Epidemiology of community-acquired and nosocomial bloodstream infections in tropical Australia: a 12-month prospective study

Multiple phylogenetically-diverse, differentially-virulent Burkholderia pseudomallei isolated from a single soil sample collected in Thailand

Burkholderia pseudomallei is a soil-dwelling bacterium endemic to Southeast Asia and northern Australia that causes the disease, melioidosis. Although the global genomic diversity of clinical B. pseudomallei isolates has been investigated, there is limited understanding of its genomic diversity across small geographic scales, especially in soil. In this study, we obtained 288 B. pseudomallei isolates from a single soil sample (~100g; intensive site 2, INT2) collected at a depth of 30cm from a site in Ubon Ratchathani Province, Thailand. We sequenced the genomes of 169 of these isolates that represent 7 distinct sequence types (STs), including a new ST (ST1820), based on multi-locus sequence typing (MLST) analysis. A core genome SNP phylogeny demonstrated that all identified STs share a recent common ancestor that diverged an estimated 796-1260 years ago. A pan-genomics analysis demonstrated recombination between clades and intra-MLST phylogenetic and gene differences. To identify potential differential virulence between STs, groups of BALB/c mice (5 mice/isolate) were challenged via subcutaneous injection (500 CFUs) with 30 INT2 isolates representing 5 different STs; over the 21-day experiment, eight isolates killed all mice, 2 isolates killed an intermediate number of mice (1-2), and 20 isolates killed no mice. Although the virulence results were largely stratified by ST, one virulent isolate and six attenuated isolates were from the same ST (ST1005), suggesting that variably conserved genomic regions may contribute to virulence. Genomes from the animal-challenged isolates were subjected to a bacterial genome-wide association study to identify genomic regions associated with differential virulence. One associated region is a unique variant of Hcp1, a component of the type VI secretion system, which may result in attenuation. The results of this study have implications for comprehensive sampling strategies, environmental exposure risk assessment, and understanding recombination and differential virulence in B. pseudomallei.

Comparative clinical characteristics and outcomes of patients with community acquired bacteremia caused by Escherichia coli, Burkholderia pseudomallei and Staphylococcus aureus: A prospective observational study (Ubon-sepsis)

BACKGROUND

Community acquired bacteremia (CAB) is a common cause of sepsis in low and middle-income countries (LMICs). However, knowledge about factors associated with outcomes of CAB in LMICs is limited.

METHODOLOGY/PRINCIPAL FINDINGS

A prospective observational study (Ubon-sepsis) of adults admitted to a referral hospital with community-acquired infection in Northeastern Thailand was conducted between March 1, 2013 and February 1, 2017. In the present analysis, patients with a blood culture collected within 24 hours of admission that was positive for one of the three most common pathogens were studied. Clinical features, management, and outcomes of patients with each cause of CAB were compared. Of 3,806 patients presenting with community-acquired sepsis, 155, 131 and 37 patients had a blood culture positive for Escherichia coli, Burkholderia pseudomallei and Staphylococcus aureus, respectively. Of these 323 CAB patients, 284 (89%) were transferred from other hospitals. 28-day mortality was highest in patients with B. pseudomallei bactaeremia (66%), followed by those with S. aureus bacteraemia (43%) and E. coli (19%) bacteraemia. In the multivariable Cox proportional hazards model adjusted for age, sex, transfer from another hospital, empirical antibiotics prior to or during the transfer, and presence of organ dysfunction on admission, B. pseudomallei (aHR 3.78; 95%CI 2.31-6.21) and S. aureus (aHR 2.72; 95%CI 1.40-5.28) bacteraemias were associated with higher mortality compared to E. coli bacteraemia. Receiving empirical antibiotics recommended for CAB caused by the etiologic organism prior to or during transfer was associated with survival (aHR 0.58; 95%CI 0.38-0.88).

CONCLUSIONS/SIGNIFICANCE

Mortality of patients with CAB caused by B. pseudomallei was higher than those caused by S. aureus and E. coli, even after adjusting for presence of organ dysfunction on admission and effectiveness of empirical antibiotics received. Improving algorithms or rapid diagnostic tests to guide early empirical antibiotic may be key to improving CAB outcomes in LMICs.

Clinico-microbiological description and evaluation of rapid lateral flow immunoassay and PCR for detection of Burkholderia pseudomallei from patients hospitalized with sepsis and pneumonia: A twenty-one months study from Odisha, India

Establishing a diagnosis of melioidosis based on clinical grounds is difficult in hospitalized patients with sepsis or community acquired pneumonia (CAP). We aimed to ascertain the prevalence, clinico-epidemiological and laboratory profile of melioidosis in hospitalized patients with sepsis or CAP, and to evaluate the diagnostic utility of rapid lateral flow immunoassay (LFI) and PCR in comparison with culture. In all patients with sepsis or CAP, blood, sputum/throat swab, and urine sample were subjected to culture along with other samples based on clinical presentation. In addition, PCR assay targeting the type III secretion system 1 (TTS1) and LFI was performed. Thirty-three (33/196, 17%) out of the total 196 cases were diagnosed as melioidosis by culture. The prevalence of melioidosis in patients who had only sepsis without CAP, had both sepsis and CAP, had CAP without sepsis was 31% (26/84), 22 % (4/18) and 3%(3/94) respectively. All the LFI or PCR positive cases were culture positive from at least one or more samples (blood/sputum/urine/pus). The sensitivity, specificity, positive predictive value and negative predictive value of TTS1 PCR was 78% (18/23 melioidosis patients), 100% (34/34 non-melioidosis patients), 100% (18/18 melioidosis patients) and 87% (34/39 non-melioidosis patients). The sensitivity, specificity, positive predictive value and negative predictive value of Rapid LFI was 91% (21/23 melioidosis patients), 100% (22/22 non-melioidosis patients), 100% (21/21 melioidosis patients) and 91% (22/24 non-melioidosis patients). On sample wise stratification of LFI and TTS1 with respect to culture, plasma/serum samples showed the highest discordance by PCR (9/55, 16.3%) and LFI (11/35, 31.4%). The lowest discordance was noted in respiratory tract samples (2/32, 6.2%) by PCR and pus/body fluids samples (2/14, 14.2%) by LFI and these findings are in line with previous published literature. The clinical utility of PCR and LFI needs to be further validated in a large scale study for early diagnosis of septicaemic melioidosis.

Revisiting the epidemiology of bloodstream infections and healthcare-associated episodes: results from a multicentre prospective cohort in Spain (PRO-BAC Study)

The epidemiology of bloodstream infections (BSIs) is dynamic as it depends on microbiological, host and healthcare system factors. The aim of this study was to update the information regarding the epidemiology of BSIs in Spain considering the type of acquisition. An observational, prospective cohort study in 26 Spanish hospitals from October 2016 through March 2017 including all episodes of BSI in adults was performed. Bivariate analyses stratified by type of acquisition were performed. Multivariate analyses were performed by logistic regression. Overall, 6345 BSI episodes were included; 2510 (39.8%) were community-acquired (CA), 1661 (26.3%) were healthcare-associated (HCA) and 2056 (32.6%) hospital-acquired (HA). The 30-day mortality rates were 11.6%, 19.5% and 22.0%, respectively. The median age of patients was 71 years (interquartile range 60-81 years) and 3656 (58.3%; 95% confidence interval 57.1-59.6%) occurred in males. The proportions according to patient sex varied according to age strata. Escherichia coli (43.8%), Klebsiella spp. (8.9%), Staphylococcus aureus (8.9%) and coagulase-negative staphylococci (7.4%) were the most frequent pathogens. Multivariate analyses confirmed important differences between CA and HCA episodes, but also between HCA and HA episodes, in demographics, underlying conditions and aetiology. In conclusion, we have updated the epidemiological information regarding patients' profiles, underlying conditions, frequency of acquisition types and aetiological agents of BSI in Spain. HCA is confirmed as a distinct type of acquisition.

