Genotypes and virulence in serotype K2 Klebsiella pneumoniae from liver abscess and non-infectious carriers in Hong Kong, Singapore and Taiwan

In Klebsiella pneumoniae liver abscess (KP-LA), K. pneumoniae K2 is the most frequently isolated serotype after K1, but this serotype has been much less studied. In the present study, the molecular types sequences type (MLST) of serotype K2 isolates from three different regions in Asia were identified and the virulence of these isolates was investigated. Eight different MLSTs were found among 26 isolates (ST 65, 66, 86, 373, 374, 375, 380, and 434). There were two major MLST groups, ST-65-like (42%) and ST86-like (46%). No isolates contained allS while all isolates contained rmpA. The prevalence of aerobactin gene and kfu were 25/26 (96%) and 3/26 (11.5%) respectively. Although liver abscess isolates were generally more resistant (11/15 isolates) to serum killing, there was no specific distribution of serum killing resistant or susceptible ST types between stool carriage and liver abscess isolates. Neutrophil phagocytosis showed that the liver abscess and carriage isolates varied in their susceptibility to phagocytosis. Strains with resistance to both neutrophil phagocytosis and serum killing were generally hypervirulent with lethality at LD₅₀ < 10³ colony forming units by intraperitoneal injection. In conclusion, Anti-phagocytosis and resistance to serum killing are two parameters that most predict hyperviurlence in serotype K2 isolates. Unlike serotype K1 KP-LA that mainly belong to ST-23, ST-65-like and −86-like are the two major MLST types among serotype K2 isolates from Singapore, Hong Kong and Taiwan.

Changes in HIV incidence among people who inject drugs in Taiwan following introduction of a harm reduction program: a study of two cohorts

BACKGROUND

Harm reduction strategies for combating HIV epidemics among people who inject drugs (PWID) have been implemented in several countries. However, large-scale studies using sensitive measurements of HIV incidence and intervention exposures in defined cohorts are rare. The aim of this study was to determine the association between harm reduction programs and HIV incidence among PWID.

METHODS AND FINDINGS

The study included two populations. For 3,851 PWID who entered prison between 2004 and 2010 and tested HIV positive upon incarceration, we tested their sera using a BED HIV-1 capture enzyme immunoassay to estimate HIV incidence. Also, we enrolled in a prospective study a cohort of 4,357 individuals who were released from prison via an amnesty on July 16, 2007. We followed them with interviews at intervals of 6-12 mo and by linking several databases. A total of 2,473 participants who were HIV negative in January 2006 had interviews between then and 2010 to evaluate the association between use of harm reduction programs and HIV incidence. We used survival methods with attendance at methadone clinics as a time-varying covariate to measure the association with HIV incidence. We used a Poisson regression model and calculated the HIV incidence rate to evaluate the association between needle/syringe program use and HIV incidence. Among the population of PWID who were imprisoned, the implementation of comprehensive harm reduction programs and a lower mean community HIV viral load were associated with a reduced HIV incidence among PWID. The HIV incidence in this population of PWID decreased from 18.2% in 2005 to 0.3% in 2010. In an individual-level analysis of the amnesty cohort, attendance at methadone clinics was associated with a significantly lower HIV incidence (adjusted hazard ratio: 0.20, 95% CI: 0.06-0.67), and frequent users of needle/syringe program services had lower HIV incidence (0% in high NSP users, 0.5% in non NSP users). In addition, no HIV seroconversions were detected among prison inmates.

CONCLUSIONS

Although our data are affected by participation bias, they strongly suggest that comprehensive harm- reduction services and free treatment were associated with reversal of a rapidly emerging epidemic of HIV among PWID. Please see later in the article for the Editors' Summary.

Notes from the field: wildlife rabies on an island free from canine rabies for 52 years--Taiwan, 2013

Dog-to-dog transmission of rabies in Taiwan was eliminated in 1961; the island was considered canine rabies-free for 52 years. On July 16, 2013, three ferret-badgers (Melogale moschata) tested positive for rabies by fluorescent antibody testing at the Animal Health Research Institute, Council of Agriculture of Taiwan. This was the first time wild animals other than bats were tested. During 1999-2012, a total of 6,841 clinically healthy dogs and five apparently normal cats from shelters were tested and found negative for rabies. During 2009-2012, a total of 322 bats were tested and found negative for rabies.

