5.1

Parts of Bacterial Cell

Prokaryotic cells are simple in structure, with no recognizable organelles. They have an outer cell wall that gives them shape. Just under the rigid cell wall is the more fluid cell membrane. The cytoplasm enclosed within the cell membrane does not exhibit much structure when viewed by electron microscopy. Nucleoid: DNA in the bacterial cell is generally confined to this central region. Though it isn't bounded by a membrane, it is visibly distinct (by transmission microscopy) from the rest of the cell interior. Genophore: The genophore, sometimes referred to as the bacterial chromosome, is a long double strand of DNA, usually in one large circle. It includes most of the genetic material of the organism (see Plasmid). Plasmid: Plasmids are small circular DNA fragments found in the cytoplasm that contain code responsible for antibiotic resistance and other characteristics. Plasmids and the associated traits can be transferred between bacteria, even from one bacterial species to another. Cytoplasm: This internal "soup" of the bacterial cell is bounded on the outside by the cell envelope. The cytoplasm is mostly water, but within it are the bacterial inclusions - nucleoid, plasmids, ribosomes and storage granules - as well as the components necessary for bacterial metabolism. Endospore: Some bacteria can survive hostile environments, often for long time periods, by bundling their genetic material in a tough internal structure. Endospores can withstand heat, cold, radiation, and lack of nutrition. Ribosomes: Ribosomes give the cytoplasm of bacteria a granular appearance in electron micrographs. Though smaller than the ribosomes in eukaryotic cells, these inclusions have a similar function in translating the genetic message in messenger RNA into the production of peptide sequences (proteins). Storage Granules: Nutrients and reserves may be stored in the cytoplasm in the form of glycogen, lipids, polyphosphate, or in some cases, sulfur or nitrogen. Cell Envelope Beginning from the innermost structure and moving outward, bacteria have some or all of the following structures Plasma Membrane: This is a lipid bilayer much like the cytoplasmic (plasma) membrane of other cells. There are numerous proteins moving within or upon this layer that are primarily responsible for transport of ions, nutrients and waste across the membrane. Periplasmic Space: This cellular compartment is found only in those bacteria that have both an outer membrane and plasma membrane (e.g. Gram negative bacteria). In the space are enzymes and other proteins that help digest and move nutrients into the cell. Cell Wall: Composed of peptidoglycan (polysaccharides + protein), the cell wall maintains the overall shape of a bacterial cell. The three primary shapes in bacteria are coccus (spherical), bacillus (rod-shaped) and spirillum (spiral). Mycoplasma are bacteria that have no cell wall and therefore have no definite shape. Outer Membrane: This lipid bilayer is found in Gram negative bacteria and is the location of lipopolysaccharide (LPS) in these bacteria. Gram positive bacteria lack this layer. LPS can be toxic to a host and can stimulate the host's immune system. Capsule: This layer of polysaccharide (sometimes proteins) protects the bacterial cell and is often associated with pathogenic bacteria because it serves as a barrier against phagocytosis by white blood cells. Capsules can be seen by viewing bacteria in India ink. Appendages Bacteria may have the following appendages. Pili, Fimbriae: These hollow, hairlike structures made of protein allow bacteria to attach to other cells. A specialized pilus, the sex pilus, allows the transfer of plasmid DNA from one bacterial cell to another. Pili (sing., pilus) are also called fimbriae (sing., fimbria). Flagella: The purpose of flagella (sing., flagellum) is motility. Flagella are long appendages which rotate by means of a "motor" in the cell envelope. Bacteria may have one, a few, or many flagella in different positions on the cell.

Nitrate Reduction Test:

Test to determine if an organism is capable of reducing nitrate to nitrite or other nitrogenous compounds via the action of the enzyme nitratase. If nitrite is present in the media, it will react with nitrate I and nitrate II to form a red compound (a positive result). If no red color forms, zinc is added to the broth to convert any remaining nitrate to nitrite. If no color change occurs upon the addition of zinc, then this means that the nitrate was converted to some other undetectable form of nitrogen (a positive result).

Arabinose Test:

Test to determine if the microbe can ferment the sugar arabinose as a food source. The microbe is incubated in phenol red arabinose broth for 24 hours. If the microbe ferments arabinose, the media become acidic, causing a color change from red to yellow.

