Week 2 Lec 2 8.31.46 pm BIOL341/981 PDF

BIOL341/981: Infection & Immunity Microbial Diseases and Prevention Martina Sanderson-Smith Lecture 4, Week 2 [email protected] 31st July 2024 1...

BIOL341/981: Infection & Immunity Microbial Diseases and Prevention Martina Sanderson-Smith Lecture 4, Week 2 [email protected] 31st July 2024 1 1 Page 1  Lecture Outline 1. Public health measures 2. Chemotherapeutics A. Penicillin B. Vancomycin 3. Immunotherapeutics A. Interferon alpha 4. Action and efficacy of antimicrobials 5. Antimicrobial resistance 6. Bacteriophages 2 2 Page 2  Lecture Outline 1. Public health measures 2. Chemotherapeutics A. Penicillin B. Vancomycin 3. Immunotherapeutics A. Interferon alpha 4. Action and efficacy of antimicrobials 5. Antimicrobial resistance 6. Bacteriophages 3 3 Page 3  Public Health Measures Following the discovery of microorganisms by Pasteur, Koch and others, measures were taken to reduce the incidence and transmission of microorganisms. Such measures include; o clean water o sewerage systems o reduction in overcrowding o better food handling and nutrition o sterilisation methods o use of disinfectants and antiseptics o education on microbial transmission Public health measures are comparatively cheap, cost effective, and save millions of lives every year. 4 4 Page 4  f miiini.IE Public Health Measures England/Wales death rates Measles Scarlet fever Typhoid Whooping cough Diptheria Deaths per 100,000 Penicillin discovered in 1928, but only widely available in 1940s.... year 5 5 Page 5  Lecture Outline 1. Public health measures 2. Chemotherapeutics A. Penicillin B. Vancomycin 3. Immunotherapeutics A. Interferon alpha 4. Action and efficacy of antimicrobials 5. Antimicrobial resistance 6. Bacteriophages 6 6 Page 6  Chemotherapeutics Chemotherapeutic agents are natural or synthetic substances which are either toxic or growth inhibitory to microorganisms (or cancer) and are used internally in humans. Relenza (flu - influenza virus type A, B and C) Antibiotics (antibacterials - eg. penicillin, streptomycin, vancomycin) Quinine (malaria) Artemisinin (malaria) Metronidazole (systemic amoebiasis) 7 7 Page 7  we E've Natural antibiotics: Produced by Microbes Secondary metabolites, or chemical compounds not directly used by the producing organism for growth and reproduction. – Often produced in the stationary phase of growth to help compete for limited resources. – They might help the producer kill competitors that are sensitive to the antibiotic. – They give the producer a selective advantage for nutrients and space. Possible roles of antibiotics. 8 firitimer Page 8  AB is antibiotic Eat Mode of Action 5 major targets for antibacterial agents inhibits Cell wall Cell membrane Ribosomes (protein synthesis) Nucleic acid synthesis (RNA and DNA) Metabolic reactions 9 9 Page 9  Beta-Lactam Antibiotics Target Bacterial Cell Wall Synthesis – Pencillin was the first beta-lactam discovered – Discovered by Alexander Fleming (1928), studied in greater detail by Howard Florey (1938-1941) – Active against many gram-positives and some gram-negatives – They interfere with cell wall synthesis in rapidly growing cells, – Specifically interfere with cross-linking of peptidoglycan layers – Exhibits greatest effect on rapidly growing populations of bacteria – More dormant communities may not be as affected slow – Allergic reaction and evolution of resistance are problematic 5 The Action of Beta-Lactamase on Sodium Penicillin G. 10 metamate L p viii finger peptides Page 10  Other Antibiotics Target Metabolism Glycopeptide antibiotics inhibit bacterial cell wall synthesis. gram ve bacteria – Vancomycin: o Effective against gram-positive bacteria such as staphylococci. o Side effects include damage to the ears and kidneys. o Used as a drug of last resort, especially to treat MRSA. 11 Page 11  Chemotherapeutics was Vancomycin: antibiotic of "last resort" probe Vancomycin is a 1.5 kDa glycoprotein used to kill bacteria (not viruses