Module 9 14 Penicillin Part 1 Flashcards
1
Q
Question
A
Answer
2
Q
What makes penicillins highly regarded as antibiotics?
A
They are effective against a wide range of bacteria with low direct toxicity.
3
Q
What antibiotic family do penicillins belong to, and what are some other members of this family?
A
They belong to the β-lactam antibiotic family, which includes cephalosporins, carbapenems, and aztreonam.
4
Q
What is the common mechanism of action among all β-lactam antibiotics?
A
Disruption of the bacterial cell wall.
5
Q
Why do bacterial cells have a cell wall?
A
Bacterial cells have a cell wall to prevent them from taking up excessive water, swelling, and bursting due to the high osmotic pressure inside.
6
Q
How do penicillins affect the bacterial cell wall?
A
Penicillins weaken the cell wall, making it more porous, which causes the bacterial cell to take up excessive water and eventually rupture.
7
Q
Are penicillins bactericidal or bacteriostatic?
A
Penicillins are generally bactericidal, meaning they kill bacteria.
8
Q
What is the role of transpeptidases in bacterial cells?
A
Transpeptidases are enzymes that help form cross-bridges between peptidoglycan strands in the bacterial cell wall, providing structural strength.
9
Q
What are autolysins, and what is their function in bacterial cells?
A
Autolysins are bacterial enzymes that break down segments of the cell wall to allow for bacterial growth and division.
10
Q
How do penicillins affect the cell wall of bacteria?
A
Penicillins inhibit transpeptidases and activate autolysins, disrupting cell wall synthesis and promoting its destruction, leading to bacterial cell lysis and death.
11
Q
Are penicillins effective against all bacteria?
A
No, penicillins are effective only against actively growing and dividing bacteria.
12
Q
What are penicillin-binding proteins (PBPs) in bacterial cells?
A
PBPs are the molecular targets of penicillins, including transpeptidases, autolysins, and other enzymes that penicillins must bind to for their antibacterial effects.
13
Q
Why do penicillins have virtually no direct effects on host mammalian cells?
A
Penicillins target bacterial enzymes involved in cell wall integrity, and host mammalian cells lack a cell wall.
14
Q
What is the primary target of penicillins in bacteria?
A
Penicillins primarily target the bacterial cell wall.
15
Q
How would you describe the safety profile of penicillins?
A
Penicillins are among the safest antibiotics due to their selectivity for bacterial cell walls and their lack of impact on host mammalian cells.
16
Q
Where are PBPs located in bacterial cells?
A
PBPs are situated on the outer surface of the bacterial cytoplasmic membrane.
17
Q
How many different PBPs have been identified in bacterial cells?
A
Over eight different PBPs have been identified.
18
Q
Which PBPs are most critical for the antibacterial effects of penicillins?
A
PBP1 and PBP3 are the most crucial PBPs for the antibacterial effects of penicillins.
19
Q
When do bacteria express PBPs, and when do penicillins work most effectively?
A
Bacteria express PBPs during their growth and division phases, and penicillins work most effectively when bacteria are actively growing.
20
Q
How can bacteria become resistant to penicillins?
A
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.
21
Q
What does it mean when penicillins can’t reach their targets (PBPs)?
A
It’s like missing the bullseye. Bacterial resistance happens when penicillins can’t effectively reach their targets, the penicillin-binding proteins (PBPs).
22
Q
How do bacterial enzymes contribute to penicillin resistance?
A
Bacteria can produce enzymes that break down penicillins, rendering the drugs ineffective. It’s as if these bacterial enzymes destroy the penicillins.
23
Q
What does it mean when PBPs have low affinity for penicillins?
A
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.
24
Q
What is the structure of the cell envelope in gram-positive bacteria?
A
The cell envelope in gram-positive bacteria consists of two layers: the cytoplasmic membrane and a thick cell wall.
25
How easily can penicillins penetrate the cell wall of gram-positive bacteria?
Penicillins can readily penetrate the thick cell wall of gram-positive bacteria.
26
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.
27
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.
28
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.
29
Why is it challenging for penicillins to act on gram-negative bacteria?
Penicillins face difficulty in penetrating the outer membrane of gram-negative bacteria.
30
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.
31
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.
32
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.
33
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.
34
What is the specific name for β-lactamases that target penicillins?
β-Lactamases that selectively act on penicillins are known as penicillinases.
35
How do gram-positive bacteria handle penicillinases?
Gram-positive bacteria produce large amounts of penicillinases and release them into the surrounding environment.
36
How do gram-negative bacteria handle penicillinases?
Gram-negative bacteria produce smaller quantities of penicillinases and secrete them into the periplasmic space.
37
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).
38
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.
39
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.
40
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.
41
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.
42
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.
43
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.
44
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.
45
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.
46
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.
47
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.
48
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
49
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.
