Epidemiology of Burkholderia cepacia complex in patients with cystic fibrosis, Canada

Burkholderia cenocepacia-mediated inhibition of Staphylococcus aureus growth and biofilm formation

Staphylococcus aureus asymptomatically colonizes the nasal cavity and pharynx of up to 60% of the human population and, as an opportunistic pathogen, can breach its normal habitat, resulting in life-threatening infections. S. aureus infections are of additional concern for populations with impaired immune function such as those with cystic fibrosis (CF) or chronic granulomatous disease. Multi-drug resistance is increasingly common in S. aureus infections, creating an urgent need for new antimicrobials or compounds that improve efficacy of currently available antibiotics. S. aureus biofilms, such as those found in the lungs of people with CF and in soft tissue infections, are notoriously recalcitrant to antimicrobial treatment due to the characteristic metabolic differences associated with a sessile mode of growth. In this work, we show that another CF pathogen, Burkholderia cenocepacia, produces one or more secreted compounds that can prevent S. aureus biofilm formation and inhibit existing S. aureus biofilms. The B. cenocepacia-mediated antagonistic activity is restricted to S. aureus species and perhaps some other staphylococci; however, this inhibition does not necessarily extend to other Gram-positive species. This inhibitory activity is due to death of S. aureus through a contact-independent mechanism, potentially mediated through the siderophore pyochelin and perhaps additional compounds. This works paves the way to better understanding of interactions between these two bacterial pathogens.IMPORTANCEStaphylococcus aureus is a major nosocomial pathogen responsible for infecting thousands of people each year. Some strains are becoming increasingly resistant to antimicrobials, and consequently new treatments must be sought. This paper describes the characterization of one or more compounds capable of inhibiting S. aureus biofilm formation and may potentially lead to development of a new therapeutic.

Colony morphotype variation in Burkholderia: implications for success of applications and therapeutics

The Burkholderia genus includes both environmental and pathogenic isolates known for their phenotypic plasticity and adaptability. Burkholderia spp. are intrinsically resistant to many antibiotics, often requiring prolonged therapies during infection. A key feature of Burkholderia spp. is colony morphotype variation (CMV), which allows for rapid adaptation to environmental changes and influences virulence, antibiotic resistance, and pathogenicity by impacting the expression of key virulence factors such as lipopolysaccharides, extracellular DNA, efflux pumps, and flagella. While alternative treatments, such as vaccines and phage therapies, hold promise, CMV has the potential to undermine their efficacy by modifying essential therapeutic targets. Despite its importance, the prevalence and underlying mechanisms of CMV remain poorly understood, leaving critical gaps in our knowledge that may hinder the development of sustainable solutions for managing Burkholderia infections. Addressing these gaps is crucial not only for improving infection management but also for enabling the safe reuse of Burkholderia in biotechnology, where their plant growth-promoting and bioremediation properties are highly valuable. Our goal is to raise awareness within the scientific community about the significance of CMV in Burkholderia, highlighting the urgent need to uncover the mechanisms driving CMV. A deeper understanding of CMV's role in virulence and resistance is essential to developing robust, long-term therapeutic strategies.

Comprehensive analysis of Burkholderia species head and neck infections: A systematic review

OBJECTIVE

To report the first systematic review and meta-analysis of Burkholderia species infections of the head and neck to facilitate understanding of the disease's demographics, mortality rate, comorbidities associated, symptoms, and antibiotic treatments utilized.

DATA SOURCES

COCHRANE Library, CINAHL, PubMed, and Scopus.

REVIEW METHODS

A systematic review and meta-analysis were performed using PRISMA reporting guidelines. Inclusion criteria included non-surgical patients who were diagnosed with any head and neck Burkholderia infection. Demographics included, patient age and gender. Symptoms, antibiotics given, bacteriology, comorbidities and mortality were analyzed. Meta-analysis of continuous measures (mean), and proportions (%) with a 95 % confidence interval (CI) was conducted. Studies were accessed for bias via the JBI appraisal tool.

RESULTS

There were 740 studies screened with 45 studies (N = 132) being included. In total, 50.1 % were females (95 % CI: 43-57) with a mean patient age of 28.7 years (95 % CI: 25.9 to 31.5). Overall survival rate was 83.4 % (95 % CI: 77.5 to 88.4) and predominant localized symptoms were neck swelling at 38.4 % (95 % CI: 27.5 to 49.9), followed by neck abscess at 34.1 % (27.5 to 41.2) and head and neck suppurative lymphadenitis at 22.9 % (17.3 to 29.4). Main antibiotic treatments included: trimethoprim-sulfamethoxazole at 63.0 % (95 % CI: 55.9 to 69.8), ceftazidime at 47.9 % (40.7 to 55.1), and doxycycline at 26.7 % (10.7 to 33.5).

CONCLUSION

Burkholderia infections exhibit diverse symptoms, which pose a challenge in diagnosis. Additionally, prescription of non-guideline antibiotics highlights the initial difficulty in identifying these organisms as the primary culprit of infection causing delayed treatment.

Acidic pH modulates Burkholderia cenocepacia antimicrobial susceptibility in the cystic fibrosis nutritional environment

IMPORTANCE

Burkholderia cenocepacia causes severe infections in cystic fibrosis (CF) patients. CF patients are prone to reoccurring infections due to the accumulation of mucus in their lungs, where bacteria can adhere and grow. Some of the antibiotics that inhibit B. cenocepacia in the laboratory are not effective for CF patients. A major contributor to poor clinical outcomes is that antibiotic testing in laboratories occurs under conditions that are different from those of sputum. CF sputum may be acidic and have increased concentrations of iron and zinc. Here, we used a medium that mimics CF sputum and found that acidic pH decreased the activity of many of the antibiotics used against B. cenocepacia. In addition, we assessed susceptibility to more than 500 antibiotics and found four active compounds against B. cenocepacia. Our findings give a better understanding of the lack of a relationship between susceptibility testing and the clinical outcome when treating B. cenocepacia infections.

Burkholderia vietnamiensis causing infections in noncystic fibrosis patients in a tertiary care hospital in Mexico

Burkholderia cepacia complex (Bcc) species are opportunistic pathogens widely distributed in the environment and often infect people with cystic fibrosis (CF). This study aims to determine which genomovars of the Bcc can cause infections in non-CF patients from a tertiary care hospital in Mexico and if they carry virulence factors that could increase their pathogenicity. We identified 23 clinical isolates that carry the recA gene. Twenty-two of them belongs to the genomovar V (B. vietnamiensis) and one to the genomovar II (B. multivorans). Thirteen pulsotypes were identified among 22 B. vietnamiensis isolates. All clinical isolates produced biofilm were motile and cytotoxic on murine macrophage-like RAW264.7 and in A549 human lung epithelial cells. In conclusion, B. vietnamiensis causes infections in non-CF patients in a tertiary care hospital in Mexico, rapid identification of this pathogen can help physicians to establish a better antimicrobial treatment.

Antibacterial Activity of a Natural Clay Mineral against Burkholderia cepacia Complex and Other Bacterial Pathogens Isolated from People with Cystic Fibrosis

There is an impending crisis in healthcare brought about by a new era of untreatable infections caused by bacteria resistant to all available antibiotics. Thus, there is an urgent need to identify novel antimicrobial agents to counter the continuing threat posed by formerly treatable infections. We previously reported that a natural mineral clay known as Kisameet clay (KC) is a potent inhibitor of the organisms responsible for acute infections. Chronic bacterial infections present another major challenge to treatment by antimicrobials, due to their prolonged nature, which results in repeated exposure to antibiotics and a constant selection for antimicrobial resistance. A prime example is bacteria belonging to the Burkholderia cepacia complex (Bcc), which particularly causes some of the most serious chronic lung infections in patients with cystic fibrosis (CF) associated with unpredictable clinical outcomes, poor prognosis, and high mortality rates. Eradication of these organisms from CF patients with limited effective antimicrobial options is a major challenge. Novel therapeutic approaches are urgently required. Here, we report the in vitro antibacterial activity of KC aqueous suspensions (1-10% w/v) and its aqueous extract (L100) against a collection of extensively and multi-drug resistant clinical isolates of Bcc, Pseudomonas aeruginosa, and Stenotrophomonas maltophilia isolated from patients with CF. These findings present a potential novel therapy for further investigation in the clinic.

