Introduction to infections PART 2

Question 1

Define the term Cmax

Answer 1

This is the maximum concentration at which you must have your antibiotic so that it can achieve what you want it to do

Question 2

Define the term MIC (minimum inhibitory concentration)

Answer 2

This is the minimum concentration of an antibiotic required in order to produce the desired effect.

Question 3

What is a concentration dependent antibiotics?

Answer 3

You must have a peak concentration at the site of infection so that is can be effective. A high concentration in the blood is required. Concentration must be constantly above the MIC.

Post-antibiotic effect is still in play. Even if the concentration of antibiotic is below minimum inhibitory concentration there is still an antibiotic effect occurring: inhibiting microbial growth.

E.G., AMINOGLYCOSIDES

Question 4

What is a time dependent antibiotic?

Answer 4

Concentration should be maintained above the MIC between doses. Higher doses do not increase antimicrobial activity. There is no post-antibiotic effect, there is no residual antibiotic effect after concentrations of antibiotics has fallen below the MIC.

E.G., BETA LACTAMS, MACROLIDES

Question 5

What is a bacterial-static antibiotic?

Answer 5

This form of inhibitor is reversible stoppage. It arrests the bacteria.

Question 6

What is a bacteriocidal antibiotic?

Answer 6

This form of inhibitor is irreversible. It kills the actual microbe.

Question 7

What is Prophylaxis treatment? and how does that differ from normal treatment?

Answer 7

Prophylaxis is to prevent infectious complications (e.g, during surgery), or to prevent recurrent infection. Normally doses are given as STAT.

Normal treatment is to reduce the growth or reproduction of pathogens (e.g., infection or colonisation). These tend to be lower doses than prophylaxis doses, with differences in dosing regimens.

Question 8

What is empirical therapy?

Answer 8

This is the initial ‘blind’ therapy, however not blind at all because it is based in evidence.

Empiric therapy or empirical therapy is medical treatment or therapy based on experience and, more specifically, therapy begun on the basis of a clinical “educated guess” in the absence of complete or perfect information. Antibiotics can be switched after MC+S results.

Urine collection: microscopy, culture and sensitivity (MCS)

Question 9

What is drug monitoring?

Answer 9

Monitoring the response to a drug, the resolution of any signs and symptoms. We must always check renal and liver function and any patient allergies.

Question 10

What are microbiological assays?

Answer 10

These enable testing. Used to determine the potency of a drug in animals or man and monitoring and controlling anti- microbial chemotherapy.

Question 11

What is red man syndrome?

Answer 11

For Vancomycin, if it is given too fast it will cause red man syndrome. The patient will turn red because of the sensitivity.

Question 12

What are the dangers of giving amino-glycosides too fast?

Answer 12

This may cause nephro-toxicity and ototoxicity.

Nephrotoxicity is defining as rapid deterioration in the kidney function due to toxic effect of medications and chemicals.

Ototoxicity is when a person develops hearing or balance problems due to a medicine.

Question 13

What microorganisms most commonly cause urinary tract infections?

Answer 13

E.coli, Klebsiella, Proteus

Question 14

What microorganisms most commonly cause skin infections?

Answer 14

e.g., cellulitis is caused by staphylococcus, streptococcus and MRSA

MRSA is a type of bacteria that’s resistant to several widely used antibiotics. This means infections with MRSA can be harder to treat than other bacterial infections. The full name of MRSA is methicillin-resistant Staphylococcus aureus. You might have heard it called a “superbug”.

Question 15

What microorganisms most commonly cause respiratory infections?

Answer 15

URTI (An upper respiratory tract infection):
Group A & C Streptococcus, Mycoplasma, Haemophylis Influenza

LRTI (Lower Respiratory Tract Infections):
Pseudomonas, Strep pneumoniae, Legionella, Staf aureus, Haemophylis Influenza

Question 16

What microorganisms most commonly cause Gastrointestinal Infection?

Answer 16

Norvirus, C difficile, Salmonella

Question 17

Outline the key characteristics of beta-lactums, giving examples and highlighting their mechanism of action, indication and adverse effects.

Answer 17

E.g., penicillin, cephalosporin, carbapenem, monobactam

β-lactam antibiotics (beta-lactam antibiotics) are antibiotics that contain a beta-lactam ring in their chemical structure.

The mechanism of action is to inhibit the cell wall synthesis. We have beta lactamases that will inhibit the inhibitor of cell wall synthesis by attacking the beta lactum, causing resistance.

Co-amoxiclav contains amoxicillin (an antibiotic from the penicillin group of medicines) mixed with clavulanic acid. The clavulanic acid stops bacteria from breaking down amoxicillin, allowing the antibiotic to work better. This drug is often used a third or fourth line to prevent resistance from occurring.

A patient may have a penicillin allergy so they wouldn’t be able to be prescribed groups classed as beta-lactums. Most common side effects include diarrhoea and GI upset.

A patient should be converted from IV to oral formulations as soon as possible.

Question 18

Outline the key characteristics of macrolides, giving examples and highlighting their mechanism of action, indication and adverse effects.

Answer 18

E.g., Erythromycin, Azithromycin and Clarithromycin

These antibiotics work by inhibiting protein synthesis by binding to the 50s ribosomal subunit. Most common adverse effect is diarrhoea.

Azithromycin is given orally once a day, it has a very long half life so is most commonly used. This cannot be given intravenously
Clarithromycin is 2 times a day
Erythromycin is given 4 times a day and if given intravenously it may cause swelling at the site of injection.

These drugs are often used when a patient has a penicillin allergy

Question 19

Outline the key characteristics of fluoroquinolone, giving examples and highlighting their mechanism of action, indication and adverse effects.

Answer 19

E.g., ciprofloxacin, levofloxacin, moxifloxacin, ofloxacin

These antibiotics will bind to messenger RNA presently mRNA synthesis and subsequently protein synthesis.

It is indicated for gram-negative bacteria as it has a broad spectrum mechanism of action. Dosing is twice a day. The most common side effect is myalgia (muscle weakness).

Question 20

Outline the key characteristics of aminoglycosides, giving examples and highlighting their mechanism of action, indication and adverse effects.

Answer 20

e.g., gentamicin, amikacin

These antibiotics work by binding to the 30s ribosomal subunit inhibiting it. These drugs are administered through IV and you can get gentamicin ear drops. Gentamicin has a narrow therapeutic window so must be monitored for nephrotoxicity and ototoxicity.

Question 21

Outline the key characteristics of Glycoproteins, giving examples and highlighting their mechanism of action, indication and adverse effects.

Answer 21

e.g., Vancomycin

These Antibiotics work by inhibiting cell wall synthesis. They come as both IV and oral formulations. The oral dosing is not absorbed in the GI tract at all. so it is used for C.Diff infections. The IV formulation is however not indicated for C.Diff.

It has a narrow therapeutic window so monitoring is required. It may also cause red man syndrome so the speed of infusion needs to be regulated.