Glucose Fermentation Test:

Test to determine if the microbe can ferment the sugar glucose. The microbe is grown in a broth that contains glucose and the pH indicator, phenol red. If an organism is capable of fermenting the sugar glucose, then acidic byproducts are formed and the pH indicator turns yellow.

Lactose Fermentation Test:

Test to determine if the microbe can ferment the sugar lactose as a food source. The microbe is incubated in phenol red lactose broth for 24 hours. If the microbe ferments lactose, the media become acidic, causing a color change from red to yellow.

Citrate Utilization Test:

Test to determine if the microbe can use citrate as its sole source of food. It is often used to differentiate between members of Enterobacteriaceae. If an organism is capable of utilizing citrate as a carbon source, CO 2 is produced. If CO 2 is produced, it reacts causing the pH indicator (bromthymol blue) in the media to turn from green to blue.

Lysine Decarboxylase Test:

Test to determine if the microbe can use the amino acid lysine as a food source. The microbe is incubated in lysine decarboxylase broth. The microbe must first use the glucose present to cause the pH to drop, which causes the color to change from purple to yellow. Once the medium has been acidified, the enzyme lysine decarboxylase is activated. The culture is incubated an additional 24 hours at 35- 37 C to allow the microbe to now use the lysine. The final results are then observed at 48 hours. Change back to purple from yellow indicates a positive test for lysine decarboxylase. Failure to turn yellow at 24 hours or to revert back to purple at 48 hours indicates a negative result.

Ornithine Decarboxylase Test:

Test to determine if the microbe can use the amino acid ornithine as a food source. The microbe is incubated in ornithine decarboxylase broth. The microbe must first use the glucose present to cause the pH to drop, which causes the color to change from purple to yellow. Once the medium has been acidified, the enzyme ornithine decarboxylase is activated. The culture is incubated an additional 24 hours at 35-37 C to allow the microbe to now use the ornithine. The final results are then observed at 48 hours. Change back to purple from yellow indicates a positive test for ornithine decarboxylase. Failure to turn yellow at 24 hours or to revert back to purple at 48 hours indicates a negative result.

Gelatin Hydrolysis:

Test to determine if the microbe can use the protein gelatin as a source of carbon and energy for growth. The microbe is incubated in nutrient gelatin. If the microbe uses gelatin, the medium changes from semisolid to liquid and cannot be resolidified.

Voges-Proskauer Test (VP Test):

Test to determine if the microbe produces acetoin as a fermentation product from glucose. If the culture is positive for acetoin, it will turn brownish-red to pink. If the culture is negative for acetoin, it will turn brownish-green to yellow.

Indole Test:

Test to determine if the microbe produces indole as a byproduct from the metabolism of the amino acid tryptophan. If indole is produced, it will react with a chemical reagent added after incubation to produce a color change. There are two media that are used for this test: Sulfide-Indole- Motility (SIM) medium and Tryptone broth medium. In SIM media, indole reacts with added Kovac's reagent to form rosindole dye which is red in color

H2S:

Test to determine if the microbe reduces sulfur-containing compounds to sulfide during metabolism. If sulfide is produced, it combines with iron compounds to produce FeS, a black precipitate. Several media containing iron compounds allow detection of hydrogen sulfide production. One medium used is Sulfide-Indole- Motility (SIM) medium. This is a nutrient medium allowing the detection of three different traits in bacteria and contains sulfates to serve as the substrate for detecting sulfide production.

Motility Test:

Test to determine whether an organism is equipped with flagella and thus capable of swimming away from a stab mark. If the entire tube is turbid, or cloudy, this indicates that the bacteria have moved away from the stab mark and are motile. If the stab mark is clearly visible and the tube is not turbid, the organism is likely non-motile.

Urease Test:

Test to identify bacteria capable of hydrolyzing urea using the enzyme urease. The hydrolysis of urea forms the weak base, ammonia, as one of its products. This weak base raises the pH of the media and the pH indicator, phenol red, turns from yellow to pink.

Oxidase:

Test to identify microorganisms containing the enzyme cytochrome oxidase (important in the electron transport chain). It is commonly used to distinguish between oxidase negative Enterobacteriaceae and oxidase positive Pseudomadaceae. In the oxidase test, artificial electron donors and acceptors are provided. When the electron donor is oxidized by cytochrome oxidase it turns a dark purple.

