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HCLD Micro > Gram Neg Rods > Flashcards

Gram Neg Rods Flashcards

1
Q

Enterics characteristics

A

-GNR
-Ox= (except Plesiomonas)
-glu+
-nit+
-motile (except Kleb, Shig, Yersinia)

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2
Q

Enterics Virulence Factors

A

1) O antigen
–Somatic antigen
–Heat stable
–external component of LPS
–O for OUTER
2) K antigen
–Heat labile
–Capsular antigen
–K1 of E coli and Vi of Salmonella typhi
3) H antigen
–Heat labile
–Flagellar antigen
–Motility

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3
Q

Opportunistic enterics are

A

1) E. coli
2) Citrobacter
3) Enterobacter
4) Kleb
5) Proteus
6) Serratia

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4
Q

E coli diseases

A

1) ETEC (Toxic)
2) EIEC (Invasive)
3) EPEC (Pathogenic)
4) EAEC (Aggregative)
5) UPEC
6) Neonatal meningitis
7) Sepsis

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5
Q

Enteric disease severity is dependent on…

A

Depth of intestinal invasion

1) No invasion
–bind but don’t enter
–enterotoxin mediated (cAMP/cGMP)
–watery diarrhea w/o fever
–ETEC, cholera

2) Invasion of the intestinal epi
–bind and destroy cells
–WBCs in stool and fever
–Blood in stool
–EIEC, Shigella, Salmonella enteritidis

3) Invasion of lymph nodes and blood stream
–fever, headache, inc. WBCs
–possible lymph node swelling and septicemia
–Salmonella typhi, Yersinia enterocolitica, Campylobacter jejuni

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6
Q

ETEC disease

A

-Traveler’s Diarrhea
-Most common cause of diarrhea in the US
-Contaminated food/water
-Needs high infectious dose
-Mild diarrhea (watery, cramps, nausea, NO fever or vomiting)
-Self-limiting

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7
Q

ETEC virulence

A

1) Pili bind for colonization
2) Enterotoxins
– LT
—-similar to cholera toxin
—-A (active) and B (binding) subunits
—-Activates cAMP -> hypersecretion of electrolytes ->watery diarrhea
– ST (Heat stable)
—-Activates cGMP -> hypersecretion of electrolytes

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8
Q

EIEC disease

A

-Similar symptoms to Shigella but needs much higher infectious dose
-Dysentery (necrosis, ulceration, inflammation of large bowel)
–Penetration, invasion, and destruction of intestinal mucosa
-Person-to-person or fecal-oral transmission
-watery diarrhea, fever, severe cramps, malaise
-vir factor encoded on plasmid (same plasmid that’s in Shigella)

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9
Q

EPEC disease

A

-Diarrhea in infants (P - think Pediatrics)
–daycares and hospital nurseries
-Attaches to cell surface and changes microvilli
-low-grade fever, malaise, vomiting, diarrhea
-mucus in stool but no blood

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10
Q

EHEC disease

A

-E coli O157:H7
-Inflammation and bleeding (hemorrhagic colitis)
-Watery, bloody diarrhea, abdominal cramps, sometimes fever
-No WBCs in stool (unlike EIEC)
-Undercooked beef

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11
Q

EHEC virulence

A

1) Shiga toxin (Stx)
–aka verotoxin
–Inhibit protein synthesis of the 60S ribosome = cell death

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12
Q

EHEC diagnosis

A

1) SMAC plates (EHEC does not ferment sorbitol)
2) MUG test
–screens for production of B-glucouronidase
–EHEC will be negative for production
3) Neutralizing Ig test against verotoxin
4) ELISA
5) Latex agglutination

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13
Q

HUS

A

-Caused by EHEC
-anemia, thrombocytopenia, renal failure
-Microthrombi leads to anemia
-Cell damage increases need for clotting which leads to thrombocytopenia
-Shiga toxin has a high affinity for globotriaosylceramide (Gb3) membrane receptor present in glomerular endothelium and tubular cells, causing widespread damage resulting in glomerular necrosis, cellular apoptosis, and microangiopathic thrombosis leading to acute renal injury

