12.23 Anti-Infective – Penicillins and Cephalosporins

Antibiotics. In this video, we’ll mainly cover the penicillins and cephalosporins. There are seven different kinds of antibiotics are being used right now. Penicillin, Cephalosporin, Tetracycline, Macrolides, Aminoglycosides, Fluroquinolone, and Sulfonamides. In this one we gonna focus on Penicillin and Cephalosporins because they are really closely related classes to each other, so, it would be much easier to learn them together.

Okay, so, mechanism of action of penicillin. So, this is bacteria, and in the bacteria, they have a penicillin binding protein receptors on their surfaces, right there, all of them. Now, the penicillin, what it does, it binds to the bacteria by the penicillin binding proteins and it weakens the cell wall. When it weakens the cell wall, all the water goes into the bacteria and destroy the, destroy the bacteria. Basically, destroy the DNA, RNA and all sort of things. That’s why, that’s the mechanism of action of penicillin killing bacteria. Now, you may have some questions, okay. Why doesn’t kill the human cell? I mean, bacteria cell can kill the human cell as well. However, the only reason it doesn’t do on a human cell, human cell do not have cell wall. Bacteria has the cell wall. Human do not have a cell wall. Human cells do not have a cell wall. That’s the reason. That’s how penicillin will kill the bacteria cell but will not kill the human cells.

Now, bacteria cells are a little bit smarter as well. So, what they will do, because when bacteria also recognize, okay, this penicillin is weakening my cell wall. So, what they will do, they will produce this beta-lactamase or also known as penicillinase enzyme. And what that enzyme will do, it will breaks the beta lactam ring in the penicillin which is this ring in the penicillin. And that’s the important ring in order to kill the bacteria. But now, bacteria produce this enzyme and it will kill this ring. The penicillin will be ineffective. That’s why when we call this bacteria are penicillin resistance. They are not gonna get killed by penicillin, that’s how they they will opt resistance. And also, like if you use this penicillin over and over and over, and that’s how this bacteria gets the resistance to penicillin. That’s why we prefer to change antibiotic very often so they do not get resistance to any antibiotic. Now, in order to increase the effectiveness of penicillin in this case, they add some agents. Like if you see, I have two example. Piperacillin tazobactam and amoxicillin clavulanate. Now, this second part, these agents, what they will do, they will destroy this enzyme, so when they destroy this enzyme, automatically, bacteria won’t be able to kill this penicillin. And when the bacteria won’t be able to kill penicillin, the effectiveness of penicillin antibiotic will increase. So, it will require lower dose as well. So, that’s why you may see sometime often with the penicillin antibiotic like Piperacillin tazobactam, now you may be wondering what the tazobactam is. Now, you know, like the tazobactam is really important in order to increase the effectiveness of penicillin since it kills the beta lactamase enzyme.

Alright. Let’s go on. Now, penicillin are used for Gram positive bacteria; Streptococci and Staphylococci. This is not really important to remember, just for information, why they are used and for which kind of bacterias they are used.

Now, they are divided in three different categories. The Penicillinase-resistant penicillins, so, these penicillins are not affected by the enzyme produced by the bacteria which destroys the penicillin. So, these are Nafcillin, Oxacllin, Dicloxacillin, Cloxacillin. So, these penicillin do not require any kind of like tazobatam or anything in order to prevent the breakdown.

The Broad Spectrum includes the Amoxicillin, Amoxicillin-Clavulanate (It’s kinda hard to pronounce), but that’s the one in order to prevent the breakdown of amoxicillin by the enzyme that bacteria produces. Ampicillin and Bacampicillin.

Extended Spectrum includes the Piperacillin, Carbenicillin, and Ticarcillin. So, I mean, these are really easy to recognize medication, all have a -cillin at the end of their name. But they are divided in this kind of categories.

Side effects. The side effects is basically the allergy from the penicillin. Fever, rash, pruritus, and the main side effects to remember for penicillin, they decrease the RBC, WBC, and platelets. So, they basically decrease all blood cells. That’s the main one to remember, often tested on the NCLEX as well.

Now, the next drug is we gonna talk about the class Cephalosporin. They are really closely related in structure and mechanism of actions, side effects, to the penicillins. Even like I think about their classes of sensitivity to the cephalosporin and penicillin as well. So, if a patient is allergic to penicillin, there are high chances they’ll be allergic to cephalosporins. Now, as vice versa as well. Like, if they are allergic to cephalosporin, they are gonna be, there are high chances that they are gonna be allergic to penicillins as well. So, that’s the thing to remember. Like, if you have a patient and they have penicillin allergy listed as the penicillin and the physician may accidentally prescribe this cephalosporins. So, you wanna question that order and ask physician, “Do you really wanna give the patient cephalosporin even though they are allergic to penicillin?” So, okay.

And, these are the examples of cephalosporins. First generation was the first one, like really old cephalosporin, for example, Cefazolin, Cephalexin, these are the common most often used cephalosporins. They are effective against Streptococci and Staphylococci. I meant the Second generation right there. So, this is not first generation. It’s Second generation cephalosporins includes these Cefaclor, Cefprozil, these are rarely used drugs right now. First and second generation. They are really potent than first generation but the resistance beta lactamase and effective against gram-negative.

Now, this is the one they often use. The third generation and the fourth generation. And if you’re working in a neuro ICU which I used to work, on neuro ICU, you’ll see these drugs often used because these third and fourth generation can cross the CSF and can go into the brain and entry the infection. So, that’s the one important to remember the third generation. And they’re actually broader spectrum and longer duration than first and second generation as well, and they are resistance to beta-lactamase as well. So, they do not get resistance to those bacterias really easily. And this is the fourth generation, I have seen this one used very very often in neuro ICU because they have even less side effects compared with the third generation as well and it can enter the CSF.

So, these are all the examples of cephalosporin. There are lot, but easy way to remember they all have a Cef- pretty much in the beginning. So, these cephalosporin examples.

Side effects is kinda same with the penicillin. Like, allergy, fever, rash, pruritus. Instead of decrease in all blood cells like as the penicillin does, this medication do not do those decrease in blood cells but they can have GI problems like a stomach pain, like a diarrhea, those kinds of stuff, those kind of complains. And this medication can cause kidney toxicity. So, you really wanna monitor the kidney function if a patient is on this antibiotic. You wanna monitor creatinine and BUN in order to make sure the kidney functions are good. And you do not wanna give any patient this medication if their kidney functions are impaired as well.

So, those are the side effects and contraindication. Those are the information about the penicillin and cephalosporins. If you have any questions, you can ask us, e-mail us. Thanks for watching.