| Talk about cell wall synthesis inhibitor antibiotics. | They are selective only for bacteria, since human cells have no cell walls, so we are giving our bodies advantage however they may have side effects by acting on normal flora |
| Talk about the beta lactams. | All four families of beta lactams have a ring in common between them, three out of them have 2 rings (one common and another one) only monobactams have one ring.
They are cell wall inhibitors. |
| Talk about the cell wall inhibition role done by beta lactams. | Transpeptidase is an enzyme that attaches two molecules of glycoproteins through the D-alanine amino acid, making the cell wall.
However this transpeptidase is also a Penicillin binding protein (receptor of betta lactams) which destroy its activity and thus destroys cell wall.
So beta lactams are bactericidal |
| How do we deal with people sensitive to antibiotics (beta lactams)? | We should ask pxs if they have any allergies to medications, if they say that they are allergic to penicillin for example, they may be also allergic to other beta lactams.
So we ask them about the type of allergy, is it a rash or anaphylaxis, if its a rash, we can use other beta lactams, if anaphylaxis, we should not use beta lactams at all |
| What is an anaphylactic shock? | 90% similar to septic shock, but in septic shock the heart stops pumping
because the vessels are dilated not allowing the blood to come back to the heart because of
bacteria, therefore anaphylactic shock happened from taking antibiotics which induce this
allergy and causing the symptom |
| Are beta lactams natural or synthetic? | Some are natural by microbes and other are synthetic (in labs) |
| Talk about penicillin G. | is the first line, and it is a narrow spectrum, and it is given parenterally, mostly
against Gram+ bacteria (example: in IV, intramuscular or subcutaneous). We can add a benzene
ring to penicillin G benzathine penicillin, this give the penicillin a longer half-life (benzene
ring is stable) so half-life of the medication will last longer.
We use benzathine penicillin in very important infections (example: effective in treating
syphilis) |
| Why is penicillin G effective for syphillis? | Since syphillis has no transposons, so it doesn't acquire immunity against penicillin so penicillin G is very effective on it however benzathine penicilline is most effective |
| How did bacteria gain resistance against penicillin G? | Due to the overuse of penicillin G on staph aureus and skin infections, they gained plasmid mediated resistance agianst it when they started synthesizing beta lactamases.
So beta lactamases are virulence factors. |
| Talk about oxacillin and methicillin. | They were antibiotics that were stronger than penicillin G and replaced it, however today we don't use methicillin since it is harmful to humans and bacteria became resistant to them as well |
| What is MRSA? | methicillin resistant staph aureus, they are scary pathogenic agents to humans. |
| What are the broad spectrum types of penicillin antibiotics? | Through synthetic chemical modifications, scientists made antibiotics for gram + and -.
Ampicillin, Ticarcillin, Amoxicillin and Clavulanic acid (together make Augmentin) |
| Talk about Ampicillin. | wide spectrum coverage, but it is also sensitive to beta lactamase. Therefore,
similar to the effectiveness of penicillin G but can be used for Gram- as well |
| Talk about Ticarcillin. | Gram +and- as well as pseudomonas |
| Talk about Amoxicillin. | (the trademark of which is Augmentin): is a stronger antibiotic than ampicillin. To
overcome beta lactamase, obtained coverage of anaerobes as well after adding clavulanic acid |
| Talk about Clavulanic acid. | suicide inhibitor (Let’s say I have one molecule of amoxicillin and attached to it
a few molecules of clavulanic acid which have a similar structure. The incoming bacteria which
are supposed to face this combination will start to destroy the clavulanic acid first. It distracts
them until amoxicillin starts antimicrobial activity. It is like they commit suicide to help
amoxicillin do its job)
N.B: clavulanic acid alone doesn't do anything |
| Talk about Cephalosporins. | They which are used more in the market currently. It has four generations.
A medication from the first generation has more coverage of gram (+) than gram (-).
Going to the 2nd and 3rd, they start targeting gram (-) more.
4th generation: special for Pseudomonas.
5th generation: special for MRSA |
| Talk about Carbapenems. | They have a Carbon core instead of sulfur core. (However, Penicillins and Cephalosporins have
sulfur core instead of the carbon one). They are extreme broad-spectrum antibiotics.
