Klebsiella pneumoniae isolates causing liver abscess in Taiwan

Development of Klebsiella pneumoniae Capsule Polysaccharide-Conjugated Vaccine Candidates Using Phage Depolymerases

Klebsiella pneumoniae is an important pathogen associated with nosocomial infection and has developed increasing resistance to antibiotics such as extended-spectrum β-lactams and carbapenem. In recent years, K. pneumoniae isolates have emerged as a major cause of global community-acquired infections such as pneumonia and pyogenic liver abscess. Although serotypes K1 and K2 have been identified as the predominant capsular types associated with invasive infections, no K. pneumoniae vaccine is commercially available, probably due to immunogenicity loss in the traditional depolymerization method to obtain capsule polysaccharide (CPS) for the preparation of conjugated vaccine. In this study, we successfully retained immunogenicity by using K1 (K1-ORF34) and K2 (K2-ORF16) CPS depolymerases that were identified from phages to cleave K1 and K2 CPSs into intact structural units of oligosaccharides with intact modifications. The obtained K1 and K2 oligosaccharides were separately conjugated with CRM197 carrier protein to generate CPS-conjugated vaccines. Immunization experiments of mice showed both K1 and K2 CPS-conjugated vaccines induced anti-CPS antibodies with 128-fold and 64-fold increases of bactericidal activities, respectively, compare to mice without vaccinations. Challenge tests indicated that K1 or K2 CPS-conjugated vaccine and divalent vaccine (a mixture of K1 and K2 CPS-conjugated vaccines) protected mice from subsequent infection of K. pneumoniae by the respective capsular type. Thus, we demonstrated K1 and K2 CPS-conjugated vaccines prepared by CPS depolymerases is a promising candidate for developing vaccines against human K. pneumoniae infections.

Serotype and virulence genes of Klebsiella pneumoniae isolated from mink and its pathogenesis in mice and mink

In the study, 15 K. pneumoniae strains were isolated from the mink experiencing respiratory distress in mideastern Shandong province, China, and the prevalence of K. pneumoniae in the sampled mink was 11.9% (15/126). Fourteen (93.33%) of the 15 K. pneumoniae isolates were identified as serotype K2 and hypermucoviscosity phenotype. The 12 virulence-associated genes of the K. pneumoniae isolates were tested. The prevalence of the wabG gene for the isolates were 100% (15/15), the ureA gene 100% (15/15), the rmpA gene 93.33% (14/15), the aerobactin gene 93.33% (14/15), the uge gene 93.33% (14/15), the IucB gene 80% (12/15) and the ybtA gene 13.33% (2/15). But the other five genes, fim, iroNB, wcaG, alls and kfuBC, gave a negative PCR reaction in the 15 isolates, respectively. The animal experiments using K. pneumoniae-SD-12 and K. pneumoniae-SD-21 demonstrated that the serotype K2 was high virulence for mice and mink. These finding implied there exist potential threat that K. pneumoniae pathogens could transmit to human, especially the fur animal farm workers and residents lived near the fur animal farms. Therefore, the etiology and epidemiological surveillance of K. pneumoniae in mink should be strengthened for people's public health.

Two T7-like Bacteriophages, K5-2 and K5-4, Each Encodes Two Capsule Depolymerases: Isolation and Functional Characterization

Two Klebsiella bacteriophages K5-2 and K5-4, which are able to infect and grow on either capsular types K30/K69 and K5 or K8 and K5 of Klebsiella strains, were isolated and characterized. Each phage contained two open reading frames (ORFs), which encoded two putative capsule depolymerases, respectively. The first ORF encoded tail fiber proteins, which have K30/K69 depolymerase and K8 depolymerase activities. The second ORF encoded hypothetical proteins, which are almost identical in amino acid sequences, and have K5 depolymerase activity. Alcian blue staining of enzyme-treated capsular polysaccharides (CPS) showed that purified depolymerases can cleave purified Klebsiella CPS in vitro and liberate monosaccharaides. Capsule K5 deletion mutants were not lysed by either phage, suggesting that the capsule was essential for phage infection. Bacterial killing was observed when incubated Klebsiella strains with phages but not with purified depolymerases. Treatment with the K5-4 phage significantly increased the survival of mice infected with a K. pneumoniae K5 strain. In conclusion, two dual host-specific Klebsiella phages and their tailspikes exhibit capsule depolymerase activity were characterized. Each phage and phage-encoded depolymerase has specificity for capsular type K30/K69, K8 or K5, and could be used for the typing and treatment of K. pneumoniae infection.

Septicemic invasive Klebsiella pneumoniae infection in a cynomolgus monkey (Macaca fascicularis) with severe diffused suppurative meningoencephalitis

A 2-year-old male cynomolgus monkey (Macaca fascicularis) showed neurological symptoms during quarantine for importation into Japan, and was euthanized due to poor prognosis. Gross anatomical examination revealed a hemorrhagic lesion around the lateral ventricle in the cerebrum. Histologically, severe diffused suppurative meningitis and ventriculitis were detected with numerous Gram-negative bacilli in the cerebrum. Immunohistochemically, the bacilli were positively stained with an antibody against Klebsiella pneumoniae. The bacterium was isolated from the liver, and it was confirmed to be K. pneumoniae by 16S rDNA sequencing. The isolate displayed a hypermucoviscosity phenotype, was positive for the rmpA and k₂A genes, and demonstrated multidrug resistance. These results suggest that invasive K. pneumoniae can cause septicemic infection, characterized by severe diffused suppurative meningoencephalitis in monkeys.

Herpes zoster correlates with pyogenic liver abscesses in Taiwan

OBJECTIVE

The purpose of the paper was to explore the relationship between herpes zoster and pyogenic liver abscesses in Taiwan.

METHODS

This was a nationwide cohort study. Using the database of the Taiwan National Health Insurance Program, there were 33049 subjects aged 20-84 years who were newly diagnosed with herpes zoster from 1998 to 2010 that were selected for our study, and they were our herpes zoster group. 131707 randomly selected subjects without herpes zoster were our non-herpes zoster group. Both groups were matched by sex, age, other comorbidities, and the index year of their herpes zoster diagnosis. The incidence of pyogenic liver abscesses at the end of 2011 was then estimated. The multivariable Cox proportional hazard regression model was used to estimate the hazard ratio and 95% confidence interval for pyogenic liver abscesses associated with herpes zoster and other comorbidities.

RESULTS

The overall incidence rate was 1.38-fold higher in the herpes zoster group than in the non-herpes zoster group (4.47 vs. 3.25 per 10000 person-years, 95% confidence interval 1.32, 1.44). After controlling for potential confounding factors, the adjusted hazard ratio of pyogenic liver abscesses was 1.34 in the herpes zoster group (95% confidence interval 1.05, 1.72) when compared with the non-herpes zoster group. Sex (in this case male), age, presence of biliary stones, chronic kidney diseases, chronic liver diseases, cancers, and diabetes mellitus were also significantly associated with pyogenic liver abscesses.

CONCLUSIONS

Patients with herpes zoster are associated with an increased hazard of developing pyogenic liver abscesses.

Bacteremic community-acquired infections due to Klebsiella pneumoniae: clinical and microbiological presentation in New Caledonia, 2008-2013

OBJECTIVES

To provide data on severe bacteremic community-acquired infections due to Klebsiella pneumoniae in New Caledonia.