Differences in virulence of pneumolysin and autolysin mutants constructed by insertion duplication mutagenesis and in-frame deletion in Streptococcus pneumoniae

Background

Insertion duplication mutagenesis (IDM) and in-frame deletion (IFD) are common techniques for studying gene function, and have been applied to pneumolysin (ply), a virulence gene in Streptococcus pneumoniae (D39). Discrepancies in virulence between the two techniques were observed in both the previous and present studies. This phenomenon was also observed during mutation analysis of autolysin (lytA).

Results

Our data showed that target gene restoration (TGR) occurred in IDM mutants, even in the presence of antibiotics, while the IFD mutants were stable. In PCR result, TGR occurred later in IDM-ply and -lytA mutants cultured in non-supplemented medium (4–5 h) compared with those grown in medium supplemented with erythromycin (erm)/chloramphenicol (cat) (3–4 h), but plateaued faster. Real-time PCR for detecting TGR had been performed. When compared with 8-h culture, TGR detection increased from Day 1 and Day 2 of IDM mutant’s culture. erm-sensitive clones from IDM mutant were found. Southern blot hybridization and Western blotting also confirmed the phenomenon of TGR. The median survival of mice following intraperitoneal (IP) injection with a 3-h culture of IDM-mutants was significantly longer than that with an 8-h culture, irrespective of antibiotic usage. The median survival time of mice following IP injection of a 3-h culture versus an 8-h culture of IDM-ply in the absence of antibiotics was 10 days versus 2 days (p = 0.031), respectively, while in the presence of erm, the median survival was 5 days versus 2.5 days (p = 0.037), respectively. For an IDM-lytA mutant, the corresponding values were 8.5 days versus 2 days (p = 0.019), respectively, for non-supplemented medium, and 2.5 versus 2 days (p = 0.021), respectively, in the presence of cat. A comparable survival rate was observed between WT D39 and an 8-h IDM culture.

Conclusion

TGR in IDM mutants should be monitored to avoid inconsistent results, and misinterpretation of data due to TGR could lead to important biological meaning being overlooked. Therefore, based on these results, IFD is preferable to IDM for disruption of target genes.

Pyrosequencing reveals an oseltamivir-resistant marker in the quasispecies of avian influenza A (H7N9) virus

Prompt diagnosis of an oseltamivir-resistant marker is important for patient management, in particular to prevent the spread of resistant strains in the recent human H7N9 outbreak. We tailored a pyrosequencing assay to reveal neuraminidase R292K, a resistant marker found in one isolate from China, and demonstrated its performance in both sensitivity and specificity. In addition, a semi-nested polymerase chain reaction was applied, which enhanced the detection rate by at least 10-fold. We validated this assay by examining the marker in Taiwan's first imported human case and found R and K in quasispecies.

Role of QuantiFERON-TB-Gold In Tube assay for active and latent tuberculosis infection in investigation of tuberculosis outbreak in a university

BACKGROUND

Identification and monitoring of active tuberculosis (TB) and latent tuberculosis infection (LTBI) are the key steps to prevent transmission during a TB outbreak. The aim of this study was to evaluate the role of QuantiFERON-TB-Gold In Tube assay (QFT-GIT) in the investigation of active TB and LTBI cases during a TB outbreak in a university.

METHODS

In this study, enrolled students and teachers were evaluated with chest radiograph, questionnaire, and QFT-GIT test. The diagnosis of active pulmonary TB was based on sputum studies and chest radiographs. The questionnaire, which covered demographic information, underlying diseases, and environmental exposures, was applied to assess the association of risk factors by multiple logistic regressions.

RESULTS

A total of 159 participants completed the study protocol. Positive QFT-GIT results were demonstrated in class A (75.7%; 25/33), class B (57.1%; 20/35), and class C (37.5%; 3/8) in institute 1; class D (17.3%; 8/46) in institute 2; and class E (3.1%; 1/32) in institute 3; but none among the (0/5) administrative officers, who comprised the control group. "Number of contact with active TB cases" was strongly associated and correlated with the prediction of a positive QFT-GIT result in multivariate analysis (odds ratio = 1.99; 95% confidence interval, 1.52-2.61; p < 0.0001). Seven cases progressed to active TB infection, all showing positive QFT-GIT results (100%; 7/7).

CONCLUSION

Inclusion of QFT-GIT may be helpful in controlling and monitoring of active TB and LTBI cases during an investigation of a TB outbreak. The finding demonstrated that the QFT-GIT test was useful in accurately identifying infected and uninfected students, permitting rapid intervention.

