Chi-Tai Fang

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 Kochs 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.

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.

Decreased HIV transmission after a policy of providing free access to highly active antiretroviral therapy in Taiwan

BACKGROUND Taiwan established a nationwide surveillance system for human immunodeficiency virus (HIV) infection in 1989 and adopted a policy to provide all HIV-infected citizens with free access to highly active antiretroviral therapy (HAART) beginning in April 1997. This provided an opportunity to determine the effect of the widespread use of HAART on the evolution of the HIV epidemic. METHODS We analyzed national HIV surveillance data. The HIV transmission rate was estimated by use of an exponential model of HIV epidemic evolution, with statistical projection over the interval between infection and detection to fit the surveillance data. RESULTS By the end of 2002, the cumulative number of HIV-infected citizens in Taiwan had reached 4390 (0.019% of the total population). After free access to HAART was established, the estimated HIV transmission rate decreased by 53% (0.391 vs. 0.184 new cases/prevalent case-year [95% confidence interval, 31%-65%]). There was no statistically significant change in the incidence of syphilis, in the general population or among HIV-positive patients, during the same period. CONCLUSION Providing free HAART to all HIV-infected citizens was associated with a 53% decrease in the HIV transmission rate and contributed to the control of the HIV epidemic in Taiwan.

Genetic Determinants of Capsular Serotype K1 of Klebsiella pneumoniae Causing Primary Pyogenic Liver Abscess

BACKGROUND Primary pyogenic liver abscess (PLA) caused by Klebsiella pneumoniae is an emerging infectious disease. Capsular serotype K1 and the magA gene have been reported to be associated with this disease. METHODS The prevalence of magA was determined by polymerase chain reaction (PCR). The sequences of the magA flanking region were completed by inverse PCR and direct sequencing. Serotyping was performed by double immunodiffusion. Insertion mutations and trans-complementation were used to define the K1 genetic determination region. RESULTS Thirty-five of 42 strains from patients with PLA were magA positive, whereas only 1 of 32 non-PLA strains was magA positive. All 36 magA-positive strains were serotype K1, and the 38 magA-negative strains were not (36/36 vs. 0/38; P<.0001). Sequencing of the magA flanking region revealed a putative capsular polysaccharide synthesis (cps) region; this region was 25 kb in length and contained 20 open reading frames (ORFs); of these ORFs, 9 were cotranscribed as part of an operon and differed from both MGH78578 and the Chedid strain. Mutation of 4 genes in this region turned the mutant strains anti-K1 negative. Trans-complementation restored the K1 phenotype. CONCLUSIONS The operon containing magA is responsible for capsular serotype K1 of K. pneumoniae. Several loci in the operon are unique determinants of K1 strains.

Genomic Heterogeneity in Klebsiella pneumoniae Strains Is Associated with Primary Pyogenic Liver Abscess and Metastatic Infection

BACKGROUND Primary pyogenic liver abscess (PLA) with septic complication by Klebsiella pneumoniae is an emerging infectious disease. METHODS AND RESULTS Using DNA microarray hybridization, we identified a 20-kb chromosomal region that contained 15 open-reading frames (ORFs), including an iron-uptake system (kfu), a phosphoenolpyruvate sugar phosphotransferase system (PTS), and 6 unknown ORFs. The region was more prevalent among tissue-invasive strains (35/46) than among noninvasive strains (19/98) (P<.0001, chi2 test). To test the role played by this region in pathogenesis, 3 different deletion mutants (NTUH-K2044 [Delta kfu], K2044 [Delta ORF7-9], and K2044 [Delta PTS]) were constructed. Only the Delta kfuABC mutants showed decreased virulence in mice, compared with the wild-type strain. An in vitro assay confirmed the involvement of kfu in iron acquisition. There was a high correlation rate (85%) between the kfu/PTS region and 2 tissue invasion-associated chromosomal regions (allS and magA). Moreover, all 3 regions were present in strains that caused PLA plus endophthalmitis or meningitis. CONCLUSION Our results suggest that chromosomal heterogeneity is present in tissue-invasive K. pneumoniae strains. A genotype containing all 3 regions is strongly associated with PLA and metastatic infection. These regions may serve as convenient markers for the rapid diagnosis of emergent tissue-invasive strains.

Comparison of WHOQOL-BREF and SF-36 in patients with HIV infection

AbstractThe purpose of the study was to evaluate the reliability and validity of the two generic instruments, the WHOQOL and the SF-36, for assessing health-related quality of life in 224 patients with HIV infection. The internal consistency ranged from 0.75 to 0.86 across the WHOQOL-BREF domains and from 0.72 to 0.93 across the SF-36 scales. The scores of all WHOQOL-BREF domains and SF-36 scales correlated positively with the measure of happiness, Sat-HRQOL and self-perceived health status, and correlated negatively with the number and intensity of symptoms. Patients with higher CD4 cell counts scored significantly higher on G4 (general health), three WHOQOL-BREF domains, seven SF-36 scales, and PCS (physical component summary). Patients with fewer symptoms and with less intensity of symptoms had significantly higher scores on all four domains of WHOQOL-BREF, eight scales, PCS, and MCS (mental component summary) of the SF-36 scale. The correlations between the physical, psychological, and social domains of the WHOQOL-BREF and PF (physical functioning), MH (mental health), and SF (social functioning) of the SF-36 were 0.51, 0.75, and 0.54, respectively. There is also good correlation between PCS of the SF-36 and the physical domain of the WHOQOL-BREF (r = 0.48), and between MCS and all four domains of the WHOQOL-BREF (r range = 0.60–0.75). The WHOQOL-BREF domains showed fewer floor or ceiling effect than the SF-36 scales. We concluded that both the WHOQOL-BREF and the SF-36 are reliable and valid health related quality-of-life instruments in patients with HIV infection.

