Module 9 14 Penicillin Part 1 Flashcards
Question
Answer
What makes penicillins highly regarded as antibiotics?
They are effective against a wide range of bacteria with low direct toxicity.
What antibiotic family do penicillins belong to, and what are some other members of this family?
They belong to the β-lactam antibiotic family, which includes cephalosporins, carbapenems, and aztreonam.
What is the common mechanism of action among all β-lactam antibiotics?
Disruption of the bacterial cell wall.
Why do bacterial cells have a cell wall?
Bacterial cells have a cell wall to prevent them from taking up excessive water, swelling, and bursting due to the high osmotic pressure inside.
How do penicillins affect the bacterial cell wall?
Penicillins weaken the cell wall, making it more porous, which causes the bacterial cell to take up excessive water and eventually rupture.
Are penicillins bactericidal or bacteriostatic?
Penicillins are generally bactericidal, meaning they kill bacteria.
What is the role of transpeptidases in bacterial cells?
Transpeptidases are enzymes that help form cross-bridges between peptidoglycan strands in the bacterial cell wall, providing structural strength.
What are autolysins, and what is their function in bacterial cells?
Autolysins are bacterial enzymes that break down segments of the cell wall to allow for bacterial growth and division.
How do penicillins affect the cell wall of bacteria?
Penicillins inhibit transpeptidases and activate autolysins, disrupting cell wall synthesis and promoting its destruction, leading to bacterial cell lysis and death.
Are penicillins effective against all bacteria?
No, penicillins are effective only against actively growing and dividing bacteria.
What are penicillin-binding proteins (PBPs) in bacterial cells?
PBPs are the molecular targets of penicillins, including transpeptidases, autolysins, and other enzymes that penicillins must bind to for their antibacterial effects.
Why do penicillins have virtually no direct effects on host mammalian cells?
Penicillins target bacterial enzymes involved in cell wall integrity, and host mammalian cells lack a cell wall.
What is the primary target of penicillins in bacteria?
Penicillins primarily target the bacterial cell wall.
How would you describe the safety profile of penicillins?
Penicillins are among the safest antibiotics due to their selectivity for bacterial cell walls and their lack of impact on host mammalian cells.
Where are PBPs located in bacterial cells?
PBPs are situated on the outer surface of the bacterial cytoplasmic membrane.
How many different PBPs have been identified in bacterial cells?
Over eight different PBPs have been identified.
Which PBPs are most critical for the antibacterial effects of penicillins?
PBP1 and PBP3 are the most crucial PBPs for the antibacterial effects of penicillins.
When do bacteria express PBPs, and when do penicillins work most effectively?
Bacteria express PBPs during their growth and division phases, and penicillins work most effectively when bacteria are actively growing.
How can bacteria become resistant to penicillins?
Bacterial resistance to penicillins can occur due to the inability of penicillins to reach their targets (PBPs), inactivation of penicillins by bacterial enzymes, or production of PBPs with low affinity for penicillins.
What does it mean when penicillins can’t reach their targets (PBPs)?
It’s like missing the bullseye. Bacterial resistance happens when penicillins can’t effectively reach their targets, the penicillin-binding proteins (PBPs).
How do bacterial enzymes contribute to penicillin resistance?
Bacteria can produce enzymes that break down penicillins, rendering the drugs ineffective. It’s as if these bacterial enzymes destroy the penicillins.
What does it mean when PBPs have low affinity for penicillins?
Bacteria can develop penicillin-binding proteins (PBPs) that don’t bind effectively to penicillins. This makes it harder for penicillins to work against these bacteria.
What is the structure of the cell envelope in gram-positive bacteria?
The cell envelope in gram-positive bacteria consists of two layers: the cytoplasmic membrane and a thick cell wall.
How easily can penicillins penetrate the cell wall of gram-positive bacteria?
Penicillins can readily penetrate the thick cell wall of gram-positive bacteria.
Are penicillins generally effective against gram-positive bacteria?
Yes, penicillins are usually highly effective against gram-positive organisms because they can easily reach their targets on the cytoplasmic membrane.
Why are penicillins less effective against gram-negative bacteria?
Penicillins have more difficulty penetrating the complex cell envelope of gram-negative bacteria, making them less effective against these organisms.