Catalase Test:

Test to identify organisms that produce the enzyme catalase. This enzyme detoxifies hydrogen peroxide by breaking it down into water and oxygen gas. The bubbles resulting from production of oxygen gas clearly indicate a catalase positive result.

Intro Summary

The medical examiner who performed Anna Garcia's autopsy pulled copies of Anna's medical records before proceeding with the autopsy. Interestingly, the medical examiner discovered that Anna had been hospitalized just ten days prior to her death for a sickle cell crisis and subsequently was treated for an infection that was most likely acquired during her hospital stay. The medical examiner then noted that pieces of the medical history are incomplete. Throughout this lesson, you will play the role of medical detectives in order to investigate Anna's mystery infection. Ultimately, you will need to identify the exact pathogen, or infectious agent, responsible for Anna's illness. An infection results when a pathogen invades and begins growing within a host. Disease occurs if and when the invasion and growth of a pathogen impair bodily functions. In order to cause disease, pathogens must enter the host body, adhere to specific host cells, invade and colonize host tissues, and inflict damage on those tissues. Entrance to the host typically occurs through openings to the body such as the mouth, eyes, nose, genital openings, or through breaks in the skin. Infectious agents that are easily transmitted are considered highly contagious. Those agents that that are very likely to cause disease once transmitted are considered highly virulent. The most troublesome infectious agents are those that are both highly contagious and virulent. You will begin your detective work by exploring the different types of pathogens as well as examining specific examples of each type in order to identify what is plaguing Anna. There are six major types of infectious agents: bacteria, viruses, fungi, protozoa, helminthes, and prions. You will investigate a variety of diseases caused by infectious agents and use this information to determine the tests you will need to perform in the subsequent activities to fill in the missing pieces from Anna's medical history. In this activity you will demonstrate the transmission of an unknown infectious agent from person to person as well as use deductive reasoning to determine "patient zero," the initial patient in the population to develop the infection. You will now play the role of a microbiologist specializing in diagnostic microbiology. A microbiologist is a scientist who investigates the growth, structure, development, and other characteristics of microorganisms, such as bacteria. Diagnostic microbiology is a specialty within microbiology concerned with the isolation and identification of bacteria in a specimen from a patient. Specimens taken from a patient sample usually contain a mixture of different bacteria. Pure cultures, or samples with only one type of bacteria, are necessary to accurately study a bacterial species. Therefore it is necessary to isolate all of the possible pathogenic or disease causing organisms in order to study the sample by itself. Once you have isolated individual colonies, you can use these colonies for identification tests. Bacteria grow in groups called colonies, on a growth media called agar. A sample of the specimen is streaked onto an agar plate in order to physically separate the bacterial colonies. Whenever working with microorganisms, it is important to observe the rules of aseptic technique. Aseptic technique refers to a procedure performed under sterile conditions. Aseptic technique assures that contaminants are not introduced into a specimen and that infectious agents are not spread to you or laboratory surfaces. While gross examination of unknown bacteria is helpful in eliminating some possibilities, it is rarely sufficient alone to identify unknown bacteria due to the large amount of bacterial species and degree of variation between them. Therefore, further tests are required. All bacteria are divided into two main groups, depending on how they react to a specific set of dyes called the Gram stain. A microbiologist named Hans Christian Gram developed the staining protocol in the 1880s, and it remains one of the first steps in classifying or identifying bacteria. If the bacteria appear purple after being treated with the stain, they are classified as Gram positive. The bacteria are considered to be Gram negative if they appear pink. A Gram stain is usually one of the first steps in identifying bacteria. In addition to the gram stain, the morphology, or structure, of the bacteria can also be observed. There are three basic morphologies of bacteria (based on the shape of a single cell): bacillus (rod), coccus (sphere), and spirillum (spiral). In this activity you will create bacterial smears on microscope slides and perform a Gram stain on three types of bacteria, including the bacteria isolated from Anna's sample. You will look at the stained samples under the microscope and identify the morphology of the bacteria as well as whether the bacteria are Gram positive or Gram negative. You will be working with live bacteria and dyes that permanently stain clothes, the floor, and counter tops. Read all the directions carefully before beginning and follow all safety precautions. If you have questions, ask your teacher. As a medical detective, you have now identified that because Anna was treated with antibiotics, it means that she was diagnosed with a bacterial infection. In order to determine the exact species of bacteria, the next step is to culture or grow bacteria from Anna's urine sample. Luckily, the laboratory that originally cultured Anna's urine has preserved a sample that you can use for further tests. In this activity you will use aseptic technique to isolate bacterial colonies from four samples, including Anna's, and then complete a gross examination of the colonies from Anna's sample. In the last activity, you isolated the bacteria that was responsible for Anna's illness and performed a gross examination of the resultant colonies. The identification of a bacterial species is based on many factors, including cell and colony morphology, chemical composition of cell walls, biochemical activities, and nutritional requirements. You have now streaked a bacterial culture onto an agar plate in order to isolate individual colonies, which can be used in identification tests. You then grossly examined the bacterial colonies. In the last activity, you began your preliminary identification by comparing the basic morphology of the bacterial cells and completing a Gram stain reaction. The final step in determining the bacterial species plaguing Anna is to perform biochemical tests. Biochemical tests are the most definitive way to identify bacterial species. They determine what growth media the bacteria will grow on and identify the end products of their metabolic processes, such as the wastes they excrete. Many tests often need to be performed in order to positively identify a bacterium. In the last activity, you identified that Anna's bacterial sample is a Gram negative rod-shaped bacteria. In this activity you will analyze the results of various biochemical tests in order to identify the unknown bacterial species infecting Anna Garcia. In this lesson you were introduced to a mystery illness infecting Anna just ten days before her untimely death. When a body is attacked by foreign invaders, such as the bacteria infecting Anna, the body mounts a defense to fight off these unwanted pests. Inside your body is an amazing system called the immune system that is made up of a network of cells, tissues, and organs that work together to protect the body. In this activity you will explore how the body's immune system works to defend against the millions of bacteria, microbes, viruses, toxins, and parasites that are constantly trying to invade your body. You will design a board game or a children's book that showcases how the immune system works to fight infection.

