General Microbiology Flashcards
(113 cards)
1
Q
Father of microbiology
A
Louis Pasteur
2
Q
Father of bacteriology
A
Robert Koch
3
Q
Koch’s postulates
A
- The organism should be constantly associated with the lesions of the disease.
- It should be possible to isolate the organism in pure culture from the lesions of the disease.
- The isolated organism when inoculated in suitable lab animals should produce a similar disease.
- It should be possible to re- isolate the organism in pure culture from the lesions produced in the experimental animals.
4
Q
Important example of not fulfilling the koch’s postulates
A
Lepra bacillus
5
Q
Guinea pigs already infected with tubercle bacillus responded with an exaggerated inflammatory response when injected with the tubercle bacillus or its proteins. This hypersensitivity reaction is called _
A
Koch’s phenomenon
6
Q
Louis pasture - important discoveries.
A
- Methods & techniques of bacteriology.
- All forms of life, even microbes, arose only from their like.
- Ubiquity of microorganisms in air by experiments in swan-necked flasks.
- Sterilization techniques & development of steam sterilizer, autoclave & hot air oven.
- Live vaccine.
7
Q
Outer capsule/ slime wall in bacteria is made of _
A
Glycocalyx
8
Q
Cell wall of bacteria contains _
A
Muramic acid.
9
Q
Cell membrane of bacteria is devoid of _
A
Sterols.
10
Q
Cytoplasm of bacteria contains _ ribosomes
A
70S
11
Q
Invagination of bacterial cell membrane & site for respiratory enzymes.
A
Mesosomes.
12
Q
Which bacteria lacks cell wall, has sterols in cell membrane & aka jumping joker?
A
Mycoplasma.
13
Q
Which bacteria lacks muramic acid in cell wall?
A
Chalamydia.
14
Q
Slime & capsule are _ in nature.
A
Polysaccharide.
15
Q
When a group of bacteria growing together produce slime, the slime gets collected to form _.
A
Biofilm
16
Q
Function of capsule
A
- Antiphagocytic.
- Phage protection.
- Most important virulence factor.
- Antigenic in nature → induces antibodies.
17
Q
Capsule + anti-capsular antibodies ( specific) ⇒ swelling of capsule.
This reaction is called as _
A
Quellung reaction.
18
Q
Capsule is demonstrated by _
A
Negative staining ⇒ India ink or nigrosine
Capsule has no net charge, so not demonstrated by gram stain
19
Q
Name capsulated bacteria.
A
( Yes Some Very Smart Bacteria Have Killer And Mean Capsule)
- Yersenia pestis
- S. Pneumoniae
- V. Parahemolyticus
- V. Cholerae O 139
- Group A,B,C,D of B hemolytic streptococcus
- Bacteroides fragilis [Zwitter ionic capsule]
- Bordetella pertussis [ non antigenic capsule]
- Hemophilus influenzae
- Klebsiella
- Bacillus anthracis [ polypeptide capsule]
- Meningococcus
- Clostridium perfringens
20
Q
Bacterial cellwall is made up of _
A
PePtidoglycan cross linked by peptides
21
Q
In gram positive cell wall, murein monomer contains _
A
N- acetyl glucosamine & N - acetyl muramic acid
22
Q
Cross linking in gram positive cell wall is mediated by _
A
Carboxy peptidases & trans peptidases ( penicillin binding proteins )
23
Q
Role of teichoic acids in gram positive all wall.
A
Adhesion & integrity of cell wall.