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14
Q

EAEC

A

-Aggregative or Adherent
-Diarrhea and UTIs
-Watery diarrhea, can be prolonged up to 2 weeks
-Stacked brick pattern on HEp2 cells

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15
Q

E coli non-GI diseases

A

1) Meningitis
–#2 cause of neonatal meningitis
–K1 antigen (capsule)
2) Sepsis
–Most common cause of gram neg sepsis
–usually hospitalized patients
3) UTIs
–Pili allow for adherence in bladder and kidney

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16
Q

Shigella characteristics

A

-Nonmotile
-Do not produce gas from glucose (exception S. flexneri types)
-Do not hydrolyze urea
-Do not produce H2S
-Do not decarboxylate lysine

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17
Q

Shigella disease

A

-Dysentery (acute inflammatory colitis)
-Diarrhea w/ blood and pus
-Fever
-Epithelial cell invasion
-Symptoms usually start 1–2 days after infection and last 7 days.
-CDC estimates about 450,000 cases of shigellosis occur in the United States every year, making it the third most common bacterial enteric disease.

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18
Q

Shigella types

A

1) Shigella dysenteriae (A) (12 serotypes)
2) Shigella flexneri (B) (6 serotypes)
3) Shigella boydii (C) (18 serotypes)
4) Shigella sonnei (D) (1 serotype)

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19
Q

Shigella non-GI disease

A

Possible complications from Shigella infections include:

1) Post-infectious arthritis.
–Joint pain, eye irritation, and painful urination
–~2% of people who are infected with Shigella flexneri.
–can last for months or years, and can lead to chronic arthritis. –caused by a reaction to Shigella infection that happens only in people who are genetically predisposed to it.
2) Bloodstream infections.
–most common among patients with weakened immune systems
3) Seizures
–Children who experience seizures while infected with Shigella typically have a high fever or abnormal blood electrolytes, but it is not well understood why the seizures occur.
4) Hemolytic-uremic syndrome or HUS.
–Shiga-toxin producing strains, most commonly Shigella dystenteriae

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20
Q

Salmonella cholerasuis group

A

-Motile
-H2S+
-Indole=
-VP=
-Urease=
-Causes three categories of infection
-Lives in animal GI tract

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21
Q

Salmonella Disease States

A

1) Typhoid fever
2) Carrier state
3) Sepsis/Bacteremia
4) Gastroenteritis

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22
Q

Salmonella virulence factors

A

1) Fimbriae
2) Enterotoxin
3) O antigen
4) H antigen
5) K antigen in S. typhi (Vi antigen)

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23
Q

Salmonella Gastroenteritis

A

-Contaminated food
-S. enterica subsp. enterica
-Poultry, milk, eggs, pets
-8-36 hours after ingestion
-Nausea, vomiting, fever, chills, watery diarrhea, pain
-Self-limiting
-More severe in sickle-cell, IBD, and immunocompromised patients
-Treat with fluid replacement

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24
Q

Salmonella Typhoid Fever (aka Enteric Fever)

A

-Salmonella typhi
-Invades intestinal epis -> lymph nodes -> multiple organ systems
-1-3 weeks after exposure
-Week 1: fever, malaise, anorexia, lethargy, dull frontal headache
-Invade and penetrate intestinal mucosa
–Patient gets constipation instead of diarrhea
-Invade regional lymph nodes
-Spread to blood
-Spread to liver, spleen, bone marrow
–Phagocytized by monocytes to become facultative intracellular
–Reproduce -> released back into blood stream -> pos blood culture
Weeks 2-3:
-Sustained fever with bacteremia
-Invade gall bladder and Peyer’s patches
–necrosis can occur = necrotizing cholecystitis, hemorrhage, perforation
-High levels in intestines -> pos stool culture
-Enlarged spleen
-Rose spots on abdomen

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25
Q

Typhoid fever complications

A

-Pneumonia
-Thrombophlebitis
-meningitis
-osteomyelitis
-endocarditis
-abscesses

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26
Q

Salmonella bacteremia

A

-Nontyphoidal Salmonella
-Does not involve GI tract
-Prolonged fever with intermitted bacteremia
-Serotypes Typhemurium, Paratyphi, and Choleraesuis
-HIGH RISK PATIENTS ARE:
–asplenic
–sickle-cell

