APHL 2019 POSTER ABSTRACTS
Methods: US states voluntarily report cryptosporidiosis cases
to CDC through NNDSS. Eleven states participate in enhanced
cryptosporidiosis surveillance through CryptoNet; other states
can also submit specimens for genotyping. State collaborators 1)
genotype Cryptosporidium specimens or send them to CDC and
2) complete the CryptoNet case investigation form, which focuses
on exposures (e.g., waterborne, foodborne, person-to-person, and
zoonotic). NNDSS and CryptoNet data from 2016 were analyzed
using R and SAS 9.4.
Results: For 2016, 13,471 cases were identified in the NNDSS
database; a subset (321, 2%) had genotyping and exposure data
in the CryptoNet database. Demographic similarities were noted
between NNDSS and CryptoNet datasets; females accounted for
>50% of cases, and children ages 0–14 years accounted for >25%
of cases. Most (>90%) of CryptoNet specimens were C. hominis or
C. parvum. Treated recreational water (e.g., pool) exposure, contact
with children in childcare, and contact with diapered persons were
each noted more frequently among C. hominis cases. Untreated
recreational water (e.g., lake), drinking water (e.g., private well,
bottled water), and animal contact (e.g., calf) were each noted more
frequently among C. parvum cases.
Presenter: Dawn Roellig, Centers for Disease Control and
Prevention, Atlanta, GA, [email protected]
Is a Positive Shiga Toxin Test a Shiga Toxin-Producing E.
coli Infection? — Foodborne Diseases Active Surveillance
Network (FoodNet) — 2012−2017
D. Tack 1 , K. Barrett 1 , C. Medus 2 , K. Garmen 3 , J. Dunn 3 , S. Hurd 4 , J.
Hatch 5 , K. Parada 6 , S. Wilson 7 , E. Wilson 8 , K. Wymore 9 , P. Griffin 1 , A.
Geissler 1 ; 1 Centers for Disease Control and Prevention, 2 Minnesota
Department of Health, 3 Tennessee Department of Health,
4
Connecticut Emerging Infections Program, 5 Oregon Health Authority,
6
Georgia Emerging Infections Program, 7 Georgia Department
of Public Health, 8 Colorado Department of Public Health and
Environment, 9 California Emerging Infections Program
Background: FoodNet conducts active laboratory-based surveillance
for Shiga toxin-producing E. coli (STEC) in 10 US sites. During 2007–
2017, FoodNet reported increased culture-independent diagnostic
test (CIDT) use and decreased isolation of STEC by culture. In the
absence of an STEC isolate, FoodNet has excluded cases whose
Shiga toxin (Stx) CIDT results were not confirmed by a public health
laboratory (PHL). In 2018, the STEC national case definition was
updated to include infections diagnosed by any CIDT.
Methods: We examined STEC infections reported to FoodNet during
2012−2017 with a positive Stx immunoassay (IA) or polymerase
52
LAB MATTERS Summer 2019
Results: During 2012−2017, 8,260 (76% of all STEC reported)
cases tested positive by IA or PCR at a clinical laboratory followed
by an IA or PCR at a PHL. Among these, 1,736 (21%) were excluded
from FoodNet case counts. Twenty-nine percent of cases had
positive results by CIDT alone. Some cases had two CIDT tests
performed, resulting in 8,989 total test combinations. The most
frequent combination was IA/PCR (57%), followed by IA/IA (26%)
and PCR/PCR (25%); most (98%) were also tested by culture. Of
the test combinations performed, 1,911 (29%) were discordant
(range by state, 10%–44%). Among the IA/PCR test results, 18%
were discordant, and 14% of those cultured had STEC isolated. A
higher proportion of IA/IA (27%) and PCR/PCR (23%) results were
discordant, and 5% of those cultured had STEC isolated. Persons
with discordant test results were less likely to have diarrhea (91%
vs. 97%) or bloody diarrhea (28% vs. 57%). Test result discordance
increased markedly from 2012 to 2017 in all sites for IA/PCR (11%
to 21%), IA/IA (17% to 34%), and PCR/PCR (6% to 24%).
Conclusions: Accepting multiple test results with differing sensitivity
and specificity complicates surveillance. Marked variation in
frequency of discordant Stx results and identification of STEC
isolates by state highlights how sensitivity and specificity of different
test types, test targets, and specimen transport might affect STEC
results and surveillance. Including all infections diagnosed by any
CIDT could increase FoodNet STEC case counts and challenge
interpretation of national trends.
Presenter: Danielle Tack, Centers for Disease Control and
Prevention, Atlanta, GA, [email protected]
Detecting Potential Outbreaks and Related Isolates Quickly
and Easily Using MASH
L. Fink, C. Kapsak, J. Sevinsky and E. Travanty, Colorado Department
of Public Health and Environment
Identifying foodborne outbreaks of bacterial disease quickly and
efficiently is a major goal of public health laboratories, both at the
state and federal level. While national organizations have many
resources, both computationally and personnel-wise to combat
outbreaks that are noticed across multiple states, many state
partners lack sufficient resources to track and identify state-wide
outbreaks before they become major problems. Towards this
end, we have been experimenting with the open-source program
MASH as a way to generate a MinHash representation of all the
isolates that have come through the Colorado Department of Public
Health and Environment (CDPHE) for whole genome sequencing
(WGS). This quasi-database distills down the information to a small
and useable search space, such that when any new isolates are
sequenced, they can be sketched and compared to the entirety of
the previously sequenced isolates in a fast and easy manner. In this
way, isolates which may be close genetic matches to one another
can be identified rapidly. Then, more robust snp, wgMLST, or core
genome comparison methods can be applied in a targeted manner
to determine true genetic distance, and give information on whether
epidemiologists need to be informed. This system has the potential
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Discussion: Analysis of early enhanced surveillance data suggest
that exposures differ by Cryptosporidium species. Strengthening
surveillance by increasing the systematic collection of genotyping
and exposure data will be used to develop and implement
increasingly effective cryptosporidiosis prevention measures.
CryptoNet is helping to modernize national cryptosporidiosis
surveillance in two ways: first, CryptoNet laboratory database will be
integrated into the PulseNet BioNumerics platform (i.e., this will be
used in the future to streamline workflows); and second, exposure
data defined by the CryptoNet case report form are included in the
Foodborne and Diarrheal Diseases Message Mapping Guide as part
of the NNDSS Modernization Initiative to support standardized HL7
messaging of exposure data from states to CDC.
chain reaction (PCR) test at a clinical laboratory, followed by
testing of the same or another specimen at a PHL. Three test type
combinations were assessed (IA/IA, PCR/PCR, and IA/PCR) by state,
symptoms, test discordance, and culture result. A positive Stx CIDT
at a clinical laboratory followed by a negative Stx CIDT at the PHL
was considered discordant.