Microbiology LabCE

This image demonstrates which of the following forms of Plasmodiumspecies:

Ring forms

Which of the following statements is true about the emergence of penicillin-resistant strains of Streptococcus pneumoniae?

A zone size of = 20 mm with the oxacillin disk screen must be confirmed with an MIC method to determine if Penicillin is susceptible or resistant.

The four mycobacteria shown have been cultured on Middlebook agar and include the duration of their incubation. Which of the organisms is most characteristic of the growth seen with Mycobacterium kansasii?

B

The amoeba that inhabits the gumline of the mouth is known as:

Entamoeba gingivalis

Which one of the following organisms can be isolated from bone marrow specimens?

Histoplasma capsulatum

With the widespread use of the pneumococcal vaccine, there has been a decline in the incidence of community-acquired pneumonia by which of the following organisms?

Streptococcus pneumoniae

Complete hemolysis of sheep blood agar as demonstrated by the image below would be seen in which of the following catalase-negative isolates?

Streptococcus pyogenes

The bacterium in the image to the right is also referred to in the quote below, what is the identification of this bacteria? "If a pregnant woman be attacked by erysipelas of the womb, it is fatal." - Hippocrates

Streptococcus pyogenes

Aspiration material recovered from a ruptured appendix abscess was inoculated to anaerobic culture media per laboratory protocol. Gray colonies (> 1 mm) grew anaerobically in 24 hours on BBE agar, blackening the media. The photograph illustrates the gram stain features of the organism. The bacterial species most likely associated with the abscess is:

Bacteroides fragilis group

The following is the term used to describe the total clearing of the agar surrounding colonies on a blood agar plate as seen in this illustration:

Beta Hemolysis

What parasite's trophozoite form ingests white blood cells, measures approximately 5 - 15 µm, and typically resides in the mouth?

Entamoeba gingivalis

The morphology of this cyst resembles Entamoeba histolytica, but lacks ingested red blood cells in its trophozoite form. What is this organism?

Entamoeba hartmanni

This 30 X 50 µm ovum is most commonly observed by the microscopic examination of transparent adhesive tape mounts of perianal skin from children complaining of nocturnal anal pruritus. What is the most likely presumptive identification?

Enterobius vermicularis

5% sheep blood agar will support the growth of most strains of the following organisms, EXCEPT:

Haemophilus spp.

The parts of the prototypical bacterium in the image to the right are identified below. Which of the following is incorrectly identified?

A - cytoplasmic membrane

What are the four nitrogenous bases found in RNA?

Adenine, guanine, cytosine, and uracil

The microscopic illustration demonstrates the golden-brown pigmented conidia and macroconidia of the following mold:

Alternaria

This suspicious form measuring 15 µm was recovered from a stool specimen. Which of the following conditions is associated with this organism?

Amebiasis

This colony grew after 4 days of incubation at 30° C. on Sabouraud's dextrose agar, as shown in the upper image, and was recovered from induced sputum from a 45-year-old construction worker who presented with an X-ray evidence of a lung abscess. This light green colony has a cottony surface, shallow rugae, and a white surrounding apron. The Lactophenol cotton blue stain microscopic appearance from the surface colony is illustrated in the lower image. From these observations select the fungal species.

Aspergillus fumigatus

Which of the following organisms display the characteristic "Medusa head" on 5% sheep blood agar (SBA) after 18 hours of incubation at 35°C?

Bacillus anthracis

The colonies seen in the upper frame, grown after 48 hours of incubation aerobically at 35°C, and the accompanying Gram stain in the lower frame are of an organism uncommonly associated with human disease; however, this organism has been associated with septicemia, bronchopneumonia, osteomyelitis and other infections, particularly in intravenous drug users. What is the most likely identification of the organism?

Bacillus circulans

The recovery of Mycoplasma hominis from the genital tract of females has been associated with all of the following clinical syndromes EXCEPT:

Bronchitis

Which of the following stains is commonly used to stain chitin in fungal cell walls?

