A wound smear from a patient revealed Gram-positive cocci arranged in clusters. The culture was catalase-positive and coagulase-positive. What is the causative agent?
- A. Staphylococcus aureus
- B. Streptococcus pyogenes
- C. Micrococcus luteus
- D. Enterococcus faecalis
Correct Answer: A
Rationale: The correct answer is A: Staphylococcus aureus.
1. Gram-positive cocci in clusters suggest staphylococci.
2. Catalase-positive indicates staphylococci since streptococci are catalase-negative.
3. Coagulase-positive further confirms Staphylococcus aureus, distinguishing it from other staphylococci.
Summary: B is incorrect as Streptococcus pyogenes is catalase-negative. C is incorrect as Micrococcus luteus is catalase-negative and coagulase-negative. D is incorrect as Enterococcus faecalis is catalase-negative and coagulase-negative.
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A 32-year-old patient undergoing dental examination was found to have some rash-like lesions resembling secondary syphilis in the oral cavity. The patient was referred for the serological study with the purpose of diagnosis confirmation. In order to detect antibodies in the serum, living Treponema were used as diagnosticum. What serological test was performed?
- A. Immobilization
- B. Passive hemagglutination
- C. Precipitation
- D. Complement binding
Correct Answer: B
Rationale: The correct answer is B: Passive hemagglutination. In this test, red blood cells coated with Treponema antigens agglutinate in the presence of patient's serum antibodies. This indicates the presence of antibodies against Treponema, confirming the diagnosis.
A: Immobilization test uses live Treponema to detect specific antibodies, but it is not commonly used for syphilis diagnosis.
C: Precipitation test is not commonly used for syphilis diagnosis.
D: Complement binding test is not specific for syphilis and is used more for autoimmune diseases.
Therefore, passive hemagglutination is the most appropriate serological test in this case due to its specificity and relevance to the presentation of the patient.
On the 15-th day after a minor trauma of the right foot a patient felt malaise, fatigability, irritability, headache, high body temperature, feeling of compression, tension and muscular twitching of his right crus. What disease can it be?
- A. Tetanus
- B. Anaerobic gas gangrene
- C. Erysipelas
- D. Acute thrombophlebitis
Correct Answer: A
Rationale: The correct answer is A: Tetanus. Tetanus is caused by the bacterium Clostridium tetani, which produces a toxin affecting the nervous system. Symptoms such as malaise, irritability, muscular twitching, and high body temperature are characteristic of tetanus due to muscle spasms and rigidity. The 15-day incubation period after trauma aligns with the typical onset of tetanus symptoms.
Incorrect choices:
B: Anaerobic gas gangrene - This condition usually presents with localized tissue necrosis and gas bubbles in the affected area, not systemic symptoms like malaise and headache.
C: Erysipelas - This is a bacterial skin infection presenting with red, swollen patches, not the neurological symptoms seen in tetanus.
D: Acute thrombophlebitis - This is a blood clot in a vein causing pain and swelling, not associated with the systemic symptoms and muscle twitching seen in tetanus.
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.
In a bacteriological laboratory some bacterial smears had to be stained by Gram's method. For this purpose the following reagents were prepared: gentian violet, Lugol's solution, aqueous fuchsin solution. What other reagent is required?
- A. 96% ethanol
- B. 5% sulfuric acid
- C. Methylene blue solution
- D. Carbolic fuchsin
Correct Answer: A
Rationale: The correct answer is A: 96% ethanol. In Gram's staining method, after applying gentian violet, Lugol's solution, and aqueous fuchsin, the next step is to use a decolorizing agent like 96% ethanol to wash away the excess stain from the Gram-negative bacteria. This step is crucial as it helps differentiate between Gram-positive and Gram-negative bacteria based on their cell wall properties. The other choices are incorrect because sulfuric acid is not used in Gram's staining method, methylene blue is typically used in other staining techniques like the simple stain, and carbolic fuchsin is not a standard reagent in the Gram's staining process.
The complex of all biological processes/mechanisms responsible for the state of steady internal, physical and chemical conditions in the living systems and defense against all foreign agents is knows as:
- A. infection
- B. homeostasis
- C. immunity
- D. commensalism
Correct Answer: B
Rationale: The correct answer is B: homeostasis. Homeostasis refers to the process by which living organisms maintain a stable internal environment despite external changes. It involves various biological processes and mechanisms that regulate factors such as temperature, pH, and nutrient levels within narrow limits. This is crucial for the proper functioning of cells, tissues, and organs.
Now, let's analyze the other choices:
A: Infection - Infection refers to the invasion and multiplication of harmful microorganisms in the body, leading to illnesses. It is not the correct answer as it does not encompass the overall maintenance of internal conditions.
C: Immunity - Immunity is the body's ability to resist and fight off infections. While immunity is related to defense against foreign agents, it does not fully capture the concept of maintaining internal stability.
D: Commensalism - Commensalism is a type of symbiotic relationship between different species where one benefits without harming the other. It is not related to the overall regulation of