Chapter 1 Flashcards
What is pathogenicity?
The ability to cause disease by overcoming the defenses of the host
What is a pathogen
A microorganism causes infection/disease
What is the virulence?
The degree or extent of pathogenicity
What is an infection?
The invasion or colonization of the body by pathogenic microorganisms
When does a disease occurs?
When the infection results in any chance in the normal state of the body to the abnormal
Name an example for an infection without a disease
AIDS
Identify inflammation
The localized tissues response to an injury or infection, often characterized by redness, swelling,pain, warmth, and pus
What does the ability of microorganisms to infect or cause disease depends on?
1 Interactions with the host defence mechanisms
2 the virulence factor
3 quantity/ number of invading microbes
Name the factors that determine the distribution and composition of normal microbes
Nutrients
Physical and chemical: temperature, pH, Oxygen, Co2, sunlight
Mechanical factors: chewing of the teeth and tongue, flow of saliva, flushing action of urine, mucus and cilia I’m the respiratory system
Defenses of the host,age, diet, health, disability, hygiene, stress
What is the relationship between normal and pathogenic microorganisms?
Microbial antagonism or competitive exclusion
What does microbial antagonism involves?
COMPETITION FOR:
nutrients
Producing harmful substances to the invading microbes (E.coli—-bacteriocin)
Affecting conditions such as PH
Give an example on bacteria that produce harmful substances to the invading microbes
E.coli:
It produces bacteriocins protein that inhibits the growth of salmonella and shigella
Give an example for a microorganism that grows after the PH or other conditions have been effected
After pH change Candida albicans (fungi) causes vaginitis
After normal bacteria elimination Clostridium difficile (gram positive anaerobic) causes fatal colitis
What are the the relationships between normal microbes and the host are? (Symbiosis) with examples
Commensalism: one benefits other doesn’t
Example staphylococcus epidermis (gram positive)
Mutualism: both benefits
Example E.coli ( gram -) synthesis vitamin K and B
Parasitism: one benefits while the other gets badly effected
Example: many disease causing bacteria
Identify opportunistic pathogens
They are pathogens that doesn’t cause a disease on normal states but do so on different environmental conditions
Give examples for opportunistic pathogens conditions with examples
Gaining access to other body sites such as the skin and mucous membranes
Example E.coli ( gram negative)
The host immunity is weakened by an infection
Example: Pneumocystis pneumonia (fungal) onlu happens after AIDS
Cooperation among microorganisms
Example in the mouth pathogens that causes periodontal disease and gingivitis have receptors for the oral streptococci
What are the exception to Koch’s postulates with examples
1 some have unique culture requirements
Example: Treponema pallidum that causes syphilis
- Signs and symptoms can be only exhibited in humans
- Some diseases have poorly defined etiologies
Example: nephritis have several pathogens with the same signs and symptoms
4 some pathogens causes several diseases for example: mycobacterium tuberculosis causes diseases in the lungs, skin and bones
Streptococcus pyogenes can cause sore throat, scarlet fever and skin infections
What are the sources of microbes?
Another host or nonliving disease reservoir
What are the requirements for a successful pathogen
1 Surviving the passage
2 attach or penetrate the hosts tissues
3 withstand the host’s defenses
4 induce damage or malfunction to the tissues
What does symptoms mean
Changes in the body functions, such as pain ( can’t be observed or seen by an observer)
What does signs mean
Changes in the body that can be seen and measured such as swelling and fever
What does syndrome means
A group of symptoms or sings are evaluated together
What is a communicable disease
A disease that spreads from one host to another, directly or indirectly
Incidence vs prevalence
Incidence: probability of developing a disease, counting ONLY NEW cases, requires a follow up from individuals, doesn’t depend on the duration of the illness, preferred when studying the cause
Prevalence: probability of already having a disease, counts BOTH new and old, does not require a follow up, depends on the duration of the disease, preferred when estimating the population based burden of chronic disease
Classify disease by the frequency of occurrence with examples
1 sporadic diseases: occasionally
Example: typhoid fever
2 endemic disease: constantly present in a population
Example: common cold
3 epidemic: many people in a given area with a certain disease in a short period
Example: Influenza
4 pandemic: worldwide disease
Example p: COVID-19 حبيب الشعب
Classify diseases by severity or duration
1 Acute: rapid but last a short time
Example: tonsillitis
2 chronic disease: develops slowly and last a long period
Example: Lyme disease
3 subacute: between Acute and chronic
4 latent : remains inactive then becomes active to produce symptoms
Examples versilia zoster( virus) (خبيث زي انشالوتي)
What is the herd immunity
Many immune people are presein a community
What is a local infection
invading microorganisms are limited to a relatively small area
of the body. Such as boils and abscesses
What is a systematic infection
infection, microorganisms or their products are spread
throughout the body by the blood or lymph. Such as Measles and scarlet fever.
