A wound infection culture grew Gram-positive cocci in clusters. The bacteria were catalase-positive and coagulase-negative. What is the likely microorganism?

Correct Answer: A

Rationale: The correct answer is A: Staphylococcus epidermidis. The presence of Gram-positive cocci in clusters, along with being catalase-positive and coagulase-negative, is indicative of Staphylococcus species. Staphylococcus epidermidis is commonly found on the skin, making it likely to cause wound infections. Summary: B: Staphylococcus aureus is catalase-positive and coagulase-positive. C: Streptococcus pyogenes is catalase-negative. D: Enterococcus faecalis is catalase-negative.

Correct Answer: C

Rationale: The correct answer is C: Vibrio. Cholera is caused by Vibrio cholerae bacteria. These bacteria produce a toxin that causes severe diarrhea and dehydration. Escherichia (choice A) and Salmonella (choice B) are known for causing other types of gastrointestinal infections but not cholera. Acinetobacter (choice D) typically causes respiratory infections, not gastrointestinal illnesses like cholera. Therefore, the correct choice is Vibrio as it is specifically associated with cholera.

Correct Answer: B

Rationale: The correct answer is B: pasteurization. This process involves heating food to a specific temperature to kill harmful bacteria while preserving the flavor and quality of the food. Sanitation (A) refers to maintaining cleanliness to prevent contamination. Disinfection (C) involves killing most, but not all, microbes on surfaces. Purification (D) typically refers to the process of removing impurities, not specifically targeting microbes. In this case, pasteurization best describes the process of reducing harmful microbes in food without completely eliminating all microorganisms.

Correct Answer: A

Rationale: The correct answer is A: Rifampicin. Rifampicin is known to cause red discoloration of bodily fluids, including tears and urine, due to its side effect of harmless color changes. Benzylpenicillins (B and C) and Biseptol-480 do not typically cause such discoloration. Rifampicin's mechanism of action involves binding to bacterial RNA polymerase, leading to inhibition of RNA synthesis, which is unrelated to the mechanism of the other drugs. Thus, based on the unique side effect profile of Rifampicin and its mechanism of action, it is the most likely drug causing red tears and urine in this scenario.

Correct Answer: A

Rationale: The correct answer is A: Blood agar. Streptococcus pneumoniae is a fastidious bacterium that requires enriched media for growth. Blood agar provides the necessary nutrients and growth factors for the cultivation of S. pneumoniae, such as blood proteins and hemin. MacConkey agar (B) is selective for gram-negative bacteria and would not support the growth of S. pneumoniae. Peptone water (C) is a liquid medium that lacks the necessary nutrients for the growth of S. pneumoniae. Choice D is incorrect as blood agar is a suitable medium for cultivating S. pneumoniae.

Correct Answer: B

Rationale: The correct answer is B: Protein synthesis. Bacterial ribosomes are responsible for translating the genetic information from mRNA into proteins. This process involves the binding of transfer RNA molecules carrying amino acids to the ribosome and the formation of peptide bonds between the amino acids to create proteins. DNA replication (A) is carried out by DNA polymerase enzymes, not ribosomes. Energy production (C) is primarily the function of mitochondria in eukaryotic cells, and cell division (D) is regulated by a complex network of proteins and signaling pathways, not ribosomes.

Correct Answer: C

Rationale: The correct answer is C because cultural characteristics of bacteria refer to their growth patterns on different culture media, including liquid and solid agars. Bacteria exhibit unique growth patterns that can be observed and studied on these media. Choice A is incorrect as it refers to isolation techniques, not cultural characteristics. Choice B is incorrect as it describes metabolic activities, not cultural characteristics. Choice D is incorrect as it dismisses the essential aspect of bacterial growth on culture media.

Correct Answer: D

Rationale: The correct answer is D because all the options listed can cause respiratory tract infections. 1. Francisella tularensis can cause pneumonia. 2. Bordetella pertussis causes whooping cough, a respiratory infection. 3. Coxiella brunetti can lead to Q fever, which affects the respiratory system. Therefore, all choices are correct for causing respiratory tract infections. Choices A, B, and C are incorrect because they are individual causes of respiratory infections, whereas choice D encompasses all possible causes listed.

Correct Answer: C

Rationale: The correct answer is C: Beta lactamase. This enzyme is produced by bacteria to break down the beta-lactam ring structure of penicillins, rendering them ineffective. Beta lactam ring (A) is part of the penicillin molecule, not an enzyme. MRSA (B) stands for methicillin-resistant Staphylococcus aureus, a type of bacteria resistant to certain antibiotics, not an enzyme. Aminoglycoside ring (D) refers to a different class of antibiotics and is not related to penicillin resistance in bacteria.