Study Guide for Lab Exam 2

What is the purpose of spread plating?

To create isolated colonies by spreading microbial sample evenly over agar surface. Or to create bacterial lawn.

What are the differences between streak plating and spread plating?

In streak plating, you’re flaming the inoculating loop between each streak, making four streaks to decrease the number of microorganisms.

In spread plating, you’re using water in a microbial sample in addition to a glass rod to dilute the amount of microorganisms for each plate.

What is the zone of inhibition?

Clear zone around disk where bacterial growth is inhibited.

How does the antibiotic get into the agar?

Diffusion

What is the purpose of an antibiotic susceptibility test?

Test the effectiveness of antibiotics against Staph. aureus and E. coli.

What is the purpose of the Snyder test? How do you interpret the results?

Measures susceptibility to dental caries(tooth decay). Favors growth of oral bacteria. Media contains pH indicator Bromocresol Green.

At a pH of 4.8 or higher, the media is green.

At a pH lower than 4.8, media will turn yellow.

Check tubes for color change at 24, 48, and 72 hours.

What is a biofilm?

complex association of 2 or more microorganisms that secrete an extracellular matrix and adhere to a surface.

What is the purpose of clinical biofilm experiment?

Tests for biofilm formation by Staphylococcus species.

What is a nosocomial infection?

Healthcare associated infections

Why were Staph. aureus and Staph. epidermis chosen for the clinical biofilm experiment?

1. Cause biofilms on medical equipment leading to hospital-acquired infections.

2. Both organisms are always present on skin.

What does MMWR stand for?

Morbidity and Mortality Weekly Reports.

What are MMWR?

The CDC collects weekly data on the occurrence of 26 notifiable diseases in the U.S. and its territories.

What is Morbidity?

number of susceptible people who have the disease within a defined population during a specific period of time (prevalence).

What is Mortality?

number of people who die from a specific disease out of the total afflicted with that disease in as specified time period.

What is incidence rate?

Occurrence of new cases of disease within a defined population during a specific period of time.

What is the incidence rate equation?

= number of new cases in a time period / size of at risk population at midpoint of time period x K

What is the purpose of epidemic simulation?

Identify the index case and explain the route of transmission.

What is R0?

Basic reproduction number , represents number of people that a single infected person will transmit the disease to. Accounts for infectious period, mode of transmission, and contact rate.

Saccharomyces cerevisiae

Important in the production of bread, wine, and beer.

Classification is division ascomycota.

Candida albicans

Most common fungal opportunistic pathogen, part of normal flora. Classification is ascomycota.

Rhizopus

Common in soil and decaying organic matter, found worldwide.

Causes zygomycosis and classification is zygomycota.

Penicillium

Produces antibiotic penicillin. Causes disseminated opportunistic infections of lungs, liver, and skin. Classification is Ascomycota.

Aspergillus

Opportunistic pathogen that causes aspergillosis. Important commercially in the production of sake, soy sauce, citric acid. Classification is Ascomycota.

Entamoeba histolytica

Causative agent of amebic dysentery. Belong to Ameobozoa.

Balantidium coli

Causes balantidiasis (GI infection). Belongs to alveolates.

Giardia Lamblia

Causes giardiasis (GI infection) belongs to diplomonadida

Trichomonas vaginalis

Causes trichomoniasis, a sexually transmitted disease. Belongs to parabasala.

Trypanosoma

Causes African sleeping sickness. Belongs to Euglenozoa.

Plasmodium

Causes malaria, belongs to alveloates

Schistosoma Mansoni

Found in tropical environments (Brazil, Caribbean, Africa, Middle East). Infection occurs through the skin via contact with fecally contaminated water.

Dipylidium caninum

Formerly taenia dipylidium. Tapeworm infection in dogs and cats, mostly in children.

Scolex: suckers and hooks

Proglottid: contains reproductive structures.

Ascaris lumbricoides

Human infection occurs when contaminated soil or food are ingested.

Necator Americanus

Infection

1. Juvenile hookworms penetrate skin.

2. Enter the blood stream

3. Travel to the lungs

4. Ciliary action moves worm up and out of lungs into pharynx.

5. Worms swallowed into digestive tract, where they attach lining of the small intestine.

How do you determine if an organism is susceptible or resistant to an antibiotic?

Performing the antibiotic susceptibility test.