Pseudomonas aeruginosa: Infections, Animal Modeling, and Therapeutics

Pseudomonas aeruginosa is an important Gram-negative opportunistic pathogen which causes many severe acute and chronic infections with high morbidity, and mortality rates as high as 40%. What makes P. aeruginosa a particularly challenging pathogen is its high intrinsic and acquired resistance to many of the available antibiotics. In this review, we review the important acute and chronic infections caused by this pathogen. We next discuss various animal models which have been developed to evaluate P. aeruginosa pathogenesis and assess therapeutics against this pathogen. Next, we review current treatments (antibiotics and vaccines) and provide an overview of their efficacies and their limitations. Finally, we highlight exciting literature on novel antibiotic-free strategies to control P. aeruginosa infections.

Opportunistic Pathogens in Cystic Fibrosis: Epidemiology and Pathogenesis of Lung Infection

Cystic fibrosis (CF) is one of the most common life-shortening genetic diseases in Caucasians. Due to abnormal accumulation of mucus, respiratory failure caused by chronic infections is the leading cause of mortality in this patient population. The microbiology of these respiratory infections includes a distinct set of opportunistic pathogens, including Pseudomonas aeruginosa, Burkholderia spp., Achromobacter spp., Stenotrophomonas maltophilia, anaerobes, nontuberculous mycobacteria, and fungi. In recent years, culture-independent methods have shown the polymicrobial nature of lung infections, and the dynamics of microbial communities. The unique environment of the CF airway predisposes to infections caused by opportunistic pathogens. In this review, we will highlight how the epidemiology and role in disease of these pathogens in CF differ from that in individuals with other medical conditions. Infectious diseases (ID) physicians should be aware of these differences and the specific characteristics of infections associated with CF.

Antibiotherapy in Children with Cystic Fibrosis—An Extensive Review

In cystic fibrosis (CF), the respiratory disease is the main factor that influences the outcome and the prognosis of patients, bacterial infections being responsible for severe exacerbations. The etiology is often multi-microbial and with resistant strains. The aim of this paper is to present current existing antibiotherapy solutions for CF-associated infections in order to offer a reliable support for individual, targeted, and specific treatment. The inclusion criteria were studies about antibiotherapy in CF pediatric patients. Studies involving adult patients or those with only in vitro results were excluded. The information sources were all articles published until December 2021, in PubMed and ScienceDirect. A total of 74 studies were included, with a total number of 26,979 patients aged between 0–18 years. We approached each pathogen individual, with their specific treatment, comparing treatment solutions proposed by different studies. Preservation of lung function is the main goal of therapy in CF, because once parenchyma is lost, it cannot be recovered. Early personalized intervention and prevention of infection with reputable germs is of paramount importance, even if is an asymmetrical challenge. This research received no external funding.

Human Cryptic Host Defence Peptide GVF27 Exhibits Anti-Infective Properties against Biofilm Forming Members of the Burkholderia cepacia Complex

Therapeutic solutions to counter Burkholderia cepacia complex (Bcc) bacteria are challenging due to their intrinsically high level of antibiotic resistance. Bcc organisms display a variety of potential virulence factors, have a distinct lipopolysaccharide naturally implicated in antimicrobial resistance. and are able to form biofilms, which may further protect them from both host defence peptides (HDPs) and antibiotics. Here, we report the promising anti-biofilm and immunomodulatory activities of human HDP GVF27 on two of the most clinically relevant Bcc members, Burkholderia multivorans and Burkholderia cenocepacia. The effects of synthetic and labelled GVF27 were tested on B. cenocepacia and B. multivorans biofilms, at three different stages of formation, by confocal laser scanning microscopy (CLSM). Assays on bacterial cultures and on human monocytes challenged with B. cenocepacia LPS were also performed. GVF27 exerts, at different stages of formation, anti-biofilm effects towards both Bcc strains, a significant propensity to function in combination with ciprofloxacin, a relevant affinity for LPSs isolated from B. cenocepacia as well as a good propensity to mitigate the release of pro-inflammatory cytokines in human cells pre-treated with the same endotoxin. Overall, all these findings contribute to the elucidation of the main features that a good therapeutic agent directed against these extremely leathery biofilm-forming bacteria should possess.

Epidemiology of Burkholderia Infections in People with Cystic Fibrosis in Canada between 2000 and 2017

Rationale: Infections by Burkholderia species bacteria in cystic fibrosis (CF) may be transmissible, necessitating infection control measures, and remain a serious cause of morbidity and mortality. The last major study of Burkholderia epidemiology in Canada included cases up until July 2000 and was marked by the dominance of a limited number of epidemic clones of Burkholderia cenocepacia.Objectives: Describe the nationwide epidemiology of Burkholderia species infections in people with cystic fibrosis in Canada over the 17-year period since 2000.Methods: Isolates were collected from across Canada between August 2000 and July 2017 and identified to the species and, for isolates between 2015 and 2017, strain level.Results: We analyzed 1,362 Burkholderia isolates from at least 396 people with CF. Forty-nine percent (n = 666) of all isolates and 47% (n = 179) of new incident infections were identified as B. multivorans. The incidence of Burkholderia infection in the Canadian CF population did not change between 2000 and 2017 at 6 cases per 1,000 annually. Multilocus sequence typing analysis suggested minimal sharing of clones in Canada.Conclusions: The epidemiology of Burkholderia in CF in Canada has shifted from limited numbers of epidemic strains of B. cenocepacia to largely nonclonal isolates of B. multivorans, B. cenocepacia, and other species. Despite widespread infection control, however, Burkholderia species bacteria continue to be acquired by people with CF at an unchanged rate, posing a continued hazard.

Draft Genome Sequence of a Burkholderia cepacia Complex Strain Isolated from a Human Intra-abdominal Abscess

Burkholderia cepacia complex (Bcc) bacteria are opportunistic pathogens with high transmissibility and mortality. Here, we report the draft genome sequence of a Bcc strain isolated from a deep abscess culture in an immunocompetent patient with no relevant prior medical history.

Burkholderia cepacia complex (Bcc) bacteria are opportunistic pathogens with high transmissibility and mortality. Here, we report the draft genome sequence of a Bcc strain isolated from a deep abscess culture in an immunocompetent patient with no relevant prior medical history.

Genomics of an endemic cystic fibrosis Burkholderia multivorans strain reveals low within-patient evolution but high between-patient diversity

Burkholderia multivorans is a member of the Burkholderia cepacia complex (Bcc), notorious for its pathogenicity in persons with cystic fibrosis. Epidemiological surveillance suggests that patients predominantly acquire B. multivorans from environmental sources, with rare cases of patient-to-patient transmission. Here we report on the genomic analysis of thirteen isolates from an endemic B. multivorans strain infecting four cystic fibrosis patients treated in different pediatric cystic fibrosis centers in Belgium, with no evidence of cross-infection. All isolates share an identical sequence type (ST-742) but whole genome analysis shows that they exhibit peculiar patterns of genomic diversity between patients. By combining short and long reads sequencing technologies, we highlight key differences in terms of small nucleotide polymorphisms indicative of low rates of adaptive evolution within patient, and well-defined, hundred kbps-long segments of high enrichment in mutations between patients. In addition, we observed large structural genomic variations amongst the isolates which revealed different plasmid contents, active roles for transposase IS3 and IS5 in the deactivation of genes, and mobile prophage elements. Our study shows limited within-patient B. multivorans evolution and high between-patient strain diversity, indicating that an environmental microdiverse reservoir must be present for this endemic strain, in which active diversification is taking place. Furthermore, our analysis also reveals a set of 30 parallel adaptations across multiple patients, indicating that the specific genomic background of a given strain may dictate the route of adaptation within the cystic fibrosis lung.

