Infections Lecture 2: Bacterial Infections, anti-bacterial agents and mechanisms of action

Question 1

What are the symptoms of a bacterial infection?

Answer 1

Malaise, fever and chills

Question 2

What are the two different types of bacteria?

Answer 2

1. Gram +ve- thick peptidoglycan

2. Gram -ve- thin peptidoglycan

Question 3

How does penicillin work? And where is it excreted mainly?

Answer 3

1. Bactericidal that inhibits cell wall synthesis by interfering with peptidoglycan and it acts as a bactericidal
2. Excreted mainly in the bile and urine

Question 4

How do cephalosporins (beta lactams) work? And where are they excreted mainly? What are the side effects?

Answer 4

1. Bactericidal that interfere cell wall synthesis by interfering with peptidoglycan synthesis after binding to the Beta-lactam-binding proteins
2. Excreted mainly in urine
3. Side effects: Nephrotoxicity, diarrhoea, similar to penicillin

Question 5

How do Fluoroquinolones work? And where are they excreted mainly?

Answer 5

1. Bactericidal that inhibits DNA gyrase

2. Excreted by kidneys and metabolised by liver

Question 6

How do Aminoglycosides work? And where are they excreted mainly?

Answer 6

1. Bactericidal inhibit protein synthesis

2. Excreted unchanged in urine

Question 7

How do Tetracyclines work? And where are they excreted mainly? What are the unwanted side effects?

Answer 7

1. Bacteriostatic inhibit protein synthesis
2. Excreted mainly in urine
3. Side effects: GI disturbances, staining growing teeth and bone deformities

Question 8

How do Metronidazole work? And where are they excreted mainly?

Answer 8

1. Bactericidal are toxic to cells by interfering with electron transport/producing free radicals
2. Metabolised in liver

Question 9

How does Chloramphenicol work? And where are they excreted mainly?

Answer 9

1. Bacteriostatic folate antagonist/inhibits folate synthesis
2. Metabolised in liver and excreted in kidney

Question 10

How does sulphonamides work? What are the unwanted side effects and its clinical use?

Answer 10

1. Targets folate synthesis pathways by competing with PABA which is an essential precursor in folic acid synthesis in bacteria
2. Side effect: nausea, vomiting, headaches, rashes
3. Used in UTIs and eye infections

Question 11

Give examples of the main antibiotics that affect the cell wall synthesis

Answer 11

Penicillin, Beta-lactamase inhibitors, Carbapenems

Question 12

How does Trimethoprim work, what are the side effects and the clinical uses of it?

Answer 12

1. An agent that interferes with the synthesis or action of folate by acting as a folate antagonist
2. Side effects: Nausea, vomiting, blood disorders and skin rashes
3. Clinical use: Urinary and respiratory tract infection

Question 13

What does bacteriostatic mean?

Answer 13

Inhibits the growth of bacteria but doesn’t kill them

Question 14

What are the clinical uses of penicillin? Give the main examples and their uses?

Answer 14

1. Severe infections of sensitive organisms (bacterial meningitis): benzylpenicillin
2. Bone and Joint infections (staphylococcus auereus): Flucloxacillin
3. Skin and soft tissue infections (staphylococcus auereus): Benzylpenicillin, flucloxacillin, PHENOXYLMETHYLPENICILLIN
4. Otitis media: amoxicillin
5. Bronchitis: amoxicillin
6. Pneumonia: amoxicillin

Question 15

What are the clinical uses of cephalosporins? Give the main examples and their uses?

Answer 15

1. Septicaemia (cefuroxime, cefotaxime)
2. Meningitis (ceftriaxone, cefotaxime)
3. Urinary tract infection (pregnancy)- Cefalexin

Question 16

What are the clinical uses of tetracyclines? And what is a common drug form of it?

Answer 16

1. Rickettsial and chlamydial infections, brucellosis, anthrax and lyme disease
2. Doxycycline

Question 17

What are the clinical uses of chloramphenicol? Give the main examples and their uses?

Answer 17

For serious infections where benefit of drug outweighs haematological toxicity such as

• Haemophilus influenzae resistant to other drugs
• Meningitis in patients when penicillin cannot be used
• Safe for “Bacterial conjunctivitis (topical)”

Question 18

What are the clinical uses of aminoglycosides? And what are the unwanted side effects?

Answer 18

1. Effective against many aerobic G-ve and some Gram +ve
2. Mainly gram -ve enteric organisms
3. Sepsis
4. Unwanted side effects: Ototoxicity and nephrotoxicity

Question 19

How do macrolides work and give some example of the main drugs

Answer 19

1. Inhibit protein synthesis, bactericidal or bacteriostatic (concentration and organism)
2. Erythromycin (main one), Clarithromycin, Azithromycin, Spiramycin, Telthromycin

Question 20

What are the clinical uses of streptogramins and give some example of the main drugs?

Answer 20

1. Mostly Gram -ve enteric organisms
2. Treatment of severe infections in combination
3. Examples: Quinupritsin and Dalfropristin

Question 21

What are the clinical uses of Lincosamides and give some example of the main drugs?

Answer 21

1. Bone and joint infections.

2. Clindamycin- Gram +ve cocci (penicillin resistant staph)

Question 22

What are the fluroquinolines clinical uses?

Answer 22

1. Complicated urinary tract infection
2. Gonorrhoea
3. Bacterial Prostatitis
4. Anthrax (ciprofloaxin)

Affect the DNA gyrases

Question 23

What is the antibiotic mechanism for Glycopeptides? Give the 2 examples of the drug and what are its clinical uses?

Answer 23

1. Inhibit cell wall synthesis
2. Examples: Vancomycin and teicoplanin
3. IV for multi-resistant staphylococcal infections
4. Orally: Clostridium Difficile

Question 24

What is the antibiotic mechanism for polymyxins? Give the example of a drug and what are its clinical uses?

Answer 24

1. Disrupts bacterial cell membrane
2. Colisitin
3. Only used topically