医学微生物学概论Understanding the medical

microbiology

Dr. Jing QianZhejiang University School of Medicine

April 09, 2014

现代医学导论 2012 级食品安全与营养专业求是科学

班

Definitions

– Microorganisms(Microbes) 微生物

– Microbiology 微生物学

– Medical Microbiology 医学微生物学

• The word “microbe” comes from the Greek words mikros, meaning small, and bios, meaning life. So microorganisms/microbes are small living things that are too small to be seen with the unaided eye.

• Microorganisms were probably the first organisms to appear on the earth.

• However, these organisms were not seen until about 3 centuries ago when lenses powerful enough to make them visible were made.

• Viruses, bacteria, fungi, protozoa and some algae are all in this category.

Microorganisms/Microbes

• The distribution of microorganisms is universal in nature including air, soil, water, animals, human body.

Distribution

• There is a close relationship between microorganisms and human beings.

• Beneficial activities: Most microbes are of benefit to human beings, some are necessary. eg. nitrogen, carbon cycles, etc.

• Harmful activities: Only a small portion of microbes cause diseases and are poisonous to human, and these pathogenic microbes are really that concern us in the study of medicine.

Relationship with human beings

Microbes in nitrogen cycle

Microbes in carbon cycle

Background knowledge:

• Cell is the fundamental unit of all living things to carry out metabolic processes that transform energy and materials for growth and propagation (multiplication).

Organizational structure

• There are two fundamental types of cells: Prokaryotes and Eukaryotes with the major difference in whether or not the cell have membrane bound organelles and nucleus.

•  The prokaryotic cell, in contrast to the eukaryotic cell, has no nuclear membranes, mitochondria, endoplasmic reticulum, Golgi body, phagosomes and lysosomes.

Differences between prokaryotes/eukaryotes

•  Prokaryotes generally possess only a single circular chromosome. Since there is no nuclear membrane, the chromosome is bound to a specific site on the cell membrane - the mesosome.  •  Prokaryotic ribosomes are 70S (S means Svedberg unit, a measure of size for centrifugation), whereas eukaryotic ribosomes are larger (80S).

• Prokaryotic ribosomal subunits are 30S and 50S (eukaryotic are larger). The 30S ribosome has 16S RNA, while the 50S ribosome contains 23S and 5S RNA.

• According to organizational structure,

microbes can be divided into three types:

Prokaryotes (Eubacteria and

Archaebacteria)

Eukaryotes (fungi, Protozoa, algae)

Acellular entities (viruses)

Classification of microbes

• Eubacteria are "True" bacteria which include Bacteria, Chlamydiae, Mycoplasmas, Richettiae, Spirochetes, and Actinomycetes. Some of them cause human diseases.

• Members of the Archaebacteria are often found in extreme environments (methane-containing, high salt or hot temperature) environments. They are not human pathogens and will not be discussed further. 

Eubacteria and Archaebacteria

• Eubacteria and Archaebacteria are the two major types of prokaryotes. They appear similar morphologically but have major biochemical differences.

Viruses• Viruses are not living organisms because they do not

contain all the enzymes required for their replication and possess the biologic equipment necessary for the production of metabolic energy.

• Viruses are non-cellular microbes. They are obligate parasites totally dependent on their host for replication.

• Morphologically, viruses are very small particles and have no basic cell structure. A simplest virus

consists of one core and one protein coat (capsid). The core composed with a nucleic acid molecule, either DNA or RNA.

• Fungi is a kind of eukaryotic cells. So they have various organelles, for examples, nuclear membranes, mitochondria, endoplasmic reticulum, Golgi body, phagosomes and lysosomes.

Fungi

• There are more than 100, 000 species of fungi, but most of them are beneficial to humankind. They reside in nature and are essential in breaking down and recycling organic matters.

• Only a few of fungi can cause human diseases.

•Microbiology is the biology of microorganisms.

Microbiology

• It has an impact on medicine, agriculture, food science, ecology, genetics, biochemistry, and other fields.

• It is a bioscience for the study of various characteristics or activities of microorganisms including microbial morphology, cytology, physiology, ecology, genetics, molecular biology and taxonomy.

• Branches of Microbiology are Medical Microbiology, Food Microbiology, Public health Microbiology, Industrial Microbiology and Agricultural Microbiology

Medical Microbiology

• The medical microbiology is the study of pathogenic microbes.

• It concerns the biological characteristics of microorganisms and their relationships with human hosts including:

　 Pathogenicity and immunity　　 Laboratory diagnosis　　 Prevention and treatment

etc.

Medical Microbiology

• Branches of medical microbiology include Medical Bacteriology (Six eubacterial categories: Bacteria, Chlamydiae, Mycoplasmas, Richettiae, Spirochetes and Actinomycetes), Medical virology, Medical Mycology.

