This document defines important terms related to the control and destruction of microbes. It discusses asepsis, antisepsis, disinfection, sterilization, and pasteurization. It describes different methods of controlling microbes, including heat treatments, chemicals, and antibiotics. Pasteurization uses lower temperatures than sterilization to kill some but not all microorganisms. Antibiotics are classified based on their target microbes, modes of action, chemical structures, and spectra. The document also distinguishes between medical and surgical asepsis, with surgical asepsis aiming for complete sterility.

1. UNIT- V
CONTROL & DESTRUCTION
OF MICROBES
IMPORTANT DEFINITIONS
1. Asepsis: A state of being free from
disease causing micro-organisms.
2. Aseptic technique: Aseptic techniques is
a general term involving practices that
minimize the infection.
3. Antisepsis: it is the destruction or
inhibition of micro-organisms in living
tissues thereby preventing the harmful
effects of infection caused by them.
4. Antiseptic: The disinfectant that s applied
to living tissue is referred to as an
antiseptic.
5. Biomedical Waste: Any solid and or
liquid waste which is generated during
the diagnosis, treatment or immunizations
of human beings or animals, in research
activities or in the production or testing of
biological products.
6. Bactericidal: agent that kills bacteria
7. cidal: having killing effect
8. Chemotherapy- Treatment of disease by
chemical compounds known as
chemotherapeutic agents.
9. Disinfection- It is a process of destruction
or removal of microorganisms capable of
producing an infection, spores are not
necessarily killed.
10. Disinfectant: Chemicals that kill
vegetative bacteria, fungi, viruses and
rarely bacterial spores.
11. Fungicidal- Agents that kill fungi
12. Fomites- Inanimate objects like
contaminated towels, utensils that may
transmit infection.
13. Incineration: Agents they kill Ashes
14. Inertization: The process involves mixing
waste with cement and other substances
before disposal.
15. Segregation: Separating waste in
different color coded containers/bags
16. Scrubbing: To clean and disinfect before
participating in surgery.
17. Septicemia: Presence of pathogenic
bacteria in the blood.
18. Sterilization: Process in which vegetative
cell as well as spores are killed.
19. Steriller: Material that has been heated in
such a way that is contains no living
organisms is said to be sterile.
20. Sanitization: Process of cleaning
pathogenic microorganisms from public
eating utensils and objects.
21. Static: Agents that inhibit growth.
22. Tyndallization: This is the process by
which the culture medium is steamed.(
Either in Koch or Arnold steamer) for 30
minutes each on three successive days.
PASTEURIZATION
 The techniques was introduced by Louis
Pasteur in 1897.
 It is a heat treatment that kills part but not
the entire microorganisms present and
usually involve the application of
temperature below 100 degree c.
 The heating may be means of strem, hot
water, dry heat or electric current and the
products are cooled promptly after the heat
treatment.
USES
1. When more rigorous heat treatment might
harm the quality of product as with market
milk.
2. When one aim is to kill pathogens as with
market milk.
3. When the main spoilage organism are not
very heat resistant such as yeasts in fruit
juices.
4. When any surviving spoilage organisms
will be taken care of by additional
preservative method.
Time and temperature used in the pasteurization
process depend upon the method employed and the
product heated.
THE VARIOUS METHODS OF
PASTEURIZATION ARE:
1. HIGH TEMPERATURE SHORT TIME
METHOD OR FLASH METHOD: high

2. temperature is used for short period of time.
The temperature used in this method is 71.7
degree c for 15 seconds.
2. LOW TEMPERATURE HOLDING
METHOD: low temperature is used for
long period of time. The temperature used
in this method is 62.8 degree c for 30
minute.
3. ULTRA PASTEURIZATION: high
temperature is used to relatively short
period of time example- 137.8 degree c for
2 seconds in market milk.
CHEMOTHERAPY & ANTIBIOTICS
 Chemotherapy is the treatment of disease
by chemical compounds known as
chemotherapeutic agents.
 Antibiotics are antimicrobial agents
produced by microorganisms that kill or
inhibit other micro-organisms.
 A more broadened definition of an
antibiotic includes any chemical of natural
origin which has the effect to kill or inhibit
the growth of other types of cells.
CLASSIFICATION OF
CHEMOTHERAPEUTIC AGENTS
1. Classification on the basis of micro-
organisms on which they act: they can be
classified according to micro-organis ms
on which they act as,
I. ANTIBACTERIAL: effective against
bacteria: example: penicillin,
cephalosporin, tetracycline,
chloramphenicol etc.
II. ANTIVIRAL- effective against viruses:
ex- acylovir, ganciclovir,
azidothymidine,ribavirin etc…
III. ANTI-FUNGAL: effective against
fungi: example: amphoterici b,
flucytosine, azoles etc.
IV. ANTI-PROTOZOAL: effective against
protozoa, example: imidazoles,
pyrimethamine, pentamidine etc...
2. CLASSIFICATION ON THE BASIS OF
THEIR MODE OF ACTION
I. BACTERICIDAL: drugs that kill
the bacteria, example-
cephalosporins, polymyxin,
streptomycin, erythromycin etc.
II. BACTERIOSTATIC: drugs that
inhibit growth of bacteria, ex-
sulfonamides, tetracycline, etc.
3. CLASSIFICATION ON THE BASIS OF
THEIR SITE OF ACTION
I. Drugs acting on cell wall: includes
penicillin, cephalosporins,
bacitracin, vancomycin etc.
II. Drugs acting on cell membrane-
includes polymyxin, amphotorcin
etc.
III. Drugs inhibiting proteins
synthesis: includes macrolides, etc.
IV. Drugs inhibiting the nucleic acid
(DNA) - nalidixic acid, tetracycline,
mitromycin etc.
V. Drugs acting as antimetabolites:
sulfonamides, sulfones, isoniazid.
4. CLASSIFICATION ON THE BASIS OF
THEIR CHEMICAL STRUCTURE
I. Lactum antibiotics: penicillins,
natural penicillin,
cephalosporins.monobactams.
II. Tetracyclin- oxy- tetracycline,
chloro tetracycline.microcycline.
5. CLASSIFICATION ON THE BASIS OF
THEIR SPECTRUM OF ACTION
I. Limited spectrum: drugs effective
against a single organisms or
disease
II. Narrow spectrum: drugs effective
against gram positive or gram
negative bacteria.
III. Broad spectrum: drugs effective
against a wide variety of species.
MECHANISMS OF ACTION OF ANTI-
MICROBIAL AGENTS
1. Inhibition of cell wall synthesis:drugs like
penicillins, cephalosporins, bactracin, and
vancomycin bind to the receptors on the
cell wall of bacteria and interfere with the
synthesis of peptidoglycan of cell wall.
2. Inhibition of cell membrane function:
drugs like polymyxin b, colistin bind
selectively with cell membrane and inhibits
its function, and as a result property of semi
permiability is lost and essential

