Flashcards in Microbiology: Exam 2 Deck (78):
-Reduce nitrates to nitrites
-Oxidase negative (except plesiomonas)
-Motile at body temp (except for Kleb, Shigella, Yersina)
MacConkey agar differentiates..
EMB agar differentiates..
lactose fermentation of enteric bacilli
positive = purple
E. coli = greenish hue
HE agar differentiates..
lactose and sucrose fermentation
most non pathogens = orange
pathogens = green/blue color (salmonella = black)
XLD agar differentiates
sucrose, lactose, and xylose fermentation
Yellow colonies: E. coli, Citrobacter
Red or colorless colonies: Shigella. (salmonella = black center)
-pink colonies on Mac plates (because it ferments lactose)
-IMVC = ++--
heat stable antigen located in LPS
5 types of E. coli
1. Enteropathogenic: infant diarrhea in children less than a year old. no blood in stool, just mucus.
2. Enterotoxigenic: Traveler's diarrhrea. toxins that lead to hyper secretion of fluids
3. Enteroinvasive: very similar to shigella. blood in stool. damage to intestinal mucosa.
4. Enterohemorrhagic: conditions include hemolytic uremic syndrome, colitis, fatality. bloody diarrhea without WBC (differentiates from Shigella). O157:H7 Shiga toxin.
5. Enteroadherent: UTI's and diarrheal disease <- mostly in children
detected on SMAC plate
doesn't ferment sorbitol
Uropathogenic E. coli
most common cause of UTI's
Kleb, Enterobacter, Serratia, Pantoea, Cronobacter, and Hafnia are all.....
IMVC --++ <--- **Few exceptions**
Wound, pneaumonia, and UTI infections
K. pneaumoniae has capsule
K. oxytoca = Indol +
E. cloacae- doesn't produce lysine decarboxylase (only one)
similar to Kleb (differentiate by motility, Pantoea is motile)
lysine, ornithine, and arginine negative
-ONPG positive (means slow lactose fermentor)
-highly resistant to antimicrobials
linked to gastroenteritis
-produce swarming on lab media. STINKS
-phenylalanine deaminase positive
P. mirabilis- most common. indole negative. ornithine decarboxylase positive. TSI: K/A with H2S
P. vulgaris- TSI: A/A. sometimes produces H2S. indole positive. ornithine decarboxylase negative.
E. tarda is only pathogen
TSI: K/A with H2S
C. freaudnii- nosocomial UTI's, endocarditis.
to differentiate from Salmonella: Citrobacter hydrolyzes urea but not decarboxylate lysine and Salmonella does the opposite
(M)ethyl red test aka MR
(V)oges-Proskauer test aka VP
-colorless colonies with black centers (H2S- except for S. paratyphi A)
-negative for most tests.
-virulence factors- fimbriae for adhesion
-can cross GI tract into bloodstream
-has a capsular antigen similar to K
Subgroup 1 Salmonella
how to differentiate:
S. typhi- ornithine decarboxylase negative
S. paratyphi- lysine decarboxylase negative
S. choleraesuis- trehalose fermentation negative
-Food poisoning with vomitting/diarrhea (do not use anti-diarrheal) caused by bacteria itself. need large [bacteria].
-can be carrier state in gall bladder
-Typhoid fever: flu-like symptoms and then constipation. can enter lymphatic & vascular system. engulfed by monocytes but then released. invades gall bladder and Peyer's patches. can lead to necrosis. found in blood/urine first and then stool.
-resistant to stomach acid
-low [bacteria] for infections
S. sonnei is ONPG and ornithine decarboxylase positive
Types of Shigella
Group A: S. dysenteriae- most serious. developing countries
Group B: S. flexneri- 2nd most common in US. gay male sex.
Group C: S. boydii- developing countries
Group D: S. sonnei- most common in US. usually non-fatal, less severe symptoms
dysentery- most severe. shedding of intestinal mucosa, blood in stool, ulcers, tenesmus (rectal prolapse)
TSI: K/A. CIN agar can differentiate.