What is a focal infection
agents of a local infection enter a blood or lymphatic vessel
and spread to other specific parts of the body
Identify the following
Sepsis, septicemia, bacteremia, toxemia, viremia
Sepsis: a toxic inflammatory conditions arising from the spread of microbes
Septicemia: blood poisoning because of pathogens in the blood
Bacteremia: bacteria in the blood
Toxemia: toxins in the blood
Viremia: viruses in the blood
What are the differences between primary and secondary infections
Primary infection: an Acute infection that causes the main illness
Secondary infections: is an infection caused by an opportunistic pathogens because of the weakened immune system due to the primary infection
Example: any infection because of AIDS
Streptococcal bronchopneumonia after influenza
What is the subclinical (inapparent) infection
An infection that doesn’t cause any noticeable illness
Example: polio virus, AIDS, H.pylori, hepatitis A
Identify predisposing factors and name them with examples
They are the factors that makes the body more susceptible to a disease and may change the course of the disease
- Gender: females higher UTI than males males higher pneumonia and meningitis
- Genetic background: sickle cells patients are resistant to the malaria
- Climate and weather: higher respiratory disease increase during the winter
4 other: age, habits, lifestyle, chemotherapy, preexisting illness
What are the stages of disease developments
1 Incubation 2 prodromal 3 period of illness 4 period of decline 5 period of convalescence
What is the incubation period and what does it depend on
It’s the time between the initial infection and the appearance of any signs or symptoms
It depends on:
1 virulence
2 number of microorganisms
3 resistance of the host
What kind of symptoms does the prodromal period have
Mild symptoms such as aches and malaise
At what stage dies the illness become severe
Period of illness
When does the patient becomes the most vulnerable to secondary infections
Period of decline
What are the three main ways of disease transmission
1 contact
2 vehicle
3 vectors
What are the types of contact transmission with examples
1 Direct contact (person to person)
Example: touching, kissing and sexual intercourse
2 indirect contact by fomite (nonliving objects
Examples: towels, tissues, bedding, cups, toys
3 droplets (less than 1M) Examples coughing, sneezing, laughing and talking
Identify vehicle transmission and it’s types
Transmission by medium such as water, blood and other fluids
1 airborne: infection by droplets in nuclei in dust that TRAVELS MORE THAN 1 METER
2 Waterborne By water contaminated with sewage
3 Foodborne by poorly cooked food
What is transmission by vectors and it’s types
Transmission by biological agents such as insects
The types
1 mechanical transmission such as insects feets
2 biological transmission such as biting
What is nosocomial infections and name the top causes
It’s hospital related infections caused by
1 microorganisms in the hospital
2 The weakened status of the host
3 The chain transmission in the hospital
What are the most frequent nosocomial infections
1 UTI 34%
2 skin infections 22%
3 surgical site 17%
4 LRTI 13%
What are the contributing factors for emerging infectious diseases
1 evolution of a new strain such as V. Cholerae and E coli
2 inappropriate use of antibiotics which results in antibiotics resistance strains
3 changes in the weather
4 modern transportation systems such as airplanes ventilation system
5 ecological disaster such as coccidioidomycosis after 1994 California earthquake
6 insects and animals control measure
Exam, Lyme disease because of the rise in deer population
7 public health failure
8 diphtheria
Identify epidemiology
the science that studies
when and where diseases occur
and how they are transmitted in
populations.
What are the epidemiology applications?