What are the three layers in the cell envelope of gram-negative bacteria?
The cell envelope in gram-negative bacteria consists of the cytoplasmic membrane, a thin cell wall, and an outer membrane.
Why is it challenging for penicillins to act on gram-negative bacteria?
Penicillins face difficulty in penetrating the outer membrane of gram-negative bacteria.
Which penicillin is capable of crossing the outer membrane of gram-negative bacteria?
Specific penicillins, such as ampicillin, can cross the outer membrane and reach their targets on the cytoplasmic membrane.
Are most penicillins effective against gram-negative bacteria?
No, many penicillins are less effective against gram-negative bacteria because they struggle to cross the outer membrane.
What are β-lactamases, and what is their role?
β-Lactamases are enzymes that break the β-lactam ring in penicillins and other β-lactam antibiotics, rendering them inactive.
What types of β-lactamases do bacteria produce?
Bacteria can produce various β-lactamases, some specific to penicillins, some specific to other β-lactam antibiotics (e.g., cephalosporins), and some that can affect multiple β-lactam antibiotics.
What is the specific name for β-lactamases that target penicillins?
β-Lactamases that selectively act on penicillins are known as penicillinases.
How do gram-positive bacteria handle penicillinases?
Gram-positive bacteria produce large amounts of penicillinases and release them into the surrounding environment.
How do gram-negative bacteria handle penicillinases?
Gram-negative bacteria produce smaller quantities of penicillinases and secrete them into the periplasmic space.
Where can genes encoding β-lactamases be found in bacteria?
Genes coding for β-lactamases can be located on bacterial chromosomes and plasmids (extrachromosomal DNA).
How can the spread of penicillin resistance be promoted in bacteria?
Genes encoding β-lactamases on plasmids can be transferred from one bacterium to another, facilitating the spread of penicillin resistance.
What happened with penicillin sensitivity in Staphylococcus aureus strains after its introduction in the 1940s?
Initially, when penicillin was introduced in the 1940s, all strains of Staphylococcus aureus were sensitive to it.
Why was the introduction of methicillin significant in combating penicillin-resistant Staphylococcus aureus?
Methicillin is a penicillin derivative that is resistant to the actions of β-lactamases, which had become a problem with penicillin-resistant strains.
Are there known strains of Staphylococcus aureus that can inactivate methicillin or related penicillinase-resistant penicillins with β-lactamases?
No, currently, there are no known strains of S. aureus that produce β-lactamases capable of inactivating methicillin or related penicillinase-resistant penicillins, although some strains may be resistant to these drugs for other reasons.
What does MRSA stand for, and what is it known for?
MRSA stands for Methicillin-resistant Staphylococcus aureus, and it is a group of bacterial strains known for their resistance to methicillin and other β-lactam antibiotics.
How do MRSA strains resist penicillins and β-lactam antibiotics?
MRSA strains have penicillin-binding proteins (PBPs) with a low affinity for penicillins and other β-lactam antibiotics.
How did MRSA develop its unique resistance mechanism?
MRSA acquired genes from other bacteria that code for low-affinity PBPs, leading to the development of this resistance mechanism.
What is Staphylococcus aureus, and where is it commonly found in healthy individuals?
Staphylococcus aureus (S. aureus) is a gram-positive bacterium often found on the skin and in the nostrils of healthy people.
What are the common types of infections caused by S. aureus?
S. aureus infections typically involve the skin and soft tissues, leading to conditions like abscesses, boils, cellulitis, and impetigo.
How has S. aureus developed antibiotic resistance over the years?
S. aureus initially became resistant to penicillins due to the production of penicillinases by bacteria.
What was introduced in 1959 to combat penicillin-resistant S. aureus strains?
In 1959, methicillin, the first penicillinase-resistant penicillin, was introduced to combat penicillin-resistant S. aureus strains
What are Methicillin-resistant Staphylococcus aureus (MRSA) strains resistant to?
MRSA strains are highly resistant, not only to methicillin (now obsolete) but also to all penicillins and most cephalosporins.
What is the basis of MRSA resistance to penicillins and cephalosporins?
MRSA resistance is based on the acquisition of genes that code for penicillin-binding proteins (PBPs) with very low affinity for penicillins and cephalosporins.
