Microbiology Questions: Bacteriology
Terms in this set (81)
In some people, untreated pharyngitis infections with Group A beta-hemolytic streptococci can eventually result in:
A sheep blood agar plate inoculated with a throat swab shows alpha hemolysis after incubation. What test can be done to determine whether the organism is viridans streptococci, part of the normal throat flora, or Streptococcus pneumoniae?
Bile solubility; S. pneumoniae colonies would be dissolved by the reagent and inhibited by optochin disk
Which of the following tests can be done to identify the presence of most Group A beta hemolytic streptococci from non Group A?
-PYR test; most Group A beta hemolytic streptococci colonies would produce a bright red color after addition of the PYR reagent
A gram stained sputum smear shows 40 to 50 squamous epithelial cells per low power field (10x) along with gram positive cocci, many gram negative rods, and many gram positive cocci in pairs using the oil immersion objective. How should you report the results for this smear?
-No report; request another specimen because this one is contaminated with mouth flora as evidenced by many squamous epithelial cells
Which test can be used to differentiate between a coagulase negative staphylococcus species and a micrococcus species?
A patient complains of a very sore throat and the throat swab submitted for routine culture grows diphtheroids; alpha, beta, and non hemolytic streptococci; staphylococci; Neisseria. The next step is to....
-Identify the beta hemolytic streptococcus species
A nasopharyngeal culture grows beta hemolytic colonies on sheep blood agar at 18 hours. The isolate is susceptible to a 0.04 unit of bacitracin. This can be identified as beta hemolytic streptococcus- which group?
Neisseria species can be identified and differentiated by...
The specimen of choice for the isolation of Bordetella pertussis from a suspected case of whooping cough is...
A mucoid, lactose positive colony on MAC agar that is indole negative, citrate positive, and non motile is...
A patient with third degree burns has a would culture that grows a gram negative rod and the colonies produce a bluish green pigment and have a fruity odor. Other characteristics include: oxidase positive, motility positive, and triple sugar iron results of K/K. The most probably genus of this isolate is...
Clue cells seen in malodorous vaginal discharge are associated with a diagnosis of bacterial vaginosis. A vaginal culture will grow what organism?
What are the apppropriate set of quality control microorganisms for the following tests that will give positive and negative reactions for each of these tests: Bile esculin hydrolysis; a. Bacitracin susceptibility; 6.5% NaCl tolerance; Hippurate hydrolysis
-S. pyogenes, Streptococcus agalactiae, enterococci
What is unique to Pseudomonas aeruginosa?
-Production of pyocyanin
Repeated negative sputum cultures are reported from an elderly patient who smokes, has pneumonia with persistent cough and high fever, and does not respond to routine antimicrobial therapy. The most recent Gram stain of sputum shows 3+ PMNs, mucous present, and rare epithelial cells. A likely etiological agent is....
A sputum culture yields predominantly alpha hemolytic, flat colonies on sheep blood agar and on Gram's stain reveal gram positive cocci in pairs. Which biochemical tests will help with the identification?
-Optochin susceptibility of bile solubility
Gram positive cocci in pairs and clusters are isolated from a superficial skin lesion. The isolate is beta hemolytic on sheep blood agar and catalase and coagulase positive. The definitive identification of this organism is...
A transtracheal aspirate yields a pure culture of an alpha hemolytic, gram positive coccus that is catalase negative. The next test to perform to identify this isolate is...
-Susceptibility to optochin
A gram negative diplococci that is a normal inhabitant of the human nasopharynx, but is known to cause serious systemic illness in children and young adults is...
Most members of the genus Pseudomonas are gram negative rods that are...
-Oxidase positive and motile
Rheumatic fever and glomerulonephritis are diseases commonly associated with which organism?
Which pair of organisms does the optochin susceptibility test differentiate?
-Viridans streptococci/Streptococcus pneumonia
Staphylococcus aureus causes a wide variety of infections, ranging from wound to pneumonia. Treatment with penicillin has not been effective because of the...
-Production of beta lactamase by S. aureus
Exudates from a patient with acute epiglottitis shows gram negative, non motile pleomorphic coccibacilli on direct smear. No growth is found on MAC or BAP. Semi opaque colonies appear on chocolate agar enhanced by CO2 and grows only around the strip that contains both X and V factors. This organism is...
Microbiology laboratory acquired infections from an aerosol are associated with...
-Improper venting of air in the laboratory setting
Prevention of aerosolization can be best accomplished by...
-Using a biological safety cabinet when working with specimens or when forming aerosols
Media that contain dyes, antibiotics, or other chemical compounds that inhibit certain bacteria while allowing others to grow are called:
Media that contain factors (e.g. carbohydrates) that give colonies of particular organism's distinctive characteristics are called...
Media that are used to permit the normal rate of growth of most nonfastidious organisms are called...
Which of the following media is used to promote the growth of gram negative organisms while inhibiting the growth of gram positive?
Which media is used to promote the growth of Neisseria species?
The lowest concentration of antimicrobial agent that will visibly inhibit the growth of the organism being tested is known as the...
-Minimum inhibitory concentration
Which of the following organisms can be recognized by its spreading growth appearance on sheep blood agar?
Urogenital swabs to be cultures for gonococci should be plated...
In culturing a throat swab for group A hemolytic streptococci, which of the following media is preferred?
-Sheep blood agar
Clue cells are best seen (When observed in the doctor's office) in which of the following specimens?
-Wet prep of vaginal discharge
If the antibiotic does not inhibit the growth of an organism, the organism is...
