Enterobacteriaceae Flashcards
What are the true pathogens?
Salmonella
Shigella
Yersinia
Pathogenic E. coli
SSYE
Serological characteristics - antigens for Enterobacteriaceae
O (somatic) - heat stable on cell wall
H (flagellar) - heat labile on surface of flagella
K (capsular) - heat labile polysaccharide
Associated with Salmonella enterica serotype Typhi
What are the H2S (+) organisms?
Salmonella
Edwardsiella
Citrobacter +/-
Proteus +/-
Edward Puts Citrus on Salmon
Or SPEC
VP (+) species
Klebsiella
Enterobacter
Serratia
KES
Phenylalanine deamination (+) species
Proteus
Morganella
Providencia
PMP
Urease (+) species
Proteus
Morganella
Providencia
Yersinia enterocolitica
Yersinia pseudotuberculosis
Klebsiella
PMPYK
Non-motile species
Shigella
Klebsiella
Y. pestis
SKY (non-motile cannot touch the SKY)
Y. pestis
Bubonic plague
Fleas
Fried egg colonies
Lacks O antigen
Non-motile
Urease negative
- Think pests = fleas, eating eggs
Which organisms are A/A on TSI?
E. coli, Enterobacter, Klebsiella
Proteus vulgaris, arizonae
Lactose fermenters
Citrobacter
E. coli
Enterobacter
Klebsiella
CEEK
Late lactose fermenters
Shigella sonnei
Citrobacter
Oxidase (+) Enterobacteriaceae
Plesiomonas shigelloides
What does SMAC agar isolate?
E. coli 0157:H7
What color colonies is E. coli O157:H7 on SMAC?
Colorless
Does not ferment sorbitol (it would be pink)
What does CIN agar isolate?
Yersinia enterocolitica
What does Yersinia enterocolitica look like on CIN agar?
Bulls eye
What does Aeromonas look like on CIN11 agar?
Pink colonies, smooth, different edges, NOT bullseye like Yersinia enterocolitica
What color does a lactose fermenter look like on XLD?
Yellow (normally red agar)
What color do lactose fermenters look like on MAC?
Pink
What color do lactose fermenters look like on HE?
Orange (normally blueish green agar)
Virulence factors of Uropathogenic E. coli (UPEC)?
Primary: pili (adherence to epithelial cells to prevent flushing away)
Cytolysins: kill immune effector cells, inhibit phagocytosis so WBCs don’t go to site of infection
Aerobactin: binds iron to allow it to grow
4 toxins of Escherichia sp
Alpha-hemolysin
Shiga toxin
Labile toxin (LT)
Stable toxin (ST)
What are the 5 categories of diarrheagenic E. coli?
EnteroTOXIGENIC
EnteroINVASIVE
EnteroPATHOGENIC
EnteroHEMORRHAGIC (O157:H7)
EnteroADHERERENT
TIPHA
Enterotoxigenic E. coli (ETEC)
- In tropical areas
- Traveler’s diarrhea
- Self limiting
- Transmission: fecal/oral
- Produce LT & ST toxins
- Symptoms: watery diarrhea, nausea, abdominal cramps
Enteroinvasive E. coli (EIEC)
- Rare in US
- Dysentery (inflammation of intestines with bloody diarrhea)
- Fever, abdominal cramps, malaise, watery diarrhea
- Similar to Shigella but infectious dose is higher (not as infectious)
- Can appear as non-pathogenic E. coli (can be non-motile and lactose neg)
Enteropathogenic E. coli (EPEC)
- Infant diarrhea: associated with daycare and nurseries
- Low grade fever, malaise, mucousy stools, v/d
- Fimbriae adhesive qualities
- Transmission: fecal/oral, fomites
Enterohemorrhagic E. coli (EHEC)
E. coli O157:H7
- Processed meat, unpasteurized dairy, etc.
