Week 4 no week 3 Flashcards

Question

which strains of Shigella are associated with what and how to ID

Answer 1

S. sonnei Serogroup D- watery diarrhea Predominant strain found in N.A. S. dysenteriae Serogroup A –bloody stool (Shiga toxin) within hours, associated with hemolytic uremic syndrome (HUS) S. flexneri Serogroup B – Most common cause of the endemic form of shigellosis Endemic form cause of most shigellosis-related death S. boydii Serogroup C– dysentery ID via biochemical testing, Vitek NOT MALDI -serology LATEX TESTING GOR GROUPS A-D

Answer 2

-E COLI 0157:H7 -produces cytotoxins (verotoxins 1,2) -serotoxin VI is similar to Shiga toxin of S dysteneraiae - shiga toxin -cow vaccine developed

Answer 3

-dairy and beef cattle -contaminated food or water -if ground beef isnt handled properly -apple cider, bean sprouts, lettuce, mayonnaise

Answer 4

-diarrhea can be bloody -low or NO fever -no leuks in stool (different from Shigella) -Hemolytic uremic syndrome (HUS) - RBC prematurely destroyed and clog the kidneys causing Microangiopathic hemolytic anemia , thrombocytopenia, acute renal disease

Answer 5

-NON MOTILE, sorbitol negative so use MAC with sorbitol (no color) -serology with 0157:H7 antiserum

Answer 6

Caused: -poor hygiene, contaminated food/water Virulence factor: -pili (colonization), toxins that increase water and lytes secretion -heat liable or heat stable toxin production Clinical -travelers diarrhea- DUKORAL -infant bacterial diarrhea

Answer 7

Caused: -outbreaks in nurseries and daycare Virulence : -pili- mucosal bowel attachment -does NOT produce enterotoxin or Shiga toxin -NOT invasive Clinical -infantile diarrhea

Answer 8

-Watery diarrhea, fever but can progress to dysentery like symptoms, bloody stool with mucus Virulence -invades enterocytes in colon and destroys intestinal mucosa - similar to Shigella can be NON MOTILE

Answer 9

-Large grey NH or BH-Ecoli -collect stool specimen early into the illness so the org that caused it is still there in large numbers if collected when youre recovering then it can be negative -needs to be processed in 2hours -transport media when delayed Cary Blair -if you have enteric fever like typhoid it will be recovered from blood not stool -NO GRAM on stool -culture on enteric media - MAC, SMAC, HEK, CIN, Campylobacter and Selenite broth -NOT on BA, CHOC OR ANAO2 due to excess NF in stool can be overgrown -Biochemical tubes -MALDI -REPORT to public health and send to their lab

Answer 10

-LF or NLF -selective for GNBs but not all that grow on it are Enterobacteriaceae -selective and differential -Bile salt and CV inhibit GP - SELECTIVE -Lactose and neutral red indicator DIFFERENTIAL based on lactose fermentation

Answer 11

-Bile salts, sodium citrate, ferric citrate and brilliant green -SELECTIVE to removed non sig GNB -Neutral red is DIFFERENTIAL also indicator since it detects lactose fermentation -H2S indicator

Answer 12

DIFFERENTIAL - CHO fermentation and H2S production ; 3 carbs Lac, Suc, Salicin SELECTIVE - bile salts inhibit GP INDICATOR - bromothymol blue DETECTION OF H2S - sodium thiosulphate and ferric ammonium citrate Fermenter - yellow -orange Non fermenter - green-blue

Answer 13

-just like MAC but instead of lactose it has sorbitol -differentiates between non sorbitol fermenting EHEC or E. coli 0157:H7) fermenter- SF- pink NON sorbitol fermenter NSF - no color

Answer 14

Selectively isolate Yersinia enterocolitica from stool specimens SELECTIVE- Antimicrobics: C, I, N INDICATOR Neutral red, mannitol Yersinia- small dark red center with clear margin (“bull’s eye)

Answer 15

Maldi-tof - Known limitations: can’t tell the difference between E. coli and Shigella Vitek2 GN ID card API 20E Biochemical tubes PCR Confirmation/typing using antisera E.g. E. coli O157

Answer 16

Purpose: distinguish between the GNB in the Enterobacteriaceae family (oxidase -) and Pseudomonas (oxidase +) Reagent: 6% tetramethyl phenylenediamine OR Dimethyl-p-phenylenediamine oxalate reagent Interpretation: If oxidized by the cytochrome oxidase system, they turn purple (positive)

