The document outlines key concepts related to infection including definitions, classifications, and principles of infection prevention. It defines infection, disease, and infectious disease and describes acute versus chronic infections. It also covers classifications such as primary/secondary infections and local/systemic infections. The chain of infection and its six links - reservoir, portal of exit, mode of transmission, portal of entry, and susceptible host - are explained. Methods of preventing infection by breaking the chain are also summarized.

1. INFECTION

2. LEARNING OUTCOMES
• At the end of this class the student will be
able to:
1. Definition and know the Classification of infection
2. Recognize the Acute Infection Vs. Chronic Infection
3. Describe the Primary Infection, Secondary Infection, Reinfection,
Local/Focal Infection, Systemic Infection, Cross/Exogenous,
Endogenous Infection, Nosocomial Infections
4. Describe the introduction of the pathway of Normal Flora
5. Comprehend the Chain of Infection
6. To know the minimize Risk and Prevention of Infection

3. DEFINITIONS
Infection - The colonization and multiplication of a microbe
in or on the tissues of a host.
- Infecting Microbes seek to use the host's
resources to reproduce, often resulting in disease.
Disease - Any deviation from a condition of good health &
well-being
Infectious - A disease condition caused by the presence or
Disease growth of infectious microorganisms or parasites

4. • Caused by microorganisms like viruses, prions,
bacteria, viroid, parasites and fungi.
• Invasion by and multiplication of pathogenic in a
bodily part or tissue, which may produce
subsequent tissue injury and progress to
manifested disease through cellular or toxic
mechanisms.
• An infection that
• produces symptoms is an apparent infection.
• is active, but does not produce noticeable symptoms, may be
called in apparent, silent, or subclinical
• is inactive or dormant is called a latent infection
INFECTION

5. Conditions Required For
Infection To Spread From One
Person To Another
3 key components
i. One person must be infected with a
microorganism
ii. The other person must be susceptible to
infection with that microorganism
iii. The microorganism must be able to leave the
body of the infected person and enter the body
of the susceptible person.

6. Time Parameters Of
Interaction
• Latency Period = the INCUBATION PERIOD of an infectious disease,
BEFORE symptoms appear
= the interval between exposure to an infectious
organism (stimulus) and the clinical appearance of
disease (response).
• Incubation Period = the time between infection and onset of
symptoms

7. Range of relationships
Saprophytes – Free living microbes
subsisting on dead / decaying organic matter
Commensals – Microbes living in complete
harmony with host without causing any
harm to them.
Parasites – Microbes establishing and
multiplying themselves in hosts.
Pathogens - Microbes capable of causing
disease in host.
Nature Of Microorganisms

8. Definitions - Pathogenicity
& Virulence
–Pathogenicity
• The ability of a microbe to cause disease
• This term is often used to describe or compare species
–Virulence
• The degree of pathogenicity in a microorganism
• used to describe or compare strains within a species
Based on:
• Invasive qualities
• Toxic qualities
• Presence of pili or fimbriae for adhesion
• Ability to avoid host defenses (mutate)

9. Microbial Mechanisms
of Pathogenicity

10. Microbial Virulence Factors

11. Causative Agents Effecting
Humans
 Bacteria
 Viruses
 Fungi
 Protozoa
 Helminths
 Prions
11

13. Defining - The Suffix “-emia”
-emia suffix meaning “presence of an infectious agent”
1. Bacteremia = Presence of infectious bacteria
2. Viremia = Presence of infectious virus
3. Fungemia = Presence of infectious fungus
4. Septicemia = Presence of an infectious agent in
the bloodstream

14. Defining - The suffix “-itis”
-itis meaning “inflammation of”
Examples:
1. Pharyngitis = Inflammation of the pharynx
2. Endocarditis = Inflammation of the heart chambers
3. Gastroenteritis = Inflammation of the
gastrointestinal tract

15. DEFINITIONS
1. Epidemiology
Epidemiology is the study and analysis of the distribution
(who, when, and where) and determinants of health and
disease conditions in defined populations.
2. Communicable Disease
A disease that can be transmitted from one individual to
another
3. Contagious Disease
A communicable disease that is easily spread from one
individual to another
4. Non communicable Disease
A disease that is not transmitted from one individual to
another

16. Definitions: Epidemiological
Terms
1. ENDEMIC - Disease constantly present in particular area
or in a certain percentage of a population
2. EPIDEMIC - spreads rapidly, involves many persons in an
area at a time (E.g. - meningococcal meningitis, Influenza)
3. PANDEMIC - spreads many areas in world involves large
number within short period (E.g. - Cholera, Enterovirus)

17. Classification Of Infection
ACUTE INFECTION VS. CHRONIC INFECTION
Acute Infection
•An infection characterized by sudden onset, rapid
progression, and often with severe symptoms
•However, there is a balance between production
and degradation of molecules e.g. collagen,
extracellular matrix

18. Classification Of Infection
ACUTE INFECTION VS. CHRONIC INFECTION
Chronic Infection
• An infection characterized by delayed onset and slow
progression of healing process
• Why? – the healing process doesn’t occur orderly as by
stages and at the possible duration of the healing period
(take more than 3 months - years)
• E.g. Wound remain in the inflammatory state for longer time.
• Acute and chronic wounds are at opposite sides of a
range of wound healing types that progress which
healed at different rates.

