Chapter 22: Infectious Diseases I

Question 1

Infectious diseases can be caused by the following pathogens:

Answer 1

1. Viruses
2. Bacteria
3. Protozoa
4. Fungi
5. Parasites
6. Infectious proteins (Prions)

Question 2

Infectious diseases that can be spread through contact between people is known as what?

Answer 2

Communicable or contagious

Question 3

When making a treatment decision regarding an infectious disease, what is considered?

Answer 3

1. The bug (pathogen)
2. The drug (antibiotic)
   3, The patient (host)

Question 4

What are the characteristics of an infection?

Answer 4

1. Site of infection
2. Severity of infection
3. Whether it is community acquired or hospital acquired (Hospital acquired infections usually involves multidrug resistant organisms)

Question 5

How is an infection diagnosed?

Answer 5

The main thing you look at is symptoms, not just the urine culture. You look at both.

Question 6

What are the characteristics of an antibiotic that we should consider for treatment?

Answer 6

1. Spectrum of activity

2. Ability to penetrate the site of infection

Question 7

What are patient characteristics we consider for antibiotic selection?

Answer 7

1. Age
2. Weight
3. Hepatic function
4. Renal function
5. Allergies

Question 8

What is empiric treatment?

Answer 8

Before we even identify what the microorganism is, we want to give broad spectrum antibiotic treatment. This is giving a group of antibiotics that provide a broad coverage of organisms to make sure we treat whatever it could possibly be.

Question 9

What is the gram stain?

Answer 9

When treating an infected patient, we obtain bodily fluids that contain the bacteria such as urine, lung sputum, etc… We send it to the microbiology lab to identify the strain of bacteria that the patient is infected with. The gram stain is a process that doesn’t completely identify the bacteria strain but it does give a clue as to what it could be in order to fight against it based on its characteristics. Gram positive cells have a thick cell wall and stain purple when stained with crystal violet. Gram negative cells have a thin cell wall and turn pink when stained with safranin concentration. Atypical cells do not have a cell wall and do not stain well.

Question 10

What is the Culture and Susceptibility Report?

Answer 10

This is the report that the microbiology lab gives back after they were given the bacterium source from the patient. It tells you what the bacteria is and what antibiotics it is susceptible and resistant to. With this, you have to make the decision on what is the best antibiotic to give to the patient.

Question 11

What is the minimum inhibitory concentration?

Answer 11

This is the minimum amount of the antibiotic needed to prevent growth of the bacterium. This is provided on the C&S Report.

Question 12

What is synergy?

Answer 12

Synergy is using two-antibiotics of different classes together to provide a much stronger effect upon the bacteria. Using the two together provides a much larger effect than if they were used solely. A good example is aminoglycosides and beta-lactams. Beta-lactams allow the aminoglycosides to reach and attack the bacterium’s ribosomes a lot more clearly.

Question 13

What are the Folic Acid Synthesis Inhibitors?

Answer 13

1. Sulfonamides
2. Trimethoprim
3. Dapsone

Question 14

What are the Cell Wall Inhibitors?

Answer 14

1. Beta-Lactams (Penicillins, Cephalosporins, Carbapenems)
2. Monobactams (Aztreonam)
3. Vancomycin, Dalbovancin, Oritavancin, Telavancin

Question 15

What are the DNA/RNA Synthesis Inhibitors?

Answer 15

Quinolones
Metronidazole, Tinidazole
Rifampin

Question 16

What are the Protein Synthesis Inhibitors?

Answer 16

Aminoglycosides
Macrolides
Tetracyclines
Clindamycin
Linezolid, Tedizolid
Quinupristin/Dalfopristin

Question 17

What things do we monitor when treating a patient with an antibiotic?

Answer 17

1. Fever
2. WBC trend
3. Signs and symptoms
   These 3 things can tell us how effectively they are responding to treatment

Question 18

What are reasons for lack of response to an antibiotic?

Answer 18

1. The pathogen (It could be developing resistance, be a different , stronger strain, etc…)
2. The drug (It could be at an insufficient dose strength, having a drug interaction with something else, etc…)
3. The patient (The patient could be fighting another infection, be immunocompromised, etc…)

Question 19

Organisms can develop resistance to fight back against antibiotics. What are some methods of resistance?

