Klebsiella pneumoniae liver abscess syndrome (KLAS) is an emerging infection caused by
hypermucoviscous strains (K1, rmpA, mgA) with a particular virulence at risk of metastatic
dissemination. We describe a case of metastatic KLAS in a Canadian immunocompetent patient
of Vietnamese origin who presented with fever and abnormal liver function tests. Imaging
studies revealed unique liver and pulmonary abscesses. Blood and liver abscess cultures showed
colonies of K.pneumoniae with hypermucoviscous phenotype, a K1 serotype and the presence
of a rmpA gene confirming biomolecular features of the invasive syndrome. Mostly reported in
patients of Asian origin, KLAS has been reported in Canada since 2007. Prompt identification
and treatment prevents severe complications such as endophthalmitis, meningitis, lung abscess
and spondylodiscitis.
Le syndrome dabcès hépatique à Klebsiella pneumoniae (KLAS en anglais) est une infection en
émergence résultant dune souche hypermuqueuse (K1, rmpA, mgA) dune virulence accrue, à
risque de dissémination. Nous décrivons un cas de KLAS métastatique chez un patient canadien
dorigine vietnamienne, immunocompétent, qui présentait de la fièvre et des anomalies du
bilan hépatique. Les imageries ont révélé des abcès hépatiques et pulmonaires uniques. Les
hémocultures et les cultures du drainage de labcès hépatique ont confirmé la présence d’une
souche hypermuqueuse de Klebsiella pneumoniae, sérotype K1, génotype rmpA, caractéristiques
biomoléculaires associées aux infections invasives. Principalement décrits chez des patients
dorigine asiatique, des cas de KLAS sont rapportés au Canada depuis 2007. L’identification et
le traitement rapide préviendront des complications sévères, dont l’endophtalmite, la méningite,
labcès pulmonaire et la spondylodiscite.
Keyword: liver abscess metastatic syndrome, hypermucoviscous
klebsiella pneumoniae
About the Authors
Dr. Sandra Criales is a 4th-year infectiology-microbiology resident at Universi Laval (Quebec City, Canada). Dr. Alexandre Lafleur
is assistant clinical professor of medicine at Universi Laval and specialist in general internal medicine at CHU de Québec. Dr. Phillipe
Gervais is an infectious diseases specialist at CHU de Québec and Quebec Heart and Lung Institute. This article was written in collaboration
with the QMA-CMA-MD Educational Leadership Chair in Health Professions Education at Université Laval Faculty of Medicine.
Correspondence can be directed to:
Submitted: March 3, 2018. Accepted: May 11, 2018. Published: February 12, 2019. DOI: 10.22374/cjgim.v14i1.278
Liver Abscess Metastatic Syndrome Caused by
Hypermucoviscous Klebsiella Pneumoniae in
a Canadian Patient of Vietnamese Origin
Sandra Criales, MD, Alexandre Lafleur, MD, MSc (Ed), Phillipe Gervais, MD
Case Study
Canadian Journal of General Internal Medicine
Volume 14, Issue 1, 2019 21
In March 2015, a 34-year-old patient presented at the emergency
department of CHU de Québec (CHUL) and was admitted to the
internal medicine clinical teaching unit. He reported one week
of fever and chills, profuse sweating, temporal headache, loss of
appetite, and myalgia. The patient emigrated from Vietnam to
Canada 11 years earlier and had not returned there since then.
His only recent trip had been to Boston in 2011. He completed
a treatment for latent tuberculosis in 2005. He worked as an
informatician, had no allergies, and did not take medication.
The patient reported no infectious contact, illicit drug abuse,
or other at-risk exposures for malaria, viral hepatitis, Q fever,
leptospirosis, or brucellosis. The patient did not complain of
rash, weight loss, or any abdominal, pulmonary, urinary, or
neurological symptoms.
The patient was diaphoretic without rash or jaundice.
Physical findings included a blood pressure of 90/58 mmHg,
a temperature of 38.9°C, a heart rate of 100 beats per minute,
non-painful cervical lymphadenopathy (less than 2 cm), and
hepatomegaly (2 cm below costal margin). The remainder of
the physical examination was normal without meningeal sings,
abdominal mass, tenderness, or ascites. Vital signs stabilized
rapidly with treatment and intravenous fluids.
Laboratory studies showed hyponatremia at 131 mmol/L
(135–145 mmol/L), white blood cell count at 9.9 × 10
thrombocytopenia at 50 × 10
g/L (150–400 × 10
g/L), abnormal
liver and pancreas functions tests: aspartate aminotransferase
0.68 µkat/L (<0.67 µkat/L ), gamma-glutamyl transferase 3.57
µkat/L (<0.83 µkat/L ), total bilirubin 31 µmol/L (0–21 µmol/L),
direct bilirubin 16 µmol/L (<4 µmol/L) amylase 2.99 µkat/L
(<1.67 µkat/L), lipase 4.21 µkat/L (< 0.92 µkat/L ). Tests for
amebiasis, echinococcosis, human immunodeficiency virus, and
hepatitis B–C were negative and tests for Epstein-Barr virus and
cytomegalovirus showed an ancient exposition.
Abdominal ultrasound, contrast-enhanced computerized
tomography (CT) scan, and magnetic resonance imaging (MRI)
showed a unique hepatic abscess with a diameter of 3.3 cm in
the eighth segment of the liver (Figure 1). A chest CT revealed
an asymptomatic pulmonary abscess in the right lower lobe
(Figure 2).