Answer 17

Purpose: Determines if organism is capable of metabolizing CHO aerobically (oxidative), anaerobically (fermentative) or not at all * All Enterobacteriaceae are all positive for both Ingredients: glucose (can have other sugars e.g. maltose), peptone, bromothymol blue Set up: Run in duplicate, stab both tubes with organism, cover one with oil

Answer 18

Purpose: To determine if an organism can reduce nitrate to nitrites or nitrogen gas (ammonia). Enterobacteriaceae reduce nitrates to nitrites Set up: (Check for bubbles in Durham tube before inoculating). 2 Reagents : Dimethyl-α-naphthylamine in glacial acetic acid, Sulfanilic acid in glacial acetic acid (Nitrate A and Nitrate B) Interpretation : observe for the presence of gas in the Durham tube before adding reagents If it turns red after the addition of reagents: Nitrates reduced to nitrites. If NO colour, add zinc dust –if it turns red then nitrates not reduced, no colour then nitrates reduced to nitrogen gas (N2) This test is can be done on an API strip (in the glucose well after the result is recorded; observe for the presence of gas)

Answer 19

Purpose: Detects the fermentation of glucose (0.1%), lactose (1%), and/or sucrose (1%), detects gas production (H2, CO2), and H2S production (ferrous sulfate and sodium thiosulfate) pH indicator: Phenol red Set up: stab butt, streak slant, loose caps, incubate 35C in O2 Interpretation: observe for the presence of gas, H2S and colour change in the slant and butt A/A=all sugars fermented ALK/ALK=no CHO fermented AEROBIC ALK/A = only glucose fermented add g if you see gas or H2S if black

Answer 20

Purpose: Used in the identification of Enterobacteriaceae –determines 3 reactions (tests) Set up: Inoculate by stabbing straight down (and back up). Incubate O2 at 35°C Reagent: Kovac’s reagent Interpretation: observe for motility and H2S (black) before adding reagent. Indole: Observe for red at top (after addition of Kovac’s) if all black then MOTILE AND H2S

Answer 21

Purpose: determine if the organism produces urease (to break down urea) Set up: Inoculate slant with zigzag streak, loosen cap, Incubate O2 at 35C Interpretation: observe for intense pink colour (positive) – the entire tube does not always go pink You can check against an un-inoculated tube

Answer 22

Purpose: to determine if an organism has the ability to decarboxylate an amino acid useful for identification of gram negative bacilli –especially Enterobacteriaceae Tubes contain the selected amino acid (not control tubes), glucose, peptones and 2 indicators: bromocresol purple and cresol red. Set up: test must be set up with decarboxylase control (does not contain the amino acid), Inoculate the liquid medium just below the surface, cover each tube with oil WHY? Interpretation: purple is a positive test Control tube must be valid (yellow)

Answer 23

Purpose: to determine if the organism uses citrate as a sole source of carbohydrate. Used in the identification of many organisms including Enterobacteriaceae Ingredients: sodium citrate, ammonium salts (source of nitrogen), Bromothymol Blue indicator Set up: Lightly inoculate by streaking the slant. Incubate tubes with loose caps at 35°C in O2 Interpretation: growth and or change to blue: positive no growth and no change in colour: negative

Answer 24

Purpose: Useful in identification of Proteus, Morganella and Providencia species. Set up: streak slant with a zigzag pattern Reagents: Ferric chloride Interpretation: Presence of a dark green colour after the addition of reagent (positive)

Answer 25

Purpose: Detects the presence of mixed acids from the breakdown of glucose. Useful in the identification and differentiation of Enterobacteriaceae Set up: Inoculate liquid (not too heavy) media below surface. Incubate in O2 at 35°C (ideal 48 hours) Reagents : Methyl red indicator Interpretation: Red colour: positive

Answer 26

Purpose: Useful in the identification of Enterobacteriaceae Set up: Inoculate liquid media below surface Reagents: alpha naphthol and Potassium hydroxide Interpretation: After adding reagents, observe for pink colour within 10 minutes (positive). Ecoli is NEG and E aerogenes is POS Additional information: Media is the same as that used for Methyl Red READ the SOP before adding reagents –you need to split the tube contents from MR This test is on the API strip –same reagents but add them in the opposite order

Answer 27

Purpose: ONPG is used to detect β-galactoside permease negative, β galactosidase positive organisms, used to determine if the organism is a “slow” or “late” lactose fermenter. Set up: Place disc in 0.5 mL saline in tube, inoculate and incubate in O2 @35°C Interpretation: any shade of yellow is positive NLF will be negative LF and LLF organisms will be yellow