Isolation of a Chromosomal Region of Klebsiella pneumoniae Associated with Allantoin Metabolism and Liver Infection

ABSTRACT Klebsiella pneumoniae liver abscess with metastatic complications is an emerging infectious disease in Taiwan. To identify genes associated with liver infection, we used a DNA microarray to compare the transcriptional profiles of three strains causing liver abscess and three strains not associated with liver infection. There were 13 clones that showed higher RNA expression levels in the three liver infection strains, and 3 of these 13 clones contained a region that was absent in MGH 78578. Sequencing of the clones revealed the replacement of 149 bp of MGH 78578 with a 21,745-bp fragment in a liver infection strain, NTUH-K2044. This 21,745-bp fragment contained 19 open reading frames, 14 of which were proven to be associated with allantoin metabolism. The K2044 (ΔallS) mutant showed a significant decrease of virulence in intragastric inoculation of BALB/c mice, and the prevalence of this chromosomal region was significantly higher in strains associated with liver abscess than in those that were not (19 or 32 versus 2 of 94; P = 0.0001 [χ2 test]). Therefore, the 22-kb region may play a role in K. pneumoniae liver infection and serve as a marker for rapid identification.

Validation of the World Health Organization quality of life instrument in patients with HIV infection

We studied the reliability and validity of the World Health Organization quality of life (WHOQOL) assessment instrument in patients with human immunodeficiency virus (HIV) infection. WHOQOL-BREF was used to assess 136 HIV-infected outpatients. The results were analyzed and compared with data from 213 healthy persons. The Cronbachs α for internal consistency ranged from 0.74 to 0.85 across domains in HIV-infected patients. The test–retest reliability ranged from 0.64 to 0.79 across domains at average 4-week retest interval. Factor analysis identified four major factors: social, psychological, environment, and physical, consistent with the four domains of the instrument. The scores of all four domains correlated positively with self-evaluated health status and happiness (r range: 0.52–0.60 and 0.55–0.73 across domains, respectively), and correlated negatively with the number and severity of symptoms (r range: −0.40 to −0.47 and −0.41 to −0.52, respectively). The scores of physical, psychological and social domains, but not the environment domain, discriminated between healthy persons and HIV-infected patients (all p < 0.01). We conclude that the WHOQOL-BREF can be a useful quality-of-life instrument in patients with HIV infection.

Changing Bacteriology of Adult Community-Acquired Lung Abscess in Taiwan: Klebsiella pneumoniae versus Anaerobes

BACKGROUND Most literature regarding lung abscess focuses on anaerobic bacterial lung abscess, and aerobic gram-negative bacillary infection is less frequently discussed. This study was conducted to investigate the bacteriology of community-acquired lung abscess and to improve the empirical therapeutic strategy for adults with community-acquired lung abscess. METHODS We reviewed and analyzed data on 90 consecutive adult cases of bacteriologically confirmed community-acquired lung abscess treated during 1995-2003 at a tertiary university hospital in Taiwan. RESULTS We found that a high proportion (21%) of cases of lung abscess were due to Klebsiella pneumoniae infection, which differs from the findings of previous studies. Lung abscess due to K. pneumoniae was associated with underlying diabetes mellitus (odds ratio [OR], 4.3; 95% confidence interval [CI], 1.0-18.4; P = .039) and negatively correlated with a time from onset of symptoms to diagnosis of >30 days (OR, 0.2; 95% CI, 0.1-0.7; P = .008). A higher percentage of patients with K. pneumoniae lung abscess had concomitant bacteremia (OR, 9.4; 95% CI, 1.1-81.9; P = .032), delayed defervesence (OR, 9.2; 95% CI, 1.8-47.8; P = .004), and multiple cavities noted on radiographs (OR, 11.0; 95% CI, 1.3-94.9; P = .015), compared with patients with anaerobic bacterial lung abscess. The rate of nonsusceptibility to clindamycin and penicillin among anaerobes and Streptococcus milleri group isolates increased. CONCLUSION K. pneumoniae has become a more common cause of lung abscess than before, and a high proportion of anaerobes and S. milleri strains have become resistant to penicillin and clindamycin. A beta-lactam/beta-lactamase inhibitor or second- or third-generation cephalosporin with clindamycin or metronidazole is suggested as empirical antibiotic therapy for community-acquired lung abscess.

Klebsiella pneumoniae isolates causing liver abscess in Taiwan

Klebsiella pneumoniae has been the leading cause of pyogenic liver abscess in Taiwan during the period from 1985 to 1999, which is different from other countries. The present study investigated the in vitro antimicrobial susceptibilities of 51 K. pneumoniae isolates collected from blood cultures of patients with liver abscess in Taiwan during the period from 1993-1997, and typed by pulsed-field gel electrophoresis (PFGE). All 51 isolates were resistant to ampicillin, but susceptible to other antimicrobial agents. The minimum inhibitory concentrations (MICs) were less than 1 microg/ml for the third- and fourth-generation cephalosporins, monobactam, carbapenems, and ciprofloxacin. In comparison, 62 isolates of K. pneumoniae from community-acquired bacteremic patients without liver abscess had similar antimicrobial susceptibilities, while 142 isolates from patients with hospital-acquired bacteremia without liver abscess were much less susceptible to all of the tested antimicrobial agents. PFGE molecular epidemiologic analysis found 20 out of 51 isolates belonged to eight clusters of genetically related strains, with two or three isolates in each clusters. The other 31 isolates were genetically distinct strains. This study demonstrated that K. pneumoniae isolates which cause liver abscess in Taiwan remained susceptible to a wide range of antimicrobial agents and that they were not genetically related.