METHODS

All patients admitted with bacteremic community-acquired infections due to K. pneumoniae at the only tertiary medical center in New Caledonia, from 2008 to 2013, were included retrospectively in this study. Clinical and microbiological characteristics were analyzed, as well as risk factors for mortality.

RESULTS

The characteristics of 119 patients were analyzed. The most common clinical presentation was urinary tract infection (40 cases, 33%), followed by pneumonia (28 cases, 23%), deep abscesses (15 cases, 13%), liver abscess (12 cases, 9%), meningitis in (five cases, 4%), and endophthalmitis (two cases, 1%). Multiple localizations were reported in 18 cases (15%) and isolated bacteremia was reported in 22 cases (18%). The overall mortality rate was 22% (26/119) and the mortality rate in the intensive care unit was 33% (14/42). Renal impairment, chronic liver disease, pneumonia, and isolated bacteremia were independent risk factors for mortality.

CONCLUSIONS

K. pneumoniae is a dominant cause of severe community-acquired bacteremic infection in New Caledonia. Physicians should be aware of the poor prognosis of any patient with a bacteremic K. pneumoniae infection and should monitor patients presenting with risk factors closely.

Protection against Klebsiella pneumoniae using lithium chloride in an intragastric infection model

Intragastric Klebsiella pneumoniae infections of mice can cause liver abscesses, necrosis of liver tissues, and bacteremia. Lithium chloride, a widely prescribed drug for bipolar mood disorder, has been reported to possess anti-inflammatory properties. Using an intragastric infection model, the effects of LiCl on K. pneumoniae infections were examined. Providing mice with drinking water containing LiCl immediately after infection protected them from K. pneumoniae-induced death and liver injuries, such as necrosis of liver tissues, as well as increasing blood levels of aspartate aminotransferase and alanine aminotransferase, in a dose-dependent manner. LiCl administered as late as 24 h postinfection still provided protection. Monitoring of the LiCl concentrations in the sera of K. pneumoniae-infected mice showed that approximately 0.33 mM LiCl was the most effective dose for protecting mice against infections, which is lower than the clinically toxic dose of LiCl. Surveys of bacterial counts and cytokine expression levels in LiCl-treated mice revealed that both were effectively inhibited in blood and liver tissues. Using in vitro assays, we found that LiCl (5 μM to 1 mM) did not directly interfere with the growth of K. pneumoniae but made K. pneumoniae cells lose the mucoid phenotype and become more susceptible to macrophage killing. Furthermore, low doses of LiCl also partially enhanced the bactericidal activity of macrophages. Taken together, these data suggest that LiCl is an alternative therapeutic agent for K. pneumoniae-induced liver infections.

Identification of an immuno-dominant protein from Klebsiella pneumoniae strains causing pyogenic liver abscess: implication in serodiagnosis

Background

Klebsiella pneumoniae has emerged worldwide as a cause of pyogenic liver abscess (PLA) often complicated by meningitis and endophthalmitis. Early detection of this infectious disease will improve its clinical outcome. Therefore, we tried to isolate immunodominant proteins secreted by K. pneumoniae strains causing PLA.

Results

The secreted proteins of the NTUH-K2044 strain were separated by two-dimensional electrophoresis and then immunoblotted using convalescent sera from patients with K. pneumoniae PLA. A ~30-kDa immunodominant protein was then identified. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) revealed an open reading frame (KP1_p307) located on the pK2044 plasmid and bioinformatic analysis identified this protein as a signal peptide of unknown function. The KP1_p307 gene was more prevalent in PLA strains and capsular type K1/K2 strains, but disruption of this gene in NTUH-K2044 strain did not decrease virulence in mice. Ten of fourteen (71%) sera from patients with K. pneumoniae PLA were immunoreactive with the recombinant KP1_p307 protein. Seroconversion demonstrated by a rise in serum titer in serial serum samples confirmed that antibodies against the KP1_p307 protein were elicited after infection.

Conclusions

The KP1_p307 protein could be used as an antigen for early serodiagnosis of K. pneumoniae PLA, particularly in K1/K2 PLA strains.

Isolation of a bacteriophage and its depolymerase specific for K1 capsule of Klebsiella pneumoniae: implication in typing and treatment

BACKGROUND

Klebsiella pneumoniae causing community-acquired pyogenic liver abscess complicated with metastatic meningitis and endophthalmitis has emerged recently, most frequently associated with the K1 capsular type.

METHODS

A bacteriophage (NTUH-K2044-K1-1) that infects K. pneumoniae NTUH-K2044 (capsular type K1) was isolated and characterized.

RESULTS

The phage infected all K1 strains, and none of the strains with other capsular types. Capsule deletion mutants were not lysed by this phage, suggesting that the capsule was essential for phage infection. Complete genome sequencing revealed the phage was a novel phiKMV-like virus. The gene-encoding capsule depolymerase was identified. The recombinant enzyme demonstrated specific lysis of the K1 capsule. Treatment with the phage or the recombinant enzyme provided significantly increased survival in mice infected with NTUH-K2044 strain, including one treated after the detection of a neck abscess by imaging. No obvious disease was observed after administration of this phage in mice. Phage was retained at detectable levels in liver, spleen, brain, and blood 24 hours after administration in mice.

CONCLUSIONS

These results demonstrate this phage and its capsule depolymerase exhibit specificity for capsular type K1 and can be used for the diagnosis and treatment of K1 K. pneumoniae infections.

An Increasing Prominent Disease of Klebsiella pneumoniae Liver Abscess: Etiology, Diagnosis, and Treatment

Background. During the past two decades, Klebsiella pneumoniae (K. pneumoniae) had surpassed Escherichia coli (E. coli) as the predominant isolate from patients with pyogenic liver abscess (PLA) in Asian countries, the United States, and Europe, and it tended to spread globally. Since the clinical symptom is atypical, the accurate and effective diagnosis and treatment of K. pneumoniae liver abscesses (KLAs) are very necessary. Methods. Here, we have comprehensively clarified the epidemiology and pathogenesis of KLA, put emphases on the clinical presentations especially the characteristic radiographic findings of KLA, and thoroughly elucidated the most effective antibiotic strategy of KLA. Results. K1 serotype is strongly associated with KLA especially in diabetic patients. Computed tomography (CT) and ultrasound (US) were two main diagnostic methods of KLA in the past. Most of KLAs have solitary, septal lobular abscesses in the right lobe of liver, and they are mainly monomicrobial. Broad-spectrum antibiotics combined with the US-guided percutaneous drainage of liver abscesses can increase their survival rates, but surgical intervention still has its irreplaceable position. Conclusion. The imaging features contribute to the early diagnosis, and the percutaneous intervention combined with an aminoglycoside plus either an extended-spectrum betalactam or a second- or third-generation cephalosporin is a timely and effective treatment of KLA.

Isolation of a bacteriophage specific for a new capsular type of Klebsiella pneumoniae and characterization of its polysaccharide depolymerase

BACKGROUND

Klebsiella pneumoniae is one of the major pathogens causing hospital-acquired multidrug-resistant infections. The capsular polysaccharide (CPS) is an important virulence factor of K. pneumoniae. With 78 capsular types discovered thus far, an association between capsular type and the pathogenicity of K. pneumoniae has been observed.

