Which type of bacteria produce more than 50% of the antibiotics?
a substance produced by a MO that inhibits another MO
What is the difference between bactericidal and bacteriostatic?
bactericidal kills bacteria, usually antibiotic of choice for infections in sites like endocardium or meninges where host defenses are ineffective.
bacteriostatic reversibly inhibits growth, duration of treatment is sufficient for host defenses to eradicate infection.
What are the 5 mechanisms of antimicrobial action?
1. inhibition of cell wall synthesis
2. disruption of cytoplasmic membrane
3. inhibition of protein synthesis
4. act as antimetabolites
5. inhibition of nucleic acid synthesis.
Which large group of antibiotics work by preventing synthesis of peptidoglycans (therefore inhibiting cell wall synthesis)?
4 important types of antibiotics work by inhibition of cell wall synthesis. Which 2 antibiotics have a beta lactam ring and which 2 do not?
penicillins and cephalosporins have a beta-lactam ring and bacitracin/vancomycin do NOT have beta-lactam ring.
What stucture do penicillins and cephalosporins have in common?
a beta-lactam ring
What type of bacteria do penicillins most effectively inhibit?
growing gram positive bacteria
How do penicillins specifically inhibit cell wall synthesis?
by inhibiting the cross-linking between the glycan molecules in the peptidoglycan by binding to transpeptidase.
What is the penicillin binding protein?
transpeptidase, the enzyme responsible for cross-linking glycan molecules in the peptidoglycan structure.
What does penicillinase do?
it breaks the beta-lactam ring in penicillin and we see antibiotic resistance to the penicillins. some bacteria can produce it. it is also called beta-lactamase.
What is clavulanic acid?
it does not have antibiotic effect by itself, it has a beta lactam ring in its own structure. it is a suicude inhibitor, covalently bonds to a serine residue on active site of beta-lactamase, restructures itself to become a much more reactive species. it can be attacked and permanently inactivated, restoring the antimicrobial activity of beta-lactam antibiotics against lactamase-secreting-resistant bacteria.
What is the first semisynthetic penicillin produced to evade penicillinase?
Which 3 semisynthetic penicillins are effective against gram pos and gram neg bacteria?
Later generations of cephalosporins are "broad spectum". What does this mean?
they are effective against more microbes. ex: Ceftiofur, a third generation cephalosporin is effective against gram pos and gram neg.
What is Isoniazid?
A synthetic antimicrobial compound, inhibits mycolic acid synthesis so used to treat Mycobacterium infections (like Tuberculosis and Johne's Disease)
What is vancomycin?
primarily effective against gram pos bacteria, inhibits cell wall synthesis by blocking cross links, used to treat MRSA infections. is a glycoprotein.
What is bacitracin used for in chicken, swine, and cattle?
growth promoter. and treatment of enteritis caused by Clostridium perfringens in swine and chicken.
What route of administration do you take for bacitracin and why?
topical use because it in nephrotoxic when administered parenterally.
What type of ribosome do bacteria have?
70S, composed of 50S and 30S subunits
Antibiotics that target bacterial ribosomes have what kind of spectrum of activity?
broad spectrum, except macrolides which only are effective against gram positive.
Which of the classes of antibiotics that inhibit bacterial protein synthesis are bactericidal while all others are bacteristatic?
the aminoglycosides are the only protein inhibiting antibiotics that are bactericidal, all others are bacteristatic.
How do tetracyclines act on the bacterial ribosome?
block the attachment of tRNA to the ribosome (on the 30S subunit).
How do aminoglycosides act on the bacterial ribosome?
block the initiation of translation and causes misreading of mRNA (on the 30S subunit).
How do macrolides act to inhibit bacterial protein synthesis?
prevent the continuation of protein synthesis.
How do lincosamides act to inhibit bacterial protein synthesis?
prevent the continuation of protein synthesis (act on the 50S subunit).
How does chloramphenicol act to inhibit bacterial protein synthesis?
prevents peptide bonds from being formed (acts on the 50S subunit).
Aminoglycosides are effective against which type of bacteria?
primarily effective against gram negative bacteria, require oxygen to transport into the cell so not effective against anaerobes.
Amikacin, Apramycin, Gentamicin, Kanamycin, Neomycin, Streptomycin, and Tobramycin are types of which class of drugs?
Aminoglycosides, they irreversibly inhibit protein synthesis by binding 30S ribosomal subunit and they are bactericidal.
What is the only Aminocyclitol used in veterinary medicine?
What is the difference between aminoglycoside and aminocyclitol?
aminoglycoside is bactericidal and aminocyclitol is bacteriostatic.
What is the structure of macrolides? How do they act?
they contain a macrocyclic lactone ring connected to sugar molecules. they prevent protein synthesis by reversibly binding to 50S ribosomal subunit.
What is the best known macrolide and its action?
erythromycin, it is bactericidal, effective against gram positive bacteria, and bacteria are often resistant (chromosome or plasmid mediated).
Azithromycin, Clarithomycin, and Tulathromycin are what class of drugs?
broad spectrum semisynthetic macrolides.
Tylosin is used to treat what condition in swine? Which 6 conditions in cattle? What type of bacteria does it act on?
treats and prevents swine dysentery. treats pneumonia, foot rot, pink eye, metritis, mastitis, and liver abscesses in cattle. it acts on gram positive bacteria, is broad spectrum, often see resistance, is bactericidal
What is the first broad spectrum antibiotic to be discovered?
What is the basic structure of tetracycline?