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27
Q

Salmonella carrier state

A

-Lives in the gall bladder after infection has cleared elsewhere
-Can shed organisms continuously or intermittently
-Abx or gall bladder removal

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28
Q

Abx for Salmonella

A

Cipro
Ceftriaxone
SXT

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29
Q

Yersinia enterocolitica

A

-Motile at 25C but not 35C
-GNCB w/ bipolar staining
-NLF
-Optimal growth temp of 25-30C
-Grows in the cold / RT so refrigerating food doesn’t slow it down
-Diarrhea
-Fecal-oral route; animal host (milk, water contaminated by pig feces)
-

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30
Q

Y. enterocolitica disease

A

-Fever
-Diarrhea
-Abdominal pain
-Mucosal ulceration in terminal illeum
-Can lead to acute mesenteric lymphadenitis (looks like appendicitis)
-Bacteremia (uncommon)
-Arthritis
-Erythema nodosum

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31
Q

Y enterocolitica virulence

A

1) Invasion via intestinal cell wall and then into lymph nodes
2) Enterotoxin similar to ST of E coli

32
Q

CIN Agar

A

-For Yersinia
-Cefsulodin, Irgasan, Novobiocin, Bile Salts, Crystal Violet, Mannitol
-Inhibits natural colon flora
-Mannitol turns center of colony red while the rest of the colony remains translucent

33
Q

Yersinia pseudotuberculosis

A

-Rare human infections
-Primarily rodent pathogen (guinea pig)
-Birds are natural hosts
-Septicemia, mesentertic lymphadenitis,
-Motile at 18-22C
-Urease+

34
Q

Yersinia pestis

A

-Rodent disease -> flea bites
-Bubonic and pneumonic plague
-2-5 days after infection
-High fever, painful regional lymph nodes (buboes)
-Organisms move to blood stream and respiratory tract

35
Q

Y pestis characteristics

A

1) Short, plump GNCB
2) W/ methylene blue -> intense staining at ends (bipolar, safety pin)
3) Happiest at 25-30C

36
Q

Klebsiella

A

-Nonmotile
-K. pneumo has capsule
-Pneumonia, UTI, bacteremia
-K. oxy indole+
-K. pneumo rhinoscleromatis - nasal cavity infection
–swelling and malformation of face
-MR=
-VP+
-Simmons citrate+

37
Q

Enterobacter

A

-Motile
-MR=
-VP+
-Ornithine decarboxylase+

38
Q

Serratia

A

-Opportunistic pathogens - Nosocomial outbreaks
-Slow lactose fermenters
-ONPG+
-Extracellular DNAase+
-Resistant to a bunch of abx

39
Q

Proteus

A

-Opportunistic
-Can deaminate phenylalanine
-H2S+
-3% of all nosocomial infections
-UTIs, kidney infection, acute glomerulonephritis
-Swarm due to regulated cycle of vegetative cells to hyperflagellated polyploid cells
-P mirabilis indole= / P vulgaris indole+

40
Q

Citrobacter

A

-Lac+
-Slow urease+
-MR+
-Diarrhea but role not fully established
-C. freundii - UTI, pneumonia, inter-abdominal abscess, endocarditis in drug users
–H2S+ / 50% lac= so can be confused w/ Salmonella
–use urease (+) and lysine decarboxylase (=) to differentiate

41
Q

Enteric Agars- MAC

A

-Lactose
-Bile salts

42
Q

Enteric Agars - EMB

A
43
Q

Enteric Agars - S/S

A
44
Q

Enteric ID Test - TSI

A

-Triple Sugar Iron
-0.1% Glucose
-1% Lactose
-1% Sucrose
-Ferrous sulfate / sodium thiosulfate to detect H2S
-Phenol red

