Antibiotics Lecture Notes PDF

Antibiotics 1. Bacitracin 2. Fluoroquinolones 3. Sulphonamides 4. Nitrofurans  Bacitracin  Bacitracin disrupts the bacterial cell wall like penicillins and cephalosporins, but not via the same mechanism.  It is a ‘polypeptide’ antibiotic (long chains of amino acids)...

Antibiotics 1. Bacitracin 2. Fluoroquinolones 3. Sulphonamides 4. Nitrofurans  Bacitracin  Bacitracin disrupts the bacterial cell wall like penicillins and cephalosporins, but not via the same mechanism.  It is a ‘polypeptide’ antibiotic (long chains of amino acids)  Does not have a beta-lactam ring therefore they are NOT susceptible to beta- lactamase  Works primarily against gram-positive bacteria  Primary uses:  Topical  Ophthalmic  Feed Additive (b/c it is poorly absorbed?)  *Toxic to the kidneys  Generally found in preparations that are in combination. Example: Bacitracin + Neomycin + Polymyxin B  Topical Creams  Triple Antibiotic Ointment Neomycin Polymyxin B + Dexamethasone Dexamethasone  Notes: BNP Drug Adverse Side Effects Polymyxin B: nephrotoxicity & neurotoxicity Bacitracin: nephrotoxicity Neomycin: nephrotoxicity   Vancomycin®️ Vancomycin hydrochloride -not commonly seen used in vet med. -it is a glycopeptide antibiotic - it is the drug of choice for the nosocomial multidrug resistant pathogens.  Inhibition of the bacterial enzyme DNA-gyrase  Excreted in kidney or bile  Have a high Therapeutic Index  Broad spectrum [ Salmonella + Pseudomonas ]  Not for use in young animals  Chelation may occur  Aluminum  Well absorbed into tissue and fluids  Iron  Calcium  Zinc  Oral & parenteral use  E.g.: do not give with sucralfate  Metabolized in liver  Flexible dosing that is based on bacterial sensitivity and penetration of the drug at the site.  Exhibit a “post antibiotic effect” ???  So Many To Choose From…..  A180 (danofloxacin) , cattle  Veraflox Dog Tablets  Baytril® Injectable Solution  Otic solution  Vigamox® Ophthalmic  Veraflox Oral Suspension  Ciprodex  Ciloxan Ophthalmic Solution  Ciprofloxacin+dexamethasone  Zeniquin®  Forcyl (marbofloxacin)  Aurizon® (Otic)  Marbofloxacin,dexamethasone,clo trimazole  Enrotron 50® 1. Baytril® (Enrofloxacin), 1980’s  IM**, PO , IV  Genitourinary tract , skin infections , respiratory tract  Caution: young dogs , foals , cats not so much  Puppies most susceptible at between 4-28 wks. of age 2. Zeniquin (marbofloxacin) 3. Orbax (orbifloxacin) 4. Cipro (Ciprofloxacin) 5. Dicural (difloxacin) *Cattle withdrawal time is 28 days! *Extra label use of fluoroquinolones in animals that produce food is ILLEGAL!!  Interfere with DNA metabolism - bacteriostatic  Were the first antibiotic used on large populations  Initially they were excellent drugs for the treatment of pneumonia  d/t widespread use there are problems with resistance to them  Sulfonamides may be administered orally , parenterally , & topically  Enteric vs. Systemic  Readily enter CSF = Tx: meninges  Potentiated Sulfonamides are those which are combined with other compounds to convert them from a bacteriostatic drug to one which is bactericidal.  Tribrissen® [sulfadiazine]  Trimidox® [sulfadoxine]  Borgal® [sulfadoxine]  Potentiation of Sulfonamides examples:  Sulfadimethoxine (Albon®)  Trimethoprim  Sulfadiazine +  Ormetoprim  Sulfamethoxazole  Sulfasalazine*  Pyrimethamine Sulfonamide + Potentiating compound is usually 5:1 ratio Sulfa  Sulfamethoxazole and Sulfatrim DS trimethoprim  Sulfadiazine and TMS Oral Granules trimethoprim 3 Precautions: 1.Crystalluria 2.KCS 3.Blood Dyscrasias Crystalluria  Occurs as a result of the sulphas and their metabolites being present in the urine , and the urine is at a low pH  Prevention………………. 1)Alkalinize urine 2)Incr. Urine volume 3)Don’t overdose  KCS  …keratoconjunctivitis sicca  Sulfonamide induced  Crusting , mucoid discharge around eyes  Pawing and rubbing of face  KCS So monitor tear production in  …keratoconjunctivitis sicca animals that are on long term therapy with a  Sulfonamide induced sulfonamide drug.  Crusting , mucoid discharge around eyes  Pawing and rubbing of face  Blood Dyscrasias  Because folic acid is required for RBC-production , the sulfonamides interfere by competitive inhibition.  IE: block PABA at TWO sites  hemolytic anemia  thrombocytopenia  agranulocytosis  NITROFURANS  Broad spectrum of activity; bacteriostatic  Less potent than traditional antibiotics  Rapid renal elimination and so often does not reach therapeutic levels in tissues  ~ half of drug is secreted unchanged and therefore used to treat infections of the bladder and urethra  Examples of Nitrofurans:  Topazone®️(furazolidone)  Equifur®️(nitrofurantoine)  Furacin®️Soluble Dressing (nitrofurazone)  NFZ Powder®️