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INFECTION AND INFECTIOUS
PROCESS
1 Infection. Classification of
infections
2 Sources of infection in
Man
3 Methods of transmission
of infection
4 Factors predisposing to
microbial pathogenicity
5 Types of infectious
diseases
Infection is the
lodgement and
multiplication of
organism in the
tissue of host
Biofilms of the different
types of bacteria
Microcolonies
Classification of infections
1 Primary infection: Initial infection with
organism in host.
2 Reinfection: Subsequent infection by
same organism in a host (after recovery).
3 Superinfection: Infection by same
organism in a host before recovery.
4 Secondary infection: When in a host
whose resistance is lowered by preexisting
infectious disease, a new organism may
set up in infection.
Classification of infections
5. Focal infection: It is a condition where due
to infection at localized sites like appendix
and tonsil, general effects are produced.
6. Cross infection: When a patient suffering
from a disease and new infection it set up
from another host or external source.
7. Nosocomial infection: Cross infection
occurring in hospital.
8. Subclinical infection: It is one where
clinical affects are not apparent.
Causative agents of infections
• Saprophytes: They are free living organisms
which fail to multiply on living tissue and so
are not important in infectious disease.
• Parasites: They are organisms that can
establish themselves and multiply in hosts.
They may be pathogens or commensal.
Pathogens are those which are capable of
producing disease in a host. On the contrary
commensal microbes can live in a host
without causing any disease.
Sources of infection in Man
Man: Man is himself a common source of
infection from a patient or carrier. Healthy
carrier is a person harboring pathogenic
organism without causing any disease to
him. A convalescent carrier is one who
has recovered from disease but
continues to harbor the pathogen in his
body.
Anthroponosis
Sources of infection in Man
Animals: Infectious diseases transmitted
from animals to man are called zoonosis.
Zoonosis may be bacterial, (e.g. Plague
from rat), rickettsial, (e.g. Murine typhus
from rodent), viral, (e.g. Rabies from dog),
protozoal, (e.g. Leishmaniasis from dogs),
helminthic, (e.g. Hydatid cyst from dogs)
and fungal (zoophilic dermatophytes from
cats and dogs).
Sources of infection in Man
Insects: The diseases caused by insects
are called arthropod borne disease.
Insects like mosquitoes, fleas, lice that
transmit infection are called vector.
Transmission may be mechanical
(transmission of Dysentery or typhoid
bacilli by housefly) and these are called
mechanical vector. They are called
biological vector if pathogen multiplies
in the body of vector, e.g. Anopheles
mosquito in Malaria.
Sources of infection in Man
Some vectors may acts aas ‫مستودع‬
‫العائل‬
reservoir host, (e.g. ticks in
Relapsing fever and Spotted fever).
Soil: Spores of tetanus bacilli, Gas-
gangrene infection remain viable in
soil for a long time.
Clostridium tetani
Sources of infection in Man
Water: Vibrio cholerae,
infective hepatitis virus
(Hepatitis A and
Hepatitis E) may be
found water.
Food: Contaminated food
may be source of
infection. Presence of
pathogens in food may
be due to external
contamination, (e.g. food
poisoning by
Staphylococcus).
Methods of transmission of
infection
• Contact (sexual
intercourse):
syphilis, gonorrhea.
• Inhalation:
influenza,
tuberculosis,
smallpox, measles,
mumps, etc.
Methods of transmission of
infection
• Ingestion: cholera
(water), food poisoning
(food) and dysentery
(hand borne).
• Inoculation: tetanus
(infection), rabies (dog),
arbovirus (insect) and
serum hepatitis, i.e.
Hepatitis B (infection).
Human hand
contaminated with
‫مستعمرات‬
‫البكتيريا‬ colonies
of bacteria
(blue/pink patches)
Methods of transmission of
infection
• ‫االبتالع‬: ‫)الماء(الكوليرا‬ ‫والتسمم‬
‫الغذائي‬ (‫)الغذاء‬
• ‫والدوسنتاريا‬ ( ‫المحمولة‬
‫باليد‬ ).‫التلقيح‬: ‫)العدوى(الكزاز‬،
• ‫وداء‬
‫الكلب‬ (‫)الكلب‬
• ،
‫والفيروسات‬ (‫)الحشرة‬ ‫والتهاب‬
‫الكبد‬
• ‫في‬
‫الدم‬
،
‫أي‬
‫التهاب‬
‫الكبد‬ B (‫)العدوى‬.