24
Q
In gram negative cell wall, just above the cell
membrane ,_ contain 2 layers of murein
A
Periplasmic space
25
Outer to the periplasmic space ⇒ outer membrane ( phospholipid bilayer) with
_
1. Integral/ structural proteins
2. Porins
3. Lipopolysaccharides/ endotoxins.
26
Parts of lipopolysacchaside/ endotoxins
1. Lipid A
2. Core polysaccharide → ketodoxy octanoic acid
→ heptose
3. O/ somatic antigen→ variable part
27
Pharmacological effects of endotoxins in humans
1. Fever
2. hypotension
3. Increased vascular permeability
4. Intravascular coagulation→DIC → shock
28
_ Gram positive bacteria has LPS in cell wall
Listeria
29
Cytochromes, respiratory chain enzymes, synthetic enzymes of the cell wall are located in _
Cell membrane
30
Single flagella at one pole
Monotrichous
| Eg. Vibrio, pseudomonas aeruginosa
31
Multiple flagella at single pole
Lophotsichous
| Eg. H. Pylori, campylobacter
32
Flagella on both the poles
Amphitrichous
| Eg. Spirillum
33
Flagella all over the surface of the bacteria
Peritrichous
Eg. Bacillus, clostridium, enterobactesiaceae
Vibrio parahemolyticus → on solid media
Listeria → only at 25 -28°c
34
Flagella in the periplasmic space
Endoflagellae
| Eg. Spirochetes
35
Pili only present in gram negative bacteria & mediate adhesion
Common pili
36
Pili present in both gram positive & negative bacteria which mediates conjugation
Sex pili
37
Bacteria containing _ can produce sex pili
F plasmid
38
Spore forming pathogenic bacteria
1. Bacillus
| 2. Clostridium
39
_ Are circular, extrachromosomal, ds DNA present in cytoplasm of bacteria
Plasmids
40
Plasmid integrated with chromosomes →_
Episome
41
Plasmid which mediate conjugation function.
F/ fertility plasmid
42
Plasmid which mediate function of resistance to antibiotics
Resistance plasmid
43
Plasmid which encodes bacteriocin
Col plasmid
44
Fluorescent dyes
1. Auramine O. → stains mycolic acid
2. Rhodamine B→ "
3. Acridine orange → ss/ ds DNA
4. FITC ( fluorescence iso thio cyanate)→ binds to antibody
5. Lissamine rhodamine→ "
45
Gram stain introduced by _
Hans Christian Gram
46
I° stain in gram staining
Crystal violet/ methyl violet / gentian violet
47
Moderator in gram staining
Iodine
48
Decolouriser in gram staining
Alcohol/ acetone/Both
49
Counterstain in gram staining
Saffranine / basic fuchsin/ neutral red
50
Gram positive bacteria appear purple because
1 . Gram positive cytoplasm is more acidic→ binds to basic stain
2.Gram positive cell wall is thicker→ retains 1° stain
51
Gram negative bacteria appears pink because
Gram negative cell wall→ more lipid → gets dissolved by alcohol.
52
Dark field microscopy used for _
Observing slender bacteria like spirochete
53
Structure of bacterial spores
1. Core
2. Spore wall
3. Spore cortex→ thickest layer
4. Spore coat→resistant of chemical disinfection
5. Exosporin
54
Phases of bacterial growth curve
1. Lag phase
2. Log phase
3. stationary phase
4. phase of decline
55
Define sterilization.
A process by which an article, surface or medium is made free of all forms of life including spores.
56
Define disinfection.
Destruction of only pathogenic microorganisms.
57
List physical methods of sterilization.
1. Sunlight.
2. Heat→ dry heat
→ moist heat.
3. Ozone
4. Filtration
5. Radiation
58
List chemical methods of sterilization
1. Alcohols
2. Aldehydes
3. Phenols
4. Halogens
5. Oxidising agents
6. Salts
7. Surface active agents
8. Dyes
9. Vapor phase disinfectants.
59
Procedures in dry heat sterilization
1. Flaming
2. Red heat
3. Incineration
4. Hot air oven
60
Mechanism of action in dry heat sterilization.
→ oxidative damage
→ Denaturation of proteins.
→ increase electrolyte levels to toxic levels.
61
Hot air oven is used for sterilization of _
→ metallic instruments.
