Anti-infective medications Flashcards
What is bacteria?
Bacteria are single celled microscopic organisms that can be classified according to a number of different characteristics.
Cell wall:
Those with a simple cell wall are called gram positive bacteria
Those with a complex cell wall are termed gram negative bacteria.
Environment:
Aerobic bacteria are those that thrive in oxygen-rich environments (i.e. generally closer to the skin surface)
Anaerobic bacteria are those that proliferate in oxygen-poor environments (i.e. typically in deeper tissues of the body).
Shapes:
Spirilla: spiral-shaped bacteria
Bacilli: rod-shaped bacteria (termed bacilli)
Cocci: spherical-shaped bacteria.
To understand the mechanism of action of antibiotics, it is important to understand the differences between types of bacteria, particularly gram positive and gram negative bacteria.
What are viruses?
Viruses, unlike bacteria, are not cells. They comprise a nucleic acid molecule (DNA or RNA) encased in a protein coat (a capsid).
Viruses can only multiple within the living cells of a host.
The immune system responds to a virus by killing the cells invaded by that virus.
What is fungi?
Fungi are eukaryotic cells and contain membrane-bound nuclei, they include moulds and yeasts.
Fungi are commonly found in normal human flora.
Fungal cells are capable of releasing enzymes that cause topical infection characterised by localised redness.
If fungi invade the body systemically, they can be life-threatening.
Antibiotics
An antibiotic is an agent that can kill or inhibit the growth of bacteria so that the person’s immune system can then fight off the infection
Antibiotics are Schedule 4 medications (prescription only). There are many different types of antibiotics, including penicillins, cephalosporins, tetracyclines, macrolides, fluoroquinolones (or quinolones), sulfonamides and glycopeptides.
Bactericidal agents include
penicillins,
cephalosporins,
vancomycin.
Bacteriostatic agents include
tetracyclines
sulfonamides
macrolides
lincomycin
Four modes of action related to antibiotics
Inhibition of bacterial DNA synthesis (e.g. quinolones)
Inhibition of bacterial protein synthesis (e.g. tetracyclines, aminoglycosides and macrolides)
Inhibition of folate synthesis (e.g. sulfadiazine and trimethorpim)
Inhibition of bacterial cell wall synthesis (e.g. penicillins, cephalosporins and carbapenems).
narrow spectrum
are useful in treating infections caused by a relatively limited number of bacteria (e.g., only gram-positive organisms). The use of narrow spectrum agents may be desirable when the identity of the infecting pathogen, as well as its susceptibility to the action of the antibiotic, has been established.
broad spectrum
act on a wide variety of different bacteria. Broad-spectrum antimicrobial agents are useful in treating infections in which the identity and susceptibility of the infecting organism has not been established. The advantage to this is that there is an excellent likelihood that the broad spectrum medication will treat the infection; however, the downside is that the use of such broad-spectrum antibiotics in this way, is their ability to destroy the body’s normal microbial population
What are Antivirals?
When viruses invade a host cell, they use at least some of the host cell’s machinery to synthesize more of the viruses’ own DNA/RNA. As a result, it is challenging for drugs to destroy a virus without affecting the host cell. Thus, most antivirals (drugs aimed at eliminating viruses) try to target the differences between the nucleic acids or enzymes of viruses and those of the host cells
What are Antifungals
Antifungals (or antimycotics) are medicines used to treat fungal infections. Antifungals act by interfering with fungal cells in various ways including:
Disrupting the synthesis and integrity of the fungal cell membrane
Disrupting the synthesis and integrity of the fungal cell wall
Disrupting the fungal cell DNA transcription and translation