Epidemiology and microbiology of Gram-negative bloodstream infections in a tertiary-care hospital in Beijing, China: a 9-year retrospective study

Background: Gram-negative bacterial bloodstream infections (BSIs) are associated with high morbidity and mortality. The present study examines the incidence, clinical characteristics, microbiological features, drug resistance and mortality associated with Gram-negative bacterial BSIs at a tertiary-care hospital in Beijing, China.Methods: This retrospective cohort study of patients with Gram-negative bacterial BSIs was performed between 1 January 2010 and 31 December 2018 at the Chinese People^,s Liberation Army General Hospital.Results: A total of 6867 episodes of Gram-negative bacterial BSIs occurred among 3199 patients over 9 years. The overall incidence of Gram-negative bacterial BSIs fluctuated from 2.30 to 2.55 episodes per 1000 admissions over 9 years. Escherichia coli was the major pathogen (34.3%). The antibiotic resistance of ESBLs-producing E. coli was higher than non-ESBLs producing E. coli including the majority of antibiotics, but to carbapenems (0.7% VS 5.1%). Between 2010 and 2018, the overall mortality of Gram-negative bacterial BSIs decreased from 11.41% to 9.05% (X² = 6.95, P = 0.434).Conclusions: Cephalosporins and carbapenem antibiotics were considered as the optimal treatment for patients with Gram-negative bacterial BSIs except for A. baumannii, which was treated according to the drug sensitivity or multidrug combination.

Trends in Bacteremia Over 2 Decades in the Top End of the Northern Territory of Australia

Background

Information on the local distribution of bloodstream pathogens helps to guide empiric antibiotic selection and can generate hypotheses regarding the effectiveness of infection prevention practices. We assessed trends in bacterial blood culture isolates at Royal Darwin Hospital (RDH) in the Northern Territory of Australia between 1999 and 2019.

Methods

 Species identification was extracted for all blood cultures first registered at RDH. Thirteen organisms were selected for focused analysis. Trends were examined graphically and using univariable linear regression.

Results

 Between 1999 and 2019, 189 577 blood cultures from 65 276 patients were processed at RDH. Overall, 6.72% (12 747/189 577) of blood cultures contained a bacterial pathogen. Staphylococcus aureus was the most common cause of bacteremia during the first decade, with an estimated incidence of 96.6 episodes per 100 000 person-years (py; 95% CI, 72.2-121/100 000 py) in 1999. Since 2009, S. aureus bacteremia has declined markedly, whereas there has been an inexorable rise in Escherichia coli bacteremia (30.1 to 74.7/100 000 py between 1999 and 2019; P < .001), particularly in older adults. Since 2017, E. coli has been more common than S. aureus. Rates of Streptococcus pneumoniae bacteremia have reduced dramatically in children, while Burkholderia pseudomallei remained the fourth most common bloodstream isolate overall.

Conclusions

 The incidence of S. aureus bacteremia, though high by international standards, is declining at RDH, possibly in part due to a sustained focus on both community and hospital infection prevention practices. Gram-negative bacteremia, particularly due to E. coli, is becoming more common, and the trend will likely continue given our aging population.

Estimation of Incidence of Typhoid and Paratyphoid Fever in Vientiane, Lao People's Democratic Republic

Typhoid conjugate vaccines represent a new tool for typhoid control. However, incidence data are needed to inform decisions about introduction. We sought to estimate typhoid and paratyphoid fever incidence in Vientiane, the capital and largest city of the Lao People's Democratic Republic (Lao PDR). We did a representative cluster survey of health-seeking behavior for fever in Vientiane from January 15, 2019 through January 26, 2019. Multipliers derived from the survey were applied to data from Salmonella Typhi and Salmonella Paratyphi A bloodstream infection surveillance from Mahosot Hospital, Vientiane, for the period of January 1, 2015 through December 31, 2017, to estimate enteric fever incidence. A total of 336 households representing 1,740 persons were enrolled in the healthcare utilization survey, and multipliers were derived based on responses to questions about healthcare seeking in the event of febrile illness. Of 7,997 Vientiane residents receiving blood cultures over the 2-year surveillance period at Mahosot Hospital, we identified 16 (0.2%) with Salmonella Typhi and six (< 0.1%) with Salmonella Paratyphi A bloodstream infection. After applying multipliers, we estimated that the annual incidence of typhoid was 4.7 per 100,000 persons and paratyphoid was 0.5 per 100,000 persons. During the study period, the incidence of typhoid and paratyphoid fever was low in Vientiane. Ongoing surveillance is warranted to identify increases in future years. Similar studies elsewhere in the Lao PDR would be useful to understand the wider enteric fever situation in the country.

Integrating Bacterial Identification and Susceptibility Testing: A Simple and Rapid Approach to Reduce the Turnaround Time in the Management of Blood Cultures

We evaluated a rapid bacterial identification (rID) and a rapid antimicrobial susceptibility testing by disk diffusion (rAST) from positive blood culture to overcome the limitations of the conventional methods and reduce the turnaround time in bloodstream infection diagnostics. The study included hemocultures flagged as positive by bacT/ALERT®, identification by MALDI-TOF MS, and rAST. The results were compared to identification and antimicrobial susceptibility testing (AST) results by current standard methods, after 24 h incubation. For rAST categorical agreement (CA), very major errors (VME), major errors (ME), and minor errors (mE) were calculated. A total of 524 bacterial samples isolated from blood cultures were obtained, including 246 Gram-negative (GN) and 278 Gram-positive (GP) aerobes. The overall concordance of rID was 88.6%, and it was highest among GN (96%). A total of 2196 and 1476 antimicrobial agent comparisons were obtained for GN and GP, respectively. Evaluation of rAST, CA, VME, ME, and mE disclosed 97.7, 0.7, 0.5, and 1.1% for GN and 98.0, 0.5, 0.7, and 0.8% for GP, respectively. Meropenem CA, VME, and ME were 98.3, 0.5, and 0.5%, respectively; mE was not observed. Oxacillin CA, ME, and mE were 97.4, 1.6, and 0.6%, respectively; VME was not observed. Overall, kappa scores of the results of the comparisons demonstrated the high agreement between rAST and the standard method. Identification and AST of aerobic bacteria from positive blood cultures after a short period of incubation on solid blood agar is a fast and reliable method that may improve the management of bloodstream infections.

Incidence of community onset MRSA in Australia: least reported where it is Most prevalent

Background

This is the first review of literature and synthesis of data on community onset methicillin resistant Staphylococcus aureus (CO-MRSA) infections in Australia. Incidence of CO-MRSA varies considerably in Australia, depending on geographic and demographic factors.

Methods

Data for the rates of MRSA infections were collected from articles identified using PubMed, Scopus, the grey literature and data from State and Federal Government Surveillance Systems. We synthesized data and developed a framework for how data was selected, collated, linked, organized and interpreted.

Results

The results of our literature search demonstrates considerable gaps in the reporting of CO-MRSA in Australia. Consequently, total incidences were under reported; however the available data suggests the incidence varied between 44 (Tasmania) and 388 (southern Northern Territory) cases per 100,000 person years. Hospitalised cases of CO-MRSA varied between 3.8 (regional Victoria) and 329 (southern Northern Territory). Taking the median percentage of infections by site for all regions available, skin and soft tissue infections (SSTIs) consisted of 56% of hospitalized CO-MRSA, compared with bacteremias, which represented 14%. No region had a complete data set of CO-MRSA infections treated in out-patient settings and so incidences were underestimates. Nevertheless, estimates of the incidence of CO-MRSA treated outside hospitals varied between 11.3 (Melbourne) and 285 (Northern Territory) per 100,000 person-years. These infections were chiefly SSTIs, although urinary tract infections were also noted.Incidences of CO-MRSA blood-stream infections and outpatient skin and soft tissue infections have been increasing with time, except in Tasmania. CO-MRSA is observed to affect people living in remote areas and areas of socioeconomic disadvantage disproportionately.

Conclusions

We generated the first estimates of the incidence of CO-MRSA infections in Australia and identified stark regional differences in the nature and frequency of infections. Critically, we demonstrate that there has been a lack of consistency in reporting CO-MRSA and a general dearth of data. The only government in Australia that requires reporting of CO-MRSA is the Tasmanian, where the infection was least prevalent. Some regions of Australia have very high incidences of CO-MRSA. To improve surveillance and inform effective interventions, we recommend a standardized national reporting system in Australia that reports infections at a range of infection sites, has broad geographic coverage and consistent use of terminology. We have identified limitations in the available data that hinder understanding the prevalence of CO-MRSA.

MELIOIDOSIS AND GLANDERS: CURRENT STATE AND ACTUAL ISSUES OF EPIDEMIOLOGICAL SURVEILLANCE

Burkholderia pseudomallei and Burkholderia mallei are etiologic agents of glanders and melioidosis, the particularly dangerous infections of animals and humans, and are attributed to potential agents of bioterrorism. The manifestation of diseases ranges from acute septicemia to chronic infection, any organs and tissues are affected, andtreatment requires long intravenous and oral antibiotic courses. The endemic zone of glanders and melioidosis covers spacious regions in the world, and the number of imported cases to temperate regions is constantly increasing. For the Russian Federation, glanders and melioidosis are «forgotten» and «unknown» infections, and this review presents current data on their distribution in the world, epidemiological aspects, and laboratory diagnosis features.

