This document discusses controlling microbial growth through various methods. It covers culturing bacteria and fungi in the laboratory, including using selective and enriched media. It also discusses factors that affect microbial growth, different types of microorganisms, and methods for inhibiting microbial growth such as sterilization techniques. The document notes controversies around using antimicrobial agents in animal feed and household products.

1. CONTROLLING MICROBIAL
GROWTH
INTRODUCTION TO MICROBIOLOGY
MUNIRA SHAHBUDDIN, PhD.
BTEN 2210

2. CHEMOTHERAPEUTICS
- Any drugs or agents used to
treat any disease
- The chemotherapeutic drugs
used to treat infectious
disease collectively referred
to as antimicrobial agents.
- An antibiotic is a substance
produced by a microorganism
that is effective in killing or
inhibiting the growth of other
microorganism

3. CONTROLLING MICROBIAL GROWTH IN
VITRO
Factors that affect microbial growth:
1. Availability of nutrient
2. Moisture
3. Temperature
4. pH
5. Light
6. Osmotic pressure and salinity
7. Barometric Pressure
8. Atmosphere

4. MICROORGANISMS
- CLASSIFICATION
Different type of microorganisms
Psychophilic
Mesophilic
Halophilic (prefer salty environment)
Haloduric
Alkaliphilic
Acidophilic
Piezophilic

5. CULTURING BACTERIA IN
LABORATORY
The earliest successful attempt to successfully
culture microorganisms in laboratory setting
were made by Ferdinand Cohn (1872), Joseph
Schoreter (1875) and Oscar Brefeld (1875).
Robert Koch describe his technique in 1881.
In 1878, Joseph Lister became the first person
to obtain the pure culture of bacterium
(Streptococcus lacti) in a liquid medium.
Koch, Pasteur and Lister made significant
contributions to the germ theory of disease.

6. CULTURING BACTERIA IN
LABORATORY
Bacterial growth – proliferation or
multiplication of bacteria.
Bacteria multiply by binary fission, which is
called organism’s generation time.
Microorganisms that are difficult to grow in
the laboratory are said to be fastidious.

7. CULTURING BACTERIA IN
LABORATORY
Selective medium: is used
to discourage the growth of
certain organisms without
inhibiting the growth of
organism being sought
Enriched medium: broth or solid
medium containing rich supply of
special nutrient that promotes the
growth of fastidious organisms.

9. INOCULATION OF CULTURE
MEDIA
In clinical microbiology laboratory, culture
media are routinely inoculated with clinical
specimens. Inoculation involves adding a
portion of the specimen to the medium using
sterile inoculating loop using a process
referred to as streaking.

10. ASEPTIC TECHNIQUE
It is practiced in microbiology laboratory to
prevent infection of individuals and
contamination of the work environment,
clinical specimen and cultures.
Unwanted organisms are referred to as
contamination

11. CONTAMINATION IN
CULTURE

12. INCUBATION: a chamber
containing appropriate
atmosphere and moisture
To culture human pathogen, the incubator is set at
35 – 37 oC.
There are three types of incubators in CML:
1. A CO2 incubator to maintain the concentration
of 5-10% CO2 – it contains O2 about 15-20%
2. A non CO2 incubator – only contain the room
air and O2 about 15-20%
3. An anaerobic incubator which is devoid of
oxygen.

13. BACTERIAL POPULATION
COUNT
Determination of total bacterial count
in the liquid
1. Spectrophotometer technique
2. Viable plate count
3. Haemacytometer

14. Coulter counter: Particle size analysisCell count using Haemacytometer

15. Cell count using Spectrophotometer

16. BACTERIA POPULATION
GROWTH CURVE
A bacterial growth curve consist of four phases
1. Lag (adaptation)
2. Log (exponential)
3. Stationary (Plateau)
4. Death

17. CULTURING INTRACELLULAR
PATHOGENS
Certain microbes can only
survive and multiply within
living cells.
- They can be propagated
in laboratory using
embryonated chicken
eggs, laboratory animals
or cell culture

18. CULTURING FUNGI IN
LABORATORY
Fungi including yeast, molds and
dimorphic fungi will grow on and in
various solid and liquid culture media.
There is no one medium that is best for
all medically important fungi.
Antibacterial agent often added to
inhibit/suppress the growth of
bacteria.
https://blog.mycology.cornell.edu/2008/01/10/a-simple-way-to-preserve-fungal-cultures/

19. CULTURING FUNGI IN
LABORATORY
Laboratory personnel must exercise
cautious when culturing fungi because
the spores of fungi are highly
infectious.

20. METHOD OF INHIBITING
GROWTH OF MICROBES IN
LABORATORY
METHODS OF
STERILIZATION:
1. Dry heat
2. Cold
3. Radiation
4. Filtration
5. Dessication
6. Autoclave (moist
heat)
Sterilization: Destruction of elimination
of all microbes
Disinfection: Elimination of most all
pathogens (except bacterial spores)

22. METHOD OF INHIBITING
GROWTH OF MICROBES IN
LABORATORY
Lyophilization: a process that combines
dehydration (drying) and freezing.
Disinfectant: the use of chemical
agents to inhibit the growth of
pathogen.

23. EFFECTIVENESS OF
ANTIMICROBIAL
PROCEDURES
Effectiveness
of
antimicrobial
procedures
Temperature
Concentration
Type of
microbes
Number of
microbes
Presence of
spores
Presence of
proteins in
feces, blood,
vomitus, pus
Time

24. CONTROVERSIES RELATING TO THE USE OF
ANTIMICROBIAL AGENTS IN ANIMAL FEED
AND HOUSEHOLD PRODUCTS
40% of the antibiotic manufactured in
the United States are used in animal
feed. The reason is obvious: to prevent
infections that could lead to economic
losses.

25. THE USE OF ANTIMICROBIAL
AGENTS IN EVERYTHING?

26. HYGENIC HYPOTHESIS?
Many scientists believe that children
must be exposed to all sorts of
microorganisms during their growth
and development so their immune
system will be developed correctly and
capable of properly responding to
pathogen in later years.