MLT104 Test Chapters 1-2

List the four types of forms or margins when describing a colony type:

1. Filamentous 2. Irregular 3. Smooth 4. Rough

List the five types of descriptions for colony elevations:

1. Raised 2. Flat 3. Umbilicate (depressed middle) 4. Convex 5. Umbonate (raised middle)

What mechanism allows strict anaerobes to grow in the crevices and areas between the teeth when plaque is present? a. A low oxidation-reduction potential occurs at the tooth surface. b. The bacteria secrete sugar to nourish the strict anaerobes. c. The normal florae secrete antibiotics to kill all the other bacteria and allow the strict anaerobes to thrive. d. The plaque-causing bacteria secrete an alkaline fluid and change the pH around the tooth.

a. A low oxidation-reduction potential occurs at the tooth surface. (Low oxidation-reduction potential= low chances of addition or removal of oxygen; little oxygen present around teeth with plaque).

Diabetics may sometimes be infected with their own resident florae. This type of infection is called:

a. An opportunistic infection

This type of bacteria is able to live in the colon with little to no oxygen and is the predominant organism:

a. Anaerobes (Specifically, obligate anaerobes like Bacteriodes, Clostridium, Prevotella and Porphyromonas. These far outnumber the faculative gram-negative bacilli, making up more than 90% of the microbial biota of the large intestine).

The outer cell wall of the gram-negative bacteria serves three important functions, which all include the following EXCEPT: a. It provides an attachment site for the flagella, which will act in locomotion. b. It acts as a barrier to hydrophobic compounds and harmful substances. c. It acts as a sieve. d. It provides attachment sites that enhance attachment to host cells.

a. It provides an attachment site for the flagella, which will act in locomotion. (The gram-negative cell wall contains porin proteins that acts as a sieve to allow water-soluble molecules through into the cell. It also has antigen O that acts as a target to host cells.)

Healthy skin secretes these substances to help prevent colonization by transient and possibly pathogenic organisms. a. Long-chain fatty acids b. Bacteriostatic substances c. Sebaceous glands d. Antibodies

a. Long-chain fatty acids

This is a leukocidin that is lethal to leukocytes and produced by staphylococci.

a. Panton-Valentine

This state occurs when a host sheds a disease-causing organism, but does not show signs of disease.

a. carrier

What process is an anaerobic process carried out by both obligate and faculative anaerobes? a. fermentation

a. fermentation

Mycobacterium have a gram-positive cell wall structure with a waxy layer containing two compounds: a. glycolipids and mycolic acid b. glycolipids and phospholipids c. mycolic acid and lipopolysaccharides d. lipodpolysaccharides and phospholipids

a. glycolipids and mycolic acid (Mycobacterium and Nocardia have an acid-fast cell wall, meaning it is highly hydrophobic (more than 60% of cell wall is lipid) and thus hard to stain. Carbolfuchsin is used to stain acid fast walls.)

The laboratory receives a specimen in which the doctor suspects that the infecting organism is Haemophilus influenzae. This organism grows best in an atmosphere that contains 5% to 10% carbon dioxide. It is classified as what type of bacteria? a. Obligate anaerobe b. Capnophillic c. Faculative anaerobe d. Obligate anaerobe

b. Capnophillic

The Gram stain is a routine stain used in bacteriology to determine gram-positive and gram-negative bacteria based on the: a. Phenotypic characteristics of the organism b. Composition of the bacterial cell wall c. Composition of the bacterial cell membrane d. Composition of the bacterial pili

b. Composition of the bacterial cell wall

The three regions of the lipopolysaccharide include all of the following EXCEPT: a. Antigenic O-specific polysacccharide b. Mycolic acid c. Core polysaccharide d. Endotoxin (inner lipid A)

b. Mycolic acid

One of the most effective defenses bacteria have against phagocytosis is: a. Enzymes b. The capsule c. Plasmids d. Liposaccharide layer

b. The capsule

Mycoplasma and Ureaplasma spp. must have media supplemented with serum or sugar because: a. Their cell walls contain only peptidoglycan. b. They lack cell walls. c. The sterols in their cell walls are soluble in normal bacterial media. d. Their cell walls contain detoxifying enzymes.

