Nokea
Gram-negative rods producing red colonies on Endo agar were isolated from a fecal sample. The bacteria were lactose-fermenting. What microorganism is likely responsible?
- A. Escherichia coli
- B. Salmonella
- C. Shigella
- D. Proteus
Correct Answer: A
Rationale: The correct answer is A: Escherichia coli. E. coli is a Gram-negative rod that ferments lactose, leading to red colonies on Endo agar. This bacterium is commonly found in the human gut and is known for its ability to ferment lactose. Salmonella and Shigella are also Gram-negative rods but do not ferment lactose, so they would not produce red colonies on Endo agar. Proteus is a Gram-negative rod that is not known for its lactose-fermenting ability and would not produce red colonies on Endo agar. Therefore, based on the characteristics provided, E. coli is the most likely microorganism responsible for the red colonies on Endo agar.
You may also like to solve these questions
An etiological cause of hospital-acquired infections could be
- A. an opportunistic microorganism
- B. an obligate pathogen
- C. an obligate pathogenic bacterium or virus
- D. all are correct
Correct Answer: D
Rationale: The correct answer is D because hospital-acquired infections can be caused by a variety of microorganisms, including opportunistic pathogens and obligate pathogens such as bacteria or viruses. Opportunistic microorganisms take advantage of weakened immune systems in hospital patients, while obligate pathogens are capable of causing infections in healthy individuals. Therefore, all the choices are correct in this context as they represent potential etiological causes of hospital-acquired infections.
The eukaryotes known for the presence of a macronucleus and a micronucleus are:
- A. algae
- B. fungi
- C. protozoans
- D. slime molds
Correct Answer: C
Rationale: The correct answer is C: protozoans. Protozoans are eukaryotic organisms that possess both a macronucleus, responsible for general cell functions, and a micronucleus, involved in genetic processes like reproduction. Algae (choice A) typically have a single nucleus, fungi (choice B) lack distinct macronucleus and micronucleus structures, and slime molds (choice D) do not have the same nucleus organization as protozoans. Thus, protozoans are the only group among the choices that exhibit the specific characteristics of having both a macronucleus and a micronucleus.
A bacteriological laboratory has received smears from the sputum of a patient with a chronic pulmonary disease. Microscopical examination of the smears stained by the Ziehl-Neelsen technique revealed red bacilli. What property of the tuberculosis bacillus has shown itself?
- A. Acid resistance
- B. Alkali resistance
- C. Alcohol resistance
- D. Capsule formation
Correct Answer: A
Rationale: The correct answer is A: Acid resistance. The Ziehl-Neelsen staining technique is specifically used to detect acid-fast bacteria like Mycobacterium tuberculosis, which is resistant to acid decolorization. This property allows the tuberculosis bacillus to retain the stain even after exposure to acid-alcohol, appearing red under the microscope.
Explanation of incorrect choices:
B: Alkali resistance - This property is not relevant in the context of Ziehl-Neelsen staining for acid-fast bacteria.
C: Alcohol resistance - While alcohol resistance is related to acid-fastness, it is not the specific property highlighted by Ziehl-Neelsen staining.
D: Capsule formation - Capsule formation is a different characteristic and not directly related to the staining behavior of acid-fast bacteria in the Ziehl-Neelsen technique.
Trichinosis is an infection caused by ingestion of a:
- A. nematode
- B. virus
- C. bacteria
- D. fungus
Correct Answer: A
Rationale: The correct answer is A: nematode. Trichinosis is caused by the roundworm Trichinella spiralis, a type of nematode. Nematodes are multicellular parasites commonly found in raw or undercooked meat. Viruses, bacteria, and fungi do not cause trichinosis. Viruses are not parasitic worms, bacteria are single-celled organisms, and fungi are eukaryotic organisms distinct from nematodes. Therefore, the ingestion of nematodes, not viruses, bacteria, or fungi, leads to trichinosis.
Bacteriological inspection of disinfection quality at a pharmacy revealed a microorganism in an utility room (in the sink). The microorganism has the following properties: mobile nonspore-forming gram- negative bacteria that form capsular substance, grow well on ordinary nutrient media, secrete the blue-green pigment. This microorganism is most likely to be of the following genus:
- A. Pseudomonas
- B. Proteus
- C. Clostridium
- D. Shigella
Correct Answer: A
Rationale: The correct answer is A: Pseudomonas.
Rationale:
1. Mobile nonspore-forming gram-negative bacteria with a capsule substance indicate Pseudomonas.
2. Pseudomonas grow well on ordinary nutrient media, matching the description.
3. The secretion of a blue-green pigment is a characteristic feature of Pseudomonas.
4. Proteus is a gram-negative bacterium but does not match all the given properties.
5. Clostridium is a gram-positive bacterium that forms spores.
6. Shigella is a gram-negative bacterium but does not have the other characteristics mentioned.
Therefore, based on the properties described, the most likely genus of the microorganism is Pseudomonas.