METHODOLOGY/PRINCIPAL FINDINGS

To investigate an initially non-typeable K. pneumoniae UTI isolate NTUH-K1790N, the cps gene region was sequenced. By NTUH-K1790N cps-PCR genotyping, serotyping and determination using a newly isolated capsular type-specific bacteriophage, we found that NTUH-K1790N and three other isolates Ca0507, Ca0421 and C1975 possessed a new capsular type, which we named KN2. Analysis of a KN2 CPS(-) mutant confirmed the role of capsule as the target recognized by the antiserum and the phage. A newly described lytic phage specific for KN2 K. pneumoniae, named 0507-KN2-1, was isolated and characterized using transmission electron microscopy. Whole-genome sequencing of 0507-KN2-1 revealed a 159 991 bp double-stranded DNA genome with a G+C content of 46.7% and at least 154 open reading frames. Based on its morphological and genomic characteristics, 0507-KN2-1 was classified as a member of the Myoviridae phage family. Further analysis of this phage revealed a 3738-bp gene encoding a putative polysaccharide depolymerase. A recombinant form of this protein was produced and assayed to confirm its enzymatic activity and specificity to KN2 capsular polysaccharides. KN2 K. pneumoniae strains exhibited greater sensitivity to this depolymerase than these did to the cognate phage, as determined by spot analysis.

CONCLUSIONS/SIGNIFICANCE

Here we report that a group of clinical strains possess a novel Klebsiella capsular type. We identified a KN2-specific phage and its polysaccharide depolymerase, which could be used for efficient capsular typing. The lytic phage and depolymerase also have potential as alternative therapeutic agents to antibiotics for treating K. pneumoniae infections, especially against antibiotic-resistant strains.

The diabetic ocular environment facilitates the development of endogenous bacterial endophthalmitis

PURPOSE

We tested the hypothesis that changes in the diabetic ocular environment facilitate the development of endogenous bacterial endophthalmitis (EBE).

METHODS

C57BL/6J mice were rendered diabetic with streptozotocin (STZ) for 1, 3, or 5 months' duration. Diabetic and age-matched nondiabetic mice were tail vein-injected with 10(8) CFU of Klebsiella pneumoniae, a common cause of EBE in diabetics. After either 2 or 4 days postinfection, the EBE incidence was assessed by electroretinography, histology, bacterial counts, and myeloperoxidase ELISAs. Blood-retinal barrier (BRB) permeability in uninfected diabetic mice also was determined.

RESULTS

No cases of EBE were observed among the 1-month diabetic group. Extending the time from diabetes induction to 3 months resulted in a 23.8% EBE incidence after 2 days, and a 22% incidence after 4 days. The incidence of EBE increased to 27% in the 5-month diabetic group. Infected eyes had an average 8.01 × 10(2) and 6.19 × 10(4) CFU/eye for the 3- and 5-month diabetic groups, respectively. There was no significant difference in BRB permeability between control and 1-month uninfected diabetic mice. However, 3- and 5-month diabetic mice had significantly greater BRB permeability than control mice. These results suggested that increasing the time from STZ diabetes induction to 3 and 5 months resulted in an ocular environment more conducive to the development of EBE.

CONCLUSIONS

These results demonstrated a correlation between an increase in BRB permeability and an increase in EBE incidence, supporting the hypothesis that diabetic ocular changes contribute to the development of EBE.

Biofilm formation and Klebsiella pneumoniae liver abscess: true, true and unrelated?

Klebsiella pneumoniae liver abscess is an emerging infectious disease. This syndrome was unknown before the late 1980s when it was first recognized in Taiwan. Over the next two decades it increased in prevalence in Taiwan and was reported from other nations of East Asia. It was then that the rest of the world became aware of this interesting new syndrome. The disease is no longer confined to East Asia, and is now an emerging infection in North America and Europe. How did this come about? We now understand some of the genetic changes that turn commensal E. coli into extra-intestinal pathogens. K pneumoniae is another member of the Enterobacteriaceae that is usually normal flora in the gut, but we know relatively little about how it evolved into an invasive pathogen capable of causing abscesses in normal livers. The phenotype of the liver-invasive strains is hyperviscosity of the polysaccharide capsules, but while the gene that determines that property is required it is not sufficient to create the pathogen, and more research is needed to discover the other virulence genes, and thus to potentially target them therapeutically.

Seroepidemiology of Klebsiella pneumoniae colonizing the intestinal tract of healthy Chinese and overseas Chinese adults in Asian countries

Background

Capsular serotypes K1 and K2 of Klebsiella pneumoniae are thought to the major virulence determinants responsible for liver abscess. The intestine is one of the major reservoirs of K. pneumoniae, and epidemiological studies have suggested that the majority of K. pneumoniae infections are preceded by colonization of the gastrointestinal tract. The possibility of fecal-oral transmission in liver abscess has been raised on the basis of molecular typing of isolates. Data on the serotype distribution of K. pneumoniae in stool samples from healthy individuals has not been previously reported. This study investigated the seroepidemiology of K. pneumoniae isolates from the intestinal tract of healthy Chinese in Asian countries. Stool specimens from healthy adult Chinese residents of Taiwan, Japan, Hong Kong, China, Thailand, Malaysia, Singapore, and Vietnam were collected from August 2004 to August 2010 for analysis.

Results

Serotypes K1/K2 accounted for 9.8% of all K. pneumoniae isolates from stools in all countries. There was no significant difference in the prevalence of K1/K2 isolates among the countries excluding Thailand and Vietnam. The antimicrobial susceptibility pattern was nearly the same in K. pneumoniae isolates. The result of pulsed-field gel electrophoresis revealed no major clonal cluster of serotype K1 isolates.

Conclusions

The result showed that Chinese ethnicity itself might be a major factor predisposing to intestinal colonization by serotype K1/K2 K. pneumoniae isolates. The prevalent serotype K1/K2 isolates may partially correspond to the prevalence of K. pneumoniae liver abscess in Asian countries.

The role of Klebsiella pneumoniae rmpA in capsular polysaccharide synthesis and virulence revisited

Klebsiella pneumoniae community-acquired pyogenic liver abscess (PLA) is an emerging infectious disease. The rmpA gene (for regulator of mucoid phenotype A) has been reported to be associated with PLA in prevalence studies. NTUH-K2044, a K1 PLA isolate, carries three rmpA/A2 genes: two large-plasmid-carried genes (p-rmpA and p-rmpA2) and one chromosomal gene (c-rmpA). In this study, we re-examined the role of rmpA/A2 in PLA pathogenesis to clarify the relationship of rmpA/A2 and capsular serotype to virulence. Using isogenic gene deletion strains and complemented strains of NTUH-K2044, we demonstrated that only p-rmpA enhanced expression of capsular polysaccharide synthesis (cps) genes and capsule production. Nevertheless, the lethal dose and in vivo competitive index indicated that p-rmpA does not promote virulence in mice. The prevalence of these three rmpA/A2 and capsular types in 206 strains was investigated. This revealed a correlation of rmpA/A2 with six PLA-related capsular types (K1, K2, K5, K54, K57 and KN1). However, the correlation of rmpA/A2 with K1 strains from the West was less obvious than with the strains from Asia (17/22 vs 39/39, P = 0.0019). Among the three rmpA/A2 genes, p-rmpA was the most prevalent. Due to the strong correlation with PLA-related capsular types, p-rmpA could serve as a surrogate marker for PLA. We found an association of p-rmpA with three widely spaced loci in a large plasmid (30/32). Therefore, rmpA could be co-inherited together with virulence genes carried by this plasmid.

