2 - Antimicrobials I Flashcards
Technically speaking, what’s the difference between an antibiotic and an antimicrobial?
An Antibiotic technically has to be a chemical produced by a microbe that has the ability to harm other microbes
Antibiotics like sulfonamides, which are produced in a lab and are not made by other organisms, are antimicrobials but not technically antibiotics
What differences between mammalian and bacterial cells make selective toxicity possible?
- Bacteria are encased in a rigid cell wall, and the osmotic pressure within the bacterium is extremely high. Since mammalian cells don’t have cell walls, we can give drugs that effect cell walls without worrying about host effects
- Mammals obtain folic acid from nutrition, but bacterial cells have to synthesize folic acid for themselves. Sulfonamides block the conversion of PABA into folic acid, which kills microbes but doesn’t effect mammalian cells
- Bacterial cells and mammalian cells have very different ribosomes. We can impair bacterial ribosomes without effecting mammalian ones
For most drugs, where is the site of action?
Why is this important?
Intracellular
Microbes can develop resistance by controlling what comes in and out of the membrane. They can cease active uptake of certain drugs, and increase active export of others, reducing the effectiveness of the drug
Which bacterial gene codes for almost complete resist to almost all bacteria?
New Delhi metallo-beta-lactamase 1 (NDM-1)
pg. 654
There’s only two ways that bacteria can develop resistance:
by mutating spontaneously
by conjugating (transferring extrachromosomal DNA from one bacteria to another)
What is an R-Factor?
The elements needed for conjugation
In order to transfer resistance by conjugation, the donor organism has to have two unique DNA segments:
- The codes for mechanisms of drug resistance
- the codes for the sexual apparatus required for DNA factor
The two DNA segments make up the R-Factor
Conjugation takes place primarily among ______ bacteria
Gram negative
Is conjugation species specific?
NO!
Pathogenic bacteria can inherit R factors from other pathogens or even the normal flora of the body
Which mechanism for resistance usually causes multiple drug resistance?
Conjugation
In a single event, a drug-sensitive bacterium can become highly drug resistant
How do different species of microbes in the body keep each other in check?
- They secrete compounds that are toxic to other microbes
- They compete with each other for available nutrients
Which antibiotics promote resistance
ALL OF THEM
BUT broad spectrums facilitate emergence the most
Resistance is created by killing, so the more bacteria a drug kills, the more likely it is to create resistance
Obviously antibiotics promote emergence of resistant pathogens. But what else do they promote?
Resistant normal flora
this is a big problem because they flora can conjugate with pathogens and create resistant pathogens
What is a superinfection?
Give an example
a NEW infection that appears during the course of treatment for a different infection
Getting a yeast infection after taking a drug for a UTI
Hospital acquired pneumonias are usually caused by which three pathogens?
Pseudomonas species
Klebsiella species
Staph Aureus
What is a PCR?
Polymerase Chain Reaction
An enzyme is used to generate thousands of copies of DNA/RNA unique to the infecting microbe, creating enough material for detection
MORE SPECIFIC AND MORE SENSITIVE THAN GRAM STAINING
To be effective, an antibiotic must be present at the site of infection in a concentration greater than:
the minimal inhibitory concentration (MIC)
Why do bacteria flourish on foreign hardware?
Phagocytes are too busy attacking the organism to attack the bacteria, allowing microbes to flourish
There is one disease in which the use of multiple drugs actually prevents resistance:
TB
As a rule, postop antibiotics are _______
unnecessary
Where are PBPs located?