→ glass ware
→ oils, jellies, powder, waxes
→ cotton swabs.
62
Temperature in hot air oven sterilization.
→ 160°c for 2 hours - most common
→ 170°c for 1 hour
→ 180°c for 30 min
63
Precautions in hot air oven stesilization.
→ No rubber objects
→ No overloading
→ cool 2 hours before opening
64
How to measure efficacy of hot air oven
1. Physical - temperature chart recorder.
2. Chemical- Browne's tube NO3
3. Biological -spores of c. tetani or bacillus subtilis.
65
Moist heat sterilisation methods at temperature < 100°c
1. Pasteurization
2. Serum Bath→ moist heat @ 56°c x1 hour x3 consecutive days
3. Vaccine bath→ moist heat @ 60°c x I hour x 3 consecutive days
4. Inspissation→ moist heat @80-85°c x I hour x3 consecutive days. Sterilization of egg & serum containing media. Eg. LJ medium, loeffler’s medium.
66
Moist heat sterilization methods at temperature 100°c
1. Boiling
2. Tyndallsation/ fractional sterilization→20min x3 consecutive days
3. Steam sterilizer.
67
Moist heat sterilization at temperature > 100°c
Autoclave
68
Mechanism of action of moist heat sterilization
Denaturation & coagulation of proteins.
69
Methods of pasteurization.
1. Holder method → moist heat @ 63°c x 30 min
coxiella burnetti can survive in this method.
2. Flash method → moist heat @ 72°c x 15-20 sec → to < 13°c → rapid cooling
3. UHT ( ultra high temperature)method → moist heat @ 149°c x 0.5 sec
70
Efficacy testingof pasteusization
1. Coliform test- pasteurized milk + mac conckey broth → overnight → No acid + gas
2. phosphatase test- pasteurized milk + disodium phenyl PO4 →2 hours → No colour change
71
Sterilization of which media by tyndallisation
TCBS, XLD, selenite F broth, sugar solutions, gelatin media.
→ done in Koch & Arnold steam steriliser.
72
Autoclave - principle
Use of saturated steam under pressure.
73
Autoclave- sterilization conditions
1. Moist heat @ 121°c x 15-20 min, pressure = 15 psi
| 2. Moist heat @ 134°c x3 min, pressure= 30 psi
74
Autoclave is used for the sterilization of _
Dressing, linen, non-sharp metallic instruments, aqueous solution, microbiological media, plastic pipettes, tubes.
75
Efficacy testing of autoclave.
1. Physical- temperature chart recorder
2. chemical- Browne's tube no. 1, Bowie dick tapes.
3. Biological - spores of bacillus stearothermophilus
76
Bacterial filters- principle & uses.
→ for heat sensitive liquids.
| →sera, antibiotic solutions, vaccines, sugar/ urea solution, gelatin media
77
Pore size & efficacy testing of standard bacterial fiters.
→ 0.45 u
| → ET- serratia marcescens, brevundimonas diminuta.
78
Types of bacterial filters.
```
1. Earthen wave filters/ candle filters
→ pasture- chamberland filters.
→berkefeld filters.
→ Mandler filters.
2. Asbestos filters.- Seitz filter.
3. Sintered glass filters
4. Membrane filters ( millipore)
5. Air filters - HEPA
6.syringe filters
```
79
Types of radiation sterilization.
1. Non inonizing - uv rays.
| 2. Ionizing - gamma rays,x-rays, cosmic rays.
80
Non ionizing radiation - MOA & uses.
```
→ MOA- DNA damage,
→ wavelength of 220- 280 nm
→poor penetrating power
→non- sporicidal
→disinfection of biosafety safety cabinets, hospital corridors.
```
81
Ionising radiation- MOA & uses.
→MOA- DNA damage
→ gamma rays- cold sterilization.
→ high penetrating power.
→ sporicidal.
→ sterilizations of disposable- gloves, petridish,syringes.
