The document provides an introduction to medical microbiology, defining key terms like pathology, infection, and disease. It describes different types of infections such as primary and secondary infections, as well as acute, chronic, and subclinical infections. The document also outlines various sources and contexts of infections like nosocomial, iatrogenic, congenital, and laboratory acquired infections.

1. Introduction to Medical
Microbiology
Dr.S.Dhiva
Assistant Professor,
Department of Microbiology,
S.N.College, Alathur

2. Pathology
• Scientific study of disease
• Patho- suffering, Logo- Science
• It is concerned with
• cause or etiology of diseases and
• pathogenesis, the Manner in which a disease develops
• Structural and functional changes brought about by the disease
• Final effects on the body

3. • The invasion or colonization of the body by the pathogenic
microorganism
• In other words, infection can be defined as the presence of a
particular type of microorganism in a part of body where it is not
normally found is called infection
Infection

4. Disease
• Disease occurs when an infection results in any change from a state of Health
• It is an abnormal state in which a part or all of the body is not properly adjusted or
incapable of performing in normal function
• An infection may exist in the absence of detectable disease
• Ex: A body may be infected with virus that causes AIDS, but there may be no
symptoms of the disease

5. TYPES OF INFECTION
• 1. PRIMARY INFECTION
• 2. SECONDARY INFECTION
• 3. SUBCLINICAL INFECTION OR INAPPARENT INFECTION

6. OTHERWISE…..
• ACUTE INFECTION
• CHRONIC INFECTION
• CROSS INFECTION
• ENDOGENOUS
INFECTION/DISEASE
• EXOGENOUS INFECTION/DISEASE
• NOSOCOMIAL INFECTION
• IATROGENIC INFECTION
• CONGENITAL INFECTION/DISEASE
• TERATOGENIC INFECTION
• LABORATORY INFECTION
• LATENT INFECTION
• LOCAL INFECTION/DISEASE
• SYSTEMIC INFECTION/DISEASE

7. TYPES OF INFECTION
• PRIMARY INFECTION: It is an acute infection that causes intial illness
• SECONDARY INFECTION: It is caused by an opportunistic pathogens after the
primary infection, that has weekened the body’s defences
• Secondary infection of skin is very common and sometimes dangerous than primary
infection
• Ex.
• Pneumocystis pneumonia in AIDS patient
• Streptococcal bronchopneumonia in Influenza patients

8. Subclinical infection or Inapparent infection
• Subclinical infection is one that doesn’t cause any noticeable illness
• Example: Poliovirus and Hep- A- Virus can be carried by people who
never develop the illness
• Chronic Disease:
• It develops more slowly and but disease is likely to be continual or
recurrent for long periods
• Ex. Infectious mononucleosis, Hep B, TB
• Acute Disease:
• Develops rapidly but lasts only a short time

9. • Sub - acute Disease:
A disease that is intermediate between acute and chronic
Ex. Sclerosing pan encephalitis, a rare brain disease characterized
by diminished Intellectual function
Acute infection:
• An Infection characterized by sudden onset, rapid progression and
often with severe symptoms
Chronic Infection:
• An Infection characterized by delayed onset and slow progression
Cross infection:
• Already suffering from a disease and acquire new disease from another
host or another external sources

10. Endogenous Infection/Disease:
Type or kind of infection or disease originates within the body
Endo – Inside, Genous – Type or Kind
Ex. Metabolic disorders, Congenital ( in born) abnormalities, Tumors, etc.,
Exogenous Disease:
• Kind of disease or infection originates out side the body Ex. Chemical agents,
Electrical shock, trauma
Nosocomial infection:
• Hospital acquired infection
• Infection transmitted by Health care workers
Iatrogenic Infection:
Physician induced infection during therapeutic or investigative procedure

11. Congenital disease:
Disease develops due to hereditary disorder, may be inborn Ex. Leucoderma,
Heart diseases, etc.,
Teratogenic infection:
• Infection due to teratogens, an agent that can disturb the development of
an embryo or fetus
• It can cause birth defects in child ex. Radiation, Maternal infection,
chemicals or drugs
Laboratory infection:
• Infection acquired through lab or lab related activities regardless it may be
symptomatic or asymptomatic

12. Latent Infection:
After following an infection the pathogen remains in tissues in a hidden
or latent form which produce clinical disease when the host resistance is
lowered