Example: Imipenem, Meropenem |
| Talk about carbapenems resistance. | They are resistant to beta lactamase: the bacteria that secretes beta lactamase to destroy beta
lactam can destroy Penicillin G but cannot destroy Carbapenems
We have a newly emerging type of resistance which is a bacterium that secretes
Carbapenemase (an enzyme coded by a resistant gene to Carbapenems). |
| Talk about monobactams. | A synthetic antibiotic that has a single ring.
Example: Aztreonam.
Does not have a broad-spectrum since it only works on gram (-) |
| List polypeptide antibiotic cell wall inhibitors. | Vancomycin, Bactracin, and cycloserine |
| Talk about Vancomycin. | binds D-Alanine-D-Alanine to prevent corporation of subunit into growing
peptidoglycan. Too big to pass through the outer membrane so it only works on the gram+
bacteria and we consider it a huge molecule. |
| Talk about Bactracin | prevents dephosphorylation of phospholipid carrier, works on gram+ bacteria. |
| Talk about Cycloserine. | prevents dephosphorylation of phospholipid carrier, works on gram+ bacteria. |
| List protein synthesis inhibitors. | Chloramphenicol and macrolides, Aminoglycosides:, Tetracyclines |
| Talk about Chloramphenicol and macrolides | : they bind to 50S ribosomal subunit and prevent peptide
formation thus stopping protein synthesis |
| Talk about Aminoglycosides | they bind to the 30S ribosomal subunit and impair proofreading, resulting in
production of faulty proteins |
| Talk about tetracyclins. | they bind also to the 30S ribosomal subunit and block the binding of tRNAs,
thereby inhibiting protein synthesis. |
| What does PRT mean? | Parenteral (in intestine IV) |
| What does PO mean? | Per Os (enteral) |
| What does IM mean? | intramuscular |
| What does IV mean? | Intravenous |
| What does SC mean? | sub-cutaneous |
| Name some macrolide antibiotics. | Erythromycin (Legionella pneumophila, Mycoplasma pneumoniae)
Azithromycin (used in sexually transmitted infections to treat mycoplasma and chlamydia),
Clarithromycin
Ketolides: telithromycin (broader spectrum – toxicity) |
| Talk about Clarithromycin. | Type of macrolide, used in STIs (along with ceftiaxone for gonorrhea)
Empirical treatment (chlamydia and gonorrhea- bacteriostatic) |
| Name some aminoglycosides. | Streptomycin: not given alone, ototoxic (have huge side effect on ears that is usually
reversable) but can be used in Tuberculosis as second line. It’s not usable anymore in
hospitals
Gentamicin: aerobic gram negative & positive – parenteral, not given alone.
bind to 30S and aerobic conditions. |
| Give properties of tetracyclins. | Mostly PO or Topical (not injectable), broad spectrum and can cause superinfections. Intracellular (work on protein synthesis), natural type is called tetracyclin, synthetic one is Doxycyclin (for acne given in winter to avoid sunlight), Minocyclin (acne)
They inhibit 30S prevent tRNA from binding and may give deposits on bone tissues, causing teeth discolorization for young children so we don't give them, it is also contraindicated for pregnancy and bacteriostatic. |
| How do we prescribe Aminoglycosides nowadays? | These days we give Gentamicin, but again we do not give it on its own we give a course of
antibiotics and one shot or one dose of Gentamicin. It works on aerobic gram + and grambacteria |
| Talk about Chloramphinecol. | works on protein synthesis: inhibits the 50S ribosomal subunit. We don’t use
it anymore because it causes a very severe type of anemia: bone marrow suppressed anemia
that we call aplastic anemia |
| Talk about Clindamycin | a very important antibiotic these days because it can act on staphylococcus which
we said that it has resistance on penicillin and resistance on methicillin so we’re trying to find
newer drugs to fight this MRSA and so I have one option to give clindamycin and a second
option we mentioned earlier is to give Vancomycin. |
| Why is clindamycin important when treating MRSA? | A patient had a skin infection of MRSA and I want to treat it, the Clindamycin is given
Per OS but Vancomycin is given IV intravenously (= hospitalization so in this case there are risks
of infections in the hospital: possible complications that could happen after admission. This is
why clindamycin is an important antibiotic that we use in treating MRSA) |
| Talk about Metronidazole. | known as Flagyl, is a bactericidal antibiotic works on anaerobic conditions.