→ iv sets, foley's catheters, sutures, implants,prosthesis, glass ware, fabrics, contraceptive devices, cottonswabs.
82
Name gaseous disinfectants.
1. Formaldehyde gas → operation theater.
2. Ethylene oxide→ beddings, blankets, rubber & plastic objects, disposables, heart lung machine, respirators, dental equipment.
3. Betapropiolactone→ inactivation of vaccines.
83
Tests for testing of disinfectants.
1. Rideal Walker test
2. Chick Martin test
3. Kelsey-Sykes test
4. In- use test.
84
Types of culture media based on physical state
1. Liquid media
2. Semisolid media.
3. Solid media.
85
Types of culture media based on presence of molecular oxygen & reducing substances.
1. Aerobic media.
| 2. Anaerobic media→ cooked meat broth, thioglycolate broth.
86
Types of culture media based on nutritional factors.
1. Simple media.→ Peptone water, glucose broth, nutrient agar.
2. Complex media
3. Synthetic media→ Dubo’s medium with tween 80.
4. Special media.
87
Types of special media with example.
1. Enriched media.→blood agar, Loeffler’s serum slope, chocolate agar.
2. Enrichment media→ tetrathionate broth, selenite F broth, alkaline peptone water, Robertson's cooked meat broth.
3. Selective media →deoxycholate citrate agar, bile salt agar.
4. Differential media → Mac Conkey‘s medium
5. Indicator media → Wilson & Blair medium, Mac conkey's agar, blood agar.
6. Transport media → Venkataraman Ramakrishnan medium, Pike’s medium, Stuart's medium.
7. Sugar media → Hiss’s serum sugars.
88
Enrichment media- imp use.
For culture of faeces where the nonpathogenic bacteria tend to overgrow the pathogenic ones.
89
Selective media - imp use.
To isolate a particular bacteria from specimens where mixed bacterial flora is expected.
90
Transport media- imp use
In case of delicate organisms which may not survive the time taken for transit or may be overgrown by nonpathogenic bacteria.
91
Blood agar- composition & uses.
1. Blood agar→ nutrient agar + sheep blood (5 -10% ). Routine culture
2. chocolate agar → heated blood agar ( 55°c x2 hours). Culture of neisseria, H. influenzae.
92
Methods of anaerobic cultivation ( anaerobiosis)
1. Production of a vacuum
2. Displacement of oxygen
3. By displacement & combustion of oxygen
4. Absorption of oxygen by chemical or biological methods.
5. By reducing agents
6. Anaerobic chamber.
93
Anaerobiosis obtained by _ aerobic jar is the most reliable & widely used method.
McIntosh & Fildels jar.
94
Chemical methods of anaerobiosis.
1. Pyrogallol
2. Chromium & sulphuric acid.
3. Gas-pak.
95
Methods of gene transfer in bacteria.
1. Transformation→uptake of naked DNA
2. Transduction → through bacteriophage.
3. Lysogenic conversion.
4. Conjugation→ plasmid mediated.
96
Types of bacterial conjugation.
1. Simple conjugation.
2. High frequency recombinant conjugation (HFR )
3. R plasmid/ resistance transfer factor
4. Col plasmid.
97
Mutation - definition.
It is a random, undirected heritable variation caused by change in nucleotide sequence of the DNA of the cells.
98
Significance of mutation.
The practical importance of bacterial mutation is mainly in the field of drug resistance & the development of live vaccines.
99
Types of mutation.
1. Point mutation.
a ) base pair substitution →transition
→ transversion.
b ) frame shift mutations
2. Multisite mutation
a) addition
b) deletion
c) duplication
d) inversion
3. Other types
a) induced mutation → enhanced by mutagens
- physical agents → uv light, ionising radiation, visible light, heat.
- chemical agents→ 5-bromouracil, 2-aminopurine, nitrous acid, acridine dyes.
b)nonsense mutation ( UAG, UAA or UGA)
c )missense mutation
d) suppression mutation
100
Transduction.