Blood cultures and cultures from percutaneous drainage of the
hepatic abscess grew Klebsiella pneumoniae with hypermucoviscous
phenotype, defined by a positive string test(viscous string >
5 mm when bacterial colonies on an agar plate are stretched
by an inoculation loop) as shown in Figure 3. The Canadian
Science Centre for Human and Animal Health (Winnipeg,
Canada) confirmed a K1 serotype and the presence of a rmpA
gene confirming biomolecular features of the invasive syndrome.
The pulmonary metastatic lesion was the hallmark for the
diagnostic of
pneumoniae liver abscess metastatic
syndrome (KLAS). Based on in vitro susceptibilities, piperacillin-
tazobactam, empirically given, was replaced by ceftriaxone for
six weeks of IV ambulatory treatment. The liver abscess, of less
than 5 cm, was entirely drained with a single percutaneous
needle aspiration, without surgery. Drainage was not indicated
for the uncomplicated pulmonary abscess. A cerebral MRI did
not show endophthalmitis, abscess or meningeal anomalies.
Figure 1. Abdominal ultrasound showing a 3.3-cm abscess in the eighth
segment of the liver.
Figure 2. Chest computed tomography scan revealing a 2.9 × 2.3 cm pulmonary
abscess in the right lower lobe.
Canadian Journal of General Internal Medicine
22 Volume 14, Issue 1, 2019
Liver Abscess Metastatic Syndrome Caused by Hypermucoviscous Klebsiella Pneumoniae
Lumbar puncture was not initially performed because of the
Followed until July 2015 by CT scans, hepatic and pulmonary
lesions disappeared, and liver tests normalized after antibiotic
treatment. The patient has not relapsed.
Klebsiella pneumoniae is a well-known gram-negative bacillus
with a thick polysaccharide. Standard clinical diseases are related
to K. pneumoniae and K. oxytoca
such as pneumonia, urinary
tract infections, abdominal cavity surgery-related infections and
several nosocomial syndromes
often associated with a history
of alcohol abuse or diabetes mellitus.
KLAS is a distinctive infection related to specific subcapsular
serotypes and a marked virulence that produces liver abscesses
and several distant metastatic infections.
Described mostly in the
Asian population since the 1980s, cases have been diagnosed in
North and South America,
and Australia.
A liver abscess caused by this particular microbiological
strain with extra-hepatic infections should be recognized as
The clinical signs of KLAS are fever, chills, headache,
and abdominal pain. Nausea and vomiting occur in about 25% of
Half of the patients have jaundice and hepatomegaly.
Blood test findings are leucocytosis, increased C-reactive protein,
abnormal liver function tests, and thrombocytopenia.
Metastatic spread, unusual for most enteric gram-negative
bacilli, is a hallmark of the hypermucoviscous Klebsiella
pneumonia strain infecting immunocompetent hosts. From
8 to 30% of metastatic disease in KLAS,
a case series of 23
patients with metastatic lesions reported mostly endophthalmitis,
uveitis, pulmonary abscess, and purulent meningitis.
Klebsiella pneumoniae
(hvKP) is directly
to the hypermucoviscous phenotype, related to the k1, k2
and the regulator of mucoid phenotype A (rmpA)
This feature gives this type of pathogen the ability to
produce lethal
extra liver infections in non-
immunocompromized patients.
Numerous virulence
factors have been elucidated and implicate
the presence of
mucoviscosity genes like magA, rmpA, aerobactin
but the exact
mechanism by which this spreading take place
Shon et al. observed that hvKP was resistant to
complement- and neutrophil-mediated bactericidal activity in a
rat subcutaneous abscess model
and produces more biofilm than
others strains.
This capacity increases intestinal colonization.
In this case, this patient developed KLAS even if he had been
colonized in an endemic area several years ago. Colonization
usually happens when there is a disruption of the natural barriers
(ascension into the bladder, aspiration into the respiratory tract,
gastrointestinal colonizers) but KLAS has been reported in people,
like this patient, without evidence of altered mucosal barriers.
Even though the majority of patients with hvKP infection are
healthy, there is a significant mortality rate between 3 and 42%
in part following necrotizing fasciitis and severe community-
acquired pneumonia.
Moreover, survivors can suffer appalling
consequences such as blindness and neurologic sequelae.
Even if most hvKP infections are treatable with
common antibiotics, long-term follow-up is necessary because
of the high risk of relapsing. Several cases of resistant strains
with extended spectrum B-lactamases and carbapenemases have
already been reported.
All these characteristics could
hvKP one of the next “superbugs.
To our knowledge, this is the first report of a complete metastatic
syndrome by HvKp in Canada, following the first published
case of pyogenic liver abscess caused by hvKP in Manitoba in
Compelling questions about hvKP remain unanswered.
Its natural course is barely understood. Diagnostic features such
as a positive string testand capsular serotypes like K1 or K2
are not always distinctive of hvKP.
Its capacity for metastatic
spread, an unusual trait for an enteric gram-negative, is a
worrying characteristic of this strain of Klebsiella that is no
longer confined to Asia.
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Figure 3. Patient’s isolated colonies plate culture demonstrating a positive
‘string test’ (formation of a viscous string >5 mm).
Canadian Journal of General Internal Medicine
Volume 14, Issue 1, 2019 23
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