MICROBIOLOGY AS A SCIENCE

2. MICROBIOLOGY -
The Science
Prepared by:
Sherleen Jane D. Fernandez, LPT

3. LEARNING OBJECTIVES:
 Define microbiology,
pathogen, nonpathogen, and
opportunistic pathogen.
 Differentiate between
acellular microbes and
microorganisms and list
several examples of each.
 List several reasons why
microbes are important (e.g.,
as a source of antibiotics).
 Explain the relationship
between microbes and
infectious diseases.
 List some of the contributions of
Leuwenhoek, Pasteur, and Koch to
microbiology.
 Differentiate between biogenesis
and abiogenesis.
 Explain the germ theory of disease.
 Outline Koch’s Postulates and cite
some circumstances in which they
may apply.
 Discuss two medically related fields
of microbiology.
 Differentiate between infectious
diseases and microbial
intoxications.

4. What is
Microbiology?
Microbiology -
is the study of
microscopic
organisms, such as
bacteria, viruses,
archaea, fungi
and protozoa.

5. TYPES OF BACTERIA
PATHOGENS
 Disease causing
microorganisms also
known as infectious
agents.
 3% of known
microbes
 “Microbial enemies”
NON-PATHOGENS
 Microbes that do
not cause disease
 Some are beneficial
to us whereas
others have no
effect on us at all
 “Microbial allies”

6. CATEGORIES OF MICROBES

8. Why study Microbiology?

9. • We have, living on and in our
bodies (skin and in our mouth and
gastrointestinal tract),
approximately 10 times as many
microbes as the total number of
cells that make up our bodies.
 Indigenous Microbiota

10. • Some of the microbes that colonize (inhabit)
our bodies are known as opportunistic
pathogens (or opportunists). Although these
microbes usually do not cause us any
problems, they have the potential to cause
infections if they gain access to the part of
our anatomy where they do not belong.

11. • Microbes are essential for life on
this planet as we know it. For
example, some microbes produce
oxygen by the process known as
photosynthesis.

12. • Many microbes are involved in the
decomposition of dead organisms and
the waste products of living
organisms.
 Decomposition
 Decomposers or Saprophytes

13. • Some microbes
are capable of
decomposing
industrial
wastes
(oil spills, for
example).

14. • Many microbes
are involved in
elemental cycles,
such as the
carbon, nitrogen,
oxygen, sulphur,
and phosphorous
cycles.

15. • Algae and bacteria serve
as food for tiny animals.
Then, larger animals eat
the smaller creatures,
and so on.

16. • Some microbes live in the
intestinal tracts of animals,
where they aid in the digestion
of food and, in some cases,
produce substances that are of
value to the host animal.

17. • Many microbes are
essential in various
food and beverage
industries, whereas
others are used to
produce certain
enzymes and
chemicals.

18. • Some bacteria and
fungi produce
antibiotics that are
used to treat
patients with
infectious diseases

19. Antibiotic era
 We have all heard of the Pre-Antibiotic Era,
prior to the 1940’s when millions of people died
from common bacterial infections because
antibiotics were not used to treat them.
 In the last 50 years we have enjoyed the luxury
of knowing that bacterial infections can almost
always be cured by using antibiotics. We are now
in the Antibiotic Era.

20. Post-Antibiotic Era
 As we enter the 21st Century, we are gradually
slipping into the Post-Antibiotic Era, a time when
antibiotics no longer work because bacteria have
become resistant to all the antibiotics.
 The change will not come as suddenly as the start of
the Antibiotic Era, because the change to antibiotic
resistant germs has been slow, up until now.
 New strains are rapidly developing

21. • Microbes are essential in the
field of genetic engineering.
• For many years, microbes have
been used as “cell odels”.

22. • Finally, we come to diseases.
Microbes cause two
categories of diseases:
infectious diseases and
microbial intoxications.

24. MICROBIOLOGY & INFECTIOUS DISEASE
 Today microbiology is mentioned frequently in the
news.
 It affects many facets of our daily lives, including:
The air we breathe
The food we eat
The hospitals where we go for treatment of illness and
injury
The natural disasters which sometimes occur without
warning

25. THE RELEVANCE OF
MICROBIOLOGY TO HEALTH CARE
• There has always been disease.
• For generations, little could be done to treat or
prevent disease.
• Advances in public health awareness lessened the
effects of infection.
• Infectious disease utilizes a large percentage of
health care.
• Health care professionals need to understand how
pathogens cause disease.

