By: Alaina Darby Intro to Antibiotics

 Intro to Antimicrobials Overview  Practice Questions  Specific Things to Remember  Helpful Tips for the Test Outline

Intro to Antimicrobials Overview

 Antibiotics  Produced by a microorganism  Most of the older antimicrobials can be classified as antibiotics and are, therefore, classified as antibiotics and antimicrobials  Example: penicillin  Antimicrobials  Antibiotics are a subset of antimicrobials  Antimicrobials inhibits growth or kills microorganisms  Many newer antimicrobials are not natural products, so they are antimicrobials but not antibiotics Antibiotic vs Antimicrobial

 Gram stain  Selective toxicity  Post-antibiotic effect (PAE)  Bactericidal  Bacteriostatic  Spectrum  Biofilm  Synergy Terms

 Concentration-dependent  C max /MIC  C max is the peak concentration  Kills at high concentration but doesn’t really matter as much how long they are at the high concentration  Can have longer dosing intervals  These have a long PAE  Example: aminoglycosides  Time-dependent  T>MIC  Has to be above the MIC for an extended period of time but really high concentrations don’t usually increase killing  Can give smaller doses more frequently  If you are giving the drug IV, then a continuous infusion is good  Has little to no PAE  Example: vancomycin Concentration vs Time-Dependent Killing

 DIAGNOSIS!!  Specificity/Spectrum  Bactericidal/Bacteriostatic  PAE  Site of infection  Other factors at the site of infection  Host factors Choosing Antibiotics

Helpful memory aid:  Think about the stock market. When you play the stock market, you want to buy low and sell high.  There are 2 subunits of the ribosome – 50S and 30S.  So… A smart person buys AT 30 and CELS for 50.  AT: A (aminoglycosides) T (tetracyclines)  CELS: C (clindamycin/chloramphenicol) E (erythromycin/other macrolides) L (linezolid) S (streptogramins) SITE OF ACTION

 Intrinsic vs Acquired  Intrinsic: already present  Acquired: mutation or transmission of genes  Mechanisms  Receptor alteration  Decreased transport into microorganism  Increased export (e.g. tetracyclines)  Inactivation (e.g. beta-lactams, aminoglycosides)  Alternative metabolic pathways (e.g. TMP/SMX)  Defect in activation (e.g. metronidazole, 5-flucytosine) Resistance

Practice Questions

Which of the following is a term that would not apply to the treatment of a virus-caused condition? a.Chemotherapy b.Antibiotic c.Antimicrobial d.Selective toxicity

Which of the following describes post-antibiotic effect? a.Suppression of bacterial growth after ceasing antibiotic administration b.Suppression of bacterial growth after ceasing antibiotic administration and concentration is below MIC c.Bacterial regrowth after ceasing antibiotic administration d.Bacterial regrowth after ceasing antibiotic administration and concentration is below MIC

Which of the following is the most important factor in determining antimicrobial therapy? a.Antibiotic specificity and spectrum b.Bactericidal vs bacteriostatic function c.Diagnosis of infecting organism d.Post antibiotic effect

Why might one choose erythromycin over an antibiotic like metronidazole that has a broader spectrum? a.Less alteration of GI microflora b.Aid in organism identification c.Target a specific area of the body d.Decrease the MIC

Which of the following describes the latency period? a.Time from administration until the drug kills all bacteria in a cidal drug b.Time from administration until the drug begins to inhibit bacterial multiplication in a cidal drug c.Time from administration until the drug begins to reduce the number of pathogens in a cidal drug d.Time from administration until the drug begins to reduce the number of pathogens in a static drug

Which of the following relies upon host defenses to aid in eliminating the pathogen? a.Bactericidal b.Bacteriostatic c.Neither bactericidal or bacteriostatic d.Both bactericidal and bacteriostatic

What would not be a reason for choosing a bactericidal agent over a bacteriostatic agent? a.More rapid acting b.Reduced number of organisms c.More effective d.Effects without maintaining MIC

Which of the following cases would not require a bactericidal agent? a.Bacterial endocarditis b.Pertussis c.Meningitis d.Transplant patient

Which of the following exhibits no post-antibiotic effect? a.Aminoglycosides b.Fluoroquinolones c.Clindamycin d.Vancomycin

