Intro To Medical Microbiology

Question 1

Anton von Leeuwenhoek

Answer 1

• Dutch biologist, in 1674
• used his handmade microscope to observe microscopic organisms
• called them “animalcules”

Question 2

Otto Muller

Answer 2

• 100 years after von Leeuwenhoek (~1774)
• Dutch biologist
• organized bacteria by assigning genus and species names to these microorganisms

Question 3

Freidrich Henle

Answer 3

• 1840
• proposed criteria that would provide evidence for germs being the cause of human disease
• germ theory of disease*

Question 4

Robert Koch and Louis Pasteur

Answer 4

-in 1870s and 1880s used Henle’s criteria to show that microorganisms cause anthrax, tuberculosis, plague, and cholera

Question 5

Koch’s postulates

Answer 5

1. Specific organism in should be in all animals suffering a disease and should be absent from healthy animals
2. Microorganism should be isolated from diseased animal and grown in pure culture on artificial lab media
3. Freshly isolated microorganism, when inoculated into a healthy lab animal, should cause the same disease of original animal
4. Microorganism should be re-isolated in pure culture from experimental infection

Question 6

Hans Christian Gram

Answer 6

-1882 developed differential staging technique for staining bacteria called the Gram stain

Question 7

Paul Ehrlich

Answer 7

-in 1910, discovered the first antimicrobial agent, Salvaran, used in the treatment of syphilis

Question 8

Alexander Fleming

Answer 8

-1928, discovered penicillin

Question 9

John Enders

Answer 9

• 1946, first to cultivate a virus in cell culture
• lead the way for others to develop diagnostic techniques for identifying viral causes of disease
• better understood viruses and lead to vaccines

Question 10

A.T. Still

Answer 10

• was not convinced that germs caused human disease and doubted the germ theory of disease
• believed that a healthy body was the best resistance to disease and the body possesses self-healing mechanisms that could resist ALL disease
• was not 100% correct

Question 11

What do antimicrobial agents do for a patient with an infectious disease?

Answer 11

• Antimicrobial agents lower the microbe number and buy the patient time so that the patient’s own immune system can effect a cure

Question 12

Microbes and Microbial forms that are difficult to kill?

Answer 12

• Bacterial and fungal spores
• Mycobacteria
• Naked viruses
• Prions
• High microbial burden

Question 13

Sterilization

Answer 13

-total destruction of ALL microorganisms

Question 14

Moist heat

Answer 14

• boiling (kills vegetative cells).
• autoclave (steam under pressure) also kills spores: 121-132*C, 15 min or more
• -Prions-boil in 1 N NaOH for 10 min followed by extended autoclaving

Question 15

Dry heat

Answer 15

• oven
• 2-3 hours at 170*C
• kills spores (oxidation of cell components), but may leave pyrogens

Question 16

Filtration

Answer 16

• HEPA filters
• remove microorganisms
• not so effective for viruses

Question 17

Radiation

Answer 17

• germicidal UV, ionizing (gamma)

- produces DNA damage, blocks replication

Question 18

Ethylene oxide gas

Answer 18

• toxic alkylating agent used for sterilizing heat-sensitive materials
• toxic or mutagenic by-products must be dissipated

Question 19

Plasma gas

Answer 19

• Hydrogen peroxide is vaporized, then microwave of radio wave frequency is used to produce reactive free radicals
• no toxic by-product residue
• has replaced ethylene oxide in hospitals

Question 20

Chlorine dioxide gas

Answer 20

• denatures proteins by oxidation

- less toxic than ethylene dioxide

Question 21

High level disinfection

Answer 21

Hydrogen peroxide: at 3-6% kills most bacteria; 10-25% kills spores

Question 22

Intermediate level disinfection

Answer 22

• alcohols, phenolic compounds for semi-critical instruments (laryngoscopes)
• spores and Mycobacteria are not killed, most other organisms are killed

Question 23

Low level disinfection

Answer 23

• quaternary ammonium compounds’ used to non-critical instruments (stethoscope)
• many organisms survive, may be effective for killing certain pathogens

Question 24

Pasteurization

Answer 24

(62. 8-65.6*C, 30 min)

- used to extend the self life of products where heat sterilization may be undesirable (milk)

Question 25

Alcohols for antisepsis

Answer 25

• kills most organisms including mycobacteria, but not spores
• non-toxic to skin by has a drying action
• more effective with water, thus 70% is more effective than 95%

Question 26

Iodophors for antisepsis

Answer 26

• carrier of iodine, which is the reactive agent precipitating or oxidizing proteins
• kills most organisms, used with iodine for skin disinfection, a little toxic to skin, but has some residual antiseptic ability
• Povidone iodine is a common stable, nontoxic agent for skin and tissues

Question 27

Chlorhexidine

Answer 27

• slower killing, but residual action

- Cl is a powerful oxidant (replaced hexachlorophene)

Question 28

Phenolic compounds

Answer 28

• attacks lipid membranes, effective against mycobacteria

- action improved by halogens (hexachlorophene)

Question 29

Phenol coefficient

Answer 29

• rating scheme for antibacterial agents

- 5 means 5 times as effective as phenol

Question 30

Quaternary ammonium compounds

Answer 30

-4 organic groups linked to nitrogen, attacks membranes but not very effective against a variety of organisms (ex: Pseudomonas, viruses, spores, mycobacteria)
Example is benzalkonium chloride