Microbiology--Clinical Rotation Quizzes

Bordet-Grengou medium is used as a primary isolation medium for __________.

Bordetella pertussis

Which Chlamydia species causes parrot fever?

C. psittaci

Which of the following conditions is NOT associated with Staphylococcus aureus?

Sub-acute endocarditis

Of the following, which media is NOT used to isolate Mycobacterium tuberculosis?

Boiled Thioglycolate broth

Which of the following is NOT consistent with Streptococcus pneumoniae?

Positive catalase test

Which of the following is NOT considered normal flora on the skin?

Streptococcus pyogenes

What media is used for the selective isolation of Neisseria spp.?

Modified Thayer Martin

Falsely decreased zone diameters on a Kirby-Bauer agar disk diffusion test would most likely result from:

A 2 hour delay in placing the antimicrobial disks on the seeded plate

Loeffler's medium is used as a primary isolation medium for:

Corynebacterium diphtheriae

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

Large, flat colony with a double zone of hemolysis

The infective stage of this parasite consists of an egg with a thin hyaline shell and one flattened side and, usually, a fully developed larva within. Eggs are collected and viewed by using cellulose tape. The parasite is:

Enterobius vermicularis (pin worm)

Inhibitory media is also called:

Selective

"Diphtheroides" is a common name for the nonpathogenic members of which genus?

Corynebacterium

Specimens for viral culture should be transported in:

Nutrient medium (like Stuart's medium) with antibiotics

CAMPY media is used to grow:

Campylobacter jejuni

What is the cause of both Chicken pox and shingles?

Varicella-zoster virus

If a bronchial wash from a patient with pneumonia was sent to the lab, what media would you set up to isolate Legionella spp.?

BCYE (buffered charcoal yeast extract)

Which of the following is true for Taenia solium?

Protoglottids have 13 or less uterine branches

A renal dialysis patient came to the emergency room and was placed on IV antibiotics before the phlebotomist could collect blood cultures. To counteract the antibiotics, the phlebotomist used blood culture bottles with sodium polyanetholsulfonate (SPS) in them. What antibiotics will be inactivated by SPS?

Streptomycin, gentamicin, polymyxin B

At what temperature does Yersinia grow best?

25-30 oC

The second of two blood culture sets went positive after 24 hours of incubation, but the first set that was drawn never did. The technician that worked up the positive blood culture stated that the gram stain and plates indicated contamination. Which of the following organisms is most likely a contaminant?

Corynebacterium sp.

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

A micoraerophilic environment with increased nitrogen gas

E. coli produces blue-black colonies with a metallic green sheen when it grows on what type of media?

EMB

What gram-negative bacteria can produce bloody diarrhea without pus and hemolytic-uremic syndrome (characterized by low platelet counts, hemolytic anemia, and possible kidney failure)?

E. coli O157:H7

Which test indicates that an organism is a slow lactose-fermentor?

ONPG

How do you identify Moraxella catarrhalis biochemically?

Oxidase-positive, does not utilize glucose or maltose, DNase-positive

In molecular testing, what does PCR stand for?

polymerase chain reaction

What is the Gram's stain of members of Letospira, Borrelia, and Treponema?

Helical/spiral gram-negative

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

Deaminates lysine

What type of hemolysis on 5% sheep blood agar is the result of complete lysis of the RBCs?

Beta

A young mother was trying to start her infant on solid foods. Since the baby kept spitting the cereal out, the mother thought the baby didn't like the taste and therefore added some honey to the cereal. Two days later, the mother called her pediatrician concerned by the fact that her baby could no longer grasp anything in its hands or hold its head up. The doctor instructed her to bring the infant to the hospital immediately for food poisoning treatment.

What is the most likely organism that the doctor was concerned about?

Clostridium botulinum

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

Plasmodium

If there are three or more colony types each less than 10,000 CFU/mL, what is the most likely interpretation?

Contamination- no ID or antibiotic sensitivities to follow

What general category of antimicrobial drugs interferes with protein synthesis by binding to the 30s ribosomal subunit?

Aminoglycosides

What is suggested when there are a large number of squamous epithelial cells seen on a sputum gram stain?

Saliva (not a true sputum)

A thick film has been prepared from a patient suspected of having malaria. It is stained with Wright's stain. Inclusions seen in the patient's erythrocytes are described as blue disks with red nuclei. The infected erythrocytes are generally oval and some of them have granules of brownish pigment. Many of the erythrocytes appear to have 8 nuclear masses in a single cell. Identify the parasite described.

