Antibiotics and Their Uses

Imipenem is a broad-spectrum antibiotic effective against a wide range of bacteria, including Gram-positive, Gram-negative, Pseudomonas aeruginosa, and Enterococcus species. However, it is easily broken down by an enzyme in the kidney, so it is always administered with cilastatin, a dehydropeptidase inhibitor.

Meropenem is a broad-spectrum antibiotic similar to imipenem, but it is not associated with seizures and can be administered by bolus injection or infusion. Because of its higher solubility, it can be given to patients with fluid restrictions and is suitable for outpatient use.

Ertapenem is also a carbapenem antibiotic, but it is not effective against Pseudomonas aeruginosa. This is a key difference compared to imipenem and meropenem.

Monobactams, such as aztreonam, are a class of antibiotics distinct from other beta-lactams. They have a unique structure, lacking the fused ring found in other beta-lactams, but share the same mechanism of action.

Aztreonam is the only commercially available monobactam antibiotic. It is highly effective against Gram-negative bacteria, including Pseudomonas aeruginosa, but it is not effective against Gram-positive bacteria or anaerobes.

Glycopeptides are a class of antibiotics that include vancomycin and teicoplanin. They are bulky molecules that are effective against Gram-positive bacteria but cannot penetrate the outer membrane of Gram-negative bacteria.

Vancomycin is a glycopeptide antibiotic effective against Gram-positive bacteria. Teicoplanin is another glycopeptide with a similar spectrum of activity to vancomycin.

Teicoplanin is another glycopeptide antibiotic, similar to vancomycin. It is effective against Gram-positive bacteria and is administered intravenously or intramuscularly.

Teicoplanin is a glycopeptide antibiotic that inhibits bacterial cell wall synthesis by binding to D-Ala-D-Ala terminus of peptidoglycan polypeptide, preventing further elongation and cross-linking.

A powerful antibiotic used against staph infections. It is sometimes used as a

Teicoplanin has a longer plasma half-life and protein binding than vancomycin, resulting in a reduced propensity for adverse reactions.

Teicoplanin can be administered by intramuscular injection unlike vancomycin.

Fosfomycin is a broad-spectrum antibiotic effective against various Gram-positive and Gram-negative bacteria, including MRSA, VRE, and E. coli.

Fosfomycin has a rapid bactericidal effect, meaning it quickly kills bacteria.

Fosfomycin is produced by certain Streptomyces species, making it a naturally derived antibiotic.

Bacitracin is a mixture of polypeptides isolated from Bacillus subtilis. It is mainly used topically against Gram-positive bacteria due to its serious nephrotoxicity.

A group of antibiotics that include gentamicin, tobramycin, amikacin, streptomycin, neomycin, and kanamycin. They are effective against a range of Gram-negative bacteria, including Pseudomonas, Serratia, and Enterobacter. However, they can cause serious side effects like nephrotoxicity and ototoxicity. They are mainly used for severe infections like pneumonia and sepsis.

Streptomycin, gentamicin, tobramycin, and amikacin are all aminoglycosides used to treat serious Gram-negative infections like those caused by Pseudomonas, Serratia, and Enterobacter. However, they are not used for systemic infections due to their toxicities. Gentamicin and tobramycin are effective against Pseudomonas, while amikacin is the most potent of the four. Streptomycin is often used for tuberculosis.

Neomycin is not used for systemic infections because of its toxicity. It is often used in bowel surgery preparation for its effect on gut bacteria. A high dose is given orally just before surgery.

The main uses of aminoglycosides include treating respiratory infections acquired in hospitals, complicated urinary tract infections, infections in the abdomen, and bone infections caused by Gram-negative bacteria. These infections are often serious and occur in hospitalized patients.

Tetracyclines are a group of broad spectrum antibiotics that include tetracycline, oxytetracycline, doxycycline, minocycline, and tigecycline. These antibiotics are bacteriostatic, meaning they stop bacteria from multiplying. They are effective against atypical bacteria like Mycoplasma and Chlamydia, but they are not effective against certain Gram-positive bacteria (like S. pyogenes) or some Gram-negative bacteria (like P. aeruginosa).

Spectinomycin is an antibiotic that is used occasionally to treat gonorrhea. It is used mostly when patients are allergic to penicillin or the gonorrhea causing bacteria are resistant to penicillin. It's not a first-line treatment but a backup option.

Aminoglycosides can cause harm to the kidneys (nephrotoxicity) and the ears (ototoxicity). They can also increase the effects of muscle-relaxing drugs.

Tetracyclines are bacteriostatic antibiotics meaning they stop bacteria from multiplying but don't directly kill them. They have a broad spectrum of activity, targeting atypical bacteria like Mycoplasma and Chlamydia. They are also effective against some Gram-positive bacteria and some Gram-negative bacteria.

