Lecture 11: Pathogenicity & Epidemiology Flashcards
What is the ability to cause disease?
Pathogenicity
What is the extent of pathogenicity?
Virulence
What are virulence factors?
Adhesion factors
Extracellular enzymes
Toxins
Antiphagocytic factors
What are the the adhesion factors on microbes?
Surface lipoproteins or glycoproteins called ligands bind to receptors on host cells
Ability to change of block the ligand or its receptor can prevent infection
Inability to make attachment proteins or adhesions renders the microorganisms arvirulent
Which enzyme coagulate blood?
Coagulase
Which enzyme digest fibrin clots?
Kinases
Which enzyme hydrolyses hyaluronic acid?
Hylaluronidase
Which enzyme hydrolyzes collagen?
Collagenase
Which enzyme destroy IgA antibodies?
IgA proteases
Which enzyme take iron from host iron-binding proteins?
Siderophores
Which enzyme alter surface proteins?
Antigenic variation
What are substances that contribute to pathogenicity?
Toxin
What is the ability to produce a toxin?
Toxigenicity
What is the presence of toxin the host’s blood?
Toxemia
What is the inactivated toxin used in vaccine?
Toxoid
What are antibodies against a specific toxin?
Antitoixin
Discuss exotoxins
Exotoxins are produced inside mostly gram-positive bacteria as part of their growth and metabolism. They are then secreted or released following lysis into the surrounding medium.
Discuss III toxins: A-B toxins
see pic
Discuss type I toxins: superantigens
Cause an intense immune response due to cytokine released by hosts
Fever, nausea, vomiting, diarrhea, shock, death
Discuss type II toxins
Membrane-disrupting toxins
Lyse host’s cells:
-makes protein channels in the plasma membrane (ex. leukocidins, hemolysins)
-disrupts phospholipid bilayer
Discuss endotoxins
Endotoxins are part of the outer portion of the cell wall of gram-negative bacteria. They are liberated when the bacteria die and the cell wall breaks apart
Discuss antiphagocytic factors and certain factors that prevent phagocytosis by the host’s phagocytic cells
Bacterial capsule: composed of same chemicals found in host’s body
slippery -> difficult for phagocytes to engulf the bacteria
Antiphagocytic chemicals
-some prevent fusion of lysosome and phagocytic vesicles
-Leukocidins directly destroy phagocytic white blood cells
What are some pathogenic properties of protozoa?
-presence of protozoa
-protozoan waste products may cause symptoms
-avoid host defenses by
-growing in phagocytes
-antigenic variation
What are some pathogenic properties of fungi?
-fungal waste products may cause symptoms
-chronic infections provoke an allergic response
-mycotoxins
-capsule prevents phagocytosis
What are some pathogenic properties of helminths?
-use host tissue
-presence of parasite interferes with host function
-parasite’s metabolic waste can cause symptoms
What are some pathogenic properties of algae?
-Neurotoxins produced by dinoflagellates
-saxitoxin: paralytic shellfish poisoning
What are the mechanisms of pathogenicity?
see pic
portals of entry [number of invading microbes and adherence] -> penetration or evasion of host defenses -> damage to host cells/cytopathic effects -> portals of exit
What is pathology?
study of disease
What is the development of disease?
Pathogenesis
What is the study of the cause of a disease?
etiology
What is the colonization of the body by pathogens?
Infection
What is an abnormal state in which the body is not functionally normally?
Disease
What is transient microbiota?
-Present for hours, days, weeks, or months
-Cannot persist in the body
- competition from other microorganisms
- elimination by the body’s defenses cells
-chemical or physical changes in the body
What is normal microbiota?
permanently colonize the host
What is symbiosis?
Close, long-termed reactions between two organisms
[microbiota]
What is commensalism?
One organism is benefited and the other is unaffected
What is mutualism?
Both organisms benefit
What is parasitism?
One organism is benefited at the expense of the other
How does the normal microbiota protect the host by?
Occupying niches that pathogens might occupy
Producing acids
Producing bacteriocins
What are probiotics?
Live microbes applied to or ingested into the body, intended to exert a beneficial effect
Are some normal microbiota opportunistic pathogens?
Yes
What is microbial anatgonism?
Competition between microbes
What are the locations of normal microbiota in humans?
Nose and throat (upper respiratory system)
eyes
mouth
skin
large intestine
urinary and genital systems
What are resident microbiota?
see pic
What are opportunistic pathogens?
Normal microbiota that can cause disease under certain circumstances
What are the conditions that provide opportunities for pathogens?
Immune suppression
Changes in the normal microbiota - changes in relative abundance of normal microbiota may allow opportunity for a member to thrive and cause disease
Introduction of normal microbiota into unusual site in the body
What is contamination?
The mere presence of microbes in or on the body
What is an infection?
An organism has evaded the body’s external defenses, multiplied, and become established in the body
What are portals of entry and what are the four major types?
Sites through which pathogens enter the body
4 major types:
-skin
-mucous membranes
-placenta
-parenteral route
How is skin a portal of entry?
Outer layer of packed, dead, skin cells
Usually = a barrier to pathogens
Pathogens can enter (1) through openings or cuts, (2) some can burrow into or digest the outer layers of skin
How is a mucous membrane a portal of entry?