Methods of transmission of
infection
• Congenital:
syphilis,
rubella,
toxoplasmosis,
cytomegaloviruses
Eight week old fetus
attached to its placenta by
the umbilical cord
Methods of transmission of
infection
• Insects: they act as
mechanical vector
(dysentery and typhoid
by housefly) or
biological vector
(malaria) of infectious
disease
• Jatrogenic and
laboratory infections:
infection may be
transmitted during
procedures
Characters of pathogens
• Bacteria should be able to enter the body.
• Organism should be able to multiply in
the tissue.
• They should be able to damage the
tissue.
• They must be capable to resist the host
defense.
Pathogenecity is referred to the ability of
microbial species to produce disease.
Virulence is referred to the ability of microbial
strains to produce disease.
Factors of Virulence
• Adhesion: The initial event in the
pathogenesis of many infections is the
attachment of the bacteria to body surfaces.
This attachment is specific reaction between
surface receptors and adhesive structures on
the surface of bacteria (adhesins).
Adherence of bacteria
Factors of Virulence
• Invasiveness is the ability of
organism to spread in a host tissue
after establishing infection. Less
invasive organisms cause localized
lesion. Highly invasive organisms
cause generalized infection
(septicemia).
• Toxigenicity. Bacteria produce two
types of toxins – exotoxins &
endotoxins
Factors of Virulence - Exotoxins
• Heat labile protein.
• Diffuse readily into the surrounding medium.
• Highly potent, e.g. 3 kg botulinum can kill all the
inhabitants of world.
• They are generally formed by Gr+ bacteria and also
by Gr- organisms like Shigella, V.cholerae, E.coli.
• Exotoxin is specifically neutralized antitoxin.
• Can be separated from culture by filtration.
• Action is enzymatic and it has specific tissue
affinity.
• Specific pharmacological effects for each
exotoxin.
• Cannot cause pyrexia in a host.
• Can be toxoided.
Modification of Toxin to Toxoid
chemical
modification
Toxoid
toxin moiety antigenic determinants
Toxin
Factors of Virulence -
Endotoxins
• Endotoxin (lipid a portion of lypopoly-
saccharide) has biological activities
causing fever, muscle proteolysis,
uncontrolled intravascular coagulation and
shock.
• These may be mediated by production
from mononuclear cells of IL-1, probably
IL-6.
Characters of Endotoxins
• Proteins polysaccharide lipid complex heat stable.
• Forms part of cell wall (don’t diffuse into the
medium).
• Obtained only by cell lysis.
• They have no enzymatic action.
• Effect is non-specific action.
• No specific tissue affinity.
• Active only in large doses 5 to 25 mg.
• Weakly antigenic.
• Neutralization by antibody ineffective.
• Cannot be toxoided.
• Produce in Gram negative bacteria.
Factors of Virulence
• Communicability is the ability of parasite to
spread from one host to another. It
determines the survival and distribution of
organism in a community.
• Coagulase (S.aureus) which prevents
phagocytosis by forming fibrin barrier
around bacteria.
• Fibrinolysin promotes the spread of
infection by breaking down the fibrin
barrier in tissues.
Factors of Virulence
• Hyaluronidase split hyaluronic acid
(component of connective tissue).
• Leucocidins damage polymorphonuclear
leucocytes.
• Ig A1 proteases: split IgA and inactivates
its antibody activity.
• Hemolysin is produced by some
organisms capable of destroying
erythrocytes.
Factors of Virulence. Bacterial
appendages
Capsulated bacteria
like
Pneumococcus,
K.pneumoniae and
H.influenzae stand
phagocytosis
Surface antigen, e.g. Vi-antigen of S. typhi and K-
antigen of E.coli resisted phagocytosis and lytic
activity of complement.
Infecting dose
• The minimum infection dose (MID) or
minimum lethal dose (MLD) is the
minimum number of organism required to
produce clinical evidence of infection or
dearth of susceptible animal.
• Route of infection
• Vibrio cholerae is effective orally. No effect
when it is introduced subcutaneously.
• Streptococci can initiate infection whatever
be the mode of entry.
Types of infectious diseases
• Infectious diseases may be localized or
generalized. Localized infections may be
superficial or deep-seated.
• Circulation of bacteria in the blood is
known as bacteremia (viruses – virusemia).
Types of infectious diseases
• Septicemia is the condition where
bacteria circulate and multiply in the
blood, form toxic products and cause
swinging type of fever.
• Pyemia is a condition where pyogenic
bacteria produce septicemia with
multiple abscesses in the internal organs
such as the spleen, liver and kidney.
Types of infectious diseases
• Depending on the spread of infectious
disease in the community they may be
classified into different types.
• Endemic diseases are ones that are
constantly present in a particular area.
