Pathogenesis of Microbial Infection
tf - Collagenase attacks collagen tissue
t' virulence factor enzyme Collagenase -Helps dissolve connective tissue allowing pathogen to invade tissues -Collagenase attacks collagen tissue -E.g. Clostridium perfringens
Opportunistic pathogen
a microbe that causes disease only when introduced into an unusual location or into an immunocompromised host
Transmission of infection There are many ways by which an infectious agent or pathogen can be transmitted to a susceptible host. Direct contact . . .
By air By water By vectors - Farm animals - Arthropods: e.g. mosquitoes - حيوانات المزرعة - مفصليات الأرجل: على سبيل المثال البعوض ........ Mechanism by which an infectious agent spread from a source to another person
Steps in Pathogenesis Mechanisms to escape host defense mechanisms
-Kill the phagocytic cell -Inhibit phagocytosis -Escape intracellular digestion -Grow inside the cell -Transmission -Entry of pathogen -Attachment to host tissue cells -Multiplication -Invasion -Evading host defenses -Damage to host tissues or toxinogenecity
Steps in Pathogenesis There are several steps involved before a pathogen establishes itself into host body and cause the disease
-Transmission -Entry of pathogen -Attachment to host tissue cells -Multiplication -Invasion -Evading host defenses -Damage to host tissues or toxinogenecity
chain of infection INFECTIOUS DISEASE Any microorganism that can ..................... such as a bacterium, virus, parasite, or fungus. Reasons that the organism will cause an infection are virulence (ability to multiply and grow), invasiveness (ability to enter tissue), and pathogenicity (ability to cause disease). RESERVOIR The _____________where the microorganism resides, thrives, and reproduces, i.e., food, water, toilet seat, elevator buttons, human feces, respiratory secretions. PORTAL OF EXIT The place where the organism___________________ such as the respiratory tract (nose, mouth), intestinal tract (rectum), urinary tract, or blood and other body fluids. MODE OF TRANSMISSION The means by which an organism ____________from one carrier to another by either____________-_______________ PORTAL OF ENTRY The ____________where an infectious disease enters the host's body such as mucus membranes, open wounds, or tubes inserted in body cavities like urinary catheters or feeding tubes. SUSCEPTIBLE HOST The person who is _______________for developing an infection from the disease. Several factors make a person more susceptible to disease including age (young people and elderly people generally are more at risk), underlying chronic diseases such as diabetes or asthma, conditions that weaken the immune system like HIV, certain types of medications, invasive devices like feeding tubes, and malnutrition.
.cause a disease place leaves the reservoir, transfers direct transmission (direct contact between infectious host and susceptible host) or indirect transmission (which involves an intermediate carrier like an environmental surface or piece of medical equipment). opening at risk
terms of cause infection disease
1-pathogen or 2-infectious agent
The Infectious Process
1. Incubation period 2. Prodromal period: 3. Illness stage 4. Convalescence
-the time between when the pathogen enters the body and when symptoms of the disease appear
1.Incubation period:
The Infectious Process Can be divided into 4 steps:
1.Incubation period: -the time between when the pathogen enters the body and when symptoms of the disease appear -Length varies due many factors 2.Prodormal period: -A time when a person is not feeling well but before the actual symptoms show up 3.Period of illness: -The time when actual symptoms of the disease are obvious -Actual length can vary from individual to individual -Transmission most often happens at this period 4.Convalescent period: -The time when an individual recovers from the illness -Time can vary and can be quiet long for illness caused by viruses
Koch's Postulates
1.The microorganism should be found in all cases of the disease reported Pathology and symptoms should be similar 2.The microorganism can be grown in pure culture in vitro (or outside the body of the host) for several generations 3.This isolated culture should be able to produce the disease when inoculated in a susceptible animal species. 4.The microorganism must again be isolated from the lesions of such experimentally produced disease
Definition of terms used in pathogenesis ______________(adhesion, attachment): The process by which bacteria stick to the surfaces of host cells. _______________: A person or animal with asymptomatic infection that can be transmitted to another susceptible person or animal. _________________: Multiplication of an infectious agent within the body. _____________: The process whereby bacteria, animal parasites, fungi, and viruses enter host cells or tissues and spread in the body. _____________: A microorganism that does not cause disease; may be part of the normal flora. ....................: An agent capable of causing disease only when the host's resistance is impaired (ie, when the patient is "immunocompromised"). .........................: A microorganism capable of causing disease. Pathogenicity: The ability of an infectious agent to cause disease. (See also virulence.) ...................: The ability of a microorganism to produce a toxin that contributes to the development of disease. 10......................... The quantitative ability of an agent to cause disease. Virulent agents cause disease when introduced into the host in small numbers. Virulence involves adherence, invasion, and toxigenicity (see above).
