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80 Cards in this Set
- Front
- Back
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What biochemical test and result will differentiate between Staphylococcus aureus and S. epidermidis?
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coagulase test
S. aureus is + |
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What biochemical test and result will differentiate between Neisseria meningitidis and S. aureus?
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oxidase test
Neisseria is + |
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What biochemical test and result will differentiate between Enterococcus and viridans Strep?
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NaCl tolerance, Bile Esculin
Enterococcus is + for both Strep too wussy |
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What biochemical test and result will differentiate between Group A strep and Group B strep?
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Bacitracin susceptibility
Grp A is sensitive, Grp B resistant |
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What biochemical test and result will differentiate between Corynebacterium diphtheriae and C. pseudodiphtheriae?
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Urea test
C. pseudodiphtheriae is + for urease --> alkaline pH --> fuschia color |
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What biochemical test and result will differentiate between Neisseria meningitidis and N. gonorrhoeae?
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Sugar oxidation
N. meningitidis ferments glucose, maltose (MC does M) N. gonorrhoeae ferments glucose only (GC does G) |
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What biochemical test and result will differentiate between N. gonorrhoeae and Moraxella spp.?
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growth on CTA slants unlike GC and MC
does NOT oxidize glucose |
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What biochemical test and result will differentiate between Listera and Corynebacterium spp?
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motility: Listeria is +, motile
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What biochemical test and result will differentiate between Haemophilus influenzae and H. parainfluenzae?
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X and V factor tests
HP req V only HI needs X and V |
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What biochemical test and result will differentiate between Strep pneumoniae and viridans strep?
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optochin and bile solubility
S. pneumo is +, + optochin sensitive and bile soluble |
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What are X and V factors?
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X = hemin
V = NAD |
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What are the only oxidase + organisms we've discussed so far?
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Pseudomonas
Neisseria Moraxella Campylobacter |
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What specimens would you find Moraxella in?
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sputum, sinus biopsies, middle ear specimens
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What diseases are caused by Listeria spp?
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foodborne meningitis
ingest large # of cells --> get into CSF via M cells in the gut |
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Which diseases are caused by encapsulated Haemophilus spp?
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INVASIVE DISEASE
no antibodies to capsule meningitis, pneumonia, epiglottitis also septic arthritis, pericarditis |
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Which diseases are caused by UNencapsulated Haemophilus spp?
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NONINVASIVE DISEASE--isolated to upper resp tract
ear infections, pink eye, sinusitis, acute bronchitis |
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How is Haemophilus transmitted from person to person?
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inhalation of respiratory droplets/aerosols
--> colonization of nasopharynx; many infections start in respiratory tract. |
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What disease is caused by Haemophilus ducreyi?
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chancroid, an STD that causes shallow genital ulcerations.
lots of fun. |
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Meningitis caused by _____ in the young and ______ in older populations.
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Streptococcus agalactiae (neonates),
Haemophilus influenzae (young) Neisseria meningitidis, Listeria monocytogenes, Streptococcus pneumoniae |
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Why is it easy to mix up Listeria with Streptococcus species?
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-beta-hemolytic and Sodium Hippurate positive (looks like Strep agalactiae/GBS)
-Bile Esculin positive and NaCl tolerant (Enterococcus) |
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Why is a red color after the addition of zinc dust to a Nitrate reduction test considered a negative result?
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red indicates the presence of nitrate and thus no nitrate reduction.
reagents A and B react to form a red color with nitrITE; Zinc dust will react to form a red color with any remaining nitrATE. clear after A and B and Zn dust means NO3 --> NO2 --> other Nitrogen spp. |
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What is Loeffler's slant particularly useful for when growing Corynebacterium spp.?
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visualizing volutin granules in C. diphtheriae.
C. diphth also grows like a weed on Loeffler's for some reason. |
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How do diphtheria's effects spread around the body?
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lysogenic phage-encoded exotoxin, not the bacterium, spreads around the body. bacterium itself remains isolated to upper respiratory tract.
exotoxin inhibits protein synthesis --> cell death |
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Which organism is identified using blood tellurite agar?
