A Case of Carbapenem Resistant Non-K1/K2 Serotype <i>Klebsiella pneumoniae</i> Liver Abscess

doi:10.4236/aid.2013.33032

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Advances in Infectious Diseases, 2013, 3, 219-222

http://dx.doi.org/10.4236/aid.2013.33032 Published Online September 2013 (http://www.scirp.org/journal/aid)

219

A Case of Carbapenem Resistant Non-K1/K2 Serotype

Klebsiella pneumoniae Liver Abscess

Lucy Cheng1, Leung Kristopher Siu2, Tom Chiang1,3

1Department of Medicine, Rutgers New Jersey Medical School, Newark, USA; 2Institute of Infectious Diseases and Vaccinology,

National Health Research Institutes, Miaoli, Taiwan; 3Division of Infectious Disease, Veterans Affairs New Jersey Health Care Sys-

tem, East Orange, USA.

Email: [email protected]

Received July 30th, 2013; revised August 15th, 2013; accepted August 20th, 2013

which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

ABSTRACT

Klebsiella pneumoniae liver abscess (KPLA) has been described as an invasive syndrome with extrahepatic complica-

tions. The majority of KPLA is caused by capsular serotype K1 and K2 isolates. We report a case of carbapenem resis-

tant Klebsiella pneumoniae liver abscess. The patient initially presented with infected right above-the-knee amputation

and was later found with a large liver abscess. Initial antimicrobial susceptibility showed carbapenem resistant K. pneu-

moniae (CRKP). Further molecular workup revealed that the isolate was a less virulent non-K1/K2 serotype, and both

rmpA and kfu genes were negative. The lack of outer membrane porins likely contributed to the carbapenem resistance.

To our knowledge, this is a first reported case of carbapenem resistant, non-K1/K2 serotype K. pneumoniae liver ab-

scess in the United States.

Keywords: Liver Abscess; Klebsiella pneumoniae; Capsular Serotype; Carbapenem Resistance

1. Introduction

Klebsiella pneumoniae liver abscess (KPLA) has been

described as an invasive syndrome with extrahepatic

complications via hematologic spread. The hypermu-

coviscosity phenotype and capsular serotype (K1 and K2)

are the major virulence factors, along with capsular

polysaccharide synthesis regulator gene rmpA, iron che-

lator aerobactin, and iron uptake gene kfu, which have

been described to contribute to the virulence and invasive

features of K. pneumoniae [1-3]. To our knowledge, we

describe the first case of non-K1/K2 KPLA in the United

States.

2. Case Report

A 64-year-old African American man presented to the

Veterans Affairs New Jersey Healthcare System with an

infected right above-the-knee amputation (AKA). The

patient’s hospital course was complicated by poor wound

healing, wound debridement, revision of the AKA, and a

urinary tract infection with Pseudomonas aeruginosa and

Klebsiella pneumoniae, for which he was treated with

doripenem. After one and a half month of hospitalization,

the right AKA began to heal appropriately. On hospital

day 49, the patient developed transient right upper quad-

rant abdominal pain. He then developed intermittent fe-

vers ranging from 100.7˚F to 101˚F, however fever

workup including blood and urine cultures, as well as

chest X-ray were negative. The patient did not have any

further physical complaints and remained hemodynami-

cally stable.

On hospital day 57, the patient was febrile (tempera-

ture, 102˚F), with a heart rate of 121 beats per minute

and blood pressure of 155/77 mm·Hg. The physical ex-

amination was unremarkable including normal thoracic

and abdominal findings. The white cell count was 19,600

cell/μL with 90 percent neutrophils; the hemoglobin level

was 8.5 g/dL, and the platelet count was 377,000 cell/μL.

The aspartate aminotransferase and alanine aminotrans-

ferase were mildly elevated, 38 IU/L and 51 IU/L, re-

spectively. The total bilirubin level was 0.6 mg/dL. A

computerized axial tomography scan of the thorax and

abdomen showed a large loculated abscess in the right

lobe of the liver and intrahepatic biliary ductal dilatation

(Figure 1). Piperacillin-tazobactam was started empiri-

cally, and the patient underwent fine-needle aspiration of

the liver abscess and pigtail placement by interventional

radiology. Culture of the liver abscess grew carbapenem

A Case of Carbapenem Resistant Non-K1/K2 Serotype Klebsiella pneumoniae Liver Abscess

220

resistant Klebsiella pneumoniae (CRKP), which prompted

change of antibiotic therapy to tigecycline. Follow up

computerized axial tomography of the abdomen at the

end of two week treatment showed significantly dimin-

ished liver abscess. However, there was communication

between the abscess and the gallbladder. The patient un-

derwent laparoscopic cholecystectomy. He remained

asymptomatic and was discharged to a nursing home.

Antimicrobial susceptibility of the CRKP isolate was

determined by using the broth microdilution test [4], ex-

cept for that of ertapenem, which was determined by

E-test strip. MICs are as follows: ceftazidime, >128

μg/mL; ceftriaxone, 128 μg/mL; cefepime, >16 μg/mL;

ciprofloxacin, >2 μg/mL; gentamicin, 16 μg/mL; ertap-

enem, 6 μg/mL; imipenem, 1 μg/mL; and meropenem,

<1 μg/mL. Capsular serotyping of the isolate was per-

formed as previously described [5,6], and it was a

non-K1/K2 serotype. Serum bactericidal assay [7], neu-

trophil phagocytosis [8,9], and mice lethality studies

were performed. All animal care procedures and proto-

cols were approved by the Institutional Animal Care and

Use Committee of the National Health Research Institute

(NHRI-IACUC-096004-A). Susceptibility to serum kill-

ing and neutrophil phagocytosis, and LD50 ≥ 1 × 107

CFU were consistent with the less virulent non-K1/K2

serotype. The colonies were phenotypically mucoid but

string test negative.