Which of the following exhibits no post-antibiotic effect? a.Time-dependent b.Concentration-dependent c.Time-dependent and concentration-enhanced d.Concentration-dependent and time-enhanced

Which of the following is a protected site into which antibiotic will not be readily available? a.Bladder b.Kidney c.Prostate d.Lungs

Which of the following is not a major concern when selecting an antibiotic for its concentration at the site of infection? a.Patient compliance b.Metabolism and excretion c.Route of administration d.Anaerobic conditions

Which of the following would not be reason to use combination chemotherapy? a.Increase bactericidal activity at the same site b.Prevent emergence of resistant organisms c.Permit lower doses of the antibiotics d.Treat infection of unknown etiology

Which of the following is not an infection that is often treated with combination chemotherapy? a.Tuberculosis b.Malaria c.HIV d.Meningitis

What would not be a reason to choose a single agent for therapy? a.Same site toxicity b.Mixed bacterial infection c.Static plus cidal combination d.Increased cost

Which of the following is not true of superinfections? a.They are due to alterations in the normal flora b.Incidence increases with broad spectrum agents c.They are a reappearance of the primary infection d.They appear during treatment

Which of the following is not true of antibiotic resistance? a.Natural resistance is present before antibiotic therapy b.Acquired resistance is caused by the antibiotic c.Acquired resistance occurs in a species that was once sensitive d.Acquired resistance is a consequence of antibiotic therapy

Which of the following is not an indication for prophylaxis? a.Prevent infection by a specific organism b.Prevent all potential secondary infections in a patient ill with other diseases c.Prevent infection from rupture of a viscus or a surgical procedure d.Prevent bacterial endocarditis or recurrence of rheumatic fever

Which of the following would not be true of the ideal antimicrobial? a.Alkaline stable b.Orally absorbed c.Bactericidal d.Good distribution to bones

Which of the following would not be true of the ideal antimicrobial? a.Readily excreted b.Widest spectrum possible c.Low MLC d.High tissue concentration

Important points for certain bugs and drugs. Specific Things to Remember

 Almost everything that works on the cell wall is renally excreted.  Almost everything that works anywhere else is metabolized. Metabolism/Excretion

 Anaerobes  Clindamycin  Metronidazole  VRE  Linezolid  Streptogramins (faecium only)  Daptomycin  Cephalosporines DO NOT treat enterococcus!  Gram negatives only  Aztreonam  Pseudomonas  Cefepime  Ceftazidime  Piperacillin/Tazobactam (Zosyn)  MRSA  Vancomycin  Ceftaroline  Linezolid  Streptogramins  Daptomycin Spectrum

 Clindamycin  C. difficile infection  Chloramphenicol  Gray baby syndrome  Telithromycin  QT prolongation  Sulfonamides  Hypersensitivity  Hematologic (G6PD deficiency)  Kidney stones  Metronidazole  Disulfram-like reaction  Isoniazid  Liver failure  Almost everything can cause GI disturbances  Aminoglycosides  Nephrotoxicity  Ototoxicity  Tetracyclines  Dental discoloration  Photosensitivity  Fluroquinolones  Photosensitivity  Tendon ruptures  Penicillins (and sometimes Cephalosporins)  Hypersensitivity Adverse Effects

 Tetracyclines  Ca 2+ chelation  Macrolides  Strong CYP inhibitors  Especially erythromycin  Exception: azithromycin  Rifampin  Induces everything Drug Interactions

Some fun memory aids for you! Helpful Tips for the Test

 Clindamycin has good activity in the bone. (That was a question my P1 year!)  Tigecycline is hepatically and renally excreted… Tigers poop and pee a lot. (I didn’t come up with that.)  TMP/SMX treats…  T: Tree (respiratory)  M: Mouth (GI tract)  P: Pee (genitourinary)  S: Syndromes (AIDS… like PCP)  CefTAZidime and cefEPIme are the only cephalosporins that are EPIc enough to TAZe Pseudomonas.  Quinolones are a “flock of sinners” (-floxacins) that gyrate (DNA gyrase) their hips at night (photosensitivity). They dance and party so much that their tendons rupture and they have heart problems (QT prolongation).

The End!