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Corynebacterium spp.
reduces tellurite --> tellurium for jet black colonies |
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Which organism do we isolate using VCN agar?
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GC aka gonococcus aka
Neisseria gonorrhoeae Vancomycin inhibits gm +, Colistin inhibits gm -, Nystatin inhibits fungi |
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How do we differentiate between Group A and Group B streptococci?
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-Sodium Hippurate test: Group B is +
-Bacitracin susceptibility: Group B is resistant |
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What makes our MacConkey "permissive?"
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lack of Crystal Violet
lets certain GPC grow |
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What makes (non-permissive) MacConkey selective? What does it select for?
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selects for intestinal GNR
Crystal Violet and other dyes inhibit gm+ Bile salts inhibit non-intestinal flora. |
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What is approximate ID50 of Shigella?
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10-100 organisms!!
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What is the purpose of an acid fast stain?
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Acid alcohol drives stain into waxy cell walls of Mycobacterium spp. et al
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What stain is used in acid-fast stain to target acid-fast structures?
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Kinyoun Carbol-Fuschin. Very strong! Red color.
Counterstain w/methylene blue. |
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From what clinical specimen would the presence of Staphylococcus saprophyticus be significant?
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urine specimen
S. saprophyticus is a common cause of UTI's in young women. |
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What organism is the leading cause of sepsis, meningitis, and pneumonia in newborns?
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Group B Strep
S. agalactiae often transmitted during vaginal births if mom is carrier (GBS sometimes normal microbiota) |
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What is one of the only times we are concerned with identifying a coagluase negative Staphylococcus species?
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in UTI specimens--rule out Staph saprophyticus, a common cause of UTI's.
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Spp. found in CSF?
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N. meningitidis
L. monocytogenes Group B strep (neonates) Haemophilus (infants) |
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Spp. found in sputum?
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Strep pneumoniae
Haemophilus influenzae S. aureus Pseudomonas normal flora |
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Spp. found in urine specimens?
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S. saprophyticus
Enterococcus Enterics Pseudomonas |
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What is Hektoen agar selective for?
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Salmonella/Shigella
Lactose/Sucrose/SALICIN ~6x bile salt conc of MacLac Iron to indicate H2S production |
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What is XLD agar selective for?
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Salmonella/Shigella
Sodium desoxycholate Lactose/Sucrose/XYLOSE Iron to indicate H2S production |
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What color do fermenters appear on Hektoen agar?
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yellow-orange colonies
may produce H2S --> black centers agar starts off green. |
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How do you interpret the results of a Lysine Iron Agar slant?
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detects how org metabolizes lysine: decarboxylate or deaminate
WHOLE TUBE: purple pH indicator --> yellow due to glucose fermentation SLANT: peptone oxidation reverts slant to purple color, deamination turns it red BUTT: lys decarboxylation will revert yellow --> purple color if + for lys decaryoxylase **read slant for deamination, butt for decarboxylation |
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How do you interpret the results of a Triple Sugar Iron agar slant?
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glucose, sucrose, lactose
reddish-orange --> yellow due to acidic fermentation products K/K = no fermentation A/A = fermentation G/L/S A/A/H2S = fermentation G/L/S + black ppt K/A = fermentation, peptone oxidation K/A + H2S = fermentation, peptone oxidation, black ppt |
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What color do fermenters appear on XLD agar?
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yellow colonies
H2S production --> black centers agar starts off pink |
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What are the selective agents in Clostridium difficile agar?
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cycloserine
cefoxitin |
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Which gives more reliable results WRT H2S production, TSI or LIA slants?
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TSI
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Why might one see a reversion of a pH indicator color change after initial acidification of a slant in LIA/TSI tests?
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switching to peptone oxidation produces basic byproducts and neutralizes acidic fermentation products.
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What is the general procedure for isolation of Salmonella/Shigella from stool specimens?
