antimicrobials

bactericidal drugs definition

kills the organism

bacteriostatic drugs definition

inhibits growth of the organism

gram positive organisms

thick cell wall

gram negative organisms

• outer membrane has lipolysaccharides (LPS)

• thin cell wall

what is MIC

minimum inhibitory concentration

classes of antibiotics

1. cell-wall agents

2. cell membrane agents

3. protein synthesis agents

4. Antimetabolites

5. nucleic acid agents

6. miscellaneous antibiotics

MOA of cell wall agents

only works on actively dividing and growing cells

• Interfere with synthesis of the cell wall

MOA of cell membrane agents

act on phospholipid bilayer of the cell membrane to alter its permeability

MOA of protein synthesis agents

inhibit formation of ribosomal units necessary for protein synthesis, preventing proteins to be made

MOA of anti-metabolites

inhibit synthesis of folic acid, hindering growth of gram positive and negative aerobic and anaerobic bacteria, and some protozoa

MOA of nucleic acid agents

inhibit DNA function

cell wall agents only work on which type of cells

actively growing and diving cells

what is the common structure of some antibiotics (Penicillin)

the Beta-lactam structure

semi-synthetic penicillins

• Amoxicillin

• Ampicillin

• Cloxacillin

• Methacillin

• Piperacillin

which semi-synthetic Penicillin is resistant to penicillinase

Cloxacillin and Methacillin

beta-lactamase

enzyme made by bacteria that destroy beta-lactam structure of Penicillin, leading to antibiotic resistance

• Amoxicillin is very susceptible to destruction

example of a potentiated amoxicillin that is resistant to B-lactamase. What is it used for

amoxicillin + clavulanic acid

• Clavamox, Clavaseptin

• Skin infections, UTI’s, and other soft tissue infections

cell wall agent examples

• penicillin

• cephalosporin

• bacitracin

• vancomycin

what is cephalosporin a close relative to

penicillin

different forms of cephalosporin

• cephalexin (PO)

• cephazolin (IV/IM)

• cefovecin (SQ)

• ceftiofur

side effect of Bacitracin if given PO

nephrotoxicity

• only give topically

when is vancomycin used

only for severe Staphy. or Strep. omfections with multiple drug resistances

• MRSP and MRSA

side effects of cell wall agents

• GI upset

• enteritis in rabbits if given PO

• idiosyncratic drug reactions to skin

why are cell membrane agents more toxic to mammal cells

because bacteria and mammals have cell membranes for the agents to act on and degrade

example of a cell membrane agent

Polymyxin B (Surolan)

• topical only!

side effects of cell membrane agents if given parenterally

damage to CNS and kidney

groups of protein synthesis agents

1. Aminoglycosides

2. tetracyclines

3. amphenicols

4. macrolides

5. lincosamides

example of an aminoglycoside (brand name), its side effects

Tobrex

• extremely nephrotoxic and ototoxic

examples of tetracyclines and side effects

• doxycycline

• tetracycline

SE: esophagitis, slow bone development and yellow teeth

Florfencicol (Osurnia and Claro) is used to treat what

• respiratory disease and foot rot in cattle

• helps treat Horner’s syndrome??

types of macrolides

• erythromycin

• tylosin

• tilmycosin

what does clindamycin treat

• Gram positive bacteria, and Toxoplasma

• pyoderma, dental infections, osteomyelitis

• may cause esophagitis → give with food

what group are fluoroquinolones part of

nucleic acid agents

examples of Fluoroquinolones

• Ciprofloxacin

• Enrofloxacin (Baytril)

• Marbofloxacin (Zeniquin)

• Orbifloxacin (Orbax)

• Pradofloxacin (Veraflox)

side effects of nucleic acid agents

• damage to growing animals

• caution in animals with neurological , kidney and liver disorders

Enrofloxacin route of admin and side effects

PO or injactable

• GI upset

• blindness in cats if >5 mg/kg/day

what are the miscellaneous antibiotics

• Nitrofurantoin

• Metronidazole (Flagyl)

• Rifampin

what does Metronidazole treat

Giardia and anaerobic bacteria infections

• narrow-spectrum bactericidal

what is a fungi

eukaryotic, non-photosynthetic cells with chitin in the cell wall and ergosterol in the membrane

• single-celled = yeast

• multi-cellular = moulds

mycosis

fungal infection

major side effect of Amphotericin B (polyene)

nephrotoxic

• targets ergosterol and cholesterol

• very effective, broad-spectrum

• given slow IV infusion

systemic or topical imidazole example

Ketoconazole

topical imidazole examples

• clotrimazole

• enilconazole

• miconazole

MOA of imidazoles and side effects

inhibit mammalian sterol synthesis causing endocrine effects and hepatotoxicity in cats

MOA of triazoles and side effects

inhibit cytochrome p450

• specific for fungal enzymes

• highly teratogenic

Groseofulvin treats what specifically

dermatophytes (ringworm)

examples of antiviral drugs

• Acyclovir

• Ganciclovir

• Famciclovir

what are interferons

help communicate between cells

• infected cells release interferon which helps other cells block viral replication

what are interferons useful for treating

gingivitis, atopic dermatitis, and neoplasia

what does L-lysine do

a supplement that helps lower arginine levels which is required for herpes virus replication

• increase lysine = decrease arginine

what does a diet lacking arginine lead to

• rapid weight loss

• refusal to eat

• death

how does bacteria acquire resistance to antimicrobials

1. Mutation

2. Gene transfer

nocosomial definition

originating in a health care setting

principles to follow to reduce antimicrobial resistance

1. demonstrate presence of pathogen

2. Prophylactic antimicrobials only used if animals are at risk, and morbidity and mortality will be decreased

3. Selection is based on known or suspected target organisms, their known/predicted susceptibility, and site of infection. Should know the drugs pharmacokinetics/dynamic properties and the hosts immunocompetance

4. Narrow-spectrum > broad-spectrum

5. Local therapy > systemic therapy

6. Follow drug use cascade

7. Antimicrobials should be used for the shortest time period required to achieve a cure for the infection

first line antimicrobials

used empirically with no pending culture results needed

second line antimicrobials

only used when justified by culture results

third line antimicrobials

use not justified, or only with culture results and consultation with infectious disease specialists