General Microbiology Flashcards
Louis Pasteur Contributions
Louis Pasteur Contributions
- introduces techniques for sterilisation
- developed autoclave
- discovered process of attenuation
- developed live vaccines
Moist heat sterilisation
Moist heat sterilisation
• <100` -pasteurisation of milk inspissation • 100` -boiling steam@ atm pressure tyndallisation steam under pressure : autoclave
autoclave
autoclave
gravity displacement type & high vacuum sterilisers
steam under pressure
dry heat sterilisation
dry heat sterilisation
flaming
incineration
hot-air oven
bacterial flagella
bacterial flagella
- organs of locomotion - darting motion of vibrio
- filament, hook, basal body
- made of flagellin protein
- arrangement: peritrichous, monotrichous, lophotrichous, amphitrichous
- demonstrate by dark ground illumination & spcl staining
bacterial capsule
bacterial capsule
- amorphous viscid material organised into a sharply defined structure
- negative staining in wet films with india ink
- quellung reaction
- give protection,virulence
enrichment media
enrichment media
- liquid
- to suppress commensal bacteria but allows pathogen to grow
- tetrathionate broth, selenite f broth
transport media
transport media
- for specimens with fastidious organisms
- stuart’s medium for gonococci
bacterial spore
bacterial spore
• each bacterium-one spore-single vegetative cell
• bulging, non-bulging
central, terminal, subterminal
• destroyed by autoclaving at 121` 15 min
• stained by modification of Ziel-Nielsen
transduction
transduction
- gene transfer by bacteriophage
- types: generalised & restricted
- can transduce chro. DNA, episome,plasmid
gaseous disinfectant
gaseous disinfectant
- ethylene oxide -to sterilise heat-sensitive equipment, explosive, carcinogenic
- formaldehyde gas - to fumigate OTs
- betapropiolactone (BPL) - carcinogenic, not used
- hydrogen peroxide fogging - bactericidal, short cycletime, non-toxic
bacterial growth curve
bacterial growth curve
1.lag phase - time to adapt
2.log phase - exponential growth
3.stationary - cell division stops due to less nutrients
4.of decline - cell death
total & viable count
mutational drug resistance
mutational drug resistance
- stepwise (penicillin) & one-step (streptomycin)
- plasmid-mediated transferable drug res., R factor
- depends on frequency of use of antibiotics
Selective media
Selective media
- solid
- inhibiting substance added
- DCA for fecal samples, TCBS for vibrio
Robert Koch
Koch’s postulates
A microorg. can be accepted as causative agent of inf d/s only if:
• bacterium is constantly associated with lesions
• possible to isolate bacteria in culture from lesions
• inoculation of culture into animals reproduce lesions
• possible to re-isolate bacteria from experimental animals
• specific Ab to bacteria demonstrable in patient’s serum
