Antibiotics Ellie Whittingham

Overview • Thinking about Abx

• Know your enemy

• Classes of Abx

• Resistance

• Quiz o’clock

How do we feel about answering questions on Abx?

This is how I feel…..

How might Abx come up in the exams?

Know your enemy…

10 4

9

8

6

5

7

2

3

1

Gram Positive

Cocci

•Staphlococci

•Steptococci

Bacilli

•Clostridium

•Bacillius

Filamentous

•Actinomyces

Gram Negative

Cocci

• Neisseria

Bacilli

• Enterobacteria

• Pseudomonas

• Campylobacter

Spirochetes

• Leptospirosis

• Syphylis

Intracellular

• Chlamydiae

What classes of Abx can you list?

Classes of ABx

ABx

Inhibit wall synthesis

Beta Lactams Carbopenems

Cephalosporins Glycopeptides

Inhibit bacterial protein

synthesis/ Messes with

ribosome

Aminoglycosides

Chloramphenicol

Clindamycin

Fusidic Acid

Macrolides

Tetracyclines

Inhibit nucleic acid synthesis/

Messes with DNA

Metronidazole

Nitrofurantoin

Quinolones

Rifampicin

Sulphonadmides

Bacteriocidal vs Bacteriostatic

Let’s break it down…

What can we target?

1

3

2

Must be a living

replicating bacteria

Inhibit Cell Wall Synthesis

Cell wall

Beta Lactams

Penicillin(s)

Many Gram Neg unaffected

e.g. Flucloxacillin, Amoxicillin, Piperacillin

(combined with Tazobactam)

Monobactams

Best coverage

e.g. Meropenem, Ertapenem

Cephalosporins

Subsequent generations

• Increasing Gram Neg cover

• Better CNS penetration

e.g. Cephalexin (1st), Cefuroxime (2nd), Ceftriaxone

(3rd)

Glycopeptides

Principally work against Gram positive cocci

Narrow spectrum

e.g. Vancomycin, Teicoplanin

Inhibit protein synthesis

Ribosomes

Messes with 50s Subunit

Chloram-phenicol

H. Influenzae

Macrolides

Erythromycin, Clarithromycin

Lincosamide

Clindamycin

Linezolid

Resistant Gram Positives

50s

30s

Messes with 30s Subunit

Aminoglycosides

Aerobic Gram Negatives

Gentamicin, Neomycin

Tetracyclines

Mycoplasma, Sprirochetes

Avoid in children <12 yrs

Tetracycline, Doxycyline

Inhibits nucleic acid synthesis (messes with DNA synthesis)

“Nucleus”

Messes with DNA Synthesis

DNA Synthesis Inhibitors

Fluoroquinolones

e.g. Ciprofloxacin, Levofloxacin,

Metronidazole

(Anaerobes)

RNA Synthesis Inhibitors

Rifampicin

Folic Acid Synthesis Inhibitors

Sulfonamides

Trimethoprim

Resistance • Intrinsic

• Abx doesn’t work for that bacteria – target not present or antibiotic cannot enter bacterium

• E.g. B-lactam agents have no effect against mycoplasma

• Acquired • Mutation • Transfer of genetic material from resistant

organisms

Quiz time!

Which class of bacteria have a thick

purple cell wall on staining?

Gram Positive

Quiz time!

What are the 3 main ways Abx work?

Inhibit Cell Wall

Synthesis

Mess with ribosomes to

inhibit protein

synthesis

Mess with DNA

synthesis

Quiz time!

Are B-Lactams bacteriostatic or

bacteriocidal?

Quiz time!

What Abx work via interfering with DNA

synthesis?

Rifampicin Fluoroquinolones e.g.

Ciprofloxacin

Trimethoprim

Quiz time!

What type of bacteria do Glycopeptides

principally work on?

Questions?

Resources used

• http://www.frcamindmaps.org/mindmaps/primarybits/antibiotics/antibiotics-assets/antibiotics.png

• https://academic.oup.com/bjaed/article/9/6/184/378495

• https://bjaed.org/article/S2058-5349(17)30054-9/abstract

• http://www.frca.co.uk/Documents/190%20Microbiology%20for%20anaesthetists%20part%201%20-%20Pharmacology%20of%20antibacterial%20and%20antiviral%20drugs.pdf

• https://www.orthobullets.com/basic-science/9059/antibiotic-classification-and-mechanism