What kind of bacteria do tetracyclines work on?
gram positive and gram negative, mycoplasma, chlamydia, rickettsia
What is Tilmicosin?
semisynthetic macrolide, marketed as MycotilR, treats respiratory infections in cattle and swine, used as single dose prophylaxis in cattle on arrival to feedlot
Which antibiotic causes serious toxicity including aplastic anemia and neutropenia, and it is prohibited in food animals?
What types of bacteria are affected by chloramphenicol?
it is broad spectrum and treats gram pos and gram neg, also mycoplasma, chlamydia, and rickettsia.
What is the synthetic analog of chloramphenicol, with broad spectrum activity and similar action but less toxic?
MycotilR and NuflorR are two antibiotic drugs. Which is approved for treatment of respiratory infections in cattle and swine?
NuflorR is approved (is florfenicol and is the safer synthetic analog of MycotilR). MycotilR is not approved (it is chloramphenicol).
What is Pleuromutilins used for?
used exclusively in animals, mainly swine. active against anaerobes and mycoplasma.
What is the semisynthetic antibiotic derived from pleuromutilin? How does it act on bacteria? What 2 conditions does it treat in pigs?
tiamulin, inhibits protein synthesis by binding 50S ribosome, is bacteriostatic and acts against only a few aerobic gram neg bacteria. treats swine dysentery and porcine proliferative enteropathy.
What class of antibiotics do clindamycin, pirilimycin and lincomycin belong to? What class are they closely related to?
they are lincosamides, and are closely related to macrolides
Lincomycin is used to control what 3 conditions in swine?
controls swine dysentery, erysipelas, mycoplasmosis
What is the semisynthetic derivative of lincomycin that is mainly used in small animals to treat soft tissue infections caused by S. aureus?
Which antibiotic is active against gram positives and through intra-mammary infusion treats mastitis caused by Streptococci and Staphylococci?
What type of bacteria produce polymyxins?
There are different forms of Polymyxins: A,B,C,D,E. Which 2 are common?
B and E
Which class of antibiotics act to dirupt the cytoplasmic membrane?
Which class of antibiotic are "detergent like", at lower doses bind endotoxin, are bacteriocidal, effective against gram negative, and used in equine colic?
How do Rifamycins act as antibiotics?
they inhibit the synthesis of mRNA, effective against gram pos bacteria, they are bactericidal.
Which antibiotic has the ability to penetrate tissues and encapsulated abscesses, used to treat tuberculosis and leprosy, used in Rhodococcus equi infections in horses? It works by inhibiting DNA-dependent RNA polymerase, binds its beta-subunit preventing transcription to RNA, inhibits gram pos bacteria.
How does Novobiocin act as an antibiotic?
inhibits DNA gyrase (enzyme involved in DNA supercoiling), effective against S. aureus, most gram neg are resistant.
Novobiocin is most often used in conjunction with which other antibiotic?
What was the first quinolone?
Which antibiotics are totally synthetic, effective only against gram negative, and nalidixic acid was the first one produced?
Which quinolone is used to treat bovine respiratory disease?
difloxacin, marbofloxacin and orbifloxacin are used in small animals and belong to which class of antibiotics?
How do fluoroquinolones act as antibiotics?
have broad spectrum activity on both gram pos and gram neg, act by inhibiting DNA gyrase (topoisomerase II), prevent DNA supercoiling. these are bactericidal antibiotics.
What was the first quinolone marketed exclusively for animal use?
Baytril R (Enrofloxacin), approved for treating GIT, soft tissue, and resp infections, and to treat bovine resp disease.
Which drug was banned in 2005 for use in chickens and turkeys because of concern with Campylobacter becoming resistant?
Enrofloxacin (a quinolone)
Which antibiotic is the quinoxaline NN dioxide derivative, used for growth production in swine, and prevention of swine dysentery and proliferative enteritis.
Which were the first synthetic antimicrobial agents used to treat bacterial infections?
sulfa drugs - bacteriocidal or bacteriostatic?
How do sulfonamides act as antibiotics?
they act as anti-metabolites, are a structural analog of PABA, prevent folic acid snthesis,
What are the 2 reasons that mammals and bacteria alike need folic acid?
1. nucleic acid synthesis (converted into purines and thymidine)
2. protein synthesis (precursor of AA's methionin and glycine)
How to bacteria obtain folic acid versus how do mammals obtain it?
bacteria synthesize it using PABA, while humans have to ingest it.
What is the advantage of narrow spectrum antibiotics.
Which 3 classes of antibiotics work against gram positive bacteria?
chloramphenicol, fluoroquinolone, and tetracycline
What 4 reasons may we need to combine antibiotics for treatment?
1. poly-microbial infections
2. serious infections
3. overcome destruction of antibiotics
4. decrease toxicity
When you combine penicillins and aminoglycosides, what is the result?
synergism, penicillin inhibits cell wall synthesis and aminoglycosides are allowed to enter bacterium and inhibit protein synthesis.
When you combine penicillins with bacteriostatic drugs, what is the result?
antagonism because cell wall synthesis is not occuring in cells that are not growing.
What are the 4 ways that antimicrobial resistance can develop?
1. modify the target
2. destroy or inactivate the antibiotic
3. develop resistant biochemical pathway
4. pump out the antibiotic from the cell
Which medium do you use for susceptibility testing (zones of inhibition)?
What is MIC?
minimum inhibitory concentration
What is MBC?
minimum bactericidal concentration
What are the 5 components of an infectious disease? (to be an infectious disease it must have at least 2 of these components).
3. localized inflammation
4. radiographic evidence
5. elevated serum fibrinogen