Surveillance of avian influenza A(H7N9) virus infection in humans and detection of the first imported human case in Taiwan, 3 April to 10 May 2013

On 3 April 2013, suspected and confirmed cases of influenza A(H7N9) virus infection became notifiable in the primary care sector in Taiwan, and detection of the virus became part of the surveillance of severe community-acquired pneumonia. On 24 April, the first imported case, reported through both surveillance systems, was confirmed in a man returning from China by sequencing from endotracheal aspirates after two negative throat swabs. Three of 139 contacts were ill and tested influenza A(H7N9)-negative.

Surveillance of avian influenza A(H7N9) virus infection in humans and detection of the first imported human case in Taiwan, 3 April to 10 May 2013

On 3 April 2013, suspected and confirmed cases of influenza A(H7N9) virus infection became notifiable in the primary care sector in Taiwan, and detection of the virus became part of the surveillance of severe community-acquired pneumonia. On 24 April, the first imported case, reported through both surveillance systems, was confirmed in a man returning from China by sequencing from endotracheal aspirates after two negative throat swabs. Three of 139 contacts were ill and tested influenza A(H7N9)-negative.

Syphilis among men who have sex with men (MSM) in Taiwan: its association with HIV prevalence, awareness of HIV status, and use of antiretroviral therapy

To understand how awareness of HIV-positivity and the use of antiretroviral therapy associated with syphilis infection, 361 MSM attending 16 Hong-Pa (drug-and-sex parties) in Taiwan were studied. The syphilis rate of individuals within their first 2 years after HIV diagnosis (awareness) was lower than that in individuals who had not been diagnosed HIV infection prior to Hong-Pa (unawareness) (Adj OR = 0.24, P < 0.05). Notably, there was a decrease in the beneficial effect of HIV-positive status awareness on syphilis prevention with an increase in time since notification. Moreover, antiretroviral therapy was not associated with a lower incidence of syphilis, and syphilis infection peaked during the treatment dropout period. In conclusion, the duration of a protective effect of knowing one's HIV-positivity against syphilis infection was short, and the highest risk of syphilis infection was observed when patients discontinued antiretroviral therapy. Future research should examine the behavioral mechanisms involved in this prevention failure.

Estimating the burden of pneumococcal pneumonia among adults: a systematic review and meta-analysis of diagnostic techniques

Background

Pneumococcal pneumonia causes significant morbidity and mortality among adults. Given limitations of diagnostic tests for non-bacteremic pneumococcal pneumonia, most studies report the incidence of bacteremic or invasive pneumococcal disease (IPD), and thus, grossly underestimate the pneumococcal pneumonia burden. We aimed to develop a conceptual and quantitative strategy to estimate the non-bacteremic disease burden among adults with community-acquired pneumonia (CAP) using systematic study methods and the availability of a urine antigen assay.

Methods and Findings

We performed a systematic literature review of studies providing information on the relative yield of various diagnostic assays (BinaxNOW® S. pneumoniae urine antigen test (UAT) with blood and/or sputum culture) in diagnosing pneumococcal pneumonia. We estimated the proportion of pneumococcal pneumonia that is bacteremic, the proportion of CAP attributable to pneumococcus, and the additional contribution of the Binax UAT beyond conventional diagnostic techniques, using random effects meta-analytic methods and bootstrapping. We included 35 studies in the analysis, predominantly from developed countries. The estimated proportion of pneumococcal pneumonia that is bacteremic was 24.8% (95% CI: 21.3%, 28.9%). The estimated proportion of CAP attributable to pneumococcus was 27.3% (95% CI: 23.9%, 31.1%). The Binax UAT diagnosed an additional 11.4% (95% CI: 9.6, 13.6%) of CAP beyond conventional techniques. We were limited by the fact that not all patients underwent all diagnostic tests and by the sensitivity and specificity of the diagnostic tests themselves. We address these resulting biases and provide a range of plausible values in order to estimate the burden of pneumococcal pneumonia among adults.

Conclusions

Estimating the adult burden of pneumococcal disease from bacteremic pneumococcal pneumonia data alone significantly underestimates the true burden of disease in adults. For every case of bacteremic pneumococcal pneumonia, we estimate that there are at least 3 additional cases of non-bacteremic pneumococcal pneumonia.

Acinetobacter baumannii nosocomial pneumonia: is the outcome more favorable in non-ventilated than ventilated patients?

Background

Acinetobacter baumannii hospital-acquired pneumonia (HAP) is associated with a high mortality worldwide. Non-ventilated patients with HAP (NVHAP) caused by nosocomial pathogens are reported to have a more favorable outcome than those with ventilator-associated pneumonia (VAP). The current study was designed to determine whether bacteremic patients with A. baumannii NVHAP also have a lower mortality than those receiving assisted ventilation.