-Poured on a slant
–Slant = aerobic
–Butt = anaerobic
–S/B

Glucose ferm / Lac/suc nonferm: K/A
Lactose ferm: A/A
Nonfermenter: K/K (use peptones but don’t ferment)

45
Q

ONPG

A

-Detects if an organisms is a true NLF or a delayed LF
-dLF has B-galactosidase but not B-galactoside permease

46
Q

Methyl Red (MR)

A

-Detects end products of glucose fermentation
-Broth contains glucose
-Incubate 3-5 days
-Add MR -> + if red

Glucose->Pyruvic Acid->Mixed Acid Fermentation->+

47
Q

Voges-Proskauer (VP)

A

-Use broth from MR BEFORE MR addition
-alpha-naphthol then 40% KOH or NaOH->+ if red
Glucose->Pyruvic Acid->Acetoin->Diacetyl+KOH+alpha-naphthol->+

48
Q

Decarboxylase

A

-Tests for decarboxylating enzymes from specific amino acids
-Lysine
-Ornithine

49
Q

Deaminase

A

-Tests for removing NH2 group
-Phenylalanine deaminase test (PAD)
-Useful in differentiating Proteus, Morganella, and Providencia (+) from rest of Enterobacteriacea (=)

50
Q

Citrate utilization

A

-Use sodium citrate as a sole carbon source
-Medium contains ammonium salts for nitrogen
-Bromophenol blue

51
Q

DNAase

A

-Medium containing 0.2% DNA then add 1N HCl
-Unhydrolized DNA is insoluble -> precipitate

52
Q

Enteric ID chart

A
53
Q

Campylobacter characteristics

A

1) Microaerophilic (5% O2)
2) Ox+
3) Grows optimally at 42C
4) Slender curved GNR (seagull)
5) Motile (darting motility)
6) Cat+
7) H2S =
8) Moist pink runny colonies
9) C. jejuni = hipp+

54
Q

Campylobacter virulence

A

1) H antigen (flagella)
2) Enterotoxin
–similar to LT of cholera and Ecoli
3) Cytotoxin
–Destroys mucosal cells

Spread by direct contact with animals or the consumption of contaminated food and water

55
Q

Campy. jejuni

A

-Most common cause of gastroenteritis worldwide
-Mild abdominal pain followed by diarrhea 2-10 days after exposure
-Cramps and bloody diarrhea follow
-Fever, chills, sometimes nausea and vomiting
-Self-limiting -> resolves in 2-6 days
-Can have carrier state
-May play a role in Guillain-Barre syndrome
-Can cause bacteremia or endocarditis

56
Q

Campy media

A

1) CAMPY blood agar plate
–Brucella agar
–10% sheep blood
–Vanc, Trimeth, Polymyxin B, Amphotericin B, Cephalothin
2) Skirrow’s
–Oxoid blood agar
–Lysed, defibrinated horse blood
–Vanc, Trimeth, Polymyxin B
3) Butzler
–Thio w/ agar
–10% sheep blood
–Bacitracin, Novobioncin, Actidione, Colistin, Cefazolin
4) CCDA
–Nutrient agar
-Charcoal
–Sodium deoxycholate
–Cefoperazone, Amphotericin B

57
Q

Campy incubation conditions

A

-5% O2, 10% CO2, 85% N2
-42C

58
Q

Helicobacter

A

-Curved
-Microaerophilic
-Grows at 42C
-GNR
-Urease+
-Motile
-Cat+
-No H2S
-Distinguish between Helicobacter & Campy by:
–Hipp=
–Cephalothin S
–Nalidixic Acid R

59
Q

Helicobacter pylori

A

-Most common cause of duodenal ulcers
-Chronic gastritis
-Gastric cancer
-No toxins
-Urease breath bag test
-Urease biopsy test
-Treat with
–Bismuth
–ampicillin
–metronidazole
–tetracycline

60
Q

Other Helicobacter

A

H. cinaedi / H. fennelliae
–proctitis, enteritis, sepsis in homosexual men
H. cinaedi
–septicemia / meningitis in neonates

