R.O Lecture 5&6 Flashcards

Question

Heat

Answer 1

* Cheapest, most effective and widely used control * Denatures enzymes * Suitable for materials undamaged by heat * Various approaches: - Dry heat - Moist heat - Pasteurisation

Answer 2

* Used to sterilise metal objects and glassware * Flame: Innoculating loops, flasks/tube mouths * Dry heat sterilisation for moisture-sensitive materials * Longer heating times/temperatues than moist heat

Answer 3

* Causes denaturation of proteins and may disrupt membrane lipids-widely used * Boiling water can kill most vegetative bacteria and fungi * Heating water under pressure (higher temps) in an autoclave: 121 °C for 15-20 min can kill also spores

Answer 4

Invented by Pasteur; does not achieve sterility Kills pathogenic organisms in raw products (milk etc) - Flash method: 71.6 °C for 15 sec - Holding method: 62.9 °C for 30 min - Ultrahigh temperature processing (UHT): 74°C--- 140°C--- 74°C (5 sec) Can be stored at RT

Answer 5

* Refrigeration: (2-8 degrees) Slows growth based on reduction in enzyme kinetics * Freezing : (-20 degrees) slows metabolic activity to prevent food spoilage but does not kill organisms.

Answer 6

* Water absence inhibits enzymatic activity * Usually bacteriostatic, but may be bactericidal depending on the species * Used to preserve some foods * Freeze-drying: Lyphilisation - used to preserve bacterial cultures.

Answer 7

* Ultraviolet (UV) light * Ionising Radiation * Microwave Radiation

Answer 8

Ultraviolet (UV) light: (40 – 390 nm) Works best at 200nm; Used for sterilising surfaces Damages DNA and proteins; DNA repair can aid survival

Answer 9

Ionising Radiation: X-rays and gamma rays (< 40 nm) – dislodge electrons from atoms, creating ions and radicals. Radicals kill by interacting with DNA, proteins, lipids etc.

Answer 10

(1mm – 1m) Acts on water molecules which release heat – not effective on spores

Answer 11

* Passage of liquid/gas through small pores; traps in a sizespecific manner * Membrane filters: Specified pore sizes (0.025 – 25 µm) * Suitable for heat-sensitive materials (e.g. media supplements, drugs, vitamins) * HEPA (High-efficiency particulate air) filters in labs

Answer 12

- 0.45 - a few bacteria, viruses molecules - 0.22 - viruses, molecules - 0.10 - medium-sizes to small viruses molecules

Answer 13

High salt/sugar concentrations draw water from cells Bacteriostatic – metabolism cannot progress Food preservation: Curing, pickling, jams etc.

Answer 14

* Ultrasonic waves can cause bacteria to cavitate – denatures proteins and disintegrates bacteria * Can be used to lyse bacteria to release components for study, but not practical for sterilisation.

Answer 15

* Oxidation of light-sensitive materials - can be used with dyes to destroy bacteria and viruses: may help sanitize clothing.

Answer 16

* Phenol coefficient * Filter Paper Method * Use-dilution Test

Answer 17

Agents that prevent growth at the lowest concentrations are considered the most effective disinfectants

Answer 18

- Comparison to the 'original' disinfectant - Some disadvantages

Answer 19

* Test bacteria coated onto carrier rings * Incubated in test solutions (time based on product) * Cultured in broth to detect surviving microbes

Answer 20

Efficacy of a Chemical Agent applied to a filter paper disc In vitro results may not translate in practice

Answer 21

* Disc-diffusion (Kirby-Baeur) method * E (epilsometer test) * Dilution Method

Answer 22

* Lawn of target bacteria spread over plate * Specific concentrations of antimicrobial agents on filter paper discs * Zones of inhibition measured (diameter) * Issues due to bacteriostatic vs. bactericidal actions

Answer 23

* E (epsilometer) test determines sensitivity to antibiotic and also minimum inhibitory concentrations (MIC) – antimicrobial gradient * Gradient of antibiotic concentrations on a strip (high to low) * Intersection of zone of inhibition with the strip used to determine the MIC

Answer 24

* Bacteria inoculated into serial dilutions of an antimicrobial agent MIC can be determined * Measuring sensitivity to an antimicrobial agent (antibiotic susceptibility testing) * Can combine with second test to determine if bacteriostatic or bacteriocidal (minimum bactericidal concentration; MBC)

Answer 25

Chemical substance used to treat diseases cause by pathogenic mcrobes

Answer 26

Chemical substance (drug) produced by microogransims, with the capacity to control growth/kill microbes. Bacteriostatic or bacteriocidal Synthetic or natural product (bacteria/fungi)

Answer 27

* Alexander Fleming (1929) * Penicillium notatum inhibited S.aureus * Recognised growth inhibition potential - Penicillin * Mass production by 1940s (WW2) * Post-war studies led to discovery of new antibiotics

Answer 28

* Selectively toxic to pathogens; non-toxic to host and minimal effect on normal microbial flora – determine chemotherapeutic index * Should not stimulate an allergic reaction (hypersensitivity) * Host should not destroy or neutralise drug before effective * Pathogens should not easily become resistant to the drug * Agent should reach the site of infection (solubility)

Answer 29

Chemotherapeutic index. The ratio of the minimal effective dose of a chemotherapeutic agent to the maximal tolerated dose.

