Enterobacteriaceae - Microbiology

Snapshot
- A 27-year-old man presents to the urgent care clinic for diarrhea. His symptoms began approximately 2 days ago. His symptoms are associated with abdominal pain, malaise, and fatigue. He denies the presence of blood or pus in the stool. He states he returned to the United States 1 week ago from his trip to Ecuador. Physical examination is notable for mild abdominal tenderness upon palpation but there is no appreciable hepatosplenomegaly or skin changes. He is recommended symptomatic treatment. (Traveler's diarrhea by ETEC)

Introduction
- Classification
  - gram-negative bacteria
    
    Escherichia coli
    
    Klebsiella
    
    Proteus mirabilis
    
    Enterobacter
    
    Serratia
    
    Shigella
    
    Salmonella

                        Enterobacteriaceae
                    
                        Enterobacteriaceae
Organism
Microbiology
Associated ConditionsTreatment
E. coliReservoirgastrointestinal and urinary tract
Transmissionfecal-oral
urethral ascension
catheter
aspiration
Labslactose fermenting
β-hemolytic
Propertiesenterotoxinsheat labile, which increases cAMP
heat stable, which increases cGMP
fimbriae
K-antigen (capsule)
H-antigen (flagella)
Diarrheaenterotoxigenic (ETEC)causes traveler's diarrhea, which is a watery diarrhea
enterohemorrhagic (EHEC)causes bloody diarrhea
secretes Shiga-like toxin, which can lead tohemorrhagic colitis
hemolytic uremic syndromeassociated withE. coli O157:H7
enteroinvasive (EIEC)causes bloody diarrhea (with pus and fever)
Newborn meningitisirritability
bulging fontanelle
Urinary tract infection (UTI)dysuria, urinary frequency, and urinary urgency
DiarrheaETECsupportive treatment
EHECsupportive treatment
monitoring of hemolytic uremic syndrome, which is also managed with supportive treatment
EIECsupportive
Newborn meningitisampicillin
third-generation cephalosporin with gentamicinin ampicillin-resistant strains
Urinary tract infectionfluoroquinolone, trimethoprim/sulfamethoxazole (TMP-SMX), or nitrofurantoin
K. pneumoniaeLabslactose fermenter
Propertieshas a capsule and is nonmotile
Pneumoniacurrant-jelly sputumtypically seen in patients with underlying lung disease or alcohol use disorder
UTIdysuria, urinary frequency, and urinary urgency
typically hospital-acquired
Typically with a 3rd generation cephalosporin
P. mirabilisLabssplits urea intoNH3 andCO2
indole negative
non-lactose fermenting
Propertiesurease positive
motile
UTIdysuria, urinary frequency, and urinary urgency
urine pH is basic (elevated) due to producing NH3
Sepsis
TMP-SMX
Ampicillin
S. dysenteriaeReservoirhumans
Transmissionfecal-oral
Labsnon-H2S producing
non-lactose fermenting
never a part of the normal intestinal flora
Propertiesnon-motile
invades the small intestine but not the lamina propria
produces Shiga toxinacts on the 60s ribosomal subunit of the intestinal epithelia, impairing protein synthesis and causing intestinal damage
 Diarrheabloody with blood and pus (similar to EHEC)
Fluoroquinolones
Azithromycin
Ceftriaxone
S. typhiReservoirhumans
Transmissionfecal-oral
LabsH2S
non-lactose fermenting
Propertiesmotile
capsulepatients with an absent or non-functioning spleen are at high risk of infection
facultative intracellularcan live in macrophages and in the gallbladder
Typhoid feverfever
hepatosplenomegaly
rose abdominal spots
abdominal pain
Osteomyelitisseen in patients with sickle cell disease
Ceftriaxone
Meropenem
Fluoroquinolone

                        TMP-SMX
                    
                        Ampicillin

Enterobacteriaceae
Organism	Microbiology	Associated Conditions	Treatment
E. coli	Reservoir gastrointestinal and urinary tract Transmission fecal-oral urethral ascension catheter aspiration Labs lactose fermenting β-hemolytic Properties enterotoxins heat labile, which increases cAMP heat stable, which increases cGMP fimbriae K-antigen (capsule) H-antigen (flagella)	Diarrhea enterotoxigenic (ETEC) causes traveler's diarrhea, which is a watery diarrhea enterohemorrhagic (EHEC) causes bloody diarrhea secretes Shiga-like toxin, which can lead to hemorrhagic colitis hemolytic uremic syndrome associated withE. coli O157:H7 enteroinvasive (EIEC) causes bloody diarrhea (with pus and fever) Newborn meningitis irritability bulging fontanelle Urinary tract infection (UTI) dysuria, urinary frequency, and urinary urgency	Diarrhea ETEC supportive treatment EHEC supportive treatment monitoring of hemolytic uremic syndrome, which is also managed with supportive treatment EIEC supportive Newborn meningitis ampicillin third-generation cephalosporin with gentamicin in ampicillin-resistant strains Urinary tract infection fluoroquinolone, trimethoprim/sulfamethoxazole (TMP-SMX), or nitrofurantoin
K. pneumoniae	Labs lactose fermenter Properties has a capsule and is nonmotile	Pneumonia currant-jelly sputum typically seen in patients with underlying lung disease or alcohol use disorder UTI dysuria, urinary frequency, and urinary urgency typically hospital-acquired	Typically with a 3rd generation cephalosporin
P. mirabilis	Labs splits urea intoNH₃ andCO₂ indole negative non-lactose fermenting Properties urease positive motile	UTI dysuria, urinary frequency, and urinary urgency urine pH is basic (elevated) due to producing NH3 Sepsis	TMP-SMX Ampicillin
S. dysenteriae	Reservoir humans Transmission fecal-oral Labs non-H₂S producing non-lactose fermenting never a part of the normal intestinal flora Properties non-motile invades the small intestine but not the lamina propria produces Shiga toxin acts on the 60s ribosomal subunit of the intestinal epithelia, impairing protein synthesis and causing intestinal damage	Diarrhea bloody with blood and pus (similar to EHEC)	Fluoroquinolones Azithromycin Ceftriaxone
S. typhi	Reservoir humans Transmission fecal-oral Labs H₂S non-lactose fermenting Properties motile capsule patients with an absent or non-functioning spleen are at high risk of infection facultative intracellular can live in macrophages and in the gallbladder	Typhoid fever fever hepatosplenomegaly rose abdominal spots abdominal pain Osteomyelitis seen in patients with sickle cell disease	Ceftriaxone Meropenem Fluoroquinolone

Action	Numeric Key	Letter Key	Function Key
Show Bullets		S	Enter (frontside only)
20%	1	N
40%	2	H
60%	3	F	Enter (backside only)
80%	4	E
100%	5	M
Toss	0	T