MOD Section A&B Revision Questions for Exam PDF

MOD: SECTION A&B revision questions for exam: Quiz revision: section A MQC Which of the following is the description of endogenous infections: a. they are not caused by microorganisms already in/on the body b. they are caused by normal microflora c. they are transmitted from fomites to hos...

MOD: SECTION A&B revision questions for exam: Quiz revision: section A MQC Which of the following is the description of endogenous infections: a. they are not caused by microorganisms already in/on the body b. they are caused by normal microflora c. they are transmitted from fomites to host d. they are often caused by true pathogens e. they do not originate from the host Why?: Endogenous infection is caused by microorganisms which are part of the host’s normal microflora, which became opportunistic pathogens under certain conditions. Flag question: Question 2 Question 21 pts 1. Pathogenic bacteria attach to the host cells to: a. Avoid antibodies b. Destroy the cells c. Evade complement d. Evade phagocytosis e. Obtain nutrients. Why?: Attachment facilities access nutrients and help bacteria colonize the host by resisting being flushed out of the body. Flag question: Question 3  Question 31 pts 2. Listeria monocytogens, a bacterial pathogen evades phagocytosis by: a. Escaping phagosome and survive in phagocytic cell b. Having a capsule c. Inhibiting complement activation and opsonization. d. Inhibiting phagosome-lysosome fusion e. Surviving at low pH after phagosome-lysosome fusion Why?: Listeria monocytogenes escapes from phagosome into cytoplasm, where it can replicate and evade the host’s immune defenses. Flag question: Question 4 Question 41 pts 3. Which of the following is used to visualize a phage particle? a. Light microscope b. Inverted microscope c. Confocal microscope d. Fluorescence microscope e. Transmission electron microscope Why?: Transmisson electron microscopes provide the resolution needed to visualize the small size of phage particles. Flag question: Question 5 Question 51 pts 4. Which of the following is a differential agent in TCBS medium? a. Yeast fermentation b. Sodium citrate fermentation c. Sucrose fermentation  d. Peptone fermentation e. Thiosulfate fermentation Why?: (TCBS) medium differentiates vibrio species based on their ability to ferment sucrose. Flag question: Question 6 Question 61 pts 5. The analysis technique that involves taking a patient sample (liquid), inoculating it into sterile aerobic and anaerobic bottles in a liquid growth medium, then monitoring the turbidity of the inoculated medium, is known as: a. wound sampling b. blood culture sampling c. urine sampling d. CSF sampling e. LJ slope sampling Why?: Blood culture sampling is used to detect microorganisms in the bloodstream. Flag question: Question 7 Question 71 pts 6. Which one of the following would NOT be considered a Healthcare- associated Infection (HCAI)? a. Food poisoning that requires a hospital admission b. An infected catheter in a critically ill ICU patient c. An infected knee joint following total knee replacement d. An infected hip joint following a hip replacement e. Chloridoids difficile infection in a patient 7 days into a hospital admission Why?: HCALs are infections acquired during hospital stays or healthcare interventions, not pre- existing conditions like food poisoning contracted outside the hospital. 8.Biochemical Analytical Profile Index (API) of a microorganism isolated from a patient is shown in the table below. Calculate the corresponding code for a microorganism that matches this pattern Table API 20E strip inoculated with the unknown culture after incubation: ON A L O CI H U T IN V G G M IN S R S M A A PG D D D T 2 R D D P EL L A O O H A EL M R H C C S E A U N R A C Y A + - + + - - - - + + + + + + - - - - - + 1 2 4 1 2 4 1 2 4 1 2 4 1 2 4 1 2 4 1 2 API 20E Code Calculation For the API 20E strip: Each test is scored as 1, 2, or 4, depending on whether the test in a group is positive or negative. To calculate the code: Combine the scores for the first three tests in a group. Repeat this for all seven groups of tests. Breakdown of test results: 1. Group 1 (ONPG, ADH, LDC): +, -, +→ 1+0+4 =5 2. Group 2 (ODC, CIT, H2S): +, -, -→ 1+0+0 =1 3. Group 3 (URE, TDA, IND): -, -, + → 0+0+4 =4 4. Group 4 (VP, GEL, GLU): +, +, +→ 1+2+4 =7 5. Group 5 (MAN, INO, SOR): +, +, - → 1+2+0 =3 6. Group 6 (RHA, SAC, MEL): -, -, -→ 0+0+0 =0 7. Group 7 (AMY, ARA): -, +→ 0+2=2 Final Code: 5-1-4-7-3-0-2  Question 91 pts 9. Which of the following causes deep seated infections in humans? a. Puccinia recondite