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Maine E. coli O157:H7
Illnesses Linked to National Cluster of Illnesses Source of
Article: http://www.marlerblog.com/ Maine
CDC is investigating a cluster of 7 shiga toxin positive E. coli O157:H7
(STEC) cases in Cumberland and York counties that occurred among residents
over the past month (case onset dates of April 17 to May 17). This is double
the usual number of STEC cases reported this time of year (n=3). The median
age of cases was 26 years (age range 14 years to 65 years). As of May 28, 6
of the 7 cases have been confirmed shiga positive E. coli O157:H7 by the
Health and Environmental Testing Laboratory (HETL). Of these, 4 cases match
by Pulse-Field Gel Electrophoresis (PFGE) and are considered part of a
national cluster. At this time, the investigation is ongoing although we have
not identified any common venues, events or foods based on case interviews. What is PFGE? When a sample is taken from
either a person, piece of meat or poultry that is contaminated with a
dangerous form of bacteria, such as E. coli O157:H7, listeria, or
campylobacter, it can be cultured to obtain and identify the bacterial
isolate. If a person consumes some of the contaminated meat or poultry, and
becomes infected as a result, a stool sample can then be cultured to obtain
and identify the bacterial isolate. These bacterial isolates are then broken
down into their various component parts creating a DNA
"fingerprint". The process of obtaining
the DNA fingerprint is called Pulse Field Gel Electrophoresis, or PFGE. This
technique is used to separate the DNA of the bacterial isolate into its
component parts. It operates by causing alternating electric fields to run
the DNA through a flat gel matrix of agarose, a polysaccharide obtained from
agar. The pattern of bands of the DNA fragments — or “fingerprints” — in the
gel after exposure to the electrical current is unique for each strain and
sub-type of bacteria. By performing this procedure, scientists can identify
hundreds of strains of E. coli O157:H7 as well as strains of listeria and
campylobacter, and other pathogenic bacteria. The PFGE pattern of the
bacteria can then be compared and matched up to the PFGE pattern of the
strain of infected persons who consumed the contaminated product. When PFGE
patterns match, they, along with solid epidemiological work, are proof that
the contaminated product was the source of a person's illness. It will be interesting to
see if Maine, the CDC and other States' Health Departments will be able to
link the illnesses in Maine to other states and to a possible source. |
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