50
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.
51
Where were MRSA strains initially found, and where can they be found today?
Initially, MRSA strains were limited to healthcare facilities, but they are now also found in the community.
52
How is Healthcare-associated Methicillin-resistant Staphylococcus aureus (HCA-MRSA) usually transmitted?
HCA-MRSA is typically transmitted through person-to-person contact, often between healthcare workers and patients.
53
What are some common risk factors for acquiring HCA-MRSA?
Common risk factors for acquiring HCA-MRSA include advanced age, recent surgery or hospitalization, dialysis treatment, stays in intensive care units, prolonged antibiotic therapy, having an indwelling catheter, and residing in a long-term care facility.
54
What guidelines are used to determine the treatment of Healthcare-associated Methicillin-resistant Staphylococcus aureus (HCA-MRSA) infections?
The Clinical Practice Guidelines by the Infectious Diseases Society of America are used to guide the treatment of HCA-MRSA infections.
55
What factors influence the selection of drugs for HCA-MRSA treatment?
Drug selection is based on factors such as the site of infection, patient age, and pathogen drug sensitivity.
56
What are the preferred drugs for complicated skin and soft tissue infections in adults with HCA-MRSA?
Preferred drugs for complicated skin and soft tissue infections in adults include IV vancomycin, linezolid, daptomycin, telavancin, clindamycin, and ceftaroline.
57
Which drug is preferred for children with complicated skin and soft tissue infections caused by HCA-MRSA?
IV vancomycin is the preferred drug for children with these infections.
58
What are the preferred drugs for bacteremia or endocarditis in both adults and children with HCA-MRSA infections?
For bacteremia or endocarditis in both adults and children, the preferred drugs are IV vancomycin and daptomycin.
59
What are the preferred drugs for pneumonia in adults and children with HCA-MRSA infections?
Preferred drugs for pneumonia in adults and children include IV vancomycin, linezolid, and clindamycin.
60
Why are many antibiotics ineffective against most strains of MRSA, including tetracyclines, clindamycin, trimethoprim/sulfamethoxazole, and β-lactam agents?
Most strains of MRSA are multidrug resistant, which renders many antibiotics ineffective against them. An exception is ceftaroline.
61
When was Community-associated Methicillin-resistant Staphylococcus aureus (CA-MRSA) first reported?
CA-MRSA was first reported in 1981.
62
How are CA-MRSA and Healthcare-associated MRSA (HCA-MRSA) genetically distinct?
CA-MRSA and HCA-MRSA are genetically distinct, with unique genetic characteristics.
63
What is a notable genetic feature of many CA-MRSA strains?
Many CA-MRSA strains carry the gene for Panton-Valentine leukocidin, which produces a cytotoxin causing tissue necrosis.
64
What is the difference between CA-MRSA and HCA-MRSA regarding the presence of the Panton-Valentine leukocidin gene?
CA-MRSA strains often carry the Panton-Valentine leukocidin gene, while HCA-MRSA strains typically lack this gene.
65
How many people in the population are asymptomatic carriers of CA-MRSA?
Approximately 20% to 30% of the population are asymptomatic carriers of CA-MRSA.
66
Where are CA-MRSA carriers typically colonized by these bacteria?
CA-MRSA carriers are typically colonized by these bacteria on the skin and in the nostrils.
67
How does the danger of infection with CA-MRSA compare to Healthcare-associated MRSA (HCA-MRSA) and methicillin-sensitive S. aureus?
CA-MRSA infections are generally less dangerous than HCA-MRSA but more dangerous than those caused by methicillin-sensitive S. aureus.
68
What types of infections are typically caused by CA-MRSA?
CA-MRSA typically causes mild infections of the skin and soft tissues, such as boils and impetigo.
69
Can CA-MRSA cause more serious infections, and what are some examples of these severe infections?
Yes, CA-MRSA can lead to more severe infections, including necrotizing fasciitis, severe necrotizing pneumonia, and severe sepsis.
70
Are these severe CA-MRSA infections common?
No, these invasive infections are relatively rare.
71
What types of infections are currently common, and what percentage of S. aureus isolates do CA-MRSA account for in these cases?
Infections of the skin and soft tissues are currently common, with CA-MRSA accounting for more than 50% of S. aureus isolates from these sites.
72
How is Community-associated Methicillin-resistant Staphylococcus aureus (CA-MRSA) primarily transmitted?
CA-MRSA is primarily transmitted through skin-to-skin contact and contact with contaminated objects, such as surfaces, sports equipment, and personal items.
73
What is the typical demographic affected by CA-MRSA infections in terms of age and health status?
CA-MRSA infections typically affect young, healthy individuals who have not recently been exposed to healthcare facilities.
74
Who are some of the at-risk individuals for CA-MRSA infections?
