BCSE > Microbiology > Flashcards

Microbiology Flashcards

Identify microbial pathogens and interpret diagnostic tests to inform antimicrobial selection and infection control. (54 cards)

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1
Q

Necropsy of an emaciated white-tailed deer reveals superficial lymphadenitis with cutaneous draining abscesses, and multiple firm, tan pleural nodules.

Which reportable disease must be considered?

A

Bovine tuberculosis

(Mycobacterium bovis)

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2
Q

Pasteurization requires heating milk to 161°F (71.7°C) to kill which ubiquitous zoonotic organism, which also causes neurologic disease in cattle and sheep?

A

Listeria monocytogenes

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3
Q

Which class of bacteria is grouped by Lancefield serologic classification?

A

Streptococci

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4
Q

True or False:

Bacteria and yeast are primary factors in otitis externa.

A

False

They tend to be opportunists when a primary non-infectious disorder exists (e.g., atopy, flea allergy, conformational abnormalities of the external ear).

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5
Q

Which infectious organism (genus and species) is most commonly reported in association with closure of large animal hospitals in North America?

A

Salmonella enterica

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6
Q

Mycobacteria all have which specific microscopic staining characteristic in common?

A

They are acid-fast

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7
Q

What is the organism most commonly isolated from cat bite abscesses?

A

Pasteurella multocida

(abscesses usually due to bites from other cats)

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8
Q

Which of the following does polymerase chain reaction (PCR) detect?

  • A. Antibody
  • B. Protein
  • C. Nucleic acid
  • D. Antigen
A

C. Nucleic acid

The chain reaction (“CR” in PCR) refers to exponential expansion of nucleic acid chains.

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9
Q

The minimum inhibitory concentration (MIC) breakpoint for ampicillin is ≤8 µg/mL. Your patient’s infection has a bacterial isolate that has MIC value of 2 µg/mL.

Is the isolate sensitive or resistant to ampicillin?

A

Sensitive

Bacterial growth was inhibited at an in vitro concentration of only 2 µg/mL, indicating that the microbe should perish when standard drug dosages are used (assuming normal distribution to affected tissue).

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10
Q

Are leptospirae gram-positive or gram-negative bacteria?

A

Gram-negative

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11
Q

Which poorly staining coiled spiral organisms require darkfield or phase contrast microscopy for visualization?

A
  • Leptospira spp.
  • Borrelia spp.
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12
Q

Rhodococcus equi, an obligate intracellular bacterium, infects which immune cell?

A

Macrophage

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13
Q

What is the causative agent of infectious canine hepatitis?

A

Canine adenovirus 1

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14
Q

Which gram-negative bacteria is the causative agent of plague?

A

Yersinia pestis

Spread by bites from infected fleas or from consuming infected prey animals.

Most often affects cats in the Western U.S. Zoonotic.

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15
Q

Name two causative agents of systemic fungal diseases most commonly seen in the Missouri, Mississippi, and Ohio River valleys of the U.S.

A
  • Histoplasma capsulatum
  • Blastomyces dermatitidis
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16
Q

What is the most likely origin of bacterial contaminants in surgical wounds?

  • A. Endogenous flora
  • B. Air
  • C. Surgical team
A

A. Endogenous flora

This explains why Staphylococcus spp. and Escherichia coli, plus other commensal or opportunistic bacteria, are among the bacteria most often isolated from infected surgical sites.

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17
Q

What is the common name for mandibular osteomyelitis of ruminants caused by Actinomyces?

A

Lumpy jaw

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18
Q

Which pathogenic fungus appears as basophilic, broad-based budding yeast forms in infected tissues, typically near water sources?

A

Blastomyces dermatitidis

(on cytology or histopathology)

This tissue form is safe to examine microscopically, unlike the highly infectious mold form that poses a zoonotic risk if cultured.

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19
Q

This zoonotic, gram-positive rod can cause cutaneous lesions and fatal systemic illness, and necropsy of affected animals is discouraged to avoid release of infective spores.

A

Bacillus anthracis

(anthrax)

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20
Q

What is the causative agent of cat scratch disease in humans?

A

Bartonella spp.

(particularly B. henselae and B. clarridgeiae)

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21
Q

Chronic wasting disease affects deer and elk, and it is believed to be caused by which type of infectious agent?

A

Prion

Prions also cause bovine spongiform encephalopathy (mad cow disease), scrapie in sheep, and Creutzfeldt–Jakob disease in humans.

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22
Q

Name two factors that can influence the efficacy of a disinfectant.

