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DS1101 - S1 Y1 > Week 8 - Microbes and Disease > Flashcards

Week 8 - Microbes and Disease Flashcards

1
Q

What are the stages of the infectious process/cycle

A
  1. Infectious agent e.g. virus, bacteria, parasite, fungi
  2. reservoir e.g. water, food, soil, humans, animals
  3. Portal of exit e.g. body fluids, blood, coughing/sneezing
  4. Mode of transmission e.g. droplet, faecal-oral, vector-borne
  5. Portal of entry e.g. mouth, nose, skin cuts, eyes
  6. Susceptible Host e.g. human being
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2
Q

What is infectious agent in the stages of the infectious process

A

Microorganism which is able to cause disease

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3
Q

What is reservoir of infection in the stages of the infectious process

A

Place where organism can live and reproduce, and where it can spread to cause disease

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4
Q

What are examples of reservoirs of infection

A
  • body tissues
  • waste of humans, animals, insects
  • contaminated food, water or soil
  • other animals (zoonoses)
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5
Q

What is Portal of entry/exist in the stages of the infectious process

A

Ways of achieving transmission (usually portal of entry and exist are the same)

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6
Q

What are examples of portals of entry

A

Skin

  • breaches
  • Active invasion of mucous membranes

Respiratory Tract

  • inhaled as aerosols (sneeze), spores, on dust
  • Bacteria (streptocuccus, TB) viruses (rhinoviruses, influenza), fungi (Aspergillus, Crytocuccus)

Urogential tract

  • gonorrhea, syphilis, HPV (genital warts), herpes (mostly HSV-2), Hep B and C, AIDS
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7
Q

Example of portals of exists

A

Skin

Crusts, scabs of wounds, exudates from lesions, boils, pustular rashes

  • this spreads by direct contact with exudate or shed into the environment where they can be spread by air currents or contaminate a fomite

Respiratory tract

Mucosal secretions and sputum

  • this is spread by sneezing or coughing

Blood

  • This is spread by sharing needles, breaks in the skin or mucous membrane, needlesticks injuries, dental and medical procedures when there is bleeding
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8
Q

What are modes of transmission in the stages of the infectious process

A

the means by which the infectious agent is transferred from the reservoir to a susceptible host. There are several modes of transmission:
- direct transmission
- indirect transmission
- airborne

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9
Q

What are the steps microorganism need to cause disease

A
  1. Gain entry to host
  2. Attach and multiply
  3. Evade host defenses
  4. Cause damage to tissue
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10
Q

Explain gain entry to a host as a step for microorganism to cause disease

A

Reservoir of infection, mode of transmission, portal of entry
The microorganism needs access to a host to cause damage

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11
Q

Explain attach and multiply as a step for microorganism to cause disease

A

Microorganisms must be able to adhere to host cells or tissues to initiate infection

Bacteria use - adhesins on fimbriae

Viruses use - capsid or envelope proteins

Fungi and protozoa use - surface proteins

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12
Q

Explain evade host defenses as a step for microorganisms to cause disease

A

evasion can prevent elimination before reproduction and or transmission to another host
can occur through:
- disguising themselves from recognition by the immune system,
- suppressing immune cell function,
- directly attacking immune cells with toxins or other virulence factors.

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13
Q

What is pathogenicity

A

ability of a microorganism to produce disease in a host organism

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14
Q

What is pathogenesis

A

mechanism by which disease is produced (how the disease is produced)
e.g. destruction of tissues, production of virulence factors, toxins, proteases, immunopathology

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15
Q

What is the dynamic relationship between host and pathogen dependent upon

A
  • resistance
  • virulence
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16
Q

What is resistance

A

Ability of body to defend against the specific microorganism

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17
Q

What is virulence

A

Relative ability of microorganism to cause disease
Influenced by:
- Properties of microorganisms that allows it to establish and cause disease
- Resistance, (potential drug/vaccine targets)

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18
Q

What properties of bacteria allows it to establish and cause disease

A

adhesins, exotoxins, neurotoxins, endotoxin

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19
Q

What properties of viruses allows it to establish and cause disease

A
  • any molecule that allows invasion of host cell
  • completion of life cycle
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20
Q

What properties of fungal allows it to establish and cause disease

A

molecules that allow attachment or evasion of host defenses

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21
Q

What does communicable mean

A

capacity for a microorganism to move from one host to another

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22
Q

What does contagious mean

A

the degree to which a disease is communicable

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23
Q

What does R0

A

the number of people infected by one contagious person

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24
Q

What does non-communicable mean

A

not infectious and not transmissible to another host e.g. diabetes, heart disease

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25
Q

What is susceptible host in the stages of the infectious process

A

There must be a susceptible host capable of being infected by the infectious agent. Factors that contribute to susceptibility include the host’s immune status, age, overall health, and genetic factors.

