MICROBIOLO NU440/NUR4-Medical Microbiology Notes

MICROBIOLO NU440/NUR4-Medical Microbiology Notes Medical Microbiology Notes The field of study in which medicine and microbiology intersect is known as medical microbiology. Which of the following is a characteristic of members of the resident microbiota? Resident microbiota can compete with and limit growth of harmful bacteria. Which body sites normally have large numbers of resident microbiota? Vagina, skin, throat, large intestine, nose. Which of the following may provide opportunities for members of the resident microbiota to cause disease? A break in the skin or mucous membrane barriers, antibiotic usage which changes the balance of normal microbiota, poorly functioning immune system. Which of the following are genera of gram-positive cocci frequently found as resident microbiota in humans? Enterococcus, streptococcus, staphylococcus Which of the following infections are frequently caused by Staphylococcus species as well as Streptococcus species? Pneumonia, endocarditis, abscess, urinary tract infection. In which body sites are gram positive cocci predominant members of the resident microbiota? Nose, skin, mouth and throat Impetigo, a type of inflammatory skin infection, is caused by staphylococcus aureus and streptococcus pyogenes. Before attempting to identify an unknown bacterial species, the organism must be isolated in a pure culture. Quickest way to isolate bacteria from a mixed culture? Streak Plating A specific example of a medium that can be used to isolate organisms from the human body because it is enriched with compounds that support the growth of fastidious organisms is blood agar. Which of the following is an example of a morphological characteristic that could be used in the bacterial identification process? Cell shape Gram positive cocci in chains = Streptococcus Gram positive cocci in clusters = Staphylococcus Gram positive cocci in pairs = Diplococcus Identification of a bacterial species cannot be made on a microscopic morphology alone because many microorganisms have a similar microscopic morphology. The most reliable source of information regarding the tests that can be used to identify a particular bacterial isolate and the expected results is Bergey’s Manual. When choosing a biochemical test to run on an unknown, you should consider which of the following? Choose an easy, rapid test that is standard for its main group of bacteria. A dichotomous key is a flowchart that can be used to identify an organism by making a series of choices until you arrive at one possibility. What test is most useful for distinguishing between streptococcus pyogenes and streptococcus pneumoniae? Hemolysis on blood agar. Which of the following types of media might be particularly helpful in the isolation of a bacterial species from a mixed bacterial culture? Selective, differential What type of medium is enriched with a complex organic substance, allowing for the growth of fastidious organisms from the human body? Blood agar. The Gram stain is an example of a test that can be used to determine the morphological characteristics of a bacterium. What correctly describes the streptococci? Purple after gram stain, cells arranged in chains, spherical cells How do you determine the species of an unknown bacterium? You use standard tests and pre-existing knowledge to classify the bacterium. FALSE: The Same tests are used on streptococci and staphylococci to determine the exact species identity of an unknown gram-positive coccus. Circle around it = sensitive No circle = resistant Triangle = Camp positive No triangle = Camp negative Square looking = gamma U looking = beta Which biochemical tests involve streaking bacteria onto a plate, applying a small disc, and after incubation, examining for a zone of inhibited growth? Novobiocin sensitivity, optochin sensitivity, bacitracin sensitivity. Which biochemical test requires rabbit plasma as a reagent and its results are determined by observation of thickening of the medium? Coagulate test Which biochemical tests are used fot the identification of species within the staphylococcus genus? Mannitol fermentation, coagulate test, novobiocin susceptibility, catalase test Staphylococcus aureus = coagulase positive Streptococcus pyogenes = beta hemolytic, bacitracin sensitive Streptococcus pneumoniae = alpha-hemolytic, optochin sensitive Staphylococcus saprophyticus = novobiocin resistant Enterococcus faecalis = bile esculin hydrolysis positive Streptococcus agalactiae = beta-hemolytic, CAMP test positive What test does not require an incubator? Catalase test What is true about staphylococcos saprophyticus? Possesses catalase enzyme, does not possess coagulase enzyme, may not ferment mannitol What color is staphylococcos saprophyticus after incubation? Pink Culture = uses several different types of media to grow bacteria from patient specimens Identification = uses a variety of tests and media to determine the genus and species of a bacterial isolate. Sensitivity = tests a microorganism with a battery of different antibiotics to determine which antibiotics are most likely to control or eliminate the infection. Staphylococcus saprophyticus = urinary tract infection in young women Streptococcus pyogenes = scarlet fever; strep throat Streptococcus agalactiae = sepsis and meningitis in newborn babies Streptococcus pneumoniae = conjunctivitis; meningitis in young children What describes Streptococcus agaliacticae (Group B strep)? Beta-hemolytic, no zone around bacitracin disk appears in test on blood agar, synergistic hemolysis with S. aureus on blood agar (CAMP test). Streptococcus agalactiae would appear purple in color and spherical shaped under a microscopic examination. Which of the following reasons for identifying bacteria isolated from infections? Identification may help with antibiotic selection, identification may help with epidemiologic investigations, identification may help with disease diagnosis. Close observation of the growth on agar revealed that the colonies were beta-hemolytic. Based on this observation alone, which two organisms are most likely agents? Streptococcus pyogenes, staphylococcus aureus The catalase test was negative. What two tests might be done next? Bacitracin susceptibility, CAMP test Which test will enable you to determine if these colonies are staphylococci or streptococci? Catalase test What is true about staphylococcus saprophyticus? May not ferment mannitol, possesses catalase enzyme, does not possess coagulase enzyme Staphylococcus saprophyticus looks purple spherical bacteria in clusters under the microscope. The blood culture bottles were sub cultured onto blood agar plates and 24 hours later, a number of colonies exhibiting alpha hemolysis were observed. A catalase test gave a negative result. Based on this information