In order to prevent wound infection associated with surgical procedures a patient was given a synthetic antiprotozoan drug with a high activity against Helicobacter pylori. Specify this drug:

Correct Answer: A

Rationale: The correct answer is A: Metronidazole. Metronidazole is a synthetic antiprotozoan drug with high activity against Helicobacter pylori, a bacterium that can cause wound infections. Metronidazole specifically targets anaerobic bacteria like H. pylori, making it effective in preventing wound infections. Incorrect choices: B: Doxycycline hydrochloride - Doxycycline is primarily used for bacterial infections, not protozoan infections like H. pylori. C: Chingamin - Chingamin is not a commonly used drug for treating H. pylori infections or preventing wound infections. D: Acyclovir - Acyclovir is an antiviral drug used to treat herpes infections, not bacterial or protozoan infections like H. pylori.

Correct Answer: B

Rationale: The correct answer is B: Orthomyxovirus type 1. Family Reoviridae includes Orthoreovirus types 1, 2, and 3. Orthomyxovirus belongs to a different family, Orthomyxoviridae. Therefore, B is the correct answer. Orthoreovirus types 1, 2, and 3 are part of the Reoviridae family. Choice A, C, and D are incorrect because they are all part of the Reoviridae family which includes Orthoreoviruses.

Correct Answer: A

Rationale: The correct answer is A because protozoan emerging and reemerging diseases fall under Group I according to the classification of infectious diseases by the Centers for Disease Control and Prevention (CDC). Group I includes diseases caused by newly identified or known infectious agents that have increased in incidence or geographic range. Choice B (Group II) includes diseases that have re-emerged due to antimicrobial resistance or lack of previous vaccination. Choice C (Group III) encompasses diseases that can be transmitted from animals to humans, and choice D (Group IV) includes diseases that are caused by re-introduction of eradicated pathogens.

Correct Answer: A

Rationale: The correct answer is A: Bacillus anthracis. This bacterium is known to cause anthrax, a serious infectious disease in humans and animals. Bacillus anthracis is a gram-positive, spore-forming bacterium that produces toxins leading to the characteristic symptoms of anthrax. Clostridium tetani causes tetanus, Mycobacterium tuberculosis causes tuberculosis, and Streptococcus pneumoniae causes pneumonia, none of which are related to anthrax. Therefore, based on the specific pathogen responsible for anthrax, Bacillus anthracis is the correct answer.

Correct Answer: A

Rationale: The correct answer is A: Streptococcus pyogenes. 1. Gram-positive cocci in chains suggest streptococci. 2. Catalase-negative indicates it's not staphylococci. 3. Beta-hemolytic points towards Group A Streptococcus (S. pyogenes). Summary: B. Streptococcus pneumoniae is not beta-hemolytic. C. Enterococcus faecalis is not typically chains. D. Staphylococcus aureus is catalase-positive.

Correct Answer: D

Rationale: The correct answer is D because the catarrhal stage of whooping cough is characterized by mild respiratory symptoms such as mild coughing, sneezing, or a runny nose. During this stage, the cough may start to worsen but is not yet severe. A: Incorrect - Decrease in paroxysms of coughing is not seen in the catarrhal stage; it occurs later in the paroxysmal stage. B: Incorrect - Subsequent respiratory infection for many months after the onset of pertussis is not a characteristic of the catarrhal stage. C: Incorrect - Uncontrollable coughing followed by a high pitched 'whoop' sound is typical of the paroxysmal stage, not the catarrhal stage.

Correct Answer: A

Rationale: The correct answer is A: Erythrocytic schizogony. In this case, the patient most likely has malaria, specifically caused by Plasmodium falciparum. The fever attacks every 2 days (tertian fever) are characteristic of P. falciparum infection. The cycle of erythrocytic schizogony in P. falciparum is around 48 hours, leading to the recurring fever pattern. Choices B, C, and D are incorrect as tissue schizogony does not cause the characteristic fever pattern, exotoxins are not typically involved in malaria fever, and gametocytes do not directly cause fever attacks.

Correct Answer: A

Rationale: The correct answer is A: Isoniazid. When rifampicin is used alone, there is a risk of developing resistance. Isoniazid is commonly used in combination with rifampicin to prevent resistance by targeting different mechanisms in the bacteria. Isoniazid works by inhibiting mycolic acid synthesis, while rifampicin targets RNA polymerase. This combination therapy is known as the first-line treatment for tuberculosis. Choices B, C, and D are incorrect because they do not have the same mechanism of action as isoniazid and would not be effective in preventing rifampicin resistance.

Correct Answer: A

Rationale: The correct answer is A: Viruses. Viruses are acellular, meaning they lack cellular structure, protein synthesizing ability, enzymes, and energy systems. They are essentially genetic material (DNA or RNA) enclosed in a protein coat. Fungi (B), bacteria (C), and protozoa (D) are all cellular organisms with protein synthesizing, enzyme, and energy systems. Viruses rely on host cells to replicate and carry out metabolic functions, making them distinct from other groups.