26. …THE RELEVANCE OF
MICROBIOLOGY TO HEALTH CARE
• The discovery of antibiotics began to prevent
serious infection.
• Vaccination and better sanitation practices reduced
the incidence of infectious diseases.
• For a time, most infectious diseases were thought to
be under control.

27. …THE RELEVANCE OF
MICROBIOLOGY TO HEALTH CARE
• Diseases once thought to be under control are
reappearing
• Pathogens are showing increasing resistance to
antibiotics.
• New diseases are emerging and organisms that were
thought to be harmless have been discovered to
cause disease in certain circumstances.
• A fundamental understanding of microbiology has
never been more relevant.

28. INFECTIOUS DISEASE
• Only a tiny fraction of
microorganisms cause infections.
• A microorganism that causes an
infection is called a pathogen.
• Only a fraction of pathogens affect
humans.

29. …INFECTIOUS DISEASE
• The potential of a pathogen to cause disease is
referred to as its degree of virulence.
• Many bacteria and some fungi are part of the normal
microbial flora of the body.
• They naturally colonize the skin and mucosal
surfaces.
• Most of the time, these organisms are completely
harmless.

30. ...INFECTIOUS DISEASE
• Some pathogens are always highly virulent.
• Highly virulent pathogens are always
associated with disease.
Most pathogens can be looked at from the
following 3 perspectives:
1. Epidemiology
2. Pathogenesis
3. Host defense

31. EPIDEMIOLOGY
In epidemiology, pathogens are studied by how
well they meet the five requirements of
infection:
• Entry (Get in)
• Establishment (Stay in)
• Defeat the host defense
• Damage the host
• Be transmissible

32. EPIDEMIOLOGY
 In epidemiology, pathogens are classified by the
transmission mechanisms they use. Such as:
• Air
• Food or water
• Insect vectors
• Person-to-person contact
 Pathogens can also be classified according to their
geographic distribution

33. EPIDEMIOLOGY
• Providing the best care for infected individuals and
protection of others involves a clear understanding of
the 5 requirements for infection.
• Knowing how an organism gains entry and how it
spreads are vital to care for infected individuals
 It allows for the implementation of strategies to
limit spread.
 It also helps in understanding of the spread of
disease.

34. EPIDEMIOLOGY
Epidemics are caused by a variety of factors,
including the following:
• Poor socioeconomic conditions
• Ignorance of how infections occur
• Poor hygiene
• Natural disasters

35. PATHOGENESIS
Virulence factors are required for a pathogen to
do the following:
Persist in the patient
Cause disease
Escape or defeat host defenses

36. PATHOGENESIS
Pathogens employ a variety of methods
to accomplish infection.
Bacterial pathogens can:
• Produce digestive enzymes
• Produce toxins

37. PATHOGENESIS
Symptoms can be associated with
particular types of infection:
 Coughing – respiratory infection
 Diarrhea – digestive infection
 Nervous system dysfunction –
central nervous system

38. HOST DEFENSE
• Infection is a complex and competitive
struggle.
• It can be characterized as pathogens versus
host defense.
• The outcome of this struggle depends on the
success or failure of the host defense.
Failure of the host defense = infection

39. HOST DEFENSE
Many pathogens have developed methods to
defeat host defenses.
Some directly attack host defenses
Some change their looks (a form of
camouflage)
Some hide

40. TREATMENT OF INFECTIOUS DISEASES
Many potent and successful tools are
available to defeat infection. These include:
1. Antibiotics
2. Disinfectants and antiseptics
Antibiotics are toxic chemicals and
therefore must act selectively.
They must kill the disease-causing
microorganisms but not harm the patient.

41. TREATMENT OF INFECTIOUS DISEASES
• Treatments are easier for bacterial infections than for
fungal and viral diseases.
• Viruses are intracellular parasites so either:
1. They must be attacked before entry into a host
cell.
or
2. The infected host cells must be killed to kill the
virus.

42. TREATMENT OF INFECTIOUS DISEASES
The best treatment
of disease is
PREVENTION.

43. TREATMENT OF INFECTIOUS DISEASES
Public health measures include:
• Disinfection of water supplies
• Monitoring food supplies
• Proper hygiene and sanitation
• Proper waste removal and treatment
• Insect and pest control

44. TREATMENT OF INFECTIOUS DISEASES
• Immunization requires that we understand
immune mechanisms and that we design
vaccines that will successfully stimulate
protection.
Immunization also requires:
 Public health control of the immunization
of children
 Design and development of new vaccines
 An ability to ensure the safety of vaccines

45. FIRST MICROORGANISMS ON EARTH
 Fossils of primitive microorganisms
date back about 3.5 billion years ago.
 Candidates for the first
microorganisms on Earth are archaea
and cyanobacteria.