Response of high-, mid- and low-abundant taxa and potential pathogens to eight disinfection methods and their interactions in domestic hot water system

Eight disinfection methods were applied to control biofilm contamination in domestic hot water system. The inactivation efficiency, responses of high- (≥1%), mid- (0.1% ~ 1%) and low-abundant taxa (≤0.1%) to disinfection, and interactions within and across three sub-communities were investigated. Ultraviolet was the most effective disinfection method for total bacteria and Escherichia coli, and chlorine dioxide had the highest inactivation efficiency on heterotrophic bacteria, while silver ions exhibited poor performance on all of them. At the phylum level, the responses of microorganisms to eight disinfection methods were different, but Proteobacteria and Firmicutes dominated in most samples. Eight disinfection methods had a greater impact on the proportion of high- and mid-abundant taxa than that of low-abundant taxa, and led to dissimilar transformations of genera among high-, mid- and low-abundant taxa in each sample. High-, mid- and low-abundant taxa of different samples showed similar structures and were roughly clustered into three Groups. Moreover, high-abundant taxa had more complex internal interactions than mid- and low-abundant taxa, and mainly presented co-occurrence patterns. The associations between high- and low-abundant taxa were close, and some low-abundant genera were identified as hub bacteria, such as Paracoccus, Thioalkalispira and Flavitalea. Furthermore, a total of 23 potential pathogens were detected in this study, and they mainly showed positive interactions, with Mycobacteria and Streptococcus as keystone genera. These results highlight the dissimilar responses of high-, mid- and low-abundant taxa to disinfection, and the critical role of some low-abundant genera in the microbial network, as well as the co-occurrence patterns among potential pathogens.

Comparative Study of Urinary Minerals and Their Effect on Stone Formation in Two Groups of Cystic Fibrosis (CF) and Healthy Children

Background: Cystic Fibrosis (CF) is a systemic autosomal disorder and the most important chronic lung disease in children. Oxalate is the end product of vitamin C metabolism, which increases the risk of kidney stones, urinary bladder stones, and calcium deposits in CF patients. Objectives: Considering the increased mineral excretion and the rate of stone formation in the urinary tract, examining the excretion of minerals will greatly help resolve clinical problems. Methods: This descriptive-analytical study was performed on CF and healthy children in Gorgan in 2018 - 19. In this study, 40 CF children and 40 healthy children were randomly selected. After obtaining informed consent from the parents of the children, a random urine sample was collected to evaluate urine minerals. Children with abnormal urinary mineral excretion underwent ultrasonography. The data were analyzed by SPSS 18 using descriptive indices (mean ± SD, frequency, and percentage) and statistical tests (independent t-test, chi-square test, and nonparametric tests). Results: Out of 80 CF and healthy children, 34 were girls, and the rest was boys. The mean age of the patients was 4.34 ± 3.38. The age difference was not significant between the groups (P > 0.05). The mean urinary levels of phosphorus, uric acid, magnesium, and citrate were 0.87 ± 1.01, 1.16 ± 0.68, 0.23 ± 0.18, 2.37 ± 3.13 mg/mg of creatinine. In the pediatric patient group, respectively (P < 0.001). The mean urinary calcium level in CF patients was 0.28 ± 0.39, which was lower than that in the healthy group. The mean urinary oxalate level was 0.13 ± 0.20 in CF patients, which was higher than that in the healthy group (P > 0.05). Hyperoxaluria, hyperuricosuria, hypomagnesiuria, and hypocitraturia occurred in 35, 30, 62, and 7.5% of the CF patients, respectively. Among the urinary minerals studied, hyperoxaluria was found to be a major determinant of stone formation risk in CF. No correlation was observed between the formation of stones and the rate of excretion of minerals (P > 0.05). Conclusions: In summary, CF patients are at an increased risk of developing citrate and calcium stones compared to the healthy group, which is associated with hyperuricosuria, hypocitraturia, and hyperoxaluria.

Investigation of Burkholderia cepacia complex bacteremia outbreak in a neonatal intensive care unit: a case series

INTRODUCTION

Burkholderia cepacia complex is a ubiquitous organism with a high virulence potential. It is found most commonly in moist environments. Hospital outbreaks have been reported from diverse sources such as contaminated faucets, nebulizers, disinfectant solutions, multidose antibiotic vials, tap water, bottled water, nasal sprays, and ultrasound gels. In this article, we present our experience in investigating and successfully managing an outbreak of nosocomial transmission of Burkholderia cepacia sepsis in the neonatal intensive care unit at SGT Hospital, Haryana, India.

CASE PRESENTATION

During the month of March, multiple Burkholderia cepacia complex isolates were recovered from blood cultures of Caucasian babies admitted to the neonatal intensive care unit of our hospital. The organisms were multidrug-resistant, with in vitro sensitivity to meropenem alone (minimum inhibitory concentration = 4 μg/ml). An outbreak was suspected, and the neonatal intensive care unit in-charge and hospital infection control teams were alerted. Outbreak investigation was initiated, and surveillance samples were collected. Burkholderia cepacia complex was successfully isolated from suction apparatus. The isolates were phenotypically typed (biotyping and antimicrobial susceptibility testing) and found to be identical.

CONCLUSIONS

In our study, the index case might have been exposed to infection due to a physiological state of low immunity (preterm, low birth weight, and mechanical ventilation). The rest of the cases might have been exposed to this organism due to inadequate hand hygiene/improper cleaning and disinfection practices. Timely reporting and implementation of infection control measures played a significant role in curtailing this outbreak.

Response of bacterial regrowth, abundant and rare bacteria and potential pathogens to secondary chlorination in secondary water supply system

This study investigated the effects of secondary chlorination on bacterial regrowth, microbial communities (abundant and rare taxa) and bacterial functions of pipe wall biofilm and bulk water in simulated secondary water supply system (SWSS). Continuous secondary chlorination was more effective than short-term secondary chlorination to control the bacterial regrowth in both biofilm and water samples. Bacterial diversity slightly reduced after continuous secondary chlorination, and 19.27% of the total operational taxonomic units (OTUs) were shared by biofilm and water samples, with Bacillus as the dominant genus. Abundant and rare taxa exhibited different community structures. Proteobacteria and candidate division WPS-1 predominated in abundant and rare phyla were sensitive to chlorine, while Firmicutes, Acidobacteria and Bacteroidetes, exhibited relative strong chlorine resistance. The abundant genera in control sample (e.g., Bosea, Sphingobium and Gemmata) exhibited poor tolerance to chlorine, while Bacillus in biofilm and Defluviimonas in water were the main chlorine-resistant genera. Moreover, the composition of rare genera in each sample was obviously different. Furthermore, a total of 18 potential pathogens were detected with Pseudomonas as the dominant genus, most of which were significantly reduced after disinfection. There were mainly positive interactions among potential pathogenic bacteria, with Enterococcus, Legionella and Vibrio as the hub genera as revealed by network analysis. Similar bacterial functions in both biofilm and water were observed with metabolism as the predominant bacterial function, while, human disease function only accounted for 1.07% of bacterial functions. These results highlighted the importance of continuous secondary chlorination for controlling biosafety of SWSS and identified the dissimilar responses of abundant and rare bacteria to the disinfection, as well as the co-occurrence patterns among potential pathogens, improving our understanding of bacterial communities in SWSS.

Microbiology of Cystic Fibrosis Airway Disease

Although survival of individuals with cystic fibrosis (CF) has been continuously improving for the past 40 years, respiratory failure secondary to recurrent pulmonary infections remains the leading cause of mortality in this patient population. Certain pathogens such as Pseudomonas aeruginosa, methicillin-resistant Staphylococcus aureus, and species of the Burkholderia cepacia complex continue to be associated with poorer clinical outcomes including accelerated lung function decline and increased mortality. In addition, other organisms such as anaerobes, viruses, and fungi are increasingly recognized as potential contributors to disease progression. Culture-independent molecular methods are also being used for diagnostic purposes and to examine the interaction of microorganisms in the CF airway. Given the importance of CF airway infections, ongoing initiatives to promote understanding of the epidemiology, clinical course, and treatment options for these infections are needed.