Adherence Carrier Infection Invasion Nonpathogen Opportunistic pathogen Pathogen Toxigenicity . Virulence:
Extracellular substances that cover a bacterial cell
CAPSULE
Extracellular substances that cover a bacterial cell They are anti-phagocytic preventing phagocytosis by white blood cells
CAPSULE
-E.g. tuberculosis, leprosy Ex of ?
Chronic disease
tf u Certain guidelines are needed to establish whether a disease is caused by an infectious agent
t
Steps in Pathogenesis -Damage to host tissues or toxinogenecity
Damage to host tissues 1.Bacteria-mediated Pathogenesis -Destroying host tissue (invasiveness) 2.Host-mediated Pathogenesis -Stimulating an excess of host immune response 3.Bacterial virulence factors -Also called bacterial toxins 1- التسبب في المرض بوساطة البكتيريا - تدمير أنسجة العائل (الغازية) 2 التسبب في المرض بوساطة المضيف - تحفيز زيادة الاستجابة المناعية للمضيف 3- عوامل الضراوة البكتيرية - تسمى أيضا السموم البكتيرية -------------------------------- -Transmission -Entry of pathogen -Attachment to host tissue cells -Multiplication -Invasion -Evading host defenses -Damage to host tissues or toxinogenecity
Escherichia coli, Vibrio cholera الإشريكية القولونية ، ضمة الكوليرا
Enterotoxins: affect the gastro-intestinal tract Cause diarrhea and vomiting Can lead to serious loss of body fluids Also damage to the intestinal lining E.g. Escherichia coli, Vibrio cholera exotoxin
Refers to the condition when an individual is exposed to a pathogen but does not develop the disease Also when an infectious disease stops producing the symptoms for a period of time However symptoms show up again after a period of time.
Latent infection- عدوى كامنة
Pathogenesis of a disease This is the mechanism by which a disease happens. Helps describe whether a disease is acute, chronic, or recurrent. Types of pathogenesis: 4:_____________________________ Helps identify the origin of the disease Currently, molecular techniques are combined with epidemiology to assess pathogenesis
Microbial infection Inflammation Malignancy Tissue breakdown
Destroy host tissues
Necrotizing enzymes:
Virulence factors: Toxins These are chemicals released by some bacteria that are poisonous for the human body Are of two types: 2. Exotoxins Poisonous proteins that can target certain organs of the body
Neurotoxins: affect the central nervous system E.g. tetanospasmin produced by Clostridium tetani Enterotoxins: affect the gastro-intestinal tract Cause diarrhea and vomiting Can lead to serious loss of body fluids Also damage to the intestinal lining E.g. Escherichia coli, Vibrio cholera فيه ثالثه •Diphtheria toxin: inhibits protein synthesis -Produced by C. diphtheriae -Kills epithelial cells and phagocytes -Also affects the central nervous system and the heart
This is the mechanism by which a disease happens.
Pathogenesis of a disease
Viruses that infect dogs may not infect humans because their cells do not have receptor for that virus
RECEPTOR AND ADHESION
Virulence
The quantitative ability of an agent to cause disease. Virulent agents cause disease when introduced into the host in *small numbers*. Virulence involves adherence, invasion, and toxigenicity (see above).
extent of disease that can be caused by a pathogen
Virulence خبث, الفوعة مقدار حدة الفيروس
Toxigenicity
ability of a microorganism to produce a toxin بعضها يسبب اسهال بسبب السم اللي خلا الخليه تفقد ماء
Enterotoxins
affect cells lining the gastrointestinal tract
- Enzymes that damage *red blood* cells causing anemia
hemolysin
Virulence factors : Attachment factors Also called adherence factors Invasion cannot occur until the pathogen attaches to part of the tissue Can be v ery specific - This is why pathogens that .................................. Receptors and Adhesins فيه MINDMAP IN WHATS
cause respiratory infection cannot cause gastrointestinal infection
Kinases
dissolve clots formed by host to isolate infection
Virulence u Means the...................................... u E.g. it takes only 10 cells of Shigella to cause shigellosis but it will take 100- 1000 cells of salmonella to cause salmonellosis u It also refers to strains of a single species that are capable of causing the disease u Virulent: strains that can cause disease on infection u ....................: strains that will not cause disease upon infection u E.g. Strains of Staphylococcus pneumoniae that are encapsulated are virulent while non-encapsulated strains are avirulent. u Virulence factors: u the morphological and physiological properties of pathogens that allow it to cause a disease u Many have been studied in detail and can be target of antimicrobial drugs
extent of disease that can be caused by a pathogen Avirulent
chain of infection
infectious agent, reservoir, portal of exit, mode of transmission, portal of entry, susceptible host
Diphtheria toxin
inhibits protein synthesis
entero
intestine
Results in septicemia (chills and very high fever,), shock (very low blood pressure) Most commonly caused by
lipopolysaccharides of Gram- negative bacteria endotoxins
Types of infection
local, systemic, acute, chronic Latent infection , secondary infection
u An infection is a disease caused by a
microorganism u Also called *infectious disease* focus on *ous*
tetanospasmin
