Liver Abscess Caused by Klebsiella pneumoniae in Siblings

Abstract

Klebsiella pneumoniae has been emerging as the leading cause of liver abscess in diabetic patients. Results of molecular typing of K. pneumoniae isolates from two siblings with liver abscess, their family members, and the environment suggest a possibility of cross infection of liver abscess by the fecal-oral route within diabetic patients.

Klebsiella pneumoniae has been emerging as the leading cause of liver abscess in Taiwan (12, 14). Most of the patients with K. pneumoniae liver abscess are diabetics without preexisting biliary diseases (12). A similar situation has been reported in other countries such as the United States, Japan, and Singapore (2, 9, 10, 13, 15). Some patients with liver abscess have developed serious extrahepatic complications such as endophthalmitis, meningitis, lung abscess, and necrotizing fasciitis (1, 6, 12, 13). The high morbidity associated with K. pneumoniae liver abscess has made it imperative to elucidate the epidemiology of this opportunist and to limit its spread among diabetic patients. However, the source of acquisition and mode of transmission have never been clearly ascertained to date. Transmission through close contact has been suggested, on the basis of identification of a major cluster of K. pneumoniae isolates from patients with liver abscess (5). Nevertheless, transmission between individuals has not previously been documented, and therefore, optimal measures for isolation of infected patients remain unavailable. We herein report on the use of infrequent-restriction-site PCR (IRS-PCR) and pulsed-field gel electrophoresis (PFGE) to investigate K. pneumoniae liver abscesses that occurred consecutively in two siblings.

Patient 1 was a 13-year-old boy with Cooley's anemia who was hospitalized after presenting with abdominal pain and fever. The patient had been on a hypertransfusion program since early childhood. Despite receiving iron-chelating therapy, he still developed hemochromatosis, for which he had received a splenectomy in our hospital 1 year before. He also developed diabetes several weeks prior to this admission. The diagnosis of liver abscess was confirmed by a computer tomography scan. Percutaneous drainage of the abscess by the insertion of a catheter was performed. Cultures of both blood and pus specimens grew K. pneumoniae.

Patient 2, patient 1's elder sister, was an 18-year-old girl with Cooley's anemia. She had been receiving regular blood transfusions for many years. She also suffered from diabetes because of insufficient iron-chelating therapy. One and a half years after the onset of illness in her brother, this patient developed a liver abscess. Culture of pus drained by a catheter yielded K. pneumoniae.

To investigate the source of the K. pneumoniae that caused liver abscess in the two siblings, 21 K. pneumoniae isolates, including 7 from the two patients, 3 from their parents, 6 from unrelated patients with liver abscess (1 isolate), peritonitis (1 isolate), or bacteremia (4 isolates), and 5 from the environment, were analyzed (Table 1). Once a fecal sample was positive for K. pneumoniae, as many as 10 colonies would be collected for molecular analysis and antimicrobial susceptibility testing. We were unable to isolate any K. pneumoniae organisms from feces of patient 2 after she had completed 6 weeks of antimicrobial therapy. All K. pneumoniae isolates were identified according to standard methods (3). A standard disk diffusion method was used to investigate the antimicrobial susceptibility of K. pneumoniae isolates according to the current recommendations of the National Committee for Clinical Laboratory Standards (8).

TABLE 1.

Bacterial strains and results of molecular typing

Strain no.	Source	Specimen	Typing result
			Antibiograma	PFGE	IRS-PCR
1	Patient 2	Pus	I	A	A
2	Patient 1	Blood	I	A	A
3	Patient 2	Feces	I	A	A
4	Patient 2	Feces	II	B	B
5	Patient 2	Feces	I	C	C
6	Patient 1	Feces	I	D	D
7	Patient 1	Feces	I	E	E
8	Father	Feces	I	F	F
9	Mother	Feces	I	G	G
10	Mother	Feces	III	H	H
11	Unrelated patient	Blood	I	I	I
12	Unrelated patient	Blood	I	J	J
13	Unrelated patient	Blood	I	K	K
14	Unrelated patient	Blood	I	L	L
15	Unrelated patient	Blood	I	M	M
16	Unrelated patient	Ascites	I	N	N
17	Water reservoir	Swab	I	O	O
18	Water reservoir	Swab	I	P	P
19	Water reservoir	Swab	I	Q	Q
20	Water reservoir	Swab	I	R	R
21	Water reservoir	Swab	I	S	S

^aI, resistant to ampicillin only; II, resistant to ampicillin and sulfamethoxazole-trimethoprim; III, susceptible to all antimicrobial agents tested. 