A group of antibiotics (e.g., erythromycin, azithromycin, clarithromycin) known for their effectiveness against Gram-positive bacteria, atypical bacteria (chlamydia, mycoplasma, spirochetes), and some Gram-negative bacteria (Legionella, Campylobacter, H. pylori).

Macrolides inhibit protein synthesis by binding to the P-site of the 50S ribosomal subunit, preventing the movement of t-RNA from the A-site to the P-site, effectively stopping the process of protein synthesis.

They are often used in cases where penicillin allergy exists, as an alternative for treating infections caused by group A streptococcus or pneumococcus.

Azithromycin, a macrolide, can penetrate cells easily and even reach the gingival crevicular fluid in teeth to treat periodontitis.

Azithromycin's long half-life allows for once-a-day dosing, making it convenient for patients.

Spiramycin, a macrolide, has proven effective in treating toxoplasmosis.

Gray baby syndrome, characterized by hypotension, cyanosis (bluish skin), and potentially death, is a serious side effect associated with chloramphenicol, an antibiotic.

Chloramphenicol is contraindicated for systemic use if another effective alternative exists due to potential risks. However, it remains widely used topically.

Doxycycline is a tetracycline antibiotic effective against MRSA. Its absorption is reduced by metallic cations like aluminum, calcium, magnesium, and iron, making simultaneous use with antacids or certain supplements problematic. However, food doesn't affect its absorption, unlike other tetracyclines. Doxycycline has a longer plasma half-life (16-18 hours) compared to other tetracyclines, and it is primarily excreted through the intestinal tract.

Tetracyclines interfere with bacterial protein synthesis by binding to the 30S ribosomal subunit at the A-site, blocking aminoacyl-tRNA from attaching. This inhibits bacterial growth.

Tetracycline use can lead to 'superinfection,' where normal flora in the body is disrupted, causing yeast infections, skin rashes, and other infections. Photosensitivity is another side effect, so minimizing sun exposure is crucial.

Teeth discoloration, a common side effect of tetracyclines, is due to their affinity for calcium, leading to the formation of tetracycline-calcium orthophosphate complexes in developing teeth. This causes a yellowish hue in teeth.

Tetracyclines are contraindicated in patients with allergies to tetracyclines, renal insufficiency (except doxycycline), during pregnancy, and in children under a certain age.

Tigecycline is a glycylcycline antibiotic related to tetracyclines. It has a broader spectrum of activity than traditional tetracyclines, including activity against anaerobic bacteria, atypical bacteria, MRSA, S. pyogenes, and most Gram-positive and Gram-negative bacteria.

Tigecycline overcomes two main mechanisms of bacterial resistance to tetracyclines: drug-specific efflux pumps and ribosomal protection.

Tigecycline is the first glycylcycline approved by the FDA and is administered intravenously.

Tetracyclines are a broad class of antibiotics known for their effectiveness against bacterial infections. They work by inhibiting bacterial protein synthesis, which is vital for their survival. However, they can also cause adverse effects, particularly tooth discoloration, if used during tooth development.

Eravacycline and Omadacycline are newer tetracycline antibiotics designed to overcome common antibiotic resistance mechanisms. Resistance mechanisms like ribosomal protection and active drug efflux are commonly encountered in bacteria, making it challenging to effectively treat infections. Eravacycline and Omadacycline attempt to overcome these challenges, expanding their spectrum of activity.

Chloramphenicol is an antibiotic with a broad spectrum of activity, capable of killing both Gram-positive and Gram-negative bacteria. It is unique in its ability to penetrate human cells, making it effective against intracellular bacteria. However, its use is limited due to its potential for serious side effects, including bone marrow suppression which can be fatal.

Chloramphenicol's mechanism of action involves inhibiting peptidyl transferase, a key enzyme responsible for protein synthesis within bacteria. By blocking this enzyme, chloramphenicol prevents bacterial cells from creating essential proteins, ultimately leading to their demise.

Chloramphenicol's most severe adverse effect is bone marrow depression, which can lead to a life-threatening condition called aplastic anemia. This condition impairs the bone marrow's ability to produce sufficient blood cells, leading to anemia and other complications.

50S ribosomal subunit inhibitors are a class of antibiotics that target the 50S ribosomal subunit, which is critical for protein synthesis in bacteria. By inhibiting the activity of this subunit, these antibiotics effectively disrupt the process of bacterial protein synthesis.

Gram-positive bacteria have a thick peptidoglycan layer in their cell wall, which makes them susceptible to drugs that target this layer. Drugs like vancomycin and teicoplanin are examples of glycopeptides that effectively target peptidoglycan synthesis in Gram-positive bacteria.