(There is over prescription of it in Lebanon, but its indication is very few)
known as Flagyl, is a bactericidal antibiotic works on anaerobic conditions.
(There is over prescription of it in Lebanon, but its indication is very few) |
| List cell membrane inhibitor antibiotics. | Daptomycin, Polymyxin B |
| Talk about Daptomycin. | which is also effective against MRSA (methicillin resistant staphylococcus aureus)
and VRE (vancomycin resistant enterococci). |
| Talk about polymyxin | works on the cell membrane, so it is a cell membrane inhibitor (the mechanism is
shown |
| List some nucleic acid inhibitors. | Rifamycin, Quinolones, Fluoroquinolones, Nalidixic acid, Ciproflaxacin |
| Talk about Rifamycin | are extracted of certain type of mycelium (Mycota) so these inhibit the
mRNA synthesis and they are important in medicine because they can reach the central
nervous system, they can go to the CSF as medications and can penetrate thick walls of
abscesses and they can invade the biofilms so Rifamycin is given with other antibiotics to treat
germs that are living in biofilms or any place that is hard to access like abscesses |
| What are the side effects of Rifamycin? | The side effect is that it may cause urine that is colored orange to red and its one of the
treatments of tuberculosis |
| Talk about Quinolones | are given for urinary tract infections (UTI) and pneumonias |
| Talk about Nalixidic acid | is one of the first nucleic acid inhibitors quinolones in the 80s, they even used it
as an antibiotic disc in the lab to see if the bacteria are resistant to quinolones or not. |
| Talk about Ciproflaxin | known as the Estecina medication (the girls mostly should know it since it’s given
for repetitive UTI however, we do not give it to the simple UTIs female usually have) |
| What are the most unnecessarily prescribed antibiotics? | Ciprofloxacin, Augmentin and Flagyl (metronidazole) : are given most of the time
unnecessarily. |
| List some metabolic pathway inhibitor antibiotics. | Sulfa drugs, Bactrim, |
| Talk about sulfa drugs. | were the first drugs used in the 30s as antibiotics. They work on the metabolic
pathway, they transform a molecule PABA to folic acid or tetra-hydro folic acid.
We take our own folic acid from food (vitamin B9) but bacteria can synthesize its own folic acid
by a multi-step process.
The Sulfonamide work on one of the steps and another drug: Trimethoprim works on another
enzyme |
| Talk about the Bactrim. | (=Trimethoprim + sulfamethoxazole) can be used in simple UTI infection but also as
prophylactic antibiotic in other casesBactrim is anti-microbial: it does not only works on bacteria but also on parasites but never on
viruses. |
| Give an example in usage of bactrim. | when someone is diagnosed in HIV and we found that he developed AIDS and the
CD4 level is low ,in order to prevent any fungal or bacterial infection we give Bactrim as
prophylaxis. |
| Give an example on a guideline of prescribing antibiotics. | At first an STI (sexually transmitted infection) patient was given 1 injection of Ceftriaxone
(Cephalosporin) + 1g of azithromycin for once but in 2021 a new recommendation reclaims that
in STI we give the injection of ceftriaxone but now we give with it Doxycycline 100mg twice a
day for 7 days. |
| List some misuses of drugs. | Getting antibiotics without a perscription, mothers know better than doctors, allergies caused by antibiotics, stopping antibiotics intake before the prescribed period leading to resistance acquisition, usage in animals in USA to enhance milk... |
| What is opsonin? | Molecule attaches to antigen and macrophage to initiate phagocytosis. |
| What are anaphylatoxins? | Fragments of proteins causing a complement cascade (vascular permeability and chemotaxis) |
| What are complements? | Proteins that mediate attachment of antigen antibody complex |
| List some antibiotics that work on gram+ bacteria. | Bacitracin and vancomycin and cycloserine |
| Does flagyl work in a classical way? | No, works on anaerobes (in colon). |
