ANTIBIOTICS

Question 1

DEFINITION OF CHEMOTHERAPY AND PARASITE

Answer 1

CHEMOTHERAPY, synthetic chemicals that selectively destroy infective/pathogenic agents with little or no harm done to the host cells
PARASSITE, or pathogen any organism that causes disease

Question 2

FACTORS THAT INFLUENCE THE CHOICE OF CHEMOTERAPIC DRUG

Answer 2

• organism ad sensitivity
• site of infection
• safety
• patient status, newborns have undeveloped elimination processes nb chloramphenicol causes Grey baby syndrome
• cost
• resistance

Question 3

SITE OF ACTION OF ANTIBACTERIAL DRUGS

Answer 3

• CELL WALL
• METABOLIC SYNTHESIS INHIBITORS (enzymes that transcript DNA to RNA
• NUCLEIC ACID FUNCTION/SYNTHESIS
• PROTEIN SYNTHESIS
• CELL MEMBRANE FUNCTION

Question 4

CELL WALL SYNTHESIS INHIBITORS

MOA AND CLASSES

Answer 4

• the bacterial cell wall is unique to bacteria and it’s made of peptidoglycan, polymers of glycan units cross-linked by peptide bonds, antibacterial drugs interfere with the cross-linking of peptidoglycan weakening the cell wall
• beta-lactam antibiotics (penicillin, cephalosporin)
• vancomycin, teicoplanin

Question 5

characteristics of penicillins

Answer 5

• bactericidal, kill the bacteria
• only effective against rapidly dividing cells (active infection)
• 5% population manifest reactions from a mild rash to anaphylactic shock
• cross-sensitivity with cephalosporins

Question 6

types of penicillins

Answer 6

• natural penicillin, penicillin G, against gram +ve and -ve cocci, gram+ bacilli, spirochetes
• antistaphylococcal penicillins, synthetic form, beta-lactamase resistant, if MRSA use vancomycin
• extended-spectrum penicillins, same spectrum as penicillin g and gram - bacilli
• combination of penicillin and aminoglycosides

Question 7

characteristics of glycopeptide antibiotics

Answer 7

• vancomycin, inhibits the release of cell wall building block, bactericidal except streptococci, used for gram+ and MRSA
• teicoplanin, similar to vancomycin but longer lasting

Question 8

MOA OF FOLATE ANTAGONISTS

Answer 8

• target the production of folate by the bacteria
• di-hydrofolic acid is a nucleic acid precursor, the organisms to be susceptible need to have the PABA (p-aminobenzoic acid) precursor of folic acid.
• sulphonamides compete with PABA for the enzymatic site, trimethoprims block the dihydrofolate reductase that turns folic acid into tetrahydrofolic acid

Question 9

CLINICAL USE OF FOLATE ANTAGONISTS

Answer 9

• SOLPHONAMIDES used for chlamydia, pneumocystis and Nocardia, topically and systemically used for trachoma
• usually used in combination with trimethoprim→ co-trimoxazole
• co-trimoxazole used mainly for pneumocystis Carinii pneumonia, more effective than single drugs alone

Question 10

WAYS OF TARGETING BACTERIAL DNA

Answer 10

• inhibit synthesis of nucleotides
• altering base-pairing properties of template (intercalating agents)
• inhibit either DNA or RNA polymerase (enzyme that transcripts DNA into RNA)
• inhibit DNA gyrase (enzyme that unfolds and relaxes supercoils of DNA for the transcription)
• direct effect of DNA (alkylating agents)

Question 11

NAC OF METRONIDAZOLE

Answer 11

• NATURE, bactericidal,
• ACTION, binds to DNA preventing nucleic acid synthesis
• CONSEQUENCES/USES, drug of choice for sepsis by Bacteroids species, pseudomembranous colitis by Clostridia sp., oral infections by Fusobacterium sp.
• s/e inhibits alcohol levels in the plasma, nausea, vomiting, rashes

Question 12

NAC OF QUINOLONES AND EXAMPLES OF DRUGS IN THIS CATEGORY

Answer 12

• NATURE, bactericidal and broad spectrum
• ACTION, inhibit bacterial replication by interfering with DNA gyrase, affect DNA elix production, synergize effect with beta-lactams abx
• CONSEQUENCES/USES, ciprofloxacin* used for pseudomonas infections in cystic fibrosis, *norfloxacin* in UTI and prostatitis, *Ofloxacin, prostatitis by E.coli and STI.

Question 13

MOA OF INHIBITORS OF PROTEIN SYNTHESIS

Answer 13

• ABX that target bacterial ribosome structurally smaller than mammalian ribosome (70S with 50S &30S bacterial ribosome)
• selective toxicity but a high dose can interfere with host cells

Question 14

NATURE AND USES OF TRETRCYCLINE/DOXYCYCLINE/MINOCYCLINE

Answer 14

• broad-spectrum abx, used for cholera, Lyme disease, chlamydia venereal infections, mycoplasma pneumonia
• s/e teeth discoloration, hepatotoxic in pregnancy, GI upset

Question 15

NAC OF AMINOCLYCOSIDES

Answer 15

• gentamicin, streptomycin, tobramycin
• NATURE bactericidal
• ACTION, protein synthesis inhibitors
• CONSEQUENCES/USES unresponsive UTIs, tularemia, E.coli pneumonia, pseudomonas aeruginosa
• s/e ototoxicity, kidney damage

Question 16

NAC OF SODIUM FUSIDATE

Answer 16

• NATURE, protein synthesis inhibitor in bacteria
• ACTION, binds to subunit 50S
• CONSEQUENCES/USES, narrow spectrum, used for osteomyelitis, staph infections caused by penicillin-resistant organisms

Question 17

NAC OF LINEZOLID

Answer 17

• NATURE, protein synthesis inhibitor
• ACTION, binds to 50S subunit, blocks protein synthesis initiation
• USES, serious infections and septicemia caused by Strep. Pneum. or Staph Aureus

Question 18

NAC OF POLYMIXIS

Answer 18

• NATURE, antibacterial drugs
• ACTION, interfere with bacterial cell membrane functions
• USES, only for topical uses, can damage host cells if used systemically

Question 19

URINARY TRACT ANTISEPTICS

Answer 19

• drugs are converted into anti-bacterial agents by the low pH of urine (5.5)
• methenamine, used for lower UTIs, slowly decomposes into formaldehyde in urine
• NITROFURANTOIN, narrow-spectrum useful against E.coli UTI