Methods

This retrospective 10-year study was conducted at a 2900-bed teaching hospital located in Northern Taiwan. The population consisted of 144 patients with A. baumannii bacteremia and HAP. Of these 96 had VAP and 48 had NVHAP. Charts were reviewed for demographic characteristics, comorbidities, clinical manifestations, antimicrobial susceptibility, and 14-day mortality. Clonal relationships were determined by molecular typing.

Results

There were no significant differences between the two groups in comorbidities (Charlson scores). Patients with NVHAP were more likely to have developed bacteremia earlier, outside the ICU and undergone fewer invasive procedures. They had significantly lower APACHE II scores, fewer bilateral pneumonias and lower rates of antimicrobial resistance. No specific clones were identified in either group. The unadjusted (crude) 14-day mortality rates were not significantly different between the groups (NVHAP 43.8% vs. VAP 31.3%, p = 0.196). The adjusted 14-day mortality risk was significantly lower in ventilator-assisted patients (odds ratio = 0.201; 95% confidence interval = 0.075-0.538; p = 0.001).

Conclusions

Patients with bacteremic NVHAP and VAP caused by A. baumannii had similar crude mortality rates, but on logistic regression analysis those receiving ventilator assistance had a significantly lower mortality. This may have been due to better airway protection, more intensive monitoring with earlier diagnosis and treatment in patients with VAP, greater innate susceptibility to infection in those with NVHAP and differences in the virulence of A. baumannii.

Surveillance and vaccine effectiveness of an influenza epidemic predominated by vaccine-mismatched influenza B/Yamagata-lineage viruses in Taiwan, 2011-12 season

Introduction

The 2011−12 trivalent influenza vaccine contains a strain of influenza B/Victoria-lineage viruses. Despite free provision of influenza vaccine among target populations, an epidemic predominated by influenza B/Yamagata-lineage viruses occurred during the 2011−12 season in Taiwan. We characterized this vaccine-mismatched epidemic and estimated influenza vaccine effectiveness (VE).

Methods

Influenza activity was monitored through sentinel viral surveillance, emergency department (ED) and outpatient influenza-like illness (ILI) syndromic surveillance, and case-based surveillance of influenza with complications and deaths. VE against laboratory-confirmed influenza was evaluated through a case-control study on ILI patients enrolled into sentinel viral surveillance. Logistic regression was used to estimate VE adjusted for confounding factors.

Results

During July 2011−June 2012, influenza B accounted for 2,382 (72.5%) of 3,285 influenza-positive respiratory specimens. Of 329 influenza B viral isolates with antigen characterization, 287 (87.2%) were B/Yamagata-lineage viruses. Proportions of ED and outpatient visits being ILI-related increased from November 2011 to January 2012. Of 1,704 confirmed cases of influenza with complications, including 154 (9.0%) deaths, influenza B accounted for 1,034 (60.7%) of the confirmed cases and 103 (66.9%) of the deaths. Reporting rates of confirmed influenza with complications and deaths were 73.5 and 6.6 per 1,000,000, respectively, highest among those aged ≥65 years, 50−64 years, 3−6 years, and 0−2 years. Adjusted VE was −31% (95% CI: −80, 4) against all influenza, 54% (95% CI: 3, 78) against influenza A, and −66% (95% CI: −132, −18) against influenza B.

Conclusions

This influenza epidemic in Taiwan was predominated by B/Yamagata-lineage viruses unprotected by the 2011−12 trivalent vaccine. The morbidity and mortality of this vaccine-mismatched epidemic warrants careful consideration of introducing a quadrivalent influenza vaccine that includes strains of both B lineages.

Klebsiella pneumoniae liver abscess: a new invasive syndrome

Klebsiella pneumoniae is a well known human nosocomial pathogen. Most community-acquired K pneumoniae infections cause pneumonia or urinary tract infections. During the past two decades, however, a distinct invasive syndrome that causes liver abscesses has been increasingly reported in Asia, and this syndrome is emerging as a global disease. In this Review, we summarise the clinical presentation and management as well the microbiological aspects of this invasive disease. Diabetes mellitus and two specific capsular types in the bacterium predispose a patient to the development of liver abscesses and the following metastatic complications: bacteraemia, meningitis, endophthalmitis, and necrotising fasciitis. For patients with this invasive syndrome, appropriate antimicrobial treatment combined with percutaneous drainage of liver abscesses increases their chances of survival. Rapid detection of the hypervirulent strain that causes this syndrome allows earlier diagnosis and treatment, thus minimising the occurrence of sequelae and improving clinical outcomes.