1) descriptive: Collection and analysis of data regarding
occurrence of disease
2) analytical: Comparison of a diseased group and a
healthy group
3) experimental: Study of a disease using controlled experiments
4) case reporting: Health care workers report specified disease to local, state, and national offices
5) nationally notifiable diseases: Physicians are required to report occurrence
What are the differences between morbidity and mortality
Morbidity: incidence of a specific notifiable disease
Mortality: deaths from notifiable diseases
What is the morbidity rate
number of people affected/total population in a given time period
What is the mortality rate
number of deaths from a disease/total population in a given time
What are the portals of entry
1) skin
2) mucous membranes
3) parenteral
4) preferred portal of entry such as swallowing and inhaling
How does the microorganism enters the body through the skin?
1) Openings in the skin such as sweat glands
2) boring in the skin such as the larvae of the hookworms
3) grows on the keratin in the skin like fungi
4 infection of the mucous membrane itself such as conjunctiva
Where is the mucous membrane membrane
1) respiratory tract
2) gastrointestinal tract
3) conjunctiva
4) genitourinary tract
What is the most frequently traveled portal of entry?
Respiratory tract
Name some diseases that uses the respiratory tract as an entry
the common cold, pneumonia, tuberculosis, influenza, and
measles
Same some microbes that causes diseases the gastrointestinal tract
Poliomyelitis, hepatitis E & A, typhoid fever, amebic dysentery,
giardiasis, shigellosis (bacillary dysentery), listeriosis,
salmonellosis and cholera.
Name some sexually transmitted infections (genitourinary tract entry)
HIV infection, genital warts, chlamydia,
herpes, syphilis, Borrelia and gonorrhea
How does the microorganism enters using the parental route
Punctures, injections, bites, cuts, wounds,
surgery, and splitting of the skin or mucous
membrane due to swelling or drying can all establish parenteral routes
Name same diseases that uses the parenteral route
HIV, the hepatitis viruses, and bacteria that cause tetanus, Lyme disease and gangrene
What bacteria prefers the entry route through swallowing
Typhoid fever, (Salmonella typhi)
What bacteria prefers the entry route through inhaling
Streptococci cause pneumonia
Name some microorganisms with multiple entry routes
Yersinia pestis (gram negative) and Bacillus anthracis (gram negative)
What are the different ID50s for Bacillus anthracis
oThrough the skin (cutaneous anthrax) is 10 to 50
endospores;
o Inhalation 10,000 to 20,000 endospores;
oGastrointestinal 250,000 to 1,000,000 endospores
Give some examples for LD50
✓ Botulinum toxin in mice is 0.03 ng/kg; for
✓ Shiga toxin, 250 ng/kg; and
✓ Staphylococcal enterotoxin, 1350 ng/kg
How do the bacterial pathogens penetrate the host defenses
1) capsules
2) cell wall components
3) enzyme
4) antigenic variation
What are the capsules made of with some examples
Glycocalyx
Example: ➢Streptococcus pneumoniae, only capsulated Strains are virulent.
➢Klebsiella pneumoniae, a causative agent of bacterial
pneumonia
Give some examples for cell wall components
A. M protein produce by Streptococcus pyogenes found on both the cell surface and fimbriae.
B. Fimbrae and Opa protein in Neisseria gonorrhoeae grows inside human epithelial cells and leukocytes.
C. The waxy lipid (mycolic acid) that makes up the cell wall of
Mycobacterium tuberculosis also increases virulence by
resisting digestion by phagocytes, and can even multiply inside phagocytes
Give some examples for exoenzymes
a. Coagulases are bacterial enzymes that coagulate (clot) the fibrinogen in blood.
b. Bacterial kinases are bacterial enzymes that break down fibrin and thus digest clotsformedby the body to isolate the infection such as : fibrinolysin (streptokinase)
c. Hyaluronidase hydrolyzes hyaluronic acid,a type of polysaccharide that holds
together certain cells of the body,
particularly cells in connective tissue
Give some examples for an antigenic variation
- N. gonorrhoeae has several copies of the Opa-encoding gene.
- Influenza virus
- Trypanosoma brucei gambiense the
causative agent of African trypanosomiasis (sleeping sickness).
How Bacterial Pathogens Damage Host Cells
(1) Using the host’s nutrients; Bacteria can obtain Iron by:
– Siderophores which are proteins secrete by microbes to obtain free iron from iron transport proteins lactoferrin,
transferrin, Hemoglobin and ferritin of the host.
