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EXAM 4: 15-18
MLT 124:MEDICAL MICRO PT 1
| Question | Answer |
|---|---|
| What are the general characteristics of oxidase positive glucose non-fermenting GNR? | -aerobic - grow on MAC (NLF) - motile (except B. mallei) - oxidase pos |
| What P. aeruginosa virulent factor inhibits protein synthesis | Exotoxin A |
| In P. aeruginosa, (blank) destroys cells and tissues of the host, which is why it often causes infection in burn patients, contact lens issues, and swimmer's ear | proteolytic enzymes and hemolysins |
| True or false: P. aeruginosa contain pili for host attachment and alginate to encourage phagocytosis | false; alginate inhibits phagocytosis due to its capsule-like capabilities |
| P. aeruginosa is an (overt /opportunistic) pathogen | opportunistic |
| Swimmer's ear is often caused by (blank), which infiltrates cracked skin of the ear canal? It is a green NLF, Beta hemolytic with metallic sheen, and has a grapelike smell | Pseudomonas aeruginosa |
| Why is P. aeruginosa particularly dangerous for Cystic Fibrosis patients? | CF is a genetic mutation that causes overproduction of mucus. P. aeruginosa's alginate virulence factor has sticky adhesions that can cause systemic issues |
| Which nosocomial infections are P. aeruginosa responsible for? | Ecthyma gangrenosum (blood vessel destruction- black papules) ear canal infection that can progress into nerve and skull bone damage (diabetics) |
| What does Pseudomonas aeruginosa look like on MAC | NLF with green color |
| What does Pseudomonas aeruginosa look like on BAP | beta hemolytic with metallic sheen |
| What biochemical tests can confirm P. aeruginosa presence, following BAP and MAC results? | oxidase pos, K/K on TSI slant, grows at 42 degrees Celsius, nitrate pos w/gas production |
| What can P. aeruginosa look like on MAC plate, for Cystic Fibrosis patients | mucoid |
| Which species of Burkholderia is considered a bioterrorism agent? What makes it so dangerous? | B. pseudomallei; it can survive phagocytosis, causing melioidosis (septic shock, skin abscesses) |
| This bacteria is known as a death nell for Cystic Fibrosis patients? It is oxidase pos, glucose neg, and LDS pos. What causes this? | B. cepacia; exposure to medical devices |
| What agar is used to promote the growth of Burkholderia cepacia | BCSA |
| Which nosocomial skin/respiratory colonizer are oxidase negative, glucose non-fermenter? | Acinetobacter and Stenotrophomonas maltophilia |
| What is the colonial morphology of Stenotrophomonas maltophilia? | NLF on MAC, smooth colonies on BAP (can be purple with green underneath), distinct ammonia smell |
| Which bacteria is known for being a maltose oxidizer? | S. maltophilia |
| How we differentiate species of the Acinetobacter spp? | glucose oxidizer ( A. baumanii ) or non-utilizer of glucose ( A. lwofiii ) |
| Which GNR is found in brackish water? What is its main source of transmission | Vibrio cholera; oyster |
| Which GNR is found in fresh water? | Aeromonas hydrophilia |
| What causes the "rice water stool" symptom of V. cholera | cholera toxin that hyper-secretes electrolytes into the GI tract |
| What virulence factor in V. cholera is responsible for penetrating the mucous layer of the GI tract? | Mucinase |
| True or False: Vibrio cholera is non-motile with pili | false; motile with pili |
| What does Aeromonas hydrophilia often cause in infected patients? | cellulitus, gastroenteritis |
| Describe the cellular morphology of V. cholera | GNR curved, greenish hue on BAP, NLF on MAC, |
| What is the cellular morphology of Acinetobacter spp | NLF on MAC, but can have a purple hue |
| True or False: Vibrio cholerae requires salt to survive, which is why the Vibrio String test lyses Vibrio cells, producing DNA upon string contact | true |
| What results does Vibrio Cholera yield to identify it? | oxidase pos, growth in 0.5% salt, string test pos, TCBS growth (yellow), 6% salt growth - variable |
| What results does Aeromonas spp. yield to identify it? | oxidase pos, 0.5% salt growth, no growth on 6% salt, string test neg, TCBS no growth |
| What media is used to cultivate Vibrio cholerae? What does it differentiate? | TCBS; sucrose fermentation |
| Why can a microscan not be used on Vibrio cholerae? | it requires salt to survive |
| What are the common characteristics of Campylobacter jejuni and Helicobacter pylori? | curved GNR, highly motile, microaerophilic (more CO2, less O2), fastidious organisms |
| Which seagull-shaped organism is known for causing gastroenteritis and septicemia from food contamination (especially chicken)? | Campylobacter jejuni |
| What media is used to transport C. jejuni? | Cary-Blair or Campy Thioglycollate |
| What is the purpose of Skirrow's media and Campy BAP used for? What are the growing requirements? | they have antibiotics to suppress normal flora; all of them are charcoal based and can only grow at 42 degrees C in microaerophilic environment for 48hrs |
| How do we identify Campylobacter spp? | found in routine stool culture, darting motility, oxidase pos, catalase pos, mucoid gray colonies |
| Which curved GNR is known for causing peptic stomach ulcers, and even gastric center? | Helicobacter pylori |
| Describe the effect of urease on in H. pylori cases | it makes an alkaline environment in the stomach, allowing for the bacteria to colonize it and causing peptic ulcers |
| What is the most common specimen for H. pylori that gets transported using Stuart's media to prevent it from drying? | tissue biopsy |