Association of high mortality with extended-spectrum β-lactamase (ESBL) positive cultures in community acquired infections

PURPOSE

Infections due to multidrug resistant organisms have become a serious health concern worldwide. The present study was conducted to investigate the spectrum of microbial resistance pattern in the community and their effects on mortality.

METHODS

A retrospective review and analysis of prospectively collected data was done of all patients admitted with diagnosis of sepsis in two tertiary care ICU's for a period of two years. Demographics, culture positivity, microbial spectrum, resistance pattern and outcome data were collected.

RESULTS

Out of 5309 patients enrolled; 3822 had suspected clinical infection on admission with 1452 patients growing positive microbial cultures. Among these, 201 bacterial strains were isolated from patients who had community acquired infections. 73% were Gram negative bacilli, commonest being E. coli (63%). 63.4% E. coli and 60.7% Klebsiella isolates were ESBL producers. The mortality in ESBL positive infections was significantly higher as compared to ESBL negative infections (Odds ratio 2.756). Moreover, ESBL positive patients empirically treated with Beta Lactams+Beta Lactamase inhibitors (BL+BLI) had significantly higher mortality as compared to patients treated with carbapenems. More data from multiple centres need to be gathered to formulate appropriate antibiotic policy for critically ill patients admitted from the community.

Cavitary lung lesions: Melioidosis and pulmonary embolism causing necrotizing pneumonia

Cavitary lung lesions of various etiologies may be encountered in patients with respiratory symptoms associated with fever. Non-malignant cavitary lesions may mimic malignant lung lesions on most of radiographic modalities including chest radiographs or thoracic computed tomography (CT). Primary lung malignancy can be detected in as high as one-fifths of CT thorax as cavitary lesions and the remaining aetiologies may be due to bacterial, parasitic, and invasive fungal infections, as well as Granulomatosis with polyangiitis (GPA), sarcoidosis, septic thrombo-embolism, and lung metastasis from extra-pulmonary primaries. We report an interesting case of melioidosis infection complicated with pulmonary embolism, both of which can lead to cavitary lung lesions and subsequently cause a clinical conundrum.

Multitarget Quantitative PCR Improves Detection and Predicts Cultivability of the Pathogen Burkholderia pseudomallei

Burkholderia pseudomallei is present in the environment in many parts of the world and causes the often-fatal disease melioidosis. The sensitive detection and quantification of B. pseudomallei in the environment are a prerequisite for assessing the risk of infection. We recently reported the direct detection of B. pseudomallei in soil samples using a quantitative PCR (qPCR) targeting a single type three secretion system 1 (TTSS1) gene. Here, we extend the qPCR-based analysis of B. pseudomallei in soil by validating novel qPCR gene targets selected from a comparative genomic analysis. Two hundred soil samples from two rice paddies in northeast Thailand were evaluated, of which 47% (94/200) were B. pseudomallei culture positive. The TTSS1 qPCR and two novel qPCR assays that targeted open reading frames (ORFs) BPSS0087 and BPSS0745 exhibited detection rates of 76.5% (153/200), 34.5% (69/200), and 74.5% (150/200), respectively. The combination of TTSS1 and BPSS0745 qPCR increased the detection rate to 90% (180/200). Combining the results of the three qPCR assays and the BPSS1187 nested PCR previously published, all 200 samples were positive by at least one PCR assay. Samples positive by either TTSS1 (n = 153) or BPSS0745 (n = 150) qPCR were more likely to be direct-culture positive, with odds ratios of 4.0 (95% confidence interval [CI], 1.7 to 9.5; P < 0.001) and 9.0 (95% CI, 3.1 to 26.4; P < 0.001), respectively. High B. pseudomallei genome equivalents correlated with high CFU counts by culture. In conclusion, multitarget qPCR improved the B. pseudomallei detection rate in soil samples and predicted culture positivity. This approach has the potential for use as a sensitive environmental screening method for B. pseudomallei.

IMPORTANCE The worldwide environmental distribution of the soil bacterium Burkholderia pseudomallei remains to be determined. So far, most environmental studies have relied on culture-based approaches to detect this pathogen. Since current culture methods are laborious, are time consuming, and have limited sensitivity, culture-independent and more sensitive methods are needed. In this study, we show that a B. pseudomallei-specific qPCR approach can detect significantly higher numbers of B. pseudomallei-positive soil samples from areas where it is endemic compared with that from culture. The use of multiple independent B. pseudomallei-specific qPCR targets further increased the detection rate of B. pseudomallei compared with that from single targets. Samples with a high molecular B. pseudomallei load were more likely to be culture positive. We conclude that our quantitative multitarget approach might be useful in defining areas where there is a risk of B. pseudomallei infections in different parts of the world.

Burden of bloodstream infection in an area of Mid-Norway 2002-2013: a prospective population-based observational study

BACKGROUND

Studies from several countries indicate that the incidence and mortality of bloodstream infection (BSI) have been increasing over time.

METHODS

We studied the burden of disease and death related to BSI in a defined geographical area of Mid-Norway, where BSI episodes were prospectively recorded by the same microbiological department during 12 consecutive years. Death from BSI was defined as death within 30 days of BSI detection. Age and sex standardized incidence and mortality rates and case fatality rates were calculated.

RESULTS

Between 2002 and 2013, 1995 episodes of BSI in 1719 patients aged 16 to 99 years were included. The overall incidence of BSI was 215 per 100,000 person-years. The incidence increased exponentially with age, particularly in males. The incidence increased from 205 to 223 per 100,000 person-years from 2002-07 to 2008-13. Escherichia coli was the most frequently isolated infective agent, followed by Streptococcus pneumoniae and Staphylococcus aureus. The rate of S. pneumoniae BSI decreased over time in males (on average by 9.2% annually), but not in females. The total rate of BSI microbes with acquired resistance increased slightly over time, but did not exceed 2 episodes per 100,000 person-years. The mortality of BSI was 32 per 100,000 person-years, higher in males than in females (36 vs. 28 per 100,000 person-years) and was significantly higher in old age, particularly in males. The total BSI mortality was similar in the first and second halves of the study period, but the mortality of S. pneumoniae BSI decreased in males (15.0% annually). The crude case fatality decreased from the first to the second half of the study period (17.2% to 13.1%; p = 0.014). The rate of blood culture sampling increased more than twofold during the study period.

CONCLUSIONS

The mortality of BSI remained stable during 2002-2013. At the same time, BSI incidence increased and case fatality rate decreased, perhaps because an increased rate of blood culture sampling may have led to improved detection of milder BSI episodes. Very low, yet slightly increasing rates of microbes with acquired resistance were observed.

Perturbation of the two-component signal transduction system, BprRS, results in attenuated virulence and motility defects in Burkholderia pseudomallei

Background

Burkholderia pseudomallei is the causative agent of melioidosis, a severe invasive disease of humans and animals. Initial screening of a B. pseudomallei signature-tagged mutagenesis library identified an attenuated mutant with a transposon insertion in a gene encoding the sensor component of an uncharacterised two-component signal transduction system (TCSTS), which we designated BprRS.

Results

Single gene inactivation of either the response regulator gene (bprR) or the sensor histidine kinase gene (bprS) resulted in mutants with reduced swarming motility and reduced virulence in mice. However, a bprRS double mutant was not attenuated for virulence and displayed wild-type levels of motility. The transcriptomes of the bprS, bprR and bprRS mutants were compared with the transcriptome of the parent strain K96243. Inactivation of the entire BprRS TCSTS (bprRS double mutant) resulted in altered expression of only nine genes, including both bprR and bprS, five phage-related genes and bpss0686, encoding a putative 5, 10-methylene tetrahydromethanopterin reductase involved in one carbon metabolism. In contrast, the transcriptomes of each of the bprR and bprS single gene mutants revealed more than 70 differentially expressed genes common to both mutants, including regulatory genes and those required for flagella assembly and for the biosynthesis of the cytotoxic polyketide, malleilactone.

Conclusions

Inactivation of the entire BprRS TCSTS did not alter virulence or motility and very few genes were differentially expressed indicating that the definitive BprRS regulon is relatively small. However, loss of a single component, either the sensor histidine kinase BprS or its cognate response regulator BprR, resulted in significant transcriptomic and phenotypic differences from the wild-type strain. We hypothesize that the dramatically altered phenotypes of these single mutants are the result of cross-regulation with one or more other TCSTSs and concomitant dysregulation of other key regulatory genes.