Typhoid fever is endemic in most parts of
India. An epidemic disease is one that
spreads rapidly, involving many persons in
an area at the same time. Influenza
causes annual winter epidemics in the
cold countries.
Types of infectious diseases
• A pandemic is an epidemic that spreads through
many areas of the world involving very large
numbers of persons within a short period
(Influenza, cholera, plaque).
• Epidemics vary in the rapidity of spread.
Waterborne disease such as cholera and
hepatitis may cause explosive outbreaks, while
disease, which spreads by person-to-person
contact evolve more slowly.
Stages of infectious disease
• Incubation period – no symptoms.
• Prodromal period – mild and
generalized symptoms (fever,
weakness, headache).
• Invasive stage – symptoms specific to
the disease.
• Decline stage – symptoms subside.
• Convalescence – no symptoms,
health returns to normal.
Biofilms
• Biofilms form when bacteria adhere to surfaces in
aqueous environments and begin to excrete a slimy,
glue-like substance that can anchor them to all kinds
of material (metals, plastics, medical implant
materials and, human or animal tissue).
Hundreds of microbial biofilm colonize the human mouth,
causing tooth decay and gum disease.
Quorum Sensing
Many groups of bacteria can communicate - by
releasing and detecting chemical pheromones to
gauge their population density - the molecular
structure of a key protein in this interbacterial
communication has been solved.
Quorum sensing provides an explanation for why
some disease-causing virulence factors are not
expressed during the early stages of encounter with
the human host
Characteristics of biofilm
• A biofilm can contain a single species of
bacteria or several species.
• Genetic studies confirm that bacteria switch
on different genes, depending on whether
they're living as free-floating microbes or
clustering as biofilms.
• Biofilm bacteria can be up to 1000 times
more resistant to antimicrobial stress (e.g.
antibiotics and disinfectants) than free-
swimming bacteria of the same species.
• Plaque is a biofilm on the surfaces of the
teeth which secretes acids that destroy
teeth and gums
Dental plaque as
seen under a
scanning electron
microcroscope
5 stages of P.aeruginosa biofilm development
1, initial attachment; 2, irreversible attachment;
3, 4 - maturation ; 5, dispersion.
Living bacteria
Biofilm communities are responsible for much of the
biological activity attributed to bacteria in the wide range
of habitats occupied by these biochemically complex
microorganisms
These
communities
represent a
higher order
of structure
and function
than is found
when bacteria
are grown in
broth culture

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INFECTION AND INFECTIOUS PROCEعمللياSS.pptx

  • 1. INFECTION AND INFECTIOUS PROCESS 1 Infection. Classification of infections 2 Sources of infection in Man 3 Methods of transmission of infection 4 Factors predisposing to microbial pathogenicity 5 Types of infectious diseases
  • 2. Infection is the lodgement and multiplication of organism in the tissue of host Biofilms of the different types of bacteria Microcolonies
  • 3. Classification of infections 1 Primary infection: Initial infection with organism in host. 2 Reinfection: Subsequent infection by same organism in a host (after recovery). 3 Superinfection: Infection by same organism in a host before recovery. 4 Secondary infection: When in a host whose resistance is lowered by preexisting infectious disease, a new organism may set up in infection.
  • 4. Classification of infections 5. Focal infection: It is a condition where due to infection at localized sites like appendix and tonsil, general effects are produced. 6. Cross infection: When a patient suffering from a disease and new infection it set up from another host or external source. 7. Nosocomial infection: Cross infection occurring in hospital. 8. Subclinical infection: It is one where clinical affects are not apparent.
  • 5. Causative agents of infections • Saprophytes: They are free living organisms which fail to multiply on living tissue and so are not important in infectious disease. • Parasites: They are organisms that can establish themselves and multiply in hosts. They may be pathogens or commensal. Pathogens are those which are capable of producing disease in a host. On the contrary commensal microbes can live in a host without causing any disease.
  • 6. Sources of infection in Man Man: Man is himself a common source of infection from a patient or carrier. Healthy carrier is a person harboring pathogenic organism without causing any disease to him. A convalescent carrier is one who has recovered from disease but continues to harbor the pathogen in his body. Anthroponosis
  • 7. Sources of infection in Man Animals: Infectious diseases transmitted from animals to man are called zoonosis. Zoonosis may be bacterial, (e.g. Plague from rat), rickettsial, (e.g. Murine typhus from rodent), viral, (e.g. Rabies from dog), protozoal, (e.g. Leishmaniasis from dogs), helminthic, (e.g. Hydatid cyst from dogs) and fungal (zoophilic dermatophytes from cats and dogs).
