European-wide distribution of Pseudomonas aeruginosa clone C

Why? - Successful Pseudomonas aeruginosa clones with a focus on clone C

The environmental species Pseudomonas aeruginosa thrives in a variety of habitats. Within the epidemic population structure of P. aeruginosa, occassionally highly successful clones that are equally capable to succeed in the environment and the human host arise. Framed by a highly conserved core genome, individual members of successful clones are characterized by a high variability in their accessory genome. The abundance of successful clones might be funded in specific features of the core genome or, although not mutually exclusive, in the variability of the accessory genome. In clone C, one of the most predominant clones, the plasmid pKLC102 and the PACGI-1 genomic island are two ubiquitous accessory genetic elements. The conserved transmissible locus of protein quality control (TLPQC) at the border of PACGI-1 is a unique horizontally transferred compository element, which codes predominantly for stress-related cargo gene products such as involved in protein homeostasis. As a hallmark, most TLPQC xenologues possess a core genome equivalent. With elevated temperature tolerance as a characteristic of clone C strains, the unique P. aeruginosa and clone C specific disaggregase ClpG is a major contributor to tolerance. As other successful clones, such as PA14, do not encode the TLPQC locus, ubiquitous denominators of success, if existing, need to be identified.

Factors influencing the acquisition and eradication of early Pseudomonas aeruginosa infection in cystic fibrosis

In recent years considerable improvements have been made in increasing the life expectancy of patients with cystic fibrosis. New highly effective modulator therapies targeting the underlying defect in the cystic fibrosis transmembrane conductance regulator protein are expected to enhance lifespan even further. However, chronic Pseudomonas aeruginosa pulmonary infections continue to threaten CF patient lung health and mortality rates. Early and aggressive antibiotic eradication therapies targeting P. aeruginosa are standard practice, but these eradication therapies fail in 10-40% of patients. The reasons for P. aeruginosa eradication failure remain unclear. Thus, this review summarizes the evidence to date for pseudomonal acquisition and eradication failure in the cystic fibrosis lung. A complex combination of host and bacterial factors are responsible for initial establishment of P. aeruginosa pulmonary infections. Moreover, host and pseudomonal factors, polymicrobial interactions, and antimicrobial limitations in relation to P. aeruginosa eradication therapy failure are summarized.

Comparison between Allura Red dye discoloration by activated carbon and azo bacteria strain

Azo dyes are extensively used in different industries areas, such as Allura Red (R-40). Previous studies have proven its carcinogenic and mutagenic properties. For the removal of this type of emerging pollutant from effluents, tertiary treatment techniques such as activated charcoal are used. Alternatively, the use of bacteria is preferred because of its quick discoloration processes. The aim of the present investigation is to compare the efficiency removal of R-40 from aqueous media by a physicochemical process and a biological one. The sorption kinetics of 10 ppm of R-40 was carried out with the use of activated charcoal based on walnut shells in water. Moreover, Pseudomonas aeruginosa and Bacillus subtilis stains were used separately to decolorize nutrient broth media supplemented with 50 ppm of R-40. The activated carbon was capable to remove 99.87% of R-40 at 264 h, while the bacterial strains decolorized 92.13% (P. aeruginosa) and 88.21% (B. subtilis), respectively, under microaerophilic conditions after 168 h. Therefore, both process strategies, physicochemical and biological rapprochements, were able to remove the dye from aqueous media. R-40 was not cytotoxic to used strains, besides gram-positive either negative bacteria could be applied to turn over this azo dye in short term. Combination of both approaches may be implemented in tandem architecture.

Environmental reservoirs for exoS+ and exoU+ strains of Pseudomonas aeruginosa

Pseudomonas aeruginosa uses its type III secretion system to inject the effector proteins ExoS and ExoU into eukaryotic cells, which subverts these cells to the bacterium's advantage and contributes to severe infections. We studied the environmental reservoirs of exoS+ and exoU+ strains of P. aeruginosa by collecting water, soil, moist substrates and plant samples from environments in the Chicago region and neighbouring states. Whole-genome sequencing was used to determine the phylogeny and type III secretion system genotypes of 120 environmental isolates. No correlation existed between geographic separation of isolates and their genetic relatedness, which confirmed previous findings of both high genetic diversity within a single site and the widespread distribution of P. aeruginosa clonal complexes. After excluding clonal isolates cultured from the same samples, 74 exoS+ isolates and 16 exoU+ isolates remained. Of the exoS+ isolates, 41 (55%) were from natural environmental sites and 33 (45%) were from man-made sites. Of the exoU+ isolates, only 3 (19%) were from natural environmental sites and 13 (81%) were from man-made sites (p < 0.05). These findings suggest that man-made water systems may be a reservoir from which patients acquire exoU+ P. aeruginosa strains.

