Lecture 1 - Introduction To Microbiology
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Introduction to Microbiology Dr. Eiman Mokaddas MD, FRCPath Associate Professor Microbiology Department Faculty of Medicine
10/14/08
E.Mokaddas
1
History Contagion: Spread of disease
10/14/08
Pioneers responsible for the science of bacteriology: Antony van Leeuwenhoek: discovered the microscope in 1675 Louis Psteur: The founder of modern Microbiology( 1860-1890): culture methods, principles of immunization Joseph Lister: professor of surgery in Glascow. Applied Pasteur’s observations to prevention of wound sepsis. In 1867 invented antiseptic technique to kill bacteria in wounds Robert Koch: German GP who discovered the bacterial causes of many diseases including tuberculosis in 1882 ( Koch’s postulates) E.Mokaddas
2
Definitions
10/14/08
Microorganisms are minute living things that cannot be seen with the naked eye. Microbial pathogens are microorganisms that have structures or products that allow them to cause disease. Microbiology is the study of all organisms in the microscopic range. This include bacteria, fungi, algae, viruses and protozoa.
E.Mokaddas
3
Classification of Microorganisms
10/14/08
E.Mokaddas
4
Classification of Microorganisms Prokaryotes Eukaryotes Viruses Bacteria Cyanobacteria
10/14/08
Fungi Protozoa
E.Mokaddas
5
Property
10/14/08
Prokaryotic cells
Eukaryotic cells
Chromosome one number Size 1-10um
Multiple
Nuclear membrane Mitochodria
Absent
Present
Absent
Present
Ribopsomes
70s
80s
sterols
Absent
Present
E.Mokaddas
10-100 um
6
Classification of Microorganisms Nomanclature (Naming) Genus e.g. Staphylococcus Species e.g Staphylococcus aureus
10/14/08
E.Mokaddas
7
Bacteria
10/14/08
Are unicellular organisms without a defined nucleus They vary in shape, size, metabolic activity, motility, and requirement for physical and chemical agents They reproduce by asexually by binary fission They occur as cocci (spherical), bacilli ( rods) spirilli (spirals), vibros (coma shaped) , wavy (spirochetes). Divided into two broad types by the Gram stain: Gram positive, Gram negative In culture, they are arranged as pairs, tetrads, clusters and chains. E.Mokaddas
8
Bacterial shapes
10/14/08
E.Mokaddas
9
The Gram Stain
10/14/08
E.Mokaddas
10
Fungi and moulds
10/14/08
Are microscopic and macroscopic, can exist as unicellular or multicellular bodies Are widely distributed in nature, like dark, moist and humid environments Cause diseases ranging from superficial to systemic infections. E.Mokaddas
11
Viruses
10/14/08
Are smaller than bacteria and are visible only with electron microscopes Are strict parasites growing only in living cells e.g. fertile eggs and tissue culture They possess a central core which is either DNA or RNA May cause disease in humans, animals, insects and plants Viruses also infect bacteria ( bacteriophages) E.Mokaddas
12
Transmission and control of microbial pathogens Definitions:
10/14/08
Host: is an organism that harbors another organism Pathogenicity: is the capacity of microorganism to cause disease A Pathogen: is an organism that is capable of causing disease Virulence: the degree of intensity of the disease produced Virulence factors: microbial factors that allow an organism to cause disease E.Mokaddas
13
10/14/08
Infection: is the invasion and damage to tissues by microorganisms Disease: the observable disturbance of the state of health whereby the body is unable to carry out normal functions Colonization: the continuing presence of microorganisms usually for weeks, months or even years without injury or invasion of host tissues Normal flora: are microorganisms that normally inhabit different body surfaces, including the skin, hair, nails, mucous membranes of the digestive tract, respiratory tract, urethra and vagina.
E.Mokaddas
14
Types of Pathogens
Primary Pathogens: Microorganisms which can cause diseases in normal hosts i.e., those with normal defense mechanism Enzymes- hyaluronidase, catalases, coagulase Avoidance of phagocytosis capsules Conventional pathogen Conditional pathogen Opportunistic pathogen: Microorganisms which do not cause disease in normal hosts but do so in hosts with impaired defenses.