b. They lack cell walls. (Mycoplasma and Ureaplasma spp. lack cell walls and contain sterols in their plasma membrane. Because they lack the rigidity of the cell wall, they are seen in various shapes referred to as being pleomorphic. Some gram-positive and gram-negative cells can lose their cell walls and grow s as L-forms in media supplemented with serum or sugar to prevent osmotic rupture of the cell membrane.)

In the laboratory, the clinical microbiologist is responsible for all the following EXCEPT: a. Isolating microorganisms b. diagnosing diseases in patients c. identifying microorganisms d. analyzing bacteria that cause disease

b. diagnosing diseases in patients

Organisms that take place in a biological relationship where both benefit from one another are called:

b. symbionts

Parasitism is:

c. A biological relationship in which one species gains benefits at the expense of the host.

What is the purpose of a capsule? a. Prevent osmotic rupture of the cell membrane. b. Make up the periplasmic space. c. Act as a virulence factor in helping the pathogen evade phagocytosis. d. Provide an attachment site for somatic antigens.

c. Act as a virulence factor in helping the pathogen evade phagocytosis.

A patient with an indwelling catheter develops a fever and lethargy. In addition, the urine in the catheter bag has turned a brownish color and is foul smelling, which indicates an infection. What type of infection does this describe? a. Opportunistic b. Pathogenic c. Iatrogenic d. Parasitic

c. Iatrogenic

If bacteria utilize various carbohydrates for growth, it is usually detected by:

d. Acid production and change of color from the pH indicator.

In what staining procedure does carbolfuschin penetrate the cell wall through heat or detergent treatment? a. Gram stain b. Acridine orange stain c. Endospore stain d. Acid-fast stain

d. Acid-fast stain (Examples of bacteria with acid fast cell walls: Mycobacterium and Nocardia).

Select the best description of a suboptimal sample for microbiology: a. Specimens receive in wrong preservative b. Specimens dried out on swab c. Inappropriate container or leaked sample d. All of the above

d. All of the above

Healthy people are colonized by many different bacteria in many different sites. These bacteria are referred to as:

d. Indigenous flora

What stain is used to stain medically important fungi? a. Methylene blue b. Acridine orange c. Acid-fast d. Lactophenol cotton blue

d. Lactophenol cotton blue (Methylene blue is used in Gram Stain. Acridine orange is a flurochorme dye that stains all gram-positive and gram-negative cell walls; living or dead. Acid-fast stains include auramine-rhodamine (flurochrome)or carbolfuschin).

When performing a Gram stain on a gram-negative organism, the crystal violet is absorbed into this outer cell wall layer, then washed away with the acid alcohol. What is the main component of the outer layer of the cell wall? a. Peptidoglycan b. Mycolic acid c. N-acetyl-d-muramic acid d. Lipopolysaccharide

d. Lipopolysaccharide (Gram-negative cell walls are mainly made of lipopolysaccharides. This is unique to gram-negative cell walls, and it contains 3 regions: Antigenic O, the core polysaccharide, and lipid A. Lipid A is an endotoxin that causes fever and shock.)

The stomach can be considered the first line of defense against microbial infections because:

d. Most microorganisms are susceptible to the acid pH of the stomach.

When the bacteria are growing, they go through a log phase when: d. The bacteria numbers increase logarithmically

d. The bacteria numbers increase logarithmically

This constituent of a gram-positive cell wall absorbs crystal violent but is not dissolved thus giving the gram-positive cell its characteristic purple color: a. mycolic acid b. cholesterol c. carbolfuschin d. peptidoglycan

d. peptidoglycan