Nokea
A patient who suffered form syphilis took a course of antibiotic therapy and fully recovered. Some time later he was infected again with Treponema pallidum. What form of infection is it?
- A. Reinfection
- B. Recurrence
- C. Superinfection
- D. Secondary infection
Correct Answer: A
Rationale: The correct answer is A: Reinfection. This is because the patient fully recovered from the initial syphilis infection after antibiotic therapy, indicating the elimination of the pathogen. Subsequently getting infected again with Treponema pallidum suggests a new exposure to the same pathogen, resulting in a new infection. Recurrence (B) would imply the reactivation of the same infection, which is not the case here. Superinfection (C) refers to a new infection that occurs on top of an existing infection, which is not the scenario described. Secondary infection (D) typically refers to an infection that occurs after an initial infection weakens the immune system, which is not the case in this scenario.
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Basing upon the data of laboratory assessment of sanitary state of soil in a certain territory, the soil was found to be low-contaminated according to the sanitary indicative value; contaminated according to the coli titer; low-contaminated according to the anaerobe titer (Cl. perfringens). This is indicative of:
- A. Fresh fecal contamination
- B. Old fecal contamination
- C. Insufficient intensity of soil humification
- D. Constant entry of organic protein contaminations
Correct Answer: A
Rationale: Step 1: The soil is low-contaminated according to the sanitary indicative value, which indicates that the contamination is recent.
Step 2: The soil is contaminated according to coli titer, suggesting the presence of coliform bacteria typically found in fresh fecal matter.
Step 3: The soil is low-contaminated according to the anaerobe titer (Cl. perfringens), which is an indicator of recent fecal contamination.
Step 4: Based on the above steps, the correct answer is A: Fresh fecal contamination, as the presence of coliform bacteria and recent anaerobe titer levels point to recent fecal contamination.
Summary:
B: Old fecal contamination - Incorrect because the indicators suggest recent contamination.
C: Insufficient intensity of soil humification - Incorrect as it is not related to the specific indicators mentioned in the question.
D: Constant entry of organic protein contaminations - Incorrect as the indicators point towards fecal contamination, not protein
The specific prevention (by vaccination) of the disease gas gangrene (caused by Clostridium perfringens) is based on:
- A. Killed whole cell vaccine
- B. Anatoxin
- C. There is no specific prevention by vaccination
- D. Alive attenuated vaccine
Correct Answer: B
Rationale: The correct answer is B: Anatoxin. An anatoxin is a toxin that has been rendered harmless while retaining its ability to stimulate an immune response. Gas gangrene is caused by the toxins produced by Clostridium perfringens, not the bacteria itself. Therefore, vaccination with an anatoxin can trigger the immune system to produce antibodies against the toxin, providing immunity against the disease.
A: Killed whole cell vaccine - Gas gangrene is caused by toxins, not the whole bacterium. This type of vaccine may not be effective in preventing the disease.
C: There is no specific prevention by vaccination - This is incorrect, as vaccination with an anatoxin can prevent gas gangrene.
D: Alive attenuated vaccine - Attenuated vaccines contain live, weakened forms of the pathogen. However, for gas gangrene prevention, targeting the specific toxin with an anatoxin vaccine is more appropriate.
A wound infection culture grew Gram-positive cocci in clusters. The bacteria were catalase-positive and coagulase-negative. What is the likely microorganism?
- A. Staphylococcus epidermidis
- B. Staphylococcus aureus
- C. Streptococcus pyogenes
- D. Enterococcus faecalis
Correct Answer: A
Rationale: The correct answer is A: Staphylococcus epidermidis. The presence of Gram-positive cocci in clusters, along with being catalase-positive and coagulase-negative, is indicative of Staphylococcus species. Staphylococcus epidermidis is commonly found on the skin, making it likely to cause wound infections.
Summary:
B: Staphylococcus aureus is catalase-positive and coagulase-positive.
C: Streptococcus pyogenes is catalase-negative.
D: Enterococcus faecalis is catalase-negative.
Family Retroviridae
- A. are helical enveloped viruses
- B. Their capsid consists of two copies o ssRNA (-)
- C. are helical, non-enveloped viruses
- D. are with complex type of symmetry
Correct Answer: B
Rationale: The correct answer is B because retroviruses, including those in the Family Retroviridae, have a capsid consisting of two copies of single-stranded RNA (ssRNA). This is a defining characteristic of retroviruses, which use reverse transcriptase to convert their ssRNA into DNA. This DNA is then integrated into the host cell's genome. Choices A, C, and D are incorrect because Family Retroviridae viruses are not helical non-enveloped viruses (C), they are not helical enveloped viruses (A), and they do not have a complex type of symmetry (D).
Which of the following is a preferred mode of transmission of HIV from a mother to a child
- A. during delivery through mixing of blood
- B. during pregnancy through placenta
- C. via breastmilk during lactation
- D. All of the above
Correct Answer: D
Rationale: The correct answer is D because HIV can be transmitted from a mother to a child through multiple modes: during delivery through mixing of blood, during pregnancy through the placenta, and via breastmilk during lactation. Each mode presents a risk of transmission due to the presence of the virus in bodily fluids. Therefore, all of the above options are preferred modes of transmission for HIV from a mother to a child. Choices A, B, and C alone do not fully encompass all the possible routes of transmission, making them incorrect.