Medical Microbiology Midterm

How did the first cell nucleus arise?

A large DNA-based virus took up residence in a bacterial cell

What role did Norman George Heatley play in penicillin?

• Devised an assay method to measure penicillin known as Oxford units

• Found the appropriate conditions under which penicillin is stable

• Worked with Florey to demonstrate penicillin’s abilities in animals

What diseases do prions cause?

Transmissible spongiform encephalopathies (TSEs)

What did Louis Pasteur do?

• Disproved spontaneous generation

• Proved Germ Theory

• Created the first rabies vaccine

Who was the founder of modern bacteriology?

Robert Koch

Robert Koch identified the specific causative agents of which diseases?

Tuberculosis, cholera, and anthrax

What is Germ Theory?

Microorganisms known as pathogens cause diseases

What award did Robert Koch win, and in what year?

The Nobel Prize in Physiology or Medicine in 1905

What are Koch’s postulates?

A set of four experimental criteria to link a specific microbe to a specific disease

1. The microbe must be found in all cases of the disease but absent in a healthy individual

2. The microbe is isolated and grown in pure culture

3. When introduced to a healthy individual, the microbe causes the disease

4. The microbe is extracted from the host upon death

What award did Fleming, Florey, and Chain win, and in what year?

The Nobel Prize in Physiology or Medicine in 1945

What are five parasitic infections? (2 Cs, 3 Ts)

1. Chagas Disease

2. Cysticercosis

3. Toxocariasis

4. Toxoplasmosis

5. Trichomoniasis

What did Dr. Ignaz Semmelweis discover, and how?

Handwashing prevents the spread of infection diseases. He noticed that the midwives had 3x more success than the physicians and medical students because they came out of the labs and surgeries without washing their hands.

What are three waterborne diseases that chlorination helps prevent?

Cholera, typhoid, and dysentery

Our           matter! Being a healthy human is impossible without them.

Microbes

What is our continuous goal?

To restore the balance of microbes so that they will work in harmony with the human body

What are noncommunicable infections?

Diseases spread by infectious agents but not spread directly from person to person

What are communicable infections?

Diseases caused by infectious agents that spread by direct contact or contamination

What is infectivity?

The frequency by which an infectious disease spreads from an infected person to a suspectible personW

What is the disease index?

The number of people who get the disease divided by the number of people who get infected

What is virulence?

The number of fatal or severe cases divided by the total number of cases

What is incidence?

The number of new cases divided by the number of people at risk

What is prevalence?

The total number of cases divided by the total population

What microbes make up the human microbiome?

Bacteria, viruses, fungi, and protozoa

What are four things our microbes in the microbiome do for us?

1. Produce vitamins that we can’t

2. Help break down food for us

3. Help strengthen the immune system

4. Help fight off disease-causing organisms

You are only what percent human?

0.5%

Our relationship with microbes is not just one of             but of               

Tolerance, encouragement

What are babies who are born via C-section more at risk for?

Immune and metabolic disorders, including

1. Type 1 Diabetes

2. Asthma

3. Allergies

4. Obesity

Where is there bacterial DNA in the birth environment, and what does this suggest?

The placenta and amniotic fluid. This suggest “in utero colonization.”

What are Crohn’s Disease and Ulcerative Colitis, two types of Inflammatory Bowel Diseases (IBDs), linked to?

The overall ecology of the human gut microbial environment, including

1. Community diversity

2. A range of microbial enrichments and deplitions

3. Imbalance or disruption in microbial metabolic activities 

How many species of microbes are in the colon?

About 1 trillion

What do the microbes in the colon do?

Pick up scraps of food and convert them into energy

What are the colonic cells’ main energy source?

The waste products of the colon’s microbes

About how many species of bacteria can be found in the stool?

4,000 species from all over the body

What benefits do Bacteroides provide?

They help shape the intestinal walls

What benefits do Klebsiella provide?

They have a gene to produce vitamin B12, which is essential for brain function

What is the heart of the human body’s microbial community?

The cecum/caecum

What is the function of the cecum?

