3D - Antibiotics and Antibiotic Resistance Flashcards
Antimicrobial
antibiotics, antivirals, anthelminthics, antifungals
Antibiotic
active against bacteria
Bacteriostatic
inhibit growth
• Sulfonamides, Tetracycline,Chloramphenical
Bactericidal
Kill
• Penicillin, Aminoglycosides
◦ Streptomycin
◦ Gentamicin
three main methods of antibacterial action
◦ Disrupt bacterial cell wall biosynthesis
‣ penicillin, cephalosporins and vancomycin
◦ Interfere bacterial protein biosynthesis
‣ macrolides, tetracyclines and aminoglycosides
◦ Bacterial DNA replication
‣ fluoroquinolones
beta lactams are cell wall inhibitors
◦ Naturally made by fungal organisms
◦ Single most important group of antibiotics
◦ Block synthesis of peptidoglycan in the cell wall
‣ Penicillin
‣ Cephalosporin
Penicillins
narrow spectrum and are only effective against gram positive bacteria
◦ But other β lactam such as ampicillin and the cephlosporins are effective against gram – ve ’s
◦ Bacteria become resistant to B- Lactams by producing an enzyme that destroys the β lactam ring called B-lactamase
◦ Extended-spectrum β lactamases (ESBL) are enzymes that confer resistance to most beta-lactam antibiotics, including penicillins and cephalosporin = BAD NEWS
Streptomyces
target the ribosome and inhibit protein synthesis
Aminoglycosides
Type of Streptomyces
gentamicin, streptomycin, neomycin)
‣ Side-effects of nephrotoxicity and neurotoxicity
‣ Treatment for serious infections caused by aerobic gram-negative bacilli
Macrolides
Type of streptomyces
Erythromycin
‣ Broad spectrum
‣ Often used as a replacement for penicillin in patients that are allergic to penicillin
Tetracycline
a broad spectrum antibiotic also made from Streptomyces spp
◦ Bacteriostatic against nearly all gram +ve and –ve bacteria
◦ Targets the ribosome and is a protein synthesis inhibitor
◦ Tetracycline and penicillin are the most widely used ABs in both human and animal health.
◦ Used for growth promotion in the pig and poultry industries
‣ → Widespread acquired antibiotic resistance
‣ Some bacteria are innately resistant to certain antibiotics.
‣ For example, gram –ve bacteria are intrinsically resistant to Penicillins. However, of great concern is when previously susceptible bacteria “acquire” antibiotic resistance.
Sulfa drugs
growth factor analogs that block the synthesis of folic acid in bacteria
◦ Discovered in 1930 - very useful against streptococcal infection (gram +ve)
◦ Lots of resistance now
◦ Sometimes still effective if used in combination with trimethoprim, another growth factor analog that also interferes with folic acid synthesis– sequential interference in the folic acid synthesis pathway
‣ Sulfa drugs are safe for animals because animals get folic acid from their diet
enrofloxacin (Baytril)
A commonly used antibiotic in veterinary Its mechanism of action is not thoroughly understood, medicine
◦ Fluoroquinolone.
◦ Broad spectrum activity against Gram-ve and +ve bacteria.
◦ Inhibits DNA synthesis
Antibiotic resistance
◦ The adaptive response of a bacteria to resist the effect of an antibiotic so that it is not killed or It ’s growth is not inhibited.
◦ Antibiotic resistance occurs when the properties of a population of bacteria changes when it is exposed to antibiotics so that it is no longer susceptible to the antibiotic at therapeutic dose rates’ (WHO)
Antibiotics and Antibiotic resistance occur naturally in the environment
Survival mechanisms in a complex, competing environment
◦ Found in natural environments, clinical settings, in pathogenic as well as commensal microbial populations
