Antimicrobial Chemotherapy and Unit 1 and 2, add to combined set when done. Need 3

What are Koch’s postulates?

Koch’s postulates state that a pathogen must be present in diseased individuals, isolated and grown in pure culture, cause disease in a healthy host, and be re-isolated.

What are the limitations of Koch’s postulates?

Some microbes cannot be cultured, some diseases are caused by multiple pathogens, and ethical concerns prevent testing in humans.

How are Koch’s postulates applied to infectious diseases?

They are used to establish a causal relationship between a specific microorganism and a disease.

What is a sporadic disease?

A sporadic disease occurs occasionally.

What is an endemic disease?

An endemic disease is constantly present in a population.

What is an epidemic?

An epidemic is a sudden increase in the number of cases of a disease in a specific area or population a

What is a pandemic?

A pandemic is a worldwide spread of disease.

What are the three main mechanisms of horizontal gene transfer in bacteria?

The three mechanisms are transformation, transduction, and conjugation.

What is transformation?

Transformation is the uptake of free DNA from the environment by a bacterial cell.

What is transduction?

Transduction is the transfer of bacterial DNA from one cell to another via a bacteriophage (virus).

What is conjugation?

Conjugation is the transfer of DNA between bacteria through direct cell-to-cell contact using a sex pilus.

What virulence factors help bacteria bind to body tissues?

Bacteria use adhesins, pili (fimbriae), and surface proteins to attach to host tissues.

What are the differences between exotoxins and endotoxins?

Exotoxins are proteins secreted by bacteria that are highly specific and toxic, while endotoxins are lipopolysaccharides from Gram-negative bacteria that are released upon cell death and cause generalized inflammation.

What is the structure of a Gram-positive (G⁺) cell wall?

Gram-positive cell walls have a thick peptidoglycan layer and contain teichoic acids, but no outer membrane.

What is the structure of a Gram-negative (G⁻) cell wall?

Gram-negative cell walls have a thin peptidoglycan layer and an outer membrane containing lipopolysaccharide (LPS).

What is the key difference between G⁺ and G⁻ cell walls?

G⁺ cells have thick peptidoglycan and no outer membrane, while G⁻ cells have thin peptidoglycan and an outer membrane.

What is the main component of the bacterial cell wall?

The main component is peptidoglycan.

What is peptidoglycan made of?

Peptidoglycan consists of alternating NAG (N-acetylglucosamine) and NAM (N-acetylmuramic acid) sugars.

How is peptidoglycan cross-linked?

Peptide chains attached to NAM are cross-linked between adjacent strands, forming a strong mesh-like structure.

What is the bacterial outer membrane made of?

The outer membrane is made of phospholipids, proteins, and lipopolysaccharide (LPS).

What are the important components of the outer membrane?

Key components include LPS, porins (proteins), and phospholipids.

Do both Gram-positive and Gram-negative cells have an outer membrane?

No, only Gram-negative cells have an outer membrane.

Which component of the Gram-negative cell is called the endotoxin and what is its significance?

The lipid A portion of LPS is the endotoxin, and it triggers strong immune responses such as fever and inflammation.

What are the phases of the bacterial growth curve?

Lag phase, log (exponential) phase, stationary phase, and death phase.

What happens in the lag phase?

Cells are metabolically active but not dividing.

What happens in the log (exponential) phase?

Cells divide rapidly at a constant rate.

What happens in the stationary phase?

Cell growth equals cell death due to limited nutrients.

What happens in the death phase?

Cells die at a faster rate than they are produced.

What are the five groups of bacteria based on oxygen requirements?

Obligate aerobes, obligate anaerobes, facultative anaerobes, microaerophiles, and aerotolerant anaerobes.

What are obligate aerobes?

They require oxygen to grow.

What are obligate anaerobes?

They cannot survive in the presence of oxygen.

What are facultative anaerobes?

They can grow with or without oxygen but prefer oxygen.

What are microaerophiles?

They require low levels of oxygen.

What are aerotolerant anaerobes?

They do not use oxygen but can tolerate its presence.

What is chemotherapy?

Chemotherapy is the use of chemicals to treat a disease.

What is an antibiotic?

An antibiotic is a substance produced by a microbe that, in small amounts, inhibits another microbe.

What are antimicrobial drugs?

Antimicrobial drugs are synthetic substances that interfere with the growth of microbes.

What is selective toxicity?