Melioidosis in New Caledonia: a dominant strain in a transmission hotspot

Melioidosis is an infectious disease caused by Burkholderia pseudomallei, a bacterium endemic in Southeast Asia and northern Australia. In New Caledonia, sporadic cases were first described in 2005; since then, more cases have been identified. To improve our understanding of melioidosis epidemiology in New Caledonia, we compared the local cases and B. pseudomallei isolates with those from endemic areas. Nineteen melioidosis cases have been diagnosed in New Caledonia since 1999, mostly severe and with frequent bacteraemia, leading to three (16%) fatalities. All but one occurred in the North Province. Besides sporadic cases caused by non-clonal strains, we also identified a hotspot of transmission related to a clonal group of B. pseudomallei that is phylogenetically related to Australian strains.

The Effect of Brief Exposure to Sub-Therapeutic Concentrations of Chlorhexidine Digluconate on the Susceptibility of Staphylococci to Platelet Microbicidal Protein

BACKGROUND

Antiseptic agents are widely used in hospitals and are essential when prevention and control of nosocomial infections is required. It is necessary to consider several aspects that affect the biocide activity because they have direct impact on the nosocomial infection rate. Organisms belonging to the Staphylococcus genus are involved in such infections and chlorhexidine digluconate (CHXD) is one of the most used antiseptic agents for human and animal health. In the context of such infections, anti-bacterial peptides have been isolated from platelets and have been termed platelet microbicidal proteins (PMP). Platelet microbicidal proteins have been shown to enhance the bacterial inhibitory activities of sub-therapeutic concentrations of antibiotics. The main objective of this study was to investigate the effect of brief exposure to different sub-therapeutic concentrations of CHXD on the susceptibility of staphylococci to PMP.

METHODS

The influence of brief exposure to three different sub-therapeutic concentrations of CHXD (0.005%, 0.0025%, and 0.00125%) on the subsequent staphylocidal effect of PMP was evaluated.

RESULTS

Among all clinical staphylococcal strains studied, all isolates were considered to be resistant to the bactericidal action of PMP. Exposure of staphylococci to CHXD prior to PMP resulted in significantly increased staphylococcal killing compared with the killing achieved with PMP alone. This enhanced effect was most marked for concentrations of CHXD of 0.005%.

CONCLUSION

The combined data indicate that PMP exerts cooperative bactericidal effect with CHXD. The anti-staphylococcal PMP and CHXD synergistic activity in vitro demonstrated in the present study make these molecules potentially useful for preventing endovascular catheter-associated infections. Future research based on animal and human models is needed to elucidate the in vivo efficacies and toxicities and utility in clinical practice.

Paediatric bacteraemias in tropical Australia

AIM

Bacteraemias in children are an important cause of morbidity and mortality. Knowledge of local epidemiology and trends is important to inform practitioners of likely pathogens in the sick child. This study aimed to determine trends over time in pathogenic organisms causing paediatric bacteraemia in North Queensland and to audit a hospital's blood culture results with respect to contamination rate.

METHODS

This was a retrospective review of 8385 blood cultures collected from children attending a tertiary centre in North Queensland over a 10-year period (2001-2010).

RESULTS

There were 696 positive blood cultures (8.3%) with 70 different bacterial species detected. Gram-positive and Gram-negative bacteria accounted for 48.6% and 51.4% of isolates, respectively. Overall, bacteraemia accounted for 4.7 per 1000 admissions. The rate of contamination was 60.6% among positive blood cultures and 5.0% for all blood cultures sampled. These results were compared with previous published reports. Notable differences were seen in the frequencies of Salmonella and group A Streptococcus bacteraemias in North Queensland when compared with other reports. There was also a decline in vaccine-preventable infections such as S. pneumoniae and an increasing trend of community-acquired MRSA bacteraemia.

CONCLUSION

This study has demonstrated the unique profile of causative pathogens of paediatric bacteraemias in tropical Australia. In light of the increasing prevalence of MRSA, empiric treatment for sepsis for children in this region needs to be reconsidered.

In situ hybridization to detect and identify Burkholderia pseudomallei in human melioidosis

Burkholderia pseudomallei causes a potentially fatal infection called melioidosis. We have developed a nonfluorescent, colorimetric in situ hybridization assay using a specific probe to target 16s rRNA of B. pseudomallei in formalin-fixed, paraffin-embedded infected tissues for diagnostic purposes and to study infectious disease pathology. A 63-base pair DNA probe was synthesized and labeled with digoxigenin by PCR. Probe specificity was confirmed by BLAST analysis and by testing on appropriate microbial controls. The in situ hybridization assay was specifically and consistently positive for B. pseudomallei, showing strongly and crisply stained, single bacillus and bacilli clusters in mainly inflamed tissues in seven human acute melioidosis cases and experimentally infected mouse tissues. Intravascular and extravascular bacilli were detected in both intracellular and extracellular locations in various human organs, including lung, spleen, kidney, liver, bone marrow, and aortic mycotic aneurysm, particularly in the inflamed areas. Intravascular, intracellular bacteria in melioidosis have not been previously reported. Although the identity of infected intravascular leukocytes has to be confirmed, extravascular, intracellular bacilli appear to be found mainly within macrophages and neutrophils. Rarely, large intravascular, extracellular bacillary clusters/emboli could be detected in both human and mouse tissues. B. cepacia and non-Burkholderia pathogens (16 microbial species) all tested negative. Nonpathogenic B. thailandensis showed some cross-hybridization but signals were less intense. This in situ hybridization assay could be usefully adapted for B. pseudomallei identification in other clinical specimens such as pus and sputum.

Analysis of community- and hospital-acquired bacteraemia during a recent 5-year period

There are sparse data concerning sex- and age-specific characteristics of community-acquired bacteraemia (CAB) and hospital-acquired bacteraemia (HAB). Between January 2008 and December 2012, we identified 2956 bacteraemia cases, which we classified as CAB, HAB or healthcare-associated bacteraemia (HCAB). Almost half of the pathogens were Escherichia coli in CAB patients. By contrast, Staphylococcus aureus was most frequent (16.2 %) in HAB patients. HCAB showed mixed features of CAB and HAB. In CAB, E. coli was significantly more abundant in females than in males (56.9  vs 24.3 %, respectively). This trend was most striking in young adults (20–39 years) (77.2 % in females vs 11.4 % in males). HAB cases showed greater heterogeneity in their associated pathogens. The extended-spectrum β-lactamase-positive rates of E. coli and Klebsiella pneumoniae, respectively, were 31.3 and 33.8 % in HAB and 8.8 and 8.4 % in CAB. The non-susceptibility rates of S. aureus to oxacillin were 37.4 % in CAB and 73.0 % in HAB. In conclusion, CAB and HAB showed different distributions of micro-organisms, and these distributions also differed with patient age and sex. In addition, antimicrobial susceptibility needs to be monitored separately.

Epidemiology of bacteremia in young hospitalized infants in Vientiane, Laos, 2000-2011

As data about the causes of neonatal sepsis in low-income countries are inadequate, we reviewed the etiology and antibiotic susceptibilities of bacteremia in young infants in Laos. As Staphylococcus aureus is the leading cause of bacteremia in Lao infants, we also examined risk factors for this infection, in particular the local practice of warming mothers during the first weeks postpartum with hot coals under their beds (hot beds). Clinical and laboratory data regarding infants aged 0-60 days evaluated for sepsis within 72 h of admission to Mahosot Hospital in Vientiane, Laos, were reviewed, and 85 of 1438 (5.9%) infants' blood cultures grew a clinically significant organism. Most common were S. aureus, Escherichia coli and Klebsiella pneumoniae. Whereas no methicillin-resistant S. aureus was found, only 18% of E. coli isolates were susceptible to ampicillin. A history of sleeping on a hot bed with mother was associated with S. aureus bacteremia (odds ratio 4.8; 95% confidence interval 1.2-19.0).

