VMP 420 Intro to antibiotics/immunology/vaccines ( may be on E1)

Antimicrobials

medicines used to prevent and treat infections caused by microorganisms in humans, animals and plants

Antimicrobial drugs works only against ONE type of organism

• antibiotics( also known as antibacterials)

  • prevents/treats infections caused by bacteria ex: cellulitis, urinary tract infection, TB. STIs

• antifungals

  • prevents/treats infections caused by fungi ex: thrush, ring worm, athletes foot

• antivirals

  • prevent/treat infections caused by viruses ex: COVID, colds, flus, shingles/chickenpox

• antiparasitic

  • prevent/treat infections caused by parasites ex: malaria, threadworm, and headlice

Quick history of antibiotics

6 Key Considerations in Antibiotics Use

1. Mechanism of action

2. Spectrum of activity

3. Dosage

4. Route of administration

5. Meat quality

6. FDA legalities

Classification-Effect

Bactericidal v bacteriostatic

Mechanisms of action from antibiotics

1. inhibition of cell wall synthesis

2. inhibition of protein syn

3. inhibition of nucleic acid syn

4. damage to plasma membrane

5. synthesis of essential metabolites

Antimicrobial Resistance

• Specific bacteria have heritable traits that interfere with the mechanism of action of an antibiotic and render it ineffective.

• AMR (antimicrobial resistance) - social and political issue.

• What is resistance?

  • Parameter defined based on laboratory concepts.

    • In vitro X In vitro

    • MIC (Minimum Inhibitory Concentration) and MBC (Minimum Bactericidal Concentration)

  • Determining factors

    • ATB concentration at the infection site

    • Pharmacokinetics: Absorption, distribution, biotransformation and excretion •

    • Pharmacodynamics: concentration drug X antimicrobial activity

    • Host's own contribution against MOs

    • Time to start therapy

Choosing an Antibiotic Treatment

• Susceptibility versus Resistance

• Immediate assumption:

  • specific bacteria are susceptible

• Lab confirmation in > 2 days:

  • Identify bacteria and sensitivity tested to multiple antibiotics

Spectrum of Activity

• Broad Spectrum Antibiotic:

  • Few bacterial types can resist the antibiotic.

  • Broad Spectrum Antibiotics are usually more reliable when:

    • Resistance pattern unknown

    • Infection by multiple types of bacteria

how to stain gran - / gram +

1. crystal violet

2. iodine

3. alcohol

4. safranin

Some antibiotics primarily affect gram positive bacteria

ex:

• penicillin

• tylosin

Some antibiotics primarily affect gram negative bacteria

ex:

• gentamicin

• neomycin

Some antibiotics affect gram - and gram +

• ex: ceftiofur, tetracycline

• Response: More reliable when bacterial type and resistance pattern is unknown.

Dosage

• Level of the Antibiotic Administered to Animals

  • How much (mg/lb, iu/lb, ml/lb)

  • How often (# doses/day)

  • How long (# days)

  • Route of administration (oral, subcutaneous, intramuscular, intravenous)

multiple doses effective period

long-acting antibiotics

Dosage Requirements

• Adequate Dose(s) Given

• Doses Repeated Steadily

• Adequate Duration

  • –Until Response: 5 Days - 2 Weeks

  • Absolute Minimum: 3 Days

  • Consider long-acting antibiotics.

  • Recurrence: Drastic Condition

Route of Administration

• Topical Administration

  • Direct Application to Skin

    • Many daily applications

    • Individually contained animals: dairy cows, horse

  • Production Animals:

    • Unimportant route for most antibiotics

• Parenteral Injection (Infuse into tissue via a needle)

  • Intramuscular (IM)

    • Anatomical site is species specific.

    • Needle size – age, species, product specific

  • Intravenous (IV) – Typically jugular vein.

  • Subcutaneous (SQ)

  • Less Common:

    • intrarticular, intraperitioneal

• Oral Administration

  • Antibiotic Given Into the Mouth:

    • Treatment of individual animals

      • ✓ Boluses (Large Pills)

      • ✓ Drenches and Pumps

      • ✓ Paste Syringes

    • Group Treatment of Animals:

      • Common:

        • ✓ 65% of antibiotic expenditure

        • Methods: ✓ Water ✓ Feed

Boluses and Drenches

Group: Water Medication

Group: Feed Medication

medication put in groups feed

Regulations – Veterinary Feed Directive [VFD]

Advantages of group treatment over parenteral injections

• Large Animals:

  • Difficult to restrain

  • reduced stress of administration

  • less labor

• may be thousands to treat-population vs individuals

Advantages of parenteral injections over group treatment

• Oral: Longer time to reach treatment level in tissues

• Oral: Sick animals do not eat and drink well

• Group Oral: Costly - every animal is treated

Antibiotics Absorbed After Oral Administration

• Oral antibiotics must be absorbed by the gut in order to reach the lungs and other organs

• Not Absorbed: Neomycin, Gentamycin, Spectinomycin

Antibiotic Characteristics For Water Medication

• Water Soluble Antibiotics: Evenly disperse in water for accurate dosing

• Suspensions: Treatment mixture must be stirred

• Palatability: Imperative that animals continue to drink.

Injection Site Damage

• Meat: Injection Site Blemishes

• Animals: Blemishes are related to discomfort.