19. 1. Primary Infection
2. Secondary Infection,
3. Reinfection
4. Local/Focal Infection,
5. Systemic Infection
6. Exogenous/Cross Infection
7. Endogenous Infection,
8. Nosocomial Infections
9. Iatrogenic Infection
Classification Of Infection

20. Primary, Secondary,
Reinfection
1. Primary Infection
Initial infection that develops in an healthy individual
2. Secondary Infection
An infection that develops in an individual who is already
infected with a different pathogen
3. Reinfection
Subsequent infection with the same pathogen in same
host

21. Local, Systemic, Cross
4. Localized Infection (focal)
An infection that is restricted to a specific location or
region within the body of the host
5. Systemic Infection
Spread to several regions or areas in the body of the host
6. Cross infection
Already suffering from disease and acquire new disease
from another host or another external sources

22. Local & Systemic –
Signs and Symptoms
4. Localized Infection (focal)
 Inflammation
 Purulent exudate if bacterial infection; serous exudate if viral
 Tissue necrosis
 Lymphadenopathy
 Respiratory effects
5. Systemic Infection
 Fever, fatigue, headache, nausea

23. Hospital Acquired Infection
Nosocomial & Iatrogenic
8. Nosocomial infection
Relating to or being an infection that a patient acquires
while being treated in a hospital /health care facility
(workers to patient).
9. Iatrogenic Infection
Induced unintentionally in a patient by a physician during
therapeutic or investigative procedure

24. Clinical vs. Subclinical
Infection
1. Clinical Infection
An infection with obvious observable or detectable symptoms
2. Subclinical Infection
An infection with few or no obvious symptoms
3. Atypical infection
Typical clinical features of particular infection is not present

25. Principles of Infection
Understanding the basic principles of infection is
essential for any health care worker in any field of
health care.
1. Disease transmission
2. Prevention of disease transmission

26. The Normal Flora of Humans
Types of Symbiosis
1. Mutualism
A symbiotic relationship in which both species benefit
2. Commensalism
A symbiotic relationship in which one species benefits, and the other
species is neither helped nor harmed
3. Parasitism
• A symbiotic relationship in which one species benefits, and the other
species is harmed
• Generally, the species that benefits (the parasite) is much smaller than
the species that is harmed (the host)

28. The Normal Flora of Humans
Normal flora is
PRESENT IN
 skin
 upper respiratory tract
 oral cavity
 intestine, especially large intestine
 vaginal tract
 Very little normal flora in eyes &
stomach

29. Introduction Of A Flora

30. The Normal Flora Is Absent
• Notably absent in most all internal organs
ABSENT IN:
1. lower respiratory tract
2. muscle tissue
3. blood & tissue fluid
4. cerebrospinal fluid
5. peritoneum
6. pericardium
7. meninges

31. Benefits of the normal flora
1. Nutrient production/processing eg
Vitamin K production by E. coli
2. Competition with pathogenic microbes
3. Normal development of the immune sys
4. Normal flora and opportunistic infections
The Normal Flora of Human

32. Modes Of Communicable
Disease Transmission
• Direct contact
• Droplet transmission
• Indirect contact
• Vector-borne
• Nosocomial

33. •Direct contact
•Indirect contacts
 Air
 Objects
•Vectors
Modes Of Pathogen
Transmission

34. Direct Transmission
• Immediate transfer of the disease agent by direct
contact between the infected and the susceptible
individuals
• Occurs through acts such as touching, biting, kissing,
sexual intercourse, or by direct projection (droplet
spread) by coughing or sneezing within a distance of
one meter
• E.g. of diseases AIDS, syphilis, gonorrhea and
common cold

35. 1. Air-borne transmission - transmission of microbial
aerosols to a suitable port of entry, usually the
respiratory tract.
–Microbial aerosols are suspensions of dust or
droplet nuclei made up wholly or in part by
microorganisms - may be suspended and
transmittable for long periods of time
–E.g. of air-borne diseases - tuberculosis, influenza,
Histoplasmosis, and Legionellosis
Indirect Transmission
May be 1 of 3 types: Air-borne, Vehicle-borne Or Vector-borne

36. 2. Vehicle-borne transmission - contaminated objects
(fomites) serve as vehicles, nonliving by which contagious
agents are transferred to a susceptible host
–The agent may or may not have multiplied or
developed on the vehicle
–E.g. of vehicles include toys, handkerchiefs, soiled
clothes, food service utensils, and surgical instruments
–Also water, milk, food (e.g., common vehicles), or
biological products such as blood, serum, plasma,
organs and tissues
Indirect Transmission
May be 1 of 3 types: Air-borne, Vehicle-borne Or Vector-borne