neurotoxin causes paralysis by binding to motor nerve endings; blocking the release of neurotransmitter for muscular contraction inhibition; muscles contract uncontrollably
affect the central nervous system - E.g. tetanospasmin التيتانوسبازمين produced by Clostridium tetani كلوستريديوم الكزازية
neurotoxins
The Infectious Process Can be divided into 4 steps: 1.Incubation period: -the time between when the pathogen enters the body and when symptoms of the disease appear -Length varies due many factors 2.Prodormal period: -A time when a person is ........... but before the actual symptoms show up 3.Period of illness: -The time when ......... of the disease are obvious -Actual length can vary from individual to individual -........most often happens at this period 4.Convalescent period: -The time when an individual .......from the illness -Time can vary and can be quiet long for illness caused by viruses
not feeling well actual symptoms Transmission recovers
Types of infection Localized infection: disease remains in ....... of infection -Infection can spread to other areas if not stopped at the site u Systemic infection: infection spreads to ..... u Acute disease: -Starts very .....and is usually severe -short period -relatively quick recovery u Chronic disease: -disease starts .... -Lasts a long time -E.g. tuberculosis, leprosy 5...........infection- عدوى كامنة Refers to the condition when an individual is exposed to a pathogen but does not develop the disease Also when an infectious disease stops producing the symptoms for a period of time However symptoms show up again after a period of time. E.g. Herpes virus that causes cold sores. Secondary infection: when a second disease is caused by after a first disease E.g. Individuals may develop bacterial pneumonia after getting vrial respiratory infection. Due to damage of the cilliary epithelial cells by the ..........
one site all over the body. quickly slowly 5 Latent virus
Pathogenesis of Microbial Infection u An infection is a disease caused by a microorganism u Also called infectious disease u The organism causing the infectious disease is called a _____________,______________ u There are two types of pathogens: - - u These can be any one of the following: u Viruses u Bacteria u Fungi u Protists u Microscopic multicellular organisms u Certain guidelines are needed to establish whether a disease is caused by an infectious agent
pathogen or an infectious agent u Extracellular (live and multiply in outside host tissue cells in the extracellular fluid) u Intracellular (live and multiply inside host's cell)
Latent
present, but not active; hidden Types of infection Latent infection- عدوى كامنة Refers to the condition when an individual is exposed to a pathogen but does not develop the disease Also when an infectious disease stops producing the symptoms for a period of time However symptoms show up again after a period of time. E.g. Herpes virus that causes cold sores.
infectious agent, ___________, portal of ______, mode of transmission, portal of entry, ______________
reservoir=مكان الممرض الفيروس مثلا مكانها في البراز مثلا البراز يعتبر ريزرفور exit يطلع بعدين ينتقل علشان يدخل, علشان اسميها عدوى susceptible host
prodormal period
second stage of infection; first signs of illness begin to appear
Steps in pathogenesis u Attachment -Pathogen has to attach u Multiplication -After successful attachment, a pathogen ........... -May multiply at a single location (...................) -Can continue to multiply in even larger numbers and spread (.......................) u Invasion of host tissues -Refers to the spread of the pathogen -Can only happen when ......
to body tissues or penetrate into a cell إلى أنسجة الجسم أو تخترق الخلية -Many mechanisms present in pathogens عندها ادوات فيلاي كابسل فلاقيلا many clones -May multiply at a single location (localized infection) -Can continue to multiply in even larger numbers and spread (systemic infection) pathogen multiplies into large numbers -Transmission -Entry of pathogen -Attachment to host tissue cells -Multiplication -Invasion -Evading host defenses -Damage to host tissues or toxinogenecity
Neurotoxins
toxic substances, such as lead or mercury, that specifically poison nerve cells
Virulence factors in bacteria
u Attachment factors -Receptors and Adhesin -Bacterial fimbrae (pilli) -Capsules -Flagella u Enzymes -Exoenzymes -Nectrotizing enzymes -Coagulase -Kinases -Collagenase -Hemolysins u Toxins -Endotoxins -Exotoxins
transfusion u Inoculation
u Directly into the blood through blood transfusion or infected syringe u Inoculation into tissue by arthropod
-Can only happen when pathogen multiplies into large numbers
u Invasion of host tissues
INFECTIOUS DISEASE Any microorganism that can cause a disease such as a bacterium, virus, parasite, or fungus. Reasons that the organism will cause an infection are v i p
virulence (ability to multiply and grow), invasiveness (ability to enter tissue) , and pathogenicity (ability to cause disease).
penetration
يكسر خط الدفاع الاول Transmission and entry of pathogen: u Several parts of the body through which a pathogen can enter. u Penetration through the skin or mucous membrane
Mode of action of Dipheria toxin
•Inhibition of protein synthesis •Hypersecretion •Inhibition of neurotransmitter release