or parasites etc). This antibiotic is used to kill multiple resistant bacteria such as methicillin resistant Staphylococcus aureus (MRSA). Vancomycin is produced by the soil bacterium Amycolatopis orientalis. Vancomycin was first deployed in 1956, while the first resistant Enterococcus spp. were detected in 1988. www-che.syr.edu 12 12 Page 12  Chemotherapeutics Vancomycin: mode of action Vancomycin kills bacteria by interfering with cell wall synthesis Binds to D-ala terminus, which interferes with transpeptidase activity Peptidoglycan layers cannot be cross-linked, resulting in weakness of fall EE peptidoglycan Vancomycin binding site www-che.syr.edu 13 13 In WHEN Page 13  Chemotherapeutics Vancomycin: origin of resistance Antibiotics have been used as "growth promoters" in intensive agriculture (chickens/pigs etc) since the 1960s. o Avoparcin extensively used, structurally similar to vancomycin. o Avoparcin resistant Enterococci isolated from animals are also vancomycin-resistant. o Europe banned Avoparcin in 1997. o A set of resistance genes (van genes) encodes resistance. 14 14 Page 14  Chemotherapeutics Vancomycin: mechanism of resistance Van genes encode proteins that modify peptidoglycan structure, resulting in vancomycin losing the capacity to bind, and hence to block peptidoglycan synthesis. wait D-lactate we peptidoglycan Vancomycin binding site D-lactate P aka http://www.sumanasinc.com/scienceinfocus/sif_antibiotics.html 15 www-che.syr.edu 15 afore diffide Page 15  Polypeptide Antibiotics Affect the Cell Membrane Topical use only - unacceptable therapeutic window for internal use - cause renal failure and respiratory paralysis Bacitracin interferes with transport of cell wall precursors through the membrane. – skin infections by gram-positive and gram-negative bacteria. – Combined with neomycin and polymyxin B, it is sold as Neosporin. Polymyxins increase membrane permeability of gram- negative rods, leading to cell death. – Polymyxin E is used against many superbugs. – Polymyxin B and bacitracin are combined to make Polysporin. 16 Page 16  Many Antibiotics Affect Translation Aminoglycosides attach to bacterial ribosomes, blocking transcription. – Streptomycin was discovered in 1943 by Waksman. Antibiotics and their affect on protein synthesis. 17 Page 17  Lecture Outline 1. Public health measures 2. Chemotherapeutics A. Penicillin B. Vancomycin 3. Immunotherapeutics A. Interferon alpha 4. Action and efficacy of antimicrobials 5. Antimicrobial resistance 6. Bacteriophages 18 18 Page 18  Immunotherapeutics Immunotherapeutic agents are molecules of the human immune system that are used to "boost" the immune response against microorganisms (or cancer)  Interferon alpha (viruses)  Humanised antibodies (all infectious agents)  Interlukin-2 and interlukin-12 (viruses)  Antibody-toxin conjugates (antimicrobial and anti-cancer) 19 19 Page 19  Immunotherapeutics Interferon alpha: role in immune system. Interferon alpha is produced by many cell types, including B cells, T cells and macrophages and exerts important antiviral role Recombinant interferon alpha is used in the treatment of Hepatitis C virus. en.wikipedia.org 20 20 Page 20  nature boost Immunotherapeutics infection Interferon alpha: mode of action. Interferon alpha is part of the innate antiviral response Induces expression of other host antiviral proteins (protein kinase, 2'-5' oligoadenylate synthetase) which block viral production Although best known for antiviral activity, IFNs have recently been shown to be induced by, and active against – rickettsia, mycobacteria and several protozoa 21 www.med.howard.edu 21 Page 21  Lecture Outline 1. Public health measures 2. Chemotherapeutics A. Penicillin B. Vancomycin signature on warning 3. Immunotherapeutics A. Interferon alpha give eventsThan to m 4. Action and efficacy of antimicrobials 5. Antimicrobial resistance 6. Bacteriophages 22 22 Page 22  ethical abets wilt Characteristics of Antimicrobial Drugs Readily Available