  • 8. Sources of infection in Man Insects: The diseases caused by insects are called arthropod borne disease. Insects like mosquitoes, fleas, lice that transmit infection are called vector. Transmission may be mechanical (transmission of Dysentery or typhoid bacilli by housefly) and these are called mechanical vector. They are called biological vector if pathogen multiplies in the body of vector, e.g. Anopheles mosquito in Malaria.
  • 9. Sources of infection in Man Some vectors may acts aas ‫مستودع‬ ‫العائل‬ reservoir host, (e.g. ticks in Relapsing fever and Spotted fever). Soil: Spores of tetanus bacilli, Gas- gangrene infection remain viable in soil for a long time. Clostridium tetani
  • 10. Sources of infection in Man Water: Vibrio cholerae, infective hepatitis virus (Hepatitis A and Hepatitis E) may be found water. Food: Contaminated food may be source of infection. Presence of pathogens in food may be due to external contamination, (e.g. food poisoning by Staphylococcus).
  • 11. Methods of transmission of infection • Contact (sexual intercourse): syphilis, gonorrhea. • Inhalation: influenza, tuberculosis, smallpox, measles, mumps, etc.
  • 12. Methods of transmission of infection • Ingestion: cholera (water), food poisoning (food) and dysentery (hand borne). • Inoculation: tetanus (infection), rabies (dog), arbovirus (insect) and serum hepatitis, i.e. Hepatitis B (infection). Human hand contaminated with ‫مستعمرات‬ ‫البكتيريا‬ colonies of bacteria (blue/pink patches)
  • 13. Methods of transmission of infection • ‫االبتالع‬: ‫)الماء(الكوليرا‬ ‫والتسمم‬ ‫الغذائي‬ (‫)الغذاء‬ • ‫والدوسنتاريا‬ ( ‫المحمولة‬ ‫باليد‬ ).‫التلقيح‬: ‫)العدوى(الكزاز‬، • ‫وداء‬ ‫الكلب‬ (‫)الكلب‬ • ، ‫والفيروسات‬ (‫)الحشرة‬ ‫والتهاب‬ ‫الكبد‬ • ‫في‬ ‫الدم‬ ، ‫أي‬ ‫التهاب‬ ‫الكبد‬ B (‫)العدوى‬.
  • 14. Methods of transmission of infection • Congenital: syphilis, rubella, toxoplasmosis, cytomegaloviruses Eight week old fetus attached to its placenta by the umbilical cord
  • 15. Methods of transmission of infection • Insects: they act as mechanical vector (dysentery and typhoid by housefly) or biological vector (malaria) of infectious disease • Jatrogenic and laboratory infections: infection may be transmitted during procedures
  • 16. Characters of pathogens • Bacteria should be able to enter the body. • Organism should be able to multiply in the tissue. • They should be able to damage the tissue. • They must be capable to resist the host defense.
  • 17. Pathogenecity is referred to the ability of microbial species to produce disease. Virulence is referred to the ability of microbial strains to produce disease.
  • 18. Factors of Virulence • Adhesion: The initial event in the pathogenesis of many infections is the attachment of the bacteria to body surfaces. This attachment is specific reaction between surface receptors and adhesive structures on the surface of bacteria (adhesins).
  • 20. Factors of Virulence • Invasiveness is the ability of organism to spread in a host tissue after establishing infection. Less invasive organisms cause localized lesion. Highly invasive organisms cause generalized infection (septicemia). • Toxigenicity. Bacteria produce two types of toxins – exotoxins & endotoxins
  • 21.
  • 22. Factors of Virulence - Exotoxins • Heat labile protein. • Diffuse readily into the surrounding medium. • Highly potent, e.g. 3 kg botulinum can kill all the inhabitants of world. • They are generally formed by Gr+ bacteria and also by Gr- organisms like Shigella, V.cholerae, E.coli. • Exotoxin is specifically neutralized antitoxin. • Can be separated from culture by filtration. • Action is enzymatic and it has specific tissue affinity. • Specific pharmacological effects for each exotoxin. • Cannot cause pyrexia in a host. • Can be toxoided.
  • 23. Modification of Toxin to Toxoid chemical modification Toxoid toxin moiety antigenic determinants Toxin
  • 24. Factors of Virulence - Endotoxins • Endotoxin (lipid a portion of lypopoly- saccharide) has biological activities causing fever, muscle proteolysis, uncontrolled intravascular coagulation and shock. • These may be mediated by production from mononuclear cells of IL-1, probably IL-6.
