10th lecture - broad-spectrum antibiotics Flashcards
Broad-spectrum antibiotics are effective against
both gram neg. and pos. bacteria
Tetracyclines are
broad-spectrum, bacteriostatic;
inhibit the protein synthesis of microbes.
Resistance occurs relatively quickly.
Cross-resistance occurs with penicillins.
Tetracyclines Pharmacokinetics
Well absorbed in case of all routes of administration.
They undergo the enterohepatic circulation if administered through the oral route.
They are eliminated through the kidneys and in the bile.
Tetracyclines accumulate in
calcium-containing tissue (bones and teeth), forming a stable complex with calcium.
It is not recommended to administer to young animals.
Tetracyclines Toxicity
Have an irritant effect both when administered PO and injection (vomiting, pain at the site of the injection and tissue damage).
The animal may collapse in case of administration into the vein.
Tetracyclines may lead to kidney damage, dehydration, haemoglobinuria and an overdose will lead to liver damage.
Name 4 examples of Tetracyclines
Tetracycline hydrochloride
Oxytetracycline hydrochloride
Doxycycline hyclate
Minocycline hydrochloride
Chloramphenicol, thiamphenicol and florfenicol are all?
Broad-spectrum and bacteriostatic.
They suppress the metabolism of microbes.
Chemically similar while toxicity and pharmacokinetics are different.
Describe Chloramphenicol
Broad-spectrum, potent, the most toxic antibiotic drug in existance.
Is used primarily for topical treatment.
Prohibited for use in farm animals.
Do not administer Chloramphenicol with
other antibiotics, especially bactericidal antibiotics, antagonism will occur.
Chloramphenicol Increases the potency of
barbiturates, phenylbutazone, xylazine and ketamine.
Do not use together with these substances, this may cause death.
Chloramphenicol toxicity
the most toxic antibiotic drug in existance.
Due to extremely high toxicity, it is only recommended to use it locally, primarily for the treatment of eye and ear infections.
Damages bone marrow, inhibits haematopoiesis - aplastic anaemia.
Chloramphenicol side effects
It has been found to cause depression, dehydration, loss of appetite, vomiting and loss of body mass.
Damages bone marrow, inhibits haematopoiesis - aplastic anaemia.
Chloramphenicol Pharmacokinetics, absorption
It is well absorbed in case of all routes of administration.
Half-life varies among species.
Penetrates the barriers of the organism well. Therapeutic concentration reached quickly in all body fluids.
Chloramphenicol Pharmacokinetics, excretion
Mainly excreted in urine, also partially in the bile.
Thiamphenicol is a
broad-spectrum derivative of chloramphenicol with lower activity compared to chloramphenicol, significantly lower toxicity too.
Not prohibited for use in farm animals like chlormaphenicol is.
It is absorbed and distributed well, primarily excreted with urine.
Florfenicol is a
broad-spectrum Fluorinated derivative of thiamphenicol.
Spectrum of activity is similar to that of chloramphenicol with a lower toxicity.
After prolonged use, bone marrow damage may develop.
Primarily used for the treatment of respiratory tract infections in cattle and treatment of furunculosis in fish.
Fluoroquinolones are…?
Broad-spectrum, bactericidal.
Resistence occurs relatively quickly. Quinolones should be left as the so-called “reserve antibiotics”.
Fluoroquinolones Mechanism of action..?
They inhibit the DNA synthesis of microbes, are batericidal.
Activity against microbes depends on the concentration level. Bacteriostatic effect (paradoxical) prevails at higher concentrations.
Fluoroquinolones Pharmacokinetics, absorption and excretion
Well absorbed and distributed in case of all routes of administration.
They are metabolised in the liver and excreted with urine and in the bile.
Fluoroquinolones may lead to what after long term therapy?
They may lead to joint cartilage erosion, not recommended for young animals.
They may also cause vomiting, diarrhoea and sometimes nervous symptoms (cramps, shivers).
Name some Fluoroquinolones examples
Enrofloxacin and ciprofloxacin
Marbofloxacin
Danofloxacin
Difloxacin
Orbifloxacin
What are ionophore antibiotics?
Ionophore antibiotics are fermentation products of different Streptomyces species and other fungi.
They are polyether antibiotics, which exert their antibiotic action by disrupting the transport of ions in the cell membranes.
Ionophores used to mainly be used for?
coccidiosis, especially in poultry
What is monensin?
is an ionophore antibiotic, trade name Rumensin.
packaged into slow-release capsules and administered to cows, straight into the rumen. reduces the amount of bacteria that produce lactic acid in order to prevent ketosis.
Narasin, salinomycin are both what?
ionophore antibitotics used for control of coccidiosis.
Nitrofurans are
A Broad-spectrum, bactericidal antibiotic class.
Relatively toxic, carcinogenic, teratogenic and mutagenic.