They make the most of the partially digested food that has gone through round 1 of the nutrient extraction process in the small intestine. The plant fibers are left for the microbes to tackle in round 2.

What is the function of the appendix?

It is a safehouse for microbial inhabitants and can repopulate the gut with its normal microbial inhabitants if needed.

What does the appendix protect us from?

Recurring GI infections, immune dysfunction, some autoimmune diseases, blood cancer, and heart attacks

What were the goals of the human microbiome project?

1. Determine if there is a set of microbes common to humans.

2. Understand if changes in the microbiota correspond to changes in health or disease.

3. Develop new technologies for examining complex micobial systems in their natural environment.

4. Begin to deal with the legal, social, and ethical complications that may arise with studying the human microbiome.

What are three “good” bacteria?

Bifidobacteria, E. coli, Lactobacilli

What are three “bad” bacteria?

Camplyobacter, Enterococcus faecalis, Clostridium difficule

What does Clostridium difficule infection cause?

• Pseumembranous colitis (inflammation of the colon)

• Toxic megacolon (enlargement of the colon)

• Sepsis

• Death

What are two ways Clostridium difficule infection is transmitted?

• Contamination by fecal oral transmission

• The contaminated hands of a healthcare personnel

What antibiotics are linked to Clostridium difficule infection?

Clindamycin, penicillins, and cephalosporins

How do bacteria produce energy?

1. Bacterial proton pumps pump H+ from the cytoplasm to the periplasmic space

2. H+ flows from the periplasmic space to the cytoplasm through ATPase to make ATP

Facultative anaerobes

Can perform anaerobic glycolysis (producing lactate) when there is no O₂ but can perform aerobic respiration where there is O₂

How often do bacteria develop a mutation for resistance?

1 in every 10⁸-10⁹

What are the three methods of gene mutation in bacteria?

1. Base substitution

2. Insertion and Deletion

3. Transposable elements

What are the three methods of gene transfer in bacteria?

1. Transformation: takeup of naked DNA

2. Transduction: DNA is transferred by a virus (bacteriophage)

3. Conjugation: direct cell-to-cell contact to transfer genetic material, usually a plasmid

What are three ways to identify microbes?

Culture media, staining, and microscopy

What does TSP broth contain?

All the nutrients bacteria need

What does blood agar contain, and what is it helpful in identifying?

Red blood cells. It is helpful in identifying hemolytic bacteria.

What does selective media do?

Discourages the growth of unwanted bacteria and encourages the growth of wanted bacteria

What does differential media do?

Provides the environment to tell bacteria apart

What does enriched media have?

Contains the nutrients for the specific needs of the bacteria being cultured

What is the process of Gram staining?

1. Crystal violet staining

2. Iodine treatment, which kills cells and fixes them in place

3. Decolorization with alcohol

4. Staining Gram-negative bacteria with safranin dye

What do Gram-negative bacteria have that Gram-positive bacteria don’t have?

A thinner peptidoglycan layer, lipoproteins, lipopolysaccharides, and an outer membrane

What are the phases of microbial growth?

1. Lag phase: microbes are adapting

2. Log phase: phase of optimal population growth

3. Stationary phase: population levels out

4. Death phase: waste and dead cells accumulates

   1. Spore formers can persist beyond the death phase and regenerate a population if conditions are favorable

By what five methods can antimicrobial agents inhibit growth or kill microbes?

Inhibit

1. Nucleic acid formation

2. Protein synthesis

3. Cell wall formation

4. Formation of metabolic products

Damaging of the plasma membrane

What are the three mechanisms of antibiotic resistance?

1. Efflux pumps: pump the antibiotic out the cell

2. An enzyme that modifies the antibiotic such that it loses activity

3. An enzyme that degrades the antibiotic to inactivate it

How does streptomycin resistance work?

An enzyme modifies the antibiotic such that it loses activity

How does penicillin resistance work?

Penicillinases degrade the antibiotic

Viral infections are often systemic but can be local (e.g., conjunctivitis and herpes). What does systemic mean?