Disease Cards

Tuberculosis Type of Infectious Agent Bacteria Name of Infectious Agent Mycobacterium tuberculosis Symptoms of Disease The symptoms of TB disease depend on where in the body the bacteria are growing. Usually, TB bacteria grow in the lungs where they cause a bad cough that lasts 3 weeks or longer, pain in the chest, and coughing up blood or the phlegm from deep inside the lungs. Other symptoms include weakness, fatigue, weight loss, no appetite, chills, fever, and sweating at night. Diagnosis of Disease Skin test, blood test, chest X-ray, and sputum culture. Transmission of Disease TB is spread through the air from one person to another. The TB bacteria are put into the air when a person with TB disease of the lungs or throat coughs, sneezes, speaks, or sings. People nearby may breathe in these bacteria and become infected. Treatment of Disease Antibiotic treatment with isoniazid (INH), rifampin (RIF), or rifapentine (RPT). Strep Throat Type of Infectious Agent Bacteria Name of Infectious Agent Streptococcus pyogenes Symptoms of Disease General symptoms include throat pain, difficulty swallowing, red and swollen tonsils that often have white patches or streaks of pus on them, tiny red spots on the soft or hard palate, swollen and tender lymph nodes in the neck, fever, headache, rash, and fatigue. Diagnosis of Disease Throat culture, rapid antigen test, and/or rapid DNA test. Transmission of Disease Streptococcal bacteria are highly contagious. They can spread through airborne droplets when someone with the infection coughs or sneezes, or through shared food or drinks. You can also pick up the bacteria from a doorknob or other surface and transfer them to your nose or mouth. Treatment of Disease Oral antibiotic treatment with penicillin, amoxicillin, erythromycin, or azithromycin. Syphilis Type of Infectious Agent Bacteria Name of Infectious Agent Treponema pallidum Symptoms of Disease Primary syphilis - small sore on genitals Secondary syphilis - Rash that begins on trunk and covers entire body and may be accompanied by wart-like sores in the mouth or gential area. Muscle aches, fever, sore throat and swollen lymph nodes are also common. Latent syphilis - No symptoms Tertiary or late syphilis - Brain, nerve, eye, heart, blood vessel, liver, bone, and joint damage. Diagnosis of Disease Blood test for presence of antibodies, fluid culture from sores, or spinal tap. Transmission of Disease Spread through contact with an infected person's sore during sexual activity. The bacteria enter your body through minor cuts or abrasions in your skin or mucous membranes. Syphilis is contagious during its primary and secondary stages, and sometimes in the early latent period. It is also spread through direct unprotected close contact with an active lesion or through an infected mother to her baby during pregnancy or childbirth. Treatment of Disease Antibiotic treatment with penicillin. Giardiasis Type of Infectious Agent Protozoa Name of Infectious Agent Giardia lamblia parasite Symptoms of Disease A gastrointestinal disease with water, sometimes foul-smelling diarrhea that may alternate with soft, greasy stools, fatigue, abdominal cramps and bloating, belching gas with a bad taste, nausea, and weight loss. Diagnosis of Disease The infection is diagnosed with a stool sample. Transmission of Disease Giardia parasites live in the intestines of people and animals. Before the microscopic parasites are passed in stool, they become encased within hard shells called cysts, which allows them to survive outside the intestines for months. Once inside a host, the cysts dissolve and the parasites are released. Infection occurs when you accidentally ingest the parasites. This can occur by swallowing contaminated water, by eating contaminated food, or through person-to-person contact. Treatment of Disease Administration of medications specific to giardia infection (including metronidazole, tinidazole, nitazoxanide, and paromomycin). Malaria Type of Infectious Agent Protozoa Name of Infectious Agent Plasmodium parasite Symptoms of Disease Malaria causes damage to red blood cells which can cause serious and sometimes fatal complications. The disease is characterized by recurrent attacks with moderate to severe shaking chills, high fever, profuse sweating as the body temperature falls, headache, nausea, vomiting, and