Antibiotics and Bacterial Genetics

Flashcards about Antibiotics, Antibiotic Resistance, and Bacterial Genetics

Ideal antimicrobial compound

Toxic to microbes without toxicity to host cells/organism, microbicidal, soluble and potent enough to function at low concentrations in tissues, long-enough acting to be functional, avoids antimicrobial resistance development, works together with host activities/host defenses, active in tissues or blood, readily transported to infected areas, affordable, and does not disrupt the host’s health

Antibiotics that inhibit cell wall synthesis

Penicillins, cephalosporins, bacitracin, vancomycin

Antibiotics that inhibit protein synthesis

Chloramphenicol, erythryomycin, tetracyclines, streptomycin

Antibiotics that inhibit nucleic acid replication and transcription

Quinolones, rifampin

Antibiotics that cause injury to plasma membrane

Polymyxin B, daptomycin

Antibiotics that inhibit essential metabolite synthesis

Sulfanimide, trimethoprim

Antimicrobials

Target any microorganism

Antibiotics

Target bacteria

Penicillin and cephalosporin

Block synthesis of peptidoglycan cross links; DD-transpeptidase is inhibited, causing the cell wall to lyse if the cells are actively growing/ remodeling

Semisynthetic penicillins

Ampicillin, amoxicillin, methicillin, oxacillin, carbenicillin

Most important natural forms of penicillins

Penicillin G and Penicillin V

Cephalosporins

Effective against gram-pos and gram-neg infections; Resistant to penicillinases and less allergenic than penicillin

Vancomycin

Used in treatment of Gram-positive infections ONLY! Narrow-spectrum, effective against penicillin & methicillin resistant staphylococcal infections, & C. diff infections; relatively toxic, requires intravenous administration

Aminoglycosides

Streptomycin, gentamicin, amikacin, neomycin, tobramycin, kanamycin

Tetracyclines

Tetracycline, doxycline, minocycline

Macrolides

Erythromycin, azithromycin, clarithyromycin

Quinolones and fluoroquinolones

Ciprofloxacin, norfloxacin, nalidixic acid

Rifamycins

Rifampin (a.k.a. rifampicin)

Lipopeptides

Daptomycin, Polymyxin B, Colistin (Polymyxin E)

Alteration of antibiotic target

Mutation in ribosomes, gyrase, penicillin-binding proteins

Enzymatic destruction or inactivation of drug

B-lactamases

Reduction of penetration of drug

Mutation or downregulation of expression of outer membrane Porins

Efflux of antibiotic

Broad substrate efflux pumps like AcrAB-TolC ; Specific substrate pumps like TetA

Classes of beta-lactamases

Ambler classes A, C, and D are serine type; Ambler class B are metalloproteases

Types of ESBLs

SHV, CTX, TEM, and OXA

Clavulanic acid

Inhibitor of beta-lactamases and is often administered with beta-lactam antibiotics to improve their efficacy.

Vertical gene transfer

Genes passed down through generations

Horizontal gene transfer

Exchange of genetic material between members of the same generation

Generalized recombination

Requires that the two recombining molecules have a considerable stretch of homologous DNA sequences

Site-specific recombination

Requires very little sequence homology between the recombining DNA molecules, but it does require a short sequence recognized by the recombination enzyme

Transformation

Transfer of “naked” DNA

Transduction

Transfer for genes via bacteriophage

Conjugation

Transfer of plasmids between bacteria

Hfr formation

Acquisition of chromosomal genes onto plasmids

Transformation

Process of importing free DNA into bacterial cells

Conjugation

Transfer of DNA from one bacterium to another, following cell-to-cell contact

Plasmids

Extra chromosomal DNA molecules that carry nonessential (for life) genes

Hfr cell

Capable of transferring chromosome parts into a recipient cell

F′ factor or F′ plasmid

Carries chromosomal genes

Transduction

Process in which bacteriophages carry host DNA from one cell to another

Generalized transduction

Can transfer any gene from a donor to a recipient cell

Specialized transduction

Can transfer only a few closely linked genes between cells