Polymerase chain reaction (PCR) for rmpA, kfu, aero-

bactin, SHV β-lactamase, and K. pneumoniae carbap-

enemase (KPC) genes were performed as previously de-

scribed [10]. rmpA, aerobactin, and kfu genes were not

present in the isolate. SHV-11 and SHV-12 genes were

detected. The KPC gene was not detected. The outer

membrane porins (OMPs) were isolated according to the

rapid procedure of Chen et al. [11]. OMPs were extracted

with sodium lauroylsarcosinate (Sigma) and recovered

by ultracentrifugation as described previously [12]. The

OMP profiles were determined by sodium dodecyl sul-

Figure 1. Computerized axial tomography of the abdomen

showed a loculated abscess in the right lobe of the liver.

phate-polyacrylamide gel electrophoresis (SDS-PAGE)

using 12% SDS gels and were visualized by Coomassie

blue staining (Figure 2). Neither OmpK35 nor OmpK36

were present.

Pulsed-field gel electrophoresis (PFGE) and multilo-

cus sequence typing (MLST) of the CRKP isolate and

two other known KPC positive CRKP isolates from the

same institution were done as previously described

[13-17] (Figure 3). Sequence type (ST) 258 was identi-

fied in all three isolates.

3. Discussion

In the past two decades, Klebsiella pneumoniae has be-

come the primary cause of liver abscess in Southeast

Asia, including South Korea and Taiwan [18]. There is

also increasing incidence in North America with the ma-

jority of patients being of Asian descent [19,20]. KPLA

has been described as an invasive syndrome as it can

cause extrahepatic complications via hematologic spread.

The major virulence factors in KPLA are the hyper-

mucoviscosity phenotype and capsular serotype (K1 and

K2). The presence of hypermucoviscosity is confirmed

by a positive string test. Isolates of capsular serotype

K1/K2 are the most prevalent serotypes found in KPLA,

accounting for more than seventy percent of liver abscess

strains reported [1-3]. There have been several case re-

ports of confirmed K1 and K2 serotype liver abscesses in

the United States [21,22]. Due to impaired neutrophil

phagocytosis, K1/K2 serotypes are found exclusively in

disseminated cases [18]. Other virulence factors, such as

capsular polysaccharide synthesis regulator gene rmpA,

iron chelator aerobactin, and iron uptake gene kfu, have

been described to contribute to the virulence and invasive

features of K. pn eumoniae . Even though isolates of

non-K1/K2 serotypes are less virulent, the presence of

hypermucoviscosity phenotype, rmpA, aerobactin, and

kfu genes in these isolates make them capable of causing

13883 CRKP J220 M594

OmpK35

OmpK36

Figure 2. Outer membrane profiles of the case CRKP iso-

late and two other known CRKP isolates from the same

institution, J220 and M594. Lane 1, ATCC13883, is the

control strain with only intrinsic resistance to ampicillin.

Neither OmpK35 nor OmpK36 are presented in the case

isolate.

A Case of Carbapenem Resistant Non-K1/K2 Serotype Klebsiella pneumoniae Liver Abscess 221

Figure 3. Pulsed-field gel electrophoresis of the case CRKP

isolate and two other known CRKP isolates. All three iso-

lates are clonally related.

liver abscesses [1]. However, these virulent factors were

not present in the case isolate. To our knowledge, there

has not been a case of nosocomial liver abscess caused

by a non-K1/K2 serotype K. pneumoniae reported in the

United States.

Cephalosporin or combination therapy has been used

to treat KPLA. Liver abscesses caused by extended spec-

trum β-lactamase (ESBL)-producing K. pneumoniae are

uncommon [18]. Carbapenems are the antibiotic main-

stay of treatment for organisms harboring ESBLs.

However, with the emergence of CRKP and particu-

larly the epidemic in the northeastern United States,

treatment options are limited to colistin and tigecycline

[23]. Both β-lactamase genes, SHV-11 and SHV-12,

were identified in the case isolate. PFGE and MLST of

the case isolate and two known KPC positive CRKP iso-

lates from the same institution showed that the isolates

are clonally related, with all three isolates displaying

sequence type 258. The KPC gene however, was not de-

tected in the case isolate. We suspect that it may have

been lost due to plasmid instability during storage. Our

patient received two weeks of tigecycline, however his

uneventful recovery was largely due to mechanical re-

moval of the liver abscess via percutaneous drainage.

In addition to the production of carbapenemase, defi-

ciency in outer membrane porins has been proposed to

increase carbapenem resistance [24]. Most ESBL-pro-

ducing K. pneumoniae strains have only OmpK36,

whereas the majority of non-ESBL-producing K. pneu-

moniae have both OmpK35 and OmpK36. As with our

case isolate, mutant strains with double deletion of

OmpK35 and OmpK36 have been found to have in-

creased antimicrobial resistance but decreased virulence

due to weakened metabolic fitness and slowed growth

rate [24]. This most likely was attributed to the case iso-

late’s high ertapenem MIC despite being KPC negative.

Despite the low virulence of non-K1/K2 serotypes of

K. pneumoniae, they are capable of causing liver abscess

due to presence of hypermucoviscosity phenotype, rmpA,

aerobactin, and kfu genes. To our knowledge, this is the

first reported case of non-K1/K2 serotype KPLA in the

United States. Commonly associated virulence factors

were also absent in this isolate. With increasing antim-

icrobial resistance, health care providers should be aware

of the emergence of CRKP liver abscesses and use ap-

propriate antimicrobial agents when multidrug resistant

organisms are suspected.

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