Chapter 19: Enterobacteriaceae Flashcards
What are the characteristics of klebsiella?
- –contain capsules in order to present the bacteria from phagocytosis
- – normally found in the respiratory tract of humans and animals
- –Non-motile
- – They are Voges-Proskauer positive
What is the colony morphology of klebsiella in MacConkey agar, Blood agar and CHROMagar?
Mucoid colonies after prolonged incubation
CHROMagr- they will appear as denim blue colonies
Blood agar_they will appear as large mucoid colonies
What are the two types of species in klebsiella? And which tests are used to differentiate the two?
Klebsiella oxytoca and klebsiella pneumoniae
INDOLE: Klebsiella oxytoca is positive and Klebsiella pneumonia is negative for indole
UREASE: Is positive for Klebsiella pneumonia
What are the most common diseases caused by klebsiella?
They cause opportunistic infections, they cause pneumonia, septicemia, bacteremia, UTIs, and the liver abscesses
They are inhabitants of the nasopharynx and gastrointestinal tract
Klebsiella pneumonia causes bacteremia, meningitis, wound infections, UTIs
Respiratory Tract infections are very common because of the prominent capsule found in the klebsiella
Nosocomial infections
What are the specimens of choice for klebsiella?
- —Wound swabs
- —Sputum
- —CNS
What are the API tests used for Klebsiella?
Oxidase: Negative ONPG: Positive Indole: K.oxytoca; Positive and K.pneumoniae: negative H2S: Citrate: Positive Simms motility: Negative (immotile) Urease: Positive Voges-Proskauer: Positive
What is the treatment for klebsiella?
Klebsiella have a tendency of acquiring resistant genes like ESBL(extended spectrum beta lactamase) and CRE (carbapenam resistant enterobacteria) which makes it resistant to carbapenam
Klebsiella pneumoniae: They are RESISTANT to ampicillin therefore it will not be effective as a treatment option
How is Serratia transmitted?
They are transmitted through medical devices which are urinary catheters and intravenous fluids. They can transmitted through person-to-person transmission
What are the characteristics of Serratia?
- –They produce prodigisin which is a red pigment used as a differential feature in Serratia marcescens when grown in room temperature
- –They are motile (they are resistant to harsh conditions)
- — Slow lactose fermenters( appear to be NLF on a MacConkey agar but with prolonged incubation because LF)
What are the biochemical tests used to differentiate Serratia from other organisms?
ONPG: Positive
Simms Motility: Positive
DNase; Positive
What are the diseases associated with Serratia?
Nosocomial infections: they can grow on catheters, saline solutions
Serratia can cause life-threatening opportunistic infections in immuno-compromised patient like UTI and respiratory infections
Describe the treatment options for Serratia
Serratia are very difficult to treat because of their resistance to antimicrobial drugs
There will be a reduced Antimicrobial susceptibility test zone and increasing Minimum inhibitory concentrations for carbapenem antibiotics
Briefly describe the characteristics of Enterobacter
Motile
Lactose fermenters
They are nosocomial infections (infections caused by medical devices)’
Indole: Negative
Enterobacter colony morphology are similar to that of klebsiella has mucoid colonies and they have a capsule
What are the biochemical tests for Citrobacter?
NB!!!! All species for Citrobacter will be Citrate POSITIVE!!!!! ONPG: Positive INDOLE: Positive for C.koseri Oxidase: Negative Citrate: Positive Simms Motility: Positive H2S : Positive foe C.freudii
Describe the Characteristics of Proteus
- -They are Non-lactose fermenters
- -They contain phenylalanine deaminase
- -Motile because they contain peritrichous flagella which results in them making a swarming effect on a blood agar
- –“Rotten egg” smell on a blood agar
What are the biochemical tests for Proteus ?
ONPG: Negative
Oxidase: Negative
Simms motility: Positive
**Citrate**: Positive
H2S: Positive
Indole: Positive on P. vulgaris
: Negative on P.mirabilis
Urease: PositiveName the diseases that are caused by proteus
Proteus mirabilis is most commonly associated with human disease
They are normally found in the Gastrointestinal tract and are associated with Urinary tract infections
in patients that use long-term catheters (nosocomial infections) and sometimes are associated with Infection-induced kidney stones
What is the treatment for Proteus?