At-risk individuals for CA-MRSA infections include athletes in contact sports (e.g., wrestling), men who have sex with men, people living in close quarters (such as family members), child care clients, prison inmates, military personnel, and college students.
75
What are some preventive measures to reduce the risk of Community-associated Methicillin-resistant Staphylococcus aureus (CA-MRSA) transmission?
Preventive measures include good hand hygiene (handwashing or using sanitizers), showering after contact sports, cleaning frequently touched surfaces, covering infected sites, and avoiding sharing towels and personal items.
76
How is the treatment for CA-MRSA determined?
Treatment for CA-MRSA depends on the severity of the infection.
77
What treatment is recommended for mild CA-MRSA infections like boils and small abscesses?
For mild infections, such as boils and small abscesses, surgical drainage may be sufficient.
78
What are the preferred antibiotics for CA-MRSA infections?
Preferred antibiotics for CA-MRSA infections include trimethoprim/sulfamethoxazole, minocycline, doxycycline, and clindamycin.
79
When should alternative antibiotics like vancomycin, daptomycin, and linezolid be considered for CA-MRSA infections?
Alternative antibiotics like vancomycin, daptomycin, and linezolid should be reserved for severe infections or when preferred agents fail to work.
80
How can the carrier state of CA-MRSA be eliminated?
The carrier state of CA-MRSA can be eliminated through intranasal application of topical antibiotics such as mupirocin or retapamulin.
81
Are β-lactam antibiotics effective against CA-MRSA, and if not, what is an exception?
β-lactam antibiotics are generally not effective against CA-MRSA. An exception is ceftaroline, a fifth-generation cephalosporin.
82
What is the common core structure shared by all penicillins?
All penicillins are derived from a common nucleus known as 6-aminopenicillanic acid.
83
What is the essential component in the core structure of penicillins for their antibacterial actions?
The β-lactam ring in the core structure of penicillins is essential for their antibacterial actions.
84
What determines the individual properties of different penicillins?
The properties of different penicillins are determined by modifications made to the common core structure.
85
How do modifications to the core structure influence the properties of penicillins?
Modifications to the core structure of penicillins impact various aspects, including their affinity for penicillin-binding proteins (PBPs), resistance to penicillinases, ability to penetrate the cell envelope of gram-negative bacteria, resistance to stomach acid, and pharmacokinetic properties, encompassing how the drug is absorbed, distributed, metabolized, and eliminated in the body.
86
How are penicillins classified based on their antimicrobial spectrum?
Penicillins are classified into four major groups based on their antimicrobial spectrum.
87
What are the four major groups of penicillins based on their antimicrobial spectrum?
The four groups of penicillins include narrow-spectrum penicillins that are sensitive to penicillinase, narrow-spectrum penicillins resistant to penicillinase (known as antistaphylococcal penicillins), broad-spectrum penicillins (often referred to as aminopenicillins), and extended-spectrum penicillins (sometimes called antipseudomonal penicillins).
88
What does the classification of penicillins into these groups depend on?
The classification is based on the range of bacteria each group is effective against.
89
What are narrow-spectrum penicillins that are penicillinase sensitive, and what bacteria are they effective against?
Narrow-spectrum penicillins that are penicillinase sensitive include Penicillin G and Penicillin V. They are effective against Streptococcus and Neisseria species, many anaerobes, spirochetes, and other bacteria.
90
What are narrow-spectrum penicillins that are penicillinase resistant, and what is their primary target?
Narrow-spectrum penicillins that are penicillinase resistant are Nafcillin, Oxacillin, and Dicloxacillin. They primarily target Staphylococcus aureus.
91
What are broad-spectrum penicillins, and which bacteria are they effective against?
Broad-spectrum penicillins include Ampicillin and Amoxicillin. They are effective against Haemophilus influenzae, Escherichia coli, Proteus mirabilis, enterococci, and Neisseria gonorrhoeae.
92
What is an extended-spectrum penicillin, and what range of bacteria does it cover?
The extended-spectrum penicillin is Piperacillin. It covers the same bacteria as broad-spectrum penicillins and also includes Pseudomonas aeruginosa, Enterobacter species, Proteus (indole positive), Bacteroides fragilis, and many Klebsiella species.
93
What is the significance of Penicillin G (benzylpenicillin) in the penicillin family?
Penicillin G is the first and prototype member of the penicillin family.
94
What is another common name for Penicillin G?
Another common name for Penicillin G is simply "penicillin."
95
How does Penicillin G work against bacteria?
Penicillin G has bactericidal effects, meaning it kills bacteria.
96
Which types of bacteria are affected by Penicillin G's bactericidal action?
Penicillin G is effective against various gram-positive bacteria and some gram-negative bacteria.
97
Is Penicillin G still used today, despite the availability of newer antibiotics?
Yes, Penicillin G remains a preferred choice for treating many infections, even with the development of newer antibiotics.