In Vitro Activity of Minocycline against U.S. Isolates of Acinetobacter baumannii-Acinetobacter calcoaceticus Species Complex, Stenotrophomonas maltophilia, and Burkholderia cepacia Complex: Results from the SENTRY Antimicrobial Surveillance Program, 2014 to 2018

We evaluated the activity of minocycline and comparator agents against a large number of Stenotrophomonas maltophilia (n = 1,289), Acinetobacter baumannii-Acinetobacter calcoaceticus species complex (n = 1,081), and Burkholderia cepacia complex (n = 101) isolates collected from 2014 to 2018 from 87 U.S. medical centers spanning all 9 census divisions. The isolates were collected primarily from hospitalized patients with pneumonia (1,632 isolates; 66.0% overall), skin and skin structure infections (354 isolates; 14.3% overall), bloodstream infections (266 isolates; 10.8% overall), urinary tract infections (126 isolates; 5.1% overall), intra-abdominal infections (61 isolates; 2.5% overall), and other infections (32 isolates; 1.3% overall). Against the A. baumannii-A. calcoaceticus species complex, colistin was the most active agent, exhibiting MIC_50/90 values at ≤0.5/2 μg/ml and 92.4% susceptibility. Minocycline ranked second in activity, with MIC_50/90 values at 0.25/8 μg/ml and susceptibility at 85.7%. Activity for these two agents was reduced against extensively drug-resistant and multidrug-resistant isolates of the Acinetobacter baumannii-Acinetobacter calcoaceticus species complex. Only two agents showed high levels of activity (susceptibility, >90%) against S. maltophilia, minocycline (MIC_50/90, 0.5/2 μg/ml; 99.5% susceptible) and trimethoprim-sulfamethoxazole (MIC_50/90, ≤0.5/1 μg/ml; 94.6% susceptible). Minocycline was active against 92.8% (MIC₉₀, 4 μg/ml) of trimethoprim-sulfamethoxazole-resistant S. maltophilia isolates. Various agents exhibited susceptibility rates of nearly 90% against the B. cepacia complex isolates; these were trimethoprim-sulfamethoxazole (MIC_50/90, ≤0.5/2 μg/ml; 93.1% susceptible), ceftazidime (MIC_50/90, 2/8 μg/ml; 91.0% susceptible), meropenem (MIC_50/90, 2/8 μg/ml; 89.1% susceptible), and minocycline (MIC_50/90, 2/8 μg/ml; 88.1% susceptible). These results indicate that minocycline is among the most active agents for these three problematic potential pathogen groups when tested against U.S. isolates.

Isolation and identification of Pandoraea spp. From bronchoalveolar lavage of cystic fibrosis patients in Iran

Background

Pandoraea species are gram negative, motile, non-spore forming, rod shaped and oxidase positive, obligate aerobes bacteria, and have one polar flagellum. Most of Pandoraea species are associated with lung infections in cystic fibrosis patients. Cystic fibrosis is the most prevalent autosomal recessive hereditary disease in the world that affects various organs of the body. The main important cause of death in these patients is lung involvement. This study was conducted to isolate and identify Pandoraea bacterium from bronchoalveolar lavage and sputum samples of cystic fibrosis patients in Shiraz, Iran.

Methods

In this research 31 samples of bronchoalveolar lavage and sputum were examined by culture and PCR method. Then confirmed isolates were evaluated for susceptibility to different antibiotics and ability to produce biofilm.

Results

The results of this study after cultivation, purification and DNA extraction led to the isolation of 4 Pandoraea bacterium by PCR using specific primers. Antibiotic susceptibility test were indicated all isolates were resistant to gentamicin, amikacin and imipenem and susceptible to ciprofloxacin, trimethoprim-sulfumethoxazole, piperacillin and tetracycline. Ability to create biofilm was indicated by some of Pandoraea isolates. According to findings of this study, ability to synthesis biofilm by Pandoraea isolates and resistance to some antibiotics are very important.

Conclusions

Our study notes the role of P. pnomenusa as an emerging pathogen that can cause chronic lung colonization in CF patients. Identification tools need to be accurate and must be based on molecular techniques. Also our findings should raise awareness about antibiotic resistance in cystic fibrosis patients in Iran and ability of including bacterial agents to produce biofilm is an alarm for public health. Thus clinicians should exercise caution about finding of clinical relevance of this pathogen to the infection and prescribing antibiotics, especially in cases of children infections.

Work environment risks for health care workers with cystic fibrosis

In Australia and New Zealand, >50% of people with cystic fibrosis (CF) are adults and many of these people are pursuing vocational training and undertaking paid employment. More than 6% of adults with CF are working in health care. There is limited guidance in literature to support health care workers with CF (HCWcf) in training and in employment to support safe practice and to provide protection for themselves and their patients from the acquisition of health care associated infection. A multidisciplinary team of CF and Infectious Disease Clinicians, Infection Prevention and Control Practitioners, HCWcf, academic experts in medical ethics and representatives from universities, appraised the available evidence on the risk posed to and by HCWcf. Specific recommendations were made for HCWcf, CF health care teams, hospitals and universities to support the safe practice and appropriate support for HCWcf.

Electrochemically Synthesized Silver Nanoparticles Are Active Against Planktonic and Biofilm Cells of Pseudomonas aeruginosa and Other Cystic Fibrosis-Associated Bacterial Pathogens

A novel, electrochemically synthesized, silver nanoparticles (AgNPs) formulation was evaluated in vitro against Pseudomonas aeruginosa, Burkholderia cepacia, Stenotrophomonas maltophilia, and Staphylococcus aureus strains from cystic fibrosis (CF) patients. AgNPs were particularly active against P. aeruginosa and B. cepacia planktonic cells (median MIC: 1.06 and 2.12 μg/ml, respectively) by a rapid, bactericidal and concentration-dependent effect. AgNPs showed to be particularly effective against P. aeruginosa and S. aureus biofilm causing a viability reduction ranging from 50% (1×MIC) to >99.9% (4×MIC). Electron microscopy showed that AgNPs deconstruct extracellular matrix of P. aeruginosa biofilm, and accumulate at the cell surface causing cell death secondary to membrane damage. Compared to Tobramycin, AgNPs showed comparable, or even better, activity against planktonic and biofilm P. aeruginosa cells. AgNPs at concentrations effective against B. cepacia and P. aeruginosa were not toxic to G. mellonella larvae. Our silver-based formulation might be an alternative to antibiotics in CF patients. Further in vitro and in vivo studies are warranted to confirm this therapeutic potential.

Novel Guanidine Compound against Multidrug-Resistant Cystic Fibrosis-Associated Bacterial Species

Chronic pulmonary infection is a hallmark of lung disease in cystic fibrosis (CF). Infections dominated by non-fermentative Gram-negative bacilli are particularly difficult to treat and highlight an urgent need for the development of new class of agents to combat these infections. In this work, a small library comprising thiourea and guanidine derivatives with low molecular weight was designed; these derivatives were studied as antimicrobial agents against Gram-positive, Gram-negative, and a panel of drug-resistant clinical isolates recovered from patients with CF. One novel compound, a guanidine derivative bearing adamantane-1-carbonyl and 2-bromo-4,6-difluouro-phenyl substituents (H-BDF), showed potent bactericidal activity against the strains tested, at levels generally higher than those exhibited by tobramycin, ceftazimide and meropenem. The role that different substituents exert in the antimicrobial activity has been determined, highlighting the importance of the halo-phenyl group in the guanidine moiety. The new compound displays low levels of cytotoxicity against THP-1 and A549 cells with a selective index (SI) > 8 (patent application PCT/IB2017/054870, August 2017). Taken together, our results indicate that H-BDF can be considered as a promising antimicrobial agent.

Crystal structure of chorismate mutase from Burkholderia thailandensis

Burkholderia thailandensis is often used as a model for more virulent members of this genus of proteobacteria that are highly antibiotic-resistant and are potential agents of biological warfare that are infective by inhalation. As part of ongoing efforts to identify potential targets for the development of rational therapeutics, the structures of enzymes that are absent in humans, including that of chorismate mutase from B. thailandensis, have been determined by the Seattle Structural Genomics Center for Infectious Disease. The high-resolution structure of chorismate mutase from B. thailandensis was determined in the monoclinic space group P21 with three homodimers per asymmetric unit. The overall structure of each protomer has the prototypical AroQγ topology and shares conserved binding-cavity residues with other chorismate mutases, including those with which it has no appreciable sequence identity.

[The controversial Burkholderia cepacia complex, a group of plant growth promoting species and plant, animals and human pathogens]

The Burkholderia cepacia complex is a group of 22 species, which are known as opportunistic pathogens in immunocompromised people, especially those suffering from cystic fibrosis. It is also found in nosocomial infections and is difficult to eradicate due to intrinsic resistance to several antibiotics. The species have large genomes (up to 9 Mbp), distributed into 2-5 replicons. These features significantly contribute to genome plasticity, which makes them thrive in different environments like soil, water, plants or even producing nodules in legume plants. Some B. cepacia complex species are beneficial in bioremediation, biocontrol and plant-growth promotion. However, because the B. cepacia complex is involved in human infection, its use in agriculture is restricted. B. cepacia complex is being constantly studied due to the health problems that it causes and because of its agricultural potential. In this review, the history of B. cepacia complex and the most recently published information related to this complex are revised.