The In Vitro Antibiotic Susceptibility of Malaysian Isolates of Burkholderia pseudomallei

Acute melioidosis may present as localised or septicaemic infections and can be fatal if left untreated. Burkholderia pseudomallei resistant to antibiotics used for the treatment of melioidosis had been reported. The aim of this study was to determine the in vitro antibiotic susceptibility patterns of Burkholderia pseudomallei isolated in Malaysia to a panel of antibiotics used for the treatment of melioidosis and also to potential alternative antibiotics such as tigecycline, ampicillin/sulbactam, and piperacillin/tazobactam. A total of 170 Burkholderia pseudomallei isolates were subjected to minimum inhibitory concentration determination using E-test method to eleven antibiotics. All isolates were sensitive to meropenem and piperacillin/tazobactam. For ceftazidime, imipenem, amoxicillin/clavulanic acid, and doxycycline resistance was observed in 1 isolate (0.6%) for each of the antibiotics. Trimethoprim/sulfamethoxazole resistance was observed in 17 (10%) isolates. For other antibiotics, ampicillin/sulbactam, chloramphenicol, tigecycline, and ciprofloxacin resistance were observed in 1 (0.6%), 6 (3.5%), 60 (35.3%) and 98 (57.7%) isolates respectively. One isolate B170/06 exhibited resistance to 4 antibiotics, namely, ciprofloxacin, chloramphenicol, trimethoprim/sulfamethoxazole, and tigecycline. In conclusion, the Malaysian isolates were highly susceptible to the current antibiotics used in the treatment of melioidosis in Malaysia. Multiple resistances to the antibiotics used in the maintenance therapy are the cause for a concern.

Community-acquired, healthcare-associated and hospital-acquired bloodstream infection definitions in children: a systematic review demonstrating inconsistent criteria

BACKGROUND

Historically, bacterial infections were categorized as either community-acquired (CA) or hospital-acquired (HA). However, the CA/HA dichotomy no longer adequately reflects patterns of emerging healthcare-associated (HCA) infections in complex patients managed between hospital and the community. Studies trying to define this evolving epidemiology often excluded children.

AIM

To identify what criteria have been used to distinguish between CA, HCA and HA bloodstream infections (BSIs) in children, and the proportional distribution of CA, HCA and HA among total BSIs and by organism.

METHODS

We systematically reviewed published literature from PubMed, UK Department of Health and US Centers for Disease Control and Prevention websites.

FINDINGS

Results from 23 studies and the websites highlighted the use of inconsistent criteria. There were 13 and 15 criteria variations for CA and HA BSI respectively, although a 48h cut-off for cultures sampled post admission was most commonly reported. Five studies used variable clinical criteria to define HCA. The mean proportion of paediatric CA BSI in nine studies was 50%. Only four BSI organisms from five studies were predominantly CA (Streptococcus pneumoniae, Salmonella spp.) or HA (coagulase-negative staphylococci, Enterococcus spp.), whereas Pseudomonas spp., Klebsiella spp. and Enterobacter spp. did not clearly fit into either category.

CONCLUSIONS

Our study reveals inconsistent use of criteria, and a lack of evidence upon which to base them, to distinguish between CA, HCA and HA BSI in children. Criteria for CA, HCA and HA BSI need to be developed using population-based studies that consider patients' clinical characteristics, recent healthcare exposure as well as isolated organism species.

Epidemiology, microbiology and mortality associated with community-acquired bacteremia in northeast Thailand: a multicenter surveillance study

BACKGROUND

National statistics in developing countries are likely to underestimate deaths due to bacterial infections. Here, we calculated mortality associated with community-acquired bacteremia (CAB) in a developing country using routinely available databases.

METHODS/PRINCIPAL FINDINGS

Information was obtained from the microbiology and hospital database of 10 provincial hospitals in northeast Thailand, and compared with the national death registry from the Ministry of Interior, Thailand for the period between 2004 and 2010. CAB was defined in patients who had pathogenic organisms isolated from blood taken within 2 days of hospital admission without a prior inpatient episode in the preceding 30 days. A total of 15,251 CAB patients identified, of which 5,722 (37.5%) died within 30 days of admission. The incidence rate of CAB between 2004 and 2010 increased from 16.7 to 38.1 per 100,000 people per year, and the mortality rate associated with CAB increased from 6.9 to 13.7 per 100,000 people per year. In 2010, the mortality rate associated with CAB was lower than that from respiratory tract infection, but higher than HIV disease or tuberculosis. The most common causes of CAB were Escherichia coli (23.1%), Burkholderia pseudomallei (19.3%), and Staphylococcus aureus (8.2%). There was an increase in the proportion of Extended-Spectrum Beta-Lactamases (ESBL) producing E. coli and Klebsiella pneumoniae over time.

CONCLUSIONS

This study has demonstrated that national statistics on causes of death in developing countries could be improved by integrating information from readily available databases. CAB is neglected as an important cause of death, and specific prevention and intervention is urgently required to reduce its incidence and mortality.

Bacteraemias in tropical Australia: changing trends over a 10-year period

Bacteraemia is an important cause of morbidity and mortality worldwide. This is the largest reported study of bacteraemias in Australia. The presence of organisms endemic to the tropical region and the changing trends described have significant implications for empirical antibiotic therapy. This retrospective study examined 8976 blood cultures from Townsville Hospital, a regional Australian hospital located in the tropics over a 10-year period. The rate of bacteraemic episodes during the study period was 10.12 per 1000 admissions. Intravenous devices (18.7%), immunosuppressive therapy (16.1%), and urinary tract infections (16.1%) were important sources for bacteraemia. The most common organisms were Staphylococcus aureus (20.9%) and Escherichia. coli (15.6%). A significant reduction was observed in S. aureus susceptibility to clindamycin (P < 0.05) and in E. coli susceptibility to gentamicin. Organisms isolated that were of relevance to the tropics of Australia included Burkholderia pseudomallei, Group A streptococcus, and Brucella suis.

Invasive Bacterial Pathogens and their Antibiotic Susceptibility Patterns in Jimma University Specialized Hospital, Jimma, Southwest Ethiopia

Background

Presence of microorganisms in the circulating blood whether continuously or intermittently is a threat to every organ in the body. Approximately 200,000 cases of bacteraemia occur annually with mortality rates ranging from 20–50%. Early diagnosis and appropriate treatment of these infections can make the difference between life and death. The aim of the present study was to determine the bacterial flora of the blood stream infections and their antibiotic susceptibility pattern.

Methods

A cross sectional study was conducted on 260 adult febrile patients in Jimma University Specialized Hospital from 27 October 2009 to 26 March 2010. The positive blood cultures were examined and the organisms were identified as per standard procedures. Antimicrobial testing was performed for all isolates by disk diffusion techniques, according to Clinical Laboratory Standards Institute guide lines. The data was analyzed using SPSS for windows version 16 and Microsoft Office Excel.

Results

From the total of two hundred sixty blood specimens only 23(8.8%) were positive to seven different types of bacteria. The isolated bacteria were: Coagulase negative staphylococci 6(26.1%), S. aureus 5 (21.7%), S. pyogens 3 (13.0%), E. coli 4(17.4%), K. pneumoniae 3(13.0%), Salmonella spp. 1(4.3%), and Citrobacter spp. 1(4.3%). The isolates showed high rates of resistance to most antibiotics tested. The range of resistance for gram positive bacteria were 0% to 85.7%, and for gram negative from 0% to 100%. None of the isolates were resistance to ciprofloxacin and ceftriaxone.

Conclusion

Our study result showed the presence of invasive bacterial pathogens with high rate of resistance to most commonly used antibiotics used to treat bacterial infections. Therefore, timely investigation of bacterial flora of the blood stream infections and monitoring of their antibiotic resistance pattern plays an important role in reduction of the incidence of blood stream infections.

Ceftazidime resistance in Burkholderia pseudomallei: first report from India

Melioidosis, a disease of public health importance in Southeast Asia and Northern Australia, of late has shown an increasing trend in India, particularly Southern India. We describe a case of a 39-year-old diabetic patient with left elbow septic arthritis, multiple liver, splenic abscesses, pneumonia, pleural effusion, followed by sepsis syndrome. Blood cultures and culture of the joint aspirate yielded pure growth of Burkholderia pseudomallei (B. pesudomallei), sensitive to carbapenem, co-trimoxazole and resistant to ceftazidime. The patient was successfully treated with imipenem- cilastin. He was discharged on co-trimoxazole to complete the 24 weeks course and follow-up has continued to date. The patient continues to remain asymptomatic. The case re-emphasizes the need to monitor the trend of B. pseudomallei in India, particularly the development of ceftazidime resistance, which incidentally is the drug of choice.