Calcoflur-white stain

The following statements regarding automated identification systems are correct EXCEPT:

Can reliably identify Francisella tularensis

The smooth and pasty appearing 72-hour yeast colonies growing on blood agar shown in the upper image are non-specific and further studies must be performed to make the identification. One of these studies is a cornmeal agar preparation as illustrated in the bottom photomicrograph in which tiny, uniform, spherical cells are arranged in tight clusters. This yeast is commonly recovered from urinary tract infections. Select the most likely yeast isolate.

Candida glabrata

Which of the following is the primary virulence factor in Streptococcus pneumoniae?

Capsular polysaccharide

A tech is working with a small Gram-negative coccobacillus that may be Francisella tularensis. Which of the following tests could the tech use to rule out this organism?

Catalase negative

Which of the following test is the most useful in differentiating Listeria monocytogenes from Erysipelothrix rhusiopathiae?

Catalase production

Methicillin-resistant Staphylococcus aureus (MRSA) is a serious health concern in the hospital environment and also in the community for patients who have had no contact with the healthcare setting. In order to control the spread of MRSA and prevent infection with the organism, it is recommended to screen patients for MRSA prior to being admitted to a healthcare setting. Which of the following antimicrobials is best to use when testing for methicillin resistance?

Cefoxitin

The images to the right are from a 4-day-old colony grown on Sabouraud's Dextrose agar (left image). It was recovered from what was considered a "contaminant" from a bacterial culture. The image on the right is a high power photomicrograph of a methylene-blue stained mount prepared from the surfaces of the colony. With these observations, select the fungus genus from the choices below.

Chrysosporium

This form measuring 30 µm by 15 µm was found in stool specimen. What is its identification?

Clonorchis sinensis egg

The top image shows a 5-day-old colony grown on blood agar and incubated at 30o C. It has a delicate cobweb-like, gray-white mycelium. Note the dark gray discoloration on the upper margin where hemoglobin pigment has been absorbed. This colony was recovered from the needle biopsy of a lung nodule that developed three months after a 45-year-old businessman returned from a business trip in Southern California. The definitive identification can be made microscopically from the observation of the distinctive hyphae as presented in the lactophenol blue mount shown in the bottom image. From these observations, select the presumptive identification of this isolate from the choices listed below.

Coccidioides immitis

The disease most commonly associated with the novobiocin-resistant staphylococcus illustrated in this photograph is:

Community-acquired urinary tract infection

The modified acid-fast stain is primarily used to identify:

Cryptosporidium oocysts

Illustrated in the top image is a circumscribed three-day-old colony growing on Sabouraud's dextrose agar recovered from nasal washings of a patient with sinusitis. The colony with a dark green-gray, wooly surface mycelium is not exclusive. Gray-black pigment would be observed on the reverse side. Species identification must be made microscopically. Illustrated in the bottom image is the appearance of a tease mount made from the surface of the colony. From these observations, what is the identification of this fungal isolate?

Curvularia species

Adult intestinal roundworms possess this structure that serves as a protective outer layer:

Cuticle

The following Clostridioides difficile virulence factor is significant in the cause of antibiotic-associated pseudomembranous colitis:

Cytotoxin A or B

The tubes shown in this photograph reading from left to right are Kligler Iron Agar (KIA), tryptophane broth for detecting indole and Simmon's citrate. The KIA tube shows an entirely yellow slant and butt, the indole tube shows a layer of red color, and the Simmon's citrate tube is green in color. Of the bacterial species listed, the one most likely to produce the reactions observed is:

Escherichia coli

Which Enterobacteriaceae is the most common cause of uncomplicated urinary tract infections (UTIs)?

Escherichia coli

Houseflies are a possible transport host for which category of parasites?

Flagellates and amebae

Which bacterial genus contains fastidious, facultative intracellular, gram-negative bacilli that causes a zoonosis called tularemia?

