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Game plan Lecture Antibiotics Antibiotic resistance Gene transfer Transformation Transduction Conjugation Lab Lab Exam Pre-lab Transformation.

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Presentation on theme: "Game plan Lecture Antibiotics Antibiotic resistance Gene transfer Transformation Transduction Conjugation Lab Lab Exam Pre-lab Transformation."— Presentation transcript:

1 Game plan Lecture Antibiotics Antibiotic resistance Gene transfer Transformation Transduction Conjugation Lab Lab Exam Pre-lab Transformation

2 - 1928: Fleming discovered penicillin, produced by Penicillium Discovery of Antimicrobial Drugs Figure 1.5

3 Where to antimicrobials come from?

4 Broad spectrum- affect a broad range of gram-positive and gram-negative bacteria Narrow spectrum- affects a narrow range of bacteria Spectrum of activity

5 This bacterium is lysing because an antibiotic disrupted its cell wall. Why doesn’t the antibiotic lyse human cells? Pit Stop

6 The Action of Antimicrobial Drugs Figure 20.2

7 Case study in narrow spectrum antibiotics: Penicillin

8 Case study in narrow spectrum antibiotics: Penicillin - Natural penicillins - Semisynthetic penicillins

9 Penicillin prevents cross-linking in cell wall

10 Figure 20.8 A peek at antibiotic resistance… penicillinase

11 Resistance to Antibiotics Figure Enzymatic destruction of drug 2.Prevention of penetration of drug 3.Alteration of drug's target site 4.Rapid ejection of the drug

12 - A variety of mutations can lead to antibiotic resistance - Misuse of antibiotics selects for resistance mutants. Misuse includes: Using outdated or weakened antibiotics Using antibiotics for the common cold and other inappropriate conditions Using antibiotics in animal feed Failing complete the prescribed regimen Using someone else's leftover prescription - Resistance genes are often on plasmids or transposons that can be transferred between bacteria Mechanisms of resistance

13 The future of antibiotic resistance… Carbapenem-Resistant Enterobacteriaceae (CREs) - CRE definition by CDC: resistant to large range of beta-lactam antibiotics - Nonsusceptible to meropenem, imipenem, doripenem - Resistant to 3rd generation cephalosporins - Ceftriaxone, cefotaxime, ceftazadime - CREs contain different enzymes that break down carbapenems: - KPC (Klebsiella pneumoniae Carbapenemase) - Most common CRE in United States. First identified in 1996 in North Carolina. [Carbapenem resistant Klebsiella pneumonia (CRKP)] - NDM-1 (New Delhi Metallo-beta-lactamase)- resistance to all antibiotics except colistin (affects membranes) and tigecycline (protein synthesis inhibitor ~ tetracylcine) - Originally identified in patient from New Delhi in 2008

14 Molton et al CID 2013 Global spread of CREs

15 Map of carbapenemase-producing CREs in US

16

17 Molton et al. CID 2013 The antibiotic pipeline looks bleak

18 How are CRE genes transferred from species to species? Vertical gene transfer Horizontal gene transfer

19 All transfer methods rely on recombination Figure 8.22

20 Horizontal gene transfer: Transformation Demo

21 Horizontal gene transfer: Transformation 1920s- Griffith experiment

22 Horizontal gene transfer: Transformation 1920s- Griffith experiment

23 Horizontal gene transfer: Transformation DNA: -Cell free or “naked” DNA Requirements: -Competent cells -Recombination

24 Horizontal gene transfer: Transduction Demo (generalized, specialized)

25 Horizontal gene transfer: Generalized transduction DNA type: -Small chromosomal fragments from bacteria Requirements: -Lytic phage -Recombination

26 Horizontal gene transfer: Specialized transduction DNA type: -Bacterial chromosome fragment near phage DNA Requirements: -Lysogenic phage -Formation of prophage -Recombination

27 Horizontal gene transfer: Transduction

28 Horizontal gene transfer: Conjugation Demo (F factor)

29 Horizontal gene transfer: Conjugation DNA type: -F plasmid Requirements: -F + cell -F – cell -Sex pili/ cell surface molecules

30 Horizontal gene transfer: Hfr Conjugation DNA type: -F plasmid/ bacterial chromosome Requirements: -Hfr cell -F – cell -Sex pili/ cell surface molecules

31 Horizontal gene transfer compared

32 Horizontal gene transfer!

33

34 Independent Study Study for Exam 2!


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