Spread throughout the body and affecting multiple organs rather than being localized at the site of infection

What are the symptoms of a bacterial infection?

Local pain, including localized

1. Redness

2. Heat

3. Swelling

4. Pain

What are the primary organs of the immune system and their functions?

1. Thymus: where T cells mature

2. Bone marrow: makes white blood cells destined to become lymphocytes; where B cells mature

What are the secondary organs of the immune system and their functions?

1. Adenoids: trap and filter bacteria that enter through the nose and mouth

2. Tonsils: trap and filter bacteria that enter through the nose and mouth

3. Peyer’s patches: masses of lymphatic tissue found in the ilium in the small intestine

   1. Monitor bacterial populations in the intestine

   2. Prevent the growth of pathogenic bacteria in the intestine

4. Lymph nodes: small bean-shaped structures that make and store cells that fight off disease; can swell when you become sick because it traps and destroys viruses and waste products accumulate

5. Spleen: largest lymphatic organ, contains white blood cells, controls blood volume

6. Appendix: safehouse for microbial inhabitants

What is the first line of immune defense?

The passive mechanisms

1. Skin

2. Mucous membranes

What is the second line of immune defense?

Non-specific innate immunity

1. Inflamation

2. Complement proteins

3. Natural killer (NK) cells

What is the third line of immune defense?

Specific acquired immunity

1. Humoral immunity

2. Cell-mediated immunity

What cells release histamine?

1. Mast cells (white blood cells that live in the tissues)

2. Basophils (white blood cells that circulate in the blood and travel to the tissue during inflammation)

What are the two physiological responses in inflammation?

1. Blood vessel dialate

2. Capillaries become leaky

Why do the capillaries become leaky in inflammation?

This allows plasma and immune cells to move from the blood to the tissues to fight infection

What is the role of neutrophils in inflammation?

They are phagocytes that consume and destroy the antigen

What are the four functions of the complement system? Describe each.

1. Opsonization: enhancing the phagocytosis of antigens

2. Chemotaxis: moving macrophages and neutrophils to the site of the injury

3. Cell lysis: rupturing the cell membrane of foreign invaders

4. Agglutination: the sticking together of pathogens

What do natural killer (NK) cells do?

Kill cells infected by viruses and cancerous cells without knowing the antigen

What cells does humoral immunity focus on?

B cells

What are the two places in which antibodies are found?

1. B cell surface receptors

2. Plasma

Where do B cells and T cells originate?

The bone marrow

What do helper T cells do?

Activate cytotoxic T cells and B cells

What do cytotoxic T cells do?

Kill virus-infected cells or cancerous cells

What do suppresor T cells do?

Mediate the immune response to prevent autoimmune disease

What are three places the T cells migrate to?

1. Tissue fluid

2. Lymph nodes

3. Other organs, like the spleen

What do T cells attack?

1. Cells infected by microorganisms, commonly viruses

2. Transplanted organs and tissues

3. Cancerous cells

What do plasma cells make?

Antibodies

What did Paul Ehrlich do?

1. Develop a cure for syphilis

2. Develop acid-fast stain

Who developed the Gram stain?

Christian Gram

Who invented the Petri dish?

R.J. Petri

What did Martinus Beijerinck do?

Recognized the viral dependence on cells for reproduction

What did Walter Reed prove?

Mosquitoes can carry yellow fever

What did W. Gilbert and F. Sanger develop?

A method to sequence DNA

What did Kary Mullis do?

Invented PCR

What did TIGR do?

Published the first microbial genome sequence

Who observed “little animals”?

Antony Leeuwenhoek

What is the method of resistance for tetracycline?

Efflux pumps

What are the components of an operon?

Regulator gene, promoter, operator, structural genes

What attaches to the operator to prevent RNA polymerase from binding at the promoter to transcribe DNA?

A repressor protein

What are the four components of the immune system? (WACH)

1. White blood cells

2. Antibodies

3. Complement system

4. Hormones

What are two examples of protozoa?

Amoeba and paramecium

How much of the oxygen we breathe is generated by microbes?

At least 50%