Environmentally Endemic Pseudomonas aeruginosa Strains with Mutations in lasR Are Associated with Increased Disease Severity in Corneal Ulcers

The Steroids for Corneal Ulcers Trial (SCUT) was a multicenter, international study of bacterial keratitis in which 101 Pseudomonas aeruginosa infections were treated. Twenty-two of 101 P. aeruginosa isolates collected had a colony morphology characteristic of a loss-of-function mutation in lasR, the gene encoding a quorum-sensing master regulator. Ulcers caused by these 22 strains were associated with larger areas of corneal opacification, worse vision, and a lower rate of vision recovery in response to treatment than ulcers caused by the other isolates. The lasR sequences from these isolates each contained one of three nonsynonymous substitutions, and these strains were deficient in production of LasR-regulated protease and rhamnolipids. Replacement of lasR with either of the two most common lasR alleles from the SCUT isolates was sufficient to decrease protease and rhamnolipid production in PA14. Loss of LasR function is associated with increased production of CupA fimbriae, and the LasR-defective isolates exhibited higher production of CupA fimbriae than LasR-intact isolates. Strains with the same lasR mutation were of the same multilocus sequence type, suggesting that LasR-deficient, environmental P. aeruginosa strains were endemic to the area, and infections caused by these strains were associated with worse patient outcomes in the SCUT study. (This study has been registered at ClinicalTrials.gov under registration no. NCT00324168.) IMPORTANCE The LasR transcription factor is an important regulator of quorum sensing in P. aeruginosa and positively controls multiple virulence-associated pathways. The emergence of strains with lasR loss-of-function alleles in chronic disease is well described and is thought to represent a specific adaptation to the host environment. However, the prevalence and virulence of these strains in acute infections remain unclear. This report describes observations revealing that lasR mutants were common among isolates from a large, multicenter clinical study of keratitis and were associated with worse clinical outcomes than LasR-intact strains despite reduced production of LasR-regulated factors. Additionally, these lasR mutants were closely related strains or clones, as determined by molecular analysis. Because bacterial keratitis is community acquired, these data indicate infection by endemic, LasR-deficient strains in the environment. These results suggest that the conventional paradigm regarding the role for LasR-mediated regulation of virulence is more complex than previously appreciated.

Modulation of biofilm-formation in Salmonella enterica serovar Typhimurium by the periplasmic DsbA/DsbB oxidoreductase system requires the GGDEF-EAL domain protein STM3615

In Salmonella enterica serovar Typhimurium (S. Typhimurium), biofilm-formation is controlled by the cytoplasmic intracellular small-molecular second messenger cyclic 3′, 5′-di- guanosine monophosphate (c-di-GMP) through the activities of GGDEF and EAL domain proteins. Here we describe that deleting either dsbA or dsbB, respectively encoding a periplasmic protein disulfide oxidase and a cytoplasmic membrane disulfide oxidoreductase, resulted in increased biofilm-formation on solid medium. This increased biofilm-formation, defined as a red, dry and rough (rdar) colony morphotype, paralleled with enhanced expression of the biofilm master regulator CsgD and the biofilm-associated fimbrial subunit CsgA. Deleting csgD in either dsb mutant abrogated the enhanced biofilm-formation. Likewise, overexpression of the c-di-GMP phosphodiesterase YhjH, or mutationally inactivating the CsgD activator EAL-domain protein YdiV, reduced biofilm-formation in either of the dsb mutants. Intriguingly, deleting the GGDEF-EAL domain protein gene STM3615 (yhjK), previously not connected to rdar morphotype development, also abrogated the escalated rdar morphotype formation in dsb mutant backgrounds. Enhanced biofilm-formation in dsb mutants was furthermore annulled by exposure to the protein disulfide catalyst copper chloride. When analyzed for the effect of exogenous reducing stress on biofilm-formation, both dsb mutants initially showed an escalated rdar morphotype development that later dissolved to reveal a smooth mucoid colony morphotype. From these results we conclude that biofilm-development in S. Typhimurium is affected by periplasmic protein disulphide bond status through CsgD, and discuss the involvement of selected GGDEF/EAL domain protein(s) as signaling mediators.