Y. pestis- safety pin appearance on Gram stain. Class A bioterrorism agent. transmission through rodent bites.
Y. enterocolita- most common. contact with pigs, dogs, cats. survives in cold temperatures. motile at 25 degrees, not 37. stimulates appendicitis. ornithine decarboxylase positive.
Y. pseudotuberculosis- ingestion of fecal material. motile at 25 degrees.
Carb Utilization test
-lactose degradation- used to ID enteric pathogens.
consists of glucose and galactose
2 enzymes: beta-galactoside and permease
-slow fermentators don't have permease
-oxidation- utilizes carbs aerobically
-fermentation- utilizes carbs anaerobically
-asacchrolytic- doesn't utilize carbs
O/F Basal Media
helps classify as either oxidizer or fementator
two tubes- one aerobic, one anaerobic. can be any sugar
+ for fermentator- yellow throughout both tubes
+ for oxidizer- aerobic tube is yellow, anaerobic is green
- for carb use- both green
-lactose and sucrose in 10:1 ratio to glucose
-black precipitate = ferrous sulfate
-phenol red = pH indicator
-no fermentation = red (K/K)
-can create gas bubbles
-glucose fermentation: A/A then K/A after 24 hours.
if still A/A after 24 hours: either lactose or sucrose.
on MAC plate: if clear colony then its sucrose.
tests for slow lactose fermentators
turns yellow for positive rxn
Methyl-Red and Voges Proskauer test
MR: glucose->pyretic acid->mixed acid ferm (4.4)
PV: glucose->butylene glycol ferm->diacetyl + KOH + alpha-naphthol
red = positive for both tests
tests ability of enzymes to remove carboxyl group (COOH) from lysine, ornithine, arginine.
dihydrolase: arginine -> ornithine
deamination or decarboxylation of lysine.
deamination = reddish color
decarboxylation = purpleish color
removes amine group from amino acids
PAD tests- produces phenylpyruvic acid. add 10% Ferric chloride. green = positive
citrate used as sole carbon source
blue = positive
loss of gelling.
+ = liquefaction
breaks tryptophan down into indole.
add Ehrlich's reagent (PDAB) or Kovac's. red = positive
two reagents: Sulfanilic acid and NNDN.
red on 1st step OR gas production w/o red = + for reduction to NO2
next add zinc, if red still..then negative (zinc forced the run)
purple = positive
be able to recognize that the really long enzyme name is associated with this test
hydrolyze urea to ammonia, water, and CO2
bright pink = positive
-found in fresh, brackish, and salt water
-Gneg straight rods. curved in clinical specimens.
-string test positive.
-Vibriostat disk (O/129) sensitive
-halophilic (except for V. cholerae & V. mimicus)
V. cholerae- O1, O139 antigens. El Tor biogroup. causative agent of cholera . rice water stool- watery diarrhea with flecks of mucus (caused by toxins) fluid loss.
V. parahaemolyticus- associated with seafood (oysters). heat stable hemolysin. Gastroenteritis
V. vulnificus- raw undercooked seafood. wound infections, GI, sepsis. lactose positive (only one)
V. alginolyticus- most frequent, least pathogenic
yellow: V. cholerae and V. alginolyticus
green: V. parahaemolyticus and V. vulnificus
-mesophilics are motile
-psychrophillics are non motile
-string test negative
-resistant to vibriostat disc
-glucose & inositol fermentating
-oxidase positive (unlike enterobacteriaciae)
-motile via polar flagella
-cold-blooded animals (zoo keepers)
-sensitive to vibriostat disc (unlike aeromonas)
-can't grow in high salt (unlike vibrios)
-positive for ornithine/lysine decarboxylase and arginine dihydrolase
-microaerophillic- 5% O2 is optimal. likes to grow @ 42 degrees.
