The document discusses concepts related to infection including definitions of infection, classifications of infection such as primary, secondary and nosocomial infections, and factors that increase the risk of infection such as neutropenia, immunosuppression, and invasive devices. It also covers the chain of infection including the infectious agent, reservoir, modes of transmission through contact, droplets, and common vehicles or fomites, the portal of entry and susceptible host. The role of healthcare workers in infection control is discussed including handwashing, cleaning, disinfecting, sterilizing, and vaccinating.

2. Prepared by:
Munaza Rizwan
Nursing Instructor
SACON & IHS

3. Microbiology
Unit no:05
Concept of asepsis:
Medical & Surgical Asepsis

4. WHAT IS INFECTION:
Definitions :
“Infection may be defined as the lodgment and
multiplication of an infectious agent in the body.”
Or
“Infection is the invasion of body tissues by disease causing agents ,their
multiplications ,and the reaction of the host tissue to the infectious agents and the
toxins they produce.”
Or
“An infection is the colonization of the host by microbial species “
Or
“The invasion and multiplication of microorganisms such as bacteria ,viruses,and
parasites that are not normally present within the body.”

5. CLASSIFICATION OF INFECTION
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.Secondry infection:
When in a host whose resistance is lowered by
preexisting infectious disease ,a new organism may set up in infection.

6. 5.Focal infection:
It is a condition where due to infection at localized sites
like appendix and tonsils, 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 occuring in hospital.
8.subclinical infection:
It is one when clinical affects are not apparent.

7. Endogenous infection:
Sometimes,microorganisms are part of
patients own body flora and can cause infection in the
immunocompromised host.These infections are called endogenous
infection.
Exogenous infection:
Infections which are acquired from external source
are called exogenous infection.

8. Infectious disease:
A clinically manifest disease of man or animal resulting from an
infection.
E.g.Flu,measles,HIV,Strep throat,covid-19, salmonellosis(common
bacterial disease that affects the intestinal tract)
Contagious disease:
A disease that is transmitted through contact.
E.g:Hepatitis A,B,C,influenza,Meningococcal disease
Communicable disease:
An illness due to specific infectious agent or its toxic products
capable of being directly or indirectly transmitted from man to
man,animal to animal,or environment(through air ,dust, soil, water
,food etc) to man or animal.
E.g:Measles,Food borne illnesses

10.  Modes of Transmission:
Breaking the chain at the ‘mode of transmission’ is one
of the most important ways to interrupt the spread of
infection. This is where infection prevention and control
strategies can be most successful.
Microorganisms are transmitted in health care settings
by four main routes:
• Contact
• Droplet
• Airborne
• Common vehicle
 Survival Times of Microorganisms on Hard
Inanimate Surfaces:
Organisms & their Survival Time
Adenovirus Up to 3 months
Clostridium difficile Up to 5 months
Coronovirus 3 hours
E. coli Up to 16 months
Influenza 1-2 days MRSA Up to 7 months
M. tuberculosis Up to 4 months
Norovirus Up to 7 days

11. 1.Contact:
Contact is the most frequent mode of transmission of health care
associated infections and can be divided into: direct and indirect. An
example of contact transmitted microorganisms is Noroviruses which are
responsible for many gastrointestinal infections.
• Direct:
Involves direct body surface to body surface contact and physical
transfer of microorganism between an infected or colonized person to
another person by touch.
• Indirect:
Involves contact between a person and a contaminated object. This is
often a result of unclean hands contaminating an object or environment.
The microorganism remains on this surface to be picked up by the next
person who touches it.

12. 2.Droplet:
Transmission occurs when droplets containing
microorganisms generated during coughing, sneezing and
talking are propelled through the air.
 These microorganisms land on another person, entering
that new person’s system through contact with his/her
conjunctivae, nasal mucosa or mouth.
 These microorganisms are relatively large and travel only
short distances (up to 6 feet/2 metres). However these
infected droplets may linger on surfaces for long periods of
time, so these surfaces (within the range of the
coughing/sneezing person) will need additional cleaning.
For this reason there may be both Droplet and Contact
Precautions required at the same time.
Examples of microorganisms that are spread by droplet
transmission are: influenza, colds, respiratory syncytial virus
(RSV) and some organisms causing pneumonia.

13. 3.Airborne:
Airbone transmission of infectious agents occurs either by:
• Airborne droplet nuclei (small particles of 5 mm or smaller in size)
• Dust particles containing infectious agents.
Microoganisms carried in this manner remain suspended in the air
for long periods of time and can be dispersed widely by air currents.
Because of this, there is risk that all the air in a room may be
contaminated.
Some examples of microorganisms that are transmitted by the
airborne route are: M. tuberculosis, rubeola, varicella and
hantaviruses.
4.Vector borne diseases:
These are the infections transmitted by the bite of infected
arthropods species,such as mosquitos,ticks
,bugs,sandflies,backflies.

14. 5.Common Vehicle:
Applies to microorganisms that are transmitted by contaminated items
such as food, water, medications, medical devices and equipment.
To inhibit the transmission of microorganisms by this mode:
• Clean patient equipment between uses with different patients
• Handle, store and prepare food properly
• Careful store and draw up doses of medication from multidose
medication vials.

15. CHAIN OF INFECTION
1.INFECTIOUS DISEASE:
Any microorganism that can cause a disease such as a bacterium,
virus, parasite, or fungus. Reasons that the organism will cause an
infection are virulence (ability to multiply and grow), invasiveness (ability
to enter tissue), and pathogenicity (ability to cause disease).
2.RESERVOIR:
The place where the microorganism resides, thrives, and reproduces,
i.e., food, water, toilet seat, elevator buttons, human feces, respiratory
secretions.
3.PORTAL OF EXIT :
The place where the organism leaves the
reservoir, such as the respiratory tract
(nose, mouth), intestinal tract (rectum),
urinary tract, or blood and other body
fluids.

16. MODE OF TRANSMISSION:
The means by which an organism transfers from one
carrier to another by either direct transmission (direct
contact between infectious host and susceptible host)
or indirect transmission (which involves an
intermediate carrier like an environmental surface or
piece of medical equipment).
PORTAL OF ENTRY:
The opening where an infectious disease enters the host’s body such
as mucus membranes, open wounds, or tubes inserted in body cavities
like urinary catheters or feeding tubes.
SUSCEPTIBLE HOST:
The person who is at risk for developing an infection from the disease.
Several factors make a person more susceptible to disease including
age (young people and elderly people generally are more at risk),
underlying chronic diseases such as diabetes or asthma, conditions
that weaken the immune system like HIV, certain types of medications,
invasive devices like feeding tubes, and malnutrition.

18. FACTORS THAT INCREASES THE RISK
FOR INFECTION:
1.Neutropenia
2.Cellular & Humoral immune dysfuctioning
3.Bone marrow Transplantation
4.Intravascular devices
5.Splenectomy
6.Chemoterapeutic agents
7.Touching contaminated objects
8.Eating contaminated food
9.Large number of people are in small space for a long time
10.Sharing of glassess
11.Poor nutrition
12.Stress
13.Lack of sleep
14.Age
15.Pre existing chronic disease

19. ROLE OF HEALTH CARE
PERSONNEL & HEALTH IN
INFECTION CONTROL

20. ROLE OF A NURSE IN INFECTION
CONTROL:

25. 1.Hand
washing
3.Disinfecti
ng
2.Cleanin
g
5.Vaccinatin
g
4.Sterilizin
g