Enterobacterales - glucose fermenters Flashcards
Name the clinically significant Enterobacterales (7)
Most common
LF
E. coli
Klebsiella
Citrobacter
Enterobacter
NLF
Proteus
Morganella*
Providencia*
Serratia
Name the Enterobacterales that are less common (8)
Citrobacter
Salmonella
Shigella
Yersenia
Cronobacter
Plesiomonas
Providencia rustigianii
Edwardsiella
What biochemical test is used to verify MALDI results for Gram negatives?
Oxidase
Enterobacterales are oxidase negative
Used to distinguish from Pseudomonas (oxidase positive)
What are 4 characteristics of Enterobacterales?
- reduce nitrate to nitrite (UTI test-urinalysis)
- Glucose fermenters (red -> yellow sugar slant)
- Oxidase negative
- Grow on MAC
- Exception of oxidase positve: Plesiomonas shigelloides, Franconibacter, and Siccibacter
pH indicator of MAC plate?
Neutral red
pH 4 = red (fermentation)
pH 9 = yellow
pH indicator of glucose slant?
Phenol red
pH 4 = yellow (fermentation)
pH 9 = red
Name 3 Enterobacterales that ferment lactose
E. coli
Klebsiell pneumoniae
Enterobacter
To a lesser degree:
Citrobacter freundii
Name 4 Enterobacterales that DO NOT ferment lactose
Salmonella
Shigella
Proteus
Serratia
E. coli biochemicals
Oxidase negative
Strong lactose fermentation
motile
Indole +
Can MALDI distinguish E. coli from Shigella?
NOPE
Can perform indole and motility tests
E. coli positive for both
Shigella negative for both
Can also distinguish on MAC
Name 7 diseases associated with E. coli
1) Urinary tract infection
2) Gastrointestinal disease - Shiga toxin may have complications (HUS)
3) Skin and surgical site infections
4) Ventilator associated Pneumonia - #3 organism
5) Line infections
6) Sepsis (dysregulation of host response)
7) Neonatal meningitis (#2, first is GBS) transmitted vertically
Uncomplicated cystitis
bladder infection only
pain during urination, pelvic discomfort, blood may be present
Complicated cystitis
Bladder infection with concern for disseminated infection
Fever, chills, flank pain, plus cystitis symptoms
pyelonephritis
Infections of the kidneys
Nausea, vomiting, Fever, chills, flank pain, plus cystitis symptoms
How are UTIs diagnosed?
1) dipstick (nitrate reduced to nitrites) (false negatives become some UTI organisms don’t reduce nitrate)
name them
2) WBC in urine observed under microscope
3) Quantitative culture on MAC (loop used depends on specimen source)
1uL loop = 1 colony = 1000 CFU
10uL loop = 1 colony = 100 CFU
How are GI diseases caused by E. coli transmitted and treated?
Contaminated food or water
Diarrhea, vomiting, fatigue, loss of appetite
Antibiotics are NOT administered to prevent toxin release
(this can lead to Hemolytic Uremic Syndrome)
It’s important to identify which E. coli strain to prevent Hemolytic Uremic Syndrome?
And how it is detected?
E. coli O157:H7” is a specific strain of bacteria, “EHEC” that produces Shiga toxin. It is called shiga toxin producing E. coli instead of EHEC. STX1/stx2
Identification can be done based on LACK OF SORBITOL FERMENTATION
Detected Shiga toxin in stool by Enzyme immunoassays (EIA) after bacteria is grown in Vero cells (THIS IS NOT DONE IN THE LAB)
Biofire panel detects shiga toxin 1 and 2. At CHOP these are detected in the GI bacterial panel!!
Hemolytic uremic syndrome (HUS) is very serious complication of Shiga toxin-producing E. coli (STEC) infection.
It can lead to kidney failure, permanent health problems, and even death.
Key characteristics of Klebsiella pneumoniae
Large mucoid colinies
Lactose fermenter
Indole negative
Oxidase negative
Intrinsically resistant to ampicillin
Klebsiella oxytoca
indole positive
Klebsiella aerogenes
“Enterobacter aerogenes”
Lactose fermenter
Indole negative
Oxidase negative
Intrinsic resistance to:
ampicillin + sulbactam
1st gen cephalosporin (cefazolin)
and 3rd gen cephalosporins
AmpC beta Lactamase
Rare Klebsiella species (2)
K. rhinoscleromatis - granulomatous (phagocytes don’t function properly) disease of the respiratory tract. Found in tropical regions. Only diagnosed by pathology
K. granulomatis (sexually transmitted genital ulcers) found in tropical regions