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A
  • Organic debris
  • Concentration
  • Temperature
  • Contact time
  • Spectrum of activity
  • Relative efficacy in the presence of organic debris
  • Toxicity to animals and humans
  • Potential damaging effects on certain surfaces
  • Cost
  • Potential environmental effects

Organic debris can inactivate disinfectants, which is why cleaning with a detergent before disinfection is essential.

23
Q

Isolation guidelines for human medicine target the prevention of five different types of transmission of infectious diseases. Name two.

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A
  • Contact
  • Droplet
  • Airborne
  • Common vehicle
  • Vector-borne
24
Q

Define:

Disease outbreak

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A

Increased occurrence of infections above the expected baseline (endemic) level

25
Molecular diagnostics (tests that evaluate for the presence of DNA or RNA) are increasingly used in veterinary medicine for the detection of infectious agents. **Name two advantages of the use of these tests.**
* Better sensitivity and specificity than most immunoassays * Automated platforms that increase throughput * Quantitative assessment of viral load (clinically useful) * Fast turnaround time that can speed up detection and reduce overall cost * Simultaneous analysis of multiple samples
26
Considering the names of these disorders, what is **unusual** about **mycosis fungoides** and **botryomycosis**?
Neither disease is caused by a fungus | (despite the "myco" part of each name, which means "relating to fungi") ## Footnote Botryomycosis is an exuberant staphylococcal infection of the skin (mainly of horses), whereas mycosis fungoides is a form of cutaneous lymphoma.
27
Dogs (and humans) mainly **acquire blastomycosis** via which route?
Inhalation of conidia from the environment
28
Which statement about methicillin-resistant staphylococci (**MRS**) in dogs and cats is correct? * A. MRSA infections in pets usually originate from the pet itself * B. MRSP is more common in pets than MRSA * C. MRSP commonly spreads from pets to healthy humans * D. MRSA infections in pets are always multidrug resistant ## Footnote Methicillin-resistant *Staph. aureus* = MRSA Methicillin-resistant *Staph. pseudintermedius* = MRSP
B. MRSP is more common in pets than MRSA ## Footnote MRSP is the main source of MRS infections in dogs and cats, whereas MRSA is rare and usually transmitted from humans.
29
Why is **coagulase positivity** clinically important in methicillin-resistant staphylococci? ## Footnote Methicillin-resistant *Staph. aureus* = MRSA Methicillin-resistance *Staph. pseudintermedius* = MRSP
Indicates higher virulence and helps distinguish MRSA and MRSP from other, less pathogenic staphylococci ## Footnote *S. epidermidis* (a common contaminant) is less pathogenic and is coagulase-negative.
30
Which **gram-negative** organism is the most common cause of infection in **large animal neonates**?
*Escherichia coli* | (often from environmental contamination or maternal sources) ## Footnote It is the most common cause of septicemia, diarrhea, and failure of passive transfer–related infections in neonatal large animals.
31
Name **two bacterial** pathogens associated with the **bovine respiratory disease complex** (BRD).
* *Mannheimia haemolytica* * *Pasteurella multocida* * *Histophilus somni* * *Mycoplasma bovis* ## Footnote Viral pathogens also contribute: bovine herpesvirus 1, parainfluenza-3, bovine viral diarrhea virus, and bovine respiratory syncytial virus.
32
During which **season** is **blastomycosis** most commonly diagnosed in North America?
Autumn ## Footnote Likely because people and animals are typically exposed to *Blastomyces* spores in summer, and the disease’s incubation period causes symptoms to appear several weeks later.
33
Which common **fungal** organism has a distinguishing **polysaccharide capsule**?
*Cryptococcus* spp. ## Footnote It is a distinguishing microscopic feature and confers virulence.
34
# Choose the correct answer: **Paired serology** (two samples, two to four weeks apart) typically documents rising plasma levels of \_\_\_\_ as a confirmatory test for many infectious diseases. Choices: * A. IgA * B. IgM * C. IgG
C. IgG ## Footnote IgG is usually measured in paired titers. IgM is typically detected in a single sample to indicate recent exposure, and IgA is less commonly used for systemic infections (it is on mucosal surfaces and in secretions).
35
Streptococci are divided into three types based on hemolysis patterns when grown on blood agar plates (alpha-, beta-, and gamma-hemolytic). **Which type are most of the pathogenic streptococci?**
Beta-hemolytic ## Footnote Major exception is *Strep.* pneumoniae, which is alpha-hemolytic.
36
What is the basis for **resistance** to **beta-lactam antibiotics** such as ampicillin or penicillin in some strains of *Staphylococcus*?
Plasmid-encoded beta-lactamase ## Footnote This enzyme hydrolyzes the beta-lactam ring of these antibiotics, rendering them ineffective.
