infection and its classification

1. ALAA ABD ELMAN AM ALI ELN AGAR
BACTERIAL INFECTION
Level Three
Microbiology Department

2. ‫الرحيم‬ ‫الرحمن‬ ‫هللا‬ ‫بسم‬

3. CONTENT
 Classification of infections.
 Types of bacterial pathogen
 Factors of Virulence.
 Streptococcal infections.
 Alpha-hemolytic Streptococci.
 Beta-hemolytic Streptococci.
 Scarlet Fever.
 Bacterial Meningitis.
 Staphylococcal infections.
 Skin and soft tissue infections.
 Invasive infections.

4. CLASSIFICATION OF INFECTIONS
Infection is the lodgment and multiplication of organism in the tissue of host.
 Primary infection: Initial infection with organism in host.
 Reinfection: Subsequent infection by same organism in a host (after
recovery).
 Superinfection: Infection by same organism in a host (before
recovery).
 Secondary infection: When in a host whose resistance is lowered by
preexisting infectious disease, a new organism may set up in
infection.
 Focal infection: It is a condition where due to infection at localized
sites like appendix and tonsil, general effects are produced.
 Cross infection: When a patient suffering from a disease and new
infection it set up from another host or external source.
 Nosocomial infection: Cross infection occurring in hospital.

5. TYPES OF BACTERIAL PATHOGEN
Bacterial pathogens
can be classified into
two broad groups:
 Opportunistic pathogens
Rarely cause disease
 Primary pathogens
Can establish infection and
cause disease

6. 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 .

8. Colonization: the establishment of stable population of bacterial in the host. Its
requires adhesion to mucosal cell surface, it is necessary to avoid innate host
defence mechanisms
Communicability is the ability of parasite to spread from one host to another. It
determines the survival and distribution of organism in a community.
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).

9. Toxigenicity: Bacteria produce two types of toxins – exotoxins &
endotoxins.
Toxemia: Presence of toxins in the blood.
Toxin effects: May include fever, cardiovascular problems, diarrhea, shock,
destruction of red blood cells and blood vessels, and nervous system
disruptions.

10. Collagenase: Breaks down collagen which forms connective tissue of
muscles, skin, and other organs. Produced by several clostridia.
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.
Hemolysin is produced by some organisms capable of destroying
erythrocytes.
Hyaluronidase split hyaluronic acid (component of connective tissue).
Bacterial Kinases: Break down clots produced by body to isolate infection.
Made by streptococci and staphylococci.
Proteases: Break down proteins in tissue.

11. STREPTOCOCCAL INFECTIONS
Streptococcal infections are any type
of infection caused by the group of
bacteria Streptococcus.
Streptococcus is a genus of gram-
positive coccus.
Streptococcal infections are primarily
treated with antibiotics.
Streptococci are divided into two key
groups:
 alpha (α)-haemolytic Streptococci.
 beta (β)-haemolytic Streptococci.

12. • Alpha-hemolytic
Streptococci
• When alpha hemolysis (α-
hemolysis) is present, the agar
under the colony will appear
dark and greenish due to the
conversion of hemoglobin to
green biliverdin.
• Alpha-hemolysis is also
termed incomplete hemolysis
and partial hemolysis because
the cell membrane of the red
blood cells are left intact. This
is also sometimes called
green hemolysis because of
the color change in the agar.
• Beta-hemolytic
Streptococci
• Beta hemolysis (β-hemolysis),
sometimes called complete
hemolysis, is a complete lysis of
red cells in the media around and
under the colonies. the area
appears lightened (yellow) and
transparent.
• Streptolysin, an exotoxin, is the
enzyme produced by the bacteria
which causes the complete lysis
of red blood cells.

14. Scarlet Fever

15. Bacterial Meningitis

17. STAPHYLOCOCCAL INFECTIONS
Staphylococcal infections are a group of
infections caused by the bacterium
Staphylococcus. Infection causes a range of
symptoms, from skin conditions to food
poisoning. Nosocomial infection and
secondary infections (influenza).
Staphylococcus is a genus of Gram-positive
bacteria.
The most common of this group of bacteria is
Staphylococcus aureus.
Staphylococcal infections are spread by skin-
to-skin contact and often start by infecting
small cuts in the skin.
Depending on how far the bacterium gets into
the body, Staphylococcal infections are
usually divided into two groups:
 skin and soft tissue infections.
 invasive infections.

18. SKIN AND SOFT TISSUE INFECTIONS
Skin and soft tissue Staphylococcal
infections include:
Boils: painful, red bumps on the skin of
the neck, face, thighs, armpits and
buttocks
Impetigo: a highly contagious bacterial
skin infection causing painful sores and
painless blisters
Cellulitis: a bacterial infection of the deep
layer of the skin and the layer of fat and
soft tissue beneath the skin. This can
cause patients to feel feverish and
nauseous.
Folliculitis: is the infection and
inflammation of one or more hair follicles.

20. INVASIVE INFECTIONS
Invasive Staphylococcal infections include:
Sepsis: also known as blood poisoning, this
happens when Staphylococcal infections enter
the blood stream causing an overwhelming
immune response.
 Symptoms include fever, fast heartbeat, low
blood pressure, diarrhea, pale and cold skin,
and sometimes loss of consciousness.
Sepsis is a medical emergency.
Endocarditis: this is when Staphylococcus
infects the internal structures of the heart (for
example, the heart valves), causing
inflammation (An immune reaction that results
in localized redness, warmth and swelling. It
generally occurs in response to an infection,
irritation or injury).

21. Thanks