Plasmodium ovale

If you are using a 0.01 mL loop, each colony on the urine culture represents how many colony forming units in the urine?

100 CFU/mL

A sputum specimen for culture and STAT gram stain is received on a patient with suspected lobar pneumonia. The gram stain showed rare gram positive cocci in clusters, few gram negative diplococci,

Haemophilus influenzae

When processing sputum specimens for mycobacterium culture, Sodium hydroxide decontaminates the sputum. What is used as a digesting agent to liquefy sputum?

NALC (N-acetyl-L-cysteine)

A clean catch urine specimen from a female with a suspected UTI showed gram positive cocci that were catalase positive, coagulase negative and Staph latex negative. On the Microscan panel, growth in the novobiocin well was noted. The most likely organism is:

Staphylococcus saprophyticus

Oxacillin is used to monitor:

Methicillin resistant Staph aureus

A sputum culture grew many mucoid, lactose-fermenting colonies. The biochemical results are as follows:

TSI: Acid slant/ acid butt, gas, H2S-negative

LIA: K/K, H2S-negative

Citrate: Positive

Urease: Weak positive (2+)

Indole: Negative

Ornithine: Negative

What is the likely organism?

Klebsiella pneumoniae

What Gram positive organism is the most common cause of lobar pneumonia in both adults and children?

Streptococcus pneumoniae

What is the most likely cause of subacute bacterial endocarditis?

Streptococcus viridans

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

Which enzyme is NOT tested for on Egg yolk agar?

Amylase

Which stain is used to visualize intestinal protozoa in their troph or cyst stages?

Trichrome stain

What is the main concern with Vancomycin resistant Enterococcus?

The VRE might pass plasmid DNA containing the resistant gene to other bacteria

Which phase of syphilis shows a high sensitivity for both the nontreponemal tests VDRL and RPR as well as the treponemal test FTA-Abs?

Secondary

Which test uses p-dimethylaminobenzaldehyde to detect tryptophan deamination?

Indole

Which Enterobacteriaceae will produce black colonies on HE agar due to hydrogen sulfide production?

Salmonella

The causative agent of Q fever is:

Coxiella burnetii

Inhibitory media is also called:

Selective

The amount of time required for one cell to divide into 2 cells is called the:

Generation time

Lowenstein-Jensen agar is used to isolate and identify which one of the following genera?

Mycobacterium

Which drug commonly used to treat Mycobacterium tuberculosis interferes with RNA synthesis by inhibiting RNA polymerase?

Rifampin

If a physician suspects duodenal ulcers caused by Helicobacter pylori, what test might he/she order, and what is the expected result?

Rapid urease reaction; positive

Because of the types of infections that are associated with Group B Strep., Group B is commonly tested for in what patient population?

Women about to give birth

The growth medium of choice for the isolation of Bordetella pertussis from a suspected case of whooping cough is:

Bordet-Gengou

Which bacteria have small colonies with narrow zones of beta hemolysis, is catalase positive, and have tumbling motility and an umbrella motility pattern at room temperature?

Listeria monocytogenes

If a urine culture was set up using a 0.001 mL loop and grew 125 colonies, how many colony forming units were in the urine?

125,000 CFU/mL

The trophozoite of which organism is characterized by "falling leaf motility", two nuclei, an axostyle, 4 pair of flagella, a sucker on the underside of the organism, and causes traveler's diarrhea?

Giardia lamblia

Interpret the following MIC. (Θ means growth; O means no growth.)

O0.5

O1

O2

O4

O8

Less than or equal to 0.5

Following the terrorist attacks of 9-11-01, there was an increased concern of anthrax exposure. If you are looking for Bacillus anthracis on a Gram's stain, what morphology are you expecting?

Large positive rods in chains and with spores

Are head lice and pubic lice the same organism?

No. The two body sites are infected by different types of lice

What does a colony of Bacteroides fragilis look like on Bacteroides bile esculin (BBE) agar?

Large, gray colony that turns the media a brown to black color

Sterilization (killing of all organisms) can be accomplished by all of the following EXCEPT:

Filtration as long as the filter's pore size is < 22 µm

Which organism is normal flora of the vagina?

Lactobacillus

What is the specimen transport media used to recover Salmonella, Shigella, Vibrio cholerae and Campylobacter?

Cary-Blair medium

What makes up a gram positive organism's cell wall?

thick peptidoglycan layer

What is the name of the chronic, granulomatous, infectious disease that produces sinus tracts and fistulae containing pus with sulfur granules?