| How can we identify Helicobacter? | oxidase pos, catalase pos, urease pos (pink), no growth at 42 degrees C, pos breath urea testing, growth on Campy-CVA |
| What are the common characteristics of the Brucella spp. | small coccobacilli, non-motile, capnophilic |
| Describe how Brucella spp. can be transmitted | consumption, inhalation, or direct contact with cattle, sheep, swine, or dogs, and the Brucella organisms get ingested but do not die in the liver and spleen |
| How do we cultivate Brucella spp. | 3 weeks of heated blood incubation (instead of 5 days), that begin to become small convex, smooth translucent colonies within 48hrs |
| How do we identify Brucella spp. | catalase pos, oxidase pos, non-motile, urease neg, nitrate pos, capnophilic |
| Which biochemical tests separates H. pylori and C. jejuni | urease; H. pylori=pos, C. jejuni=neg |
| What are the general characteristics of Pasteurella multocida | small GNR, non motile, oxidase pos, glucose fermenter, no growht on MAC |
| Describe how Pasteurella is acquired and what infection it causes | cat/dog bite that produces an endotoxin and capsule, causing soft tissue infection, chronic respiratory infection, or bacteremia |
| How do we cultivate and identify Pasteurella multocida | grow on BAP/SBA (gamma hemolytic), and CHOC in capnophilic environment, smooth gray colonies; catalase pos, indole pos, urease neg, mannitol/sucrose fermenter, nitrate reducer |
| Pasteurella spp. can grow on BAP and CHOC agar, while Haemophilus spp. (blank) | only grows on CHOC (no BAP/MAC growth) |
| True or False: Haemophilus require heat stable Factor X and heat liable Factor V to grow | true |
| Which bacteria is known to be the most common cause of bacterial meningitis in children? | Haemophilus influenzae |
| Which typeable H. influenzae contains a capsule, and is the most common strain that causes serious effects such as bacteremia, osteomyelitis, pneumonia, and epiglottis? | H. influenzae b (Hib) |
| Which kind of H. influenzae causes conjunctivitis and other localized infections | non-typeable |
| Describe H. ducreyi (transmission, adverse effects during infection) | genital pathogen that is transmitted by an ulcer-like lesion called a chancroid |
| Which bacteria is known for having a "school of fish" morphology | H. ducreyi |
| Describe the Satelliting test | a LAWN streak is made with Haemophilus spp. on a BAP, and a streak of S. aureus is brought across in a line. S. aureus contains NAD, which Haemophilus spp. is able to grow around the Staph colonies because of V Factor production |
| H. ducreyi grows on | Mueller-Hinton agar to inhibit Gram pos growth |
| How can we identify Haemophilus spp. | X and V factor growth, hemolysis on rabbit blood agar, satelliting with S. aureus |
| A blood culture from a child with sepsis was discovered. The lab results are as follows: Pos for V and X factor, Satellite on BAP positive. What organism is this? | H. influenzae (type b, likely) |
| Specimen from a patient with conjunctivitis was received by the lab. The results are as follows: pos X factor only, negative Satellite on BAP. What bacteria is this? | H. ducreyi |
| What is the principle of the Porphyrin test? | converts ALA to porphyrin, which determines the bacteria's need for X factor |
| What are the general characteristics of the HACEK group? | normal oropharyngeal flora that are fastidious capnophiles. they can cause endocarditis by forming abscesses |
| Describe Eikenella corrodens | oral flora that can corrode agar as it grows, has a chlorine bleach odor, and commonly causes cellulitis/clenched fist injuries. no growth on MAC |
| Which HACEK organism has "morse code" gram stianing | Actinobacillus |
| Which bacteria is known for causing sexually-transmitted gonorrhea? | Neisseria gonorrhoeae |
| Which species of Neisseria causes meningitis and sepsis? | Neisseria meninigitidis |
| How do we identify N. gonorrhoeae | intra- or extra-cellular diplococci. capnophilic, no BAP growth, but grows on Thayer-Martin/Martin-Lewis choc agar, gray opaque convex colonies that are oxidase positive and only ferment glucose |
| A college-aged patient comes in with petechial and pupric rashes along their skin and is complaining of neck stiffness. A CSF sample is taken to the lab. How can we prove that this is N. meningiditis? | small, tan colonies on BAP and Martin-Lewis plate. gram neg diplococci that is oxidase positive. followed up with carbohydrate fermentation that reveals glucose and maltose ferm. |
| A sputum sample is retrieved from an immunocompromised patient with otitis. It grew on BAP and CHOC, the later having creamy pink hue. What can we do to confirm it is Moraxella catarrhalis? | oxidase positive, non-sugar fermenter, positive DNase enzyme |
| A sputum sample is retrieved by the lab. The bacteria grew on neither MAC nor BAP. What follow-up testing can we do to confirm Haemophilus influenzae presence? | gram stain (GNR), oxidase (-), CHOC growth, Satelliting w/S. aureus (positive), Factor X and V testing proves clearing using XV together. |
| What pathogens are particularly dangerous for Cystic Fibrosis patients? | Burkholderia cepacia, P. aeruginosa, H. influenzae, S. aureus |
| What testing differentiates Stenotrophomonas maltophilia from P. aeruginosa | P. aeruginosa=oxidase pos, glucose fermenter only S. maltophilia=oxidase negative, glucose and maltose fermenter |
| Which specialty media is used to cultivate Vibrio cholera | TCBS |
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