#antibacterials

[biomedicool]

Antimicrobial Agents - Inhibition of DNA and Protein Synthesis

Bacterial chromosome replication

DNA replication

Bacterial Topoisomerases 

maintain DNA in appropriate state of supercoiling 

cut and reseal DNA

DNA gyrase (topoisomerase II) introduces negative supercoils 

Topoisomerase IV decatenates circular chromosomes 

these are the targets of the quinolone antibacterial agents 

Quinolones

bind to bacterial DNA gyrase and topoisomerase IV after DNA strand breakage 

prevent resealing of DNA 

disrupt DNA replication and repair 

bactericidal (kill bacteria)

Fluoroquinolone is particularly useful against

Gram +ves: Staphylococcus aureus, streptococci 

Gram -ves: Enterobacteriacea; Pseudomonas aeruginosa 

Anaerobes: e.g. Bacteroides fragilis 

many applications e.g. UTIs, prostatitis, gastroenteritis, STIs 

Adverse effects

Relatively well tolerated

GI upset in ~ 5% of patients 

allergic reactions (rash, photosensitivity) in 1 - 2% of patients 

Inhibition of Bacterial Protein Synthesis 

Macrolides 

in 1952: Erythromycin was isolated as the first macrolide (Streptomyces erythreus) 

Newer macrolides: clarithromycin, azithromycin 

Structurally they consist of a lactone ring (14- to 16-membered) + two attached deoxy sugars 

Mode of action 

bind reversibly to bacterial 50S ribosomal subunit 

causes growing peptide chain to dissociate from ribosome → inhibiting protein synthesis 

bacteriostatic (stops reproduction)

Macrolides’ spectrum of activity

good antistaphylococcal and antistreptococcal activity 

treatment of respiratory & soft tissue infections and sensitive intracellular pathogens • e.g. Chlamydia, Legionella 

Adverse effects

Generally well tolerated

nausea 

vomiting 

diarrhoea 

rash 

Aminoglycosides

large family of antibiotics produced by various species of Streptomyces ("mycin") and Micromonospora ("micin") 

include: streptomycin, neomycin, kanamycin, gentamicins, tobramycin 

Structure = linked ring system composed of aminosugars and an aminosubstituted cyclic polyalcohol 

Mode of action of aminoglycosides

Bind irreversibly to 30S ribosomal subunit 

disrupt elongation of nascent peptide chain 

translational inaccuracy → defective proteins 

bactericidal 

Spectrum of activity 

broad spectrum; mainly aerobic G-ve bacilli (e.g. P. aeruginosa) 

used to treat serious nosocomial infections (hospital acquired infections)

First TB antibiotic

Used for cystic fibrosis 

Adverse effects

all aminoglycosides have low Therapeutic Index (only a small amount needed to become toxic)

renal damage, ototoxicity, loss of balance, nausea 

[scholarshipportal]

(via Antibacterial Medications – Types, Mechanism, Uses, and Adverse Effects)

[scholarshipportal]

(via Topical Antibacterials – Mechanism, Uses & Examples)

[scientificinquirer-blog]

DAILY DOSE: NASA Revises Costly Mars Sample Return Strategy; Getting Off Obesity Drugs Isn't So Great.

NASA SEEKS NEW PLANS FOR MARS SAMPLE RETURN. NASA is revising its Mars Sample Return (MSR) strategy to retrieve samples collected by the Perseverance rover on Mars, as escalating costs and delays have made the original plan untenable. Initially projected to cost between $2.5 and $3 billion, an independent review now estimates the cost at $11 billion, with a return not expected until 2040—delays…

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[scientificinquirer-blog]

A quick new way to screen virus proteins for antibiotic properties.

HAVE YOUR SAY.Join us in The Bullpen, where the members of the Scientific Inquirer community get to shape the site’s editorial decision making. We’ll be discussing people and companies to profile on the site. On Wednesday, March 22 at 5:30pm EST, join us on Discord and let’s build the best Scientific Inquirer possible. As conventional antibiotics continue to lose effectiveness against evolving…

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[amcrasto]

FAROPENEM

  Molecular FormulaC12H15NO5SAverage mass285.316 Da Faropenem 7086 (+)-(5R,6S)-6-((1R)-1-Hydroxyethyl)-7-oxo-3-((2R)-tetrahydro-2-furyl)-4-thia-1-azabicyclo[3.2.0]hept-2-ene-2-carboxylic Acid(5R,6S)-6-[(1R)-1-Hydroxyethyl]-7-oxo-3-[(2R)-tetrahydro-2-furanyl]-4-thia-1-azabicyclo[3.2.0]hept-2-ene-2-carboxylic…

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[thescientificinquirer]

Baltic amber shown to have antibacterial properties.

Baltic amber shown to have antibacterial properties.

For centuries, people in Baltic nations have used ancient amber for medicinal purposes. Even today, infants are given amber necklaces that they chew to relieve teething pain, and people put pulverized amber in elixirs and ointments for its purported anti-inflammatory and anti-infective properties. Now, scientists have pinpointed compounds that help explain Baltic amber’s therapeutic effects and…

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[thescientificinquirer]

Novel facemask has antibacterial properties but antiviral is uncertain

Novel facemask has antibacterial properties but antiviral is uncertain

Face masks have become an important tool in fighting against the COVID-19 pandemic. However, improper use or disposal of masks may lead to “secondary transmission”. A research team from City University of Hong Kong (CityU) has successfully produced graphene masks with an anti-bacterial efficiency of 80%, which can be enhanced to almost 100% with exposure to sunlight for around 10 minutes. Initial…

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