Case History No. 10
Submitted by: Brent Barrett, B.S., M(ASCP)
Indiana State Department of Health
Enterics and Parasitology Laboratories
Indianapolis, Indiana
Rare Food = Rare Bug
An Indiana resident presented with symptoms of diarrhea,
nausea, vomiting, cramps, and chills.
A travel history was taken, which revealed a recent trip to
Florida, in which the patient sampled the local seafood
including lightly cooked oysters.
In the lab, stool cultures showed yellow colonies on TCBS
Agar plates. In addition, a string test was performed giving
positive results.
What is it?
Answer:
In late March to early April, 2011, an outbreak occurred in
northern Florida with eleven reported cases and ten confirmed
cases due to cholera toxin producing Vibrio cholerae serotype
O75. Seven cases were Florida residents, and three were from
Georgia, Louisiana and Indiana, with current travel history to
Florida.
After consuming raw or lightly cooked oysters (figure 1)
harvested from Apalachicola Bay, Florida, they presented with
gastrointestinal symptoms of diarrhea, nausea, vomiting,
cramps, chills, and/or fever. Symptoms were milder than those
during outbreaks of epidemic Vibrio cholerae serogroup O1
and O139. None required rehydration treatment or were
hospitalized and no deaths occurred in the first reported
outbreak of this rare strain of Vibrio cholerae and oyster
consumption.
Figure 1: The ingestion of raw or undercooked oysters is usually
associated with Vibrio vulnificus. Oysters are sedentary
bivalve mollusks that feed by filtering plankton from estuarine
water. Because Vibrio vulnificus occurs naturally in the same
waters that oysters feed, the bacteria is ingested and becomes
assimilated and concentrated in the animal’s tissues. When
people ingest oysters, there is a risk of also ingesting Vibrio
vulnificus or more rarely, Vibrio cholerae, as described in this
case history.
Florida Department of Health began the investigation and a
trace back of the oysters was conducted by the Florida
Department of Agriculture. The affected oysters were
harvested from Area 1642 in Apalachicola Bay in the Gulf of
Mexico between March 21 and April 6, 2011. The harvesting
area was closed and re-opened for harvesting after 15 oysters
samples from ten different sections of the implicated harvest
area tested negative for V. cholerae O75.
Vibrio spp. are common in coastal waters and found in local
shell fish. Vibrio vulnificus is an important cause of
gastrointestinal illness and wound infections in Florida . Vibrio
cholerae has over 180 serogroups and most are non-toxigenic.
Infections caused by toxigenic V. cholerae strains especially
serotype O1 and O139 can cause sporadic cases, outbreaks and
pandemics, but rarely occur in the United States. Most of the
reported cases are related to travel outside the US.
The Indiana case was detected by a South Bend, Indiana
clinical and reference laboratory and the V. cholerae isolate
was reported and referred to the Indiana State Department of
Health (IN SHD) for confirmation. At IN SHD, the isolate
was planted to Thiosulfate Citrate Bile Sucrose (TCBS) agar
(figure 2) and Blood Agar plates.
Figure 2: Vibrio cholerae colonies will be yellow on TCBS Agar,
Cat. no. G55. V. vulnificus colonies are usually green, and V.
parahemolyticus colonies are blue to green within 24 hours.
Suspected colonies are checked by conventional biochemicals,
oxidase, string test (figure 3) and API 20E. Vibrio discs offer
another way to differentiate Vibrio spp from other gram
negative rods.
Figure 3: Showing a positive string test with V. cholerae. When
the colonies are mixed with a drop of 0.5% sodium
deoxycholate on a glass slide, they produce a viscous
suspension that can be drawn into a sting when the
inoculating loop is slowly raised from the slide after 60
seconds. This test solution can be prepared by making a 1:20
dilution of the Bile Spot Test (Cat. no. Z61, 10% sodium
deoxycholate).
Once confirmed by biochemical tests as V. cholerae, the
isolate was tested with V. cholerae serotype O1 and O139
antiserum, which were negative and reported as Vibrio cholera
non- O1 and non-O139 then forwarded to the Center for
Disease Control for additional characterization, cholera toxin
and serology testing.
This is the first reported outbreak due toxigenic V. cholerae
O75 and oyster consumption. The detection of this outbreak
could be due to testing stools for Vibrio spp more common in
states along coastal waters. Two events that may have caused
the contamination of oyster beds are being investigated.
Dredging operations near Area 1642 harvesting area that may
have stirred up organisms on the sea floor and a sewer break at
the Eastpoint, Florida sanitation treatment facility. Toxigenic
V. cholera O75 strains have the cholera toxin gene and can
cause severe diarrhea, but are infrequently seen in the US.
Laboratories, clinicians and public health officials should be
aware of new and emerging toxigenic V. cholerae non-O1 and
non-O139 serogroups and request Vibrio cultures as needed.
Submitted by:
Brent Barrett
Indianapolis, Indiana
Website: www.HardyDiagnostics.com
Email: [email protected]
Phone: (800) 266-2222
Address: 1430 West McCoy Lane, Santa Maria, CA 93455