Week 5 Lecture Flashcards
involve interaction between the body of the host and the infecting microorganisms.
Infection and immunity
They are found in soil and water and They are of little relevance in infectious disease.
Saprophytes
From Greek word sapros it means
Decayed
From greek word phytons it means
Plant
(organisms of normal flora) are the microorganisms that live in complete harmony with the host without causing any damage to it.
Commensals
are the microorganisms or agents, which are capable of producing disease in the host.
Pathogens
Its ability to cause disease is called
pathogenicity
are the organisms, which are capable of producing disease in previously healthy individuals with intact immunological defenses.
Primary (frank) Pathogens
rarely cause disease in individuals with intact immunological and anatomical defenses.
Opportunist Pathogens
These bacteria are able to cause disease only when such defenses are impaired or compromised.
Opportunist Pathogens
The lodgement and multiplication of an agent on the tissues of a host constitute infection.
Infection
It does not invariably result in disease.
Infection
Initial infection of an organisms in the host
Primary infection
Subsequent infections by the same
organism in the host
Reinfections
When a new agent sets up an infection in
a host whose resistance is lowered by a pre-
existing infectious disease.
Secondary Infection
An infection that is confined in one area
Local Infection
Cross-infections occurring in hospitals are called (from Greek nosocomion hospital)
Nosocomial Infections
The term refers to physician induced infections resulting from investigative, therapeutic, or other procedures.
Iatrogenic Infection
What type of infection is one where clinical effects are not apparent
Inapparent Infection
The term is often used as a synonym to inapparent infection.
Subclinical Infection
is one in which the typical or characteristic clinical manifestations of the particular infectious disease are not present.
Atypical Infection
Some organisms, following infection, may remain in the tissues in a latent or hidden form proliferating and producing clinical disease when the host resistance is lowered.
Latent Infection
Give the Sources of Infection
- Human being
- Animals
- Insects
- Soil and water
- Food
Most common source of infection for themselves. The parasite may originate from a patient or carrier.
Human Beings
Humans serving as the microbial reservoir
Touching, blood transfusions, sexual contact and cough
is person who harbors the microorganisms without suffering from any ill effect because of it.
Carrier
What type of carries is An individual who has recovered from the infectious disease but continues to harbor large numbers of pathogen.
Convalescent carrier
What type of carrier is an individual who harbors the pathogen but is not ill.
Healthy carrier
What type of carrier is an individual who is incubating the pathogen in large numbers but is not yet ill.
Incubatory carrier
What type of carrier is Convalescent, healthy, and incubatory carriers may harbor the pathogen for only a brief period (hours, days, or weeks) and lasts less than six months.
Temporary carrier
What type of carrier that They harbor the pathogen for long periods (months, years or life)
Chronic carrier
What type of carrier is applied to a person who acquires the pathogen from a patient
Contact carrier
What type of carrier refers to a carrier who acquires the pathogens from another carrier
Paradoxical carrier
The diseases and infections, which are transmissible to man from animals called
Zoonosis
These, animals serve to maintain the parasite in nature and act as reservoir and they are, therefore, called
Reservior hosts
Many pathogens are capable of causing in both human beings and animals. Therefore, animals may act as a source of infection of such microorganisms.
Reservoir hosts
Examples of Zoonotic Disease in bacterial
Anthrax, brucellosis, Q fever, leptospirosis, bovine tuberculosis, bubonic plague, Salmonella food poisoning.
Examples of Zoonotic Disease in viral
Rabies, yellow fever, cowpox, monkeypox.
Examples of Zoonotic Disease in protozoal
Leishmaniasis, toxoplasmosis, trypano-
somiasis, babesiosis.
Examples of Zoonotic Disease in helminthic
Echinococcosis, taeniasis, trichinellosis.
Examples of Zoonotic Disease in fungal
Microsporum canis, Trichophyton verrucosum.
Blood-sucking insects, such as mosquitos, ticks, mites, flies, and lice may transmit pathogens to human beings and diseases so caused are called
Arthropod-borne Diseases
in relapsing fever and spotted fever
Ticks
Insects that transmit infections are called
Vectors
can be of two types either mechanical (external) or biological (internal).