- HUS (damaged small blood vessels, clots)
- Absence of leukocytes
- Low or no fever
- Often fatal, especially in immunocompromised
- Watery diarrhea
2 cytotoxins:
- Verotoxin I (Shiga like toxin - Stx1)
- Verotoxin II (Stx2)
How to identify EHEC?
SMAC (-)
MUG (-)
Enteroadherent E. coli (EAEC)
Stacked brick appearance
- Watery diarrhea, vomiting, dehydration, abdominal pain
- 2+ weeks
- WBC & RBC absent from stools
- Infants in US and HIV patients
Shigella subgroups
S. dysenteriae
S. flexneri
S. boydii
S. sonnei
Transmission of Shigella
- Fecal/oral
- Direct contact
- 5 F’s: fingers, fomites, fecal, food, flies)
Most contagious (lowest infective dose)
Shigella
1-100 organisms for an infective dose
Shigella dysenteriae vs E. coli O157:H7
O157:H7 - no leukocytes in stools
Habitat of S. enterica subsp. enterica
Warm-blooded animals and humans
S. flexneri
3rd world nations
Reiter’s chronic arthritis syndrome
S. sonnei
- Predominantly in USA
- Gastroenteritis in men being with other men
- Self limiting, fever, watery diarrhea, typically asymptomatic
ONPG and ODC (+) — remember late lactose fermenter
Salmonella Typhoid Fever
- Tropical disease
- Transmission: fecal/oral, direct contact, fomites
- Symptoms: 9-14 days after ingestion, malaise, anorexia, myalgia/muscle pain, headache, fever, bacteremia, dissemination to multiple organs
- Isolated from blood (blood culture positive)
Non-typhoidal Salmonella
- Young children: bacteremia, fever
- Adults: septicemia, septic arthritis
Y. pseudotuberculosis
Close contact with animals and contaminated food
Y. enterocolitica
Undercooked meat, contaminated milk, transfusion
Bullseye on CIN
Urease (+)
Non-motile at 35 C
Y. pestis vs other Yersinia
- Non-motile
- Urease negative
3 forms of plague
- Pneumonic - bacteria inhaled, lungs
- Bubonic - fleas
- Septicemic - pneumonic and bubonic turn into this, manifests in the whole body
Edwardsiella tarda
Gastroenteritis, wound infections, bacteremia in immunocompromised patients
K/A
Indole (+) vs salmonella indole (-)
iMViC ++–
Citrobacter sp
GI tract, UTI
Cause healthcare associated infections (HAI)
C. freundii
UTIs, pneumonia, endocarditis
Similar to Salmonella - ONPG and Citrate (+) compared to Salmonella paratyphi A
iMViC -+-+
C. koseri
Neonatal meningitis, brain abscesses
iMViC ++-+
Klebsiella pneumoniae vs Klebsiella oxytoca
Pneumoniae = Indole (-)
Oxytoca = Indole (+)
Klebsiella pneumoniae
Normal flora in GI tract, nasopharynx
- Pneumonia, wound infections, UTI, bacteremia
- Pyrogenic liver abscess
Hyper-mucoid colonies
iMViC - - ++
Morganella vs Providencia
Morganella: Citrate (-), ODC (+)
Providencia: Citrate (+), ODC (-)
Proteus mirabilis vs Proteus vulgaris
P. mirabilis: ODC (+), Indole (-), K/A H2S+
P. vulgaris: ODC (-), Indole (+), A/A H2S+
- Remember P. vulgaris on iMViC chart, indole (+). Then, ODC is the opposite
- P. mirabilis and Morganella are both ODC (+)
Proteus sp
Urease (+), can cause calculi (hard deposited of minerals and salts in the kidneys) in P. mirabilis
UTI
Serratia marcescens
- Nosocomial (originates in the hospital)
- Cystitis, pneumonia, bacteremia, septic arthritis, osteomyelitis
- DNase (+)
iMViC - - ++
Red pigment on plate!
Enterobacter sp
iMViC - - ++
Isolated in wounds, urine, blood, CSF
Mucoid colonies like Klebsiella
What are the 3 organisms that are iMViC ++- -?
