chp 15 microbe pathogenicity worksheet-1 (1)

BIO208 Lectures 18-20: Microbial mechanisms of pathogenicity, Chapter 15 Fill in the blank 1. A microbe that causes disease is called a pathogen . 2. Infections that may go unnoticed because of the absence of symptoms are called asymptomatic/subclinical, latent disease infections. 3. A person steps on a rusty nail and develops tetanus. In this case, the person has acquired a(n) noncommunicable, pathogen . Word Bank • Disease • Infection • Asymptomatic/subclinical • Infectious disease • Communicable • Contagious • Nosocomial disease • Zoonotic disease • Noncommunicable • Noninfectious disease • Acute disease • Chronic disease • Latent disease • Pathogen Which of the following statements about the development of infectious diseases is correct? A. The prodromal period is characterized by the most severe symptoms. B. During the incubation period, the infected individual exhibits obvious signs of sickness. C. The period of decline is the time during which the person regains health and recovers back to the pre-disease state. D. The period of illness is the time when the height of infection occurs. E. The number of pathogen particles in the patient increases during the period of decline. Which of the following violates Koch’s postulates? A. Infection of a healthy individual with M. tuberculosis bacteria causes development of tuberculosis. B. M. tuberculosis is resistant to many types of antibiotic. C. V. cholera bacteria can be isolated from both cholera patients and healthy individuals. D. S. pyogenes bacteria can only grow on highly nutritious media. The most common characteristics of Covid-19 infection are listed below. Categorize each as a sign or symptom: • Fever or chills • Cough • Shortness of breath or difficulty breathing • Fatigue • Muscle or body aches • Headache • New loss of taste or smell • Sore throat • Congestion or runny nose • Nausea or vomiting • Diarrhea What are the limitations of Koch’s postulates in determining the cause of the following diseases? • Cancer- Koch’s postulates link a pathogen to an infectious disease but cannot account for genetic or environmental causes of disease. Cancer is caused by many factors, including genetics, environment, and sometimes microbes. • HIV- Koch’s postulates require external measures of diseases. The incubation period of HIV is long, so a person may not exhibit signs of disease until much after the initial viral infection. It is also impossible to make a pure culture of a virus because it requires co-growth with a host cell. Humans 1

are also a major host of HIV, but cannot be studied on. You would have two mates that can be infected with the virus. • Tuberculosis ( Mycobacterium tuberculosis grows very slowly)- The slow growth rate of M. Tuberculosis would make it difficult to link the bacteria to tuberculosis disease. It would not be impossible, but you would have to wait a very long time for the pure culture to grow. • Staphylococcus aureus is present in carriers but can also cause disease- Because S. aureus is also present in healthy individuals, it would confuse the results of Koch’s postulates. If you isolate S. aureus from the health control animal that isn’t sick, you can’t link it to the disease in the sick animal where it may be present. A rabbit was found to have floppy ear disease, which causes long-ear infections. Its etiology is unknown. Unknown Microorganism X from the infected rabbit’s right ear is successfully isolated and cultured on laboratory growth media. The ear of a healthy laboratory rabbit is then inoculated with isolated microorganism, and after a period of time, no disease is observed. Which of the following statements accurately describe(s) the conclusion(s) that can be drawn from the experiment?  The microorganism should be injected in another type of animal to follow Koch’s postulates.  Because microorganism X is found in nature, it is not possible to isolate and culture it in the lab.  Microorganism X might not be linked to floppy ear disease, because the inoculated rabbit remained healthy.  Microorganism X modified its cell wall structure while being cultured, and is no longer infectious to rabbits.  Health laboratory organisms rarely show signs and symptoms of infection and disease.  Microorganism X is the etiological agent for floppy ear disease because it caused infection in the diseased rabbit. Which statements accurately describe Koch’s postulates?  The microscopic properties of pathogens isolated from the original (diseased) and inoculated (also diseased) animals should differ significantly.  The pathogen must be isolated from the diseased host and grown in pure culture.  The pathogen must be isolated from the inoculated animal and must be shown to be in the original organism.  The pathogen from the pure culture must cause the disease when it is inoculated into a healthy, susceptible laboratory animal.  The same pathogen must be present in every case of the disease. What is the difference between a pathogen’s infective dose (ID50) and lethal dose (LD50)? A. LD50 is a measure of virulence and ID50 determines cause of disease. B. ID50 is determined by measuring active infection (signs/symptoms), LD50 is determined by measuring death. C. ID50 can be measured experimentally, LD50 cannot be measured experimentally. D. Contagious diseases have a high ID50 and noncommunicable diseases have a low ID50. From this table, which microbe(s) are pathogenic? 2

Staphylococcus aureus is a gram-positive, facultative anaerobe, and a normal constituent of the nose/throat and skin. A 42-year-old male with a history of high blood pressure and cholesterol went to the hospital complaining of chest pain and ultimately underwent emergency open-heart surgery. Three days after surgery the patient became very ill with a Staphylococcus aureus infection at the surgical site. In this scenario, what is the normal microbiota on the skin? How did conditions change? S. aureus went from the surface of the skin to deeper skin layers at the surgical incision. In the new location, it can grow and colonize the patient, resulting in infection. What is the opportunistic pathogen? S. aureus Categorize each as an exoenzyme, endotoxin, or, exotoxin, and write how it enables a microbe to infect and invade 1. Lipopolysaccharide endotoxin causes systematic inflammation to befuddle the immune system 2. Urease produced by H. pylori exoenzyme that neutralizes stomach pH so that H. pylori can grow in the stomach 3. Hyaluronidase is produced by streptococci and staphylococci exoenzyme that breaks apart cell connections so microbe can move through host tissues and find nutrients and spaces to colonize and infect 4. Systemic effect on many tissues and organs exotoxin can disrupt the function of the host’s tissues and allow for the microbe to colonize 5. Fever-inducing endotoxin can befuddle the immune system 6. Collagenase exoenzyme that breaks apart cell connections so microbe can move through host tissues and find nutrients and spaces to colonize and infect 7. Botulinum toxin exotoxin that causes flaccid paralysis and muscle dysfunction 1. Which have an effect on the signs/symptoms of a disease? A, B, C 2. Which have an effect on the portal of entry for a microbe? D, E 3. Which have an effect on the portal of exit for a microbe? D, E A. Exoenzymes B. Endotoxin C. Exotoxin D. Adhesion factors E. Mode of transmission A patient has a bacterial infection and circulating levels of bacterial toxin in their body. After treatment with an antibiotic, toxin concentration in their body increases sharply before falling to zero. What type of bacterial infection and toxin did the patient have? A. Gram positive bacteria, endotoxin B. Gram positive bacteria, exotoxin C. Gram negative bacteria, endotoxin D. Gram negative bacteria, exotoxin A positive antibody test for HIV infection would be a _____ of infection. A. sign B. symptom C. syndrome D. defense E. transmission 4