• Medical Microbiology contains anti-infectious immunity in Immunology.

• In some countries, Parasitology is enclosed Microbiology

• Understanding and employing the principles of microbiology and the molecular mechanisms of pathogenesis enable the physicians and medical scientists to control an increasing number of infectious diseases.

history and current situation

Medical Microbiology

Infectious Diseases in History

• Tuberculosis• Plague• Smallpox• Syphilis• Influenza

3700 BC

Smallpox• Numerous epidemics in Europe, Asia

– Plague of Athens 430 BC– Antonia Plague of Rome 165-180– India c. 400

• Introduced to the Americas in 1520 by Cortés, killing 25% of Aztec population

• Spread to Incan population via roads• North America in 1633, Plymouth, MA

Influenza• Symptoms described by

Hippocrates 412 BCE• Ascribed to unfavorable

astrological influences in Italy in the 15th Century

• First pandemic recorded in 1580

• Term “influenza” used in English in 1743

• Virus discovered by Medical Research Council in England in 1933

Influenza Pandemics

• 1918 Spanish flu• 1957 Asian flu (H2N2)• 1968 Hong Kong flu

(H3N2)• 1976 swine flu non-

pandemic• ? Avian flu (H5N1)

• The numerous emerging and re-emerging infectious diseases such as AIDS, SARS, avian influenza, tuberculosis, viral hepatitis and so on.

New challenge in medical microbiology

30 years of emerging viral diseases

1986Bovine spongiform encephalopathy

1980 Hepatitis D

1980 Human T-cell- Leukemia-Virus

1977 Hantaan-Virus

1976 Ebola fever

1985 HIV/AIDS

1981 HIV/AIDS

1989 Hepatitis C

1999 West Nile fever

1994 New Variant of Creutzfeldt-Jakob-Syndroms

2003 SARS

2005 HPAI H5N1

2013 H7N9??

Emerging viral diseases: monkey pox virus

A 7 year old girl from Zaire

Monkeypox

A member of the orthopox virus (next to: Variola)

local outbreaks since 1990

It is a zoonosis in the Americas: prairie dogs

Kaposi-sarcoma

origin:Human Herpesvirus type 8, HHV-8= Kaposi-sarcoma-associated Herpesvirus, KSHV

One of the leading diseases in (untreated) AIDS-patients

Emerging viral diseases: Kaposi sarcoma

Influenza Hong Kong, 1997: death of 7.000 chicken

in 3 farms

Crossing of species barrier of a new influenza strain (H5N1) from poultry to man

20 humans became infected.

One third die. No human to human transmission.

Killing of 1,6 millions poultry to prevent spreading among poultry

Vietnam, Thailand, China, Laos, Korea, Japan, Kambodscha, Indonesien, 2004: reemergence of H5N1

Suspected human to human transmission

Emerging viral diseases: Avian influenza virus

Development of Medical Microbiology

• Medical microbiology has developed from

Experience phase, Experimental phase to

Modern phase and is still keep developing.

• Some landmarks in each phase are:

Time line of Microbiology

Time line of Microbiology

Robert Koch :Based on his experimental results, he raised a criteria, called as Koch’s Postulate, to establish the link between a particular microorganism and a particular disease:

1. The microorganisms must be present in every case of the disease but

absent from healthy individuals.

2. The suspected microorganisms must be isolated and grown in pure

culture.

3. The same disease must result when the isolated microorganism is

inoculated into a healthy host.

4. The same microorganism must be isolated again from the diseased

host.

Time line of Microbiology

Time line of Microbiology

Fleming and Florey(1945 nobel price)

Fei-Fan Tang 汤飞凡

（ 1897-1958 ）The first generation of virologist

in China.

He is the first scientist who was successful in isolating and

cultivating chlamydia trachomatis in 1955.

So far he is the only Chinese microbiologist who created a

research field in microbiology.

• Microbiology established a closer relationship with other disciplines during the 1940s because of its association with genetics and biochemistry.

• More recently, microbiology has been a major contributor to molecular biology and has been deeply involved in the elucidation of the genetic code; in studies on the mechanisms of DNA, ribonucleic acid (RNA), and protein synthesis; and in studies on the regulation of gene expression and the control of enzyme activity.

• In the 1970s new discoveries in microbiology led to the development of recombinant DNA technology and genetic engineering.

Microbiology in nature science

The Nobel Prize in Physiology or

Medicine 2008 was divided, one half

awarded to Harald zur Hausen "for his

discovery of human papilloma viruses causing cervical cancer",

the other half jointly to Françoise Barré-Sinoussi and

Luc Montagnier "for their discovery

of human immunodeficiency

virus".