Antibacterial Drug Therapy & Beta Lactams Flashcards
How do you detect type of bacteria?
Gram stain
Gram stain cells turned purple are:
Gram positive
Gram stain cells turned colourless are:
Gram negative
Gram positive bacteria layers consist of:
A thick murein layer and cytoplasmic membrane
Definition of minimum inhibitory concentration:
Lowest concentration of an antibacterial drug that inhibits visible growth
Definition of minimum bactericidal concentration:
Lowest concentration of antibacterial agent that is required to kill a particular bacterium
How is MBC calculated?
- Taking dilutions of the MIC and sub-culturing them into antibacterial-free media
- After a set amount of time, tubes are assessed for bacterial growth
- Tube showing no bacterial growth at the lowest drug concentration indicates the MBC
Bacteria growing close to drug on Kirby-Bauer test indicates:
Drug resistance
Bacteria not growing in a wide circumference around the drug on Kirby-Bauer test indicates:
Sensitivity to drug
Steps for selecting & administering antimicrobial drugs:
- Identify the organism
- Initiate treatment immediately
- Select a drug
- Determine dosage
- Discuss drug safety
When are bactericidal drugs prioritized over bacteriostatic?
When the immune system is compromised, or the infection is life-threatening
Diseases requiring special consideration:
- Osteomyelitis
- Foreign bodies
- Abscesses
- Intracellular pathogens
- Immunodeficiencies
Definition of prophylactic use of a microbial drug:
Use of pharmacological agents for prevention as opposed to curing or treating a disease
When is prophylactic treatment recommended?
- In situations where there is a high risk of serious infection following trauma such as meningitis
- When a patient’s condition predisposes them to serious infection, such as recurring UTIs
- Surgical situations
Commonly prescribed beta-lactams:
Penicillin and cephalosporins
MOA of beta-lactams:
Inhibition of cell wall synthesis
How do beta-lactams inhibit cell wall synthesis?
Inactivating bacterial transpeptidase which results in a defective cell wall, and ultimately cell lysis
Penicillin G spectrum of activity:
Narrow spectrum of activity (Gram pos bacteria, some anaerobes)
Highly effective
What is penicillin G used to treat?
Serious infections w gram pos bacteria, as well as some anaerobes
Method of administration of pen G:
Injected due to unstable in acidic conditions
Method of administration of Pen V:
Taken orally
Penicillins designed to be resistant to penicillinase:
Dicloxacillin, oxacillin, cloxacillin
Amoxicillin spectrum of activity:
Targets gram pos aerobes, anaerobes, and several gram neg pathogens
Oral bioavailability of amoxicillin:
80%, highest of the penicillins
Amoxicillin is more effective when taken in combination with:
Penicillinase inhibitors, such as clavulanic acid
Penicillin adverse effects:
hypersensitivity reactions, non-allergic skin rashes
Main difference between cephalosporins and penicillins:
Cephalosporins are not susceptible to penicillinases
Cephalosporin spectrum of activity:
Dependent on what generation
Cephalexin is an example of:
First generation cephalosporin
What are first gen cephalosporins used to treat?
Gram pos aerobes, anaerobes, and some medically important gram neg aerobes such as e. coli
Cefuroxime is an example of:
Second generation cephalosporin
What are second gen cephalosporins used to treat?
Anaerobes, many gram neg bacteria
Cefotaxime is an example of :
Third gen cephalosporin
MOA of third gen cephalosporins:
Readily cross BBB
What are third gen cephalosporins used to treat?
Gram neg aerobes
What are fourth gen cephalosporins used to treat?
reserved for life-threatening infections
- Rapidly penetrate gram neg bacteria
- Active against beta-lactamase producing bacteria