37. 3. Vectors Borne - transmission of animal (nonhuman) that
can transmit an infectious agent to humans
Two types: Mechanical & Biological
• Biological animal vectors: The infectious agent must
incubate in the animal host as part of the agent’s
developmental cycle; eg, the transmission of malaria by
infected mosquitoes
• Mechanical animal vectors: The infectious agent is
physically transmitted by the animal vector, but the
agent does not incubate or grow in the animal; eg, the
transmission of bacteria sticking to the feet of flies
Indirect Transmission
May be 1 of 3 types: Air-borne, Vehicle-borne Or Vector-borne

38. Latent & Opportunistic
Infection
Latent infection-
• After following an infection the pathogen
remain in tissues in a hidden or latent
form which produce clinical disease
when the host resistance is lowered.
Opportunistic infection
–An infection caused by microorganisms that
are commonly found in the host’s
environment. This term is often used to
refer to infections caused by organisms in
the normal flora

39. Nosocomial Infection –
Hospital Acquired Infections
• Infection which was neither present
nor incubating at the time of
admission
• Includes infection which only becomes
apparent after discharge from hospital
but which was acquired during
hospitalisation
• Also called nosocomial infection

40. • Portal of Entry
• Susceptible Host
• Causative Agent
• Reservoir
• Portal of Exit
• Mode of Transmission
6 Links - Chain of Infection

41. Links in the Chain
Transmitted through a chain (six links)
1. Pathogen - disease causing microorganism
2. Reservoir - natural environment of the pathogen:
Person, animal or environmental component
3. Portal of Exit
4. Means of transmission
• Direct transmission
• Indirect transmission
5. Portal of entry
• Penetration of the skin
• Inhalation
• Ingestion
6. New host
Breaking the Chain
6 Links - Chain of Infection

42. 6 Links - Chain of Infection

44. Definitions
• Reservoir of Infection
The source of an infectious agent
• Carrier
An individual who carries an infectious agent without
manifesting symptoms, yet who can transmit the agent to
another individual
• Fomites
Any inanimate object capable of being an intermediate in the
indirect transmission of an infectious agent

45. Vector & Sources Of Infection
Human Beings • Animals
• Patients
• Carriers
Healthy
Convalescent
Temporary
Chronic
Contact
Paradoxical
• Zoonosis
• Reservoir
Insects
• Mechanical
• Biological
Soil & Water
Food, Formites

46. Carriers
Carrier/Human cases
An individual who carries an infectious agent without
manifesting symptoms, yet who can transmit the agent
to another individual-
Healthy carrier
Convalescent carrier-Individual who recovered from
infectious disease but continuous to harbour the
pathogen

47. Methods Of Transmission
1. Contact-Direct/ Indirect-5Fs
2. Congenital
3. Inhalation
4. Ingestion
5. Inoculation
6. Insects
7. Iatrogenic
8. Lab Acquired

48. Methods Of Transmission

49. Methods Of Transmission

51. Virulence & Pathogenicity

52. Virulence
Virulence: Degree Of Pathogenicity
of the individual organism

53. Endotoxin vs Exotoxin

54. Endotoxin vs Exotoxin

55. 1. Protein
2. Heat Labile
3. Secreted by cells. Diffuse out
4. Separable by filtration
5. Enzymatic action
6. Specific effect
7. Specific tissue affinity
8. Active in small qty
9. Highly antigenic
10. Action neutralized by Ab
11. Both G + &G –
12. Eg:Botulinum,Tetanus,Diphtheria
1. LipoPolysaccharide
2. Heat Stable
3. Part of cell wall. No diffusion
4. Obtained only by cell lysis
5. No Enzymatic action
6. Effect nonspecific
7. Not specific
8. Active in large doses
9. Weakly antigenic
10. Antibody does not
11. Gram negative
Endotoxin vs Exotoxin

56. Mechanism of Endotoxin
Activity

57. Steps to Minimize Risk of
Infection
1. Locate, remove reservoir host
2. Block portal exit of microbes from reservoir
3. Know mode(s) of transmission of specific infections
4. Block portals of entry
5. Cleaning
6. Sterilization
7. Disinfectants
8. Antiseptics

58. 1st Principle Of Infection
Prevention
1st principle of infection prévention at least 35-50%
of all nosocomial infections are associated with
patient care practices:
1. Use and care of urinary catheters
2. Use and care of vascular access lines
3. Therapy and support of pulmonary functions
4. Experience with surgical procedures
5. Hand hygiene and standard precautions

59. Basic Steps In Prevention of
Infection
• There are possible
treatment and prevention to
stop the infection cycle. This
is through adequate
hygiene, sanitary
environment maintenance
and health education.
Dr.T.V.Rao MD 59

60. Infection Control And Quality
Healthcare In The New Millenium
Multidisciplinary Team Approach