Parenteral Carriers: Injectable Solvents

• Aqueous Carriers:

• Antibiotics that are water soluble or suspend in water.

  • Soluble: Clear Solution

  • Suspension: Precipitate

• Oil Carriers:

  • Polypropylene Glycol (PPG)

Carrier Irritation

• Aqueous - Little tissue irritation.

• PPG Carriers - Very Irritating

  • Painful at injection site

  • swollen tissue

  • complication= abscess =/- scar

• ex in pic pigs lost sciatic nerve due to damage from injection to sciatic nerve

Reducing Injection Site Irritation

• Limit volume injected.

  • Base volume on animal size and caustic property of product.

    • Cattle (>500#)- 10 ml per site

    • Hogs (100#-250#)- 5 ml per site

• Consider SubQ route.

  • cattle and other ruminants

  • use subq route if label directions advise

Reasons for Antibiotic Failure

• Misdiagnosis: viral, animal flow, environmental, nutritional, PPM

• Improper Dosing: Bacteria resistant to selected antibiotic

• Irreversible Damage: too late, impossible

Residue Avoidance

Immunology timeline

Concepts

• Immunity •

  • Ability to resist infection.

• Immunology

  • Study of all aspects of host defense against infection and of the adverse consequences of the immune response.

• ⚫ Pathogen

  • Microorganisms that can cause disease when they infect a host.

• ⚫ Antigen/Immunogens •

  • Recognized by the body as non-self and stimulates an acquired immune response.

types of immunity

• innate immunity

• acquired (adaptive) immunity

  • humoral immunity

  • cell-mediated immunity

    • naturally acquired immunity

    • artificially acquired immunity

innate immunity

• antigen-nonspecific defense mechanisms

• very rapid response to almost any antigen

• born w it

• initial response to eliminate microbes and prevent infection

  • examples: anatomical barriers (skin), mechanical removal (saliva, mucus), antigen-nonspecific defense chemicals

acquired immunity

• antigen-specific

• takes several days to become protective

• develops through life

• reacts w and removes specific antigen

natural barriers

APCs (antigen-presenting cells)

• dendrit cells

• macrophages

• B cells

2 types of acquired immunity

• humoral immunity

  • involves production of antibody molecules in response to an antigen and is mediated by B-lymphocytes

  • antibodies or immunoglobins are produced by B-lymphocytes and plasma cells in response to specific antigen

  • antibodies circulate in blood and enter tissue via inflammation

  • effective against bacteria, bacterial toxins, and viruses prior to these agents entering cells

  • there are 5 classes antibodies: IgG, IgM, IgA, IgD, and IgE

• cell-mediated immunity

  • involves production of cytotoxic T-lymphocytes, activated macrophages, activated NK cells, and cytokines in response to an antigen and is mediated by T-lymphocytes

2 types of naturally acquired immunities

• ACTIVE naturally acquired immunity

  • natural exposure to an infectious agent or other antigen

  • body responds by making its own antibodies

• PASSIVE naturally acquired immunity

  • ex: placental transfer of antibodies from mother to fetus during pregnancy

  • antibodies( IgA, IgG) found in colostrum and milk

ACTIVE ARTIFICIALLY acquired immunity

• Any immunization with an antigen.

• The body will produce its own ANTIBODIES and develop circulating, long-lived B-memory cells.

• If the body is again exposed to that same antigen, the memory cells will cause immediate and rapid production of the appropriate antibodies for protection.

phases of adaptive immune responses

classes of lymphocytes

pathways

phases of lymphocyte activation (a)

phases of lymphocyte activation (b)

summary of innate vs adaptive

vaccination

• not treatment for disease it is to PREVENT

• why important?

  • protects individuals/ animals- effective

  • eradication

  • clinical signs/ shedding

important Concepts

• ACTIVE IMMUNITY IS NOT ABSOLUTE

  • animal can become diseases

    • high levels of virus/bacteria

    • animal in poor health/condition

    • stressful environment

  • animal can still become infected

    • may not show disease

  • Passive immunity can block active immunity

types of vaccines- VIRUSES

• live viruses

  • rarely used

  • feedback programs in pigs

• modified live viruses

  • common, PRRSV in pigs, IBR in cattle

  • can be pathogenic to fetuses, sick animals, or other species

types of vaccines- bacteria

• modified live bacteria

  • becoming more common

  • salmonella, erysipelas, ileitis in pigs

  • caution: do not use antibiotics at time of vaccination

• killed

  • safety improved over modified live

  • immunity may be incomplete

types of vaccines-others

• toxoids

  • inactivated toxins

  • animal produces antibpody response

  • ex: tetanus toxoid in horses, clostridial toxoids for sheep and pigs

• antisera

  • antibodies in serum from another animal

  • does not stimulate active immunity

  • ex: tetaus antitoxin

• new genetically engineered vaccines

killed vs modified live

adjuvants that enhance immune responses

handling vaccines

• remember- made from living organisms

• keep in fridge (unless instructed otherwise)

• opened bottles of killed virus/bacteria can be stored and reused

• opened bottles of MLV or bacteria should be discarded

• keep vaccines away from heat and sunlight

• do not mix vaccines in same syringe

  • formalin in bacterins will kill MLV

• caution: disinfectants for cleaning syringes will kill MLV vaccines

• use appropriate routes of administration- IM vs SubQ vs oral

• use appropriate needle length