Francisella

All of the following parasites are appropriately matched with its respective means of motility, EXCEPT:

Giardia sp. - no locomotion

The reactions in the tubes illustrated in this exercise (reading from left to right: TSI, Pseudosel, OF glucose closed, and OF glucose open) indicate that the bacterial species in question is:

Glucose oxidizer

The presence of Gram-negative intracellular diplococci in a genital specimen from a male is diagnostic of which disease?

Gonorrhea

Two sputum specimens were submitted to the Microbiology laboratory for culture. A Gram stained smear was evaluated for each specimen prior to culturing. The fields that are shown in these images are representative of the 20 - 30 low power fields (lpf) that were examined. Which one of the two results represents a sputum specimen that is acceptable for culturing?

Gram Stain A

A thick peptidoglycan cell wall is MOST often associated with which of the following?

Gram-positive bacteria

Which one of the following organisms is sensitive to bacitracin:

Group A Streptococcus

Which fungal culture media is used for the primary recovery of pathogenic fungi exclusive of dermatophytes?

Inhibitory mold agar

Amoebae stained with this substance may be readily distinguished because it enhances nuclear and structural detail

Iodine

A 65 y/o male with type 2 diabetes presented to ED complaining of febrile episodes following his last dialysis treatment. The microscopic examination of his urine showed numerous white blood cells and bacteria. His urine was sent to the laboratory for culture and sensitivity. Urine colony count was >100,000 CFU/mL for a single organism that was identified as Klebsiella pneumoniae. Observe the reactions of this organism on the Kirby Bauer antibiotic susceptibility plate and review the susceptibility results on the AST report form. The Hodge Test was positive. Which resistance mechanism is this organism demonstrating?

KPC - Klebsiella pneumoniae Carbapenemase

From the choices listed below, which organism is classified as an aerotolerant anaerobe?

Lactobacillus species

Buffered charcoal yeast extract agar (BCYE) is the nonselective solid culture medium used for the primary recovery of:

Legionella pneumophila

The Gram stain of a sputum specimen is unremarkable but the culture reveals many small gram-negative rods that are able to grow only on charcoal yeast extract agar. What is the MOST likely diagnosis?

Legionnaire's disease

Illustrated in this high-power image is an inflammatory reaction of a skin lesion at the site of a Phlebotomus sand-fly bite. Observed are large histiocytes with small intra-cytoplasmic oval cells measuring 2 µm in diameter that superficially have the appearance of Histoplasma capsulatum yeast cells. Note the distinctive bar-like kinetoplasts that lie adjacent to the nucleus of some of these cells (arrows). Select the name of the protozoa.

Leishmania species

The minimum time of retention for microbiology instrument records is?

Life of the instrument

Which of the following scenarios represents appropriate detection of MRSA by the Kirby Bauer method?

MHA; direct colony suspension; 35oC; cefoxitin disk; 18 hour incubation

In the life cycle for the intestinal trematodes Fasciolopsis/Fasciola and Heterophyes, which stage infects snails?

Miracidium

A patient shows signs of conjunctivitis including itching of the eyes, reddening of the conjunctiva, purulent secretion, and lid edema. A culture was taken of the secretion and a Gram-negative coccobacilli was seen on both the Sheep's blood and chocolate agars. There was no growth observed on the MacConkey agar. Additionally, the colonies were oxidase-positive, catalase-positive, reduced nitrate to nitrite, and liquefied gelatin. The identification of this organism is:

Moraxella lacunata

Which organism will infect humans and a wide range of host animals?

Mycobacterium bovis

An acid-fast bacillus recovered from a post-surgery wound of a young child had the following characteristics: Rapid growth (3-5 days) on blood and chocolate agar Nitrate positive Niacin negative Urease positive Catalase 68ºC positive Iron uptake positive Which of the following Mycobacterium species does this represent?

Mycobacterium fortuitum

The following is the MOST likely identity of an acid-fast bacilli that showed buff-colored, dry, heaped colonies; niacin, nitrate, and urease positive; and took 23 days at 35ºC to grow:

Mycobacterium tuberculosis

The nitrate reduction test is used to determine the ability of an organism to reduce nitrate. The Enterobacteriaceae group can reduce nitrate. Based on this test, what is the end product for which nitrate is reduced?