Isolation of genes involved in biofilm formation of a Klebsiella pneumoniae strain causing pyogenic liver abscess

BACKGROUND

Community-acquired pyogenic liver abscess (PLA) complicated with meningitis and endophthalmitis caused by Klebsiella pneumoniae is an emerging infectious disease. To investigate the mechanisms and effects of biofilm formation of K. pneumoniae causing PLA, microtiter plate assays were used to determine the levels of biofilm formed by K. pneumoniae clinical isolates and to screen for biofilm-altered mutants from a transposon mutant library of a K. pneumoniae PLA-associated strain.

METHODOLOGY/PRINCIPAL FINDINGS

The biofilm formation of K. pneumoniae was examined by microtiter plate assay. Higher levels of biofilm formation were demonstrated by K. pneumoniae strains associated with PLA. A total of 23 biofilm-decreased mutants and 4 biofilm-increased mutants were identified. Among these mutants, a biofilm-decreased treC mutant displayed less mucoviscosity and produced less capsular polysaccharide (CPS), whereas a biofilm-increased sugE mutant displayed higher mucoviscosity and produced more CPS. The biofilm phenotypes of treC and sugE mutants also were confirmed by glass slide culture. Deletion of treC, which encodes trehalose-6-phosphate hydrolase, impaired bacterial trehalose utilization. Addition of glucose to the culture medium restored the capsule production and biofilm formation in the treC mutant. Transcriptional profile analysis suggested that the increase of CPS production in ΔsugE may reflect elevated cps gene expression (upregulated through rmpA) in combination with increased treC expression. In vivo competition assays demonstrated that the treC mutant strain was attenuated in competitiveness during intragastric infection in mice.

CONCLUSIONS/SIGNIFICANCE

Genes important for biofilm formation by K. pneumoniae PLA strain were identified using an in vitro assay. Among the identified genes, treC and sugE affect biofilm formation by modulating CPS production. The importance of treC in gastrointestinal tract colonization suggests that biofilm formation contributes to the establishment and persistence of K. pneumoniae infection.

Experimental phage therapy in treating Klebsiella pneumoniae-mediated liver abscesses and bacteremia in mice

Intragastric inoculation of mice with Klebsiella pneumoniae can cause liver abscesses, necrosis of liver tissues, and bacteremia. A newly isolated phage (φNK5) with lytic activity for K. pneumoniae was used to treat K. pneumoniae infection in an intragastric model. Both intraperitoneal and intragastric administration of a single dose of φNK5 lower than 2 × 10(8) PFU at 30 min after K. pneumoniae infection was able to protect mice from death in a dose-dependent manner, but the efficacy achieved with a low dose of φNK5 by intragastric treatment provided the more significant protection. Phage φNK5 administered as late as 24 h after K. pneumoniae inoculation was still protective, while intraperitoneal treatment with phage was more efficient than intragastric treatment as a result of the dissemination of bacteria into the circulation at 24 h postinfection. Surveys of bacterial counts for mice treated with φNK5 by the intraperitoneal route revealed that the bacteria were eliminated effectively from both blood and liver tissue. K. pneumoniae-induced liver injury, such as liver necrosis, as well as blood levels of aspartate aminotransferase and alanine aminotransferase and inflammatory cytokine production, was significantly inhibited by φNK5 treatment. These data suggest that a low dose of φNK5 is a potential therapeutic agent for K. pneumoniae-induced liver infection.

Approach of empirical antibiotic treatment: analyzing bacterial resistance of community-acquired bacteremia

BACKGROUND/PURPOSE

Nosocomial bacterial resistance has been advanced and well studied in Taiwan, but there were few reports describing the antibiotic susceptibility of community-acquired pathogens. Through collecting data from those who received blood cultures in emergency department, we presented an epidemiological study to analyze appropriate empirical therapy for the community-acquired bacteremia in Southern Taiwan.

METHODS

From July 1998 to June 1999, patients presented at emergency department of Kaohsiung Veterans General Hospital with fever, chills or symptoms of sepsis were routinely performed two sets of blood cultures. Those of positive blood cultures without prior admission history to the hospital within 2 weeks were further analyzed for the etiologic pathogens, antibiotic susceptibility, and risk factors of community-acquired bacteremia.

RESULTS

A total of 303 episodes were enrolled for analysis, Escherichia coli, Klebsiella pneumoniae, and Staphylococcus aureus accounted for 76.3% of the isolates. Most of the community-acquired bacteremia was secondary bacteremia. Eighty-four percents of E. coli, 89% of K. pneumoniae, and 76% of S. aureus were susceptible to cefazolin. Susceptible rates of the three major pathogens to gentamicin were 72%, 92%, and 68% respectively.

CONCLUSION

While treating community-acquired bacteremia in Southern Taiwan, the first generation antibiotic, cefazolin plus gentamicin, was effective in vitro for the majority of cases. However, since the community-acquired bacteremia is mostly secondary in origin, it is necessary to explore the underlying primary lesions to attain therapeutic success. Further on-going epidemiological surveillance on bacterial resistance of community-acquired bacteremia is necessary to provide evidence-based appropriateness of empirical therapy.

Phosphoproteomics of Klebsiella pneumoniae NTUH-K2044 reveals a tight link between tyrosine phosphorylation and virulence

Encapsulated Klebsiella pneumoniae is the predominant causative agent of pyogenic liver abscess, an emerging infectious disease that often complicates metastatic meningitis or endophthalmitis. The capsular polysaccharide on K. pneumoniae surface was determined as the key to virulence. Although the regulation of capsular polysaccharide biosynthesis is largely unclear, it was found that protein-tyrosine kinases and phosphatases are involved. Therefore, the identification and characterization of such kinases, phosphatases, and their substrates would advance our knowledge of the underlying mechanism in capsule formation and could contribute to the development of new therapeutic strategies. Here, we analyzed the phosphoproteome of K. pneumoniae NTUH-K2044 with a shotgun approach and identified 117 unique phosphopeptides along with 93 in vivo phosphorylated sites corresponding to 81 proteins. Interestingly, three of the identified tyrosine phosphorylated proteins, namely protein-tyrosine kinase (Wzc), phosphomannomutase (ManB), and undecaprenyl-phosphate glycosyltransferase (WcaJ), were found to be distributed in the cps locus and thus were speculated to be involved in the converging signal transduction of capsule biosynthesis. Consequently, we decided to focus on the lesser studied ManB and WcaJ for mutation analysis. The capsular polysaccharides of WcaJ mutant (WcaJY5F) were dramatically reduced quantitatively, and the LD(50) increased by 200-fold in a mouse peritonitis model compared with the wild-type strain. However, the capsular polysaccharides of ManB mutant (ManBY26F) showed no difference in quantity, and the LD(50) increased by merely 6-fold in mice test. Our study provided a clear trend that WcaJ tyrosine phosphorylation can regulate the biosynthesis of capsular polysaccharides and result in the pathogenicity of K. pneumoniae NTUH-K2044.

