Sanitary bacteriological research on water by the membrane filter method revealed two red colonies on a membrane filter (Endo agar) through which 500 ml of analyzed water were passed. Calculate the coli index and coli titer of the analyzed water:
- A. 4 and 250
- B. 2 and 500
- C. 250 and 4
- D. 500 and 2
Correct Answer: A
Rationale: The correct answer is A: 4 and 250. Coli index is calculated by dividing the number of red colonies by the volume of water analyzed, which gives 2 red colonies / 500 ml = 4. Coli titer is the reciprocal of the coli index, so it is 1 / 4 = 250. This indicates the concentration of coliform bacteria in the water sample. Choices B, C, and D are incorrect as they do not follow the correct calculation steps for determining the coli index and coli titer. B has the correct coli index but incorrect coli titer. C and D have the values reversed, leading to incorrect results.
You may also like to solve these questions
In Transmissive infections, the vector is:
- A. Air
- B. Objects
- C. Medical devices
- D. Water
Correct Answer: A
Rationale: The correct answer is A: Air. In transmissive infections, the vector refers to the means by which the infectious agent is transmitted from one host to another. Air can carry pathogens such as viruses and bacteria, leading to respiratory infections like the flu or tuberculosis. Airborne transmission occurs when droplets containing the pathogens are inhaled. Objects (B), medical devices (C), and water (D) can also transmit infections, but they are not specifically related to transmissive infections. Objects and medical devices can harbor pathogens, while waterborne infections are transmitted through contaminated water sources. However, in the context of transmissive infections, the primary vector is the air due to its ability to carry infectious agents over distances.
Which of the following bacteria is associated with the formation of dental caries?
- A. Streptococcus mutans
- B. Streptococcus pneumoniae
- C. Bacillus cereus
- D. Clostridium tetani
Correct Answer: A
Rationale: Step 1: Streptococcus mutans is known for its ability to produce lactic acid, which contributes to the demineralization of tooth enamel, leading to dental caries.
Step 2: Streptococcus pneumoniae is a common respiratory pathogen and not directly associated with dental caries.
Step 3: Bacillus cereus is a foodborne pathogen and not typically found in the oral cavity or associated with dental caries.
Step 4: Clostridium tetani causes tetanus, a neurological condition, and is not involved in the formation of dental caries.
Summary: Choice A is correct as Streptococcus mutans is specifically linked to dental caries due to its acidogenic and aciduric properties. Choices B, C, and D are incorrect as they are not associated with dental caries.
The main virulence factor of Neisseria meningitidis is?
- A. The polysaccharide capsule
- B. The beta lactamase
- C. The erythrogenic toxin
- D. None of the above
Correct Answer: A
Rationale: The correct answer is A: The polysaccharide capsule. The capsule of Neisseria meningitidis plays a crucial role in its virulence by preventing phagocytosis, allowing the bacteria to evade the host's immune system. This leads to increased survival and colonization in the host.
Choice B: The beta lactamase is incorrect because it is an enzyme that breaks down beta-lactam antibiotics and does not directly contribute to the virulence of Neisseria meningitidis.
Choice C: The erythrogenic toxin is incorrect as this toxin is produced by Streptococcus pyogenes, not Neisseria meningitidis.
Choice D: None of the above is incorrect as the polysaccharide capsule is indeed a key virulence factor of Neisseria meningitidis.
Which of the following bacteria is capable of surviving in extreme heat?
- A. Escherichia coli
- B. Bacillus subtilis
- C. Staphylococcus aureus
- D. Clostridium botulinum
Correct Answer: B
Rationale: The correct answer is B: Bacillus subtilis. Bacillus subtilis is a thermophilic bacterium capable of surviving in extreme heat due to its heat-resistant spores. It forms spores when exposed to unfavorable conditions, allowing it to withstand high temperatures. Escherichia coli (A), Staphylococcus aureus (C), and Clostridium botulinum (D) are mesophilic bacteria that do not have the same heat resistance mechanisms as Bacillus subtilis, making them unable to survive in extreme heat conditions.
A patient has been brought to the hospital with the complaints of headache, pain in left hypochondrium. He has been ill for 1,5 weeks. The sudden illness began with the increase of body temperature up to 39, 90C. In 3 hours the temperature decreased and hydropoiesis began. The attacks repeat rhythmically in 48 hours. The patient had visited one an African country. The doctors have suspected malaria. What method of laboratory diagnostics is necessary to use?
- A. Blood examination
- B. Immunological tests
- C. Stool examination
- D. Urine examination
Correct Answer: A
Rationale: The correct method of laboratory diagnostics for suspected malaria is blood examination. Malaria is diagnosed by detecting the presence of the Plasmodium parasite in the patient's blood. This can be done through microscopy to identify the parasite in a blood smear or through rapid diagnostic tests (RDTs) that detect specific antigens produced by the parasite. Blood examination allows for the direct visualization of the parasite, making it the most accurate method for diagnosing malaria. Immunological tests, stool examination, and urine examination are not suitable for diagnosing malaria as the parasite primarily resides in the red blood cells. Stool and urine examinations are more commonly used for diagnosing gastrointestinal or urinary tract infections, respectively.