Antimicrobials and Their Mechanisms

Antimicrobials that kill bacteria directly.

Antimicrobials that stop bacterial growth.

Inhibits bacterial cell wall synthesis by targeting penicillin-binding proteins (PBPs).

Antimicrobials whose effectiveness increases with higher concentrations.

Antimicrobials whose effectiveness depends on the duration of exposure, not concentration.

The core structure of beta-lactam antibiotics, responsible for their antibacterial activity by inhibiting bacterial cell wall synthesis.

Enzymes produced by bacteria that break down the beta-lactam ring, rendering the antibiotic ineffective.

Combining a beta-lactam antibiotic with an aminoglycoside, where they work better together than alone.

A beta-lactamase inhibitor that protects penicillin-type antibiotics from inactivation.

A combination drug containing amoxicillin, a penicillin antibiotic, and clavulanic acid, a beta-lactamase inhibitor.

Penicillin is effective against gram-positive bacteria, anaerobes, and some gram-negative bacteria, BUT it has limited effectiveness against beta-lactamase producing bacteria.

Penicillin G is a fast-acting antibiotic used for urgent treatments of severe bacterial infections, especially those caused by sensitive gram-positive bacteria and anaerobes.

Penicillin's side effects include hypersensitivity reactions (allergies), procaine reactions (CNS stimulation), electrolyte imbalances (heart problems), and GI upset.

Aminopenicillins, like ampicillin and amoxicillin, are modified penicillins with broader activity, including against some gram-negative bacteria.

Amoxicillin, unlike ampicillin, is more easily absorbed orally and its absorption isn't affected by food.

Ampicillin comes in different forms, like sodium and trihydrate. Trihydrate shows 'flip flop' kinetics, meaning its half-life changes depending on dosage.

Penicillin G is a water-soluble salt that breaks down quickly in the body when given orally. Therefore, injections (IV, IM, SQ) are required for effective delivery.

Procaine Pen G is a longer-acting formulation that can be injected into muscle (IM) for sustained effects.

These penicillins are specifically effective against staphylococcus bacteria. They are important because they can be used to treat infections caused by methicillin-resistant Staphylococcus aureus (MRSA).

Some bacteria, particularly Staphylococcus aureus, can develop resistance to methicillin and other Beta-lactam antibiotics. This resistance means that the antibiotic cannot effectively kill the bacteria and can make infections harder to treat.

These penicillins have a narrow spectrum of activity but are specifically effective against Pseudomonas aeruginosa, a gram-negative bacteria that can cause serious infections.

Some penicillins can work synergistically with other antibiotics, such as aminoglycosides. This means that the combination of drugs is more effective than either drug alone.

The bioavailability of penicillins refers to the amount of the drug that reaches the bloodstream after it is administered. Some penicillins have good oral bioavailability, while others need to be given intravenously or intramuscularly.

Many Gram-negative bacteria have developed resistance to penicillins. This is often due to the production of beta-lactamases, which break down penicillin molecules making them ineffective.

Cefadroxil, cephalexin, cephapirin, cefazolin. Broad-spectrum antibiotics effective against many gram-positive and some gram-negative bacteria.

Cefoxitin. Broad-spectrum antibiotics with increased activity against gram-negative bacteria compared to 1st generation.

PO well-absorbed in dogs, cats, and horse neonates, but erratic in older foals, ruminants, and horses. IM/SQ results in rapid absorption.

Low volume of distribution. Primarily in the extracellular fluid, including pleural, pericardial, and synovial spaces. Penetrates bone.

Unchanged drug eliminated through the kidneys via glomerular filtration. Very short half-life. Protein binding increases half-life in 3rd generation cephalosporins.

Similar to penicillin G: Coagulopathies, blood dyscrasias, GI upset (give with food), nephrotoxicity (avoid use with aminoglycosides). Injection site inflammation possible with cetiofur.

Ceftiofur, cefovecin, cefotaxime, cefpodoxime, ceftazidime. Broad-spectrum antibiotics with increased activity against gram-negative bacteria compared to 2nd generation.

Cefquinome. Broad-spectrum antibiotics with excellent activity against many gram-positive and gram-negative bacteria.

A cephalosporin with a long duration of action, given subcutaneously, primarily used in dogs and cats.

A cephalosporin less effective against some gram-positive bacteria like Corynebacterium, Streptococcus, and Staphylococcus.

Methicillin-resistant Staphylococcus aureus or Staphylococcus pseudintermedius, which are resistant to many antibiotics.

Penems are 'last resort' drugs in human medicine with broad activity against many bacteria.

Imipenem side effects include nephrotoxicity (kidney damage) and seizures requiring slow IV administration.

Aztreonam, a monobactam, is generally avoided in veterinary medicine due to limited clinical indications.

Aminoglycosides bind to the 30S ribosomal subunit, inhibiting protein synthesis, causing bacterial death.

Monitoring aminoglycoside levels is crucial due to potential accumulation in the kidneys and development of resistance.

Gentamicin and amikacin are commonly used for IV, IM, SQ, intra-articular, and IO routes, even for intrauterine infusions.

Spectinomycin is a narrow-spectrum antibiotic effective against gram-negative aerobes, but unpredictable against rods.