Pyogenic liver abscess caused by Klebsiella pneumoniae genetic serotype K1 in Japan

Pyogenic liver abscess caused by Klebsiella pneumoniae is an emerging disease worldwide, and we know the serotype K1 strain to be the most virulent strain. We report a Japanese case of septic pyogenic liver abscess caused by K. pneumoniae genetic serotype K1. A 60-year old man presented at our hospital in a state of cardiopulmonary arrest. From the patient's chief complaint of chest pain, we suspected acute coronary syndrome, i.e., acute myocardial infarction. We used extracorporeal circulation and checked coronary angiography, but the 75% stenosis by itself could not adequately account for the patient's critical condition. The patient's laboratory data indicated multiple organ failure. The patient's condition did not improve while in intensive care and he died 20 h after the onset of the cardiopulmonary arrest. Pathological autopsy later showed colliquative necrosis in the deltoid and left greater pectoral muscles, as well as liver abscesses. The patient's blood, gastric juice, and stool cultures all grew a Gram-negative bacillus identified as Klebsiella pneumoniae. We also performed capsular polysaccharide synthesis (cps) genotyping by polymerase chain reaction for the detection of K serotype-specific alleles at the wzx and wzy loci. The result indicated that wzx_K1 and wzy_K1 were positive. This is the first reported Japanese case of septic pyogenic liver abscess caused by K. pneumoniae genetic serotype K1.

Rapid real-time PCR assays for detection of Klebsiella pneumoniae with the rmpA or magA genes associated with the hypermucoviscosity phenotype: screening of nonhuman primates

The relationship of mucoviscosity-associated (magA) and/or regulator of mucoid phenotype (rmpA) genes to the Klebsiella pneumoniae hypermucoviscosity (HMV) phenotype has been reported. We previously demonstrated that rmpA+ K. pneumoniae can cause serious disease in African green monkeys and isolated rmpA+ and magA+ HMV K. pneumoniae from other species of non-human primates. To rapidly screen African green monkeys/non-human primates for these infections, we developed three real-time PCR assays. The first was K. pneumoniae-specific, targeting the khe gene, while the others targeted rmpA and magA. Primer Express 2 was used with the three K. pneumoniae genes to generate sequence-specific TaqMan/TaqMan-Minor Groove Binder assays. Oral/rectal swabs and necropsy samples were collected; swabs were used for routine culture and DNA extraction. K. pneumoniae colonies were identified on the Vitek 2 with DNA tested using the K. pneumoniae-specific assays. Testing of 45 African green monkeys resulted in 19 khe+ samples from 14 animals with none positive for either rmpA or magA. Of these 19 khe+ samples, five were culture-positive, but none were HMV "string test"-positive. Subsequent testing of 307 non-human primates resulted in 64 HMV K. pneumoniae isolates of which 42 were rmpA+ and 15 were magA+. Non-human primate testing at the U.S. Army Medical Research Institute of Infectious Diseases demonstrated the ability to screen both live and necropsied animals for K. pneumoniae by culture and real-time PCR to determine HMV genotype.

Occult colon cancer in a patient with diabetes and recurrent Klebsiella pneumoniae liver abscess

Klebsiella pneumoniae (Kp) is a well-known leading cause of liver abscess in patients with diabetes, but recurrent Kp liver abscess in such patients within a period of time is seldom seen. Here, we report a patient with diabetes who experienced three episodes of Kp liver abscess within 1 year. The patient was subsequently diagnosed to have an occult sigmoid cancer. The liver abscess did not recur after resection of the colonic tumor. Occult sigmoid colonic cancer may have played an important role in the recurrent Kp liver abscess in our case. Therefore, further investigation of gastrointestinal malignancies, particularly of the colonic tract, is necessary in patients with diabetes and Kp liver abscess.

Predictors of septic metastatic infection and mortality among patients with Klebsiella pneumoniae liver abscess

BACKGROUND

Primary liver abscess caused by Klebsiella pneumoniae is an infection that is emerging worldwide and that is associated with severe morbidity and considerable mortality.

METHODS

A retrospective analysis of 110 episodes of primary liver abscess caused by K. pneumoniae that required hospitalization during 2001-2002 was conducted to identify predictors of metastatic infection, mortality, and the efficacy of first-generation cephalosporins and percutaneous drainage. The potential role of Klebsiella rmpA and magA genes was also evaluated.

RESULTS

The study included 59 men and 51 women, with a mean age of 61.8 years. Diabetes was noted in 67 patients (60.9%). Metastatic infection occurred in 17 patients (15.5%), with meningitis accounting for 11 patients (64.7%) and endophthalmitis accounting for 4 patients (23.5%). The overall mortality rate was 10.0% (11 patients). Most of the severe complications occurred within the first 3 days after hospital admission. Ninety-two patients (83.6%) received treatment with cefazolin for >3 days. Four patients (4.3%) of the group who received cefazolin had metastatic infection, 1 patient (1.1%) experienced septic shock, and 3 (3.3%) experienced acute respiratory failure. Five (5.4%) of those 92 patients died. Multivariable analysis revealed that rmpA (odds ratio [OR], 28.85), Acute Physiologic and Chronic Health Evaluation (APACHE) II score >or=20 (OR, 8.08), and septic shock (OR, 4.33) were statistically significant predictors of metastatic infection. Metastatic infection (OR, 6.73), severity of disease (APACHE II score >or=16; OR, 11.82), septic shock (OR, 8.30), acute respiratory failure (OR, 69.92), and gas formation revealed on imaging (OR, 13.26) predicted mortality. Pigtail drainage protected against both metastatic infection (OR, 0.25) and mortality (OR, 0.14).

CONCLUSION

Management of primary liver abscess caused by K. pneumoniae with use of first-generation cephalosporins and percutaneous drainage was associated with low rates of mortality, metastatic infection, and complications. These rates are comparable to those reported for third-generation cephalosporins.

Correlation between time to positivity of blood cultures with clinical presentation and outcomes in patients with Klebsiella pneumoniae bacteraemia: prospective cohort study

Time to positivity (TTP) of blood cultures in patients with bacteraemia is considered to be a predictor of outcome for some bacterial species. Two hundred and thirty-one patients with Klebsiella pneumoniae monomicrobial bacteraemia at a hospital from 1 January to 31 December 2007 were prospectively enrolled. TTP <7 h (46 patients, 19.9%) was associated with a higher Pittsburg bacteraemia score (6.2 +/- 5.5 vs. 3.7 +/- 4.3, p 0.002), fewer non-fatal diseases by the McCabe classification (39.1% vs. 64.9%, p 0.002), a higher percentage of patients with liver cirrhosis, active malignancy, and chemotherapy within 3 months (28.3% vs. 11.9%, p 0.007; 28.3% vs. 14.6%, p 0.031; 23.9% vs. 5.4%, p <0.001), more primary bacteraemia (45.7% vs. 22.2%, p 0.002), and a higher 30-day mortality rate (47.8% vs. 21.1%, p <0.001). Risk factors for 30-day mortality in the univariate analysis included higher Pittsburg bacteraemia score (5.8 +/- 5.3 vs. 3.7 +/- 4.3, p 0.002), primary bacteraemia (41.0% vs. 21.8%, p 0.004), TTP <7 h (36.1% vs. 14.1%, p <0.001), and the presence of active malignancy (29.5% vs. 12.9%, p 0.004). In the multivariate analysis, higher Pittsburg bacteraemia score (OR 1.07; 95% CI 1.01-1.14), TTP <7 h (OR 2.46; 95% CI 1.20-5.05) and active malignancy (OR 2.21; 95% CI 1.03-4.73) were the significant factors associated with 30-day mortality. In the Kaplan-Meier survival curve, short TTP was significantly associated with mortality at all time-points after admission. TTP of blood cultures, interpreted with a cut-off point of <7 h, in patients with K. pneumoniae bacteraemia can provide useful prognostic information.

