Several patients with similar complaints came to the doctor. They all present with weakness, pain in the intestines, indigestion. Feces analysis revealed the need for urgent hospitalization of the patient, who had microbial cysts with four nuclei detected in his samples. Such cysts are characteristic of the following protozoon:

Correct Answer: A

Rationale: The correct answer is A: Entamoeba histolytica. This protozoon is known to cause amoebic dysentery, presenting symptoms of weakness, intestinal pain, and indigestion. The presence of microbial cysts with four nuclei in fecal samples is characteristic of Entamoeba histolytica. These cysts are the infective form of the parasite and can cause severe invasive disease in the intestines. Incorrect choices: B: Entamoeba coli does not typically cause invasive disease or severe symptoms like those described in the question. C: Balantidium is a ciliated protozoan that causes balantidiasis, which presents differently from the symptoms described in the question. D: Trichomonad is a flagellated protozoan that typically infects the urogenital tract, not the intestine, and does not form cysts with four nuclei. In summary, the key clues in the question were the symptoms of weakness, intestinal pain,

Correct Answer: B

Rationale: The correct answer is B because the AST reaction, or anti-streptolysin titer, is used in the diagnostic of post-streptococcal sequelae, such as rheumatic fever and glomerulonephritis. This test measures the level of antibodies produced by the body in response to Streptolysin O, a toxin produced by Group A Streptococcus bacteria. It helps in identifying if a patient has had a recent Streptococcus infection that could lead to these complications. A: Incorrect. The AST reaction does not require urine samples, but rather blood samples. C: Incorrect. The AST reaction specifically targets antibodies produced in response to Group A Streptococcus. D: Incorrect. The AST reaction does not directly identify isolated streptococci but rather measures the body's immune response to Streptolysin O.

Correct Answer: A

Rationale: The correct answer is A: Clostridium perfringens. Clostridium perfringens is a Gram-positive, spore-forming bacterium that is anaerobic and produces gas. It is commonly associated with wound infections and gas gangrene. Clostridium tetani causes tetanus, not wound infections. Clostridium botulinum causes botulism, not typically associated with wound infections. Bacillus anthracis causes anthrax, which does not typically produce gas in wound infections.

Correct Answer: A

Rationale: Step 1: Legionellosis is caused by the Legionella bacteria. Step 2: Legionellosis has two main clinical forms - Legionnaires disease and Pontiac fever. Step 3: Legionnaires disease presents with severe pneumonia symptoms, while Pontiac fever is a milder flu-like illness. Step 4: Therefore, the correct answer is A: Legionnaires disease and Pontiac fever. Summary: - Choice B (Skin and intestinal form) is incorrect as Legionellosis primarily affects the lungs. - Choice C (Lymphatic, lung, and intestinal forms) is incorrect as it does not accurately represent the clinical forms of Legionellosis. - Choice D (None of the above) is incorrect as Legionellosis does have specific clinical forms.

Correct Answer: C

Rationale: Step 1: Define sexually transmitted infections (STIs) as infections primarily spread through sexual contact. Step 2: Understand that STIs can also be transmitted through non-sexual means like blood transfusions. Step 3: Recognize that choice C is incorrect as it limits STIs to only sexually transmitted infections. Step 4: Therefore, the correct answer is C as it does not encompass all possible modes of transmission for STIs. Summary: Choices A, B, and D are incorrect as they all accurately describe the characteristics of sexually transmitted infections, while choice C is incorrect as it excludes other potential modes of transmission for STIs.

Correct Answer: C

Rationale: To calculate the total magnification, we multiply the magnification of the ocular lens by the magnification of the objective lens. In this case, 10 (ocular) x 40 (objective) = 400. This is why choice C (400) is correct. Choices A, B, and D are incorrect because they do not represent the correct calculation of total magnification based on the given magnification powers of the ocular and objective lenses.

Correct Answer: A

Rationale: The correct answer is A: Tetanus. Tetanus is caused by the bacterium Clostridium tetani, which produces a neurotoxin leading to muscle stiffness, including trismus (restricted mouth opening). The patient's history of a stab wound increases the likelihood of tetanus infection due to the spores entering the body through the wound. Incorrect Choices: B: Brucellosis does not typically present with trismus and is more commonly associated with fever, joint pain, and fatigue. C: Whooping cough presents with severe coughing fits but does not cause trismus. D: Wound anaerobic infection may cause localized symptoms at the wound site but is less likely to cause trismus compared to tetanus.

Correct Answer: A

Rationale: The correct answer is A. Method of Ziel-Neelsen. This method uses a special stain (carbol fuchsin) to detect acid-fast organisms like Mycobacterium tuberculosis, the causative agent of tuberculosis. The staining procedure involves heating the slide to help penetrate the mycolic acid layer of the bacteria, making them resistant to decolorization by acid-alcohol. The red stained acid-fast bacilli stand out against the blue counterstain. This method is specific for identifying tubercle bacilli in sputum samples. Choice B: Method of Romanowsky-Giemsa is used for staining blood smears and is not suitable for detecting acid-fast bacilli in sputum. Choice C: Method of Gram is used for staining bacteria based on their cell wall composition and is not effective for identifying acid-fast bacilli like Mycobacterium tuberculosis. Choice D: Method of Neisser is not a specific staining method for acid-fast bacilli and is not suitable

Correct Answer: B

Rationale: The correct answer is B: Salmonellosis. The description of microorganisms resembling a tennis racket indicates the presence of Salmonella typhi, which causes salmonellosis. Salmonella bacteria can appear like tennis rackets under a microscope due to their flagella. Botulism (A) is caused by Clostridium botulinum, which does not resemble a tennis racket. Cholera (C) is caused by Vibrio cholerae, which appears as curved rods under the microscope. Dysentery (D) is usually caused by bacteria like Shigella or Entamoeba histolytica, which do not resemble tennis rackets.