Microbiology

Microbiology

• The study of organisms too small to be seen without magnification.– Bacteria– Viruses– Fungi– Protozoa– Helminths (worms)– algae

Branches of study within microbiology

• Immunology

• Public health microbiology & epidemiology

• Food, dairy and aquatic microbiology

• Biotechnology

• Genetic engineering & recombinant DNA technology

Microbes are involved in

• Nutrient production & energy flow

• Decomposition

• Production of foods, drugs & vaccines

• Bioremediation

• Causing disease

Impact of pathogens

• Nearly 2,000 different microbes cause diseases.

• 10 billion infections/year worldwide.

• 13 million deaths from infections/year worldwide.

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Characteristics of microbes

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Antonie van Leeuwenhoek

• First to observe living microbes

• his single-lens magnified up to 300X

(1632-1723)

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Spontaneous generation

Early belief that some forms of life could arise from vital forces present in

nonliving or decomposing matter.

(flies from manure, etc)

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Louis Pasteur

• Showed microbes caused fermentation & spoilage

• Disproved spontaneous generation of m.o.

• Developed aseptic techniques.

• Developed a rabies vaccine.

(1822-1895)

Germ theory of disease

Many diseases are caused by the growth of microbes in the body and not by sins,

bad character, or poverty, etc.

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Robert Koch

• Established a sequence of experimental steps to show that a specific m.o. causes a particular disease.

• Developed pure culture methods.

• Identified cause of anthrax, TB, & cholera.

(1843-1910)

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3 domains

• Eubacteria -true bacteria, peptidoglycan

• Archaea –odd bacteria that live in extreme environments, high salt, heat, etc

• Eukarya- have a nucleus, & organelles

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Taxonomy - system for organizing, classifying & naming living things

• Domain - Archaea, Bacteria & Eukarya

• Kingdom - 5• Phylum or Division• Class • Order• Family• Genus• species

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Naming micoorganisms

• Binomial (scientific) nomenclature • Gives each microbe 2 names

– Genus - noun, always capitalized– species - adjective, lowercase

• Both italicized or underlined– Staphylococcus aureus (S. aureus)– Bacillus subtilis (B. subtilis)– Escherichia coli (E. coli)

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Epidemiology

• The study of the frequency and distribution of disease & health-related factors in human populations

• Surveillance –collecting, analyzing, & reporting data on rates of occurrence, mortality, morbidity and transmission of infections

• Reportable, notifiable diseases must be reported to authorities

Communicable disease – can be spread.

Noncommunicable – cannot be spread from one person to another.

Black Plague killed 200

million

Small pox killed 1/3 of

Europe in 1348.

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• Centers for Disease Control and Prevention (CDC) in Atlanta, GA – principal government agency responsible for keeping track of infectious diseases nationwide

• http://www.cdc.gov

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• Prevalence – total number of existing cases with respect to the entire population usually represented by a percentage of the population

• Incidence – measures the number of new cases over a certain time period, as compared with the general healthy population

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• Mortality rate – the total number of deaths in a population due to a certain disease

• Morbidity rate – number of people afflicted with a certain disease

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• Endemic – disease that exhibits a relatively steady frequency over a long period of time in a particular geographic locale

• Sporadic – when occasional cases are reported at irregular intervals

• Epidemic – when prevalence of a disease is increasing beyond what is expected

• Pandemic – epidemic across continents

Reservoirs of Infection

• Primary habitat in the natural world of a pathogen.

• Living reservoirs may or may not have symptoms.

• Vectors – living animal that transmits infectious disease.

• Nonliving reservoirs – soil, water

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Vectors

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Patterns of transmission

• Direct contact

• Indirect contact– Vehicle – inanimate material, food, water,

biological products, fomites

– Airborne – droplet nuclei, aerosols

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Nosocomial infections

• Diseases that are acquired during a hospital stay

• Most commonly involve urinary tract, respiratory tract, & surgical incisions

• Most common organisms involved gram-negative intestinal flora, E. coli, Pseudomonas, Staphylococcus

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Koch’s postulates

1. Find evidence of a particular microbe in every case of a disease

2. Isolate that microbe from an infected subject and cultivate it artificially in the laboratory

3. Inoculate a susceptible healthy subject with the laboratory isolate and observe the resultant disease

4. Reisolate the agent from this subject

Bacteria

Binary Fission

• Reproduction

• One cell grows to about double its original size and then splits.– Dna replicates– divides

Shapes of Bacteria

Coccus – spherical or oval shaped.

-diplococcus: cocci in pairs

-streptococcus: cocci in chains

-tetrad: arranged in squares of 4

-sarcina: arranged in cubes of 8

-staphylococcus: random planes

diplococcus

streptococcus

Tetrad

sarcina

staphylococcus

Bacillus

• Rod-shaped bacteria

Bacillus

Bacillus under scanning electron microscope

Escherichia coli

Spiral

• 3 forms: vibrio, spirillum, spirochete

Vibrio cholerae

Spirillum

Spirochete

Identifying Bacteria

• Gram Positive

• Gram Negative

• Shape

Gram-Positive

• After being stained appears purple.

• Due to a peptidoglycan wall.

• Thicker wall

Gram-negative

• Appears red when gram stained.

• Picks up safranin stain.

• Thin wall.

How they use oxygen?Facultative anaerobe - Prefer to

grow in the presence of oxygen, but can grow in an anaerobic environment using fermentation.

Strict Aerobe

• Cannot survive in the absence of oxygen.

Strict Anaerobe

• Generate energy by fermentation and are killed in the presence of oxygen.

Thioglycollate agar

• determines the oxygen relationship of a microorganisms.

• Contains: thioglycollic acid, cystine and 0.35% agar.

• The thioglycollic acid and agar prevent oxygen from entering the entire medium.

Autoclave

• Pressurized device designed to elevate temperature and pressure to sterilize material and solutions.

Media

• Liquid media

• Semi-solid media

• Solid media

Semi-solid media

• Can be used for motility testing.

Solid Media

• Contains more agar = where microbes grow.

• This enables the formation of colonies.

Different Media

• Grows all: Some agar grows everything.

• Differential media: Some shows different reactions.

• Selective media: Some can grow certain bacteria.

MacConkey Agar

• Differential media.

• Detects lactose fermentation.

Viewing Microbes

• Resolution(seeing detail) can be increased using immersion oil.

• Allows the light ray to go directly through the objective lens.

Gram Stain

• Fix microbe onto slide.• 20 secs. Crystal Violet• Rinse with water• 15 secs. Iodine• Rinse with water• Alcohol rinse• 20 secs. Safranin • Rinse with water