Burkholderia pseudomallei triggers altered inflammatory profiles in a whole-blood model of type 2 diabetes-melioidosis comorbidity

Melioidosis is a potentially fatal disease caused by the bacterium Burkholderia pseudomallei. Type 2 diabetes (T2D) is the most common comorbidity associated with melioidosis. B. pseudomallei isolates from melioidosis patients with T2D are less virulent in animal models than those from patients with melioidosis and no identifiable risk factors. We developed an ex vivo whole-blood assay as a tool for comparison of early inflammatory profiles generated by T2D and nondiabetic (ND) individuals in response to a B. pseudomallei strain of low virulence. Peripheral blood from individuals with T2D, with either poorly controlled glycemia (PC-T2D [n = 6]) or well-controlled glycemia (WC-T2D [n = 8]), and healthy ND (n = 13) individuals was stimulated with B. pseudomallei. Oxidative burst, myeloperoxidase (MPO) release, expression of pathogen recognition receptors (TLR2, TLR4, and CD14), and activation markers (CD11b and HLA-DR) were measured on polymorphonuclear (PMN) leukocytes and monocytes. Concentrations of plasma inflammatory cytokine (interleukin-6 [IL-6], IL-12p70, tumor necrosis factor alpha [TNF-α], monocyte chemoattractant protein 1 [MCP-1], IL-8, IL-1β, and IL-10) were also determined. Following stimulation, oxidative burst and MPO levels were significantly elevated in blood from PC-T2D subjects compared to controls. Differences were also observed in expression of Toll-like receptor 2 (TLR2), CD14, and CD11b on phagocytes from T2D and ND individuals. Levels of IL-12p70, MCP-1, and IL-8 were significantly elevated in blood from PC-T2D subjects compared to ND individuals. Notably, differential inflammatory responses of PC-T2D, WC-T2D, and ND individuals to B. pseudomallei occur independently of bacterial load and confirm the efficacy of this model of T2D-melioidosis comorbidity as a tool for investigation of dysregulated PMN and monocyte responses to B. pseudomallei underlying susceptibility of T2D individuals to melioidosis.

Population-based laboratory assessment of the burden of community-onset bloodstream infection in Victoria, Canada

Although community-onset bloodstream infection (BSI) is recognized as a major cause of morbidity and mortality, its epidemiology has not been well defined in non-selected populations. We conducted population-based laboratory surveillance in the Victoria area, Canada during 1998-2005 in order to determine the burden associated with community-onset BSI. A total of 2785 episodes were identified for an overall annual incidence of 101·2/100,000. Males and the very young and the elderly were at highest risk. Overall 1980 (71%) episodes resulted in hospital admission for a median length of stay of 8 days; the total days of acute hospitalization associated with community-onset BSI was 28 442 days or 1034 days/100,000 population per year. The in-hospital case-fatality rate was 13%. Community-onset BSI is associated with a major burden of illness. These data support ongoing and future preventative and research efforts aimed at reducing the major impact of these infections.

Strategies for Intracellular Survival of Burkholderia pseudomallei

Burkholderia pseudomallei is the causative agent of melioidosis, a disease with high mortality that is prevalent in tropical regions of the world. A key component of the pathogenesis of melioidosis is the ability of B. pseudomallei to enter, survive, and replicate within mammalian host cells. For non-phagocytic cells, bacterial adhesins have been identified both on the bacterial surface and associated with Type 4 pili. Cell invasion involves components of one or more of the three Type 3 Secretion System clusters, which also mediate, at least in part, the escape of bacteria from the endosome into the cytoplasm, where bacteria move by actin-based motility. The mechanism of actin-based motility is not clearly understood, but appears to differ from characterized mechanisms in other bacterial species. A small proportion of intracellular bacteria is targeted by host cell autophagy, involving direct recruitment of LC3 to endosomes rather than through uptake by canonical autophagosomes. However, the majority of bacterial cells are able to circumvent autophagy and other intracellular defense mechanisms such as the induction of inducible nitric oxide synthase, and then replicate in the cytoplasm and spread to adjacent cells via membrane fusion, resulting in the formation of multi-nucleated giant cells. A potential role for host cell ubiquitin in the autophagic response to bacterial infection has recently been proposed.

Influence of referral bias on the clinical characteristics of patients with Gram-negative bloodstream infection

Referral bias can influence the results of studies performed at tertiary-care centres. In this study, we evaluated demographic and microbiological factors that influenced referral of patients with Gram-negative bloodstream infection (BSI). We identified 2919 and 846 unique patients with Gram-negative BSI in a referral cohort of patients treated at Mayo Clinic Hospitals and a population-based cohort of Olmsted County, Minnesota, residents between 1 January 1998 and 31 December 2007, respectively. Multivariable logistic regression analysis was used to determine factors associated with referral. Elderly patients aged ≥80 years with Gram-negative BSI were less likely to be referred than younger patients [odds ratio (OR) 0·43, 95% confidence intervals (CI) 0·30-0·62] as were females (OR 0·63, 95% CI 0·53-0·74). After adjusting for age and gender, bloodstream isolates of Escherichia coli (OR 0·50, 95% CI 0·43-0·58) and Proteus mirabilis (OR 0·49, 95% CI 0·30-0·82) were underrepresented in the referral cohort; and Pseudomonas aeruginosa (OR 2·26, 95% CI 1·70-3·06), Enterobacter cloacae (OR 2·31, 95% CI 1·53-3·66), Serratia marcescens (OR 2·34, 95% CI 1·33-4·52) and Stenotrophomonas maltophilia (OR 17·94, 95% CI 3·98-314·43) were overrepresented in the referral cohort. We demonstrated that demographic and microbiological characteristics of patients with Gram-negative BSI had an influence on referral patterns. These factors should be considered when interpreting results of investigations performed at tertiary-care centres.

Melioidosis presenting as sepsis syndrome: a case report

Melioidosis is an important disease in Asia and Australia. It is very rare in Venezuela. We describe the case of a 50-year-old diabetic patient with several episodes of right tibial osteomyelitis, left shoulder arthritis, sternal osteomyelitis, right parietal osteomyelitis, and subperiosteal abscess, followed by septic arthritis of the right knee. In all cases Gram stain smear showed Gram-negative bacilli. Culture yielded Burkholderia pseudomallei, susceptible to third- and fourth-generation cephalosporins, ciprofloxacin and aztreonam, and resistant to aminoglycosides. He developed sepsis syndrome. Blood cultures and culture of abscess and joint fluids also revealed B. pseudomallei. The patient was treated with ceftazidime and ciprofloxacin, then cefepime and trimethoprim-sulfamethoxazole. He was discharged with suppressive therapy consisting of oral doxycycline and trimethoprim-sulfamethoxazole, and follow-up has continued to date. At this time he remains asymptomatic. Melioidosis is an extremely rare disease in our country. To our knowledge, this is only the second case reported in Venezuela.

Secular trends of healthcare-associated infections at a teaching hospital in Taiwan, 1981-2007

The National Taiwan University Hospital (NTUH) adopted international guidelines for surveillance and control of healthcare-associated infection (HCAI) in 1981. This report describes the secular trends in HCAI at the NTUH over the past 27 years according to site of infection, aetiological agents and control measures. Clinical and microbiological data were collected by infection prevention and control nurses using a standardised case-record form. Specific control programmes were implemented and/or intensified as needed. Poisson or negative binomial regression analysis was used to quantify time trends of the incidence of HCAI. The annual number of discharges increased from 25 074 to 91 234 with a parallel increase in the Charlson comorbidity index. Active HCAI surveillance and periodic feedback were associated with a marked decrease in surgical site infections from 1981 to 2007 (2.5 vs 0.5 episodes per 100 procedures, P < 0.0001). On the other hand, there was a 4.8-fold increase in bloodstream infections (BSIs) (0.39 vs 1.88 episodes per 100 discharges, P < 0.0001). The average annual increase of pathogen-specific HCAI incidence during 1981–2007 was 11.4% for meticillin-resistant Staphylococcus aureus (MRSA), 75.4% for extensively drug-resistant A. baumannii (XDRAB), and 7.5% for Candida albicans (P < 0.0001, respectively). The infection prevention and control programme was upgraded in 2004 by implementing annual, intensive, project-based control programmes, and decreases in rates of HCAI, BSI, MRSA and XDRAB were observed. This long term study demonstrates the need to couple surveillance of HCAI with focused control programmes. Hospitals must invest in adequate manpower to accomplish these goals.

Two nations: racial disparities in bloodstream infections recorded at Alice Springs Hospital, central Australia, 2001-2005

OBJECTIVE

To compare bloodstream infection (BSI) rates, pathogens and mortality among Indigenous and non-Indigenous adults in central Australia.

