NCLEX : Identifying Bacteria

Study concepts, example questions & explanations for NCLEX

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Example Questions

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Example Question #1 : Identifying Bacteria

What is the primary effect of botulism toxin?

Possible Answers:

Ascending paralysis

Tonic paralysis

Flaccid paralysis

Nausea and vomiting

Correct answer:

Flaccid paralysis

Explanation:

Botulism toxin inhibits acetylcholine release from the presynaptic nerve terminal, causing flaccid paralysis. Death in botulism exposure is generally due to respiratry failure. Tonic paralysis is the cause of respiratory arrest in other toxicity exposures, such as exposure to tetanus toxin. 

Example Question #2 : Microbiology

What organism causes Rocky Mountain spotted fever?

Possible Answers:

Rickettsia rickettsii

Borrelia burgdorferi

Rickettsia helvetica

Ehrlichia chaffeensis

Correct answer:

Rickettsia rickettsii

Explanation:

Rickettsia rickettsii causes Rocky Mountain Spotted Fever, and is spread by dermacentor ticks. It causes fever, headache, muscle pain, and a rash. Borrelia burgdorferi is associated with Lyme disease, ehrlichia chaffeensis is associated with human monocytotropic ehrlichiosis, and rickettsia helvetica is associated (very rarely) with meningitis. 

Example Question #2 : Identifying Bacteria

What is the most common cause of infectious diarrhea in HIV-positive patients?

Possible Answers:

Salmonella

Cryptosporidium

Clostridium

Campylobacter

Correct answer:

Cryptosporidium

Explanation:

While all of the listed organisms can cause diarrhea, Cryptosporidium, a protozoa, is the most commonly isolated organism in HIV positive patients presenting with diarrhea. 

Example Question #4 : Microbiology

What is the most common infection preceding the development of Guillain-Barré syndrome?

Possible Answers:

Campylobacter jejuni

Salmonella

Staphylococcus aureus

E. coli

Correct answer:

Campylobacter jejuni

Explanation:

30% of cases of Guillain-Barré are preceded by infection by Campylobacter jejuni. There is no known association between Staphylococcus aureus, Salmonella, or E.coli and Guillain-Barré syndrome.

Example Question #4 : Microbiology

All of the following are frequently implicated in epiglottitis except __________.

Possible Answers:

H. influenzae type B

Campylobacter jejuni

Streptococcus spp

Staphylococcus aureus 

Correct answer:

Campylobacter jejuni

Explanation:

The most commonly implicated bacteria in epiglottiits are H. influenzae type B, Streptococcus spp, and Staphylococcus aureus. Campylobacter jejuni is a common cause of food poisoning.

Example Question #3 : Identifying Bacteria

Which agar would be the best choice option to identify Escherichia coli

Possible Answers:

Phenethyl alcohol

Nutrient agar

EMB (eosin methylene blue), because it is selective and differential

Selenium enriched media

Correct answer:

EMB (eosin methylene blue), because it is selective and differential

Explanation:

The question requires the knowledge that  Escherichia coli is a facultative, Gram negative, lactose fermenting bacteria. EMB (eosin methylene blue), or Mac (MacConkey) media is superior for isolating Escherichia coli  because it is both selective and differential. Nutrient agar is neither selective nor differential. Selenium enriched media would not help identify this bacteria because Escherichia coli does not require this supplemented media to grow. Phenethyl alcohol can be used to select for anaerobic bacteria, which is of no utility in this situation.

Example Question #4 : Identifying Bacteria

Which of the following sexually transmitted infections is mismatched with its causative agent?

Possible Answers:

Gonorrhea - Neisseria gonorrhea

Toxic shock syndrome - Staphylococcus aureus

Genital warts - herpes simplex virus 2

Syphillis - Treponema pallidum

Correct answer:

Genital warts - herpes simplex virus 2

Explanation:

Genital warts is caused by human papillomavirus. All other sexually transmitted infection is correctly matched with its causative agent.

Example Question #5 : Identifying Bacteria

Which of the following organisms causes fever, headache, fatigue, myalgia, and buboes?

Possible Answers:

Borrelia burgdorferi

Bacillus anthracis

Staphylococcus aureus

Yersinia pestis

Correct answer:

Yersinia pestis

Explanation:

The question stem describes bubonic plague which is caused by Yersinia pestisStaphylococcus aureus causes skin infections, toxic shock, and food poisoning. Bacillus anthracis causes anthrax, which is similar to plague, but does not cause buboes. Borrelia burgdorferi causes lyme disease., which presents as rash and arthralgia. 

Example Question #6 : Identifying Bacteria

E. coli (Esherichia coli) are primarily found in the colon of humans, but can also cause cystitis. Which of the following best explains why this occurs?

Possible Answers:

E. coli are obligate anaerobes

E. coli are microaerophiles

E. coli are obligate aerobes

E coli are facultative anaerobes

Correct answer:

E coli are facultative anaerobes

Explanation:

The colon is anaerobic and the bladder is aerobic. This fact explains why  E. coli normally lives in an anaerobic environment, but can also survive aerobically. Facultative anaerobes normally live in anaerobic conditions but can adapt to aerobic conditions. Microaerophiles describes bacteria that are obligate aerobes, but are poisoned by high levels of oxygen and thus require specific oxygen levels to grow.

Example Question #7 : Identifying Bacteria

90% of all Proteus infections in human are caused by what organism?

Possible Answers:

Proteus penneri

Proteus myxofaciens

Proteus vulgaris

Proteus mirabilis

Correct answer:

Proteus mirabilis

Explanation:

While Proteus penneri and Proteus vulgaris do cause opportunistic infections in a small percentage of people, 90% of Proteus infections in humans are caused by Proteus mirabilis. 

Proteus myxofaciens is only found in insect hosts and does not infect humans.

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