3. macromolecules and ions escape out in to
environment resulting in damage or death
of a cell.
3. Inhibition of protein synthesis: drugs like
tetracycline,chloramphenicol and
macrolides interfere with different stages of
process of protein synthesis and thus inhibit
protein synthesis in bacterial
ribosomes.(70S)
4. Inhibition of nucleic acid synthesis: drugs
like rifampicin binds with DNA dependent
RNA polymerase, quinolones block DNA
gyrase and thus interfere with transcription
of genetic information on ribosomes
leading to inhibition of DNA synthesis.
5. Inhibition of metabolism: drugs like
sulphonamides, sulfones, trimethrprim act
as antimetabolities as they interfere with
normal metabolism of bacteria by
inhibiting the biosynthesis of various
essential metabolites in the cell.
USES OF ANTIBIOTICS
1. Medically they are used for treatment of
disease.
2. They are used for chemoprophylaxis in
surgery and other diseases.
3. They are incorporated in culture media to
make them selective.
4. They are used to control contamination in
tissue culture used for virus isolation.
5. They are used in animal feeds as
supplements.
6. They are used against some plant
pathogens.
7. They are used for epidemiological typing of
bacteria.
MEDICAL AND SURGICAL ASEPSIS
Asepsis is the condition of being free from disease
producing micro-organisms. Asepsis is divided in
to the following two categories.
1. MEDICAL ASEPSIS
It includes all the procedures used to protect the
patient and his environment from the spread of
infectious organisms.
Medical asepsis consists of techniques that
inhibit the growth and spread of pathogenic
micro-organisms.
Medical asepsis is also known as clean
technique and in many daily activities such as
hand hygiene and changing patient’s bed linen.
2. SURGICAL ASEPSIS:
It includes all the procedures used to sterilize and
to keep sterile any objects or article that are to be
introduced in to a wound or body cavity or that is
to penetrate the skin.
Surgical asepsis destroys all micro-organisms and
their spores.
Surgical asepsis is known as sterile technique and
is used in specialized areas or skills such as care of
surgical wounds, urinary catheter insertion,
invasive procedures and surgery.
MEDICAL AND SURGICAL ASEPSIS
TECHNIQUES
A. EMPHASIS
Medical asepsis: cleanliness (freedom from
most pathogenic organisms)
Surgical asepsis: sterility (freedom for all
micro-organisms)
B. PURPOSES
Medical asepsis: to reduce the transmission
of pathogenic organisms from patient to
another person.

4. Surgical asepsis: to prevent introduction of
any organism in to an open wound on the
patients or in to a body cavity.
C. ISOLATION
Medical sepsis: patients with a communicable
disease are separated from the rest of the patients
by room, ward or unit.
Surgical asepsis: patients requiring surgery are
taken to the operating room of the hospital.
D. ZONE
Medical asepsis: a zone about the isolation unit is
established as contaminated. Everything within the
zone of isolation is contaminated.
Nothing goes out of the zone without being
disinfected or wrapped in a clean cover to permit
handling in a clean zone.
Surgical asepsis: a zone about the site of operation
or wound is established as a sterile field.
Once a sterile article touches an unsterile article, it
is contaminated.
Only sterile article are brought in to the sterile field.
E. HANDWASHING
Medical asepsis- hands and forearms are washed
for 1 to 2 minutes to remove surface contaminants
and soil. Hands and arms are dried with paper
towels.
Surgical asepsis: hands and forearms are scrubbed
for 10 minutes to reduce the bacterial count on the
skin surface. Hands and arms are dried with a
sterile towel.
F. GOWNS
Medical asepsis: clean gowns are worn to protect
the worker. Inside of gown is clean outside of gown
in contact with patient and his environment it
contaminated.
Surgical asepsis: sterile gown are worn to protect
the patient from the worker, outside of gown is in
contact with the sterile field must kept sterile.
G. STATUS OF PATIENT
Medical asepsis: reservoir of infection
Surgical asepsis: potential host (other people and
environment are reservoirs of infection.
H. GOALS
Medical asepsis: confine disease organisms and
prevent spread to others.
Surgical Asepsis: Reduce number of organisms and
prevent spread of infection to others.