46. EARLIEST KNOWN INFECTIOUS DISEASES
 Infectious diseases of humans and
animals have existed for as long as
humans and animals have inhabited
the planet.
 Earliest known account of pestilence
occurred in Egypt in about 3180 BC.

47. PIONEERS IN THE SCIENCE
OF MICROBIOLOGY

48. ANTON VAN
LEEUWENHOEK
(1632-17230
• “Father of
Microbiology”
• Not a trained scientist!
• Made many simple
single-lens microscopes
• Observed
”animalcules”
(bacteria and
protozoa)

49. LOUIS PASTEUR
(1822-1895)
• French chemist who made
numerous contributions to
microbiology
• Investigated different
fermentation products
• Developed the pasteurization
process
• Discovered life forms that could
exist without oxygen (anaerobes)
• Developed several vaccines,
including rabies and anthrax
vaccines

50. LOUIS PASTEUR
• Pasteur laid the foundation of aseptic
techniques, techniques that prevent
contamination by unwanted microbes. These
techniques are based on Pasteur’s idea that
microbes can be killed by heat and that
procedures can be designed to inhibit the
access of airborne microbes to nutrient
environment.
• He disapprove the idea that microorganisms
spontaneously generated from non-living
matter.

51.  Pasteur discovered forms of
life that could exist in the
absence of oxygen.
 Pasteur discovered the
“Germ Theory of Disease”.

52. ROBERT KOCH
(1843-1910)
• German physician who made
numerous contributions to
microbiology
• Made significant
contributions to the germ
theory of disease
• Discovered that Bacillus
anthracis produced spores
• Developed methods of fixing
and staining bacteria
• Developed methods to
cultivate bacteria

53. Bacillus anthracis

54. Koch’s Postulates:
1. A particular microbe must be found in all cases of
the disease and must not be present in healthy
animals or humans.
2. The microbe must be isolated from the diseased
animal or human and grown in pure culture in the
laboratory.
3. The same disease must be produced when microbes
from the pure culture are inoculated into healthy
susceptible laboratory animals.
4. The same microbe must be recovered from the
experimentally infected animals and grown again in
pure culture.

56.  If an organism fulfill Koch’s postulates, it
has been proven to be the cause of that
particular infectious disease.
 Koch’s Postulates helped prove the germ
theory of disease.
 Koch gave a tremendous boost to the
development of microbiology by stressing
laboratory culture and identification of
microorganisms.
 Circumstances do exist in which Koch’s
Postulates cannot be fulfilled.

57. Exceptions to Koch’s Postulates:
 To fulfil Koch’s Postulates, it is
necessary to grow the pathogen in
the laboratory (in vitro) in or on
artificial culture media. However,
some pathogens will not grow on
artificial media.

58.  To fulfil Koch’s Postulates, it is
necessary to infect laboratory
animals with the pathogen being
studied. However, many pathogens
are species-specific, meaning that
they infect only one species of
animal.

59. Some diseases, called synergistic
infections or polymicrobial
infections, are caused not by one
particular microbe, but by the
combined effects of two or more
different microbes.

60.  Another difficulty that is
sometimes encountered while
attempting to fulfil Koch’s
Postulates is that certain pathogens
become altered when grown in
vitro.

61. The Golden Age of Microbiology
(1857-1914)
• Many disease producing organisms were
discovered.
• Microbial metabolism studies undertaken.
• Microbiological techniques refined.
• A better understanding of the role of
immunity and ways to control and prevent
infection by microbes.

62. CAREERS IN MICROBIOLOGY
• A microbiologist is a scientist who
studies microbes.
• There are many career fields within
the science of microbiology (e.g.,
bacteriology, phycology, protozoology,
mycology, parasitology, and virology).

63. Medical & Clinical Microbiology
 Involves the study of pathogens, the
disease they cause and the body’s defenses
against disease.
 Concerned with epidemiology, transmission
of pathogens, disease-prevention measures,
aseptic techniques, treatment of infectious
diseases, immunology, and production of
vaccines.

64. Your future career:
NURSE
Put your name here, RN