Selective toxicity is the ability to destroy pathogens while causing minimal harm to the host.

What is therapeutic index?

The therapeutic index is the ratio of the lowest dose toxic to the patient to the dose used for therapy and indicates drug safety.

What are the characteristics of antimicrobial medications?

Antimicrobial drugs exhibit selective toxicity, can be bacteriostatic or bactericidal, and their toxicity is measured by the therapeutic index.

What is the spectrum of activity?

The spectrum of activity is the range of microorganisms that an antimicrobial drug is effective against.

What are the advantages and disadvantages of broad and narrow spectrum antibiotics?

Broad-spectrum antibiotics act against a wide range of microorganisms, including Gram-negative bacteria, but misuse can promote resistance. Narrow-spectrum antibiotics target specific organisms.

What are semi-synthetic and extended spectrum antibiotics?

Semi-synthetic antibiotics are chemically modified to improve effectiveness or resistance to penicillinase. Extended-spectrum antibiotics are modified to act against additional bacteria. Examples include amoxicillin with clavulanic acid and ceftriaxone.

What is superinfection?

Superinfection occurs when normal microbiota are suppressed, leading to dysbiosis such as overgrowth of Clostridioides difficile.

What are some effects of antimicrobial combinations?

Antimicrobial combinations can be synergistic, additive, or antagonistic.

• Synergistic

  • The combined effect is greater than the sum of each drug alone

  • Example: penicillin + aminoglycoside against some bacteria

• Additive

  • The combined effect equals the sum of their individual effects

  • They help each other but do not greatly enhance activity

• Antagonistic

  • One drug reduces or interferes with the effect of the other

  • Example: a bacteriostatic drug may interfere with a bactericidal drug that works best on actively growing bacteria

What are some possible adverse effects of antibiotics?

Adverse effects include allergic reactions, toxic effects, and disruption of normal microbiota.

What is the difference between intrinsic and acquired resistance in bacteria?

Intrinsic resistance is natural, such as lack of a cell wall or presence of an outer membrane, while acquired resistance develops through mutations or horizontal gene transfer.

What are the different targets for antibiotics in a bacterial cell?

Targets include cell wall synthesis, protein synthesis, nucleic acid synthesis, metabolic pathways, and the cytoplasmic membrane.

What classes of antibiotics inhibit cell wall biosynthesis?

β-lactam drugs, glycopeptides such as vancomycin, and cyclic polypeptides such as bacitracin inhibit cell wall synthesis.

Why are beta lactams effective only against growing cells?

They are effective only against actively dividing cells because they interfere with cell wall synthesis during growth.

What is the mechanism of activity of beta-lactam antibiotics? How do they kill bacterial cells?

They bind to penicillin-binding proteins (PBPs) and inhibit peptidoglycan cross-linking, weakening the cell wall and causing osmotic lysis.

What are the different improvements of cell wall inhibitor antibiotics?

Improvements include resistance to penicillinase and an expanded spectrum of activity.

What are the antibiotics that inhibit cell walls of Mycobacteria? How do they function?

Isoniazid (INH) inhibits mycolic acid synthesis in Mycobacteria, while ethambutol inhibits incorporation of mycolic acid into the cell wall.

Why are some protein synthesis inhibitors harmful?

They can affect mitochondrial 70S ribosomes, which are similar to bacterial ribosomes.

What are the different mechanisms of protein synthesis inhibition?

They target the 70S ribosome (30S and 50S subunits) and interfere with translation.

What is the mechanism of inhibition of folate biosynthesis pathway?

These drugs inhibit folate metabolism, which is required for DNA synthesis.

How do some antibiotics block DNA and RNA biosynthesis?

They inhibit DNA gyrase or RNA polymerase, blocking replication or transcription.

What is antibiotic resistance?

Antibiotic resistance is the ability of bacteria to survive antimicrobial treatment.

What are some common causes for antibiotic resistance?

Common causes include misuse of antibiotics, use against viral infections, and failure to complete treatment.

How does antibiotic resistance evolve?

It evolves through spontaneous mutations and horizontal gene transfer.

What are the major mechanisms of antibiotic resistance in bacteria?

Major mechanisms include drug inactivation, gene transfer via R plasmids, and spontaneous mutations.

What are some ways to slow the emergence and spread of antibiotic resistance?

Antibiotic stewardship, proper prescribing, patient compliance, and public education help reduce resistance.