Microbiology: Exam 2 Flashcards
All Enterobacteriaceae
- Gram negative
- Ferment glucose
- Reduce nitrates to nitrites
- Oxidase negative (except plesiomonas)
- Motile at body temp (except for Kleb, Shigella, Yersina)
MacConkey agar differentiates..
lactose fermentation
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)
E. Coli
- pink colonies on Mac plates (because it ferments lactose)
- sex pilli/fimbriae
- beta hemolysis
- O,H,K antigens
- IMVC = ++–
- TSI: A/A
O antigen
heat stable antigen located in LPS
H antigen
flageller antigen
K antigen
capsular antigen
5 types of E. coli
- Enteropathogenic: infant diarrhea in children less than a year old. no blood in stool, just mucus.
- Enterotoxigenic: Traveler’s diarrhrea. toxins that lead to hyper secretion of fluids
- Enteroinvasive: very similar to shigella. blood in stool. damage to intestinal mucosa.
- Enterohemorrhagic: conditions include hemolytic uremic syndrome, colitis, fatality. bloody diarrhea without WBC (differentiates from Shigella). O157:H7 Shiga toxin.
- Enteroadherent: UTI’s and diarrheal disease
O157:H7 toxin
E coli
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 –++
Klebsiella
non-motile.
TSI: A/A
K. pneaumoniae has capsule
K. oxytoca = Indol +
Enterobacter
TSI: A/A
E. cloacae- doesn’t produce lysine decarboxylase (only one)
Pantoea
similar to Kleb (differentiate by motility, Pantoea is motile)
lysine, ornithine, and arginine negative
Serratia
- ONPG positive (means slow lactose fermentor)
- DNAse positie
- highly resistant to antimicrobials
Hafnia
BEER
linked to gastroenteritis
Proteaus
- produce swarming on lab media. STINKS
- phenylalanine deaminase positive
- urease 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.
Edwardsiella
E. tarda is only pathogen
Indole positive.
TSI: K/A with H2S
Citrobacter
C. freaudnii- nosocomial UTI’s, endocarditis.
to differentiate from Salmonella: Citrobacter hydrolyzes urea but not decarboxylate lysine and Salmonella does the opposite
IMVC test
(I)ndole production
(M)ethyl red test aka MR
(V)oges-Proskauer test aka VP
(C)itrate production
Salmonella
- colorless colonies with black centers (H2S- except for S. paratyphi A)
- TSI: K/A
- negative for most tests.
- virulence factors- fimbriae for adhesion
- can cross GI tract into bloodstream
- toxins
- O,H antigens
- has a capsular antigen similar to K
Subgroup 1 Salmonella
human infections
how to differentiate:
S. typhi- ornithine decarboxylase negative
S. paratyphi- lysine decarboxylase negative
S. choleraesuis- trehalose fermentation negative
Salmonella infections
- 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.
Shigella
- non-motile.
- TSI: K/A
- resistant to stomach acid
- low [bacteria] for infections
- Shiga toxin
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
Shigella infections
dysentery- most severe. shedding of intestinal mucosa, blood in stool, ulcers, tenesmus (rectal prolapse)
Yersina
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 fermentation
- 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
TSI slant
- 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.
ONPG test
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
Decarboxylase test
tests ability of enzymes to remove carboxyl group (COOH) from lysine, ornithine, arginine.
dihydrolase: arginine -> ornithine
LIA Slant
deamination or decarboxylation of lysine.
deamination = reddish color decarboxylation = purpleish color
Deaminase test
removes amine group from amino acids
PAD tests- produces phenylpyruvic acid. add 10% Ferric chloride. green = positive
Citrate utilization
citrate used as sole carbon source
blue = positive
gelatinase production
loss of gelling.
+ = liquefaction
indole tests
breaks tryptophan down into indole.
add Ehrlich’s reagent (PDAB) or Kovac’s. red = positive
NO3 reduction
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)
Oxidase
purple = positive
be able to recognize that the really long enzyme name is associated with this test
Urease
hydrolyze urea to ammonia, water, and CO2
bright pink = positive
Vibrios
- found in fresh, brackish, and salt water
- causes epidemics
- Gneg straight rods. curved in clinical specimens.
- string test positive.
- catalase/oxidase positive
- Vibriostat disk (O/129) sensitive
- halophilic (except for V. cholerae & V. mimicus)
Vibrio species
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
TCBS agar
yellow: V. cholerae and V. alginolyticus
green: V. parahaemolyticus and V. vulnificus
Aeromonas
- oxidase positive
- mesophilics are motile
- psychrophillics are non motile
- beta hemolysis
- indole positive
- string test negative
- resistant to vibriostat disc
Plesiomonas
- glucose & inositol fermentating
- oxidase positive (unlike enterobacteriaciae)
- facultatively anaerobic
- 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
Campylobacter
- microaerophillic- 5% O2 is optimal. likes to grow @ 42 degrees.