37
**Brucellosis** is a disease of worldwide importance and affects a number of animal species. What is the most common **clinical manifestation** in **females**?
Abortion | (primarily late-term)
38
What is the most common clinical manifestation of **brucellosis** in **males**?
* Orchitis * Infection of accessory sex glands
39
What is the **reservoir** for ***Brachyspira hyodysenteriae***?
The gastrointestinal tract of pigs ## Footnote This is the causative agent of swine dysentery.
40
Which domestic animal species are most **susceptible** to infection with ***Bacillus anthracis***?
Ruminants: * cattle * sheep * goats
41
What is the etiological agent for **bacillary hemoglobinuria** (red-water, icterohemoglobinuria) in cattle?
*Clostridium hemolyticum* | (a.k.a. *C. novyi* type D) ## Footnote *C. hemolyticum* infection causes massive intravascular hemolysis. Confusingly, the name "red water disease" is also used to describe bovine babesiosis.
42
Which of the following is **true** about **Q fever**? * A. Caused by *Coxiella burnetii* * B. Is not zoonotic * C. Primarily transmitted by insect bites * D. Always causes visible illness in infected animals
A. Caused by *Coxiella burnetii* ## Footnote *C. burnetii* causes abortion (primarily in dairy cattle); is zoonotic; is spread by aborted tissues, urine, feces; and many infections are silent.
43
Which types of **toxin** produced by ***Clostridium botulinum*** most often cause disease in domestic animals?
Types C and D cause disease in birds and mammals ## Footnote Types A, B, E, and F cause human disease.
44
**Diskospondylitis** is most often seen in dogs (especially larger breeds). What is the most common **bacterium** isolated?
*Staphylococcus* spp. ## Footnote Others are *Brucella canis*, *Streptococcus* spp., etc.
45
# True or False: Valley fever is contagious.
False | (it is not contagious) ## Footnote Caused by *Coccidioides immitis*, infection primarily occurs via inhalation of fungal spores from dust.
46
What is the geographical **endemic** region of **coccidioidomycosis** in North America?
* Southwestern U.S. * Mexico * Arid/semi-arid regions
47
***Clostridium difficile*** diarrhea is often associated with what **inciting** risk factor/predisposing cause?
Antibiotic therapy disrupts normal gut flora | (allowing *C. difficile* overgrowth and toxin production) ## Footnote Other predisposing factors can include hospitalization, immunosuppression, or other gastrointestinal disease.
48
Which of the following species is most **resistant** to **tetanus**? * A. Cat * B. Chicken * C. Cow * D. Dog * E. Horse
B. Chicken ## Footnote Horses are most sensitive, then cows, then dogs, then cats.
49
How should all **bite wounds** be classified? * A. Contaminated * B. Clean-contaminated * C. Clean
A. Contaminated ## Footnote The oral cavity harbors a large and diverse microbial population, including bacteria that are normally harmless in the mouth but pathogenic when introduced into tissues.
50
An adult cat presents with anorexia and bilateral mucopurulent nasal discharge. The owner keeps a flock of messenger pigeons. **What is the top differential diagnosis for this cat?**
Cryptococcosis | (*Cryptococcus neoformans* infection) ## Footnote Commonly found in pigeon droppings and can cause nasal and systemic disease in cats.
51
Which of these is characterized by a fulminant, **rapid** course that includes **neurologic** signs in a majority of cases, and **can affect humans**? * A. Cytauxzoonosis * B. Rocky Mountain spotted fever * C. Canine monocytic ehrlichiosis
B. Rocky Mountain spotted fever
52
Which **form** of ***Coccidioides immitis*** is typically observed in **cytology** or **histopathology** of infected tissues?
Spherules containing endospores ## Footnote These are the tissue form of *C. immitis* and are safe to observe microscopically, unlike the infectious arthroconidia that pose a zoonotic risk if cultured.
53
When are **morulae** in neutrophils most likely to be seen on a blood smear from a horse with **equine granulocytic anaplasmosis**, and when might they be missed?
* Seen: three to five days after fever onset, during the acute phase * Missed: too early, late in disease, after antibiotic treatment, or with low parasitemia ## Footnote Timing and treatment affect visibility of morulae; a negative smear does not rule out infection. Definitive diagnosis relies on PCR or IFAT (depending on stage of disease).
54
Which of the following statements is **true** regarding the **diagnosis** of **babesiosis** in animals? * A. Diagnosis is best made using blood from large peripheral veins * B. Blood smear examination is most sensitive in capillary blood * C. Babesia organisms are only visible in white blood cells * D. Serology and PCR are never useful for diagnosis
B. Blood smear examination is most sensitive in capillary blood ## Footnote Capillary blood, such as from ear tips or tail veins, often has higher parasitemia, making intraerythrocytic piroplasms easier to detect.
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