Lesson 1.2: Antibiotic Treatment

What is bacterial mutation?

A change in the DNA that can sometimes cause a change in the gene product, the target of the antimicrobial

How does the zone of inhibition indicate wether the antibiotic is effective or not?

A larger zone of inhibition around an antibiotic-containing disk indicates that the bacteria are more sensitive to the antibiotic in the disk. ... If an antibiotic stops the bacteria from growing, one can see circular areas around the disks where bacteria have not grown.

Plasmid

A small ring of DNA that carries accessory genes separate from those of the bacterial chromosome

Antibiotic

A substance produced by or derived from a microorganism and able in dilute solution to inhibit or kill another microorganism

How were the results after 48 hours different from the results after 24 hours?

All antibiotics that had an effect at the 24 hour mark had larger zones of inhibition at the 48 hour mark for B. Cereus. On the other hand, at the 24 hour mark only 2 zones of inhibition were present (for 2 antibiotics) while there were 5 at the 48 hour mark.

How do antibiotics attack bacterial cells but not human cells?

Attack walls of bacterial cells by preventing the synthesis of peptidoglycan

What is bacterial destruction and inactivation?

Bacteria genes produce enzymes that chemically degrade or inactivate microbial activity within the bacterial cell

What is transduction?

Bacteriaphage attach to bacterial cell and incorporate bacterial DNA into own DNA. When cell dies, phage infects other bacteria, transferring resistant genes

Tetracyclines

Bind to the 30S ribosomal subunit blocking attachment of tRNA molecules preventing the synthesis of proteins.

Which component of a bacterial has a dual role of protection as well as helping to stick to various surfaces?

Cell wall

Which antibiotic would be the most effective treatment for an infection with the B. cereus? Explain your response.

Chloramphenicol because it had the best results in inhibiting bacterial growth at both the 24 and 48 hour points by observing the zone of inhibition.

Sulfonamids (Sulfa)

Competitively inhibit PABA molecule preventing the formation of folic acid essential for bacterial metabolism.

Propose reasons why an antibiotic may not be as effective at inhibiting E. coli as it is against B. cereus.

Different bacterias have different properties and have been exposed to different antibiotics over time, this means that different bacteria have varying levels of antibiotic resistance in comparison to others.

True or False: Gram positive bacteria have 3 membranes and gram negative bacteria have 2 membranes.

False

True or False: Neisseria meningitidis is a gram positive bacteria.

False

Which component of a bacterial cell assists the cell in movement?

Flagella

Which bacteria has endotoxins?

Gram negative

What is the difference between gram positive and gram negative bacteria?

Gram positive have a thick layer of peptidoglycan and appears purple when stained while gram negative has a thin layer of peptidoglycan and appears red when stained

Fluoroquinolones

Inhibit topoisomerase enzymes which function to maintain the supercoiling of chromosomal DNA preventing essential cellular processes.

B-lactam (penicillin)

Inhibits enzymes involved in cell wall synthesis, thus preventing the components of the cell wall from joining together.

What are the three mechanisms of antibiotic resistance?

Mutation, destruction or inactivation, and efflux

Classify each of the tested antibiotics as limited spectrum or broad spectrum. Explain your responses.

Penicillin, Streptomycin, Tetracycline, and Gentamicin are all broad-spectrum antibiotics because they have similar effects on B-cereus and E. coli and they can be used for patients with either one of the infections or both of them. Ampicillin and Chloramphenicol are both limited-spectrum antibiotics because they are extremely effective on one type of bacteria, but not particularly on the other.

Which component of the bacterial cell contains DNA that is ring-shaped?

Plasmid

Antibiotic Resistance

Resistance to one or more antibiotics, usually due to additional genetic information

How did we create a superbug in 1.2.3?

Strain 2 plasmid DNA transferred through conjugation to strain 1, strain 1 already had chromosomal DNA

Nucleoid

The DNA-containing area of a bacterial cell

Why is the clear area surrounding an antibiotic disk called the zone of inhibition?

The clear area is called the zone of inhibition because the antibiotic inhibits bacterial growth, so bacterial colonies are unable to grow in this 'zone'. Due to the antimicrobial effect of bacteria, there is no visible presence of bacteria in the inhibition zone.

Transformation

The genetic modification of a bacterium by incorporation of free DNA from another ruptured bacterial cell

Conjugation

The one-way transfer of DNA between bacteria in cellular contact

Endotoxins are found in

The outer membrane of gram negative bacteria.

Transduction

The transfer of genetic material from one organism (such as a bacterium) to another by a genetic vector

Which method of gene transfer involves the use of a bacteriaphage to transfer genes between two bacteria?

Transduction

Which method of gene transfer involves the bursting of a cell and the uptake of "Naked" DNA by another bacterial cell?

Transformation

True or False: Gram positive bacteria have a thicker cell wall composed of peptidoglycan when compared to gram negative bacteria.

True

Which antibiotic would be the most effective treatment for a person with an infection with both B. cereus and E. coli? Explain your response.

While Ampicillin was the most effective at treating E. coli, it wasn't the only antibiotic that was effective to the same degree (it just worked faster). In treating both E. Coli and B. Cereus it would be best to use Chloramphenicol because it had the largest zones of inhibition on both bacteria cultures at the 48 hour mark (same as Ampicillin at 48 hours, Ampicillin would be used for ONLY E.coli treatment due to faster results, but with both it would be best to use Chloramphenicol).

Which antibiotic would be the most effective treatment for an infection with the E. coli? Explain your response.

While both Chloramphenicol and Streptomycin showed similar results to the Ampicillin at the 48 hour mark, the Ampicillin would be more effective because it showed the best results at inhibiting bacterial growth at the 24 and 48 hour marks by observing the zone of inhibition, meaning it would be effective earlier in treatment.

Which of the following is the effectiveness of an antibiotic NOT dependent upon? a. The number of ribosomes in the bacteria. b. The mechanism of action of the drug. c. The structure of the bacteria.

a. The number of ribosomes in the bacteria.

What is transformation?

cells die and release "naked" DNA into the environment containing resistant genes, this DNA is scavenged by other cells for use

Which method of gene transfer involves the transfer of a plasmid via a sexual pilus between two neighboring bacteria?

conjugation

What are the three mechanisms of gene transfer?

conjugation, transformation, transduction

When do mutations occur?

during DNA replication, the enzymes encoded no longer allow antimicrobials to bind and stop DNA replication

Pili

hollow structures made of protein that allow bacteria to attach to other cells, sex plus allows transfer of plasmid DNA

Capsule

layer of polysaccharides around the cell wall that protects the cell and serves as a barrier against phagocytosis and white blood cells

Cell wall

layer outside the cell membrane that serves for protection and sometimes communication between cells

Endotoxin

lipopolysaccharides found on outer membrane of gram negative bacteria, release when bacteria ruptures

Plasma Membrane

made up of phospholipid bilayer. protects cell by regulating passage of substance into and out of the cell

What is bacterial efflux?

mechanism that causes resistance, efflux pump actively transports antimicrobial out of bacterial cell

Flagella

mobility; long appendages which rotate by a motor in cell envelope. Allow cell movement, can be any number

What is conjugation?

plasmid releases resistant genes that are transferred between two bacterial cells via the pilus

Ribosomes

protein synthesis takes place here. mRNA is read by the ribosome and Amino Acids are assembled into a protein chain