N2

A patient came into the emergency department with symptoms of meningitis. The patient was suspected of having a blocked cerebral shunt, which can cause meningitis. The shunt was drained and sent to the microbiology laboratory for culture. All of the following organisms are associated with shunt infections EXCEPT?

Neisseria meningitidis

An 18-year-old student was seen in the college health center with a sudden onset of headache, fever, and stiff neck. A gram stain of the cerebral spinal fluid sediment is shown in the photograph to the right. The MOST likely cause of this patient's acute meningitis is:

Neisseria meningitidis

What is the main problem with the acridine orange stain?

Once a bacterium is detected, a Gram stain must be used to determine differential staining characteristics.

All of the following statements about peptide nucleic acid-fluorescence in situ hybridization (PNA-FISH) are true for Staphylococcus EXCEPT?

PNA-FISH assays provide differentiation between Methicillin Resistant Staphylococcus aureus (MRSA) and Methicillin Sensitive Staphylococcus aureus (MSSA)

The FilmArray meningitis/encephalitis panel is a multiplex panel that detects all of the following microorganism types, EXCEPT?

Parasites

Which of the following would ensure positive patient identification prior to specimen collection?

Patient's full name and hospital or medical record number

Refer to the image on the right demonstrating macroscopic images of hyaline molds. All of the following are accurate descriptions of the expected microscopic findings, EXCEPT:

Photo A: single-celled, smooth-walled microconidia

A 40-year-old business man developed intermittent spiking fevers one week following a trip to Western Africa. This image is a Wright-stained smear of his peripheral blood. Based on the morphology of the erythrocytes and the heavy parasitic invasion with ring form trophozoites, the diagnosis of malaria may be made. Which Plasmodium species is represented by this peripheral blood smear?

Plasmodium falciparum

Illustrated in the image to the right is a tube of tryptophane agar with a positive indole reaction, as seen by the red ring at the top of the medium. It is necessary to use xylene extraction and Ehrlich's reagent rather than the conventional Kovac's reagent when detecting indole production by which of the following organisms?

Porphyromonas asaccharolytica

A doctor is requesting an acid-fast culture on a stool specimen. How should the tech handle this request?

Prepare a direct smear from the sample and only digest the specimen for culture if the smear is positive

The trichrome stain is most commonly used to identify which class of parasites?

Protozoa

HIV is known as a retrovirus because:

RNA is used as the template for DNA synthesis

The saying, "If it wasn't recorded, it never happened," holds true in the microbiology laboratory because accrediting agencies require that detailed and accurate records be maintained. All of the following are purposes of record retention within the microbiology laboratory EXCEPT?

Records are not important as computers store all the data

The disappearance of HBsAg and HBeAg, the persistence of Total anti-HBc, the appearance of anti-HBs, and often the presence of anti-HBe indicates what type of Hepatitis infection?

Recovery phase of HBV infection

This Gram-positive coccus is catalase positive. The tests shown are a tube coagulase test inoculated with the isolate, and an MRSA screen plate containing 4% NaCl and 6 µg/mL of oxacillin. A 0.5 McFarland standardized inoculum of the isolate is inoculated to the plate. What step should you take next?

Report the isolate as methicillin-resistant Staphylococcus aureus.

An alpha-hemolytic slightly concave isolate from a respiratory specimen gave a zone of inhibition of 18 mm around the optochin disk. What should the next step be?

Report this organism as Streptococcus pneumoniae.

Common colds are most often associated with which agent?

Rhinovirus

Which of the yeasts listed below is commonly used in baking?

Saccharomyces cerevisiae

All of the following are usually associated with Group A Beta Strep, EXCEPT?

Scalded Skin Syndrome

The upper image is a 4 day old colony grown on Sabouraud's Dextrose agar, recovered from a bacterial culture that was considered to be a "contaminant". The lower image is a high power image of a methylene-blue stained mount prepared from the surfaces of the colony. With these observations, select the fungus genus from the multiple choices as listed.

