Antimicrobials 1 + 2
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What is the goal of antimicrobial therapy?
Eliminate infectious organism without toxicity to host
What is the most important thing to try and augment when treating bacterial infection?
Natural defence mechanism
Give 3 examples of natural defences and when these may be compromised
• mucociliary escalator (cystic fibrosis) • flushing effect of urination (catheter placement) • normal gut flora (gut dysbiosis)
What are the 4 quadrants targetted by the antimicrobial spectrum? What else may “4 quadrants” of microbes also refer to?
• G+ aerobes/ G- aerobes/ Obligate anaerobes (G+-)/Penicillinase producing staph • G+/G- aerobes/ G+/G- anaerobes
Give 4 examples of G+ aerobes
• Strep (B haemolytic) • Enterococcus • Pnumococcus • Bacilli (lactobacillus, corynebacterium, listeria, erysopalathrix, arcanobacterium)
Give 6 examples of G- aerobes
• E. Coli • Klebsiella • Helicobacter • Campylobacter • Pastuerella • Psuedomonas
Give 5 examples of staph
• aureus • saphrophyticus • epidermis • haemolyticus • capitis
Give 4 broad examples of anaerobes
• G+ spore forming clostridium (perfringens, botulinum, tetani) • G+ bacilli (actinomyces, lactobacillus, bifdobacterium) • G- bacilli (fragillis or not fragillis) • Cocci (peptococcus niger)
Give 6 examples of atypical bacteria
• Rickettsia (not uk disease) • Mycoplasma • Chlamydia • Borrelia • Bartonella • Mycobacterium
Where are many antimicrobial substances derived from?
Fungus
Give conditions when rational antimicrobial use can be justified
• bacterial infection definitively diagnosed • OR highly likely • disease will progress without medical therapy • would casue critical illness if occourred and not recognised/treated
What essentially useless treatment should be given inlieu of prescribing antibiotics as a placebo because you don’t know what else to do?
Vitamin injection
Give some clues of bacterial infection
• heat, redness, swelling • pyrexia (could also be viral/fungal/neoplasia) • neutrophilia (stress leukogram) • bacterial cause COMMON?!
Give 3 examples where ABx are commonly prescribed but a bacterial aetiology is rare
• V+ D- = acute gastritis due to eating rubbish etc. No bacteria casues V+D-! except helicobacter but v. rare • Hameaturia in young cat <10y = idiopathic cystitis usually due to stress, will resolve within 5-7d. In DOGS haematuria indicates UTI but cat urine so concentrated these are RARE. • Haemotochezia = no evidence of need for antimicrobials unless signs of sepsis seen
What 5 factors influence the success rate of ABx Tx?
• what bugs live where? • bacterial susceptibility • Pharmacokinetic phase - getting the drug to the infection • Pharmacodynamic phase - Local conditions • Client comlpliance
Give the 3 main sources of infection with egs.
• Environment - mycobacteria, tetanus, contaminated food (campylobacter, E. Coli) • Other animals - Bordatella • Internal - GI (E. Coli, G-s, Anaerobes) - Skin (Staph - S. Aureus, Strep in horses )
How does previous ABx Tx affect the decision making for rational ABx use?
changes susceptibility profile of bugs
How do horses differ from SAs with wound infection risks?
Strep ^ risk in horses than staph/
What bacteria usually causes mastitis in cattle?
Staph
How should sepsis of unknown origin be treated?
Cover all 4 bacterial quadrants
What is the common cause of pneumonia?
Difficult to predict bacteria
What is the common cause of endocarditis, arthritis or discospondylitis?
Staph -> systemic infection from the skin
What is the exception to the rule of bacteria which are resistant to a drug in vitro being resistant in vivo?
• stats based on blood concentration of drug - > resistence may be overcome by high concentrations achieved in urine/topically
Define MIC. How is this used clinically?
Minimum inhibitory concentration • lowest concentration of a drug to inhibit bacterial growth • MIC90 used as therapeutic dose (conc that inhibits 90% bacterial isolates of a specific species eg. e coli, s. pseudointermedius)