10/14/08
E.Mokaddas
15
Benefits of non pathogenic microorganisms
10/14/08
1. Contribution to health e.g. normal flora 2. Food production e.g. yogurt, bread, spreads e.g vegemite 3. Chemical production- enzymes, antibiotics, vitamins 4. Genetic engineering- production of hormones, insulin etc 5. Elimination of pollution- bioremediation, degradation of toxic compounds e.g. polychlorinated biophenyls (PCB), cleaning up of oil spills
E.Mokaddas
16
Microbial pathogenesis (How microorganisms cause disease)
Adherence leads
to colonization and invasion. Adhesisn, fimbriae, pilli, capsules.
Toxin productionendotoxins, exotoxins, neurotoxins, cytotoxins Substances that damage host tissue or impede host defenses
Haemolysins, 10/14/08
E.Mokaddas
leucocidins, 17
Bacterial toxins
10/14/08
E.Mokaddas
18
Sources and reservoirs of infection
10/14/08
Source: The source of infection is the site from which spread occurs to the host. These include Inanimate objects: water, food (fruits and vegetables), equipment Animals: snails, fish, milk, uncooked or undercooked meat, fish etc. Humans: infected individuals, those incubating an illness, those with subclincal infection and those recovering from infection. Reservoir: a reservoir is the organism’s usual residence, where it reside and replicates
E.Mokaddas
19
Route of transmission:
1. Contact transmission: Direct:
person to person- skin infection Indirect contact: via an object.
2. Common vehicle : an
object touches a source or reservoir before the host
3. Airborne transmission e.g. droplet nuclei 4. Vector borne e.g. malaria, dengue (mosquitoes), Salmonella food poisoning (flies)
10/14/08
E.Mokaddas
20
Mode of transmission:
Portal of entry:
10/14/08
Faecal - oral route- (food, water), Droplet, Blood and direct contact. Mouth and gastrointestinal tract, respiratory tract, skin, genital tract.
E.Mokaddas
21
Source of transmission of microbial pathogens
Exogenous infections:
Endogenous infections: ( arising from within).
10/14/08
Arising from outside the host. Can occur by ingestion, inhalation, inoculation (insect bites), implantation ( surgical wounds or transfusion), sexual intercourse.
Occurs when normal flora becomes an conditional or opportunistic pathogen. E.Mokaddas
22
Etiology of infectious disease
10/14/08
Koch’s postulate: 1. The same pathogen must be present in every case of the disease 2. The pathogen must be isolated from the diseased host and grown in pure culture. 3.The pathogen from the pure culture must cause the disease when inoculated into a healthy susceptible laboratory animal 4. The pathogen must be re-isolated from the inoculated animal. E.Mokaddas
23
10/14/08
Exception to Koch’s postulate: 1. Koch postulates are modified to establish etiologies for diseases caused by viruses and bacteria that can not by grown on artificial media 2. Some diseases such as pneumonia and nephritis may be caused by a variety of microorganisms 3. Some pathogens e.g. Streptococcus pyogenes cause different diseases 4. Some diseases may not have well defined signs and symptoms e.g tetanus. E.Mokaddas
24
Control and prevention of infections
Health education
Personal hygiene, hand washing, food hygiene
Immunization
Passive immunization: antibody is given to protect against infection. It produces instant effect. No need for immunity to develop. Active Immunity- Vaccination:
A part of a pathogen is given ( live, killed, attenuated). Needs time for immunity to develop Antimicrobial prophylaxis. Vector control- spraying with insecticides etc.
10/14/08
E.Mokaddas
25
Laboratory diagnosis of microbial pathogens
Collection of specimens
Microscopylight microscopy: wet mount, Gram stain, Zn stain, silver stain etc. Fluorescence, dark field, electron microscopy Growth of microorganism,
10/14/08
Any tissue or body fluid can be obtained from patients and subjected to investigation. Specimens include blood, urine, faeces, sputum, tissues, pus.