26
Q

What are some preventions to control the infectious cycle/process

A
  • hand hygiene sterilization
  • hand hygiene gloves
  • immunization
27
Q

What is colonisation

A

Microorganisms living in a mutual relationship eg. microbiota

28
Q

What is infection

A

Invasion and multiplication of pathogenic microorganisms (parasitic relationship)

29
Q

What is disease

A

Harmful alteration to the physiological or metabolic state of the host
they have signs and symptoms

30
Q

What are signs

A

measurable changes in the patient (one which the doctor discovers)
e.g. high temperature, skin changes, increase in WBC counts

31
Q

What are symptoms

A

changes that are felt and reported by the patient
e.g. pain, headache, nauseam malaise

32
Q

What are characteristics of bacteria infections

A

localized inflammation, pus
e.g. dental abscess

33
Q

What are characteristics of viral infections

A

tend to be systemic but some are local
e.g. herpes

34
Q

What are characteristics of fungal infections

A

mycoses
often skin conditions but can go deeper e.g. thrush

35
Q

What are stages in progression of disease

A
  1. Incubation period
  2. Prodromal period
  3. illness
  4. decline
  5. convalescence
36
Q

What is the incubation period

A

no signs or symptoms
- This stage begins after the infectious agent has entered the body but before symptoms appear.
- During this period, the pathogen is replicating and spreading within the host, but the host does not yet exhibit signs or symptoms of the disease.
- The duration of the incubation period can vary widely depending on factors such as the type of pathogen, the route of transmission, and the individual’s immune response.

37
Q

What is the prodromal period

A

vague, general symptoms
- In this stage, the initial symptoms of the disease begin to appear.
- These symptoms are often nonspecific and may include fatigue, malaise, mild fever, headache, and muscle aches.
- The prodromal stage serves as an early warning sign that the body is mounting an immune response against the infection.
- During this stage, the infectious agent continues to multiply, and the host’s immune system begins to recognize and respond to the pathogen.

38
Q

what is illness in the progression of disease

A

most severe signs and symptoms
- the full development of the disease’s characteristic signs and symptoms.
- The infection reaches its peak intensity during this stage, and the host experiences the most severe manifestations of the illness.
- The specific symptoms depend on the nature of the disease but may include high fever, inflammation, tissue damage, organ dysfunction, and other clinical manifestations associated with the infection.
- This stage is typically the period during which the individual seeks medical attention and receives treatment for the disease.

39
Q

what is decline in the progression of disease

A

declining signs and symptoms
- symptoms gradually improve, and the body begins to repair and recover from the effects of the infection.
- The duration varies depending on the severity of the illness, the effectiveness of treatment, and individual factors such as overall health and immune function.

40
Q

What is convalescent in the progression of disease

A

No signs or symptoms

41
Q

What are the types of infection

A
  • acute
  • chronic
  • latent
  • localised infections
  • systemic infections
  • focal (disseminated) infections
42
Q

What is an acute infection

A

an illness which develops quickly and is last a relatively short duration. These infections can range from mild, self limiting illnesses to severe and life threatening conditions

e.g. Food poisoning, common cold

43
Q

What is a chronic infection

A

An illness which may persist in the body for an extended period and can lead to long term complications and may require ongoing management and treatment to control symptoms and prevent disease progression

e.g. Mycoses, TB, HBV

44
Q

What is a latent infection

A

When the infectious agent remains dormant or inactive within the host for an extended period after the initial infection. Latent infections can be reactivated later in life, leading to recurrence of symptoms and diseases.

e.g. HSV-1, HSV-2, Varicella zoster, EBV, cytomegalovirus

45
Q

What is a localized infection

A

Infections which are confined to a specific area or organ within the body. Symptoms are often localized too.