DESIGN, PARTICIPANTS AND SETTING

Retrospective study of adult patients (aged > or = 15 years) admitted to Alice Springs Hospital (ASH) between 1 January 2001 and 31 December 2005. Patients were followed up until 30 June 2008.

MAIN OUTCOME MEASURES

Admission-based and population-based BSI rates and mortality rates for Indigenous and non-Indigenous adults.

RESULTS

During the study period, there were 824 BSI episodes (Indigenous, 753; non-Indigenous, 71). The admission-based BSI rate for Indigenous patients was 26.5 (95% CI, 26.4-26.6) per 1000 adult admissions, compared with 5.2 (95% CI, 5.1-5.2) per 1000 adult admissions for non-Indigenous patients (infection rate ratio [IRR], 5.13 [95% CI, 5.10-5.18]). The population-based BSI rate was 1354.7 (95% CI, 1256.3-1460.8) per 100 000 persons per year among Indigenous patients and 69.9 (95% CI, 55.1-88.6) per 100 000 persons per year among non-Indigenous patients (IRR, 19.4 [95% CI, 15.1-24.9]). These differences were not explained by higher comorbidity levels among Indigenous patients. Human T-cell lymphotropic virus type 1 and Strongyloides stercoralis infected 43% and 35%, respectively, of Indigenous patients tested. The risk of death during the follow-up period was 32.1% for Indigenous and 13.4% for non-Indigenous patients (hazard ratio [HR], 2.69 [95% CI, 1.38-5.25]; P = 0.004). Mortality rates were higher among Indigenous patients who had more than a single BSI (HR, 1.86 [95% CI, 1.32-2.62]; P < 0.001). The mean age at death was 48.5 years (SD, 16.2 years) for Indigenous patients and 75.1 years (SD, 18.7 years) for non-Indigenous patients (P < 0.001).

CONCLUSION

Indigenous adults living in central Australia experience BSI rates that are among the highest reported in the world. These are associated with a high risk of death, and are a likely consequence of the poor socioeconomic circumstances of Indigenous people.

Pneumonia risk stratification in tropical Australia: does the SMART-COP score apply?

OBJECTIVE

To examine the performance in tropical northern Australia of SMART-COP, a simple scoring system developed in temperate Australia to predict the need for intensive respiratory or vasopressor support (IRVS) in pneumonia patients.

DESIGN, SETTING AND PATIENTS

A prospective observational study of patients admitted to Royal Darwin Hospital in the Northern Territory with sepsis between August 2007 and May 2008. Chest x-rays were reviewed to confirm pneumonia, and each patient's SMART-COP score was assessed against the need for IRVS.

RESULTS

Of 206 patients presenting with radiologically confirmed pneumonia, 184 were eligible for inclusion. The mean age of patients was 50.1 years, 65% were Indigenous and 56% were men. Overall, 38 patients (21%) required IRVS, and 18 patients (10%) died by Day 30. A SMART-COP score of >or= 3 had a sensitivity of only 71% for predicting the need for IRVS and 67% for 30-day mortality. As the variables most strongly associated with IRVS were serum albumin level < 35 g/L (odds ratio, 6.8) and Indigenous status (odds ratio, 2.3), we tested a modified scoring system (SMART-COP) that used a higher weighting for albumin and included Indigenous status. A SMART-COP score of >or= 3 had a sensitivity of 97% for IRVS and 100% for 30-day mortality.

CONCLUSIONS

The SMART-COP score underestimates the severity of pneumonia in tropical northern Australia, but can be improved by using locally relevant additions.

Cutaneous melioidosis in the tropical top end of Australia: a prospective study and review of the literature

BACKGROUND

Burkholderia pseudomallei is endemic in northern Australia, and melioidosis is a common cause of sepsis in the region.

METHODS

We summarized the cutaneous manifestations of melioidosis from a prospective cohort of 486 patients with culture-confirmed melioidosis in northern Australia, and we compared those who had primary skin melioidosis with those who had other forms of melioidosis.

RESULTS

Primary skin melioidosis occurred in 58 patients (12%). Secondary skin melioidosis--multiple pustules from hematogenous spread--was present in 10 patients (2%). Patients with primary skin melioidosis were more likely to have chronic presentations (duration, >or=2 months). On multivariate analysis, patients with primary cutaneous melioidosis were more likely to be children aged <or=15 years (adjusted odds ratio, 8.50; 95% confidence interval [CI], 3.24-22.28) and to have a history of occupational exposure to B. pseudomallei (adjusted odds ratio, 3.12; 95% CI, 1.56-6.25) but were less likely to have typical risk factors--including diabetes (adjusted odds ratio, 0.26; 95% CI, 0.12-0.56), excessive alcohol intake (adjusted odds ratio, 0.45; 95% CI, 0.22-0.90), and chronic lung disease (adjusted odds ratio, 0.26; 95% CI, 0.10-0.67). Of those patients with primary skin melioidosis, 1 patient was bacteremic and none had severe sepsis or died from melioidosis. Four (7%) of the 58 patients presenting with primary skin melioidosis had disseminated melioidosis, and 1 (2%) experienced a relapse of melioidosis. Nine patients (16%) were cured with a regimen of oral antibiotics alone, and 1 recovered with no therapy.

CONCLUSION

In our cohort, patients with primary skin melioidosis were younger, had fewer underlying medical conditions, and had better outcomes than did those with other forms of melioidosis. There may be a role for exclusive oral antibiotic therapy for some cases of primary skin melioidosis.

Failure of a poster-based educational programme to improve compliance with peripheral venous catheter care in a tertiary hospital. A clinical audit

The objective of this audit was to determine the prevalence of recording the date and time of insertion of peripheral venous catheters (PVCs) in a tertiary hospital setting, and whether this could be improved by a simple poster-based educational programme. The two-phase point prevalence audit covered 1109 adult inpatients at the Royal Darwin Hospital, Australia. The presence or otherwise of a PVC was recorded, along with whether the date and time of insertion of the device was recorded in situ, in the bedside chart or in the clinical notes. Background demographic data were collected along with any identifiable risk factors for catheter-associated bacteraemia. The process was then repeated in the same hospital units following implementation of a simple poster-based educational programme. The prevalence of any dating method (in situ, in the bedside chart or in the clinical notes) was low, at 13.4% and 16.1% in the pre- and post-intervention groups respectively. This difference was not statistically significant (P=0.27). Independent of the poster campaign, patients with risk factors for catheter-associated bacteraemia were more likely to have the insertion date recorded compared to those without (P=0.03). Given the potential cost of catheter-associated bacteraemia to the patient, hospital and community, it is surprising that compliance with an in-house infection control recommendation was so poor. A poster-based education programme alone had little effect in improving the situation.

Acute septicemic melioidosis presenting with acute cholangitis

Melioidosis is a disease prevalent in the tropics, especially in Southeast Asia. The most common clinical presentations are bacteremic pneumonia and abscess formation in various organs. Although a wide variety of disease presentations are reported for melioidosis, acute cholangitis has not been previously reported. Herein, we report a 54-year-old woman who had fever, right upper abdominal pain and jaundice 1 week after a flood caused by a typhoon in southern Taiwan. Acute cholangitis and pneumonia with septic shock caused by Burkholderia pseudomallei were subsequently diagnosed.

Evaluation of bacteremias in a Turkish university hospital: 3-year outcomes

In this retrospective study, the investigators examined blood cultures from patients that had been diagnosed with bacteremias over a 3-y period. The study was conduced at Kocatepe University Hospital (Middle Anatolia, Turkey). Blood samples that arrived at the university's microbiology laboratory between 2002 and 2005 were evaluated retrospectively. These samples were classified as contamination, false positivity, community-acquired bacteremia (CAB), or hospital-acquired bacteremia (HAB). Patient age and sex, foci of bacteremia, present comorbidities, predisposing factors, pathogens, and mortality rates were evaluated. A total of 1783 blood cultures that had been drawn from 1441 patients during this 3-y period were examined retrospectively. Of 354 positive isolates, 61 (17.2%) were CABs and 293 (82.8%) were HABs. In HABs, the most commonly isolated microorganisms were Staphylococcus aureus (37.5%), coagulase-negative staphylococci (29.7%), and Escherichia coli (10.2%); in CABs, the most commonly isolated microorganisms were S aureus (29.5%), Brucella spp (26.2%), and E coli (24.6%). Crude mortality rates were determined to be 15.2% for HABs and 12.7% for CABs. This study yielded data on the most common foci of bacteremia, microbiologic factors, and the epidemiology associated with HABs and CABs. It is hoped that these data will enhance empirical antibiotic therapeutic approaches, thereby preventing delays in treatment and decreasing mortality rates associated with bacteremias.