-looks like seagull wings
-direct contact with animals & improperly cooked poultry
C. jejuni: #1 cause of diarrheal illness worldwide
C. fetus: can cause animal abortions
H. pylori colonizes 20-40% of adults
-urease positive (rapid color change on Christenen's urea medium)
-causes stomach cancer/ulcer formation
-Campy BAP, skirrow agar?
All Non-Fermentators (glucose)
-G neg rods
-doesn't ferment sugars, only oxidizes them
-generally oxidase positive
-prefer moist environments (fluids in hospitals)
-can withstand treatment with chlorhexidine
-sepsis, wound infections, meningitis, osteomyelitis
-grape-like odor, blue-green pigment on SBA
-variable on MAC plate
-arginine dihydrolase positive
-grows at 42 degrees (hot tub syndrome)
-Exotoxin A- similar to diphtheria toxin by blocking protein synthesis
-nosocomial UTI's/bacteremia, pneaumonia, Cystic Fibrosis pts
wrinkly leathered colonies
-found in the environment and hospitals (ventilators, catheters, humidifiers)
-oxidase and catalase negative
-on MAC plate: non-lactose fermenter, purplish hue. non-hemolytic
A. baumanii: glucose oxidizer. resistant to antibiotics
A. lwoffii- glucose negative. less virulent
almost entirely nosocomial. also in environment
S. maltophilia: rough lavender-green colonies with ammonia odor.
on MAC: NFL. DNAse positive. lysine decarboxylase positive
-nosocomial. pneumonia especially with CF pts
-oxidase is weak/slow positive (can be variable)
-on SBA: non-wrinkly yellow-green colonies
-ONPG and lysine decarboxylase positive
-utilizes glucose, lactose, maltose, and mannitol
-arginine dehydrolase negative (this is how you differentiate this from pseaudomonas)
-OFPBL & BCSA agars are selective for this organism
-contaminant of hospital equipment
-indole, gelatin hydrolysis, oxidase, and DNAse positive
Elizabethkingia meningoseptica: no growth on MAC plate. meningitis and septicemia of newborns, especially neonates.
brown-tan colonies on SBA
**H2S on TSI**
Haemophilus & Pasteurella are both..
-part of the family Pasteurellaceae
-G neg rods
-reduces nitrate to nitrite
-parasite in mucous membranes
-hemolysis, dies rapidly on plates
-requires X factor (hemin), V factor (NAD) or both (if its called para_____ then it only requires V factor.
-wont grow on MAC but will on CAP with bacitracin
-satellitism around S. aureus
required X and V. neg for porphyrin
virulence: capsule, IgA protease, LPS, adherance factors
- Serotype B (HiB) = #1 cause of meningitis in children that aren't vaccinated
-causes pink eye and Brazilian purpuric fever
-required X and V
-STI. extremely fastidious (needs to culture for 7 days)
-chancroid, painful lesions
-requires just X
Mueller Hinton agar with X & V strips
if it doesn't require X factor, thats a positive result (pink-red-orange color)
-all normal flora of oral cavity
-Gneg rods but won't grow on MAC
star formation at center of colonies
-infects aortis valve the most
-pitting on agar
-human bite and fight wounds
-bleach like odor, pits agar
isolates of children <3yo- affects bones and joints
-Gneg rods that may fusiform (thick in center, thinner at ends)
-producing gliding motility
-bipolar staining (safety pin appearance)
-no growth on MAC
-exposure from cat/dog bites/scratches
-weak acid fermentation
-different types of Brucella can be differentiated by growth on agars with different dyes
-brucellosis, undulant (persistant) fever
-contact with animals and their products
-H2S and urease positive within 2hours
requires cysteine for growth
-inhalation of aerosols (no person to person contact)
-epidemics via air conditioners
- can live within macrophages
- pneaumonia, legionnaire's disease, pontiac fever caused by L. pneaumophili
-wont Gstain well, no growth on SBA
-grows on BCYE agar