Entererics Flashcards
Carbapenem-resistant Enterobacterales (CRE)
- Enterobacterales are a large order of different types of germs (bacteria) that commonly cause infections in healthcare settings. Examples of germs in the Enterobacterales order include Escherichia coli (E. coli) and Klebsiella pneumoniae.
- Antibiotic resistance occurs when the germs no longer respond to the antibiotics designed to kill them. Enterobacterales bacteria are constantly finding new ways to avoid the effects of the antibiotics used to treat the infections they cause.
- When Enterobacterales develop resistance to the group of antibiotics called carbapenems, the germs are called carbapenem-resistant Enterobacterales (CRE).
- CRE are difficult to treat because they do not respond to commonly used antibiotics. Occasionally CRE are resistant to all available antibiotics. CRE are a threat to public health.
Enterobacteriaceae
- Klebsiella,
- Enterobacter
- Citrobacter
- Salmonella
- Escherichia coli
- Shigella
- Proteus
- Serratia
- other species.
Salmonella Clinical Significance
-Salmonellosis ranges clinically from the common Salmonella gastroenteritis (diarrhea, abdominal cramps, and fever) to enteric fevers (including typhoid fever) which are life-threatening febrile systemic illness requiring prompt antibiotic therapy. Focal infections and an asymptomatic carrier state occur.
Salmonella Structure, Classification, and Antigenic Types
-Salmonella species are Gram-negative, flagellated facultatively anaerobic bacilli characterized by O, H, and Vi antigens. There are over 1800 known serovars which current classification considers to be separate species.
E. coli Clinical Significance
- Most E. coli are harmless and actually are an important part of a healthy human intestinal tract.
- some E. coli are pathogenic, meaning they can cause illness, either diarrhea or illness outside of the intestinal tract.
- Shiga toxin-producing E. coli (STEC)
- enterohemorrhagic E. coli (EHEC)
- Enterotoxigenic E. coli (ETEC)
- Enteropathogenic E. coli (EPEC)
- Enteroaggregative E. coli (EAEC)
- Enteroinvasive E. coli (EIEC)
- Diffusely adherent E. coli (DAEC)
E. coli Structure, Classification, and Antigenic Types
- Gram-negative bacilli
- family Enterobacteriaceae.
- Virulent strains differ from nonvirulent E coli only in possessing genetic elements for virulence factors. Strains producing enterotoxins are enterotoxigenic E coli (ETEC).
Shigella Clinical Significance
- Shigella, a highly virulent pathogen that causes bacterial dysentery
- Shigellosis is typically an invasive infection of the human colon and rectum with severe inflammation and tissue necrosis.
Shigella Structure, Classification, and Antigenic Types
- Shigellae are Gram-negative
- nonmotile
- facultatively anaerobic
- non-spore-forming rods.
- lysine negative
- Motility negative
- Shigella are differentiated from the closely related Escherichia coli on the basis of pathogenicity
- physiology (failure to ferment lactose or
decarboxylate lysine) and serology.
Shigella Biochem ID
- Non-Lactose Fermenter
- Non-pigmented colonies on MacConkey Agar
- TSI = K/A-
- Non Motile***
- Lysine -***
- Biochemically Inert
- Ornithine Decarboxylate Positive
- Shigella Sonnei Positive
Citrobacter Species Presumptive ID
- Smooth, convex, mucoid colonies on blood agar
- KIA: A/A GAS
- Citrate Positive
- Lysine Negative
Citrobacter Species Presumptive ID
- Smooth, convex, mucoid colonies on blood agar
- KIA: A/A GAS
- Citrate Positive
- Lysine Negative
- H2S Positive
- -indole negative
- -Ornithine Negative
- -Citrobacter freundii
- H2S Negative
- -Indole Pos
- -Ornithine Pos
- -Citrobact koseri
Serratia Marcescens Presumptive ID
-grey entire colonies on blood agar
-Non-lactose fermentation on MacConkey agar
-Distinctive red-pigmented colonies on MAC
-DNA’se = +
-Lipase = +
Gelatinase = +
-Confirmatory Tests
–Ornithine
–Citrate
–VP
–Gelatin
E. Coli Presumptive ID
- grey, beta-hemolytic colonies on BA
- Short Gram-Neg Bacilli
- Lactose Fermentation on MAC
- spot Indole POS
- 0157 sorbitol NEG
- MR POS
- VP NEG
- DNAse, H2S, Urease, Phenylalnine deaminase Neg
- Citrate Neg
Klebsiella Presumptive ID
- smooth convex mucoid colonies on blood agar
- lactose fermentation on MAC
- Indole Negative
- Urease, Citrate, VP POS
–Klebsiella pneumoniae
Shigella Species
- dysenteriae Group A
- flexneri Group B
- boydii Group C
- sonnei Group D