Microbiology For Health Professionals Lab Answer Key

Microbiology$for$Health$Professionals$$ 1. Cite some beneficial and harmful aspects of molds (filamentous fungi). 3 points a. Most fungi are decomposers. Many fungi can create food like bread and wine while other fungi have medical uses like creating HBV vaccines and being used as cancer therapy. b. There are many fungal diseases that can affect the hair, skin, and nails. These include cutaneous mycoses, subcutaneous mycoses, and superficial mycoses. Some fungi are also involved in food spoilage. 2. How are fungi classified into their medically important phyla? Cite examples for each phyla. 3 points a. Fungi are classified into their medically important phyla by their sexual spores. The spores include Zygomycota, Ascomycota, Basidiomycota, and anamorphs. Examples for Zygomycota are Rhizopus and mucor. An example of Ascomycota is aspergillus. An example of Basidiomycota is Coprinus (mushroom). Lastly, an example of anamorphs is penicillium. 3. What is the purpose of asexual spores for fungi? What are the two most common asexual spore types and what do they look like? 3 points a. Asexual spores are for when conditions are stable fungi produce asexually because it is simple mitosis and there is no need for new genes. The two most common types of spores are conidiospores and sporangiospores. Conidiospores are formed in chains attached to a conidiophore while sporangiospores are formed in sacs that contain the spores. 4. Why is it advantageous for fungi to reproduce both sexually and asexually? 3 points a. It is advantageous for fungi to reproduce sexually and asexually because it gives itself the ability to reproduce in any environment. When the environment is not suitable for asexual reproduction, it would then resort to sexual reproduction. Sexual reproduction allows for the fungi to have genetic variation from its parent, whereas in asexual reproduction, they are identical to their parent. The variation that sexual reproduction gives, allows for the fungi to gain more advantageous traits to adapt to its environment. Once they have adapted to the point where they can successfully survive, then they would then reproduce asexually with the newly acquired genetical variations from sexual reproduction. 5. Since dimorphism is a property of fungi, how do you account for the fact that molds (filamentous fungi w/ hyphae) grow preferentially in vitro rather than in vivo? 3 points a. Some fungi preferentially grow in vitro rather than vivo because fungi strive in different temperatures. The dimorphism properties of fungi allow it to be in either yeast or hyphal form. Hyphal usually grows in room temperature, while yeast usually grows in body temperature. Mold grows in hyphal conditions and will correspondingly grow in hyphal conditions. 6. Why are yeast cells classified as fungi, and how do they differ from other fungi? 3 points a. Yeast cells are classified as fungi because they are nonfilaments, unicellular fungi. Yeast, like fungi, reproduce by asexual budding, and it can also reproduce sexually by ascospores. Yeast differs from fungi because yeasts are unicellular and do not have hyphae or sporangia. 7. Cite some beneficial and pathogenic aspects of yeast. 3 points a. Yeast such as Saccharomyces is useful because it is used in baking, brewing, and creating juices. However, yeast such as, Candida albicans, are pathogenic as they contribute to urinary tract infections, vaginal infections, and thrush. 8. A female patient develops candidiasis (moniliasis) following prolonged antibiotic therapy for a bladder infection caused by Pseudomonas aeruginosa. How can you account for the development of the concurrent fungal infection? 3 points a. The patient developed this concurrent fungal infection because it was a superinfection. The antibiotics used for the bladder infection caused by pseudomonas aeruginosa killed off the good/normal bacteria that keeps the right amount of yeast. This resulted with the removal of a kind of defense in the immune system. Without this good/normal bacterium, candidiasis was able to grow and infect the female patient. The yeast continuously grows out of control which results in a yeast infection. Case Study: A 33-year-old housewife with no premorbidities presented with sudden onset of breathlessness after a 4-day history of cough and fever. On examination, she was febrile (fever) and tachypnoeic (abnormal rapid breathing), with oxygen saturation of 84% on high-flow oxygen. Respiratory system examination showed bronchial breath sounds in left supraclavicular and interscapular areas; all other systems were within normal limits. Hence a clinical diagnosis of left upper lobe pneumonia with acute respiratory distress syndrome (ARDS) was initially made, based on the presentation. Laboratory investigations showed normal white cell counts (WCC) with mildly elevated erythrocyte sedimentation rate (31 mm/h) and mild elevation of aspartate aminotransferase/alanine transaminase (liver enzymes) at (144/152 U/L) levels. Other routine blood parameters were normal. Initial workup for fever, including malaria, dengue, scrub typhus and leptospirosis tests, were negative, thereby ruling out the other common causes of ARDS prevalent in the locality. Hepatitis B surface antigen and HIV were also negative. Chest X-ray showed left hemithorax haziness. ECG showed sinus tachycardia (rapid heart rate) and twodimensional echocardiography was normal. Ultrasound study of the abdomen was normal. Arterial blood gases showed respiratory alkalosis with PO2/FiO2 of 121. A clinical diagnosis of left upper lobe pneumonia with ARDS was considered, and the patient was started on broad-spectrum antibiotics. She was also started on oseltamivir, after collecting respiratory samples, in view of the possibility of H1N1 