Vector-borne transmission
What type of vectors is The disease agent is transmitted mechanically by the arthropod.
Mechanical vector
What type of vector is Those in whom the pathogens multiply sufficiently or have undergone a developmental cycle.
Biological vector
The interval between the time of entry of the pathogen into the vector and the vector becoming infective is called the
extrinsic incubation period
remain viable in the soil for several decades and serve as source of infection.
Spores of Tetanus and Gas Gangrene
also survive in the soil and cause human infection.
Fungi (causing mycetoma, sporotrichosis, histoplasmosis) and parasites (roundworms and hookworms )
may act as the source of infection either due to contamination with pathogenic microorganisms (Shigella, Salmonella, Vibrio cholerae, poliomyelitis virus, hepatitis virus) or due the presence of aquatic vector (cyclops containing larvae of guinea worm infection).
Water
may act as source of infection of organisms causing food poisoning, gastroenteritits, diarrhea and dysentery
Food
Modes Of Transmission of Infection may be acquired by contact, which may be direct or indirect.
Contact
Diseases transmitted by ________ include STD (sexually transmitted diseases), such as syphilis, gonorrhea, lymphogranuloma venereum, lymphogranuloma inguinale, trichomoniasis, herpes simplex type 2,hepatitis B and acquired immunodeficiency syndrome (AIDS).
Direct contact
may be through the agency of fomites, which are inanimate objects, such as clothing, pencils or toys which may be contaminated by a pathogen from one person and act as a vehicle for its transmission to another.
Indirect contact
Droplet nuclei: Respiratory infections, such as common cold, influenza, measles, mumps, tuberculosis and whooping cough are acquired by
Inhalation
are generally acquired by the ingestion of food or drink contaminated by pathogens.
Ingestion
Infection transmitted by ingestion may be water borne (cholera), food borne (food poisoning o hand borne (dysentery).
Ingestion
Disease transmitted by water and food include chiefly infections of the alimentary tract, e.g. acute diarrheas, typhoid fever, cholera, polio, hepatitis A, food poisoning and intestinal parasites.
Ingestion
Disease agent may be inoculated directly in to the skin or mucosa, e.g. Rabies virus deposited subcutaneously by dog bite, tetanus spores implanted in deep wounds, and arboviruses injected by insect vectors.
Inoculation
Infection by inoculation may be iatrogenic when unsterile syringes and surgical equipment are employed.
Inoculation
It is involve in Hepatitis b and the human immunodeficiency virus (HIV).
Inoculation
Vector is defined as an arthropod or any living carrier (e.g. snail) that transports an infectious agent to a susceptible individual.
Insect
In some diseases, blood-sucking insects play an important role in the spread of infection from one individual to another
Vector- borne
Vertical Transmission: Some pathogens are able to cross the placental barrier
and reach the fetus in uterus.
Congenital
Examples of congenital
TORCH agents (Toxoplasma gondii, rubella virus, cytomegalovirus and herpes
virus)
If meticulous care in asepsis is not taken, infections like AIDS and hepatitis B may sometimes be transmitted during administration of injections, lumber puncture and catheterization.
Iatrogenic infections
These iatrogenic are known as
physician- induced infections
Modern methods of treatment, such as exchange transfusion, dialysis, and heart and transplant surgery have increased the possibilities for iatrogenic infections.
Iatrogenic infection or laboratory infections
It is the ability of a microbe to produce disease in a susceptible individual
Pathogenicity
the relative ability of microorganism to cause disease or the degree of pathogenicity
Virulence
Reduction of virulence
Attenuation
The first step of the infectious process is the entry of microorganism into the host by one of several ports: the respiratory tract, gastrointestinal tract, urogenital tract, or through skin that has been cut, punctured, or burned.
Transmissibility
The initial event in the pathogenesis is the attachment of the bacteria to body surfaces.
Adhesion
This attachment is not a chance event but a specific reaction between surface receptors on host cells and adhesive structures (ligands) on the surface of bacteria.