The clonal relation between individual isolates was assessed by PFGE and IRS-PCR as previously described (4, 7). To ensure the reproducibility of the method, each isolate was examined twice. The criteria proposed by Tenover et al. (11) were employed to analyze the DNA fingerprints generated by both PFGE and IRS-PCR.

The two methods showed the same efficiency in ascertaining strain identity and discriminating genetically distinct strains. Both demonstrated that the K. pneumoniae clinical strain recovered from patient 2 was the same as that obtained from patient 1 (Fig. 1). There were two different DNA fingerprint patterns among the fecal isolates of patient 1 and three patterns among the isolates from patient 2. One of the three DNA fingerprints of the fecal isolates and the liver abscess isolate from patient 2 appeared identical (Fig. 1). As shown in Table 1, none of the other isolates tested had a pattern that was similar to those of the isolates derived from patients 1 and 2. Antimicrobial susceptibility profiles were identical for most of the isolates.

FIG. 1.

DNA fingerprint patterns in K. pneumoniae isolates from the patients, their family members, unrelated patients, and the environment. DNA fingerprinting was performed by PFGE and IRS-PCR. (A) PFGE patterns of XbaI-digested genomic DNA from K. pneumoniae isolates. Lanes 1 to 21 represent isolates 1 to 21, respectively, as shown in Table 1, and lane M represents the lambda DNA concatemer standard. (B) IRS-PCR patterns of the 21 K. pneumoniae isolates. Lanes 1 to 21 represent isolates 1 to 21, respectively, and lane M represents the 20-bp DNA ladder. Band sizes (in base pairs or kilobase pairs) are shown at the left.

This is the first report of K. pneumoniae liver abscess in siblings. Both patients had diabetes, and isolates from the two patients (one from blood and the other from pus) showed identical DNA fingerprints, indicating that these isolates were a single clone. The result supports previous microbiological observations suggestive of the possibility of cross infection of liver abscess within diabetic patients (5). Nevertheless, clinical evidence such as outbreaks within families or hospitals has never been reported. It is possible that the frequency of the vulnerable hosts (diabetes mellitus) is relatively low in the population, making cross infection rare if it ever occurs. Another explanation is that acquisition through close contact with infected patients or contaminated environments may be just the primary means by which K. pneumoniae liver abscess can occur. Risk factors for diabetic patients developing liver abscess following colonization remain unknown, although poorly controlled hyperglycemia or diabetic ketoacidosis has been implicated (12). In this study, the secondary patient (sister) could have been colonized with the strain from the first patient (brother) through household contact earlier, while the liver abscess did not occur until hemochromatosis worsened and consequent diabetes and hyperglycemia developed.

As mentioned above, a previous study demonstrated that the K. pneumoniae isolates that cause liver abscess in Taiwan form a cluster in terms of their PFGE patterns (5). By a visual comparison, the strains isolated from our patients appeared to belong to cluster A (5). It therefore would be reasonable to speculate that certain unique virulence factors of these isolates might play a role in the pathogenesis of liver abscess in diabetic patients. This hypothesis deserves further study.

This study provides evidence that the strain of K. pneumoniae in the liver abscess originated from the patient's bowel. A possibility is that this strain is endogenous to patient 1, from whom it was transmitted to patient 2. The route of transmission might be fecal-oral. Based on the results of this study, we suggest that unnecessary contact by diabetic patients with liver abscess patients should be avoided.