b. Diplocarpon rosae c. Filobasidiella neoformans d. Erysiphe alphitoides e. Rhytissma acerina Why?: Answer: Filobasidiella neoformans This is the teleomorph (sexual form) of Cryptococcus neoformans, a fungal pathogen that causes deep-seated infections like cryptococcal meningitis. Flag question: Question 10 Question 101 pts 10. Which of the following are described as dermatophyte fungi a. Aspergillus niger b. Trichophyton interdigitale c. Fusarium d. Sclerotinia sclerotiorum e. Candida Why?: Answer: Trichophyton interdigitale Dermatophytes are fungi that infect keratinized tissues (skin, hair, nails). Trichophyton interdigitale is a well-known dermatophyte. Flag question: Question 11 Question 111 pts 11. A person suffering from aflatoxicosis is associated with the consumption of which of the following commodities?  a. Lettuce b. Wheat c. Grapefruit d. Radish e. Water Why?: Answer: Wheat Aflatoxins are produced by Aspergillus species and are often associated with improperly stored grains like wheat, corn, and peanuts. Flag question: Question 12 Question 121 pts 12. What does the term 'estrogenic' mean? a. It causes cancer in humans b. It causes injury to the liver c. It damages the immune system d. It damages or causes alterations in the reproductive tract e. It interferes with the development of a fetus, causing congenital disabilities Why?: Answer: It damages or causes alterations in the reproductive tract Estrogenic compounds mimic or disrupt estrogen activity, leading to changes in the reproductive system. Flag question: Question 13 Question 131 pts 13. According to the Agency for Research on Cancer (IARC) a. Aflatoxin B1 is carcinogenic. b. All mycotoxins are carcinogenic c. Any mycotoxin can produce cancer  d. Denoxinivalenol is possible carcinogenic e. Mycotoxins only cause tumors development in immunocomprimised patient Why?: Answer: Aflatoxin B1 is carcinogenic. Aflatoxin B1 is classified as a Group 1 carcinogen by the IARC, indicating it is known to cause cancer in humans. Flag question: Question 14 Question 141 pts 14. Fumonisins can be produced by genus belong a. Fusarium and Aspergillus b. Fusarium and Penicillium c. Aspergillus and Escherichia d. Fusarium and Staphylococcus e. Escherichia and Staphylococcus Why?: Answer: Fusarium and Aspergillus Fumonisins are primarily produced by Fusarium species, though some Aspergillus species may also produce them. 15. Which fungal genus is represented in the picture below: a. Fusarium b. Penicillium c. Aspergillus d. Alternaria e. Escherichia Why?:  Fusarium: Banana-shaped or canoe-shaped conidia. Penicillium: Brush-like conidia. Aspergillus: Conidiophores with a bulbous head. Alternaria: Muri form spores with transverse and longitudinal septa. Escherichia: Not a fungus (bacterium). Flag question: Question 16 Question 161 pts 16. Ochratoxin A can be produced by genus belong a. Aspergillus and Penicillium b. Penicillium and Candida c. Aspergillus and Candida d. Aspergillus and Fusarium e. Fusarium and Candida Why?: Answer: Aspergillus and Penicillium Ochratoxin A is a mycotoxin primarily produced by the species Aspergillus and Penicillium. Flag question: Question 17 Question 171 pts 17. Which of the following is correct regarding HIV-1? a. HIV-1 possesses a segmented DNA genome b. Reverse transcription of the HIV-1 genome occurs in the nucleus c. The HIV-1 spike protein is known as Neuraminidase d. HIV-1 reverse transcriptase is carried in the virion e. HIV-1 viruses attach to red blood cells Why?: Answer: HIV-1 reverse transcriptase is carried in the virion HIV-1 carries reverse transcriptase within its virion to convert its RNA genome into DNA after infection. Flag question: Question 18 Question 181 pts 18. Under the Baltimore classification system: a. Group 3 and group 5 viruses have double-stranded DNA genomes b. Influenza A viruses are group 2 viruses c. Retroviruses are group 6 viruses d. Viruses are classified based on the size of the viral genome e. Viruses are classified on the basis of the tissues affected Why?: Answer: Retroviruses are group 6 viruses Retroviruses (e.g., HIV) belong to Group 6, characterized by their single-stranded RNA genome that is reverse-transcribed into DNA. Flag question: Question 19 Question 191 pts 19. What are the common methods of detection of Schistosomiasis? a. Observation of the parasite in the blood b. Detection of anti-parasite antibodies by ELISA c. Observation of eggs in the stool d. Examination of the skin for spots and rashes e. All of the questions are correct Why?: Answer: Observation of eggs in the stool Schistosomiasis is