Which bacteria are responsible for causing the disease known as 'whooping cough'?

Correct Answer: A

Rationale: The correct answer is A: Bordetella pertussis. Bordetella pertussis is the bacterium responsible for causing whooping cough, also known as pertussis. It produces toxins that damage the respiratory tract, leading to severe coughing fits. Haemophilus influenzae, Streptococcus pneumoniae, and Mycobacterium tuberculosis are not associated with whooping cough. Haemophilus influenzae can cause respiratory infections but not whooping cough. Streptococcus pneumoniae is known for causing pneumonia, and Mycobacterium tuberculosis causes tuberculosis, both different from whooping cough. Therefore, the correct answer is A as it is the specific bacterium linked to the disease in question.

Correct Answer: A

Rationale: The correct answer is A: Neisser staining. This method is specifically used to identify cytoplasmic inclusions by staining them with a specific dye that highlights these structures. Neisser staining is designed to selectively target and visualize cytoplasmic inclusions, making it the most appropriate choice for this purpose. Option B: Clett staining, Option C: Ziehl-Nielsen staining, and Option D: Gram staining are not typically used for identifying cytoplasmic inclusions. Clett staining is not a commonly known staining method for this purpose. Ziehl-Nielsen staining is primarily used to detect acid-fast bacteria like Mycobacterium tuberculosis. Gram staining is used to differentiate bacteria into Gram-positive and Gram-negative based on cell wall characteristics. Therefore, these options are not suitable for identifying cytoplasmic inclusions.

Correct Answer: B

Rationale: The correct answer is B: Motility. Bacterial flagella function in providing motility to bacteria, allowing them to move towards nutrients or away from harmful substances. Flagella are long, whip-like appendages that rotate to propel the bacteria through their environment. Incorrect choices: A: Protein synthesis - Bacterial flagella are not involved in protein synthesis. C: Adhesion to surfaces - While some bacteria use flagella for attachment, their main function is not adhesion. D: DNA replication - Flagella do not play a role in DNA replication, which occurs in the bacterial cell's nucleus.

Correct Answer: A

Rationale: The presence of acid-fast bacilli stained red against a blue background indicates mycobacteria, specifically Mycobacterium tuberculosis in this case. Ziehl-Neelsen staining is commonly used to detect tuberculosis. Diphtheria is caused by Corynebacterium diphtheriae, which does not stain with Ziehl-Neelsen. Pneumonia is a general term for lung infections caused by various pathogens. Leprosy is caused by Mycobacterium leprae, which requires special staining methods different from Ziehl-Neelsen.

Correct Answer: B

Rationale: The correct answer is B: Outer membrane with lipopolysaccharides. Gram-negative bacteria have an outer membrane that contains lipopolysaccharides, which play a role in pathogenicity and resistance to certain antibiotics. This outer membrane is a distinguishing feature of Gram-negative bacteria, as opposed to Gram-positive bacteria that have a thick peptidoglycan layer. Choices A, C, and D are incorrect because Gram-negative bacteria have a thin peptidoglycan layer, do have a cell wall (although it is different from Gram-positive bacteria), and do not contain teichoic acids.

Correct Answer: A

Rationale: The correct answer is A: HSV-1. Herpes simplex infections on lips and in the mouth are most commonly caused by HSV-1 due to its preference for infecting oral mucosa. HSV-2 typically causes genital herpes. HSV-6 and HSV-7 are less common and not typically associated with oral infections. Therefore, based on the typical presentation and epidemiology of herpes simplex infections, HSV-1 is the most likely cause in this scenario.

Correct Answer: C

Rationale: The correct answer is C: Acid-fast cell wall. Mycobacterium tuberculosis is characterized by its unique cell wall composition, containing high levels of mycolic acids which make it acid-fast. This property allows it to resist decolorization during acid-fast staining procedures. This distinguishes it from other bacteria. A: Producing spores is not a key feature of Mycobacterium tuberculosis. Spore formation is more commonly associated with bacterial species such as Bacillus and Clostridium. B: Mycobacterium tuberculosis is not Gram-negative. It is classified as acid-fast Gram-positive. D: Mycobacterium tuberculosis does not produce toxins as a key feature. Its pathogenicity is more closely related to its ability to evade host immune responses and persist in host tissues.

Correct Answer: C

Rationale: The normal microflora plays a crucial role in defending against pathogens in the skin and mucus. This is because the skin and mucus act as physical barriers and the normal microflora outcompetes potential pathogens, preventing their colonization. In contrast, the circulatory system (A), hepatobiliary tract (B), and CNS (D) are not typically colonized by normal microflora, so they do not directly contribute to defense against pathogens in those areas.

Correct Answer: A

Rationale: The correct answer is A: Giardia lamblia. This protozoan matches the description of the causative agent because it has two nuclei, four flagella, and a ventral adhesive disc. Giardia lamblia is commonly found in the duodenum and causes giardiasis. The other choices can be eliminated because Leishmania donovani causes visceral leishmaniasis, not the described symptoms. Entamoeba coli is a non-pathogenic amoeba found in the large intestine. Trypanosoma gambiense causes African trypanosomiasis and is transmitted by the tsetse fly, not matching the described characteristics.