Pyogenic liver abscess as endemic disease, Taiwan

Increasing incidence and microbiologic shift might have changed the manifestation of this condition.

Pyogenic liver abscess has become a health problem in Taiwanese society. However, the extent of this problem has remained unclear because of the lack of a population-based study. We therefore performed a nationwide analysis of pyogenic liver abscess in Taiwan from 1996 through 2004. We analyzed 29,703 cases from the Taiwan National Health Insurance database and 506 cases from National Taiwan University Hospital. Our analysis showed that the annual incidence of pyogenic liver abscess increased steadily from 11.15/100,000 population in 1996 to 17.59/100,000 in 2004. Diabetes, malignancy, renal disease, and pneumonia were associated with a higher risk for the disease. By contrast, death due to pyogenic liver abscess decreased over time, although population-based abscess-related death increased slightly. Renal disease, malignancy, pneumonia, and heart disease correlated with higher death rates; Klebsiellapneumoniae infection and therapeutic procedures were related to lower death rates. Diabetes did not significantly change death rates for the 506 patients from the hospital.

Multisystemic abscesses in African green monkeys (Chlorocebus aethiops) with invasive Klebsiella pneumoniae--identification of the hypermucoviscosity phenotype

Invasive Klebsiella pneumoniae is an emerging disease of humans characterized by abscesses in the liver or other sites involving bacteria with the unique hypermucoviscosity phenotype. Over several months, 7 African green monkeys in our research colony developed abscess formation in multiple locations and succumbed to disease. K. pneumoniae was identified by bacterial culture in 6 monkeys and immunohistochemistry in 1 additional monkey. All monkeys had been housed in, or had contact with monkeys housed in, 1 animal room in our facility. All affected monkeys had 1 or more abscesses, most notably in the abdomen, but also affecting the lungs, cerebellum, and skin. Abdominal abscesses and associated adhesions entrapped loops of bowel, forming palpable masses. Abdominal masses were located at the root of the mesentery, the ileocecocolic junction, or the pelvic inlet. In 1 case, culture, serotyping, and polymerase chain reaction (PCR) analysis of the bacterial isolate identified K. pneumoniae expressing the hypermucoviscosity phenotype and capsular serotype K2 and determined that the K. pneumonia was genetically rmpA(+)/magA(-).

Klebsiella pneumoniae liver abscesses in a public hospital in Queens, New York

BACKGROUND

Klebsiella pneumoniae liver abscess has been described frequently in patients residing in Asian countries. With the advent of immigration, this disease has become more common in certain hospitals in the United States, based upon the demographics of their patient populations.

METHODS

We reviewed laboratory and clinical data for patients admitted to a municipal hospital in Queens, New York from 2000 to 2007 via a retrospective chart review.

RESULTS

Of the 56 cases of pyogenic liver abscess reviewed, 20 cases were secondary to Klebsiella pneumoniae, verified via radiographic imaging plus positive blood culture or liver aspiration culture. Of these cases, 60% of patients were of Asian descent. Liver drainage appeared to be the most important modality of treatment. Choice of antibiotics and duration of treatment varied greatly depending upon whether an infectious disease consultant was called or not.

CONCLUSIONS

The majority of community-acquired Klebsiella pneumoniae liver abscess occurred in patients of Asian descent. Many of these patients have not resided in their country of origin for quite some time. In hospitals serving large Asian populations, this diagnosis must be considered and appropriate work-up for metastatic complications should be provided promptly.

Virulence characteristics of Klebsiella and clinical manifestations of K. pneumoniae bloodstream infections

Differences in clinical manifestations are due to virulence factors expressed by the organism.

We studied 455 consecutive episodes of Klebsiella pneumoniae bacteremia occurring in 7 countries. Community-acquired pneumonia and an invasive syndrome of liver abscess, meningitis, or endophthalmitis occurred only in Taiwan and South Africa. Infections by K1 and K2 capsular serotype, the mucoid phenotype, and aerobactin production were important determinants of virulence. The mucoid phenotype was seen in 94% of isolates in patients with community-acquired pneumonia and in 100% of isolates that caused the invasive syndrome in Taiwan and South Africa, compared with only 2% of isolates elsewhere. Mortality of mice injected with mucoid strains (69%) was strikingly higher than that occurring in mice injected with nonmucoid strains (3%, p<0.001). Differences in clinical features of bacteremic infection with K. pneumoniae are due to the virulence factors expressed by the organism.

Characterization of integrative and conjugative element ICEKp1-associated genomic heterogeneity in a Klebsiella pneumoniae strain isolated from a primary liver abscess

Genomic heterogeneity has been shown to be associated with Klebsiella pneumoniae strains causing pyogenic liver abscesses (PLA) and metastatic infections. In order to explore the mechanism responsible for genomic heterogeneity in K. pneumoniae, we compared the complete genomic sequences of strains NTUH-K2044 and MGH78578. An approximately 76-kbp DNA fragment located adjacent to an asparagine (asn) tRNA gene was present in NTUH-K2044 but not in MGH78578. This fragment could be divided into three regions with different functions, and structurally it resembled a functional integrative and conjugative element (ICE), ICEEc1, in Escherichia coli. The 5' region of this fragment contained genes similar to a high-pathogenicity island (HPI) of Yersinia pestis and Yersinia pseudotuberculosis. The middle region was similar to part of a large plasmid in K. pneumoniae, and the 3' region contained genes responsible for DNA conjugative transfer. Therefore, this DNA fragment was designated ICEKp1. Precise excision and extrachromosomal circularization of ICEKp1 were detected in K. pneumoniae wild-type strain NTUH-K2044. ICEKp1 could integrate into the asn tRNA loci of the chromosome of another K. pneumoniae isolate. The prevalence of ICEKp1 was higher in PLA strains (38 of 42 strains) than in non-tissue-invasive strains (5 of 32 strains). Therefore, ICEKp1 may contribute to the transmission of the HPI and result in K. pneumoniae PLA infection-associated genomic heterogeneity.

Concanavalin A protects mice from a lethal inoculation of intragastric Klebsiella pneumoniae and reduces the induced liver damage

Intragastric inoculation of Klebsiella pneumoniae can cause invasive diseases, including necrosis of liver tissues and bacteremia. The effect of concanavalin A (ConA) on K. pneumoniae was tested. Pretreatment with ConA was able to protect mice from K. pneumoniae infection in an intragastric model. K. pneumoniae-induced mouse death and liver injury such as liver necrosis, as well as blood levels of aspartate aminotransferase and alanine aminotransferase, were inhibited in a dose-dependent manner by ConA. ConA administered intravenously as late as 24 h after K. pneumoniae inoculation was still protective. In an in vitro assay, ConA was able to bind K. pneumoniae cells directly and further agglutinate them but had no effect on their in vitro growth. Surveys of bacterial counts of ConA-treated mice revealed that the bacteria were eliminated effectively in both blood and liver tissues. Furthermore, the bactericidal activity of macrophages against K. pneumoniae was also enhanced in a dose-dependent manner by ConA in an in vitro culture. These data suggest that ConA is a potentially therapeutic agent for K. pneumoniae-induced liver infection.

Klebsiella pneumoniae genotype K1: an emerging pathogen that causes septic ocular or central nervous system complications from pyogenic liver abscess

BACKGROUND

Since 1986, researchers have noted a syndrome of Klebsiella pneumoniae pyogenic liver abscess that is complicated by endophthalmitis or central nervous system infections. There are limited data regarding the role of bacterial genotype in the pathogenesis of this syndrome.