Proteus are usually resistant to antimicrobial drugs
Briefly describe the appearance of this Proteus on a Blood, MacConkey and CHROMagar
Blood agar: swarming due to the presence of peritrichous flagella
MacConkey agar: Swarming effect based on the amount of agar present
CHROMagar: Brown/tan colonies
Give a reason my some organisms in the Enterobacteriaceae family are called true pathogens
They produce types 3 secretions system:
- -Introduce proteins that inhibit phagocytosis
- they have the ability to rearrange the cytoskeletons of eukaryotic cells
- – they induce apoptosis
What are the Biochemical tests used for Salmonella?
Sal--MM--onela are motile H2S: Positive Lysine: Positive D-Sorbitol: negative Citrate: Negative
What are the Biochemical tests for Shigella?
Shigella is the negative sister therefore anything that is positive for salmonella will be negative for shigella
- -NON MOTILE
- -H2S: Positive
- -Lysine: Positive
- -Citrate Positive
- -D-sorbitol: positive
What are the Biochemical tests for Shigella?
Shigella is the negative sister therefore anything that is positive for salmonella will be positive for shigella
- -NON MOTILE
- -H2S: Positive
- -Lysine: Positive
- -Citrate Positive
- -D-sorbitol: positive
Name the tests that will e the same outcome for both salmonella and shigella
Indole: negative
Urea: Negative
ONPG: Negative because they are both NLF
How is salmonella transmitted? also state the disease that are associated with salmonella
Salmonellosis(causes gastroenteritis) : is transmitted via the fecal oral route from poultry products, eggs, meat and reptiles
Typhoid fever: can only be contracted from a “HUMAN” carrier via the fecal oral route
Name the different species associated with Salmonella and the diseases they cause
S.enteritis and S.typhimurium cause acute gastroenteritis
S.Typhi and Paratyphi causes typhoid fever
What are the different types of antigens associated with salmonella?
- O antigens
- K antigens (capsule)
- H antigens(flagella)
Salmonella typhi has a specific Vi antigen that that is used to detect typhoid fever in certain patients
Explain the pathogenesis of Salmonella
- Salmonella attaches to the epithelial lining of small intestines
- Salmonella will then trigger endocytosis
- Salmonella will then start multiplying within the vessels
- Salmonnela will then kill the host causing fever, cramps and diarrhea
- Salmonella then moves into the bloodstream causing bacteremia
What is the tests used for identifying Typhoid?
WIDAL test is a serological test used for typhoid screening this is done by measuring the Salmonella antibodies in a patients serum by adding antigens of S.typhi to a serially diluted patient
What are the virulence factors associated with shigella? also what diseases do they cause?
Shigella produce a Shiga toxin which is also known as a diarrhea-inducing enterotoxin
Virulence factors____________
Shiga toxin, Enterotoxic, neurotoxic and cytotoxic
Name the different species of shigella
- S.sonnei
- S.dysenteriae
- S.Flexneri
- S.boydii
Analogy: My little son is a dys-flexic boy
Name the Pathogenesis of Shigella
- Shigella attaches to the epithelial of the colon
2.Shigella will trigger endocytosis
3.Shigella will multiply in the cytosol
4.Shigella will invade neighboring epithelial cells thus avoiding defenses
5.An abscess(painful pus) forms as the epithelial cells are killed by the infection
6.shigella enters the bloodstream but will be quickly phagocytized
Difference is that salmonella will enter the bloodstream whereby shigella will not enter the bloodstream
What are the differential media used for Salmonella and shigella?
Salmonella Shigella Agar(SSA): Colorless colonies with black center
Desoxycholate Citrate Agar(DCA): Slightly pink colonies with a black center
Xylose lysine Dextrose agar: Black colonies on salmonella because of the H2S production
