Enterobacteriaceae (3 tests: blood agar, McConkey's agar, EMB)

Question 1

E. coli

Answer 1

” Heat Labile (diarrhea) & Stabile (vomiting) Enterotoxin E.coli. Some make toxin similar to cholera.
Virulence factors: fimbriae- cystitis & pyelonephritis, K1-capsule - pneumonia & neonatal meningitis. LPS endotoxin - septic shock.
Lactose (+) fermentation.”

“EIEC: Invades intestinal mucosa. Necrosis & inflammation. No toxins. Clinically similar to shigella. ““Invasive””, causes dysentery.
ETEC: Labile and Stabile toxin. No inflammation or invasion. ““Travelor’s”” diarrhea.
EPEC: No toxin. Adheres to apical surface. Flattens villi. prevents absorption. ““Pediatrics””
EHEC: E. coli 0157:H7 is most common serotype. Shiga-like toxin. hemolytic uremic syndrome (HUS). Anemia, thrombocytopenia, acute renal failure. Endothelium swells and narrows the lumen leading to mechanical hemolysis and reduced renal bloodflow. Damaged endothilium consumes platelets. Dysentery (toxin- alone causes necrosis and inflammation). Does not ferment sorbitol.
#1 cause of UTI.
Cystitis (bladder infection). K1=neonatal meningitis.”

Question 2

Salmonella sp.

Answer 2

Flagella. Produces H2S. NO lactose fermentation.

Disseminates hematogeneously. Many animal reservoirs). Antibiotics may prolong symptoms. Invadesintestinal mucosa. Causes monocytic response. Can cause bloody diarrhea.

Question 3

Salmonella typhi

Answer 3

No lactose fermentation, produces H2S

Gall bladder colonization (can remain in gall bladder and cause carrier state). Typhoid fever. Human only. Rose spots on abdomen. Fever. Headache. Diarrhea. Grows inside macrophages.

Question 4

Salmonella enteritidis

Answer 4

No lactose fermentation. Produces H2S

Osteomyelitis in people with sickle cell trait. Eggs. Reptiles. Fecal-oral. Chickens. Non-human reservoir. Outbreaks. Gastroenteritis.

Question 5

Shigella

Answer 5

No flagella (immotile). Shiga toxin. Cell-to-cell transmission (not hematogeneously). Human & primate only reservoir. No H2S production. No lactose fermentation.

Dysentery (bloody diarrhea). Human pathogen. Antibiotics prolong excretion of organism in feces. Invades intestinal mucosa & causes PMN infiltration.

Question 6

Klebsiella pneumoniae

Answer 6

Mucoid colonies by the abundant polysaccharide capsule. Lactose (+). Non-motile.

“4 A’s: Aspiration pneumonia, abscess in lungs & liver, alcoholics, diAbetics.
Intestinal flora causes lobar pneumonia in alcoholics & diabetics when aspirated.
Red ““currant jelly”” sputum. UTI. wound infections”

Question 7

Enterobacter

Answer 7

Lactose (+)

Similar to Klebsiella. UTI, Pneumonia, Sepsis. Wound infection

Question 8

Serratia

Answer 8

Lactose (+), Forms Red colonies.

Similar to Klebsiella. UTI, Pneumonia, Sepsis. Wound infection. Nosocomial. Moist, wet environments. Soil in hospital plants.

Question 9

Proteus

Answer 9

Urease +. Swarming motility.

Kidney stones (stag-horn). UTI

Question 10

Morganella

Answer 10

Urease +

Kidney stones. UTI

Question 11

Providencia

Answer 11

Urease +

Kidney stones. UTI