Comparative Genomics of Environmental and Clinical Burkholderia cenocepacia Strains Closely Related to the Highly Transmissible Epidemic ET12 Lineage

The Burkholderia cenocepacia epidemic ET12 lineage belongs to the genomovar IIIA including the reference strain J2315, a highly transmissible epidemic B. cenocepacia lineage. Members of this lineage are able to cause lung infections in immunocompromised and cystic fibrosis patients. In this study, we describe the genome of F01, an environmental B. cenocepacia strain isolated from soil in Burkina Faso that is, to our knowledge, the most closely related strain to this epidemic lineage. A comparative genomic analysis was performed on this new isolate, in association with five clinical and one environmental B. cenocepacia strains whose genomes were previously sequenced. Antibiotic resistances, virulence phenotype, and genomic contents were compared and discussed with an emphasis on virulent and antibiotic determinants. Surprisingly, no significant differences in antibiotic resistance and virulence were found between clinical and environmental strains, while the most important genomic differences were related to the number of prophages identified in their genomes. The ET12 lineage strains showed a noticeable greater number of prophages (partial or full-length), especially compared to the phylogenetically related environmental F01 strain (i.e., 5–6 and 3 prophages, respectively). Data obtained suggest possible involvements of prophages in the clinical success of opportunistic pathogens.

What matters in chronic Burkholderia cenocepacia infection in cystic fibrosis: Insights from comparative genomics

Burkholderia cenocepacia causes severe pulmonary infections in cystic fibrosis (CF) patients. Since the bacterium is virtually untreatable by antibiotics, chronic infections persist for years and might develop into fatal septic pneumonia (cepacia syndrome, CS). To devise new strategies to combat chronic B. cenocepacia infections, it is essential to obtain comprehensive knowledge about their pathogenesis. We conducted a comparative genomic analysis of 32 Czech isolates of epidemic clone B. cenocepacia ST32 isolated from various stages of chronic infection in 8 CF patients. High numbers of large-scale deletions were found to occur during chronic infection, affecting preferentially genomic islands and nonessential replicons. Recombination between insertion sequences (IS) was inferred as the mechanism behind deletion formation; the most numerous IS group was specific for the ST32 clone and has undergone transposition burst since its divergence. Genes functionally related to transition metal metabolism were identified as hotspots for deletions and IS insertions. This functional category was also represented among genes where nonsynonymous point mutations and indels occurred parallelly among patients. Another category exhibiting parallel mutations was oxidative stress protection; mutations in catalase KatG resulted in impaired detoxification of hydrogen peroxide. Deep sequencing revealed substantial polymorphism in genes of both categories within the sputum B. cenocepacia ST32 populations, indicating extensive adaptive evolution. Neither oxidative stress response nor transition metal metabolism genes were previously reported to undergo parallel evolution during chronic CF infection. Mutations in katG and copper metabolism genes were overrepresented in patients where chronic infection developed into CS. Among professional phagocytes, macrophages use both hydrogen peroxide and copper for their bactericidal activity; our results thus tentatively point to macrophages as suspects in pathogenesis towards the fatal CS.

The large Burkholderia cenocepacia populations which persist in cystic fibrosis lungs during many years of chronic infections have an inherent potential for adaptive evolution. The results provided by comparative genomics are key in understanding the processes involved. Mutational events which have taken place allow us to deductively reconstruct the history of chronic infection and to identify driving forces acting upon the bacteria. Beyond the conventional point mutation analysis of next generation sequencing data, we observed interesting phenomena such as large deletions and transposable element movement which represent another facet of adaptive evolution of B. cenocepacia during chronic infection. We also found, unexpectedly, that adaptive evolution in B. cenocepacia strain ST32 affects a set of genes conspicuously different from related species B. dolosa; these appear to be linked to host immune response. Our study provides clues to the complex puzzle of chronic B. cenocepacia infection establishment, persistence and outcome in cystic fibrosis.

Novel antibiotic combinations proposed for treatment of Burkholderia cepacia complex infections

Effective strategies to manage Burkholderia cepacia complex (Bcc) infections in cystic fibrosis (CF) patients are lacking. We tested combinations of clinically available antibiotics and show that moxifloxacin-ceftazidime could inhibit 16 Bcc clinical isolates at physiologically achievable concentrations. Adding low dose of colistin improved the efficacy of the combo, especially at conditions mimicking CF respiratory secretions.

Outbreak of Burkholderia cepacia pseudobacteraemia caused by intrinsically contaminated commercial 0.5% chlorhexidine solution in neonatal intensive care units

BACKGROUND

Burkholderia cepacia is intrinsically resistant to certain antiseptics. The authors noted a sudden increase in the frequency of isolation of B. cepacia from blood cultures in a neonatal intensive care unit (NICU) of a university-affiliated hospital.

AIM

To identify the source and intervene in the ongoing infections.

METHODS

The cases were defined as patients with positive blood cultures for B. cepacia in an NICU between November 2014 and January 2015. Medical records were reviewed and NICU healthcare workers were interviewed. Samples of suspected antiseptics, blood culture bottles, cotton balls, gauze and a needle used in the NICU were analysed microbiologically.

FINDINGS

During the outbreak period, B. cepacia was identified in 25 blood cultures obtained from 21 patients. The clinical features of the patients were suggestive of pseudobacteraemia. Regarding environmental samples, B. cepacia was cultured from 0.5% chlorhexidine gluconate (CHG) solution products that had been used as a skin antiseptic during blood drawing in the NICU. The clinical B. cepacia isolate and two strains obtained from 0.5% CHG exhibited identical pulsed-field gel electrophoresis patterns. After the CHG products were withdrawn, the outbreak was resolved.

CONCLUSIONS

The pseudobacteraemia cases were caused by contaminated 0.5% CHG produced by a single manufacturer. Stricter government regulation is needed to prevent contamination of disinfectants during manufacturing. In addition, microbial contamination of antiseptics and disinfectants should be suspected when a B. cepacia outbreak occurs in hospitalized patients.

Virulence traits associated with Burkholderia cenocepacia ST856 epidemic strain isolated from cystic fibrosis patients

BACKGROUND

Burkholderia cenocepacia is considered one of the most problematic cystic fibrosis (CF) pathogens. Colonization prevalence in the Serbian CF population is high and virtually exclusively limited to a single highly transmissible clone of B. cenocepacia ST856 which is positive for both the B. cepacia epidemic strain marker (BCESM) and cable pilin, and is closely related to the epidemic strain CZ1 (ST32).

METHODS

Biofilm formation for 182 isolates, and adhesion to components of the host extracellular matrix, proteolytic activity, mucoidy and motility of selected ST856 representatives, as well as B. cenocepacia ST858 and ST859, and B. stabilis ST857, novel STs isolated from Serbian CF patients, were investigated in this study. The presence of the cepI, cepR, fliG, llpE, wbiI, and bcscV genes was analyzed.

RESULTS

Biofilm-formation ability of analyzed strains was poor under standard laboratory conditions, but changed in stress conditions (cold stress) and conditions that mimic CF milieu (increased CO₂). All strains expressed ability to bind to collagen and fibronectin albeit with different intensity. Representatives of ST856 exhibited gelatinase activity. ST858, ST859 and 9/11 of ST856 genotypes were positive for swimming and twitching motility whereas ST857 was non-motile. Mucoidy was demonstrated in all ST856 genotypes, ST857 was semi-mucoid, and ST858 and ST859 were non-mucoid. Molecular analysis for major virulence factors revealed that ST856 and ST857 carried the six analyzed genes, while ST858 and ST859 were negative for the llpE gene.

CONCLUSION

Variations in virulence phenotypes in different genotypes of epidemic B. cenocepacia ST856 clone, in vitro, could be a consequence of diversification driven by pathoadaptation. Diversity of epidemic clone genotypes virulence, could be challenging for accurate diagnosis and treatment, as well as for infection control.

