Microbiology Lab- Exercise 45 Bacteria of the Skin Flashcards


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1

True or false the skin is inhospitable environment for most microorganisms.

true

2

Dry layers of _________ containing cells make up the _______ the outermost layer of the skin an are not easily colonied by microbes.

keratin
epidermis

3

______ secreted by oil glands ________ _______ _______.

sebum
inhibits bacterial growth

4

_______ in ________ create a hypertonic environment.

salt
perspiration

5

Salt and perpsiration are nutritive for certain microorganisms and this estabishes them as part of the _____ _______.

Normal
microflora

6

Normal microflora tends to be ______ to drying and to relatively high ______ ________.

resistant
salt concentrations

7

Bacteria like moist areas such as the _____ and ________.

arm pits (axilla)
sides of the nose

8

________ microflora ar present on hands and arms in contact with the environment.

transient

9

True or false. Despite the adverse environment the microbial population is diverse.

true

10

Recent ribosomal RNA swabbing on the skin of the forehead have identified _____ species of bacteria.

40

11

The most common genera on the skin are ______ and ____________.

Propionibacterium
Staphylococcus

12

Propionibacterium live in _______ on sebum from the oil glands.

hair follicles

13

The propionic acid they produce maintains the ______ of the skin between ____-____ which suppresses the growth of other bacteria.

pH
3-5

14

Most bacteria on the skin are _________ and ____________.

gram (+) and salt tolerant

15

Mannitol salt agar is selective for ________ ___________ and __________ in that mannitol-fermenting organisms will produce __________ turning the indicator _______.

salt tolerant organisms
differential
acid
yellow

16

_________ _________ i considered part of your normal microflora and considered a ________.

Staphylococcus aureus
pathogen

17

S. Aureus which produces _________ an enzyme that coagulates the fibrin in blood and is ______.

coagulase
pathogenic

18

True or false. A test for the presence of coagulase is used to distinguish S. aureus from other species of Staphylococcus.

true

19

Why is MSA used as a selective medium for normal skin microbiota?

Because it i selective for salt tolerant organisms such as Staph

20

List three identifying characteristics of Staphylococcus aureus

gram-positive (purple), catalase-positive (when mixed with hydrogen peroxide it bubbles), and coagulase-positive cocci (clumps)

21

List three factors that protect the skin from infection:

1. the dry layers making up the epidermis are not easily colonized.

2. sebum, secreted by oil glands, inhibits growth

3. salts in perspiration create a hypertonic environment

22

What is coagulase? How is it related to pathogenicity?

Coagulase is a protein enzyme produced by several microorganisms that enables the conversion of fibrinogen to fibrin. In the laboratory, it is used to distinguish between different types of Staphylococcus isolates. Importantly, S. aureus is coagulase-positive, meaning that coagulase negativity excludes S. aureus.

Coagulase reacts with prothrombin in the blood. The resulting complex is called staphylothrombin, which enables the enzyme protease to convert fibrinogen to fibrin. This results in clotting of the blood. Coagulase is tightly bound to the surface of the bacterium S. aureus and can coat its surface with fibrin upon contact with blood. It has been proposed that fibrin-coated staphylococci resist phagocytosis, making the bacteria more virulent. Bound coagulase is part of the larger family of MSCRAMM

23

The microorganisms that establish more or less permanent residence without producing diseases are known as _______ _________.

Normal microbiota (aka microflora)

24

Microorganisms that may be present for just a few days or months are called ____________.

transient microbiota

25

True or false. At one time bacteria and fungi were thought to be plants which why they are referred to as flora sometimes.

true

26

A microorganism that causes disease is called a ________.

pathogen

27

Identifying pathogens is imperative for initiating proper _________ and tracing the sources of the ______.

treatment
infection

28

What are three essentials for identifying the microorganisms in a clinical laboratory?

morphological characteristics
differential stains
biochemical testing

29

Dichotomous keys are essential tools for sorting through lab tests identifying microorganisms in an organized manner. In a dichotomous key identification is based on successive _________ and each one has _____ possible answers.

questions
2 possible answers

30

Dicho means?

cut in two

31

MSA:
S. aureus ferments __________ causing the phenol red to turn ____________.

mannitol
yellow

32

MSA:
S. epidermidis tolerates the high _________ concentration and grows on __________.

salt
mannitol salt agar