diarrhea. Diagnosis of Disease Blood test for the parasite. Transmission of Disease Microscopic parasites transmit the disease from person to person. A mosquito becomes infected by feeding on a person who has malaria and then transmits the malaria parasites to the next person the mosquito bites. Malaria can also be transmitted from mother to unborn child, through infected blood transfusions, and by sharing infected needles. Treatment of Disease Administration of antimalarial drugs. Cryptosporidiosis Type of Infectious Agent Protozoa Name of Infectious Agent Cryptosporidium parvum parasite Symptoms of Disease A gastrointestinal disease whose symptoms include watery diarrhea, dehydration, weight loss, stomach cramps or pain, fever, nausea, and vomiting. Diagnosis of Disease The infection can be diagnosed with an acid-staining test which identifies cryptosporidium under the microscope or a stool culture. Transmission of Disease The infection begins when you ingest the parasite which then travels to your intestinal tract and settles into the walls of your intestines. You can become infected with cryptosporidium by touching anything that has come in contact with contaminated feces. Methods of infection include swallowing or putting something contaminated in your mouth, drinking contaminated water, swimming in contaminated water and accidentally swallowing some of it, touching your hand to your mouth if you had comes into contact with a contaminated surface, or having close contact with other infected people or animals. Treatment of Disease Administration of anti-parasitic drug, anti-motility agents to slow down the movements of the intestines, and fluid replacement therapy. Creutzfeldt-Jakob Disease (CJD) Type of Infectious Agent Prion Name of Infectious Agent CJD Prion Symptoms of Disease CJD is marked by rapid mental deterioration, usually within a few months. Initial signs and symptoms typically include personality changes, anxiety, depression, memory loss, impaired thinking, blurred vision, insomnia, difficulty speaking, difficulty swallowing, and sudden jerky movements. As the disease progresses, mental symptoms worsen and people eventually lapse into a coma. Diagnosis of Disease Doctors commonly use an EEG, MRI, spinal fluid tests, and/or tonsil biopsies to diagnose the disease. Transmission of Disease CJD disease is caused by an abnormal version of a kind of protein called a prion. Normally the proteins are harmless, but when they're misshapen they become infectious and can cause major problems on normal biological processes. Most people with CJD develop the disease for no apparent reason, but others who develop the disease have a family history of the disease or test positive for a genetic mutation associated with CJF. A small number of people have developed CJD after being exposed to infected human tissue during a medical procedure. This happens because standard sterilization methods do not destroy abnormal prions. Treatment of Disease No effective treatment exists for Creutzfeldt-Jakob disease or any of its variants. Ascariasis Type of Infectious Agent Helminth Name of Infectious Agent Ascariasis worm Symptoms of Disease After the ascariasis eggs are ingested, they hatch in the intestines and sometimes migrate through the bloodstream or lymphatic system into the lungs. An intestinal infection can cause abdominal pain, nausea and vomiting, diarrhea or blood stools, and/or fatigue. A lung infection can cause persistent cough, shortness of breath, and/or Wheezing. Diagnosis of Disease Infection is identified by stool tests, blood tests, and/or imaging tests. Transmission of Disease A person must come into contact with soil mixed with human feces that contains ascariasis eggs. Treatment of Disease Administration of anti-parasite medications. Trichinosis Type of Infectious Agent Helminth Name of Infectious Agent Trichinella roundworm Symptoms of Disease When a person swallows trichinella larvae encased in a cyst, the digestive juices dissolve the cyst, releasing the parasite into the body. The larvae then penetrate the intestine, where they mature into adult worms and mate. At this stage, symptoms include diarrhea, abdominal cramps, and malaise. Later the adult female worms produce larvae that penetrate the intestinal wall, enter the bloodstream, and burrow into muscle or other tissue. This causes