Microbiology Lect 18

Question 1

What is the relation between microbes used in food production and those that cause food spoilage?

Answer 1

We use the same genus a lot of the time, but not the same species, and they are used intentionally/in different ways

Question 2

Ergot of Rye

Answer 2

-Claviceps purpurea
-Causes Ergotism
-Historical significance, such as in St. Anthony’s Fire and the Salem Witch Trials

Question 3

What is the nomenclature for organisms?

Answer 3

Domain → Kingdom → Phylum → Class → Order → Family → Genus → Species
-Naming is genus species

Question 4

Bacterial Soft Rot

Answer 4

-Erwinia carotovora (Enterobacteriaceae)
-Vegetables and fruits susceptible
-Greatest losses when food is stored improperly

Question 5

Fruit and bread molds

Answer 5

-Fungi:
-Penicillium species
-Rhizopus stolonifer
-Low pH: fungi
-Bacteria: Serratia marcescens
-neutral or high pH: bacteria

Question 6

Alfatoxins overall

Answer 6

-Made by Aspergillus (ascomycota)
-Some of the most toxic compounds produced by fungi
-Carcinogenic, liver damage and liver cancer
-Contaminates foods before harvest or during storage
-Frequently found in food crops such as peanuts and corn

Question 7

Alfatoxins regulation

Answer 7

-US FDA has strict limits on how much is allowed in food for human and livestock/animal consumption
-Recalls are common
-In 2006, over 70 dogs died from eating one brand of pet food

Question 8

What are the different types of Ergotism?

Answer 8

-Convulsive: seizures, spasms, psychosis, nausea
-Vasoconstrictive: gangrene, edema, low blood pressure

Question 9

What is the modern significance of ergot?

Answer 9

-Vasoconstrictive properties led to use inhibiting postpartum bleeding and migraine treatment
-Synthetic development of hallucinatory compounds such as LSD

Question 10

How was LSD created?

Answer 10

First synthesized in 1938 by Sandoz laboratories, when they were looking into ergot alkaloid derivates for therapeutic uses

Question 11

How did LSD affect the 1960s?

Answer 11

-Counterculture of the 1960s was heavily influenced by LSD
-LSD impacted the colors, clothing, art, ideology, and music

Question 12

What methods are used to control food spoilage?

Answer 12

-Kill or remove microbes
-Heat sterilization
-Irradiation
-Filtration
-Inhibit microbial growth
-Drying (decrease water activity, such as salting and jellies)
-Refrigeration
-Addition of chemical inhibitors

Question 13

What is a pathogen?

Answer 13

A disease-causing agent

Question 14

Pathogenicity

Answer 14

Ability to cause disease

Question 15

Virulence

Answer 15

Severity of disease (degree of pathology)

Question 16

How do we classify pathogens?

Answer 16

-Primary pathogens: capable of causing disease in healthy hosts
-Must have a way/special adaptation to breach the immune system defenses
-Opportunistic pathogen: cause disease in immunocompromised host

Question 17

What is the pathogenicity and virulence of Rhinovirus (the common cold) and Ebola virus?

Answer 17

Rhinovirus:
-Pathogenicity: high
-Virulence: Low
Ebola virus:
-Pathogenicity: high
-Virulence: High

Question 18

What causes someone to be immunocompromised?

Answer 18

-Extremes in age
-Presence of other diseases (especially HIV/AIDS)
-Lack of proper nutrition
-Genetic defects in immunity
-Induction by drugs (ex: for organ transplant)

Question 19

What are most fungal pathogens classified as?

Answer 19

-Opportunistic
-Many human deaths from fungal diseases occur in AIDS patients

Question 20

What are the elements of pathogenesis?

Answer 20

-Maintain a reservoir
-Transport to host
-Invade and colonize host
-Evade host defenses
-Multiply in host
-Damage host
-Leave host

Question 21

Pathogen reservoir (elements of pathogenesis)

Answer 21

-An animal or place where a pathogen can be found before or after an infection
-Important as source of infection
-Can also be necessary for pathogen survival
-Ex: Yersinia pestis reservoir is rats, while the vector is fleas

Question 22

What are common modes of transport? (elements of pathogenesis)

Answer 22

-Via other animals, the animal can be a vector or the pathogen can be zoonotic
-Sexual transmission
-Water-borne pathogens (Fecal-oral route)
-Air-borne pathogens
-Wound-related pathogens (rarer)

Question 23

How do pathogens invade and colonize the host? (elements of pathogenesis)

Answer 23

-Adhesins are microbial factors that promote attachment to the host surface

Question 24

How do pathogens evade host defenses? (elements of pathogenesis)

Answer 24

-Avoid being recognized (ex: Lyme disease)
-Resist phagocytosis
-Survive (persist) in phagocytic cells (ex: Rikettsia)
-Destroy antibodies

Question 25

Lyme Disease

Answer 25

-Borrelia burgdorferi
-Decreases surface proteins recognized by host
-Resides in biofilm

Question 26

How is phagocytosis prevented?

Answer 26

-Capsules ((polysaccharide?) layer around cell wall)

Question 27

What is an example of avoiding antibodies?

Answer 27

-ImmunoglobulinA (IgA) proteases break down IgA in host

Question 28

How is a host damaged? (elements of pathogenesis)

Answer 28

-Trigger exaggerated immune response
-Toxins

Question 29

What is an example of an exaggerated immune response?

Answer 29

-Mycobacterium tuberculosis
-Granulomas: many immune cells aggregate to “Wall off infection”
-Pathogen get a free hide out within which grow and multiply

Question 30

Exotoxins

Answer 30

Soluble proteins released outside cell

Question 31

Endotoxins

Answer 31

-Released only when the cell lyses, eliciting immune response
-Usually outer membrane lipopolysaccharides (LPS)

Question 32

Tetanus/”Lockjaw”

Answer 32

-Clostridium tetani: aeorbic soil Firmicute bacteria
-Secretes exotoxin, a neurotoxin (tetanospasmin)
-Causes muscle spasms, can tear muscle fibers
-Lethal dose of tetanospasmin for adult: 175 ng
- ~50,000 death per year, ~45% of tetanus infections lead to death

Question 33

How do pathogens leave the host? (elements of pathogenesis)

Answer 33

-Sexual contact
-Vertical transmission (parent to offspring)
-Feces (fecal-oral route)
-Coughing
-Vector-borne