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1. streak onto Mac/Hek/XLD
2. pick non-fermenters to do TSI/LIA 3. GLUCOM tests |
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What is the major difference between Salmonella and Shigella colonies on Hek and XLD agar?
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Salmonella have black centers due to H2S production.
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What battery of tests is used to identify lactose fermenting members of Enterobacteriaceae?
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LOVMIC only
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What battery of tests is used to identify NON lactose fermenting members of Enterobacteriaceae?
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LOVMIC GLUT
do Glucose, lactose, Urea, TSI to further characterize |
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What color does XLD start off?
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pinkish
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What color does Hektoen agar start off as?
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green or blue
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Why is Campylobacter so hard to isolate?
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-microaerophilic!!!
don't see unless you look for it. --> plate onto blood+abx, incubate @ 42 in 5-7% oxygen |
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Which members of the Enterics are Lactose negative?
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Salmonella, Shigella, Proteus
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Which members of the Eneterics are Lactose positive?
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Escherichia, Enterobacter, Klebsiella, 50% of Citrobacter
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Which members of the Eneterics are Indole positive?
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Escherichia, Proteus vulgaris
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What organism do you suspect if your TSI shows up K/K for a GNR?
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Pseudomonas
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Which members of the Eneterics are motility negative?
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Shigella, Klebsiella
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Which members of the Eneterics are Lysine deaminase positive?
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Proteus spp.
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Which members of the Eneterics are Urease positive?
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Strong +: Proteus spp.
Weak +: Klebsiella |
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Which members of the Eneterics are Voges-Proskauer butanediol positive?
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Enterobacter, Klebsiella
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Which members of the Eneterics are positive for H2S production?
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SPACE
Salmonella Proteus Arizona Citrobacter Edwardsiella |
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Why are Shigella species typically harder to isolate than Salmonella species?
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Shigella gives a lot of negative test results, doesn't do much; no distinguishing test results.
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Routine setup for stool specimens?
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Regular MacLac, XLD, Hek at 35C (not in CO2)
Campy-CVA in CampyPak at 42 |
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Routine setup for urine specimens?
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BA and Mac (w/o CV)
Incubate 35 C 18-24 hrs |
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Routine setup for sputum specimens?
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Chocolate, BA, Mac
Incubate 35C in CO2 |
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Common pathogens in sputum specimens?
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Strep pneumoniae
Staph aureus H. influenzae Klebsiella Pseudomonas |
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Common pathogens (of interest in 443) found in stool specimens?
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Campylobacter
Salmonella Shigella |
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Common pathogens in urine specimens?
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Enterics: E. coli, Enterobcter, Klebsiella, Proteus
Pseudomonas Staph saprophyticus Enterococcus |
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Routine setup for CSF specimens?
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Chocolate, Blood agar, BHI
Increased CO2 at 35C |
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Specimens that require incubation in CO2?
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CSF, Sputum, Wound BA
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Routine setup for wound specimens?
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BA in CO2
BA anaerobically MacLac all at 35C |
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What is the expected color change for a positive carbohydrate "O/F" medium test result?
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yellow color = carbohydrate utilization under given conditions (with or without mineral oil to simulate anaerobic conditions and promote fermentation)
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What are the key test results that distinguish Klebsiella from other UTI pathogens?
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+ urease
- motility + bile esculin |
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What is the key test result that distinguishes Citrobacter from other common UTI pathogens?
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+ indole
+ CITrate test CITrobacter has + CITrate test |
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What is the expected color change for a positive carbohydrate "O/F" medium test result?
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yellow color = carbohydrate utilization under given conditions (with or without mineral oil to simulate anaerobic conditions and promote fermentation)
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What are the key test results that distinguish Klebsiella from other UTI pathogens?
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+ urease
- motility + bile esculin |
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What is the key test result that distinguishes Citrobacter from other common UTI pathogens?
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+ indole
+ CITrate test CITrobacter has + CITrate test |
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Which organisms are lecithinase +?
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Clostridium perfringens
Bacillus spp. Staph aureus |
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Which organism is resistant to penicillin?
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Bacteroides fragilis
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