P1253814630hFkAd

1
Occupational Exposure to Streptococcus suis
Z-061
Tara C. Smith, Ana Capuano, Brenda Boese, Kendall
Myers, and Gregory C. Gray Center for Emerging
Infectious Diseases Department of
Epidemiology University of Iowa College of Public
Health, Iowa City, IA

RESULTS
SUMMARY
BACKGROUND
ABSTRACT

• Streptococcus suis--swine
• Swine pathogen
• Causes meningitis in newborn pigs
• Transmitted from mother to piglet
• Streptococcus suishuman
• Sporadic human cases noted
• 2005 large outbreak in China due to serotype
  2
• 215 infections, 38 deaths 1, 2
• Toxic shock-like manifestation
• First reported US case in 2006 3.

• Swine-exposed individuals had higher mean
  titers of anti-S. suis antibodies than
  non-exposed individuals.
• Those with the highest titers reported greater
  than 10 years of working with swine.
• 1 individual reported never wearing gloves when
  working with swine.

Streptococcus suis is a gram-positive bacterium
that causes invasive disease and death in swine.
This bacterium is considered an emerging disease
in humans, and was the cause of an outbreak which
sickened over 200 individuals in China in 2005.
Previously documented human cases of S. suis
infection have occurred primarily in those who
contracted the bacterium via occupational
exposure. Despite a high prevalence in swine, it
was only in 2006 that the first human case of
invasive disease due to S. suis was diagnosed in
the United States. Prior research shows that
because S. suis is considered to be typically a
swine pathogen and only rarely a cause of human
disease, infection is incorrectly attributed to
other species of streptococci, including
Streptococcus pneumoniae and viridans
streptococci. Therefore, we hypothesized that
human infections with S. suis are more common
than currently recognized. To test this, we
analyzed by ELISA the sera of 73 swine-exposed
subjects and 67 non swine-exposed subjects in
Iowa, testing for antibodies to S. suis serotype
2, the most common serotype to cause disease in
humans. Groups mean optical densities were
compared using generalized linear models. The
exposed group presented higher mean optical
density at all titer levels. Two swine-exposed
observations above 2 standard deviations of the
mean were identified. One individual was found to
have worked with finish and nursery swine, and
the second worked with finishing but not with
nursery swine. One of them reported never using
gloves when working with sick swine. This
suggests that human infection with S. suis occurs
more commonly than currently documented,
particularly among those in close contact with
swine.
CONCLUSIONS

• S. suis infects humans more frequently than
  currently recognized.
• Swine-exposed individuals are at risk of
  exposure.
• Future studies will further investigate
  exposure and carriage of S. suis in
  swine-exposed individuals.

STUDY PROTOCOL

• Population
• Swine-exposed individuals (n73) and
  non-exposed individuals (n67) from Iowa 4.
• IRB approval was obtained prior to collection.
• Questionnaire data
• Individuals completed questionnaires asking
  about swine exposure and personal protective
  gear and practices.
• Clinical specimens
• Blood samples were collected from all
  participants.
• Molecular methods
• Whole cell enzyme-linked immunosorbant assay
  (ELISA) using S. suis serotype 2.

STUDY LIMITATIONS

• Samples were not collected specifically for our
  study, and no samples were collected for
  bacterial isolation.
• No human positive control was available.
• Study tested only one serotype (type 2) of S.
  suis. Additional serotypes may also infect
  humans therefore, our data are likely an
  underestimation of true infection prevalence.
• Time period of infection is unknown therefore,
  waning antibody
• titers in exposed individuals also may
  underestimate actual infections.

Figure 1 Comparison of group mean optical
density by dilution, and 95 confidence intervals
around mean.
WORKS CITED
STUDY QUESTIONS
DATA ANALYSIS

• Sriskandan S, Slater JD. Invasive disease and
  toxic shock due to zoonotic Streptococcus suis
  an emerging infection in the East? PLoS Med
  20063e187
• Tang J, Wang C, Feng Y, et al. Streptococcal
  toxic shock syndrome caused by Streptococcus
  suis serotype 2. PLoS Med 20063e151
• Willenburg KS, Sentochnik DE and Zadoks RN.
  Human Streptococcus suis meningitis in the
  United States. N Engl J Med 20063541325
• Myers KP, Olsen CW, Setterquist SF, et al. Are
  swine workers in the United States at increased
  risk of infection with zoonotic influenza virus?
  Clin Infect Dis 20064214-20.

• How frequently does Streptococcus suis
  infection occur in those in close contact with
  swine?
• Does infection with S. suis vary according to
  work area and duty?
• What are the risk factors associated with
  infection by S. suis in swine workers?

• Optical Density
• Groups mean optical density (OD) results were
  compared using generalized linear models.
• The least square mean and 95 confidence
  interval were calculated per group.
• Risk factors associated with prior infection
• Questionnaire data was examined to determine
  risk factors for infection.

at
least in one dilution optical density (OD)
greater than two standard deviations above the
mean
Table 1 Characteristics of swine exposed
subjects