microbiology a systems approach test bank

Correct Answer: A

Rationale: The correct answer is A: Streptococcus pneumoniae. This bacterium is known for producing a capsule that helps it evade the immune system. The capsule acts as a protective barrier, making it difficult for the immune system to recognize and attack the bacteria. Streptococcus pneumoniae is a common cause of pneumonia and meningitis. Explanation for why other choices are incorrect: B: Escherichia coli does not typically produce a capsule for immune evasion. It is more commonly associated with gastrointestinal infections. C: Salmonella enterica also does not produce a capsule for immune evasion. It is known for causing foodborne illness. D: Bacillus subtilis is a soil bacterium that is not known for producing a capsule to avoid the immune system.

Correct Answer: A

Rationale: The correct answer is A: Psittacosis. This disease is transmitted via aerosols containing dried bird droppings or respiratory secretions from infected birds. When these aerosols are inhaled, the bacteria causing psittacosis enter the respiratory system and infect the individual. - B: Shigellosis is transmitted through contaminated food or water, not via aerosols. - C: Leptospirosis is transmitted through contact with water, soil, or food contaminated with the urine of infected animals, not via aerosols. - D: Giardiasis is transmitted through ingesting contaminated food or water, not via aerosols. Therefore, Psittacosis is the only disease in the list that is transmitted via aerosols, making it the correct answer.

Correct Answer: D

Rationale: The correct answer is D: Imipenem. Imipenem is a carbapenem antibiotic effective against multiple-resistant microorganisms due to its broad spectrum and resistance to beta-lactamases. It is often used as a last resort for severe infections. Ampicillin (A) and Penicillin (B) are both beta-lactam antibiotics that are less effective against multiple-resistant microorganisms due to widespread resistance mechanisms. Augmentin (C) is a combination of amoxicillin and clavulanic acid, which may have limited efficacy against certain resistant strains but is not as effective as imipenem for treating infections caused by multiple-resistant microorganisms.

Correct Answer: A

Rationale: The correct answer is A because Legionellae are typically found in natural water sources such as lakes, rivers, and soil. Legionellae thrive in aquatic environments and can also be present in mud. Choice B is incorrect as Legionellae are not limited to infected humans but are also found in the natural environment. Choice C is incorrect as Legionellae are not primarily associated with infected animals. Choice D is incorrect as Legionellae do have natural reservoirs in water and soil.

Correct Answer: A

Rationale: The correct answer is A: Entamoeba histolytica. This protozoan parasite causes amoebic dysentery and is characterized by cysts with four nuclei in fecal smears. It is commonly associated with chronic diarrhea. Balantidium coli (B) presents with large ciliated trophozoites, not cysts. Giardia lamblia (C) has trophozoites with flagella and causes giardiasis, not cysts with four nuclei. Trichomonas hominis (D) typically has a pear-shaped trophozoite and is not associated with cysts with four nuclei.