This document discusses types of infections and their classification. It covers primary infections caused by initial exposure to a pathogen. Reinfections occur when exposed to the same pathogen after recovery. Secondary infections happen when immunity is lowered allowing a new pathogen to invade. Focal infections are localized, while nosocomial infections are acquired in hospitals. Factors like drugs, medical equipment, and commensal bacteria turning pathogenic can lead to iatrogenic or endogenous infections. Exogenous infections come from external sources. Latent infections involve pathogens hiding in tissues.

1. Types of infection
• Primary
• Reinfection Secondary
• Focal infection
• Nosocomial infection
• Iatrogenic infection
• Endogenous
• Exogenous
• Inapparent/subclinical
• Atypical
• Latent
• Local
• Systemic

2. --=
• Primary infection
• Exposure of pathogen for the first time
• Reinfection
• Exposure of the same pathogen for second or many
times.
• Secondary
• Infected by a pathogen, immunity lowered and cause
invasion by other pathogen

3. • Focal infection
• Localised infection
Nosocomial infection
• A person make a hospital visit, immunity is low, and get
infected by hospital micro1
bes.
• Eg: wou nd sepsis

4. • Iatrogenic infection
• Drug induced infection during course of treatment
• Eg: muscle sepsis caused by unsterilized equipmen t used.
• Endogenous infectiom
• When a commensal enter places it should not be.
• Eg: entrance of E. coli to urinary tract cause infection.
• Exogenous infection
• When a pathogen comes from other source
• Eg: soil

5. • Inapparent /subclinical
• Asymptomatic
• Atypical infection
• Symptoms are atypical
• Latent infection
• Parasites remains in tissues in latent or hidden form,
proliferating and producing clinical disease when the host
resistance is lowered.
• Eg: herpes infection

6. • Systemic infection
• Spread throughout the body
• Eg: streptococcus infection

7. 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

8. Microcolonies
• Biofilms of the
different types of
bacteria
Infection is the
lodgement and
multiplication of
organism in the
tissue of host

9. Classification of infections
1. Primary infection: Initial infection
organism in host.
with
2. Reinfection: Subsequent infection by
same organism in a host (after recovery).
3. Superinfection:Infection by
same organism in a host before recovery.
organism may set up in infection.
4. Secondary infection: When in a host
whose resistance is lowered by
preexisting infectious disease, a new

10. 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.

11. Causative agents of infections
• Saprophy tes: 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.

12. 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
pathogen in his body.
Anthroponosis
harbor the

13. 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),
protozoa!, (e.g. Leishmaniasis from dogs),
helminthic, (e.g. Hydatid cyst from dogs)
and fungal (zoophilic dermatophytes from
cats and dogs).

14. 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
called
called
by housefly) and these are
mechanical vector. They are
biological vector if pathogen
multiplies in the body of vector,
Anopheles mosquito in Malaria.
e.g.

15. Sources of infection in Man
Some vectors may acts as 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.
C/ostridium tetani -

16. Sources of infection in Man
Water: Vibrio cholerae,
infective
(
Hepatitis
Hepatitis
hepatitis virus
A and
E) may be
found water.
Food: Contaminated food
of
may be source
infection. Presence of
pathogens in food may
be due to external
(e.g.
contamination,
food poisoning by
Staphylococcus ).

17. Methods of transmission of
infection
• Contact (sexual
intercourse): syphilis,
gonorrhea.
• Inhalation: influenza,
tuberculosis,
smallpox,
measles,
mumps, etc.

18. Methods of transmission of
infection
• Ingestion:
(water), food
(food) and
(hand borne).
• Inoculation:
cholera
poisoning
dysentery
tetanus
(infection), rabies (dog),
arbovirus (insect) and
serum hepatitis, i.e.
Hepatitis B (infection).
Human hand
contaminated with
colonies of bacteria
{blue/pink patches)