

A

Eukaryotic organisms
* Can be single-celled or very complex multicellular organisms
* Have a cell wall that contain melanin
* Are found everywhere; e.g. soil, mouldy bread, medicine, food
* Filaments of fungi are called ‘hyphae’
* A mass of fungi is a ‘mycelium’
* We are generally resistant to fungal infections. Fungal infections are often opportunistic and occur in immune compromised patients (e.g. HIV, diabetes mellitus)

38
Q

Fungi Mycosis (infections) - fungi types

A

Usually result from 3 forms of fungi:
1. Yeasts; Single-celled fungus that reproduces by budding; e.g. candida albicans
2. Moulds; Multi-cellular fungi. Some moulds cause disease, others are involved in production of various foods and antibiotics; e.g. aspergillus and penicillium
3. Dermatophytes; Fungi causing skin disease. They obtain nutrients from keratin in ksin (no living tissue is invaded) and colonise in the stratum corneum. It’s the only fungus dependant on humans; e.g. ringworm or tinea.

39
Q

Fungi growth and reproduction

A
  1. Growth results in formation of:
    * Hyphae: Fungal filaments
    * Mycelium: A ‘mesh’ of intertwined filaments
    * Grwoth is promoted by warmth, moisture, rich nutrition, acidity
  2. Reproduction occurs via:
    * Asexual reproduction occurs via budding (extension of the hyphae) containing chromatin that eventually detach and develop into an independent organism
    * Sexual reproduction is less common and occurs by forming fungal spores
40
Q

Protozoa

A

Eukaryotic organisms
* Exists as single cells and have no cell wall, just a membrane
* Live in moist environments such as fresh water, soils and in the ocean
* Can move in various easy. E.g. flagella, cilia or vector

41
Q

Protozoa; Reproduction

A

Occurs via:
* Binary fission and budding
* Sexual reproduction (only in unfavourable conditions)
* Can form cysts – can survive harsh conditions

42
Q

Helminths

A

Parasitic worms.
* Eukaryotic and macroscopic organisms
* Multi-cellular
* Lifecycles: egg, larva, adult
* Can live in intestines, blood or tissue; i.e. intestinal epithelium
* Include roundworm, tapeworm, pinworms
* Many helminths are intestinal parasites

43
Q

Host Resistance v Microbial Virulence - Host resistance

A

Host Resistance:
* Intact skin and mucous membranes
* Body secretions - stomach acid, tears etc.
* Phagocytosis
* Interferon production
* Effective inflammatory response
* Effective immune system

44
Q

Host Resistance v Microbial Virulence - Microbial virulence

A

Microbial Virulence:
* Production of invasive / destructive enzymes
* Production of endo- or exo-toxins
* Spore formation
* Entry of large number of organsisms; form colonies (CFUs)
* Presence of bacterial capulse and pili
* Ability to mutate, e.g. MRSA, HIV

45
Q

Infection control

A

It is important to prevent the spread of infections, especially for healthcare professionals
Ways to reduce spread inc;
* Reduce the reservoir
* Stop droplet transmission – covering the mouth (not with the hand)
* Black the method of transmission (hand washing, gloves, condoms)
* Kill the organism
* Sterilisation

46
Q

Infection control; Sterilisation

A

Sterilisation: All micro-organsims and their spores are destroyed;
Hot air; 30 mins at 180’C
Autoclaving (steam); 20 mins at 120’C

47
Q

Infection control; Disinfectants

A

Disinfectants: Destroy pathogenic microbes, but usually not their spores

48
Q

Infection control; Antiseptics

A

Reduce the number of organisms on the skin, but not their spores e.g. alcohol

49
Q

Infection control; Pasteurisation

A

Pasteurisation; 71.7’C for 15-25 seconds – will kill most pathogenic microbes but not their spores

50
Q

Infection control; Natural options

A

Natural options; Tea tree oil, Eucalyptus oil, Neem oil, Calendula & colloidal silver but are not medically recommended anti-microbial agents

51
Q

Infectious Pathologies; Local signs

A

Local signs:
* Pain:
* Swelling
* Redness
* Warmth
* Purulent exudate (bacterial)

52
Q

Infectious Pathologies; Systemic symptoms

A

Systemic Symptoms:
* Fever (+ possibly chills)
* Fatigue and weakness
* Headache
* Nausea

53
Q

Infectious Pathologies; Sepsis (complication)

A

Sepsis (septicaemia) can be a complication of infection. It occurs when the pathogen has infected the blood. It arises when the bodies response to the infection causes injury to the body’s own organs, potentially leading to multi-organ failure.
Higher risk in elderly (>75) or very young (<1), alcoholics, diabetes, chemotherapy patients.
Symptoms include lethargy, nausea, vomiting, abdominal pain, diarrhoea, coughing, etc.

54
Q

Diagnostic testing;

A
  1. Culture / Staining:
    * Identification of micro organisms
    * If required; drug sensitivity test
  2. Blood tests:
    * Bacterial infection: Often Leukocytosis
    * Viral infection: often leucopenia
    * High ‘erythrocyte sedimentation rate’ (ESR)
  3. Stool tests:
  4. Radiography:
    * E.g. tuberculosis
55
Q

Extra Information: Natural Antimicrobials- Anti-bacterials

A
  • Garlic
  • Goldenseal
  • Oregano
  • Grapefruit seed extract
  • Myrrh and tea tree
  • Thyme and calendula
  • Colloidal silver
56
Q

Extra Information: Natural Antimicrobials - Anti-virals

A
  • Elderberry (colds and flu)
  • Olive leaf
  • St John’s Wort and Pau D’Arco
  • Lemon Balm (Herpes simplex)
57
Q

Extra Information: Natural Antimicrobials - Anti-fungals

A
  • Garlic
  • Oregano
  • Caprylic acid
  • Cinnamon
  • Berberine
58
Q

Extra Information: Natural Antimicrobials - Anti-parasitics

A
  • Garlic
  • Black walnut
  • Wormwood
  • Berberine
  • Goldenseal
  • Oregano

Biomedicine 1 (39 decks)

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