Examples are; Nitrofurazone, nitrofurantoin, furazolidone.
Prohibted for use in farm animals. In other animal species, use is limited to treatment of infections involving urinary and reproductive organs.
Examples of common nitromidazole class Ab are:
Metronidazole
Dimetridazole
Ronidazole
Tinidazole
Ipronidazole
Nitroimidazoles are
chemically similar to the AB class nitrofurans, acting on anaerobes, but are still their own class.
Are Broad-spectrum, bactericidal.
They are toxic and must not be used in farm animals.
Rifamycins are
a broad-spectrum, bactericidal AB class.
They inhibit RNA polymerase of the bacteria. They act on chlamydias and rickettsias.
They may lead to liver damage.
These should be left as reserve antibiotics.
Other broad spectrum antibiotics to note:
Carbadox
Fusidic acid
Isoniazid
Mupirocin
Methenamine
Novobiocin
Antifungal drugs
What is Amantadine?
an antiviral drug toward influenza virus.
used to treat dyskinesia associated with parkinsonism and influenza caused by type A influenzavirus, though its use for the latter is no longer recommended due to widespread drug resistance.
2 Antiviral drug Examples and what virus they work against
Acyclovir (herpesvirus)
Amantadine (influenzavirus)
Sulfonamides are
synthetic broad-spectrum bacteriostatic antibacterials but not technically “antibiotics”.
Antibiotics are typically derived from living organisms, whereas sulfonamides are chemically synthesized.
pharmacologically used as broad spectrum for the treatment of human and animal bacterial infections.
Mechanism of action of sulfonamides.
They inhibit the folic acid synthesis of bacteria, they prevent folic acid from being formed from para-aminobenzoic acid (PABA).
Pharmacokinetics of sulfonamides.
Absorption from the gastrointestinal tract is quick, distribution is good.
They bind to plasma proteins.
They are metabolised in the liver.
Resistance develops quickly.
Sulfonamides are ineffective in case of
pyogenic processes, an excess of folic acid occurs (pus contains a lot of folic acid) which bacteria can then utilize for growth and remember, the whole point of sulfonamides is to inhibit folic acid synthesis by bact. but if there’s too much substrate than they won’t work.
Sulfonamide Toxicity, Side effects
Allergic reactions
Urinary tract disorders (crystalluria, haematuria)
Most sensitive among animals are Doberman Pinscher dogs, it is recommended not to administer to them.
Diaminopyrimidines are
antimicrobial substances, The most common active Diaminopyrimidine substance being trimethoprim.
Sulfonamides and Diaminopyrimidines act how together?
in a synergistic manner, suppressing the bacterial synthesis of folic acid in two consecutive phases.
The Bactericidal effect of diaminopyrimidines thus occurs when administered in combination with sulfonamides.
eg.Sulfamethoxazole and trimethoprim combination
Diaminopyrimidine pharmokinetics and toxicity
They are absorbed and distributed well.
They are of a relatively low toxicity, side effects are rarely experienced.
Broad-spectrum antibiotics are typically reserve preparations (used if others are ineffective), may be used in case of
mixed infections, may be used in case of infections involving skin and reproductive organs.
Do not administer antibiotics simultaneously with? (3)
- do not administer multiple antibiotics simultaneously (unless proven combined infection)
- Do not combine active substances of one group or active substances of similar toxicity and side effects (two aminoglycosides).
- do not administer together with glucocorticoids (except e.g. topical preparations for pruritic infection)
Example of Natural Antimicrobial resistance
gram-negative microbes resistant to beta-lactams
Example of Obtained Antimicrobial resistance
bacterial chromosomal mutations
MRSA
methicillin-resistant staphylococcus aureus
MRS (methicillin-resistant staphylococci) are resistant to
cephalosporins,
carbapenems,
beta lactams (+ beta lactamase inhibitors).
Often multiresistant, resistant also to fluoroquinolones, aminoglycosides, tetracyclines etc.
What is the first choice AB in most cases.
penicillin
Typical AB choice for mastitis,
Streptococci, staphylococci B-neg?
Staphylococci B-pos ?
E. coli?
Streptococci, staphylococci B-neg – penicillin
Staphylococci B-pos – no AB (culling)
E. coli - no AB (fluid therapy, NSAID)
Hoof diseases should be treated with
local treatment, no systemic AB in most of cases.
Diarrhea in calves should first be treated with
electrolytes and NSAIDs.
In case of E. coli sulfa/trimethoprim, in the case of other pathogens (e.g. cryptosporidium) choose the appropriate treatment.
What classes of AB belong to broad-spectrum AB? (5)
Tetracyclines
Chloramphenicol, thiamphenicol and florfenicol
Fluoroquinolones
Ionophores
Rifamycins
Tetracyclineside effects specific to horses
Horses will experience diarrhoea and enterocolitis (it is not recommended to administer them systemically).