Tissue culture, Culture media, animal inoculation. E.Mokaddas
26
Identification:
Antimicrobial susceptibility testing
To test for their likely response to antibiotic therapy
Bacterial typing
10/14/08
Biochemical tests, serology (antigen – antibody reactions) DNA technology, Probes. Amplification
To determine strains relatedness
E.Mokaddas
27
10/14/08
E.Mokaddas
1
History Contagion: Spread of disease
10/14/08
Pioneers responsible for the science of bacteriology: Antony van Leeuwenhoek: discovered the microscope in 1675 Louis Psteur: The founder of modern Microbiology( 1860-1890): culture methods, principles of immunization Joseph Lister: professor of surgery in Glascow. Applied Pasteur’s observations to prevention of wound sepsis. In 1867 invented antiseptic technique to kill bacteria in wounds Robert Koch: German GP who discovered the bacterial causes of many diseases including tuberculosis in 1882 ( Koch’s postulates) E.Mokaddas
2
Definitions
10/14/08
Microorganisms are minute living things that cannot be seen with the naked eye. Microbial pathogens are microorganisms that have structures or products that allow them to cause disease. Microbiology is the study of all organisms in the microscopic range. This include bacteria, fungi, algae, viruses and protozoa.
E.Mokaddas
3
Classification of Microorganisms
10/14/08
E.Mokaddas
4
Classification of Microorganisms Prokaryotes Eukaryotes Viruses Bacteria Cyanobacteria
10/14/08
Fungi Protozoa
E.Mokaddas
5
Property
10/14/08
Prokaryotic cells
Eukaryotic cells
Chromosome one number Size 1-10um
Multiple
Nuclear membrane Mitochodria
Absent
Present
Absent
Present
Ribopsomes
70s
80s
sterols
Absent
Present
E.Mokaddas
10-100 um
6
Classification of Microorganisms Nomanclature (Naming) Genus e.g. Staphylococcus Species e.g Staphylococcus aureus
10/14/08
E.Mokaddas
7
Bacteria
10/14/08
Are unicellular organisms without a defined nucleus They vary in shape, size, metabolic activity, motility, and requirement for physical and chemical agents They reproduce by asexually by binary fission They occur as cocci (spherical), bacilli ( rods) spirilli (spirals), vibros (coma shaped) , wavy (spirochetes). Divided into two broad types by the Gram stain: Gram positive, Gram negative In culture, they are arranged as pairs, tetrads, clusters and chains. E.Mokaddas
8
Bacterial shapes
10/14/08
E.Mokaddas
9
The Gram Stain
10/14/08
E.Mokaddas
10
Fungi and moulds
10/14/08
Are microscopic and macroscopic, can exist as unicellular or multicellular bodies Are widely distributed in nature, like dark, moist and humid environments Cause diseases ranging from superficial to systemic infections. E.Mokaddas
11
Viruses
10/14/08
Are smaller than bacteria and are visible only with electron microscopes Are strict parasites growing only in living cells e.g. fertile eggs and tissue culture They possess a central core which is either DNA or RNA May cause disease in humans, animals, insects and plants Viruses also infect bacteria ( bacteriophages) E.Mokaddas
12
Transmission and control of microbial pathogens Definitions:
10/14/08
Host: is an organism that harbors another organism Pathogenicity: is the capacity of microorganism to cause disease A Pathogen: is an organism that is capable of causing disease Virulence: the degree of intensity of the disease produced Virulence factors: microbial factors that allow an organism to cause disease E.Mokaddas
13
10/14/08
Infection: is the invasion and damage to tissues by microorganisms Disease: the observable disturbance of the state of health whereby the body is unable to carry out normal functions Colonization: the continuing presence of microorganisms usually for weeks, months or even years without injury or invasion of host tissues Normal flora: are microorganisms that normally inhabit different body surfaces, including the skin, hair, nails, mucous membranes of the digestive tract, respiratory tract, urethra and vagina.
E.Mokaddas
14
Types of Pathogens
Primary Pathogens: Microorganisms which can cause diseases in normal hosts i.e., those with normal defense mechanism Enzymes- hyaluronidase, catalases, coagulase Avoidance of phagocytosis capsules Conventional pathogen Conditional pathogen Opportunistic pathogen: Microorganisms which do not cause disease in normal hosts but do so in hosts with impaired defenses.