Adhesion
may occur as organized structures, such as fimbriae or fibrillae and pilli, or as colonization factors.
Adhesion
usually made of protein and are antigenic in nature.
Adhesion
has been attempted as a method of prophylaxis in some infections.
Adhesion
signifies the ability of a pathogen to spread in the host tissues after establishing infection.
Invasiveness
characteristically produce spreading or generalized lesions (e.g. Streptococcal septicemia following wound infection)
Highly invasive pathogens
cause more localized lesions (e.g. staphylococcal abscess).
Less invasive pathogens
Some bacteria cause disease by producing toxins, of which there are two general types: The exotoxins and the endotoxins
Toxigenicity
are soluble, heat-labile proteins inactivated at 60°–80°C and diffuse readily into the surrounding medium.
Exotoxins
These are highly potent in minute amounts and include some of the most poisonous substances known.
Exotoxins
are thus useful in preparing vaccines.
Exotoxins
They exhibit specific tissue affinity and
pharmacological activities.
Exotoxins
They are associated with specific diseases
and have specific mechanisms of action.
Exotoxins
Exotoxins They are easily inactivated by
Formaldehyde, iodine and other immunogenic toxoids
are generally formed by gram- positive bacteria but may also be produced by some gram-negative organisms such as Shiga’s dysentery bacillu
Exotoxins
These are heat-stable, lipopolysaccharide (LPS) components of the outer membranes of gram negative.
Endotoxins
Their toxicity depends upon the component (lipid A).
Endotoxins
They are released into the host’s circulation following bacterial cell lysis.
Endotoxins
They are toxic only at high doses.
Endotoxins
They cannot be toxoided.
Endotoxins
They are poor antigens and weakly
immunogenic.
Endotoxins
They do not exhibit specific pharmacological
activities.
Endotoxins
Intravenous injections of large doses of
endotoxin and massive gram-negative septicemias cause endotoxic shock marked by fever, leukopenia, thrombocytopenia, significant fall in blood pressure, circulatory collapse and bloody diarrhea leading to death
Endotoxins
Some bacteria such as Streptococcus pneumoniae, Neisseria meningitidis, and Haemophilus influenzae can produce a slippery mucoid capsule that prevents the phagocyte from effectively contacting the bacterium. Streptococcal M Protein
Capsule
Other bacteria evade phagocytosis by producing specialized surface proteins such as the M protein on Streptococcus pyogenes.
Capsule
can acquire iron from the host’s iron binding proteins.
Siderophores
is produced by Staphylococcus. aureus. This thrombin-like enzyme prevents phagocytosis by forming a fibrin barrier around the bacteria and walling off the lesion.
Coagulase
C. perfringens produces _________ and ______ promoting spread of infection in tissue.
Lecithinase-C and collagenase
split hyaluronic acid and thus facilitate the spread of infection along tissue spaces, e.g. Streptococcus.
Hyaluronidases
Many hemolytic streptococci produce _______ which promotes the spread of infections.
Streptokinase (fibrinolysin)
These include hemolysins capable of destroying erythrocytes and leukocidins damage polymorphonuclear leukocytes.
Cytolysins
These enzymes specifically cleave immunoglobulin IgA which protects at mucosal surfaces.
IgA 1 proteases
are extrachromosomal DNA segments that carry genes for antibiotic resistance known as R-factors.
Plasmids
increase the severity of clinical disease by their resistance to antibiotic therapy.
Multiple drug resistance (R) plasmids
The ability of a microbe to spread from one host to another
Communicability
Adequate number of bacteria is required for successful infections. The dosage may be estimated as the minimum infecting dose (MID) or minimum lethal dose (MLD).
Infective dose
Certain bacteria are infective when introduced through optimal route
Route of infection
may be superficial or deep seated.
Localized infections
Circulation of bacteria in the blood is known as.
bacteremia
It is the condition where bacteria circulate and multiply in the blood, form toxic products and cause high, swinging type of fever.
Septicemia
It is a condition where pyogenic bacteria produce septicemia with multiple abscesses in internal organs, such as the spleen, liver and kidney.