e.g. skin infections

46
Q

What is a systemic infection

A

Also known as generalized infections, which involve multiple organs or systems within the body. They normally spread through the bloodstream or lymphatic system.

e.g. typhoid, measles, clostridium tetani toxin

47
Q

What is a focal (disseminated) infection

A

Localized infections that have the potential to spread and cause secondary infections or complications in distant parts of the body. The primary focus of infection serves as a reservoir from which the pathogen can spread to other sites.

e.g. streptococcus and endocarditis

48
Q

What are endogenous infections

A

Infections which are host derived - the source of infection is from inside the host
e.g. shift in microorganism

49
Q

Examples of endogenous infections

A
  • surgical wound infections - Staphylococcus epidermidis
  • oral streptococci - infective endocarditis
  • Overgrowth of Candida albicans - oral thrush
50
Q

What are exogenous infections

A

Infection caused by an outside source

51
Q

Example of exogenous infections

A
  • herpes implex virus
  • Hepatitis B
  • HIV
  • Measles
52
Q

What are the 3 main factors in an infectious disease

A
  • Microorganism able to cause disease
  • host susceptible to infection
  • suitable environment for survival and transmission
53
Q

What is HVB - Hepatitis B Virus

A
  • An enveloped DNA virus
  • Transmitted by direct contact with blood or bodily fluids
  • The skin or mucous membrane is the portal of entry
  • An infected person is the reservoir of infection
  • Causes inflammation of the live and can develop into cirrhosis or liver cancer

Acute Infection

  • incubation time 2-3 months, lasts 6 weeks-6 months

Chronic infection

  • 6 months with HBV surface antigen detectable
  • Still infectious at this stage
54
Q

What are body fluids with low/not detectable concentration of HBV

A
  • urine
  • faeces
  • sweat
  • tears
  • breast milk
55
Q

What are body fluids with moderate concentration of HBV

A
  • semen
  • vaginal fluid
  • saliva
56
Q

What are body fluids with a high concentration of HBV

A
  • blood
  • serum (liquid part of blood)
  • Wound exudates
  • GCF (gingivitis)
57
Q

What is HIV - Human Immunodeficiency Virus

A

HIV weakens the immune system over time, making the infected individual more susceptible to opportunistic infections and certain types of cancers.

  • An enveloped single strand RNA retrovirus
  • Transmitted in body fluids
  • Skin, mucous membrane is the portal of entry
  • an infected person is the reservoir of infection
  • HIV destroys the CD4+ (T-helper) cells which weakens the immune system and promotes opportunistic pathogens

Acute Infection

2-4 weeks

Chronic or latent

> 10 years

58
Q

What is Pseudomonas Aeruginosa

A

Pseudomonas aeruginosa is a versatile and opportunistic Gram-negative bacterium that can cause a wide range of infections, particularly in individuals with weakened immune systems or underlying health conditions

  • gram negative bacillus
  • Opportunistic pathogen

Reservoir of infection = water and soil and waterlines

Portal of entry = mouth

  • multi-drug resistant as it has:

-intrinsic efflux pumps

-horizontal gene transfer

-located in biofilm which has extracellular polysaccharide slim layer which is hard for drugs to penetrate

59
Q

What is Impetigo

A

Impetigo is a contagious bacterial skin infection that primarily affects infants and young children, though it can occur in individuals of any age. It is characterized by the formation of red sores or blisters on the skin, particularly around the face, mouth, and hands. Impetigo is usually caused by either Staphylococcus aureus or Streptococcus pyogenes bacteria, or sometimes both.

  • endogenous or exogenous contagious infection (staph.aureus, strep.pyogenes)

reservoir = infected people

Mode of transmission

  • Direct contact with sore or nasal discharge
  • opportunistic

Portal of entry/exit = skin which is non-intact or intact

60
Q

What is infective endocarditis

A

Infective endocarditis is a serious infection of the endocardium, which is the inner lining of the heart chambers and heart valves. It is typically caused by bacteria or less commonly by fungi or other microorganisms. Infective endocarditis can lead to damage of the heart valves and surrounding tissues, as well as systemic complications if not treated promptly.

DS1101 - S1 Y1 (49 decks)

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