Phenotypic diversity and genotypic flexibility of Burkholderia cenocepacia during long-term chronic infection of cystic fibrosis lungs

Chronic bacterial infections of the lung are the leading cause of morbidity and mortality in cystic fibrosis patients. Tracking bacterial evolution during chronic infections can provide insights into how host selection pressures—including immune responses and therapeutic interventions—shape bacterial genomes. We carried out genomic and phenotypic analyses of 215 serially collected Burkholderia cenocepacia isolates from 16 cystic fibrosis patients, spanning a period of 2–20 yr and a broad range of epidemic lineages. Systematic phenotypic tests identified longitudinal bacterial series that manifested progressive changes in liquid media growth, motility, biofilm formation, and acute insect virulence, but not in mucoidy. The results suggest that distinct lineages follow distinct evolutionary trajectories during lung infection. Pan-genome analysis identified 10,110 homologous gene clusters present only in a subset of strains, including genes restricted to different molecular types. Our phylogenetic analysis based on 2148 orthologous gene clusters from all isolates is consistent with patient-specific clades. This suggests that initial colonization of patients was likely by individual strains, followed by subsequent diversification. Evidence of clonal lineages shared by some patients was observed, suggesting inter-patient transmission. We observed recurrent gene losses in multiple independent longitudinal series, including complete loss of Chromosome III and deletions on other chromosomes. Recurrently observed loss-of-function mutations were associated with decreases in motility and biofilm formation. Together, our study provides the first comprehensive genome-phenome analyses of B. cenocepacia infection in cystic fibrosis lungs and serves as a valuable resource for understanding the genomic and phenotypic underpinnings of bacterial evolution.

An efficient system for the generation of marked genetic mutants in members of the genus Burkholderia

To elucidate the function of a gene in bacteria it is vital that targeted gene inactivation (allelic replacement) can be achieved. Allelic replacement is often carried out by disruption of the gene of interest by insertion of an antibiotic-resistance marker followed by subsequent transfer of the mutant allele to the genome of the host organism in place of the wild-type gene. However, due to their intrinsic resistance to many antibiotics only selected antibiotic-resistance markers can be used in members of the genus Burkholderia, including the Burkholderia cepacia complex (Bcc). Here we describe the construction of improved antibiotic-resistance cassettes that specify resistance to kanamycin, chloramphenicol or trimethoprim effectively in the Bcc and related species. These were then used in combination with and/or to construct a series enhanced suicide vectors, pSHAFT2, pSHAFT3 and pSHAFT-GFP to facilitate effective allelic replacement in the Bcc. Validation of these improved suicide vectors was demonstrated by the genetic inactivation of selected genes in the Bcc species Burkholderia cenocepacia and B. lata, and in the non-Bcc species, B. thailandensis.

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We have constructed antibiotic-resistance cassettes and suicide vectors for use in Burkholderia and related species.

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These vectors facilitate construction of mutants by gene disruption with antibiotic-resistance markers.

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We have validated the utility of the vectors for marked genetic inactivation in members of the genus Burkholderia.

Taxonomy and pathogenesis of the Burkholderia cepacia complex

Patients with cystic fibrosis (CF) are susceptible to chronic respiratory infection with a number of bacterial pathogens. The Burkholderia cepacia complex bacteria are problematic CF pathogens because (i) they are very resistant to antibiotics, making respiratory infection difficult to treat and eradicate; (ii) infection with these bacteria is associated with high mortality in CF; (iii) they may spread from one CF patient to another, leading to considerable problems for both patients and carers; and (iv) B. cepacia complex bacteria are difficult to identify and nine new species have now been found to constitute isolates originally identified as ‘B. cepacia’ based on their phenotypic properties. Here we review the changes that have occurred in the taxonomy of the B. cepacia complex and the pathogenic factors these bacteria possess. While the taxonomy of the B.cepacia complex has advanced considerably with the development of accurate methods for their identification, the pathogenic mechanisms employed by these CF pathogens are only just beginning to be explored at the molecular level. Several virulence factors have been defined for B. cenocepacia (the dominant CF pathogen within the complex); however, knowledge of the disease mechanisms employed by other B. cepacia complex species is limited. The recent determination of the complete genome sequences for several of the B. cepacia complex species should greatly enhance our ability to study these problematic CF pathogens.

Isolation of Infectious Cystic Fibrosis Patients: Results of a Systematic Review

Objective:

Respiratory tract infections significantly contribute to morbidity and mortality among cystic fibrosis (CF) patients. Therefore, pathogen transmission needs to be prevented. There are several guidelines for the care of CF patients, but no transparent systematic literature review has been published.

Methods:

We conducted a systematic literature review (January 1966 to September 2004) dealing with segregation of CF patients colonized withBurkholderia cepaciaspecies,Pandoraeaspecies,Pseudomonas aeruginosa, Stenotrophomonas maltophilia,orAlcaligenesspecies. Quality of studies was evaluated by taking patient population size, existence of control-patients, patient randomization, diagnostic approach, and bacteria typing methods into account.

Results:

One hundred ninety-nine studies were found. Evidence and quality of 102 publications were evaluated. In 99 publications, recommendations concerning segregation measures for infectious CF patients were determined including a total of 11,576 patients. No randomized, controlled trials had been conducted. Fifty of 56 authors strongly recommended isolation of CF patients infected withB. cepaciaorPandoraeaspecies. In 31 of 39 studies, interpatient spread ofPseudomonas aeruginosawas documented or had been brought to an end by isolation of patients. Only five studies had addressed S.maltophiliaorAlcaligenesspecies.

Conclusions:

Patients colonized withB. cepaciaorPandoraeaspecies are to be separated from noncolonized patients in single rooms. Patients harboring multidrug-resistantPseudomonas aeruginosa, S. maltophilia,orAlcaligenesspecies may not share a room with immunocompromised patients, in intensive care units, or with other CF patients anywhere in the hospital.

Infection Prevention and Control Guideline for Cystic Fibrosis: 2013 Update

The 2013 Infection Prevention and Control (IP&C) Guideline for Cystic Fibrosis (CF) was commissioned by the CF Foundation as an update of the 2003 Infection Control Guideline for CF. During the past decade, new knowledge and new challenges provided the following rationale to develop updated IP&C strategies for this unique population:

1.The need to integrate relevant recommendations from evidence-based guidelines published since 2003 into IP&C practices for CF. These included guidelines from the Centers for Disease Control and Prevention (CDC)/Healthcare Infection Control Practices Advisory Committee (HICPAC), the World Health Organization (WHO), and key professional societies, including the Infectious Diseases Society of America (IDSA) and the Society for Healthcare Epidemiology of America (SHEA). During the past decade, new evidence has led to a renewed emphasis on source containment of potential pathogens and the role played by the contaminated healthcare environment in the transmission of infectious agents. Furthermore, an increased understanding of the importance of the application of implementation science, monitoring adherence, and feedback principles has been shown to increase the effectiveness of IP&C guideline recommendations.

2.Experience with emerging pathogens in the non-CF population has expanded our understanding of droplet transmission of respiratory pathogens and can inform IP&C strategies for CF. These pathogens include severe acute respiratory syndrome coronavirus and the 2009 influenza A H1N1. Lessons learned about preventing transmission of methicillin-resistantStaphylococcus aureus(MRSA) and multidrug-resistant gram-negative pathogens in non-CF patient populations also can inform IP&C strategies for CF.

[Cystic Fibrosis Cloud database: An information system for storage and management of clinical and microbiological data of cystic fibrosis patients]

The epidemiological and clinical management of cystic fibrosis (CF) patients suffering from acute pulmonary exacerbations or chronic lung infections demands continuous updating of medical and microbiological processes associated with the constant evolution of pathogens during host colonization. In order to monitor the dynamics of these processes, it is essential to have expert systems capable of storing and subsequently extracting the information generated from different studies of the patients and microorganisms isolated from them. In this work we have designed and developed an on-line database based on an information system that allows to store, manage and visualize data from clinical studies and microbiological analysis of bacteria obtained from the respiratory tract of patients suffering from cystic fibrosis. The information system, named Cystic Fibrosis Cloud database is available on the http://servoy.infocomsa.com/cfc_database site and is composed of a main database and a web-based interface, which uses Servoy's product architecture based on Java technology. Although the CFC database system can be implemented as a local program for private use in CF centers, it can also be used, updated and shared by different users who can access the stored information in a systematic, practical and safe manner. The implementation of the CFC database could have a significant impact on the monitoring of respiratory infections, the prevention of exacerbations, the detection of emerging organisms, and the adequacy of control strategies for lung infections in CF patients.