influenza, which is commonly seen at that time of the year in the community. As the patient continued to be tachypnoeic and subsequent investigations showed increasing WCC, she was electively intubated and antibiotics were escalated. Meanwhile, blood and urine cultures were reported as sterile (no bacteria), and viral studies were negative for influenza and other common respiratory viruses. Sputum samples for acid-fast bacilli were reported as negative. As the patient was not improving on current therapies, on the fourth day of admission, the patient's sputum was again cultured and this time was positive. It was considered that this could be a “false” positive as possibly only normal upper respiratory flora, therefore, a repeat culture of endotracheal aspirate was cultured. This culture was also positive. CT scan of the thorax was suggestive of an acute infective aetiology in both lungs, predominantly in the left upper lobe. • • • Why did the patient not respond to the previous course of antibiotics? 2 points o The patient did not respond to the previous course of antibiotics because the patient was experiencing acute respiratory distress syndrome due to a fungal infection. The antibiotics used were not effective for the fungi infection because antibiotics are only effective for bacterial infections. Fungi have a different cellular structure compared to bacteria and would correspondingly have different antigens. Culturing of the sputum and endotracheal aspirate revealed what type of organism present? 2 points o The type of organism that is present is a fungus, which is a Ascomycota. Colonies on the agar appeared initially as a white dense mat with the surface later becoming brownish-black as the culture matured, but a visible whiter edge was still apparent. Microscopic examination revealed septate hyphae with chains of spores arising from the terminal bulb of the aerial hyphae. What specific genus do you suspect is the causative agent of the patient’s ARDS? 2 points o The specific genus that we suspect is the causative agent of the patient’s ARDs is Aspergillus. We believe so because Aspergillus is a plant and animal pathogen that is initially a white colony that becomes black or brown as the culture matures. • • • • • • • Would you expect to see other spores present under the scope? If so, what type? 2 points o Yes, you would expect to see other spores present under the scope. The type of spores you would see would be normal fungal flora which help to ensure that pathogenic fungi do not cause infections. Also, humans inhale a variety of different spores throughout the day which can get stuck in their respiratory tract. Even if these spores are not severe enough to cause health problems, they would see be present under the scope. What phyla does this organism belong to? How did you determine its classification? Name at least two other medically relevant members of this phyla. 2 points o Aspergillus belongs to the Ascomycota phylum. We determined its classification based on the description of the culture. When looking at the white rim of the colony in the microscope, the hyphae and the chains of the conidiospores are present. Fungi in the Ascomycota phylum produce conidiospores both asexually and sexually. Two other medically relevant members of this phyla would be Candida albicans and Penicillium. Based on this finding, what type of treatment should this patient be started on? 2 points o The type of treatment this patient should be started on is an antifungal treatment called itraconazole. This is an antifungal medication that is used in adults to treat infections caused by fungus. This treatment is given to patients who are allergic to Aspergillus. Because her symptoms only consist of a fever, coughing, and abnormal breathing, she should be started on itraconazole. Her infection should not be invasive based on her symptoms and no preexisting health conditions. Who usually gets this disease type of disease? 2 points o Aspergillus is commonly found in the environment and it usually affects people with weakened immune systems. Especially if the individual has other lung diseases, has asthma, taking corticosteroids, and other factors that affects immune systems. How do individuals acquire the disease and from where? 2 points o All individuals usually breathe in aspergillus spores all the time from being outside, however, only those with weakened immune systems are the ones who develop the aspergillosis disease. How common is the disease? In the U.S. how many people are usually hospitalized annually with the disease? 2 points o It is difficult to determine the how common this disease is as it is not reportable. Invasive forms of aspergillosis is more uncommon than the allergic forms. Allergic aspergillosis affects between 1-15% of cystic fibrosis patients and around 4.8 million people have allergic aspergillosis worldwide. In 2014, 15,000 people were hospitalized due to aspergillosis related complications. Is the disease serious? Can it be fatal? What is the prognosis for this patient? 2 points This disease is not serious unless the patient has preexisting immune problems. This disease can be fatal to patients who went through an organ transplant or stem cell transplant. The prognosis for this patient would be that the patient most likely has a form of allergic aspergillosis. Because she has no pre-existing health conditions that have severely affected her, she will most likely be able to fully recover. How can the disease be prevented? 2 points o It can be prevented by avoiding dusty areas or using N95 masks. Avoiding yard work that involves dirt or dust is also advised as well as wearing long sleeves, gloves and pants which can also help prevent this disease. Washing hands and taking antifungal medications would also prevent infections. o •