Actinomycosis

_____________is the method in which the DNA segment of interest is identified when a complementary and labeled probe binds to it.

Nucleic acid hybridization

What is the usual percentage of blood used in preparing sheep blood agar plates?

5%

An acid-fast bacillus (AFB) has been isolated form the sputum of a patient suspected to have a mycobacterium pulmonary disease. The organism is a slow growing isolate that produces cream- to tan-colored colonies when grown in the dark incubator and turns bright yellow upon exposure to light. It is nitrate-positive and semi-quantitative catalase-positive. Which of the following is the most likely identification of this organism?

Mycobacterium kansasii

Which organism is associated with cystic fibrosis patients, prefers

temperatures below body temperature (30oC), is oxidase negative, and

produces yellow, nonwrinkled colonies?

Burkholderia cepacia

Which statement is FALSE about E. coli O157:H7?

Does not have flagella

Of the genus Haemophilus, which species is a pathogen that can be found in a genital culture?

H. ducreyi

Which of the following statements regarding Simmon's citrate agar is

INCORRECT?

Glucose is the carbohydrate in the medium

A lung abscess is cultured. At 24 hours of incubation, no growth is detected on any of the primary, aerobic agar plates. Gram-negative rods are seen in the thioglycollate broth and on anaerobic sheep blood agar. The isolate will fluoresce to produce a brick red color under ultraviolet light, is kanamycin resistant, and is 20% bile and vancomycin susceptible.

What is the most likely ID?

Porphyromonas sp.

What organism would you suspect from this sputum culture after reading the following gram stain?

3+ GNeg Rods

1+ GPos Cocci chains

4+ PMNs

Less than 10 epi per LPF

Klebsiella pneumoniae

Where does Salmonella typhi reside in the "carrier state" of typhoid fever?

Human gall bladder

Which statement best describes Salmonella?

Gram negative rod found in many species causing food poisonings

Which organism does not have a cell wall, is a facultative anaerobe requiring growth media with cholesterol and fatty acids, produces colonies that look like fried eggs, and causes atypical/walking pneumonia?

Mycoplasma pneumoniae

_____________is the method in which the DNA segment of interest is identified when a complementary and labeled probe binds to it.

Nucleic acid hybridization

MacConkey agar is used for the isolation of members of the family

Enterobacteriaceae because the medium is selective and differential. What color are non-lactose fermentors on MacConkey's?

Clear

What organism would you suspect from this sputum culture after reading the following gram stain?

3+ GPos dc

2+ GNeg dc

4+ PMNs

Less than 10 epi/ LPF

Streptococcus pneumoniae

A specimen from a female complaining of vaginitis emitted a "fishy" odor

when mixed with 10% KOH. A wet prep showed some white cells and

epithelial cells covered with small gram variable/negative rods. The specimen grew beta-hemolytic colonies on V agar. The most likely organism is:

Gardnerella vaginalis

Which parasite's diagnostic stage is acid-fast oocysts in stool?

Cryptosporidium

MacConkey agar is used for the isolation of members of the family

Enterobacteriaceae because the medium is:

selective and differential

Bacteria are able to pass little bits of DNA back and forth to each other which can result in multi-drug resistant bacteria. What drug is the majority of Enterococcus still sensitive to, but whose susceptibility is still closely monitored by the medical community?

Vancomycin

Which of the following characteristics is NOT used to characterize

Staphylococcus aureus?

"Pitting" on sheep-blood agar

What percentage of the original concentration of organisms is killed by the minimal bactericidal concentration of an antibiotic?

99.9%

Which genus of gram positive rods is a member of our skin's normal flora?

Corynebacterium

The color of a nonacid-fast bacillus is:

Blue

The L-pyrolidonyl-betat-naphthylamide (PYR) hydrolysis test is a presumptive test for which one of the following Streptococci?

Group A and Enterococcus

What organism would you suspect from this sputum culture after reading thefollowing gram stain?

3+ G = cb

2+ G+ cocci

4+ PMNs

< 10 epi/ LPF

Haemophilus influenzae type b

Neisseria species can be identified and differentiated by:

Carbohydrate utilization

In the Bactec blood culture system, how are organisms detected?

By the production of carbon dioxide

Which of the following is used to produce an anaerobic environment?

Gas pack jar

What is the term used to describe when bacteria are alive, but cease to grow and divide?

Bacteriostatic