high fever, muscle pain and tenderness, swelling of the eyelids or face, weakness, headache, and sensitivity to light. Diagnosis of Disease Initial diagnosis relies on physical examination of the classic signs and symptoms, blood samples, and a muscle biopsy. Transmission of Disease People get trichinosis when they eat undercooked meat — such as pork, bear, walrus, or horse — that is infected with the immature form (larvae) of the trichinella roundworm. Treatment of Disease Administration of anti-parasite (anti-helminthic) medication Tapeworm Type of Infectious Agent Helminth Name of Infectious Agent Tapeworm Symptoms of Disease Intestinal infections cause nausea, weakness, loss of appetite, abdominal pain, diarrhea, weight loss and inadequate absorption of nutrients from food. Invasive infections result in fever, cystic masses or lumps, allergic reactions to the larvae, bacterial infections, and neurological symptoms including seizures. Diagnosis of Disease Stool sample analysis, blood test, and/or imaging exam. Transmission of Disease Consumption of food or water contaminated with feces from a person or animal with tapeworm or ingestion of larvae cysts in meat or muscle tissue of an animal with a tapeworm infection. Treatment of Disease Administration of oral medications that are toxic to the adult tapeworm (including praziquantel, albendazole, and nitazoxanide). Common Cold Type of Infectious Agent Virus Name of Infectious Agent Rhinovirus Symptoms of Disease Symptoms include: runny or stuffy nose, itchy or sore throat, cough, congestion, slight body aches or a mild headache, sneezing, watery eyes, a low-grade fever, and mild fatigue. Diagnosis of Disease Physical examination. Transmission of Disease The virus enters your body through your mouth or nose. The virus can spread through droplets in the air when someone who is sick coughs, sneezes, or talks. But it also spreads by hand-to-hand contact with someone who has a cold or by using shared objects, such as utensils, towels, toys, or telephones. If you touch your eyes, nose, or mouth after such contact or exposure, you're likely to "catch" a cold. Treatment of Disease There is no cure for the common cold. Over-the-counter cold treatments do not treat the cold but can sometimes relieve symptoms. These include pain relievers, decongestants, and cough syrups. Flu Type of Infectious Agent Virus Name of Infectious Agent Influenza Symptoms of Disease Symptoms include fever, aching muscles (especially in the back, arms, and legs), chills and sweats, headache, dry cough, fatigue and weakness, and nasal congestion. Diagnosis of Disease Physical examination Transmission of Disease Flu viruses travel through the air in droplets when someone with the infection coughs, sneezes, or talks. You can inhale the droplets directly, or you can pick up the germs from an object — such as a telephone or computer keyboard — and then transfer them to your eyes, nose, or mouth. Treatment of Disease Bed rest and hydration is usually the only treatment needed. Antiviral medications can be prescribed if taken soon after symptoms begin. These drugs may shorten the illness by a day or so and help prevent serious complications. Rotavirus Type of Infectious Agent Virus Name of Infectious Agent Rotavirus Symptoms of Disease Symptoms begin with a fever, followed by three to eight days of watery diarrhea and vomiting. The infection can cause abdominal pain as well. In adults who are otherwise healthy, a rotavirus infection may cause only mild signs and symptoms — or none at all. Diagnosis of Disease Diagnosed via a physical exam. Stool sample may be analyzed to confirm the diagnosis. Transmission of Disease Rotavirus is present in an infected person's stool several days before symptoms appear and for up to 10 days after symptoms subside. The virus spreads easily through hand-to-mouth contact throughout this time — even if the infected person doesn't have symptoms. Not washing your hands after using the toilet or changing a child's diaper can cause the virus to spread to anything you touch, including food, toys, and utensils. If another person touches your unwashed hands or a contaminated object and then touches his or her mouth, an infection may follow. Sometimes rotavirus spreads through contaminated water or infected respiratory droplets coughed or sneezed into the air. Treatment