Control of Microbial Growth Flashcards
Koch’s postulates (1)
Suspected pathogen should be present in all cases of disease and absent in healthy animals
Koch’s postulates (2)
Suspected organism should be grown in pure culture
Koch’s postulates (3)
Cell from pure culture of suspected organism should cause disease to healthy animals
Koch’s postulates (4)
Organism should be reisolated and shown to be the same as the original one
What the first vaccine against?
Anthrax
How Pasteur made anthrax vaccine?
- Weaken anthrax bacteria by heating it until it cannot cause disease.
- Inject that weakened anthrax bacteria to healthy sheep
- The sheep’s immunity recognize the bacteria and produce antibody to against it.
- Inject anthrax bacteria to vaccinated sheep and normal sheep
- Result: vaccinated sheep survive while other can’t
What cause death in surgery?
Nosocomial infections
Liset’s surgical protocol for disease control
- Wash hands before surgery
- Heat sterilization of surgical instrument
- Apply phenol to wound
Carrier
People recover from disease but still carry the bacteria
Control measure for Salmonella typhi
- Water chlorination
- Milk pasteurization
- Sewage treatment plant design improvement
- Transmission control (flies, carries)
- Preventive vaccinate and antibiotic therapy
Aseptic
Environment or procedure free of microbial contaminants
Sterillaztion
killing all living organism, including spores
Disinfection
killing most organism from inanimate object
Antisepsis
killing pathogen from surface of living tissues
Sanitation
reducing microbial population to safe level
Pasteurization
Heat to destroy pathogen and reduce spoilage microorganism in food
Antimicrobial treatment result facts
Microbial death does not occur at once, but in constant rate determined by D-value
D-value
how long it take to reduce bacteria by 90%
Effectiveness of treatment depend on
- Size of population
- Exposure time of agent
- Concentration, temperature, pH
- Characteristics
- Interaction and protective features of environment
The most resistant microbial charcteristic
Prion: naked protein against most chemical method, cooking, and autoclaving
How mycobacterium resist antimicrobial treatment?
Waxy mycolic acid prevent chemical entry
How endospore and cyst resist antimicrobial treatment?
Thick coat prevent chemical entry
Surprising fact of enveloped virus
Enveloped virus more easily damaged than non-enveloped one
What antibiotic cannot do?
Cannot fight injection caused by virus
How antibiotic work?
Inhibit the bacterial process by killing them or keeping them from reproducing
Key targets of antimicrobials
Cell wall synthesis (Penicillin)
DNA replication (flouroquinolones)
RNA synthesis (rifampicin)
Protein synthesis (tetracyclines, macrolides)
Folic acid synthesis (sulfonamides)
Membrane disruption (daptomycin for Gram-positives, colistin for Gram-negative)
How penicillin disrupt cell wall synthesis?
Inhibit crosslinking of peptidolycan
How rifampicin inhibit RNA sysnthesis?
Inhibit RNA polymerase (expect eukaryotic)
Types of antibiotic resistances
- Intrinsic resistance: innate
- Acquired resistance: develop the ability to resist over time
Mechanisms of HGT
Transduction
Conjugation
Transformation
Germ Theory of Disease
Disease is made of small microscopic entities that replicated within the disease
Bactericidal agent
Compound kill bacteria
Bactericidal vs bacteriostatic
Bacteriostatic just slow down the growth while bactericidal completely kill all
Antimicrobial Efficacy Test
Incubate challenge organism with antimicrobial agent then draw the kill curves
Or use dilutions
Broad-spectrum
Antimicrobial’s ability to affect large variety of microbes
SOS response
Bacterium’s coordinated response to DNA damage
Problems with antibiotic resistance
- Overuse/misprescribing
- Non-adherence to antibiotics regiments
- Wide-spread use in agriculture
How tetracycline inhibit protein synthesis
Bind to A site to block tRNA come in, so new amino acid cannot add to growing peptide chain so synthesis of peptide is aborted
How macrolide inhibit protein synthesis
Target the 23s large subunit so peptide bond formation cannot catalyze
How sulfonamide inhibit folic acid synthesis
Target enzyme dihydropteroate so the thyme synthesis cannot be done
How daptomycin disrupt membrane in Gram-positive
Attach into membrane and form large pores that result in leakage of ions and electrolytes
How colistin disrupt membrane in Gram-negative
Disrupt outer membrane and then inner membrane
Why using antibiotics in long term can link to C. diff?
Antibiotic destroy normal microflora.
Normal microflora cannot eat primary bile salt in intestine and make them turn to secondary bile salt.
Primary bile salt activate C. diff pore.
Ways of acquired resistance
Acquiring mutation
Acquiring new genes by HGT
HGT
donor - receipt
Gene mutation cause antibiotic resistance
Most bacteria killed by antibiotic. Only drug resistance bacteria survive and multiple
