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Medical Microbiology
Xuan Xiaoyan
Dept. of medical Microbiology
and Immunology
Microbiology is the study of
living organisms that are so small
as to be visible only through
Medical Microbiology
What is Microorganisms
 Microorganisms are creatures that are not
directly visible to the unaided eye, with
dramatically biologic diversity.
 Viruses , bacteria, fungi, protozoa and some
algae are all in this category
 All with the exception of plants and animals
Major groups of microorganisms
1. Prokaryotes
2. Eukaryotes
3. Neither eukaryotic nor prokaryotic
 They are the cells of lower (primitive ) life forms. The
nuclear material (DNA) not enclosed within a membrane,
but rather is distributed in masses throughout the
cytoplasm; this primitive type of nucleus is called a
prokaryon, and the cell are said to be prokaryotic. In
addition to nuclear membrane, these simple unicellular
organisms also have not mitochondria, Golgi bodies, and
endoplasmic reticulum. They produce by asexual division.
This group of microorganisms contains bacteria,
actinomycetes, mycoplasmas, rickettsiae, Chlamydiae,and
 In this type of cells the nucleus is well defined,
being enclosed within a nuclear membrane. it is
called a true nucleus, or eukaryon and the cell is
said to be eukaryotic. All higher form of life,
including ourselves, consists of eukaryotic cells.
Fungi are eukaryotic organisms that contain a
well-defined nucleus, mitochondria, Golgi
bodies, and endoplasmic reticulum.
Neither eukaryotic nor prokaryotic
 Viruses are the smallest infectious particles. They are not
cells in the accepted sense and rely on the biochemical
processes of the host cell for their replication and
propagation. A viral particle consists of a nucleic acid
molecule, either DNA or RNA, enclosed in a protein coat
or capsid. A number of transmissible plant diseases are
caused by viroids---small single-strand RNA molecules.
They do not possess capsids. Prion , a new transmissible
agent causing a degenerative central nervous system
disease of human and animal, is a infectious protein
without nucleic acid.
Distribution of microorganisms
 Air
 Soil
 Water
 Animals
 Human body
Microorganisms and Human Beings
 Beneficial activities: Most microbes are of
benefit to human beings, some are
necessary( nitrogen, carbon cycles, etc)
 Harmful activities: A portion of microbes
cause diseases and are poisonous to human,
and these are really that concern us in the
study of medical microbiology, etc.
 Microbiology is the biology of
microorganisms. It is a bioscience for the
study of the evolution, Classification ,
morphology, physiology, genetics, ecology
of microbes under certain definite
conditions, The law of their life activities,
and their interaction with human being,
animals or plants as well as with natural
The Importance of Microbiology
 Environment
 Medicine
 Food
 Industry
 Biotechnology
 Research
History of Microbiology
 Experience phase经验时期
 Experimental phase实验时期
 Modern phase现代微生物学时期
Experience phase
Experimental phase
 Leeuwenhoek
 Pastur
 Koch
 lister
Koch’s postulates
 the microbe must be found in the body in all cases
of the disease
 it must be isolated from a case and grown in a
series of pure culture in vitro
 it reproduce the disease on the inoculation of a late
pure culture into a susceptible animal
 the microbe must be isolated again into pure
culture from such experimentally caused infection.
Fei-Fan Tang
Modern phase
Emerging and Reemerging
Infectious Disease
 Tuberculosis
 Hepatitis
 Gastric ulcer
Medical Microbiology
 The medical microbiology is one of the
essential basic sciences for medcine. It
is the study of Biological
characteristics of microorganisms and
their relationships with human hosts
Medical Microbiology
Medical Bacteriology
Medical Virology
Medical Mycology
 Parasitology
 Immunology
Purpose for learning of Medical
 Medical Microbiology
 Note of Medical Microbiology
One of the most important reasons for studying
microbes is to understand the diseases they cause and the
ways to control them. The relationship between many
organisms and their disease is not simple. Organisms
rarely cause a single well-defined disease. Instead, it is
more commonly for a particular organism to produce
many manifestations of disease or for many organisms to
produce the same disease. In addition relatively few
organisms can be classified as always pathogenic Instead,
most are able to establish disease only under welldefined circumstances. Some diseases arise by
exogenous infections, and most human diseases,
however, are produced by endogenous infections.
The interaction between an organism and the
human host is complex. The outcome of this
interaction is determined by the virulence of the
organism, the site of exposure, and the host's ability
to respond to the organism. To improve the human
body's ability to prevent infection the immune
system can be augmented either through the passive
or through active immunization. Infection can also
be controlled with a variety of chemotherapeutic
Unfortunately, microbes can alter their
antigenic complexion (antigenic variation) or
develop resistance to even the most potent
antibiotics. Thus, the battle for control between
microbe and host continues, with neither side yet to
claim victory.
It is important to realize that our knowledge of
the microbial world is evolving continually. Just as
the early microbiologist built their discoveries on
the foundations established by their predecessors,
so, too, will we and future generations continue to
discover new microbe ,a new diseases, and new