Microbiology and Parasitology Questions and Answers

Microbiology and Parasitology Questions and Answers When was the term microbiology first used 1860s What four areas of study are encompassed by clinical microbiology Viruses, fungi, bacteria, and parasites What is the difference between a pathogen and an opportunistic pathogen Pathogen: a bacteria capable of causing a disease Opportunistic pathogen: microorganisms that invade the body and cause illness only when the body's immune defense are impaired or absent How do bacterial pathogens cause host damage The damage is caused by bacterial growth in tissues or y the toxins bacteria produce What are the morphological types of bacteria Coccus, bacillus, and spirochete What are the morphological forms of fungi Molds and yeast What is a gram stain? A test that uses a series of stains to differentiate the composition of their cell walls Gram positive- violet (retain the crystal violet stain) Gram negative- pink (lose the crystal violet and retain the safranin) What is the difference between aerobic and anaerobic bacteria Aerobic bacteria grow in the presence of oxygen Anaerobic bacteria grow in the absence or decreased levels of oxygen How are viruses different from microorganisms? Name 3 viral diseases Viruses are not living cells, and can only replicate by invading a cell, viruses can only contain either a DNA or RNA not both Epstein-Barr virus (mono), rubella, rhinoviruses What type of specimen is used to detect malaria and giardia Malaria requires blood specimen Giardia requires fecal specimen Five methods used to help identify bacteria microscopic morphology- coccus, bacillus, spirochete colony morphology- how the colony grows on the plate reactions with Gram stain and other stains, biochemical reactions, gene probes antibody reactions- antibiotic susceptibility testing antibiotic susceptibility testing can be routine like strep only works for bacteria finding the minimum inhibitory concentration (MIC) to inhibit the bacterial growth fastidious bacteria bacteria that require special nutritional factors to survive immunoassay a diagnostic method using antigen-antibody reactions Diagnostic Testing The standard method for isolating and identifying viruses have been cell culture. As well as serum testing for anti-viral antibodies using enzyme immunoassays. What can cause contamination of a throat swab during collection? Touching the tongue and inside of the mouth will contaminate the swab with normal flora What mistakes can occur in the collection of urine for culture? The patient can insufficiently cleanse the area around the urethral opening and contaminate the urine with skin microorganisms, epithelial cells and mucus Why stool specimens in an infants disposable diaper may not grow microorganisms because diapers often contain bacteriostatic chemicals inhibiting microorganisms from growing Why should the patient rinse their mouth with water before collecting sputum sample? to reduce the number of oral bacteria present that can contaminate the sputum sample why is an aspirate of a wound preferred over a swab? the swab is more prone to drying and in addition may not pick up sufficient bacteria for culture why are both alcohol and iodine used in preparation for a blood culutre if cleansing is not thorough, skin bacteria or fungi can contaminate the culture and produce false-positive results 3 important properties of transport systems for bacteriology specimens A container capable of providing the correct environment until the bacteria can be inoculated, the test requisition form and specimen label What type of culture performed to determine MRSA nasal swab specimen carrier an individual who harbors an organism and is capable of spreading the organism to others, but has no symptoms or signs of disease What are the 3 categories of transmission-based precautions? give an example of a condition or disease related to each precaution Contact- infections spread primarily by close or direct contact- MRSA Droplet- infections easily transmitted through short distances- pertussis Airborne- infections transmitted by long distances airborne route- varicella standard precaution vs transmission based precaution standards are always used, regardless of diagnosis, treating all blood and bodily fluids as if infectious transmission based precautions- used in addition to standard, provide additional protection of transmission based infections protective isolation isolation category to protect highly susceptible patients from exposure to infectious agents; reverse isolation nonsocomial infection healthcare-associated infection infection acquired while being treated for another condition in a healthcare setting fomite inanimate objects such as bed rails, linens or eating utensils which can be contaminated with infectious organisms and serve as a means of their transmission How are parasitic infections usually diagnosed? Finding and identifying the parasite either macroscopically or microscopically or by immunological tests. Have to look in the right place The 3 major groups of organisms that contain human parasites? Arthropods- insects, helminths- worms, and protozoa- single cell What body sites can be infected by parasites? External body surfaces, external body cavities, the intestinal tract, and tissues and organs such as blood, bone marrow, brain lung or liver. Factors that affect the severity of parasitic infections Parasite numbers, size, location, toxicity, host condition What are ways parasitic diseases can be transmitted? Through contact with an infected person, ingestion of an infective form, or through insect bites Methods used to prevent or control parasite infections Blocking transmission of the infective form, providing health education, improving sanitation, identifying and treating infected individuals, and developing vaccines Four groups of protozoan parasites Amebae, flagellates, ciliates, and sporozoan Three groups of parasitic helminths trematodes (flukes), cestodes (tapeworms), and nematodes (roundworms) How are intestinal parasitic infections usually diagnosed morphology by either cysts, trophozoites or oocyts in fecal specimens. Immunological test assays that have high sensitivity and detect low levels of antigen, levels that might require microscopic and macroscopic assay. Free living ameba lives in nature without a host, becomes toxic when invaded Four parasites that cause food borne or waterborne infections Giardia, enterobasis, trichinosis, cyclosporiasis, cryptosporidosis How are infections with blood or other tissue parasites usually diagnosed? Determined by the location of the infection Blood parasites are identified by microscopic examination on stained blood smears tissue parasites are identified by microscopic examinations of stained biopsy material Guinea worm disease? A parasitic worm that causes painful crippling. Expected to be the first eradicated without a vaccine due to education and preventative measures- contaminating drinking water, and finding clean filtered water Correct fecal collection method Samples should be collected in a clean, dry, wide-mouth, leakproof container. Sample must not be contaminated with urine, water, soap, or disinfectant Specimen container must be labeled correctly Which type of fecal specimen must be processed quickly watery or liquid specimens within 30 minutes because forms such as protozoan trophozoites deteriorate rapidly Terms used to describe the consistency of fecal specimens watery, loose, soft or formed Fecal specimen preservative requirements Must be formalin- and mercury free environmentally safe zinc and copper based PVA preservatives What parasite is best detected from a perianal swab Pinworm- the eggs How are commercially available sticky paddles used to collect perianal specimens The paddle device is used by gently spreading the buttocks apart and pressing the paddle swab several times around the anal opening between 9pm and midnight What specimens other than fecal specimens are examined for parasites? Sputum, vaginal secretions, tissue or biopsy, CSF or urine Why is timing of specimen collection and rapid processing of parasitic specimen important To ensure that the parasite morphology is maintained and increase the chances of finding motile forms