Burkholderia species infections in patients with cystic fibrosis in British Columbia, Canada. 30 years' experience

RATIONALE

We have been collecting Burkholderia species bacteria from patients with cystic fibrosis (CF) for the last 30 years. During this time, our understanding of their multispecies taxonomy and infection control has evolved substantially.

OBJECTIVES

To evaluate the long-term (30 year) epidemiology and clinical outcome of Burkholderia infection in CF, and fully define the risks associated with infection by each species.

METHODS

Isolates from Burkholderia-positive patients (n=107) were speciated and typed annually for each infected patient. Microbiological and clinical data were evaluated by thorough review of patient charts, and statistical analyses performed to define significant epidemiological factors.

MEASUREMENTS AND MAIN RESULTS

Before 1995, the majority of new Burkholderia infections were caused by epidemic clones of Burkholderia cenocepacia. After implementation of new infection control measures in 1995, Burkholderia multivorans became the most prevalent species. Survival analysis showed that patients with CF infected with B. cenocepacia had a significantly worse outcome than those with B. multivorans, and a novel finding was that, after Burkholderia infection, the prognosis for females was significantly worse than for males.

CONCLUSIONS

B. multivorans and B. cenocepacia have been the predominant Burkholderia species infecting people with CF in Vancouver. The implementation of infection control measures were successful in preventing new acquisition of epidemic strains of B. cenocepacia, leaving nonclonal B. multivorans as the most prevalent species. Historically, survival after infection with B. cenocepacia has been significantly worse than B. multivorans infection, and, of new significance, we show that females tend toward worse clinical outcomes.

Mechanisms of Disease: Host-Pathogen Interactions between Burkholderia Species and Lung Epithelial Cells

Members of the Burkholderia species can cause a range of severe, often fatal, respiratory diseases. A variety of in vitro models of infection have been developed in an attempt to elucidate the mechanism by which Burkholderia spp. gain entry to and interact with the body. The majority of studies have tended to focus on the interaction of bacteria with phagocytic cells with a paucity of information available with regard to the lung epithelium. However, the lung epithelium is becoming more widely recognized as an important player in innate immunity and the early response to infections. Here we review the complex relationship between Burkholderia species and epithelial cells with an emphasis on the most pathogenic species, Burkholderia pseudomallei and Burkholderia mallei. The current gaps in knowledge in our understanding are highlighted along with the epithelial host-pathogen interactions that offer potential opportunities for therapeutic intervention.

Identification of synergists that potentiate the action of polymyxin B against Burkholderia cenocepacia

Burkholderia cenocepacia and other members of the Burkholderia cepacia complex (BCC) are highly multidrug-resistant bacteria that cause severe pulmonary infections in patients with cystic fibrosis. A screen of 2686 compounds derived from marine organisms identified molecules that could synergise with polymyxin B (PMB) to inhibit the growth of B. cenocepacia. At 1 μg/mL, five compounds synergised with PMB and inhibited the growth of B. cenocepacia by ≥70% compared with growth in PMB alone. Follow-up testing revealed that one compound from the screen, the aminocoumarin antibiotic novobiocin, synergised with PMB and colistin against tobramycin-resistant clinical isolates of B. cenocepacia and Burkholderia multivorans. In parallel, we show that novobiocin sensitivity is common among BCC species and that these bacteria are even more susceptible to an alternative aminocoumarin, clorobiocin, which also had an additive effect with PMB against B. cenocepacia. These studies support using aminocoumarin antibiotics to treat BCC infections and show that synergisers can be found to increase the efficacy of antimicrobial peptides and polymyxins against BCC bacteria.

Parallel evolution of small colony variants in Burkholderia cenocepacia biofilms

A common phenotype within bacterial biofilms is the small, "wrinkly" colony, which may associate with worse prognoses from biofilm-associated infections. The mechanisms that produce these variants in Burkholderia are undefined. Here we report the mutational and ecological causes of wrinkly (W) colonies that evolved during experimental biofilm evolution of Burkholderia cenocepacia. Mutations clustered in a homologous pathway to the Pseudomonas wsp operon but with a distinct terminal signaling mechanism, and their parallel evolution suggested that they inhabited an equivalent biofilm niche. We tested this hypothesis of niche complementarity by measuring effects of substituting different W variants in the same evolved biofilm community. Despite phenotypic differences among W mutants growing alone, fitness of reconstituted mixed biofilms did not differ significantly. In conclusion, the evolution of small-colony variants in Burkholderia biofilms appears to be driven by an ecological opportunity that generates strong selection for constitutive wsp mutants to inhabit a common niche.

Fosmidomycin decreases membrane hopanoids and potentiates the effects of colistin on Burkholderia multivorans clinical isolates

Burkholderia cepacia complex (Bcc) pulmonary infections in people living with cystic fibrosis (CF) are difficult to treat because of the extreme intrinsic resistance of most isolates to a broad range of antimicrobials. Fosmidomycin is an antibacterial and antiparasitic agent that disrupts the isoprenoid biosynthesis pathway, a precursor to hopanoid biosynthesis. Hopanoids are involved in membrane stability and contribute to polymyxin resistance in Bcc bacteria. Checkerboard MIC assays determined that although isolates of the Bcc species B. multivorans were highly resistant to treatment with fosmidomycin or colistin (polymyxin E), antimicrobial synergy was observed in certain isolates when the antimicrobials were used in combination. Treatment with fosmidomycin decreased the MIC of colistin for isolates as much as 64-fold to as low as 8 μg/ml, a concentration achievable with colistin inhalation therapy. A liquid chromatography-tandem mass spectrometry technique was developed for the accurate quantitative determination of underivatized hopanoids in total lipid extracts, and bacteriohopanetetrol cyclitol ether (BHT-CE) was found to be the dominant hopanoid made by B. multivorans. The amount of BHT-CE made was significantly reduced upon fosmidomycin treatment of the bacteria. Uptake assays with 1-N-phenylnaphthylamine were used to determine that dual treatment with fosmidomycin and colistin increases membrane permeability, while binding assays with boron-dipyrromethene-conjugated polymyxin B illustrated that the addition of fosmidomycin had no impact on polymyxin binding. This work indicates that pharmacological suppression of membrane hopanoids with fosmidomycin treatment can increase the susceptibility of certain clinical B. multivorans isolates to colistin, an agent currently in use to treat pulmonary infections in CF patients.

Putrescine reduces antibiotic-induced oxidative stress as a mechanism of modulation of antibiotic resistance in Burkholderia cenocepacia

Communication of antibiotic resistance among bacteria via small molecules is implicated in transient reduction of bacterial susceptibility to antibiotics, which could lead to therapeutic failures aggravating the problem of antibiotic resistance. Released putrescine from the extremely antibiotic-resistant bacterium Burkholderia cenocepacia protects less-resistant cells from different species against the antimicrobial peptide polymyxin B (PmB). Exposure of B. cenocepacia to sublethal concentrations of PmB and other bactericidal antibiotics induces reactive oxygen species (ROS) production and expression of the oxidative stress response regulator OxyR. We evaluated whether putrescine alleviates antibiotic-induced oxidative stress. The accumulation of intracellular ROS, such as superoxide ion and hydrogen peroxide, was assessed fluorometrically with dichlorofluorescein diacetate, while the expression of OxyR and putrescine synthesis enzymes was determined in luciferase assays using chromosomal promoter-lux reporter system fusions. We evaluated wild-type and isogenic deletion mutant strains with defects in putrescine biosynthesis after exposure to sublethal concentrations of PmB and other bactericidal antibiotics. Exogenous putrescine protected against oxidative stress induced by PmB and other antibiotics, whereas reduced putrescine synthesis resulted in increased ROS generation and a parallel increased sensitivity to PmB. Of the 3 B. cenocepacia putrescine-synthesizing enzymes, PmB induced only BCAL2641, an ornithine decarboxylase. This study reveals BCAL2641 as a critical component of the putrescine-mediated communication of antibiotic resistance and as a plausible target for designing inhibitors that would block the communication of such resistance among different bacteria, ultimately reducing the window of therapeutic failure in treating bacterial infections.