Sepedonium

A patient is showing signs of an intravenous catheter-associated infection. The physician has removed the catheter and sent the catheter tip along with a skin swab of the catheter site to the laboratory for testing. The physician ordered a Gram stain of the skin entry site and a culture of the catheter tip. On which of the following media should the catheter tip be plated?

Sheep Blood Agar and Thioglycollate Broth

Shigella serotyping is performed by using a polyvalent somatic (O) antisera. A Shigella species grew from culture and serotyped as Group B. Which of the following Shigella species serotypes as Group B?

Shigella flexneri

The ovoid microconidia arranged in a daisy-head pattern at the tip of a straight conidiophore, observed in the photomicrograph on the right, is characteristic of which of the following dimorphic molds?

Sporothrix schenckii

An infective agent of skin wound infections and an agent of toxic shock syndrome, the large, entire, golden-yellow, smooth convex colonies on blood agar were recovered from a swab specimen after 48 hours incubation at 37° C. In the photomicrograph, clusters of Gram-positive cocci were observed microscopically in a Gram stain prepared from one of the colonies. The coagulase reactions are pictured in the lower images. With these observations, select the name of this isolate.

Staphylococcus aureus

Observed on the surface of blood agar are smooth, white, 48-hour-old colonies incubated at 37oC, demonstrating a positive catalase reaction and a negative coagulase reaction. The sample was taken from an intravenous catheter. In the photomicrograph are gram-positive cocci distinctly arranged in loose clusters and in tetrad formation. From these observations, select the presumptive identification of this isolate.

Staphylococcus epidermidis

A tech is testing a sorbitol negative isolate for possible E.coli O157: H7 from the MacConkey with sorbitol agar plate. The biochemical identification proves the organism is E.coli. Serological testing for the O157 somatic antigen is positive. Serological testing for the H7 flagellar antigen is negative. Quality control for all serological testing passed. What should the tech do next?

Subculture the organism to motility medium for repeat H7 serological testing

The morphologic structures for this scolex from a cestode include: A) rostellum, B) hooklets, and C) suckers. Identify the cestode species associated with this scolex.

Taenia solium

The ovum illustrated in this photograph is in an immature stage of development and is surrounded by a residual yolk sack material and membrane. It measures 50 µm in diameter. What is the presumptive identification of this ovum?

Taenia species

Which statement about assays for the antigenic detection of both Clostridioides difficile toxins A and B is TRUE?

The antigenic assays give rapid results

Baseline testing for latent Mycobacterium tuberculosis infection (LTBI) is recommended for all newly-hired healthcare workers. In which of these cases would a tuberculin skin test (TST) be repeated a second time, one to three weeks after the first test?

The first test is negative and the new employee has never been tested for LTBI before.

A tech is working on a culture and accidentally enters an incorrect organism. The tech quickly issues a corrected report which includes both the incorrect result and the new, correct result. The tech completes the report and moves on to the next patient culture. What part of the corrected report process is missing or incorrect?

The physician was not called to be notified of the corrected report

A purulent fluid was collected between the lung and the chest wall. What is the name of this fluid?

Thoracentesis fluid

What is the purpose of a trichrome stain?

To identify protozoan trophozoites and cysts in fecal samples

Which specimen type is inoculated to media by using a quantitative isolation method?

Urine specimen

A CSF specimen was sent to the laboratory for analysis. A glucose, protein, and cell count were performed. Based on the following results, what would be the probable cause? Glucose50 mg/dL Protein100 mg/dL Leukocytes80 cells/mm3 mononuclear

Viral infection

A tech is working on a culture from an aspirated lesion. The culture grows non-hemolytic colonies with flattened edges and raised centers, resembling a fried egg on blood agar. Gram stain of the colonies shows plump Gram-negative bacilli with bipolar staining. What is the likely identification of the organism?

Yersinia pestis

India Ink is used to:

visualize capsule