  • 25. Characters of Endotoxins • Proteins polysaccharide lipid complex heat stable. • Forms part of cell wall (don’t diffuse into the medium). • Obtained only by cell lysis. • They have no enzymatic action. • Effect is non-specific action. • No specific tissue affinity. • Active only in large doses 5 to 25 mg. • Weakly antigenic. • Neutralization by antibody ineffective. • Cannot be toxoided. • Produce in Gram negative bacteria.
  • 26. Factors of Virulence • Communicability is the ability of parasite to spread from one host to another. It determines the survival and distribution of organism in a community. • Coagulase (S.aureus) which prevents phagocytosis by forming fibrin barrier around bacteria. • Fibrinolysin promotes the spread of infection by breaking down the fibrin barrier in tissues.
  • 27.
  • 28. Factors of Virulence • Hyaluronidase split hyaluronic acid (component of connective tissue). • Leucocidins damage polymorphonuclear leucocytes. • Ig A1 proteases: split IgA and inactivates its antibody activity. • Hemolysin is produced by some organisms capable of destroying erythrocytes.
  • 29.
  • 30. Factors of Virulence. Bacterial appendages Capsulated bacteria like Pneumococcus, K.pneumoniae and H.influenzae stand phagocytosis Surface antigen, e.g. Vi-antigen of S. typhi and K- antigen of E.coli resisted phagocytosis and lytic activity of complement.
  • 31. Infecting dose • The minimum infection dose (MID) or minimum lethal dose (MLD) is the minimum number of organism required to produce clinical evidence of infection or dearth of susceptible animal. • Route of infection • Vibrio cholerae is effective orally. No effect when it is introduced subcutaneously. • Streptococci can initiate infection whatever be the mode of entry.
  • 32. Types of infectious diseases • Infectious diseases may be localized or generalized. Localized infections may be superficial or deep-seated. • Circulation of bacteria in the blood is known as bacteremia (viruses – virusemia).
  • 33. Types of infectious diseases • Septicemia is the condition where bacteria circulate and multiply in the blood, form toxic products and cause swinging type of fever. • Pyemia is a condition where pyogenic bacteria produce septicemia with multiple abscesses in the internal organs such as the spleen, liver and kidney.
  • 34. Types of infectious diseases • Depending on the spread of infectious disease in the community they may be classified into different types. • Endemic diseases are ones that are constantly present in a particular area. Typhoid fever is endemic in most parts of India. An epidemic disease is one that spreads rapidly, involving many persons in an area at the same time. Influenza causes annual winter epidemics in the cold countries.
  • 35. Types of infectious diseases • A pandemic is an epidemic that spreads through many areas of the world involving very large numbers of persons within a short period (Influenza, cholera, plaque). • Epidemics vary in the rapidity of spread. Waterborne disease such as cholera and hepatitis may cause explosive outbreaks, while disease, which spreads by person-to-person contact evolve more slowly.
  • 36. Stages of infectious disease • Incubation period – no symptoms. • Prodromal period – mild and generalized symptoms (fever, weakness, headache). • Invasive stage – symptoms specific to the disease. • Decline stage – symptoms subside. • Convalescence – no symptoms, health returns to normal.
  • 37. Biofilms • Biofilms form when bacteria adhere to surfaces in aqueous environments and begin to excrete a slimy, glue-like substance that can anchor them to all kinds of material (metals, plastics, medical implant materials and, human or animal tissue). Hundreds of microbial biofilm colonize the human mouth, causing tooth decay and gum disease.
  • 38. Quorum Sensing Many groups of bacteria can communicate - by releasing and detecting chemical pheromones to gauge their population density - the molecular structure of a key protein in this interbacterial communication has been solved.
  • 39. Quorum sensing provides an explanation for why some disease-causing virulence factors are not expressed during the early stages of encounter with the human host
  • 40. Characteristics of biofilm • A biofilm can contain a single species of bacteria or several species. • Genetic studies confirm that bacteria switch on different genes, depending on whether they're living as free-floating microbes or clustering as biofilms. • Biofilm bacteria can be up to 1000 times more resistant to antimicrobial stress (e.g. antibiotics and disinfectants) than free- swimming bacteria of the same species.
  • 41. • Plaque is a biofilm on the surfaces of the teeth which secretes acids that destroy teeth and gums Dental plaque as seen under a scanning electron microcroscope
  • 42. 5 stages of P.aeruginosa biofilm development 1, initial attachment; 2, irreversible attachment; 3, 4 - maturation ; 5, dispersion.
  • 43.
  • 44. Living bacteria Biofilm communities are responsible for much of the biological activity attributed to bacteria in the wide range of habitats occupied by these biochemically complex microorganisms These communities represent a higher order of structure and function than is found when bacteria are grown in broth culture