Inexpensive Chemically stable (so that it can be transported easily and stored for long periods of time) Easily administered Non-toxic and non-allergenic Selectively toxic against a wide range of pathogens 23 23 Page 23  Clinical Considerations in Prescribing Antimicrobial Drugs Spectrum of Action – The number of different bacterial pathogens a drug acts against o Narrow spectrum (eg. Penicillin) o Broad spectrum (eg. Tetracycline) Efficacy (versus toxicity) - ascertained by: o Diffusion susceptibility test o Minimum inhibitory concentration test o Minimum bactericidal concentration test 24 24 Page 24  Therapeutic Window Selective toxicity says a drug should harm the pathogen but not the host. – The toxic dose of a drug is the concentration causing harm to the host. – The therapeutic dose is the concentration eliminating pathogens in the host. – Together, the toxic and therapeutic doses are used to formulate the therapeutic window. A Representation of the Therapeutic Window. 25 Page 25  Antimicrobial Spectrum Drugs have a range of pathogens on which they will work, which is known as the antimicrobial spectrum. nisheyaifof.rs – Broad-spectrum drugs affect many taxonomic groups. – Narrow-spectrum drugs affect only a few pathogens. broad narrow The Antimicrobial Spectrum of Activity. 26 Page 26  Antibiotic Susceptibility Assays Tube dilution method: decreasing concentrations to determine the lowest concentration of the antibiotic that is effective. mineralisition MIC: The smallest amount of the drug that will inhibit the growth and reproduction of the pathogen 27 Page 27  published abide determine MC MIC – result interpretation Plot data – easy identification of break-point Compared to known MIC values in break-point tables MIC 28 28 Page 28  Colonies acone Amniotes widthMinimum bactericidal concentration test (MBC) MBC: Determines the amount of drug required to kill the microbe rather than just the amount to inhibit it. The lowest concentration of drug for which no growth occurs in the subculture is the MBC 29 29 Lust dont E netflix.ie iiiide our Page 29  Plate based Methods Etest: Determines MIC using an antibiotic-infused strip placed on an agar plate. iii Disk diffusion method: antibiotics Courtesy of bioMerieux, Inc. diffusing from paper disks on a bacterial confluent growth. - Both Etest and disk diffusion method involve measuring the zone of inhibition of bacterial growth. Figure 10.14A: Figure 10.14B: Kirby- Etest Method. Bauer Method. 30 30 Page 30  Zone of inhibition in a diffusion susceptibility test Susceptible Resistant ELI 31 31 Page 31  Zone of inhibition – result interpretation Compare inhibition diameter to known data in break-point tables (published by manufacturer) Species-specific values for each drug diff MC none fewanee Abbreviation Zone Resistant Intermed Sensitive Sensitive/ Antibiotic on disc Diameter Diameter Diameter Diameter Resistant Streptomycin S10 15 mm Ampicillin AM 15 mm Gentamicin GM 15 mm Erythromycin E 23 mm Chloramphenicol C 18 mm Tetracycline Te 19 mm 32 32 Page 32  Lecture Outline 1. Public health measures 2. Chemotherapeutics A. Penicillin B. Vancomycin 3. Immunotherapeutics A. Interferon alpha 4. Action and efficacy of antimicrobials 5. Antimicrobial resistance 6. Bacteriophages 33 33 Page 33  Figure 10.18: Timeline for antibiotic introduction and appearance of antibiotic resistance. 34 Page 34  resisted preadfari snowing Resistance to Antimicrobial Drugs 35 35 Page 35  Resistance to Antimicrobial Drugs The Development of Resistance in Populations — Some pathogens are naturally resistant — Resistance can be acquired by bacteria in two ways L  New mutations of chromosomal genes  Acquisition of R-plasmids via transformation, transduction, and it war conjugation Darwinian theory of evolution = survival of the fittest 36 36 Page 36  Multiple strategies of antibiotic resistance _splitethyk to sina.ttcell or Antibiotic hydrolysis. streptomycinfosphate group Antibiotic modification. Membrane modification/efflux. Target modification. Metabolic pathway alteration. no overcome side effects the Figure 10.20: Antibiotic Resistance Tactics. 