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