METHODS

We conducted a retrospective cohort study involving 177 cases of K. pneumoniae pyogenic liver abscess treated during 1997-2005 at a tertiary university hospital in Taiwan. We performed bacterial cps genotyping by polymerase chain reaction detection of serotype-specific alleles at wzy and wzx loci and used an in vitro serum assay to evaluate the virulence of bacterial strains.

RESULTS

Septic ocular or central nervous system complications developed in 23 patients (13%). Logistic regression analysis showed that genotype K1 was the only significant risk factor (adjusted odds ratio, 4.8; 95% confidence interval, 1.5-15.7, P=.009). The serum resistance assay indicated that, on average, K1 strains (n=100) were significantly more virulent than were strains of K2 (n=36), K20/K5/K54 (n=21), or other genotypes (n=20) (P<.001 for each comparison). In addition to the serotype-specific cps region, the genomic background of K1 strains also differed significantly from that of non-K1 strains (20-kb kfu/PTS region, 97/100 vs. 13/77; P<.001). Of the 19 cases in which genotype K1 strains caused complications, 8 patients (42%) did not have identifiable underlying medical diseases.

CONCLUSIONS

K. pneumoniae genotype K1 is an emerging pathogen capable of causing catastrophic septic ocular or central nervous system complications from pyogenic liver abscess independent of underlying diseases in the host.

Invasive Klebsiella pneumoniae syndrome in North America

Invasive liver abscess syndrome, which is caused by hypervirulent Klebsiella pneumoniae subtypes, has been emerging worldwide over the past 2 decades. The syndrome is associated with the hypermucoviscosity phenotype of K. pneumoniae strains and with the magA and rmpA genes. We provide the first laboratory evidence of the presence of rmpA-positive K. pneumoniae in North America.

A clinical survey of Klebsiella pneumoniae virulence and genotype in pyogenic liver abscess

Primary Klebsiella pneumoniae liver abscess with metastatic complications is a globally emerging infectious disease and is the leading cause of liver abscess in Taiwan. Host immunity and bacterial virulence, especially of the capsular polysaccharide type, are important in determining clinical manifestations. Investigators retrospectively studied the K pneumoniae genotype and capsular serotype from patients with 37 strains of liver abscess; no correlation was noted with genotype, and many genetically different strains caused liver abscess. Although K pneumoniae is prevalent in patients with diabetes, it can attack healthy or alcoholic people as well. Additional studies are needed to explore the mechanisms of bacterial virulence and to optimize treatment strategies. Physicians should be alert to the illness and its complications.

Control of an outbreak of pandrug-resistant Acinetobacter baumannii colonization and infection in a neonatal intensive care unit

OBJECTIVE

To investigate the potential reservoir and mode of transmission of pandrug-resistant (PDR) Acinetobacter baumannii in a 7-day-old neonate who developed PDR A. baumannii bacteremia that was presumed to be the iceberg of a potential outbreak.

DESIGN

Outbreak investigation based on a program of prospective hospital-wide surveillance for nosocomial infection.

SETTING

A 24-bed neonatal intensive care unit in a 2,200-bed major teaching hospital in Taiwan that provides care for critically ill neonates born in this hospital and those transferred from other hospitals.

INTERVENTIONS

Samples from 33 healthcare workers' hands and 40 samples from the environment were cultured. Surveillance cultures of anal swab specimens and sputum samples were performed for neonates on admission to the neonatal intensive care unit and every 2 weeks until discharge. The PDR A. baumannii isolates, defined as isolates resistant to all currently available systemic antimicrobials except polymyxin B, were analyzed by pulsed-field gel electrophoresis. Control measures consisted of implementing contact isolation, reinforcing hand hygiene adherence, cohorting of nurses, and environmental cleaning.

RESULTS

One culture of an environmental sample and no cultures of samples from healthcare workers' hands grew PDR A. baumannii. The positive culture result involved a sample obtained from a ventilation tube used by the index patient. During the following 2 months, active surveillance identified PDR A. baumannii in 8 additional neonates, and isolates from 7 had the same electrokaryotype. Of the 9 neonates colonized or infected with PDR A. baumannii, 1 died from an unrelated condition. Reinforcement of infection control measures resulted in 100% adherence to proper hand hygiene protocol. The outbreak was stopped without compromising patient care.

CONCLUSIONS

In the absence of environmental contamination, transient hand carriage by personnel who cared for neonates colonized or infected with PDR A. baumannii was suspected to be the mode of transmission. Vigilance, prompt intervention and strict adherence to hand hygiene protocol were the key factors that led to the successful control of this outbreak. Active surveillance appears to be an effective measure to identify potential transmitters and reservoirs of PDR A. baumannii.

Capsular serotype K1 or K2, rather than magA and rmpA, is a major virulence determinant for Klebsiella pneumoniae liver abscess in Singapore and Taiwan

Capsular serotypes, magA, and rmpA have been documented in high prevalence for Klebsiella pneumoniae liver abscess. To investigate the regional difference and the correlation of capsular serotype, magA, and rmpA with virulence, 73 isolates were collected in Singapore and Taiwan. Capsular serotypes were determined by countercurrent immunoelectrophoresis, the presence of magA and rmpA was determined by PCR, and virulence was determined by phagocytosis and mouse inoculation. Isolates from Singapore were similar to those from Taiwan in genomic heterogeneity, prevalence of serotype, and the presence of magA and rmpA. The most common serotype was K1 (34/73; 46.6%), followed by K2 (15/73; 20.5%). magA was restricted to serotype K1. All K1 or K2 isolates and 66.7% (16/24) of isolates that were neither serotype K1 nor serotype K2 (non-K1/K2) carried rmpA. Serotype K1 or K2 isolates demonstrated significantly more phagocytic resistance and virulence than did rmpA-positive and -negative groups of non-K1/K2 isolates. In the non-K1/K2 group, the virulence profiles of rmpA-positive strains from Taiwan and Singapore were different by phagocytosis assay and in the mouse model, indicating that factors other than rmpA contributed to virulence. The characteristics of K. pneumoniae liver abscess in Singapore and Taiwan are similar. Capsular serotype K1 or K2 plays a more important role than magA and rmpA in determining virulence in K. pneumoniae liver abscess.

Sputum bacteriology in hospitalized patients with acute exacerbation of chronic obstructive pulmonary disease in Taiwan with an emphasis on Klebsiella pneumoniae and Pseudomonas aeruginosa

BACKGROUND AND OBJECTIVE

Bacterial infection is one of the major causes of acute exacerbation of COPD (AECOPD). This study was undertaken to investigate the microbiology of AECOPD.

METHODS

Medical records from 494 episodes of AECOPD in patients admitted to the National Taiwan University Hospital from January 2000 to June 2004 were reviewed. Severity of COPD was classified according to the 2003 Global Initiative for Chronic Obstructive Lung Disease guideline.