Bacterial genes are transferred via a phage, from one bacterium to another.
101
Types of transduction.
1. Generalised transduction
→ in lytic cycle
→ due to defective assembly.
→ mediated by virulent or temperate phage.
2.specialised transduction ( restriction)
→following lysogenic cycle
→due to defective excision during induction of prophage
→ mediated by temperate phage.
102
Transposon.
A segment of DNA with one or more genes in the centre & the two ends carrying inverted repeat sequences of nucleotides.
103
Mutational drug resistance.
→ resistance to one drug at a time.
→ Low degree resistance
→ resistance is not transferable to other organisms.
→ mutants may be defective.
→ virulence may be decreased.
→ resistance prevented by treatment with combination of drugs.
104
Transferable drug resistance.
→ R factor mediated.
→ multiple drug resistance.
→ High degree resistance.
→ resistance is transferable to other organisms.
→ mutants not defective
→ virulence not decreased.
→ cannot be prevented by treatment with combination of drugs.
105
Genetic engineering principle.
Plasmid vector + DNA fragment to be cloned → insert DNA into plasmid vector → recombinant plasmid. → introduce RP into E.coli → bacterial cell multiplication → colony of cells containing copies of the same RP
106
Genetic engineering- application in medicine
1. Production of vaccines → hepatitis B, rabies & . B. pertusis vaccines.
2. Production of proteins → human growth hormone, insulin, interferons, interlukin-2, tumour necrosis factor & factor 8.
3. Gene therapy.
107
Restriction endonuleases
→ microbial enzymes which split DNA into fragments of varying lengths.
→ Eco R1, Hind 3, etc.
→ natural functionin bacteria is the destruction of foreign DNA which enter bacterial cell.
108
Zoonotic infections.
→ infectious diseases transmitted from animals to man are called zoonoses.
1. Bacterial → bovine tuberculosis, salmonella food poisoning.
2. Viral → rabies from dogs.
3. Protozoal →leishmaniasis
4. Helmenthic→ Hydatid disease from dogs.
5. Fungal → dermatophytesfrom cats & dogs
109
Carrier.
→A person who harbours the pathogenic microorganism without suffering from its ill effects.
→ very important source of infection to spread the disease in a community.
110
Types of carriers.
1. Healthy carrier→ harbours the pathogen but has never suffered from its disease.
2. Convalescent carrier → recovered from disease but continue to harbour pathogen.
3. Temporary carrier → <6 months
4. Chronic carrier → several years to lifetime carrier.
5. paradoxical carrier →carrier who acquires pathogen from another carrier.
6. Contact carrier → acquires pathogen from a patient.
111
Biological vectors.
→pathogen multiplies in the body of the vector, undergoes part of a development cycle in it.
→ eg. Female anopheles mosquito m malarial parasite, culex mosquito in filarial parasite.
112
Modes of transmission of infection.
1. Contact
a) direct→ contagions disease, STDs
b) indirect→ infections disease, through fomites.
2. Inhalation
3. Ingestion
4. Inoculation
5. Vectors
6. Transplacental
7. Iatrogenic & laboratory infections.
113
Determinants of virulence in bacteria.
1. Adhesion→ fimbriae & pili
2. Invasiveness
3. Antiphagocytic factors
a) capsule
b) streptococcal M protein
c) cytotoxin
d) bacterial surface antigens
4. survival within the phagocyte
a) interference with the oxidative burst.
b) prevention of fusion & degeanulation.
c) resistance to lysosomal enzymes.
d) escape from phagoranes
5. bacterial toxins.
a) endotoxins
b) exotoxins
6. Enzymes
a) Proteases→ cleave ig A
b) kinase
c) hyaluronidase
d) coagulase
e) collagenase
7. Siderophores & iron acquisition
8. Genetic factors → plasmids
9. Infecting dose→ MID, MLD
10. Route of infection
11. Communicability
