Microbiology

In a broth dilution method of antimicrobial susceptibility testing, the tube with the lowest concentration of antimicrobial in which their is no visible growth is the minimal

Inhibitory concentration

In an iodine preparation of feces an amoebic cyst appears to have a single nucleus with a large karyosome and chromatin bodies do not appear along the nuclear membrane. A large glycogen mass that stains reddish brown occupies the cytoplasm. The most probable identity of the cyst is

Iodamoeba butschlii

A discharge from an infected ear grows a colorless colony type on MacConkey agar that swarms on sheep blood agar. This oxidase negative, gram negative rod is most likely

Proteus mirabilis

The X and V factors required for growth Haemophilus influenza are contained in

chocolate agar

A 43 year old female patient complains of a very sore throat. the throat swab that is submitted for routine culture grows a variety of diptheroids, alpha, beta and non hemolytic streptococci; staphylococci and Neisseria. The next step is to:

identify the beta-hemolytic streptococcus species

A urine is received in the laboratory for culture. If the specimen cannot be plated immediately, it should be held:

in the refrigerator

Standardized testing conditions for the Kirby-Bauer agar disk diffusion antimicrobial susceptibility test include all of the following except

incubation in 8-10% CO2

MacConkey agar is used for the isolation of members of the family Enterobacteriaceae because the medium is

inhibitory and differential

After 48 hours of incubation on anaerobic sheep blood agar, Clostridium perfringens appears as a

large, flat colony with a double zone of hemolysis

Safety precautions designed to minimize laboratory acquired infections when working with Mycobacterium tuberculosis in a clinical laboratory would prevent spreading of these organisms by

Aerosol production

Chlamhydiae differ from viruses in that chlamydiae

Are bacteria

A fungal colony grows rapidly on Sabouraud's dextrose agar as a white colony type with a dense production of aerial, blue-green spores. On lactophenol cotton blue preparation, swollen-tipped conidiophores bear steringmata and conidiophores in chains. The most likely identification of this isolate is

Aspergillus

Which of the following characteristics is not used to characterize Staphylococcus aureus?

"pitting" on sheep blood agar

A specimen for viral culture is collected on a Friday and must be held for processing until the next day. In general, the optimal temperature for holding this specimen is

4 degree Celsius

Routine sterilization of artificial culture media by autoclaving is recommended by:

15 psi at 21 degree Celsisus for 15 minutes

To eliminate the antibacterial properties of blood and simultaneously introduce an adequate volume of blood for recovery of microorganisms from septicemia, the recommended blood to broth ratio in the blood culture bottle is approximately:

1:10

A potentially pathogenic yeast that is normal flora in the oropharyngeal cavity and may produce thrush is

Candida albicans

Which of the following pairings of yeast species with identifying characteristics is (are) correct?

Candida albicans: germ tube positive, chlamydoconidia producer

The function of 10% potassium hydroxide in the direct examination of skin, hair, and nail scrapings is to

Clear and dissolve debris

This adult disease results from preformed neurotoxin that is ingested and causes the symptoms of neuromuscular flacid paralysis. The agen that produces the toxin is

Clostridium botulinum

The direct iodine preparation is best used to detect protozoan

Cysts

The infective stage of theirs parasite consists of an egg with a thin hyaline shell, with one flattened side and usually, a fully developed larva within. The parasite is

Enterobius vermicularis

The pair of organisms that would provide a good positive and negative control for PEA blood agar is

Enterococcus and E. coli

Which of the following descriptions does not pertain to Pasteurella multocida?

Growth on MacConkey agar

A procedure that directly determines beta lactamase production by a microorganisms is based on the detection of a (an)

Increased acidity due to the release of penicilloic acid

A mucoid, lactose positive colony type on Mac Conkey agar that is indole negative and citrate positive and non motile is

Klebsiella pneumoniae

A small gram positive rod that cause neonatal meningitis and septicemia is

Listeria monocytogenes

Which result is not consistent with the identification of Mycobacterium fortuitum?

Nitrate reduction negative

Norcardia species that cause no radios is often are

Partially acid fast

Parasites that are detected by direct visualization in a peripheral blood smear are

Plasmodium

A gram negative rod is isolated from a patient with second and third degree burns. The isolate produces a bluish green pigment and a characteristic fruity odor. Other characteristic observations are: Triple sugar iron: K/K Motility: positive Oxidase: positive Oxidative/fermentation glucose: oxidative utilization only The most probable genus of this isolate is

Pseudomonas

A saprobic yeast that inhabits airborne dust skin and mucosa grows rapidly and produces an orange-to-red color. This isolate most likely belongs to the genus

Rhodotorula

On a sheep blood agar plate Haemophilus influenzae satellites around colonies of

Staphylococcus aureus

An optochin disk is a chemical used to differentiate

Streptococcus pneumoniae from alpha-hemolytic streptococci

On thisculfate citrate bile salts sucrose (TCBS) agar, colonies of Vibrio cholerae appear

Yellow

Isolation of Campylobacter jejuni from a patient with gastroenteritis is optimized by

a microaerophilic environment

Neisseria species can be identified and differentiated by

carbohydrate utilization

A pustule drainage submitted for culture is plated onto primary media. After an 18 hour incubation, the seep blood agar plate reveals a predominance of beta-hemolytic, white, porcelain like colonies. Gram stain shows gram positive cocci. the colonies test catalase positive. the most appropriate test for additional identification of the isolate is:

coagulase

The color of a nonacid fast bacillus following the acid alcohol step and before conunterstaining in the acid fast stain procedure is:

colorless

A lysine iron agar (LIA) slant shows a red slant over a yellow butt. This reaction indicates that the organism

deaminates lysine

In the N-acetyl-L-cysteine alkali method of processing sputum specimens for mycobacterial culture, the N-acetyl-L-cysteine serves as a

digestant

Family characteristics of the Enterobacteriaceae include

fermentation of glucose

To differentiate between a coagulase-negative staphylococcus species and a micrococcus species, which of the following tests can be used?

furazolidone susceptibility

Escherichia, Klebsiella, and Proteus species are common flora of the

gastrointestinal tract

A nasopharyngeal culture grows a predominance of beta hemolytic colony type on sheep blood agar at 18 hr. The isolate is susceptible to a 0.04 unit of bacitracin. The most likely identification is beta hemolytic streptococcus,

group A

The specimen of choice for the isolation of Bordetella pertussis from a suspected case of whooping cough is

nasopharyngeal swab

Which of the following specimens is acceptable for the evaluation of clinically important anaerobes?

peritoneal fluid

Which of the following characteristics is not consistent with Streptococcus pneumoniae?

positive catalase test

When acetone-alcohol is inadvertently omitted from the gram stain procedure, streptococci and Neisseria will be stained, respectively,

purple and purple

A sputum specimen is submitted to the laboratory accompanies by a request for an AFB culture. All of the following are standard protocol for processing this specimen except;

use of concentrated potassium hydroxide for decontamination procedure