37 Page 37  Resistance to Antimicrobial Drugs Improper or excessive use of antibiotics causes antibiotic resistance. – If resistant strains spread to other patients, a superinfection occurs. Three factors have contributed: – Prescription abuse. – Prescription misuse by individuals. – Prescription misuse by healthcare organizations. Figure 10.21: How antibiotic resistance develops. 38 Page 38  Resistance to Antimicrobial Drugs Limiting Resistance Maintain high concentration of drug in patient for sufficient time o Kills all sensitive cells and inhibits others so immune system can destroy (PK/PD modelling) Use antimicrobial agents in combination (synergy) Use specific antimicrobials and only when necessary Develop new variations of existing drugs a variety o Second/Third-generation drugs to overcommen Search for new antibiotics, semi-synthetics, and synthetics o Bacteriocins e.g. antimicrobial peptides (BLIS; http://blis.co.nz/) o Identify new bacterial proteins to target 39 39 Page 39  Lecture Outline 1. Public health measures 2. Chemotherapeutics A. Penicillin B. Vancomycin 3. Immunotherapeutics A. Interferon alpha 4. Action and efficacy of antimicrobials 5. Antimicrobial resistance 6. Bacteriophages 40 40 Page 40  Bacteriophage Therapeutics Bacteriophages: viruses that infect bacteria o Bacteriophages cannot reproduce and survive on their own, take over host cell o Bacteriophage have 2 distinct life cycles waited lytic (T4) lysogenic (lambda) Lytic phage may perhaps be weaponised against pathogenic bacteria. 41 41 Page 41  Feet detention 42 42 Page 42  Bacteriophage: Lytic life cycle 1. Adsorption to the host cell and penetration Phages then inject DNA into the cell 2. Synthesis of phage nucleic acids and proteins Assembly of phage particles 3. Release of phage particles (300 in 22 min) Many phages lyse their host by damaging the cell membrane and cell wall Holin – enzyme which destabilizes the host cell membrane (pokes holes) Lysin – phage enzyme which breaks host cell wall (lyses host bacteria) Utilisation of either complete phage or holin and lysin proteins for therapy? 43 43 Page 43  Bacteriophage Therapeutics Bacteriophages: medical applications Need for alternative therapies for treating bacterial infections o resistance exists to every antibiotic we have Phages are potent anti-bacterials Self-replicating (smart drugs?) Narrow specificity so don’t damage the normal flora Resistance not as significant Resurgent interest in the application of phages to agriculture and human health Used for years in Eastern Europe and Russia Reassessment of Medicinal Phage Spurs Companies to Study Therapeutic Uses. ASM News 64:620-623, 1998. Phages eyed as agents to protect against harmful E. coli. ASM News 65:666-667, 1999. 44 44 Page 44  Bacteriophage Therapeutics Bacteriophages: medical applications Clearance from circulatory system (not a problem if topical application) Immune response against phage upon repeated use Access to site of infection http://ehp.niehs.nih.gov/ 45 45 Page 45  Bacteriophage Therapeutics Bacteriophages: medical applications https://www.sciencemag.org/news/2019/05/viruses-genetically-engineered-kill-bacteria- rescue-girl-antibiotic-resistant-infection 46 46 Page 46  commandments seventh Other Antimicrobial Drugs Target Viruses, Fungi, and Parasites Antiviral drugs interfere with viral replication. – Virus attachment/penetration: Several classes of antifungal drugs cause membrane damage The goal of antiprotozoal agents is to eradicate the parasite Antihelminthic agents target non-dividing Types of Human Infectious Disease. Helminths 47 Page 47  Lecture Outline 1. Public health measures 2. Chemotherapeutics A. Penicillin B. Vancomycin 3. Immunotherapeutics A. Interferon alpha 4. Action and efficacy of antimicrobials 5. Antimicrobial resistance 6. Bacteriophages 48 48 Page 48