98
Which type of bacteria are effectively targeted by Penicillin G?
Penicillin G is effective against most gram-positive bacteria, except for penicillinase-producing staphylococci.
99
What are penicillinase-producing staphylococci?
Penicillinase-producing staphylococci are strains of Staphylococcus aureus that can produce penicillinase, an enzyme that can inactivate penicillin.
100
Which gram-negative cocci are susceptible to Penicillin G?
Penicillin G is effective against gram-negative cocci, including Neisseria meningitidis and non-penicillinase-producing strains of Neisseria gonorrhoeae.
101
What types of bacteria like anaerobic bacteria and spirochetes are sensitive to Penicillin G?
Penicillin G is active against anaerobic bacteria and spirochetes, including the bacterium Treponema pallidum, which causes syphilis.
102
Are most gram-negative bacilli responsive to Penicillin G?
No, most gram-negative bacilli are resistant to Penicillin G.
103
How does Penicillin G's spectrum of activity compare to other penicillins?
Penicillin G is considered a narrow-spectrum antibiotic compared to other members of the penicillin family.
104
How many different salt forms of Penicillin G are available?
Penicillin G is available in four different salt forms.
105
What are the four different salt forms of Penicillin G?
The four salt forms of penicillin G are potassium penicillin G, procaine penicillin G, benzathine penicillin G, and sodium penicillin G.
106
In what ways do these salt forms of Penicillin G differ from each other?
These salt forms vary in terms of their route of administration and the duration of their action.
107
What is the common feature among all these salt forms of Penicillin G?
Regardless of the form, each salt dissociates to release penicillin G, which is the active component responsible for the antibiotic's effect.
108
How can all forms of penicillin be administered?
All forms of penicillin can be administered intramuscularly (IM).
109
What is the key difference in the absorption rates of different penicillin salts?
The absorption rates of different penicillin salts vary significantly.
110
Which penicillin salts are absorbed rapidly, and when do their blood levels peak after IM injection?
Potassium and sodium penicillin G are absorbed rapidly, and their blood levels peak approximately 15 minutes after injection.
111
How are procaine and benzathine penicillin salts characterized in terms of absorption?
Procaine and benzathine penicillin salts are absorbed slowly and are considered repository preparations.
112
For what purpose is benzathine penicillin particularly useful due to its slow absorption?
Benzathine penicillin is useful against highly sensitive organisms, such as Treponema pallidum, the bacterium that causes syphilis, as it leads to prolonged, low-level absorption.
113
Does penicillin distribute well throughout the body's tissues and fluids?
Yes, penicillin effectively distributes to most tissues and body fluids.
114
In the absence of inflammation, is penicillin's penetration into certain areas effective, or is it limited?
In the absence of inflammation, penicillin's penetration into certain areas is limited.
115
Which areas exhibit limited penetration by penicillin in the absence of inflammation?
These areas include the meninges (protective membranes around the brain and spinal cord), joint fluids, and the fluids of the eyes.
116
How does the presence of inflammation affect the entry of penicillin into these areas?
In the presence of inflammation, the entry of penicillin into the meninges, joint fluids, and the eyes is enhanced.
117
Why is enhanced penetration of penicillin into these areas significant?
Enhanced penetration allows for the treatment of infections caused by susceptible organisms in these specific locations.
118
How does penicillin undergo elimination from the body?
Penicillin is primarily eliminated by the kidneys.
119
What are the two main mechanisms by which penicillin is eliminated by the kidneys?
Penicillin is eliminated through active tubular secretion (90%) and glomerular filtration (10%).
120
What is the typical half-life of penicillin in older children and adults?
In older children and adults, the half-life of penicillin is very short, approximately 30 minutes.
121
How does renal impairment affect the half-life of penicillin?
Renal impairment can dramatically prolong the half-life of penicillin.
122
In cases where the half-life of penicillin is significantly prolonged, what may be required?
Prolonged half-life may necessitate a reduction in the dosage of penicillin.
123
Who are considered high-risk patients for penicillin toxicity, and what should be done for them?
High-risk patients for penicillin toxicity include those with renal impairment, the acutely ill, the very young, and older adults. Kidney function should be monitored in these individuals.
124
Is penicillin G considered one of the safest antibiotics and medications?
Yes, penicillin G is considered one of the least toxic antibiotics and among the safest medications.
125
What is the primary concern associated with penicillin use?
Allergic reactions, particularly penicillin allergies, are the primary concern with penicillin use.
126
Besides allergic reactions, what are some other potential reactions to penicillin?
Other potential reactions include pain at the site of intramuscular (IM) injections, reversible sensory and motor dysfunction from accidental injection into a peripheral nerve, and neurotoxicity leading to seizures, confusion, and hallucinations when blood levels of penicillin are too high.