E. coli
Edwardsiella tarda
Proteus vulgaris
EEP
What are the 3 organisms that are iMViC - - ++?
Klebsiella pneumoniae
Enterobacter sp
Serratia marcescens
KES
Y. pseudotuberculosis vs Y. enterocolitica
Pseudotuberculosis - motile at 25 C
Enterocolitica - NON-motile at 35 C
Enterobacter vs Serratia
Serratia = DNase (+)
Enterobacter = DNase (-)
Salmonella vs E. tarda
Salmonella = Indole (-)
E. tarda = Indole (+)
- iMViC for E. tarda
C. freundii vs S. paratyphi A
C. freundii = ONPG (+)
S. Paratyphi A = ONPG (-)
What are the differences between Pseudominas aeruginosa vs. P. putida and P. fluorescens vs. P. stutzeri and P. oryzihatibans?
P. aeroginosa: grows at 42 C, pyocyanin (blue-green pigment)
P. putida, P. fluorescens: Grows at 4 C, produces pyoverdin (yellow green or yellow brown pigment), fluorescent under UV. Produces acid from a xylose
P. stutzeri, P. oryzihatibans: no fluorescent pigments
P. stutzeri has wrinkly colonies
Grows at 42 C
How to differentiate P. stutzeri?
Leathery wrinkled colonies with yellow pigment
P. putida vs P. fluorescens
Gelatin hydrolysis
P. fluorescens (+)
P. putida (-)
P. aeroginosa on SBA
- Flat with serrated edges
- beta hemolytic
- grape or tortilla odor
- mucoid when from a CF patient
What are the 2 LDC (+) nonfermenters?
Burkholderia and Stenotrophomas
Difference between Burkholderia and Stenotrophomonas?
DNase
Burkholderia = DNase (-)
Stenotrophomonas = DNase (+)
Where is Burkholderia cepacia found in?
In the environment (soil, stream, water. Can be a plant pathogen
What is the difference between Citrobacter koseri and Citrobacter freundii?
C. koseri: iMViC ++-+
C. freundii: iMViC -+-+
What are the two LDC (+) non fermenters?
Burkholderia and Stenotrophomonas
How do you differentiate Burkholderia and Stenotrophomonas?
DNase
Burkholderia (-)
Stenotrophomonas (+)
Burkholderia pseudomallei
Found in soil, stream, rice paddies in other parts of the world
Affects lungs (meliodosis) and sacs that form tears
Bioterrorism agent
Smooth and mucoid to dry and wrinkled on SBA
Essential oil spray at Walmart, essential oil from India - first case in US
What media is used to differentiate sucrose fermenting Vibrios with non sucrose fermenting?
TCBS - thiosulfate citrate bile salts
V. cholerae = yellow colonies since it ferments sucrose
Other Vibrios = green colonies since it doesn’t ferment sucrose
Which organism is associated with Trench fever?
Bartonella quintana
Cat scratch disease
Bartonella henselae
Tularemia (rabbit fever)
Francisella tularensis
Capnocytophaga
Cat no
From cat and dog bites
Spindle shaped, thin on both ends (think of cat nails)
C. canimorsus may cause amputation of leg/arm
Penicillin
Aerobic organisms
PPBBSAA
Pseudomonas aeroginosa
Pseudominas stutzeri
Burkholderia cepacia
Burkholderia pseudomallei
Stenotrophomonas maltophilia
Acetinobacter baumanii
Alcaligenes
Stomach ulcers and strong urease activity
Helicobacter
Urea breath test
What is BYCE media used for?
Legionella
What 3 ingredients in BCYE are specific for Legionella?
L-cysteine HCl
Ferric pyrophosphate
Alpha-ketoglutarate
Which non-Enterobacteriaceae are oxidase negative?
Stenotrophomonas and Acinetobacter
What is the disease for H. aegypticus?
Conjunctivitis/pink eye
What is the disease for H. ducreyi?
Genital ulcer disease
Bleach odor
Haemophilis influenzae
Eikenella