Isolation of Campylobacter jejuni from a patient with gastroenteritis is optimized by...
-A microaerophilic environment
If acetone-alcohol is omitted from the gram stain procedure, streptococci and Neisseria will be stained, respectively....
-Purple and purple
On thiosulfate citrate bile salts sucrose (TCBS) agar, colonies of Vibrio cholerae appear...
Organisms that grow best with greater carbon dioxide concentrations than are found in ambient air are called...
A stool specimen from a five year old patient with bloody diarrhea is received. Which of the following media would be used to detect E. coli O157:H7?
A child presents with a typical paroxysmal "whoop-type cough" and lymphocytosis. The appropriate primary culture medium to isolate the suspected etiologic agent is...
Which of the following specimens should not be routinely processed for anaerobic culture?
-Clean, voided urine
Chocolate agar is usually used as primary planting medium for...
Several vacationers at a Gulf Coast seaside resort complain of severe abdominal pain and diarrhea after eating raw oysters. The media most appropriate for screening these patient's stools is...
-Thiosulfate citrate bile salts sucrose
Stool cultures from children with a day care outbreak of diarrhea revealed an oxidase negative, non-lactose fermenting, non-motile, gram negative rod. These characteristics presumptively indicate...
Organisms that grow in the presence or absence of oxygen are called...
A small gram positive rod that causes neonatal meningitis and septicemia is...
The X and V factors required for growth of Haemophilus influenzae are found in...
On sheep blood agar, Haemophilus influenzae satellites around colonies of...
What does the family of Enterobacteriaceae do with glucose?
Escherichia, Klebsiella, and Proteus species are common flora of the...
The beta-lactamase test that directly determines beta-lactamase production by a microorganism is based on detection of a (an)....
-Increased acidity due to the release of penicilloic acid
A gram negative coccobacilliary organsim that is isolated from synovial fluid on chocolate agar resemble either Morazella species or neisseria gonorrhoeae. The single best test to distinguish between these two organisms is...
The most sensitive method for the detection of beta-lactamase in bacteria is by the use of...
Cerebrospinal fluid should be cultured immediately, but if delayed the specimen should be...
-Refrigerated at 4-6 degrees C
A beta hemolytic, gram positive rod was isolated from CSF of a baby with signs of meningitis. The isolate grew on sheep blood agar and demonstrated tumbling motility. The presumptive identity of the isolate is...
What quantitative urine culture results would be considered clinically significant for a UTI in an asymptomatic patient?
-10^5 CFU/mL Urine
MacConkey agar is quantitatively inoculated with a urine specimen. Results are 10^5 CFU/mL urine of gram negative, lactose fermenting organisms. Which of the following would be the most likely organism to cause this infection?
A urine is received in the lab for culture. If the specimen cannot be plated immediately, it should be held...
-In the refrigerator
Which of the following is a common cause of UTI among sexually active women?
A urine sample that reveals gram positive cocci and gram negative rods is inoculated on a sheep blood agar, MacConkey agar, and Columbia NCA agar. The CNA is included because it...
-Contains colistin and nalidixic acid as inhibitory agents
An isolate from a UTI grows as porcelain white, butyrous colony that is nonhemolytic on sheep blood agar. The isolate is gram positive coccus, catalase positive, tube coagulase negative, modified oxidase negative, novobiocin sensitivity- resistant, and Mannitol= acid. This isolate is best identified as...
A catalase negative nonhemolytic gram positive coccus isolated from a urine specimen from a 42 year old woman hydrolyzes bile esculin and grows in the presence of 6.5% NaCl. This isolate is most likely...
The following results are obtained from a nonlactase-fermenting, gram negative rod isolated from a UTI: TSI= K/A; H2S= negative; Indole, Motility, Urease, Ornithine, Phenylalanine deaminase are all postiive; Citrate= negative. This organism is...
Urine cultured from the cathater of an 18 year old female patient grew greater than 10^5 CFU/mL urine on a CAN plate. Colonies were catalase positive, slide and tube coagulase negative. The best single test for identification is...
Which of the following tests will rapidly differentiate micrococci from staphylococci?
Which of the following primary media combinations is appropriate for initial subculture of blood cultures?
-Sheep bloccd, MacConkey, chocolate, and anaerobic blood agar
Which of the following organisms most commonly cause endocarditis?
Blood culture instrument systems indicates bacterial growth by monitoring a (an)...
-Increase in carbon dioxide
Blood culture instrument systems may interpret a true negative culture as a false positive due to...
-Increased WBC count
Which of the following specimens is acceptable for the evaluation of clinically important anaerobes?
An anaerobic gram positive spore forming rod is isolated from an intra-abdominal abscess following boewl surgery. This organism produces colonies on anaerobic blood agar that show a doulbe zone of hemolysis and is most likely:
Obligate anaerobes, facultative anaerobes, and microaerophiles are terms referring to bacteria requiring...
Which of the following is the medium of choice for the selective recovery of gram negative anaerobes?
-Kanamycin-vancomycin (KV) agar
Which spore type and location is found on Clostridium tetani?
-Round, terminal spores
Obligate anaerobic gram negative bacilli that do not form spores grow well in 20% bile and are resistant to penicillin are most likely...
Which gram negative bacilli produce black pigment and brick red fluorescence when exposed to an ultraviolet light source?
-Porphyromonas species and Prevotella species
The gram positive non-spore forming anaerobic rods most frequently recovered from blood cultures as a contaminant are...
Anaerobic bacteria are routinely isolated from these infections...
-Lung abscesses, brain abscesses, dental infections
-Not from UTIs
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