The Uninoculated MDCK Cell Lin - Essay Example

Case Study 1) What is the of the stain used in specimen 1a? Answer: The stain used for the sputum smear is acid-fast stain such as Ziehl-Neelsen acid-fast. The bacteria appear red (due to Carbol Fuchsin) as they are acid-fast and do not stain with Gram stain and the epithelial cells appear blue. 2) What is the culture medium employed in specimen 1b? Answer: The culture medium of the agar slope is LJ or Löwenstein–Jensen medium. 3) Suggest, with reasons, a likely diagnosis for this patient. Answer: The 25-year old nurse has likely been infected by the TB-bacteria, i.e. Mycobacterium tuberculosis. The patient had initially complained of fatigue and loss of appetite. But in a month’s time she had developed persistent dry cough, all of which are symptoms of tuberculosis. 4) Assuming that a diagnosis was made at the hospital on the basis of laboratory investigation of her sputum, the nurse’s diagnosis took one month. Why do you think the nurses and doctor at occupational health might have suspected the diagnosis and so reduced this time? Answer: The symptoms of tuberculosis may be hard to diagnose if it is in latent form. Although it is not known whether the exposure to the bacteria was recent or not, the patient had started exhibiting the general symptoms of tuberculosis. The patient also came from one of the African nations where TB is endemic. These were indicative of tuberculosis as the cause of illness. Mantoux tuberculin skin test or Heaf test may be used to confirm the diagnosis and immediate hospitalisation and medication is required. 5) What implications for Infection Control in the hospital does this case have? Answer: TB is a highly contagious disease and its onset in individuals in a locality has to be recorded and notified to all local and state health departments to formulate a control and prevention plan. Every health department has to ensure a complete and timely investigation for suspected TB cases reported in its area. Case Study 2: 1) Suggest, with reasons, the likely pathogen responsible for the baby’s symptoms. Answer: The baby is immunosuppressed and has likely been infected by the fungi, Pneumocystis jirovecii, which causes pneumonia due to lung infection. It is known to be an opportunistic pathogen and has, therefore, affected the baby’s lungs causing fever, cough and respiratory distress. 2) What is the condition it causes and what is the likely treatment for this condition? Answer: The lungs are the usual target site and the pathogens cause the alveolar walls to thicken leading to a state of oxygen deprivation or hypoxia. This causes shortness of breath and chest pain. 3) Why do you think it is so difficult to prevent susceptible children from being infected with this pathogen? Answer: The pathogen for PCP, Pneumocystis, is found in the lungs of healthy individuals but it causes infection only in people who have weak immune systems. Children are especially susceptible to diseases as they do not have fully developed immune systems, and in this case, the patient is also HIV+ve. Case Study 3: 1) Compare the uninoculated MDCK cell line with the one inoculated with the patient NPA. What is the effect observed on NPA-inoculated MDCK cells known as? Answer: Sample 3a containing MDCK monolayer after incubation with patients NPA sample clearly indicates cytopathogenic effect on the cells when compared to the uninoculated MDCK cell sheet in sample 3b. This is an indication of viral infection. 2) What is your diagnosis based upon the results of the tissue culture assay plus the clinical information provided? Answer: The symptoms observed in the patient which include fever, chills, headache, runny nose and sore throat suggest that she may have contracted the flu. The doctor examining her at the clinic also suspected the same and the NPA test also confirms that she has been infected by the influenza virus. 3) What method(s) might you use to confirm the identification of the virus present and why is doing this important? Answer: Some of the methods that can be used to isolate and identify viruses are by using Monkey liver cells, MDCK and LLC-MK2 cell cultures; Haemagglutination Inhibition Test; and by using Immunofluoresense techniques, specifically designed for viruses causing respiratory infections (Wong 2013). It is important to identify a particular virus to understand its nature like mutability or structural plasticity and transmission channels. Influenza virus can cause acute febrile respiratory illness and at a global scale. The influenza virus can replicate in birds and pigs through antigenic shift or re-assortment. Thus, the viruses can become highly virulent and difficult to manage. Some of the factors to consider while dealing with influenza virus are the host factors like immune-competence of the host, viral factors like evolution of antigenic variance, entry points of virus into hosts, symptoms in patients and transmission to others. It is important to understand the viral immune defence mechanisms to provide better treatment options to patients and prevent pandemic outbreaks (Behrens and Stoll 2009). 