NCLEX : Classes of Bacteria

Study concepts, example questions & explanations for NCLEX

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Example Questions

Example Question #3 : Understanding Bacteria

If a colony of round or oval-shaped bacteria are arranged in a random grape-like cluster, they must be:

Possible Answers:

Streptobacilli

Spirochetes

Staphylococci

There is no way to predict based on the information provided.

Streptococci

Correct answer:

Staphylococci

Explanation:

The two most common bacterial arrangements are Staph- and Strep-. Staph- is a non-symmetrical arrangement like a cluster of grapes. Strep- indicates a chain of bacteria.

The three most common bacterial shapes are listed below.

Coccus—round or oval

Bacillus—rectangular or rod-shaped

Spirilla (spirochete)—spiral

By breaking down names into arrangement and shape, students can predict or identify the appearance of an organism by its name. In the example Staph indicates arrangement in a chain. Coccus indicates round or oval in shape. Therefore, Staphylococci are round or oval-shaped organisms arranged in a cluster.

Example Question #13 : Bacteria

Which of the following correctly describes the classification of Bordetella pertussis?

Possible Answers:

Gram positive aerobic cocci

Gram negative anaerobic cocci

Gram negative aerobic rod

Gram positive anaerobic rod

Correct answer:

Gram negative aerobic rod

Explanation:

Bordetella pertussis is a Gram negative, rod-shaped aerobe. It requires oxygen to function and commonly infects the respiratory tract of young children, causing whooping cough. 

Example Question #14 : Microbiology

Which of the following describes the classification of Neisseria gonorrhoeae?

Possible Answers:

Gram positive diplococcus

Gram positive rod

Gram negative diplococcus

Gram negative rod

Correct answer:

Gram negative diplococcus

Explanation:

Neisseria gonorrhoeae is a Gram negative coccus bacterium that generally presents as a diplococcus (in pairs of cocci). 

Example Question #1 : Classes Of Bacteria

Vibrio cholerae is classified as what type of bacteria?

Possible Answers:

Gram negative facultative rods

Gram positive cocci

Gram negative cocci

Gram positive facultative rods

Correct answer:

Gram negative facultative rods

Explanation:

Vibrio cholerae is classified as Gram negative facultative rods. This bacteria is the most well known amongst the Vibrio species as it's the cause of cholera, which produces a toxin that causes very severe diarrhea.

Example Question #2 : Classes Of Bacteria

Any species of bacteria that feeds on dead matter is termed a __________.

Possible Answers:

Archaebacteria

Thermophile

Saprophyte

Halophile

Correct answer:

Saprophyte

Explanation:

Bacteria or any other microbes that feed on dead matter are termed saprophytes. Thermophilic microbes thrive in heated environments, halophiles such as Vibrio parahaemolyticus prefer salt water, and archaebacteria are a group of bacteria found in high heat, high salt content locations such as sewage treatment plants and are able to tolerate many extreme habitats.

Example Question #17 : Microbiology

E. coli is classified as what type of bacteria?

Possible Answers:

Gram negative cocci

Gram negative rod

Gram positive cocci

Gram positive rod

Correct answer:

Gram negative rod

Explanation:

E. coli is a Gram negative rod. It's a lactose fermenting bacteria commonly implicated in urinary tract infections and less frequently in gastroenteritis. 

Example Question #3 : Classes Of Bacteria

Which of the following describes the morphology and features of Staphylococcus species?

Possible Answers:

Gram positive cocci, catalase positive

Gram negative cocci, catalase positive

Gram positive rods, catalase negative

Gram negative rods, catalase negative

Correct answer:

Gram positive cocci, catalase positive

Explanation:

Staphylococcus species are Gram positive, catalase positive cocci. The most famous member of this bacterial species, Staphylococcus aureus, is commonly implicated in skin infections, upper respiratory infections, and gastroenteritis (food poisoning).

Example Question #19 : Microbiology

Which of the following bacteria is classified as Gram positive cocci?

Possible Answers:

Chlamydia trachomatis

Staphyloccocus aureus

Rikettsia prowazekii
Neisseria meningitidis
Correct answer:

Staphyloccocus aureus

Explanation:

Staphyloccocus aureus are Gram positive cocci. Chlamydia trachomatis and Rikettsia prowazekii are both classified as Gram negative rods and Neisseria meningitidis are Gram negative cocci.

Example Question #1 : Classes Of Bacteria

All of the following are Gram positive bacteria except __________.

Possible Answers:

Streptococcus

Staphyloccocus

Clostridium

Salmonella

Correct answer:

Salmonella

Explanation:

All of the bacteria listed are Gram positive except Salmonella, which is a Gram negative facultative rod. 

Example Question #2 : Classes Of Bacteria

A sputum culture from a patient is described as "Gram positive cocci". What is the significance of the Gram stain?

Possible Answers:

The bacteria has a thick peptidoglycan cell wall

The bacteria is actively multiplying

The bacteria has no chitin cell wall

The bacteria has a thick chitin cell wall

The bacteria has no peptidoglycan cell wall

Correct answer:

The bacteria has a thick peptidoglycan cell wall

Explanation:

The Gram stain is a test used to help classify bacteria based on the presence of peptidoglycan in the cell wall. Bacteria with a thick peptidoglycan cell wall will stain dark purple, and are termed Gram positive. On the other hand, if there is no peptidoglycan cell wall (or a very thin one), it will show up as pink. This is termed Gram negative. This distinction is particularly important when prescribing classes of antibiotics, as the cell wall is commonly targeted by antibiotics. 

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