Pyemia
The disease which is constantly present in a particular area, e.g. typhoid fever is endemic in most parts of India.
Endemic
The disease that spreads rapidly, involving many persons in a particular area at the same time, is called e.g. meningococcal meningitis.
Epidemic
It is an epidemic that spreads through many areas of the world involving very large number of persons within a short period, e.g. cholera, influenza and enteroviral conjunctivitis.
Pandemic
Association of two organisms living in close proximity
Symbiosis
symbiotic relationship in which both organisms benefit from each other
Mutualism
one organism benefits while there is no beneficial or harmful effect to the other
Commensalism
one organism (parasite) benefits at the expense of its host
Parasitism
It is caused by a microorganism from the microbiota of the host.
Autogenous infection
It is an infection that occurs as the result of some medical treatment or procedure
Iatrogenic infection
affects immunocompromised host by not individuals with a normal immune system
Opportunistic infection
hospital acquired infection; acquired at a healthcare facility
Nosocomial infection
presence of bacteria in the blood without active multiplication
Bacteremia
active multiplication of invading bacteria in the blood
Septicemia
pus-producing organisms repeatedly invade the blood stream and become localized at different parts of the body
Pyemia
presence of toxins in the blood
Toxemia
signs and symptoms are confined in one area
Local infection
starts as a local infection before spreading to other parts of the body
Focal infection
microbes spread throughout the body through the blood or lymph
Systemic infection
initial infection that causes the illness
Primary
Example of Primary infection
Common cold
caused by opportunistic pathogens after primary infection has weakened the host’s immune system
Secondary infection
Example of secondary infection
pneumonia and bronchitis
clinically silent inside the body and causes no noticeable illnesses in the host. Then, a severe and acute infection manifests
Latent (silent phase)
Example of Latent (silent phase)
Asymptomatic-type polio infection
caused by two or more organisms
Mixed infections
Example of mixed infection
wound infection
refer to microbe living inside a host for a limited period of time, typically less than six months
Acute infection
Example of acute infection
Whooping cough
develops slowly with milder but longer-lasting symptoms
Chronic Infection
Example of chronic infection
Tubercolosis
ability of a pathogenic agent to produce a disease in a susceptible individual
Pathogenicity
degree of pathogenicity
Virulence
toxins cause tissue and cellular damage
Toxic factors
Give one of the toxic factors
diphtheria toxin, tetanospasmin, botulism toxin, enterotoxin
produced by bacteria that aid in the spread of infection and disease
Enzymatic factors
Give the enzymatic factors
hyaluronidase, coagulase, leucocidin, collagenase
capsules resist phagocytosis
Cellular structure
skin serves as the physical and chemical barrier to microorganisms.
Physical barriers
nasal hairs keep out airborne particles; “cough-sneeze” reflex contributes to removal of potential infective agents; cilia move trapped mucus
Cleansing mechanism
lysozymes destroy bacterial cell walls and bile salts disrupt bacterial membranes
Antimicrobial substances
commonly found in healthy person
Indigenous microbial flora
phagocytes engulf and dispose of microorganisms and cell debris
Phagocytosis
Ability to create a specific protective response against microorganisms
Immune response
“memorizes” all of the encountered microorganism so that an immune mediated defensive response is immediately available in the second or third time they are encountered
Immune system
based on the action of soluble proteins called antibodies. From B-lymphocytes
Humoral (antibody-mediated)
action of specific kinds of T-lymphocytes that directly attack the cells that are infected
Cellular (cell-mediated)
protection of susceptible humans and domestic animals from communicable diseases through vaccination
Active immunization
non-specific response that activates chemotaxis, or the process by which phagocytes are directed to the site of replication and engulf the invading organism
Natural immunity
antibodies that are attached to the surface of the pathogens and which kill the bacteria by lysis
Complement-fixing antibodies
attached to the surface of microorganisms which block surface receptors
Neutralizing antibodies
attached to the surface of microorganisms and render pathogens susceptible to phagocytosis
Opsonizing antibodies