Bacteremia in children at a regional hospital in Trinidad

OBJECTIVE

The objective of this study was to provide a Trinidadian perspective on pediatric community-acquired and hospital-acquired bacteremia via the documentation of common etiologic agents, antimicrobial profiles of the isolated pathogens, and patient outcome.

METHODS

This was a six-year retrospective study of children with bacteremia admitted to the pediatric wards of the San Fernando General Hospital, Trinidad.

RESULTS

Seven hundred and four episodes of pediatric bacteremia were reviewed during the six-year study period. The predominant isolate was Staphylococcus aureus (23.9%), followed by Pseudomonas aeruginosa (15.5%), Klebsiella pneumoniae (12.5%), and Enterobacter spp (11.1%). The remaining isolates each accounted for less than 10% of total isolates. The mortality rate was highest for P. aeruginosa (39.4%), Streptococcus pneumoniae (22.5%), and Escherichia coli (19.2%). Of the six cases due to Neisseria meningitidis, only two survived. The overall mortality rate for the study period was 15.1%, but varied considerably according to age. All deaths due to P. aeruginosa and E. coli occurred in neonates. Almost 90% and about half of all S. aureus were resistant to ampicillin and erythromycin, respectively; nineteen (11.3%) were methicillin-resistant. More than 95% of K. pneumoniae and more than 87% of Haemophilus influenzae were resistant to ampicillin. Group B streptococci were fully susceptible to ampicillin and amoxicillin-clavulanic acid, but showed >90% and >70% resistance to tetracycline and trimethoprim-sulfamethoxazole, respectively. Of the 40 strains of S. pneumoniae isolated, 10.0% had a minimum inhibitory concentration (MIC) >or=4 microg/mL (resistance) and 12.5% had a MIC=2.0 microg/mL (intermediate resistance) to ceftriaxone, while 7.5% showed intermediate resistance (MIC between 0.12 and 1 microg/mL) and 25.0% showed resistance (MIC >or=2 microg/mL) to penicillin.

CONCLUSION

The bacteremia rate was found to be 8.4% among hospitalized children suspected of having sepsis and from whom a blood culture was positive. Bacteremia was also associated with a high mortality rate of 15.1%. An unusually high level of bacteremia with Gram-negative enteric bacteria was seen, which might indicate cross infection and reflect a breakdown in infection control measures. Relatively high-level resistance of S. pneumoniae to penicillin and ceftriaxone was not seen, even though the overall prevalence of resistance to other antibiotics among other pathogens was relatively low. The drugs that showed the greatest efficacy were imipenem, gentamicin, ciprofloxacin, and the cephalosporins ceftazidime and ceftriaxone.

Burden of community-onset bloodstream infection: a population-based assessment

Although community-onset bloodstream infection (BSI) is recognized to be a major cause of morbidity and mortality, there is a paucity of population-based studies defining its overall burden. We conducted population-based laboratory surveillance for all community-onset BSI in the Calgary Health Region during 2000-2004. A total of 4467 episodes of community-onset BSI were identified for an overall annual incidence of 81.6/100,000. The three species, Escherichia coli, Staphylococcus aureus, and Streptococcus pneumoniae were responsible for the majority of community-onset BSI; they occurred at annual rates of 25.8, 13.5, and 10.1/100,000, respectively. Overall 3445/4467 (77%) episodes resulted in hospital admission representing 0.7% of all admissions to major acute care hospitals. The subsequent hospital length of stay was a median of 9 (interquartile range, 5-15) days; the total days of acute hospitalization attributable to community-onset BSI was 51,146 days or 934 days/100,000 annually. Four hundred and sixty patients died in hospital for a case-fatality rate of 13%. Community-onset BSI is common and has a major patient and societal impact. These data support further efforts to reduce the burden of community-onset BSI.

Use of a single-nucleotide polymorphism genotyping system to demonstrate the unique epidemiology of methicillin-resistant Staphylococcus aureus in remote aboriginal communities

Community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) has emerged as a major public health problem in Australia, as in many other parts of the world. High rates of CA-MRSA skin and soft tissue infection have been reported from Aboriginal communities. We used a single-nucleotide polymorphism (SNP) genotyping typing system based on the multilocus sequence type (MLST) database to investigate the epidemiology of CA-MRSA and methicillin-sensitive S. aureus (MSSA) over a 12-month period in three remote Aboriginal communities of Northern Australia. This was supplemented by real-time PCR for Panton-Valentine leukocidin (PVL) genes, staphylococcal cassette chromosome mec (SCCmec) typing, and antimicrobial susceptibility testing. S. aureus was recovered from pyoderma lesions on 221 occasions and throat swabs on 44 occasions. The median monthly recovery rate of S. aureus from skin sores was 58% (interquartile range, 62 to 78%), and there was no seasonal variation. Twenty-three percent of isolates were CA-MRSA; the proportion was similar across the communities and did not vary over the study period. Erythromycin resistance was found in 47% of CA-MRSA and 21% of MSSA. SNP-based typing identified 14 different clonal complexes (cc); however, cc75 was predominant, accounting for 71% of CA-MRSA isolates. These were confirmed as ST75-like by using an additional SNP and MLST of selected isolates. All but one of the cc75 isolates had SSCmec type IV (one had type V), and all were PVL negative. Monthly tracking of SNP-based cc types showed a highly dynamic process. ST75-MRSA-IV appears to be unique to the region and probably evolved de novo in remote Aboriginal communities.

Biological relevance of colony morphology and phenotypic switching by Burkholderia pseudomallei

Melioidosis is a notoriously protracted illness and is difficult to cure. We hypothesize that the causative organism, Burkholderia pseudomallei, undergoes a process of adaptation involving altered expression of surface determinants which facilitates persistence in vivo and that this is reflected by changes in colony morphology. A colony morphotyping scheme and typing algorithm were developed using clinical B. pseudomallei isolates. Morphotypes were divided into seven types (denoted I to VII). Type I gave rise to other morphotypes (most commonly type II or III) by a process of switching in response to environmental stress, including starvation, iron limitation, and growth at 42 degrees C. Switching was associated with complex shifts in phenotype, one of which (type I to type II) was associated with a marked increase in production of factors putatively associated with in vivo concealment. Isogenic types II and III, derived from type I, were examined using several experimental models. Switching between isogenic morphotypes occurred in a mouse model, where type II appeared to become adapted for persistence in a low-virulence state. Isogenic type II demonstrated a significant increase in intracellular replication fitness compared with parental type I after uptake by epithelial cells in vitro. Isogenic type III demonstrated a higher replication fitness following uptake by macrophages in vitro, which was associated with a switch to type II. Mixed B. pseudomallei morphologies were common in individual clinical specimens and were significantly more frequent in samples of blood, pus, and respiratory secretions than in urine and surface swabs. These findings have major implications for therapeutics and vaccine development.

MRSA—the tip of the iceberg

Methicillin-resistant Staphylococcus aureus (MRSA) strains cause serious nosocomial infections all over the world. Overall, approximately 20% of S. aureus isolates in Europe are reported as methicillin-resistant, whereas in US hospitals the prevalence ranges from 33% to 55%. The past few years have also witnessed an increase in life-threatening community-acquired infections caused by Panton-Valentine leukocidin-producing MRSA in the USA. Increasing use of glycopeptides for treatment of community-acquired MRSA infections may result in higher rates of glycopeptide resistance. Since 1996, five vancomycin-intermediate S. aureus (VISA; vancomycin MIC = 8-16 mg/L) strains have been identified in Europe, Asia and the USA, and vancomycin-resistant S. aureus (VRSA) strains (vancomycin MIC > or = 32 mg/L) have also been reported in the USA between 2002 and 2005. Most infections with VISA and VRSA have occurred in a setting of heavy prior use of glycopeptides and other antimicrobial agents. Emergence of reduced vancomycin susceptibility in S. aureus increases the possibility that currently available antimicrobial agents may become ineffective for treating systemic infections, especially bacteraemia, endocarditis and osteomyelitis. Ceftobiprole is a novel broad-spectrum cephalosporin with expanded activity against Gram-positive bacteria, including MRSA. Ceftobiprole is refractory to the development of endogenous resistance both in vitro and in vivo. The additional activity of ceftobiprole against MRSA strains makes it a potentially important addition to currently available agents.