Answer 19

1. Intrinsic Resistance: The pathogen has a natural resistance to the antibiotic. An example would be E. Coli towards Vancomycin. Vancomycin is too big to properly tear down the walls of the E. Coli. Therefore, the E. Coli thrives
2. Susceptible Pressure. There are strains that are killed by the antibiotic but the resistant group of it will survive and thrive. An example would be enterococcus towards Vancomycin. When Vancomycin is taken, it will kill a lot of the enterrococcus that is naturally in the gut but there are groups of enterococcus resistant to the Vancomycin that will survive and thrive. This is natural selection.
3. Acquired Resistance: This is when bacteria obtain resistant genes from other bacteria or by picking them up from the environment.
4. Enzyme Inactivation: There are bacteria that contain enzymes capable of breaking down the antibiotic. There are many bacteria that contain beta-lactamases that break down beta-lactams (Penicillins, Cephalosporins, and Carbapenems). Through this, the bacteria survives. This is why beta-lactamase inhibitors are added to beta-lactams (Clavulanate, sulbactam, tazobactam).

Question 20

Common Resistant Pathogens

Answer 20

Klebsiella
Escherichia coli
Acinetobacter
Enterococcus
Staphylococcus
Pseudomonas

(Kill each and every strong pathogen)

Question 21

What is Clostroides difficile infection?

Answer 21

This is another example of natural selection. Antibiotics kill of normal GI flora along with the bacteria that they are targeting. Inactive C. dificcile are usually sitting in the gut but once the active ones are wiped out, these inactive ones activate and thrive in the gut. The symptoms can then be mild or severe.

Question 22

What needs to be considered with dose optimization?

Answer 22

We have to consider whether the antibiotic is time dependent or concentration dependent. If it is concentration dependent (Aminoglycosides, quinolones) then big doses of them should be given. If the antibiotic is time dependent (Beta-lactams) they should be given for a long period of time to keep them above the MIC.

Question 23

What are Beta-Lactams?

Answer 23

These are drugs that contain a beta-lactam ring in their molecular structure. They bind to peptidoglycan binding proteins which then prevents the formation of cell walls.

Question 24

What are penicillins?

Answer 24

These are Beta-Lactams. There are many subtypes of penicillins that cover different types of bacteria. However, for the most part, they cover gram positive bacteria. They do not cover MRSA or atypical bacteria.

Question 24

What are penicillins?

Answer 24

These are Beta-Lactams. There are many subtypes of penicillins that cover different types of bacteria. However, for the most part, they cover gram positive bacteria. They do not cover MRSA or atypical bacteria.

Question 25

What are side effects of penicillins?

Answer 25

Upset GI
Rash
Diarrhea

Question 26

What are possible drug interactions of penicillins?

Answer 26

1. Increase the concentrations of probenecid
2. Increase the effectiveness of warfarin (Except for nafcillin and dicloxacillin)
3. Increase the concentration of methotrexate and decrease tje concentration of mycophenolates

Question 27

What are cephalosporins?

Answer 27

These are another beta-lactam. There are different generations of them. With every next generation, they cover more gram negative pathogens. As a whole, they do not cover enterococcus or atypical organisms.

Question 28

What are side effects of cephalosporins?

Answer 28

Diarrhea, rash, GI upset, may cause seizures if they reach high accumulations

Question 29

What are drug interactions with cephalosporins that we should watch out for?

Answer 29

Avoid antacids and calcium containing products.

Question 30

What are carbapenems?

Answer 30

This is another beta lactam. They are usually used for multi-drug resistant organisms.

Question 31

What are side effects and drug interactions of Carbapenems?

Answer 31

They also cause nausea, vomiting, diarrhea, and rash. Avoid valproic acid and other seizure control drugs because they can decrease their concentrations and therefore, not control the seizure in the patient.

Question 32

What are monobactams?

Answer 32

This drug class is extremely similar in structure to beta-lactams. They are usually used when the patient has a beta-lactam allergy. The side effects are the same as that of beta-lactams. It has the same mechanism of action too. Monobactams have gram negative activity.

Question 33

What are aminoglycosides?

Answer 33

This class of antibiotics works by binding to ribosomes which ultimately prevents the synthesis of cell membranes. They are active against gram negative bacteria but can be used synergistically with beta-lactams and vancomycin to kill gram positive bacteria (Streptomycin and Gentamicin). These drugs are concentration dependent.

Question 34

Are aminoglycosides time-dependent or concentration-dependent?

Answer 34

They are concentration dependent. Therefore, we must dose the patient by giving them large doses with low frequencies or give them short dosages with many timing frequencies. This is done to keep the concentration above the MIC.