commonly diagnosed by identifying eggs of the parasite in stool or urine samples. However, ELISA can detect antibodies, and other methods can help, depending on the case. Flag question: Question 20 Question 201 pts 20. In malaria, what stages of the parasite life cycle would need to be targeted in order to prevent clinical disease? a. Gametocytes because they are the ones infecting the mosquito b. The blood stages or the sporozoites c. The merozoite stage because this is the one that invades erythrocytes d. The schizont stage because this is the one that generates the merozoites e. This can only be done by spraying insecticides to eliminate the mosquito vector Why?: Answer: The blood stages or the sporozoites Targeting sporozoites (to prevent infection) or blood stages (to prevent symptoms) is crucial. Blood stages are responsible for the clinical manifestations of malaria. Flag question: Question 21 Question 211 pts 21. What is BLAST (Basic local alignment search tool) a. It is software for sequencing microbial DNA b. It is free software for cleaning DNA electropherogram c. It is an algorithm and program for comparing primary biological sequence information such as the nucleotides of DNA sequence d. It is a database for consulting papers e. It is an algorithm for estimating the length of microbial genomes Why?: Answer: It is an algorithm and program for comparing primary biological sequence information such as the nucleotides of DNA sequence BLAST is a widely used bioinformatics tool for sequence comparison. It identifies similarities in nucleotide or protein sequences. Section B: SAQ Question one: Discuss the challenges associated with the culture and identification of pathogenic bacteria from an infection site, including in your discussion named examples of microorganisms, the benefits of undertaking culture and identification, and how the challenges can be overcome. Answer: Culturing and identifying pathogenic bacteria from infection sites is vital for diagnosing infections, but it poses several challenges. Polymicrobial infections, such as those involving Pseudomonas aeruginosa and Staphylococcus aureus, make isolating individual pathogens difficult. Fastidious bacteria like Legionella pneumophila require specific media, while anaerobic bacteria such as Clostridium difficile need oxygen-free environments. Low pathogen loads, as seen in early bacteremia, and the presence of commensals, such as Staphylococcus epidermidis, further complicate isolation. Slow- growing bacteria like Mycobacterium tuberculosis and biofilm-forming pathogens such as Pseudomonas aeruginosa add additional challenges. Despite these hurdles, culture offers critical benefits. It enables definitive pathogen identification, supports antibiotic susceptibility testing (e.g., for Escherichia coli), and provides data for tracking outbreaks, such as with Neisseria meningitidis. To overcome challenges, molecular methods like PCR and MALDI-TOF can complement culture, providing rapid and accurate results. Selective and enriched media, improved sample collection, and automated systems like BACTEC enhance success rates. Disrupting biofilms mechanically or enzymatically also aids isolation. Combining traditional and modern techniques ensures effective pathogen detection and targeted treatment, improving patient outcomes. Exam revising notes: Challenges in Culturing Pathogenic Bacteria 1. Polymicrobial infections: Multiple bacteria (e.g., Pseudomonas aeruginosa, Staphylococcus aureus) in one sample. Fix: Use selective media (e.g., MacConkey agar). 2. Fastidious bacteria: Need special nutrients (e.g., Legionella needs BCYE, Haemophilus needs chocolate agar). Fix: Use enriched media. 3. Anaerobes: Cannot grow in oxygen (e.g., Clostridium difficile). Fix: Use anaerobic chambers. 4. Low pathogen numbers: Few bacteria in blood/CSF. Fix: Concentrate samples or use blood culture bottles. 5. Contaminants/commensals: Hard to tell real pathogens from normal flora (e.g., S. epidermidis vs. S. aureus). Fix: Proper sampling techniques. 6. Slow growers: Some bacteria (e.g., Mycobacterium tuberculosis) grow very slowly. Fix: Use PCR or molecular tools. 7. Biofilms: Bacteria in biofilms (e.g., Pseudomonas) are hard to culture. Fix: Disrupt biofilms first. Why Culture? Identifies bacteria (e.g., Salmonella). Tests antibiotics (e.g., for E. coli). Tracks outbreaks (e.g., Neisseria meningitidis). Overcoming Challenges Use PCR for quick results. Automate processes (e.g., BACTEC for blood cultures). Combine traditional culture with modern techniques. Overcoming Challenges Use PCR for quick results.