Genome Sequence of Burkholderia cenocepacia H111, a Cystic Fibrosis Airway Isolate

The Burkholderia cepacia complex (BCC) is a group of related bacterial species that are commonly isolated from environmental samples. Members of the BCC can cause respiratory infections in cystic fibrosis patients and immunocompromised individuals. We report here the genome sequence of Burkholderia cenocepacia H111, a well-studied model strain of the BCC.

Bacterial community of biofilms developed under different water supply conditions in a distribution system

In order to understand the bacterial community characteristics of biofilms developed under different finished water supply histories in drinking water distribution systems (DWDS), biofilm samples on different type of iron corrosion scales in a real DWDS were collected and systematically investigated using 454 pyrosequencing of 16S rRNA gene. The richness and diversity estimators showed that biofilms formed in DWDS transporting finished groundwater (GW) had the lowest level of bacterial diversity. From phylum to genus level, the dominant bacterial groups found in the biofilms under finished surface water (SW) and GW conditions were distinct. Proteobacteria was the dominant group in all biofilm samples (in the range of 40%-97%), but was relatively higher in biofilms with GW. The relative abundance of Firmicutes in biofilms with SW (28%-35%) was significantly higher (p<0.01) than that in biofilms with GW (0.5%-2.88%). Statistical analysis (Spearman's rank) revealed that alkalinity and chemical oxygen demand (CODMn) positively correlated with the relative abundance of Proteobacteria and Firmicutes, respectively. The abundance of sequences affiliated to iron-reducing bacteria (mainly Bacillus) and iron-oxidizing bacteria (mainly Acidovorax) were relatively higher in biofilms with SW, which might contribute to the formation of much thicker or tubercle-formed corrosion scales under SW supply condition. Several potential opportunistic pathogens, such as Burkholderia fungorum, Mycobacterium neoaurum, Mycobacterium frederiksbergense were detected in the biofilms.

Serum susceptibility in clinical isolates of Burkholderia cepacia complex bacteria: development of a growth-based assay for high throughput determination

Burkholderia cepacia complex (BCC) bacteria can cause devastating chronic infections in people with cystic fibrosis. Of particular concern is “cepacia syndrome,” a rapidly progressive and usually fatal decline in health, characterized by a necrotizing bacteremic pneumonia. An important component of defense against bloodstream infections is the bactericidal action of serum. Traditional methods to determine the capacity of bacterial isolates to resist the bactericidal effects of serum are relatively low-throughput viability assays. In this study, we developed a novel growth-based assay for serum susceptibility, which allows for high throughput analysis. We applied this assay to a range of clinical isolates of BCC as well as isolates comprising the BCC experimental strain panel. Our data demonstrate that isolates from all species of BCC examined can possess serum resistant or serum sensitive/intermediate phenotypes. Of particular clinical significance, we also found no direct link between the last saved pulmonary isolate from patients who subsequently developed “cepacia syndrome” and their capacity to resist the inhibitory effects of human serum, suggesting serum resistance cannot be used as a marker of an isolate’s capacity to escape from the lung and cause bacteremia.

PCR detection of Burkholderia cepacia complex as one of key factors to handle a long-term outbreak

BACKGROUND

Once the outbreak with Burkholderia cenocepacia ST32 was identified in the Prague cystic fibrosis (CF) centre, molecular tools were implemented into diagnostic routine in order to complement infection control measures with as accurate as possible microbiological service. In addition, genotyping techniques were applied as part of an infection surveillance program to assign species and strain status in samples positive for Burkholderia cepacia complex (Bcc). We sought to evaluate a usefulness of Bcc-specific PCR in infection control and to map evolution of the outbreak.

METHODS

Since 2001, 6109 respiratory samples from 299 CF patients were examined not only by conventional culture, but also by PCR, detecting Bcc directly in sputum.

RESULTS

Diagnosis of Bcc infection was established by culture in 54 patients already prior to 2001. As 39 more patients were diagnosed by culture and/or PCR during 2001-2010, this represented annual prevalence of 18.5%-28.9%. Twelve of 39 patients were culture negative at the time of their first PCR positivity. Although 2/3 of them became subsequently culture positive, the time delay in diagnostics of the infection by culture ranged from 1 to 22 months. New cases of Bcc infection were detected every year, however a dramatic drop was observed for the epidemic strain ST32.

CONCLUSION

A likely factor contributing to the end of ST32 epidemic was segregation of Bcc infected patients that included also patients with no culture, but PCR positivity. The diagnostic PCR led to timely identification of cases with 'culture-invisible' infection.

Cangene Gold Medal Award Lecture — Genomic analysis and modification ofBurkholderia cepaciacomplex bacteriophages1This article is based on a presentation by Dr. Karlene Lynch at the 61st Annual Meeting of the Canadian Society of Microbiologists in St. John’s, Newfoundland and Labrador, on 21 June 2011. Dr. Lynch was the recipient of the 2011 Cangene Gold Medal as the Canadian Graduate Student Microbiologist of the Year, an annual award sponsored by Cangene Corporation intended to recognize excellence in graduate research

The Burkholderia cepacia complex (Bcc) is a group of 17 Gram-negative predominantly environmental bacterial species that cause potentially fatal opportunistic infections in cystic fibrosis (CF) patients. Although its prevalence in these individuals is lower than that of Staphylococcus aureus and Pseudomonas aeruginosa , the Bcc remains a serious problem in the CF community because of the pathogenicity, transmissibility, and inherent antibiotic resistance of these organisms. An alternative treatment for Bcc infections that is currently being developed is phage therapy, the clinical use of viruses that infect bacteria. To assess the suitability of individual phage isolates for therapeutic use, the complete genome sequences of a panel of Bcc‐specific phages were determined and analyzed. These sequences encode a broad range of proteins with a gradient of relatedness to phage and bacterial gene products from Burkholderia and other genera. The majority of these phages were found not to encode virulence factors, and despite their predominantly temperate nature, a proof-of-principle experiment has shown that they may be modified to a lytic form. Both the genomic characterization and subsequent engineering of Bcc‐specific phages are fundamental to the development of an effective phage therapy strategy for these bacteria.

Global changes in gene expression by the opportunistic pathogen Burkholderia cenocepacia in response to internalization by murine macrophages

Background

Burkholderia cenocepacia is an opportunistic pathogen causing life-threatening infections in patients with cystic fibrosis. The bacterium survives within macrophages by interfering with endocytic trafficking and delaying the maturation of the B. cenocepacia-containing phagosome. We hypothesize that B. cenocepacia undergoes changes in gene expression after internalization by macrophages, inducing genes involved in intracellular survival and host adaptation.

Results

We examined gene expression by intracellular B. cenocepacia using selective capture of transcribed sequences (SCOTS) combined with microarray analysis. We identified 767 genes with significantly different levels of expression by intracellular bacteria, of which 330 showed increased expression and 437 showed decreased expression. Affected genes represented all aspects of cellular life including information storage and processing, cellular processes and signaling, and metabolism. In general, intracellular gene expression demonstrated a pattern of environmental sensing, bacterial response, and metabolic adaptation to the phagosomal environment. Deletion of various SCOTS-identified genes affected bacterial entry into macrophages and intracellular replication. We also show that intracellular B. cenocepacia is cytotoxic towards the macrophage host, and capable of spread to neighboring cells, a role dependent on SCOTS-identified genes. In particular, genes involved in bacterial motility, cobalamin biosynthesis, the type VI secretion system, and membrane modification contributed greatly to macrophage entry and subsequent intracellular behavior of B. cenocepacia.

Conclusions

B. cenocepacia enters macrophages, adapts to the phagosomal environment, replicates within a modified phagosome, and exhibits cytotoxicity towards the host cells. The analysis of the transcriptomic response of intracellular B. cenocepacia reveals that metabolic adaptation to a new niche plays a major role in the survival of B. cenocepacia in macrophages. This adaptive response does not require the expression of any specific virulence-associated factor, which is consistent with the opportunistic nature of this microorganism. Further investigation into the remaining SCOTS-identified genes will provide a more complete picture of the adaptive response of B. cenocepacia to the host cell environment.