Visual Learner Studios uses visual mnemonics to teach pharmacology fast and efficiently.

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In this video, we will be talking about antibiotics that act by inhibiting the synthesis of bacterial cell walls. This is the first of a three part series on antibiotics. One of the other videos will discuss antibiotics that inhibit protein synthesis and the last will discuss antibiotics that inhibit nucleic acid synthesis.

Now, before we get into what medications the characters represent, let’s talk a little about these medications.

So bacteria have a peptidoglycan cell wall, and most of these types of antibiotics will inhibit the formation of this wall through a betalactam ring in their molecular structure. This betalactam ring binds to transpeptidases, also known as penicillin binding proteins, thereby preventing the formation of cross links in the cell wall. As a result, an increased osmotic gradient forms between the inside and outside of the cell wall, leading to leakage and degradation of the cell content.

Clinically useful families of betalactam compounds include penicillins, cephalosporins, monobactams, and carbapenems. All of the medications we will be talking about today are betalactams, with one exception, which we will talk about in greater detail later in the video.

Unfortunately, some bacteria have evolved over time and are able to counter the effects of betalactam antibiotics through the production of betalactamase, which breaks down the betalactam ring structure in these drugs. When bacteria have this resistance, betalactamase resistant antibiotics or betalactamase inhibitors can be used.

Narrow spectrum penicillins cover mostly gram positive infections. There are two narrow spectrum penicillins in this picture: Benzylpenicillin and flucloxacillin.

There are two broad spectrum penicillins in this picture, which act on both gram+ve and gram ve bacterial groups: Ampchillin’ representing ampicillin. Ampchillin’, Ampicillin. And AnOxChillin’, amoxicillin. AnoxChillin’, amoxicillin.

Due to the possibility of betalactamase producing bacteria, certain betalactam antibiotics are often combined with betalactamase inhibitors. A common combination is amoxicillin with clavulanic acid, often called coamoxiclav.

There are two antipseudomonal penicillins in this picture: the tinycarchillin’ represents Ticarcillin. Tinycarchillin’, Ticarcillin. And the pipechillin’ represents, piperacillin. Pipechillin’, piperacillin.

An important note to keep in mind when prescribing or dispensing penicillins is that it is a common drug allergy, so its important to ask.

Let's move onto the cephalosporins. Cephalosporins are derived from a fungus class called Acremonium, (previously called Cephalosporium). There are considered 5 generations of cephalosporins. Each generation has different clinical efficacy against specific types of bacteria. Each newer generation has significantly greater Gramnegative antimicrobial properties than the preceding generation, and, in most cases, decreased activity against Grampositive organisms, except when it comes to the 4th and 5th generation cephalosporins, as they generally also have good gram +ve activity.

The cephalosporins are represented on the shelving unit with 4 shelves, each representing one of the first four generations of cephalosporins, and the poster above in on the wall which represents one of the 5th generation cephalosporins.

Examples of other important drugs that target bacterial cell walls include meropenem, aztreonam, and vancomycin. Meropenem and aztreonam are both betalactam antibiotics, so their mode of action is similar to penicillins and cephalosporins.

Vancomycin is a nonbeta lactam antibiotics that targets gram positive bacterial cell walls. It works by Inhibiting cell wall synthesis by binding to the terminal of the growing peptide chain during cell wall synthesis, resulting in inhibition of the transpeptidase preventing further elongation and crosslinking of the peptidoglycan matrix.

Vancomycin is extremely important as it treats infections such as MRSA, which produces lowaffinity penicillinbinding protein 2A (PBP2A), which confers crossresistance to most βlactams.

Alright folks, that’s it for this video. To learn more about visual mnemonics and antibiotics including mechanisms of action and side effects, please visit our website at visuallearner.net, happy studying!