Klebsiella pneumoniae in gastrointestinal tract and pyogenic liver abscess

To determine the role of gastrointestinal carriage in Klebsiella pneumoniae liver abscess, we studied 43 patients. Bacterial isolates from liver and fecal samples from 10 patients with this condition and 7 healthy carriers showed identical serotypes and genotypes with the same virulence. This finding indicated that gastrointestinal carriage is a predisposing factor for liver abscess.

Characterization of oseltamivir-resistant influenza A(H1N1)pdm09 viruses in Taiwan in 2009-2011

The early isolated swine-origin influenza A(H1N1)pdm09 viruses were susceptible to oseltamivir; however, there is a concern about whether oseltamivir-resistant influenza A(H1N1)pdm09 viruses will spread worldwide as did the oseltamivir-resistant seasonal influenza A(H1N1) viruses in 2007-2008. In this study, the frequency of oseltamivir resistance in influenza A(H1N1)pdm09 viruses was determined in Taiwan. From May 2009 to April 2011, 1,335 A(H1N1)pdm09-positive cases in Taiwan were tested for the H275Y mutation in the neuraminidase (NA) gene that confers resistance to oseltamivir. Among these, 15 patients (1.1%) were found to be infected with H275Y virus. All the resistant viruses were detected after the patients have received the oseltamivir. The overall monthly ratio of H275Y-harboring viruses ranged between 0% and 2.88%, and the peak was correlated with influenza epidemics. The genetic analysis revealed that the oseltamivir-resistant A(H1N1)pdm09 viruses can emerged from different variants with a great diversity under drug pressure. The ratio of NA/HA activities in different clades of oseltamivir-resistant viruses was reduced compared to those in the wild-type viruses, indicating that the balance of NA/HA in the current oseltamivir-resistant influenza A(H1N1)pdm09 viruses was interfered. It is possible that H275Y-bearing A(H1N1)pdm09 virus has not yet spread globally because it lacks the essential permissive mutations that can compensate for the negative impact on fitness by the H275Y amino acid substitution in NA. Continuous monitoring the evolution patterns of sensitive and resistant viruses is required to respond to possible emergence of resistant viruses with permissive genetic background which enable the wide spread of resistance.

Methicillin-resistant Staphylococcus aureus bacteremia in hemodialysis and nondialysis patients

BACKGROUND/PURPOSE

Increased mortality has been reported in patients treated with vancomycin for methicillin-resistant Staphylococcus aureus (MRSA) bacteremia with high minimum inhibitory concentration (MIC) values within the susceptibility range. However, this finding has not been verified in hemodialysis patients, who have much higher invasive MRSA infection rates than nondialysis patients. We aimed at comparing vancomycin MICs between hemodialysis and nondialysis patients, and identifying predictors of high vancomycin MICs and infection-related mortality in hemodialysis patients with MRSA bacteremia.

METHODS

Patients with MRSA bacteremia from January 2008 through December 2009 were enrolled. Vancomycin MIC was determined for each first isolate using the Etest method. Clinical characteristics and vancomycin MICs were compared between hemodialysis and nondialysis patients. Factors associated with high vancomycin MIC (2 μg/mL) and infection-related mortality in hemodialysis patients were analyzed.

RESULTS

A total of 162 MRSA bacteremia episodes were identified. Forty-four (27.0%) isolates were obtained from hemodialysis patients and 118 (73.0%) from nondialysis patients. Diabetes (63.3% vs. 39.8%, p = 0.007) and prior vancomycin exposure in 30 days (31.8% vs. 12.7%, p = 0.005) were more prevalent in hemodialysis group than in nondialysis group. A higher prevalence of vancomycin MIC of 2 μg/mL was observed in hemodialysis group in comparison with nondialysis group (11.4% vs. 1.7%, p = 0.016). In following analyses of hemodialysis group, patients with initial presentation of septic shock had a higher risk of vancomycin MIC of 2 μg/mL than nonseptic shock patients (100.0% vs. 38.5% p = 0.014). Infection-related mortality was associated with age, Acute Physiology and Chronic Health Evaluation II (APACHE-II) score >15, presence of septic shock, receipt of mechanical ventilation, and failure to remove source of bacteremia in univariate analysis.

CONCLUSION

Hemodialysis patients with MRSA bacteremia are more likely to have a high vancomycin MIC (2 μg/mL) compared with nondialysis patients. Infection-related mortality is associated with the patient's clinical manifestations, including age, APACHE-II score >15, presence of septic shock, receipt of mechanical ventilation, and failure to remove source of bacteremia. Treatment selection should be tailored according to the patient's clinical condition.