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A blood culture from a patient with sepsis revealed Gram-positive cocci in pairs. The bacteria were catalase-negative and alpha-hemolytic. What is the most likely causative agent?
- A. Streptococcus pneumoniae
- B. Staphylococcus aureus
- C. Enterococcus faecalis
- D. Neisseria gonorrhoeae
Correct Answer: A
Rationale: The correct answer is A: Streptococcus pneumoniae. This is because the bacterium is Gram-positive cocci in pairs, catalase-negative, and alpha-hemolytic, which are characteristic features of S. pneumoniae. The other choices can be ruled out based on specific characteristics: B) Staphylococcus aureus is catalase-positive, C) Enterococcus faecalis is gamma-hemolytic, and D) Neisseria gonorrhoeae is a Gram-negative diplococcus. Therefore, based on the given information, S. pneumoniae is the most likely causative agent of the sepsis.
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Which scientist performed the first successful vaccination against smallpox?
- A. Pasteur
- B. Jenner
- C. Semmelweis
- D. Koch
Correct Answer: B
Rationale: The correct answer is B: Jenner. Edward Jenner is credited with performing the first successful vaccination against smallpox in 1796. He used cowpox virus to inoculate individuals, leading to immunity against smallpox. Jenner's experiment laid the foundation for modern vaccination. Pasteur (A) is known for developing the germ theory of disease. Semmelweis (C) advocated for handwashing to prevent infections. Koch (D) identified the causative agents of several diseases but did not develop the smallpox vaccine.
For family Rhabdoviridae is true that:
- A. They are enveloped viruses
- B. They cause plague
- C. They have spherical shape
- D. They infect only humans
Correct Answer: A
Rationale: The correct answer is A: They are enveloped viruses. Rhabdoviridae family consists of enveloped viruses, which means they have a lipid envelope surrounding their protein coat. This envelope helps the virus in infecting host cells and evading the immune system. The other choices are incorrect because B: They cause plague is not true as Rhabdoviridae family typically causes diseases like rabies in mammals. C: They have spherical shape is incorrect as rhabdoviruses have a bullet-shaped structure. D: They infect only humans is also incorrect as Rhabdoviridae viruses can infect a wide range of hosts beyond just humans.
A patient with a long history of chronic gastritis undergoes a gastroscopy, which detects an ulcer in the duodenum area. Microscopic examination of the tissue biopsy developed Gram-negative curved bacteria and the rapid urease activity test of the biopsy material was highly positive. The most likely cause of the disease is:
- A. Vibrio cholerae
- B. Campylobacter fetus
- C. Acinetobacter baumannii
- D. Helicobacter pylori
Correct Answer: D
Rationale: The correct answer is D: Helicobacter pylori. Helicobacter pylori is a known bacterium associated with causing duodenal ulcers. The presence of Gram-negative curved bacteria in the biopsy along with a highly positive rapid urease test is characteristic of H. pylori infection. Vibrio cholerae causes cholera, not duodenal ulcers. Campylobacter fetus is associated with gastroenteritis, not duodenal ulcers. Acinetobacter baumannii is a nosocomial pathogen, not typically associated with duodenal ulcers. In summary, the unique combination of findings in this case points towards H. pylori as the most likely cause of the disease.
After consumption some tinned meat a patient had diplopia, acute headache, deglutition disorder, hard breathing, muscle weakness. The diagnosis was botulism. What factor of pathogenicity are the clinic presentations of this disease connected with?
- A. Exotoxin B.Hemolysin C.Endotoxin D.Plasmocoagulase E.Fibrinolysin
Correct Answer: A
Rationale: The correct answer is A, Exotoxin. Botulism is caused by the exotoxin produced by Clostridium botulinum bacteria. The symptoms described - diplopia, acute headache, deglutition disorder, hard breathing, muscle weakness - are all consistent with botulism due to the neurotoxic effects of the exotoxin. The exotoxin interferes with neurotransmission at the neuromuscular junction, leading to muscle paralysis and the symptoms mentioned. The other choices (B, C, D, E) are incorrect as they do not correspond to the pathogenic mechanism of botulism and do not explain the specific clinical manifestations observed in this case.
There are several cases of children from boarding school suffering from sore throat. Microscopy of tonsil smears stained according Neisser method has revealed thin yellow bacilli with dark brown grains on their ends placed in the shape of Roman numeral five. What infection can be suspected in this case?
- A. Diphtheria
- B. Scarlet fever
- C. Listeriosis
- D. Tonsilitis
Correct Answer: A
Rationale: Rationale for Correct Answer A (Diphtheria):
1. Thin yellow bacilli with dark brown grains on ends suggest Corynebacterium diphtheriae, characteristic of diphtheria.
2. Roman numeral five shape is typical of diphtheria bacilli.
3. Diphtheria causes sore throat and can spread in boarding schools.
4. Neisser staining method is used for diphtheria bacilli.
Summary of Incorrect Choices:
B: Scarlet fever is caused by Streptococcus pyogenes and presents with rash, not yellow bacilli.
C: Listeriosis is caused by Listeria monocytogenes, not consistent with the described findings.
D: Tonsillitis can be caused by various bacteria or viruses, but the specific characteristics described do not match.