10/14/08
E.Mokaddas
15
Benefits of non pathogenic microorganisms
10/14/08
1. Contribution to health e.g. normal flora 2. Food production e.g. yogurt, bread, spreads e.g vegemite 3. Chemical production- enzymes, antibiotics, vitamins 4. Genetic engineering- production of hormones, insulin etc 5. Elimination of pollution- bioremediation, degradation of toxic compounds e.g. polychlorinated biophenyls (PCB), cleaning up of oil spills
E.Mokaddas
16
Microbial pathogenesis (How microorganisms cause disease)
Adherence leads
to colonization and invasion. Adhesisn, fimbriae, pilli, capsules.
Toxin productionendotoxins, exotoxins, neurotoxins, cytotoxins Substances that damage host tissue or impede host defenses
Haemolysins, 10/14/08
E.Mokaddas
leucocidins, 17
Bacterial toxins
10/14/08
E.Mokaddas
18
Sources and reservoirs of infection
10/14/08
Source: The source of infection is the site from which spread occurs to the host. These include Inanimate objects: water, food (fruits and vegetables), equipment Animals: snails, fish, milk, uncooked or undercooked meat, fish etc. Humans: infected individuals, those incubating an illness, those with subclincal infection and those recovering from infection. Reservoir: a reservoir is the organism’s usual residence, where it reside and replicates
E.Mokaddas
19
Route of transmission:
1. Contact transmission: Direct:
person to person- skin infection Indirect contact: via an object.
2. Common vehicle : an
object touches a source or reservoir before the host
3. Airborne transmission e.g. droplet nuclei 4. Vector borne e.g. malaria, dengue (mosquitoes), Salmonella food poisoning (flies)
10/14/08
E.Mokaddas
20
Mode of transmission:
Portal of entry:
10/14/08
Faecal - oral route- (food, water), Droplet, Blood and direct contact. Mouth and gastrointestinal tract, respiratory tract, skin, genital tract.
E.Mokaddas
21
Source of transmission of microbial pathogens
Exogenous infections:
Endogenous infections: ( arising from within).
10/14/08
Arising from outside the host. Can occur by ingestion, inhalation, inoculation (insect bites), implantation ( surgical wounds or transfusion), sexual intercourse.
Occurs when normal flora becomes an conditional or opportunistic pathogen. E.Mokaddas
22
Etiology of infectious disease
10/14/08
Koch’s postulate: 1. The same pathogen must be present in every case of the disease 2. The pathogen must be isolated from the diseased host and grown in pure culture. 3.The pathogen from the pure culture must cause the disease when inoculated into a healthy susceptible laboratory animal 4. The pathogen must be re-isolated from the inoculated animal. E.Mokaddas
23
10/14/08
Exception to Koch’s postulate: 1. Koch postulates are modified to establish etiologies for diseases caused by viruses and bacteria that can not by grown on artificial media 2. Some diseases such as pneumonia and nephritis may be caused by a variety of microorganisms 3. Some pathogens e.g. Streptococcus pyogenes cause different diseases 4. Some diseases may not have well defined signs and symptoms e.g tetanus. E.Mokaddas
24
Control and prevention of infections
Health education
Personal hygiene, hand washing, food hygiene
Immunization
Passive immunization: antibody is given to protect against infection. It produces instant effect. No need for immunity to develop. Active Immunity- Vaccination:
A part of a pathogen is given ( live, killed, attenuated). Needs time for immunity to develop Antimicrobial prophylaxis. Vector control- spraying with insecticides etc.
10/14/08
E.Mokaddas
25
Laboratory diagnosis of microbial pathogens
Collection of specimens
Microscopylight microscopy: wet mount, Gram stain, Zn stain, silver stain etc. Fluorescence, dark field, electron microscopy Growth of microorganism,
10/14/08
Any tissue or body fluid can be obtained from patients and subjected to investigation. Specimens include blood, urine, faeces, sputum, tissues, pus.
Tissue culture, Culture media, animal inoculation. E.Mokaddas
26
Identification:
Antimicrobial susceptibility testing
To test for their likely response to antibiotic therapy
Bacterial typing
10/14/08
Biochemical tests, serology (antigen – antibody reactions) DNA technology, Probes. Amplification
To determine strains relatedness
E.Mokaddas
27
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