Parasitology IV Microbio Lab 11 & Chemical Methods of Microbial Control

Round Worms

1. Cylindrical, non

segmented worms

2. Sex organs on separate

worms

3. No hooks or suckers to

attach to host

4. Inhabit the intestinal

tract, blood, organs,

tissues

Flat Worms

1. Flat body shape

2. May be

hermaphrodites

3. Have hooks/ suckers to

attach to host

4. Inhabit intestinal tract,

blood, organ tissues

Taenia saginata

• MOT - Eating undercooked beef with cysticerci

• Infective stage - Cysticerci

• Hosts - D - Human, I - Cattle

• Disease - Taeniasis

Taenia solium

• Mode of Transmission: Eating undercooked pork with cysticerci

• Infective Stage: Cysticerci

• Hosts: D-Human, I-pig

• Disease: Taeniasis

Taenia saginata

Taenia solium

Diphyllobothrium latum

• Mode of Transmission: Eat fish with cysticerci

• Infective Stage: cysticerci

• Host: D- human, I-fish

Echinococcus granulosus

• Mode of Transmission: Ingestion of egg/ova

• Infective Stage: Egg

• Host: D-Canine, I-human, sheep, cattle

• Disease: Hydatid Cysts

Chemotherapeutic drug

Any chemical used in the

treatment, relief, or prophylaxis of a disease

Prophylaxis

use of a drug to prevent potential infection

in a person at risk

Antimicrobial chemotherapy-

the use of

chemotherapeutic drugs to control infection

Antimicrobials

any antimicrobial drug, regardless of its

origin

Antibiotic

a substance produced by microbes that can

inhibit growth or destroy other microbes

• Many synthesized antibiotics are based on natural antibiotics

Semisynthetic Drugs

compounds chemically modified in

the laboratory after being isolated from natural sources

Synthetic Drugs

compounds synthesized entirely in the

laboratory through chemical reactions

Minimum Inhibitory Concentration

Lowest concentration of an antibiotic that prevents

visible bacterial growth

• Test can be done instead of Kirby Bauer

Kirby-Bauer Method

Few antibiotics work equally well against all types of

bacteria

• Uses antibiotic containing disks to test whether

particular bacteria are susceptible to specific antibiotics

• Determines the effectiveness of multiple antibiotics at

the same time

• Highly Standardized method

Kirby-Bauer Antibiotic Sensitivity Test

Standardized procedure for the Kirby-Bauer test:

Media: Mueller-Hinton agar (must be 4 mm deep)

• Media pH: 7.2-7.4

• Amount of Bacteria: 0.5 McFarland Turbidity Standard

• 150 million bacterial cells/ml of liquid

• Age of Culture for Set-up: 2-6 hours old

• Times plates are Incubated: 18-24 hours

• Temperature of Incubation: 35-37°C

• Spreading Technique: Bacterial Lawn

Kirby-Bauer Antibiotic Sensitivity Test

what does the Kirby-Bauer Antibiotic Sensitivity Test measure?

Measures the zone of inhibition (mm)

• Circular area around the antibiotic disk

• Measured Zones of Inhibition are compared to a

chart supplied by the manufacturer

• Determines if bacteria are sensitive or resistant

to the antibiotic

• All labs that do this test must follow the

same standards

Measure Diameter in Millimeters

Resistant

antibiotic has no effect on the

bacteria

intermediate

antibiotic is only moderately

effective against the bacteria

sensitive

antibiotic is effective against the

bacteria (prevents growth)

Effects of Antibiotics on Bacteria

Broad Spectrum antibiotics: Effective against a large

range of bacteria

• Example: Gram-Positive and Gram-Negative Bacteria

• Narrow spectrum antibiotics: Effective against a

small group of bacteria

• Example: Effective against only Gram-Positive Bacteria

• Bactericidal-kills bacteria

• Bacteriostatic-inhibit reproduction of bacteria,

allows immune system to eliminate them

Broad Spectrum antibiotics:

Effective against a large range of bacteria

• Example: Gram-Positive and Gram-Negative Bacteria

Narrow spectrum antibiotics:

Effective against a

small group of bacteria

• Example: Effective against only Gram-Positive Bacteria

Bactericidal

kills bacteria

Bacteriostatic

inhibit reproduction of bacteria,

allows immune system to eliminate them

General Actions of Antibiotics

1. Cell membrane

2. DNA / RNA