RESULTS

Potential pathogenic microorganisms were isolated from patients in 328 (66.4%) episodes of AECOPD. The predominant bacteria were Klebsiella pneumoniae (19.6%), Pseudomonas aeruginosa (16.8%) and Haemophilus influenzae (7.5%), followed by Acinetobacter baumannii (6.9%), Enterobacter species (6.1%) and Staphylococcus aureus (6.1%). The incidence of Streptococcus pneumoniae was 2.4%. Spirometry results obtained within 1 year of the exacerbation were available in 186 cases. K. pneumoniae was more frequently isolated in stage I COPD (39.1%) than stage II (16.6%), III (13.8%) and IV (9.4%). No glucose non-fermentative Gram-negative bacilli were isolated in stage I patients. Multivariate logistic regression analysis revealed that P. aeruginosa (odds ratio (OR) 3.19; 95% confidence interval (CI): 1.21-8.38), intubation (OR 14.81; 95% CI: 5.08-43.12) and age (OR 1.1; 95% CI: 1.03-1.17) were independent risk factors for mortality.

CONCLUSIONS

Klebsiella pneumoniae and P. aeruginosa are the most common sputum pathogens in hospitalized patients with AECOPD in Taiwan, with the former being more commonly isolated from mild COPD and the latter associated with poor clinical outcome. These results should be considered when deciding which antibiotics should initially be used to treat patients with AECOPD.

Nosocomial liver abscess caused by extended-spectrum beta-lactamase-producing Klebsiella pneumoniae

A nosocomial pyogenic liver abscess caused by an extended-spectrum beta-lactamase-producing Klebsiella pneumoniae isolate presented in a man with adenocarcinoma of the stomach. The K. pneumoniae strain isolated from blood and liver aspirate cultures after antibiotic therapy for recurrent bacteremia was resistant to all extended-spectrum beta-lactams except imipenem and differed from K. pneumoniae strains causing community-acquired liver abscesses.

Comparison between pyogenic liver abscess caused by Klebsiella pneumoniae and non-Klebsiella pneumoniae

AIM: To analyze the differences between pyogenic liver abscess caused by Klebsiella pneumoniae (Kp) and non-Klebsiella pneumoniae (NKp), and provide the evidence for early diagnosis and treatment.

METHODS: The clinical data of 162 patients with pyogenic liver abscess from January 2000 to January 2005 were collected, and statistical analysis was performed to compare the differences between the Kp and NKp patients in general characteristics, underlying diseases, clinical manifestations, laboratory features, and characteristics of liver abscess, treatments and outcomes.

RESULTS: Of the 162 patients, 112 (69.1%) were classified into Kp group, and 50 (30.9%) were NKp group. There was significant difference between the two groups in ages (P < 0.05). For underlying diseases, there were significant differences in diabetes (66.1% vs 38.0%, P < 0.01), biliary diseases (14.3% vs 28.0%, P < 0.05) and abdominal injury (5.4% vs 16.0%, P < 0.05) between two groups. For clinical manifestations and laboratory features, there were also significant differences in anemia between two groups (60.7% vs 78%, P < 0.05). For characteristics of liver abscess, solitary liver abscess and monomicrobial isolates were more frequent in the Kp group than those in the NKp group (75.9% vs 58%, P < 0.05; 85.7% vs 64%, P < 0.01). For treatment and outcome, there were significant differences in metastatic infection and mortality rate between two groups (20.5%vs 6%, P < 0.05; 8.9% vs 26.0%, P < 0.01).

CONCLUSION: In comparison with those in NKp patients, the age and mortality rate of Kp patients are lower, and the rate of diabetes and metastatic infection are higher. Monomicrobial isolates are mostly found in Kp patients.

Necrotizing external otitis in a patient caused by Klebsiella pneumoniae

Necrotizing external otitis is a potentially life-threatening infection involving the temporal and adjacent bones. The most frequent pathogen is attributed to Pseudomonas aeruginosa, but is rarely caused by Klebsiella pneumoniae. Recently, we encountered a 47-year-old diabetic man with a swollen obliterated external ear canal with granulation tissue on the right ear. Image study demonstrated skull base osteomyelitis, epidural abscess and cerebral venous sinus thrombi. It was later proved to be necrotizing external otitis caused by Klebsiella pneumoniae. He then underwent craniotomy for drainage of the epidural abscess, followed by intravenous ciprofloxacin and metronidazole for 2 consecutive weeks until both pus and blood cultures depicted no growth of pathogens. Based on this case, synergistic antibiotic therapy using a third-generation cephalosporin or quinolone (ciprofloxacin), accompanied by metronidazole, and even a short-term aminoglycoside is recommended for the treatment of severe Klebsiella-induced necrotizing external otitis. Surgical intervention should be limited without shedding of the pathogens.

Pyogenic liver abscess due to Rhodococcus equi in an immunocompetent host

A case of pyogenic liver abscess (PLA) due to Rhodococcus equi in an immunocompetent individual was successfully treated by combining surgery and antibiotics. The R. equi-targeted antimicrobial agents erythromycin and rifampin were used only after surgical resection of the lesion and identification of the infective organism.

Pyogenic liver abscess: recent trends in etiology and mortality

BACKGROUND

Pyogenic liver abscess, a potentially life-threatening disease, has undergone significant changes in epidemiology, management, and mortality over the past several decades.

METHODS

We reviewed the data for patients admitted to Bellevue Hospital and New York University Downtown Hospital (New York, New York) over a 10-year period.

RESULTS

Of 79 cases reviewed, 43% occurred in patients with underlying biliary disease. The most common symptoms were fever, chills, and right upper quadrant pain or tenderness. The most common laboratory abnormalities were an elevated white blood cell count (in 68% of cases), temperature >or=38.1 degrees C (90%), a low albumin level (70.2%), and an elevated alkaline phosphatase level (67%). Seventy percent of the abscesses were in the right lobe, and 77% were solitary. Klebsiella pneumoniae was identified in 41% of cases in which a pathogen was recovered. Eighteen (50%) of 36 Asian patients had K. pneumoniae isolated, in contrast to 6 (27.3%) of 22 non-Asian patients (not statistically significant). Fifty-six percent of cases involved treatment with percutaneous drainage. Although prior reports noted mortality of 11%-31%, we observed only 2 deaths (mortality, 2.5%).

CONCLUSIONS

The data suggest that K. pneumoniae has become the predominant etiology of pyogenic liver abscess and that mortality from this disease has decreased substantially.

A novel virulence gene in Klebsiella pneumoniae strains causing primary liver abscess and septic metastatic complications

Primary Klebsiella pneumoniae liver abscess complicated with metastatic meningitis or endophthalmitis is a globally emerging infectious disease. Its pathogenic mechanism remains unclear. The bacterial virulence factors were explored by comparing clinical isolates. Differences in mucoviscosity were observed between strains that caused primary liver abscess (invasive) and those that did not (noninvasive). Hypermucoviscosity correlated with a high serum resistance and was more prevalent in invasive strains (52/53 vs. 9/52; P < 0.0001). Transposon mutagenesis identified candidate virulence genes. A novel 1.2-kb locus, magA, which encoded a 43-kD outer membrane protein, was significantly more prevalent in invasive strains (52/53 vs. 14/52; P < 0.0001). The wild-type strain produced a mucoviscous exopolysaccharide web, actively proliferated in nonimmune human serum, resisted phagocytosis, and caused liver microabscess and meningitis in mice. However, magA⁻ mutants lost the exopolysaccharide web and became extremely serum sensitive, phagocytosis susceptible, and avirulent to mice. Virulence was restored by complementation using a magA-containing plasmid. We conclude that magA fits molecular Koch's postulates as a virulence gene. Thus, this locus can be used as a marker for the rapid diagnosis and for tracing the source of this emerging infectious disease.