of Disease There is no treatment for a rotavirus infection. The infection usually resolves within three to eight days. Primary treatment involves the prevention of dehydration. Histoplasmosis Type of Infectious Agent Fungus Name of Infectious Agent Histoplasma capsulatum Symptoms of Disease Several types of histoplasmosis exist. The mildest form produces no signs or symptoms, but severe infections can be life-threatening. Symptoms of the infection include fever, chills, headache, muscle aches, dry cough, and chest discomfort. Sometimes the infection causes joint pain and a rash. Diagnosis of Disease Inspection of lung secretions, blood or urine, biopsied lung tissue, and/or bone marrow. Transmission of Disease Histoplasmosis is caused by the reproductive cells (spores) of the fungus. The histoplasmosis fungus thrives in damp soil that's rich in organic material, especially the droppings from birds and bats The spores are extremely light and float into the air when dirt or other contaminated material is disturbed, so infection is most commonly transmitted during cleanup or demolition projects and to farmers and landscapers. Treatment of Disease Treatment usually isn't necessary if you have a mild case of histoplasmosis. But if your symptoms are severe or if you have the chronic or disseminated forms of the disease, you'll likely need treatment with one or more antifungal drugs. Ringworm (Tinea corporis) Type of Infectious Agent Fungus Name of Infectious Agent Dermatophytes Symptoms of Disease A circular rash on the skin that's red and inflamed around the edge and healthy looking in the middle; slightly raised expanding rings of red, scaly skin on the trunk or face; and/or a round, flat patch of itchy skin. Diagnosis of Disease Skin scrapings or samples from the infected area are taken and looked at under a microscope. Transmission of Disease Ringworm is contagious and can be spread in the following ways: direct, skin-to-skin contact with an infected person; touching an animal with ringworm; contact with objects or surfaces that an infected person or animal has recently touched or rubbed against; or contact with infected soil. Treatment of Disease Administration of a prescription-strength topical antifungal or oral medication. Athlete's Foot (Tinea pedis) Type of Infectious Agent Fungus Name of Infectious Agent Dermatophytes Symptoms of Disease Symptoms include itching, stinging, and burning between the toes; itching, stinging, and burning on the soles of the feet; itchy blisters; cracking and peeling skin, especially between the toes and on the soles of the feet; excessive dryness of the skin on the bottoms or sides of the feet; and/or toenails that are thick, crumbly, ragged, discolored, or pulling away from the nail bed. Diagnosis of Disease Skin scrapings or samples from the infected area are taken and viewed under a microscope. Transmission of Disease Athlete's foot thrives in thick, tight shoes that squeeze the toes together and create warm, moist areas between them. Damp socks and shoes and warm, humid conditions also favor the organisms' growth. The fungus is transmitted by sharing clothes or shoes with someone who has the fungal infection or walking barefoot in public areas where the infection can spread. Treatment of Disease Administration of antifungal medication.

Biochemical Tests

Biochemical tests are the most definitive way to identify bacterial species. Each biochemical test helps determine a property or characteristic specific to a certainbacterial species. These tests determine which growth media the bacteria will grow on and identify the end products of their metabolic processes, such as the wastes they excrete. For example, in one biochemical test, the bacterial sample is inoculated in a growth media containing a specific nutrient that only certain bacterial samples are able to metabolize, or break down. The media also contains an indicator. If the bacterial sample metabolizes the nutrient, it excretes acid as a waste product, causing the indicator to change color, indicating a positive result. Many tests often need to be performed in order to positively identify a bacterium. Laboratories have developed shortcuts that allow scientists to perform several biochemical tests at one time. Below is a description of each of the biochemical tests performed on Anna's bacterial sample.