Enterobacteriaceae I Flashcards
Enterobacteriaceae
Gram Oxygen use Shape Motility Oxidase Nitrate reduction
Gram (-) Facultative anaerobe Rod-shaped Motile (most) Oxidase (-) Nitrate --> Nitrite reduction
Natural habitat of enterobacteriaceae
lower GI tract
Colonization sites of enterobacteriaceae
What types of patients are at risk for infection?
Oral mucosa, respiratory tract, urinary tract
Hospitalized patients
What tests do you run to differentiate enterobacteriaceae?
Oxidase and nitrate reduction
What selective agar can you use to grow enterobacteriaceae on? What special ingredients does it contain? What does it suppress growth of?
MacConkey agar - contains lactose, pH indicator, bile salts
Suppresses growth of Gram +, Neisseria, and Haemophilus
What color will Gram (-) lactose + organism be on MacConkey agar?
Pink/red
What color will Gram (-) lactose (-) organism be on MacConkey agar?
Yellow
What color will Gram (+) lactose (+) organism be on MacConkey agar?
No growth! - Gram + can’t grow on MacConkey b/c of bile salts
Protein surface antigens on enterobacteriaceae
- Flagella-H antigen (motility)
- Fimbriae
Polysaccharide surface antigens on enterobacteriaceae
- Capsule K
- O antigen
Functions of capsule of enterobacteriaceae
- Defense (shielding, complement, camouflage)
- Resistance to drying
- Biofilm formation
Sidereophores
Small, high-affinity iron-binding compounds that scavenge iron away from high-affinity iron-binding proteins in host
What organism caused a nosocomial blood stream infection outbreak due to IV magnesium sulfate as well as pre-filled heparin syringes?
Serratia marcescens
What organism caused a febrile diarrhea outbreak liked to institutional brand peanut butter?
Salmonella typhimurium
What are the distinct components of bacterial endotoxin/LPS?
- Lipid A
- KDO or core - negative charge so repels negative charges
- O polysaccharide - shields like a capsule