61
Q

Helicobacter detection

A

1) Biopsy
–Gram stain / add basic fuchsin
–urease+
–urea breath test
2) Culture
–H. cinaedi / H. fennellia -> campy-CUA w/o cephalothin
–H. pylori -> biopsy
—-Skirrows or MTM
—-Columbia agar / egg yolk agar
—-incubate 1 week
—-small, translucent, circular colonies

62
Q

Vibrio

A

-Water >20C
-Four main infectious species
-Small, straight GNR but can be curved / pleomorphic
–add 1:10 carbolfuchsin for best stain
-Polar flagella in broth / peritrichous on solid media
-Facultative anaerobe
-Reduce nitrate
-Positive string test (0.5% sodium desoxycholate
-Halophilic except V. cholerae / V. mimicus

63
Q

V cholerae disease

A

-Cholera
-Acute diarrhea
-“rice-water” stools
–10-30 stools per day with flecks of mucus
-Epidemic strains are O1 and El Tor

64
Q

Cholera toxin

A

1) aka Choleragen
-A and B subunit
-B binds to GM-ganglioside receptor on cell membrane
-A2 subunit facilitates entrance of A1 subunit
-A1 stimulates G protein -> increase cAMP
-Hypersecretion of electrolytes (Na+, K+, HCO3-) and water out of cells and into intestines

65
Q

V cholerae culture and diagnosis

A

1) Alkaline peptone broth (pH 8.4)
2) TCBS (thiosulfate citrate bile salt) agar
–Yellow if sucrose fermenting (Cholera is yellow)
–may turn green after prolonged incubation if El Tor
3) O/129 Vibriostatic agent S
4) Polyvalent serum
–agglutination+
5) Cholera red test

66
Q

Vibrio cholera differential tests

A

1) String test: Cholera+ / Aeromonas =
2) Inositol: Cholera= / Plesiomonas+
3) Oxidase: Cholera+ / Enterobacteriacae=
4) Fermentation: Cholera+ / Pseudomonas=

67
Q

Vibrio parahaemolyticus

A

-Gastroenteritis
–watery diarrhea, moderate cramps, vomiting
–24-48 hours after ingestion then self-limiting
–Occasional wound isolation
-Summer diarrhea in Japan
-Improperly cooked fish / shellfish
-Halophilic (3-7% NaCl)
-Growth on
–XLD
–TCBS
–Alkaline peptone broth

68
Q

V. parahaemolyticus virulence

A

1) H antigen (motile)
2) Capsule
3) Heat-stabile hemolysin that works in high-salt mediums
–Kanagawa phenomenon / toxin

69
Q

V. vulnificus

A

-Primary septicemia
–starts with ingestion -> goes systemic
–liver dysfunction are most prone
–40-60% mortality
-Wound infections
–traumatic aquatic wound
–cellulitis -> necrotizing fasciitis -> multiple organ system failure

70
Q

V. alginolyticus

A

-Least pathogenic

71
Q

Aeromonas

A

-Ox+
-Glu+/Lac+ (Pink on MAC!!)
-Beta-hemo on BAP
-Indole+
-Water-> found in produce and animal meat products
-Motile

72
Q

Aeromonas disease

A

GI disease (usually A caviae)
1) Acute diarrhea / vomiting
2) Dysentery
3) Chronic diarrhea
4) Cholera-like diarrhea
5) Traveler’s diarrhea

Extraintenstinal infection (usually A. hydrophila)
–aquatic trauma
1) Osteomyelitis
2) Pelvic abscesses
3) Otitis
4) Endocarditis

73
Q

Plesiomonas

A

-Soil and water
–undercooked seafood
-Does not like NaCl
-Diarrhea, fever, vomiting
-Wounds in vets, others who handle animals

74
Q

Plesiomonas characteristics

A

-Motile
-GNR in single, pairs, or short chains
-Ox+
-Grows on most media
-Nonhemolytic
-may not grow on MAC; does not grow on TCBS
-AmpS

75
Q

E. tarda

A

-Urea=
-LDC+
-H2S+
-Indole+
-Citrate=

76
Q

Providencia

A

-Indole+
-MR+
-VP=
-Urea+/=

HCLD Micro (13 decks)

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