Line the body cavities that are open to the environment
Provides a moist, warm environment
Respiratory tract is the most commonly used site of entry (entry is through the nose, mouth, or eyes)
Gastrointestinal tract can be a route of entry
-pathogen must be able to survive the acidic pH of the stomach
How is a parenteral route a portal of entry?
Not a true portal of entry, via injection or insertion
Pathogens deposited directly into tissues beneath the skin or mucous membranes
Discuss pathogenic organisms
Portal of entry
Attachment or adhesion to cause infection (bacteria, viruses, and protozoa (parasites))
Infection - the invasion of the host by a pathogen
Disease - results only if the invading pathogen alters the normal functions of the body, also referred to as morbidity
What are Koch’s postulates?
- The suspected germ must be present in every case of the disease
- The germ must be isolated and grown in pure culture
- The cultured germ must cause the disease when it is inoculated into a healthy, susceptible experimental host (animal or plant
- The same germ must be reisolated from the diseased experimental host
What are the exceptions to Koch’s postulates?
Some pathogens can’t be cultured in the laboratory
Some diseases are caused by a combination of pathogens and other cofactors
Ethical considerations prevent applying to pathogens that require human host
Difficuluties:
-Diseases that can be caused by more than one pathogen
-Pathogens that are ignored as potential causes of disease
What is a symptom?
A change in body function that is felt by a patient as a result of disease
What is a syndrome?
A specific group of signs and symptoms that accompany a disease
What is a sign?
A change in a body that can be measured or observed as a result of disease
What is a communicable disease?
A disease that is spread from one host to another
What is a contagious disease?
A communicable disease that is easily spread
What is a non-communicable disease?
A disease that is not transmitted from one host to another
What is an acute disease?
Symptoms develop rapidly
What is a chronic disease?
Disease develops slowly
What is a subacute disease?
Symptoms between acute and chronic
What is a latent disease?
Disease with a period of no symptoms when the patient is inactive
What is a local infection?
Pathogens limited to a small area of the body
What is a systemic infection?
An infection throughout the body
What is a focal infection?
Systemic infection that began as a local infection
What is a bacteremia?
Bacteria in the blood
What is a septicemia?
Growth of bacteria in the blood
What is toxemia?
Toxins in the blood
What is viremia?
Viruses in the blood
What is a primary infection?
Acute infection that causes the initial illness
What is a secondary infection?
Opportunistic infection after a primary (predisposing) infection
What are some predisposing factors that make the body more susceptible to disease?
inherited traits such as sickle-cell gene
climate and weather
fatigue
age
lifestyle
short urethra in female
chemotherapy
What is a subclinical disease?
No noticeable signs or symptoms (inapparent infection)
What are the stages of infectious disease aka disease process?
- incubation period (no signs or symptoms)
2.prodromal period (vague, general symptoms)
- Illness (most severe signs and symptoms)
- Decline (declining signs and symptoms)
- Convalescence (no signs or symptoms)
How do pathogens leave through the portals of exit?
Ear (wax)
Broken skin (blood)
Skin (flakes)
Anus (feces)
seminal vesicles (semen and secretions)
urethra (urine)
vagina (secretions, blood)
mammary glands (milk, secretions)
mouth (saliva, sputum)
nose (secretions)
eyes (tears)
What are reservoirs of infection and some examples in humans, animals, and the nonliving?
They are continual sources of infection.
Humans - AIDS, gonorrhea
-carriers may have inapparent infections or latent diseases
Animal - rabies, lyme disease
-some zoonoses may be transmitted to humans
Nonliving - botulism, tetanus
-soil
What are the transmission of disease through contact?
Direct contact: requires close association between infected and susceptible host
Indirect contact: spread by fomites
Droplet transmission via airborne droplets
What are the transmission of disease via vehicle and vector?
Vehicles: transmission by an inanimate reservoir (food, water)
Vectors: arthropods, especially fleas, ticks, and mosquitoes
-mechanical arthropod carries pathogen on feet
-biological pathogen reproduces in vector
What are nosocomial infections?
Are acquired as a result of a hospital stay
5-15% of all hospital patients acquire nosocomial infections
What are emerging new diseases and contributing factors?
Evolution of new strains; ex v. cholera O139
Inappropriate use of antibiotics and pesticides: antibiotic resistant strains
Changes in weather patterns: Hantavirus
Modern transportation: West Nile virus
Ecological disaster, war, expanding human settlement: Coccidioidomycosis
Animal control measures: Lyme disease
Public health failure: diphtheria
What is epidemiology?
The study of where and when diseases occur and how they are transmitted in a population
During the occurrence of disease, what is incidence?
Fraction of a population that contracts a disease during a specific time period
During the occurrence of disease, what is prevalence?
Fraction of a population having a specific disease at a given time
What is endemic disease?
Disease constantly present in a population
Disease acquired by many hosts in a given area in a short time
What is a sporadic disease?
Disease that occurs occasionally in a population
What is morbidity?
Incidence of a specific notifiable disease
What is a pandemic disease?
Worldwide epidemic
What is mortality?
deaths from notifiable disease
