Week 8 - Microbes and Disease Flashcards
What are the stages of the infectious process/cycle
- Infectious agent e.g. virus, bacteria, parasite, fungi
- reservoir e.g. water, food, soil, humans, animals
- Portal of exit e.g. body fluids, blood, coughing/sneezing
- Mode of transmission e.g. droplet, faecal-oral, vector-borne
- Portal of entry e.g. mouth, nose, skin cuts, eyes
- Susceptible Host e.g. human being
What is infectious agent in the stages of the infectious process
Microorganism which is able to cause disease
What is reservoir of infection in the stages of the infectious process
Place where organism can live and reproduce, and where it can spread to cause disease
What are examples of reservoirs of infection
- body tissues
- waste of humans, animals, insects
- contaminated food, water or soil
- other animals (zoonoses)
What is Portal of entry/exist in the stages of the infectious process
Ways of achieving transmission (usually portal of entry and exist are the same)
What are examples of portals of entry
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
Example of portals of exists
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
What are modes of transmission in the stages of the infectious process
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
What are the steps microorganism need to cause disease
- Gain entry to host
- Attach and multiply
- Evade host defenses
- Cause damage to tissue
Explain gain entry to a host as a step for microorganism to cause disease
Reservoir of infection, mode of transmission, portal of entry
The microorganism needs access to a host to cause damage
Explain attach and multiply as a step for microorganism to cause disease
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
Explain evade host defenses as a step for microorganisms to cause disease
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.
What is pathogenicity
ability of a microorganism to produce disease in a host organism
What is pathogenesis
mechanism by which disease is produced (how the disease is produced)
e.g. destruction of tissues, production of virulence factors, toxins, proteases, immunopathology
What is the dynamic relationship between host and pathogen dependent upon
- resistance
- virulence
What is resistance
Ability of body to defend against the specific microorganism
What is virulence
- things which assist bacteria in causing disease e.g. toxins, surface receptors that bind to host cells, capsules
What properties of bacteria allows it to establish and cause disease
adhesins, exotoxins, neurotoxins, endotoxin
What properties of viruses allows it to establish and cause disease
- any molecule that allows invasion of host cell
- completion of life cycle
What properties of fungal allows it to establish and cause disease
molecules that allow attachment or evasion of host defenses
What does communicable mean
capacity for a microorganism to move from one host to another
What does contagious mean
the degree to which a disease is communicable
What does R0
the number of people infected by one contagious person
What does non-communicable mean
not infectious and not transmissible to another host e.g. diabetes, heart disease
What is susceptible host in the stages of the infectious process
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.
What are some preventions to control the infectious cycle/process
- hand hygiene sterilization
- hand hygiene gloves
- immunization
What is colonisation
Microorganisms living in a mutual relationship eg. microbiota
What is infection
Invasion and multiplication of pathogenic microorganisms (parasitic relationship)
What is disease
Harmful alteration to the physiological or metabolic state of the host
they have signs and symptoms
What are signs
measurable changes in the patient (one which the doctor discovers)
e.g. high temperature, skin changes, increase in WBC counts
What are symptoms
changes that are felt and reported by the patient
e.g. pain, headache, nauseam malaise
What are characteristics of bacteria infections
localized inflammation, pus
e.g. dental abscess
What are characteristics of viral infections
tend to be systemic but some are local
e.g. herpes
What are characteristics of fungal infections
mycoses
often skin conditions but can go deeper e.g. thrush
What are stages in progression of disease
- Incubation period
- Prodromal period
- illness
- decline
- convalescence
What is the incubation period
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.
What is the prodromal period
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.
what is illness in the progression of disease
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.
what is decline in the progression of disease
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.
What is convalescent in the progression of disease
No signs or symptoms
What are the types of infection
- acute
- chronic
- latent
- localised infections
- systemic infections
- focal (disseminated) infections
What is an acute infection
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
What is a chronic infection
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
What is a latent infection
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
What is a localized infection
Infections which are confined to a specific area or organ within the body. Symptoms are often localized too.
e.g. skin infections
What is a systemic infection
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
What is a focal (disseminated) infection
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
What are endogenous infections
Infections which are host derived - the source of infection is from inside the host
e.g. shift in microorganism
Examples of endogenous infections
- surgical wound infections - Staphylococcus epidermidis
- oral streptococci - infective endocarditis
- Overgrowth of Candida albicans - oral thrush
What are exogenous infections
Infection caused by an outside source
Example of exogenous infections
- herpes implex virus
- Hepatitis B
- HIV
- Measles
What are the 3 main factors required for disease to occur
- Microorganism able to cause disease
- host susceptible to infection
- suitable environment for survival and transmission
What is HVB - Hepatitis B Virus
- 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 liver and can develop into cirrhosis (liver scaring) 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
What are body fluids with low/not detectable concentration of HBV
- urine
- faeces
- sweat
- tears
- breast milk
What are body fluids with moderate concentration of HBV
- semen
- vaginal fluid
- saliva
What are body fluids with a high concentration of HBV
- blood
- serum (liquid part of blood)
- Wound exudates
- GCF (gingivitis)
What is HIV - Human Immunodeficiency Virus
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
What is Pseudomonas Aeruginosa
Pseudomonas aeruginosa is a versatile and opportunistic Gram-negative bacterium that can cause a wide range of infections, in the blood, lungs (pneumonia)
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
What is Impetigo
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
What is infective endocarditis
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.
- If you have this and then during dental surgery or poor oral hygiene allows bacteria to enter the bloodstream and attach to damaged valves it can lead to heart failure
- it is usually caused by bacterial infection. Bacteria can reach your heart through your mouth after a dental procedure or after regular brushing and flossing
