Lecture 20- Bacteria & Human/Animal Disease

Question 1

What do we mean when we say bacteria are ubiquitous?

Answer 1

they are everywhere (soil,water,air,mud,saliva,skin,etc)

Question 2

Are most bacteria beneficial or harmful?

Answer 2

vast majority are beneficial?

Question 3

Explain the ways that bacteria can be beneficial

Answer 3

• some produce drugs &chemicals (ethanol, acetic acid, streptomycin- an antibiotic)
• some produce food products (cheese,butter,yogurt)
• Saprophytes break down organic matter
• legumenous bacteria fix N₂ to Nitrates, amino acids etc

Question 4

What is infection?

Answer 4

the process of microbial invasion & multiplication in body of a human/animal

Question 5

What is an infectious disease>

Answer 5

diseases caused by an infectious agent (spreads easily from person to person)

Question 6

What are some of the way infectious diseases cons be spread?

Answer 6

• direct contact with body
• contact with contaminated items
• breathing in exhaled air

Question 7

What type of bacteria are flora, where are get located, and how do they obtain energy?

Answer 7

• they are commensals heterotrophs
• live on skin,mucous membranes of (mouth,vagina,upper respiratory tract, intestines)
• contain energy from secretions/food residues
• Generally harmless but opportunistic when immune system impaired (may invade tissue & cause disease)

Question 8

What are frank pathogens?

Answer 8

• true pathogens that overcome normal body defense& invade tissue
• ‘growth or production of toxins damages tissue, causing disease

Question 9

Which. Bacterium did Koch test mice on?

Answer 9

Anthrax

Question 10

What is Koch’s postulate?

Answer 10

a postulate establishing a causal relationship between a pathogen & a specific disease

• A Frank pathogen must be found in body of all cases of that disease
• should be isolated from a known animal that has disease and growin in pure culture in vitrio & characterized (study properties)
• inject pathogen into a healthy susceptible,animal
• reisolate organism & reidentify

Question 11

What is a Localized and what is a systemic infection?

Answer 11

localized infection- confined to small body area

systemic infection- spreads throughout body

Question 12

What is the difference between primary, secondary, and mixed infection?

Answer 12

primary infection is caused directly by organism

Secondary infection is an organism that causes a disease opportunistically (commensals)

mixed infection is an infection caused by 2+ Organisms

Question 13

What is a Nosocomial infection?

Answer 13

An opportunistic infection acquired in the hospital

Question 14

What is bacteremia and Septicemia?

Answer 14

Bacteremia- bacteria present in blood

Septicemia- bacteria & harmful products (toxins) present in blood

Question 15

What are the primary defended against infection?

Answer 15

• Normal intact skin
• microbial flora
• mucous membranes
• fluid flow (tears,urine.saliva)

Question 16

What are the chemical defenses the body has against infection?

Answer 16

• Enzymes (lysozymes in tears,saliva,human milk, mucous)
• Acidity (fatty acids on skin 3-5 , lactic acid in vagina, HCl I’m stomach)- low Ph retards bacterial growth

Question 17

What are the frequent ports of entry of infectious agents?

Answer 17

• Respiratory tract
• GI(gastrointestinal) tract
• urinary & genital tracts
• cuts/burns in mucous membranes or skin

Question 18

What must bacterial cells do in order to enter cells and multiply?

Answer 18

Adhere to cells, using Adherence factors (fimbriae, capsule)

then they produce hydrolytic enzymes (proteases,lipases,etc)

*some do both, some do one of these steps

Question 19

What is another name for the properties of pathogenic bacteria that allow transmition of disease (easy transmissibility, adherence, etc)

Answer 19

Virulence factors

Question 20

What are toxoids?

Answer 20

neutralized form of exotoxins, can be injected as a vaccine

Question 21

What are exotoxins?

Answer 21

Proteins secreted by some G+ & G- bacteria that are

• heat sensitive
• highly toxic (Tetanus,Diptheria,Cholera)
• antigenic (stimulate cells to make antibodies )
• usually bind to specific receptors
• Include neurotoxins (Tetanus)
• include cytotoxins (Diptheria)
• include enterotoxins- toxic to intestine (Cholera)

Question 22

What is an Endotoxin?

Answer 22

LPS (lipopolysaccharide of G- cell Wall) ONLY

• Moderately toxic- released when bacterial cell lysis
• ​heat stable
• ​cannot be converted to toxoids

Question 23

Under what circumstance can endotoxic shock take place, and what are the consequences?

Answer 23

during septicemia, causing impaired functioning of essential organs

• heart
• brain
• kideney (etc)

Question 24

What other cell components other than endo and exo toxins are toxic?

Answer 24

• ​PG monomers
• teichoic acid of Gram +
• mycolic acids of mycobacterium & other acid fast

Question 25

What is the ability of the bacteria to change its fimbria called?

Answer 25

**Antigenic variation**

Question 26

Is it possible to kill bacteria that have fully formed their spores?

Answer 26

**No**, they are **dormant**, **not fully alive** (not metabolizing )

Question 27

What are the variables that control bacterial population?

Answer 27

* **Competition** for **limited nutrients** * **temp** * **humidity** * **Salinity** * **presence of bacteriophages (***T4 kills E coli***)**

Question 28

Describe T4 bacteriophage cycle

Answer 28

* **Attachment** of Bacteriophage to specific **outer surface receptors** of É coli * **injection of DNA,** by **contraction** of **sheath tail** * **Hydrolysis** of DNA & **synthesis of viral genomes & proteins** * **Assembly** of bacteriophage **3 sets** of proteins **heads**, **tails**,and **tail fibers**- phage genome packaged in capsid **while head forms** * **lysis** of bacterial cell by phage directing production of an **enzyme** that **damages cell wall**, allowing **fluid to enter 100-200 phage exit**

Question 29

What are Disinfectants and antiseptics?

Answer 29

Disinfectants-chemicals used to **kill vegetative** bacterial cells from **inanimate** objects (chair,table.etc) Antiseptics- Chemicals used on **living tissue** (skin) to **inhibit growth** or **kill bacteria**

Question 30

What are antibacterial agents?

Answer 30

chemicals used to control bacterial growth during an **infection** they are **antibiotics** and can be **fully natural** **semi-synthetic** (made from natural) **Synthetic**- made from man made drugs

Question 31

What is the difference between broad and narrow spectrum antibiotics, and how can these antibacterial agents work (broadly)

Answer 31

Broad spectrum are effective against many gram **+ &** gram **-** narrow spectrum- kill **only** gram **+** or gram **-** or **few bacteria** are either **Bactericidal-** **lysis kill bacteria** ​ **Bacteriostatic-** **inhibit growth** for long enough for immune system to kill them

Question 32

Give specific ways antibacterial agents can work

Answer 32

* inhibit **cell wall synthesis** - causing **osmotic lysis**- l*ow toxicity* (**penicillin, cephalosporin**) * **alter ribosomes -** faulty protein synthesis affect **30S (streptomycin)** affect **50S (erythromycin)** * inhibit **Nucleic acid synthesis -** topisomersde & DNA replication inhibition (**quinolone)** * inhibit bacterial **RNA** synthesis (**Rifampicin)**