(2) Causing direct damage in the immediate vicinity of the
invasion; by rupturing the cell during penetration or after multiplication
(3) Producing toxins, transported by blood and lymph,
(4) Inducing hypersensitivity reactions: immune response
What are the two types of Bacterial toxins?
Exotoxins and endotoxins
Where is the exotoxin produced?
Inside gram negative and positive bacteria as part of their growth and metabolism
What is a toxoid
inactivated toxins by heat or by formaldehyde, iodine, or other chemicals,
• Cannot cause the disease .
• Used as vaccine to stimulate the body to produce antitoxins..
What are the types of exotoxins
1) A-B Toxins : consist of two parts designated as A and B, A part is the active (enzyme) component, and the B part is the binding component (H. pylori)
2)Membrane-Disrupting Toxins
cause lysis of host cells by disrupting their plasma membranes (Staph and
Streptococcus).
3) Superantigens: are antigens that
provoke a very intense immune
response (S. aureus)
How do endotoxins differ from exotoxins
- They are part of the outer portion of
the cell wall of gram-negative bacteria
lipopolysaccharides (LPS) - Endotoxins are released when death or during bacterial multiplication
- Endotoxins stimulate T-lymphocytes to release cytokines in very high concentrations
4.All endotoxins produce the same signs and symptoms, regardless of the species of microorganism
Example: Chills, fever, weakness, generalized aches, and, in some cases, shock and even death
What are the fungi’s pathogenic properties
- The production of toxins that provokes allergic responses and causes headaches and vomiting
- Secrete proteases that causes skin infections
Example: Candida albicans and Trichophyton - Producing capsules like Cryptococcus neoformans that causes meningitis
- causing ergotism
Producing toxins lime Aflatoxin (Aspergillus flavus) and mycotoxins like phalloidin and amanitin
How does ergotism help in resistance to antifungals
by decreasing the synthesis
of receptors for these drugs
Who produces ergot and what does it do
Claviceps purpurea
➢ can cause hallucinations
➢ can cause gangrene of the limbs
What are the pathogenic properties of protozoa
- The presence of protozoa and their waste products often produces disease
- Some protozoa can evade host defenses and cause disease for very long periods of time by antigenic variation
Give examples for a protozoa and their waste products that causes illness
❖ Plasmodium, the causative agent of malaria, invade host cells
(liver, RBCs) and reproduce within them, causing their
rupture and the release of hemozoin that causes the chill and fever symtoms.
❖ Toxoplasma attaches to macrophages and gains entry by phagocytosis.
❖ Giardia lamblia, the causative agent of giardiasis, attach to host cells by a sucking disc
Name some protozoa with antigenic variation
❑Giardia, which causes diarrhea,
❑Trypanosoma, which causes African
trypanosomiasis (sleeping sickness)
What is elephantiasis and what causes it
Wuchereria bancrofti
This parasite blocks
lymphatic circulation, leading to an accumulation oflymph and eventually causing grotesque swelling of the legs andother body parts.
Name some examples for algae that produce neurotoxin
Alexandrium, (are important
medically) they produce a neurotoxin called saxitoxin.
What are the portals of exists
- Respiratory: coughing and sneezing
- Gastrointestinal: (feces and saliva)
- Genitourinary
- Skin or wound
- Infected blood
Give examples for diseases that uses the RESPIRATORY exist
tuberculosis, whooping cough, pneumonia, scarlet fever,
meningococcal meningitis, chickenpox, measles, mumps, smallpox, and
influenza
Give examples for diseases that uses FECES as a exist
salmonellosis, cholera, typhoid fever, shigellosis, amebic dysentery, and
poliomyelitis, listeriosis
Give examples for diseases that uses SALIVA as an exit
rabies, mumps, and infectious mononucleosis
Name some diseases that uses URINE as a exist
typhoid fever and brucellosis,
Name disease that uses the SKIN as a portal of exist
yaws, impetigo, ringworm,
herpes simplex, and warts
Name some diseases that are transmitted by biting
yellowfever, plague , tularemia , and malaria.
Name some diseases that uses needles and syringes
AIDS and hepatitis B
