The Corpus Callosum

Streptococcus suis Outbreaks

Posted by Joseph j7uy5 on July 26, 2007
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Infections
with href="http://www.wpro.who.int/media_centre/fact_sheets/fs_20050802.htm"
rel="tag">Streptococcus suis
have been reported in a cluster in Viet Nam, plus one
apparently-isolated case in China.  This is not the first
outbreak of the pig-borne illness.  A href="http://www.who.int/csr/don/2005_08_03/en/index.html">larger
outbreak occurred in 2005 in Sichuan, China.  In
2005, there were 205 reported cases, with 36 fatalities.
 Earlier, a 1998 outbreak involved 14 deaths out of 25
reported human cases.  Cases have been recorded dating back to
the 1960′s.  No cases have been reported in the USA or Canada,
but it has href="http://genome.jgi-psf.org/draft_microbes/strsu/strsu.home.html">been
alleged that this may be because labs here don’t look for it
and probably would misidentify it.  

The current
outbreak has led to 42 identified infections in Viet Nam,
with two fatalities so far.  In addition, there has been href="http://www.chinadaily.com.cn/china/2007-07/26/content_5443473.htm">one
reported case in Shenzhen, China (near Hong Kong).  

Streptococcus suis can cause a nasty illness.
 Initial symptoms are nonspecific: high fever, malaise,
nausea, vomiting.  This can progress to href="http://www.merck.com/mmhe/sec06/ch089/ch089b.html"
rel="tag">bacterial meningitis, with symptoms of
neck stiffness, photophobia, and headache. The meningitis can cause
hearing loss. It can lead to impaired level of consciousness, coma, and
death.  Other complications can include href="http://www.emedicine.com/med/topic3394.htm" rel="tag">septic
arthritis or href="http://www.emedicine.com/med/topic2292.htm" rel="tag">toxic
shock syndrome.  The incubation period could be as
short as a few hours, or as long as a few days.  

Most cases are due to handling of infected pork.  Infection
can be spread through skin injuries or contact with mucous membranes,
including inhalation.
 

href="http://medicine.plosjournals.org/perlserv/?request=get-document&doi=10.1371/journal.pmed.0030187">i-727c55b5039d62ccf4ea70376862fa43-Strep_suis.jpgIf that is not enough detail, Dr.
Smith has a more href="http://scienceblogs.com/aetiology/2006/04/suis.php">thorough
review at Aetiology.  Her main
reference, by the way, is PLOS Medicine: href="http://medicine.plosjournals.org/perlserv/?request=get-document&doi=10.1371/journal.pmed.0030151">Streptococcal
Toxic Shock Syndrome Caused by href="http://medicine.plosjournals.org/perlserv/?request=get-document&doi=10.1371/journal.pmed.0030151">Streptococcus
suis href="http://medicine.plosjournals.org/perlserv/?request=get-document&doi=10.1371/journal.pmed.0030151">
Serotype 2.
 The accompanying commentary, href="http://medicine.plosjournals.org/perlserv/?request=get-document&doi=10.1371/journal.pmed.0030187">Invasive
Disease and Toxic Shock due to Zoonotic Streptococcus suis:
An Emerging
Infection in the East?, concludes that S.
suis is a serious problem with the potential for recurrent
outbreaks with multiple human fatalities, and for serious economic
consequences.

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Comments

  1. #1 Paul Orwin
    July 26, 2007

    I find this (and another recent similar article in PLOS One) very odd. Not the actual cases themselves (not much question there) but the STSS issue. As far as I know (and I’m not a world expert, but I did do my grad work on TSS), there must be a superantigen associated with this disease. They apparently haven’t been able to identify it, but it must be there somewhere. It definitely could be a serious problem. To call it STSS and not make an extensive effort to isolate a superantigen is weird to me.

  2. #2 Tara C. Smith
    July 26, 2007

    Hi Paul,

    They’re working on that part of it. The Chinese outbreak was the first time the toxic shock manifestation has been seen in an outbreak of S. suis, and the diagnosis was made on clinical signs rather than presence of any toxin, which I think is fair given the circumstances (and dearth of any real understanding of STSS in any strep species besides group A–and even that’s not all that great). There actually is a more recent paper in PLOS One where they did comparative genomics, and found a pathogenicity island associated with the STSS phenotype. They still haven’t figured out exactly how it’s causing the disease, though.

  3. #3 Paul Orwin
    July 26, 2007

    Hi Tara,
    I saw that paper (I even left a brief comment similar to the one above. I certainly don’t dispute the diagnosis (I’m not qualified!) but I think perhaps they should look harder for a pyrogenic toxin. You are right, though, that we are quite ignorant of mechanism of TSS outside S. aureus and STSS in GAS. I didn’t look at the sequences of their putative PAIs. If I get a chance I might check it out. My Ph.D. was based mostly on identifying novel toxin genes in the unfinished COL genome (long time ago!) and using that to clone some toxins out S. aureus. The SAg fall into some distinct families, and aren’t too hard to find.