Discussion
cKP and hvKP
Klebsiella pneumoniae , a gram-negative bacillus, has been
implicated as a cause of pneumonia, urinary tract infection, abdominal
cavity infection, and intravascular device infection; this type ofKlebsiella pneumoniae is recognized as classical Klebsiella
pneumoniae (cKP) [1]. However, different types of Klebsiella
pneumoniae have been recognized, starting in East Asia. The first
report of a unique Klebsiella pneumoniae was reported in Taiwan
in the 1980s, with characteristic of community-acquired infection with
complications of pyogenic liver abscess and endophthalmitis [3].
Similar cases were reported afterward worldwide. This new and unusual
type of Klebsiella pneumoniae has been studied and named hvKP
based on its malignancy. The features of hvKP have been described as
community-acquired infection among healthy young individuals, which
tends to be associated with endophthalmitis, multiple abscesses, and
especially liver and septic arthritis. It has been reported that 90.9%
of the pathogens causing liver abscesses with Klebsiella
pneumoniae infection are hvKP [4]. The string test, which uses an
inoculation loop to generate a viscous string from a bacterial colony,
is used for differential diagnosis between cKP and hvKP. If a string
length of > 5 mm is generated because of
hypermucosviscosity, the test is considered positive [5]. However,
the specificity of the string test and hvKP varies between 51% and
98%, and even cKP shows positive string test rates of 17% to 23%
[6]. Although one retrospective study reported no clinical relevance
of a 30-day mortality rate between cKP and hvKP [7], a review
article demonstrated that hvKP is associated with a significant
mortality rate of 3 to 55% compared to cKP [1]. Iron acquisition
has been described as the decisive factor of hvKP’s hypervirulence
compared to cKP [1].
Our patient had hvKP infection with a positive string test, and this
infection induced multiple abscesses, such as liver abscess,
retropharyngeal abscess, and psoas major abscess. He had septic shock
because of severe hvKP infection. Therefore, endotoxin adsorption
therapy with a longer PMX-DHP duration was performed 2 times to treat
his septic shock. PMX-DHP has been shown to adsorb not only endotoxin
but also monocytes and anandamide, resulting in a reduction in blood
levels of inflammatory cytokines such as interleukin-6, tumor necrosis
factor-alpha and interleukin-17A [8]. In addition, we have shown
that a longer duration of PMX-DHP improves hemodynamics and decreases
vasopressors rapidly compared to the conventional duration, and a ≥
8-hour duration of PMX-DHP was associated with an improvement in
pulmonary oxygenation [9]. As a result, our patient’s hemodynamics
and pulmonary oxygenation improved after PMX-DHP treatment, and he
recovered from septic shock. It is important for clinicians to be aware
of hvKP, and whole-body examination must be conducted, with or without
the positive string test, when suspected.
Infectious rhabdomyolysis due to hvKP
At first, our patient presented complained of weakness in the lower
limbs, slurred speech, and lower back pain. He was diagnosed with
rhabdomyolysis because of a high serum CK level (37370 U/L) and high
myoglobin level (11850 ng/mL). Rhabdomyolysis is a fatal clinical
condition caused by the release of toxic intracellular content from
damaged skeletal muscles. Although there are no diagnostic criteria for
rhabdomyolysis, a serum CK level higher than 10 times the normal value
in the absence of heart or brain diseases is used for clinical
indication [10]. Despite multiple of rhabdomyolysis, rhabdomyolysis
secondary to infection is uncommon. Furthermore, infectious
rhabdomyolysis is reported to have a poorer prognosis (such as incidence
of acute kidney failure) than rhabdomyolysis secondary to exercise
events, though peak CK and myoglobin levels are lower in the former
[11]. The most commonly reported organisms causing infectious
rhabdomyolysis are Legionella spp., Streptococcus spp.,Salmonella spp., and influenza virus, and the main site of
primary infection is the respiratory tract [12,13]. There are
several hypotheses regarding the mechanism of infectious rhabdomyolysis,
but none of them are well established: direct muscle invasion of
bacteria or viruses, immunologic reactions such as ‘cytokine storms’,
toxic effects from bacteria or viruses, and muscle damage caused by high
fever and hypoxia [13]. Significant mortality of 38% in infectious
rhabdomyolysis has been reported [14].
Because our patient did not have any initial imaging findings except for
the hypodense lesion in the liver, we suspect that the primary source of
infection was a liver abscess. To the best of our knowledge, there are
only two English reports describing cases of rhabdomyolysis secondary to
liver abscess [4,15], but there are no reported rhabdomyolysis cases
due to hvKP infection. Our case was rhabdomyolysis secondary to hvKP
infection, making liver abscess the primary focus. Overall, this was an
extremely rare case with a good course despite the high mortality rate.