4) Record the macroscopic appearance of Samples 3c and 3d. In this case, the laboratory refused to process Sample 3d and requested a replacement be collected. Why did they do this? Answer: The sputum sample in 3c is green and purulent indicating pus forming bacterial infection in the lungs. The reason why sample 3d may have been rejected was because the sample had been taken from another patient and could neither be treated as normal/control nor would it help in further diagnosis of the patient. 5) What alternatives to sputum might be collected for analysis of lower respiratory tract infection and what are the advantages and disadvantages of these samples compared to a sputum sample? Answer: Other than the primary physical examination of chest and listening to bronchial breathing, chest X-rays, pulse oximetry, CBC blood tests and Arterial Blood Gases can confirm pneumonia. Chest radiograph and CAT scans are also recommended to determine the extent of spread and severity of the illness (Gelfand 2007). 6) Examine and record the colonial morphology observed in Sample 3e. What is the significance of the zone around the optochin disc? What is your presumptive identification of the pathogen isolated from the lower respiratory tract and blood? What further test(s) could you perform to confirm the identification? Answer: Sample 3e is an inoculation of the Gram positive cocci obtained from the patients sputum sample on blood agar. The colonies appear green in colour and mucoid. An inhibition zone can also be observed around the Optochin test filter paper. This test is used to determine the presence of pneumococci as they selectively inhibit S. pneumoniae even at low concentrations. Also, the colonies of Streptococcus pneumoniae have such an appearance as observed in sample 3e. They produce pneumolysin which causes breakdown of haemoglobin into a green pigment. An additional test can be the Bile Solubility Test which refers to the addition of bile salts to accelerate the lytic reaction rate by increasing the activation of autolytic enzymes Streptococcus pneumoniae. It results in the colonies disappearing and the green zones become less turbid or clear. Serological tests can then be performed. (Bakdash 2003) 7) This patient appears to have been suffering from two infections, one viral and one bacterial. What is your overall diagnosis in this case? Answer: The patient exhibits symptoms for viral influenza as well as bacterial pneumonia. Her initial symptoms were fever, chills, headache, neck pain, sore throat and runny nose which are symptoms of influenza, caused by a virus. The NPA collected at the time was shown to cause cytopathic effect on MDCK cell layers corroborating influenza. Although, her symptoms had shown slight improvement over the next one week, her condition became worse soon after that. Her symptoms now included high fever, productive cough and shortness of breath. She exhibited low blood pressure with partial pressure of oxygen in the ABG test as low as 55.8mmHg. Her blood and sputum culture showed an infection with Gram positive cocci which were cultivated on blood agar and showed the infection to be bacterial pneumonia caused by Streptococcus pneumoniae. Also the fact that the patient was a long time smoker and was above the age of 65 meant that her immunity was lower than the average person. (Mayo Clinic 2013) Case Study 4: 1) Examine Sample 4a and record the colonial morphology. What is the halo effect known as? What bacterial factor is responsible for producing this effect? Answer: Sample 4a is a blood agar culture plate containing gray-white colonies that are glossy and translucent. The small punctiform colonies have clear halos around them. This is probably because the bacteria are capable of capable of breaking down the blood cells present in the agar. The clear halos indicate Beta-hemolysis pattern usually associated with Streptococcus pyogenes (Port 2010). 2) What is the most likely species of a pathogen present? Give reasons for your answer. Answer: The patient has fever, sore throat and swollen, red tonsils covered with purulent exudate. The throat swab is cultured on blood agar and the plate develops small colonies with tell-tale clear halos. The patient is, therefore, likely to be suffering from Strep throat or infection caused by Streptococcus pyogenes which demonstrates β-haemolysis on blood agar and symptoms that the patient exhibits. References: 1. Backdash, S. (2003). Microbiology Diagnosis. Available: http://path.upmc.edu/cases/case349/microbiol.html. Last accessed 1st July 2013. 2. Behrens, G & Stoll, M. (2009). Pathogenesis and Immunology. Available: http://www.influenzareport.com/ir/pathogen.htm. Last accessed 28th June 2013. 3. Gelfand, J.L. (2007). Bacterial Pneumonia. Available: http://www.webmd.com/lung/bacterial-pneumonia?page=2. Last accessed 2nd July 2013. 4. Mayo Clinic Staff. (2013). Pneumonia. Available: http://www.mayoclinic.com/health/pneumonia/DS00135/DSECTION=risk-factors. Last accessed 2nd July 2013. 5. Port, T. (2010). Beta haemolysis on blood agar bacterial growth media. Available: http://www.helium.com/items/1783109-beta-hemolysis-blood-agar. Last accessed 2nd July 2013. 6. Wong, D. (2013). Diagnostic Methods in Virology. Available: http://virology-online.com/general/Test1.htm. Last accessed 2nd July 2013. Read More