Beth Schweitzer MT(ASCP), SM Nebraska Public Health Laboratory
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Transcript of Beth Schweitzer MT(ASCP), SM Nebraska Public Health Laboratory
Beth Schweitzer MT(ASCP), SM Nebraska Public Health
Laboratory
Enteric Pathogens Beth Schweitzer MT(ASCP), SM Nebraska Public
Health Laboratory Pathogens Routinely Tested
Salmonella spp. Shigella spp. Campylobacter spp. Aeromonas
Plesiomonas Vibro This is a list of pathogens that will be detected
by a routine Stool Culture.A Stool Culture must be held for 48
hours before it can be determined negative.However, a positive may
take slightly longer to fully identify the organism involved.
Pathogens Tested for upon request
Yersinia entercolitica E. coli 0157:H7 Vibrio Must be specifically
requested This is a list of organisms that must be specifically
requested in order for them to be identified.There are special
medias required for their identification.A physician must order a
test for these organisms. Testing for Salmonella/Shigella
Look for appearance of colonies on specialized media Normal Enteric
Flora Stool is not a sterile body site, as we all know.The lab uses
special medias that let us see what sugars the bacteria can use as
a food source, as a way to help identify them.These are 2 pictures
of normal enteric flora.See the pink colonies and the yellow
colonies. Salmonella/ Shigella This is a picture of an isolate of
Salmonella or Shigella.Notice the colonies are clear, as compared
to the pink colonies on the previous slide. E. coli/ Shigella This
is a picture of E coli on the top and Shigella on the bottom.Notice
the yellow colonies as compared to the dark green colonies on the
bottom. Salmonella This is a picture of an isolate of
Salmonella.Salmonella is able to perform a biochemical reaction on
this media that causes the colonies to become black.Notice the
colonies with the black centers. Campylobacter testing
Look for colonies on media after incubation at specific
temperatures and atmospheric conditions Campylobacter needs special
atmospheric conditions that help inhibit the other normal enteric
flora.It is also able to grow at warmer temperatures than the
normal enteric flora.Because of the special atmospheric needs, this
is why we need to get the stool specimen as soon as possible or it
may die.There are special enteric preservatives you can put the
stool into if there is going to be a delay in transport.
Campylobacter screening
This is baggie we fill with gas so the Campylobacter can grow.
Campylobacter spp. This is an electron micrograph picture of
Campylobacter. Gram- Negative cell structure
Once we have a organism identified we now have to use structures on
the cell surface to serogroup and serotype the organism. There are
proteins sticking off the surface of the cell wall, they are known
as the O antigens Salmonella Serogrouping
Based on Cell Wall Antigens (O) Somatic Each antigen identified by
a number designation Multiple antigens can be present on each cells
surface Serogroup is determined by pattern of O antigens present
95% of isolates belong to serogroups A-E (O2-O10) Remaining 5% O
antigens O11-O67 Commercial kits available Latex agglutination
These O antigens are what determine the serogroup. Next we look at
the proteins that are on the flagellum. Salmonella serotyping
Based on Flagellar antigens (H) Each antigen identified by a letter
or number designation Multiple antigens can be present on each
isolate Most isolates can posses 2 sets (phase1/phase 2) Serotype
is determined by O antigens present and phase 1/phase 2 H antigens
Over 2400 different serotypes Over 1400 common to humans No
commercial kit available Serotyping End up with an antigenic
formula
O antigen: Phase 1 H antigens: Phase 2 H antigens Most common
formulas have a name Salmonella serotype Typhimurium (4,5:i:2)
Serogroup B Salmonella serotype Enteritidis (9:gm:-) Serogroup D E.
coli O157:H7 First look for E. coli in stool
Sorbitol negative Test organism for presence of O and H antigens
Commercial kit available In order to find E coli in stool we use
special media to help us tell the difference between the normal
healthy E coli, and the E coli O157:H7.E coli O157:H7 cannot use a
sugar called sorbitol as food, where normal E coli can.Once we find
a sorbitol negative E coli, we then test for the specific O and H
antigens. This is a basic antigen/ antibody reaction, and is the
basis for our latex agglutination tests.As the antibodies bind up
the antigens they begin to clump up.If the antibodies are bound to
latex beads we then can visualize the clumping. Circle 2 contains a
positive latex agglutination test you can see the beads are all
clumped together as compared to the homogenous texture of circle 1.
Further testing All E coli O157:H7 isolates have Pulse field gel
electrophoresis (PFGE) performed on them Any other organisms can
have PFGE performed, at the request of the state Once we have
identified an E coli O157:H7 Pulse Field Gel Electrophoresis is
performed.The state of Nebraska has decided that PFGE is to be
performed on all E coli O157:H7 that are found in the state.We can
perform PFGE on any organism, but it must be requested by the
state. Any questions??Contact information