Answer 30

Range of different microogranisms treatable with an agent

Answer 31

Broad spectrum: Active across a wide range of taxonomic groups; useful for untargeted treatment without pathogen identification

Answer 32

- Narrow spectrum: Specifically targets small number of organisms; may protect host microflora; reduces development of drug resistance

Answer 33

1. Inhibition of Cell Wall Synthesis 2. Disruption of Cell Membrane Function 3. Inhibition of Protein Synthesis 4. Inhibition of Nucleic Acid Syntheisis 5. Action as Antimetabolites

Answer 34

* Penicillins * Cephalosporins * Bacitracin * Vancomycin

Answer 35

* Penicillins: Bactericidal; All contain a β-lactam ring; * Natural penicillins (G, V) are penicillinase sensitive and narrow spectrum. * Semi-synthetic penicillins are modified to increase penicillinase resistance and broaden spectrum (e.g.methicillin, ampicillin, amoxicillin) * Interfere with PG cross-linking: Targets PBP

Answer 36

* Cephalosporins - effective against Gram-negatices * Resistant to Penicilliniases * More expensive; mainly IV/IM * Interfere with PG cross-linking Targets PBP

Answer 37

* Bacitracin: Polypeptide antibiotic * Effective against Gram positives * Topical application * Interfere with linear PG strand formation

Answer 38

* Vancomycin: Glycopeptide antibiotics; * Narrow spectrum; * toxic * Penicillinase-resistant * Interfere with linear PG strand formation

Answer 39

* Peniclllin has one R site, which means it can only bind to one target in bacteria. This limits its spectrum of activity and makes it more effective against certain types of bacteria than others. * Cephalosporsins, have two R sites, which gives them a broader spectrum of actiity and makes them more effecive against a wider range of bacteria than penicllin. These two R sites also make cephalosprins more resistant to certai bacterial enzymes than can break down penicllin. ## Footnote look at slide 25 for the common method of administration of each.

Answer 40

Alter permeability of bacterial cell membranes; Polypeptide antibiotics; clinical application limited to certain members due to similarities between host and bacterial cell membranes

Answer 41

* Polymyxins: (A, B, C, D, E) used only when pathogen is resistant to other less toxic antibiotics; Gram negatives; Topical

Answer 42

combine with sterols; therefore effective against mycoplasmas (and also systemic fungal infections).

Answer 43

* Bacteriocin of E.coli; encoded by Col plasmid, which also codes for immunity protein. * Kills bacterial cells not carrying the plasmid e.g. cells of same species.

Answer 44

* Similar to antibiotics * Produced only by bacteria * Specific to certain bacterial strains , wheras antibiotics can be effective against a broad range of bacteria.

Answer 45

Takes advantage of differences between bacterial and eukaryotic ribosome - selective toxicity

Answer 46

* Amino sugars linked by glycoside bonds. Broad spectrum. * Bacteriocidal; bacteriostatic at lower doses. Work synergistically with other compounds (e.g. penicillin) * Streptomycin (1940s); now has high resistance levels; toxic. * Other compounds (kanamycin, gentamicin etc.)

Answer 47

Tetracyclines: Interfere with tRNA attachment. Bacteriostatic; very broad spectrum; can inhibit intestinal microflora

Answer 48

Bacteriostatic; broad spectrum ; inhibits peptide bond formation. Damages bone marrow.

Answer 49

Macrolides: Erythromycin – Bacteriostatic. Can not penetrate Gram negative cell walls. Used as an alternative to Penicillin

Answer 50

Can be Toxic to host cells due to common targets. * Rifampin: Inhibits mRNA synthesis by binding RNA polymerase; High absorbance into tissues and cells; Bactericidal; Broad Spectrum; Interacts with other drugs; Treatment of mycobacteria infections-leprosy and tuberculosis * Quinolones: Blocks bacterial enzyme that unwinds DNA prior to replication; Broad spectrum; Used for UTIs; Can affect cartilage development

Answer 51

Compounds that interfere with metabolic reactions by: 1) Competitive inhibition of enzymes or 2) Erroneous incorporation into important molecules

R.O Lecture 5&6 Flashcards

(75 cards)