- oxidase/catalase positive.
- looks like seagull wings
- darting motility
- direct contact with animals & improperly cooked poultry
C. jejuni: #1 cause of diarrheal illness worldwide
C. fetus: can cause animal abortions
Helicobacter
H. pylori colonizes 20-40% of adults
- microaerophillic
- urease positive (rapid color change on Christenen’s urea medium)
- causes stomach cancer/ulcer formation
- corkscrew motility
- Campy BAP, skirrow agar?
All Non-Fermentators (glucose)
- G neg rods
- doesn’t ferment sugars, only oxidizes them
- generally oxidase positive
- TSI: K/K
- prefer moist environments (fluids in hospitals)
- can withstand treatment with chlorhexidine
- sepsis, wound infections, meningitis, osteomyelitis
Pseudomonas aeruginosa
- grape-like odor, blue-green pigment on SBA
- variable on MAC plate
- beta hemolysis
- oxidase positive
- arginine dihydrolase positive
- grows at 42 degrees (hot tub syndrome)
- citrate positive
- acetamide utilization
- Exotoxin A- similar to diphtheria toxin by blocking protein synthesis
- nosocomial UTI’s/bacteremia, pneaumonia, Cystic Fibrosis pts
P. stutzeri
wrinkly leathered colonies
Acinetobacter
- found in the environment and hospitals (ventilators, catheters, humidifiers)
- oxidase and catalase negative
- coccobacilli
- on MAC plate: non-lactose fermenter, purplish hue. non-hemolytic
A. baumanii: glucose oxidizer. resistant to antibiotics
A. lwoffii- glucose negative. less virulent
Stentrophomonas
almost entirely nosocomial. also in environment
S. maltophilia: rough lavender-green colonies with ammonia odor.
on MAC: NFL. DNAse positive. lysine decarboxylase positive
Burkholderia Cepacia
-nosocomial. pneumonia especially with CF pts
-oxidase is weak/slow positive (can be variable)
-on SBA: non-wrinkly yellow-green colonies
motile
-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
Flavobacteriaceae
- contaminant of hospital equipment
- indole, gelatin hydrolysis, oxidase, and DNAse positive
- non motile
Elizabethkingia meningoseptica: no growth on MAC plate. meningitis and septicemia of newborns, especially neonates.
Shewanella
brown-tan colonies on SBA
H2S on TSI
Haemophilus & Pasteurella are both..
- part of the family Pasteurellaceae
- G neg rods
- non-motile
- oxidase/catalase positive
- reduces nitrate to nitrite
Haemophilus
- 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
H. influenzae
-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
H. aegyptius
- causes pink eye and Brazilian purpuric fever
- required X and V
H. ducreyi
- STI. extremely fastidious (needs to culture for 7 days)
- chancroid, painful lesions
- requires just X
- nastaaaaaay
H. aphrophilus
endocarditis
Culturing haemophilus
Mueller Hinton agar with X & V strips
porphyrin test
if it doesn’t require X factor, thats a positive result (pink-red-orange color)
HACEK
(H)aemophilus (A)citnobacillus (C)ardiobacterium (E)ikerella (K)ingella
- all normal flora of oral cavity
- endocarditis
- increase CO2
- Gneg rods but won’t grow on MAC
A. acitomycetemocommitans
star formation at center of colonies
C. hominis
- infects aortis valve the most
- pitting on agar
E. corrodens
- human bite and fight wounds
- bleach like odor, pits agar
K. kingae
isolates of children <3yo- affects bones and joints
Capnocytophaga
- Gneg rods that may fusiform (thick in center, thinner at ends)
- producing gliding motility
Pasteurella myltocida
- bipolar staining (safety pin appearance)
- no growth on MAC
- exposure from cat/dog bites/scratches
- weak acid fermentation
Brucella
- different types of Brucella can be differentiated by growth on agars with different dyes
- brucellosis, undulant (persistant) fever
- contact with animals and their products
- catalase/oxidase positive
- H2S and urease positive within 2hours
Franscisella
requires cysteine for growth
rabbit fever
Legionella
- 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
- aquatic sources
- wont Gstain well, no growth on SBA
- requires L-cystein
- grows on BCYE agar
Bordatella
- B. pertussis & B. parapertussis cause whooping cough
- Pertussis toxin- interferes with signal transduction
- breathing in aerosols, very contagious
- specimens are best from nasopharynx on calcium alginate or Dacron swabs
- Regen-Lowe transport medium
- Bordet-Gengou agar: smooth silver pinpoint colonies resembling mercury droplets