Twenty-five-year outbreak of Pseudomonas aeruginosa infecting individuals with cystic fibrosis: identification of the prairie epidemic strain

Transmissible strains of Pseudomonas aeruginosa have been described for cystic fibrosis (CF) and may be associated with a worse prognosis. Using a comprehensive strain biobank spanning 3 decades, we sought to determine the prevalence and stability of chronic P. aeruginosa infection in an adult population. P. aeruginosa isolates from sputum samples collected at initial enrollment in our adult clinic and at the most recent clinic visit were examined by a combination of pulsed-field gel electrophoresis and multilocus sequence typing and compared against a collection of established transmissible and local non-CF bronchiectasis (nCFB) isolates. A total of 372 isolates from 107 patients, spanning 674 patient-years, including 66 patients with matched isolates from initial and final encounters, were screened. A novel clone with increased antibacterial resistance, termed the prairie epidemic strain (PES), was found in 29% (31/107 patients) of chronically infected patients referred from multiple prairie-based CF centers. This isolate was not found in those diagnosed with CF as adults or in a control population with nCFB. While 90% (60/66 patients) of patients had stable infection over a mean of 10.8 years, five patients experienced strain displacement of unique isolates, with PES occurring within 2 years of transitioning to adult care. PES has been present in our cohort since at least 1987, is unique to CF, generally establishes chronic infection during childhood, and has been found in patients at the time of transition of patients from multiple prairie-based CF clinics, suggesting broad endemicity. Studies are under way to evaluate the clinical implications of PES infection.

Halting the spread of epidemic pseudomonas aeruginosa in an adult cystic fibrosis centre: a prospective cohort study

Objectives

To assess if cohort segregation policies are effective in preventing cross-infection in cystic fibrosis (CF) clinics.

Design

A prospective cohort study.

Setting

A large adult CF centre in Northwest England.

Participants

All CF patients cared for at the Liverpool adult CF centre 2003–2009.

Methods

Regular sputum sampling with genotyping of pseudomonas aeruginosa (Psa) isolates led to a policy of inpatient and outpatient segregation by microbiological group.

Main outcome measures

Prevalence and cross-infection/super-infection rates of a transmissible Psa strain, i.e. the Liverpool epidemic strain (LES) in adult CF patients at the Liverpool adult CF centre from 2003 to 2009.

Results

There was a decline in the proportion of patients with LES (71–53%) and an increase in those with unique strains (23–31%) and without Psa infection (6–17%) from 2003 to 2009. There were two cases of LES super-infection and one case of new chronic Psa infection (with a unique strain). There were no cases of transmissible strain infection in patients previously uninfected by Psa.

Conclusions

Our segregation policy has halted the spread of the commonest highly transmissible strain in the UK (LES) in our clinic, without endangering patients who were not previously infected with Psa. It confirms that if genotypic surveillance is used, it is unnecessary to segregate patients infected with unique strains from those without Psa infection.

Increasing resistance of the Liverpool Epidemic Strain (LES) of Pseudomonas aeruginosa (Psa) to antibiotics in cystic fibrosis (CF)--a cause for concern?

BACKGROUND

Transmissible Pseudomonas aeruginosa (Psa) strains such as the Liverpool Epidemic Strain (LES) are now widespread throughout UK CF clinics: their susceptibility to antibiotics is therefore important. To study this, we compared antibiogram patterns of Psa strains in our CF clinic over 5 years, looking at differences in resistance patterns between strains and changes to these over time.

METHODS

The antibiograms of sputum samples between 2004 and 2008 from patients attending our centre were included. We compared Psa isolate antibiotic resistance (to six anti-pseudomonal antibiotics) patterns for patients infected with LES with those infected with other Psa strains, both in the total population in 2004 (125 patients) and 2008 (166 patients) and also longitudinally from annual review samples 2004 to 2008 in matched and unmatched patient groups.

RESULTS

LES exhibited significantly more resistant isolates in 2004 (p<0.0001). There was an increase in antibiotic resistance in both LES and other Psa strains over time (p<0.001). Cox proportional hazards analysis of both unmatched (n=125) and matched (n=56) patients in 2004 revealed that LES infected patients were more likely to develop antibiotic resistant isolates over time (hazard ratio 8.1, p<0.001). Fewer LES isolates were classed as fully sensitive in both matched and unmatched groups at the end of study period (p<0.001).

CONCLUSION

This study shows a worrying trend in antibiotic resistance in the Psa isolates amongst patients chronically infected with LES. This highlights the need to prevent cross infection through segregation and also the need to develop new strategies to treat these organisms.

Multidrug-resistant epidemic clones among bloodstream isolates of Pseudomonas aeruginosa in the Czech Republic

To determine whether the high proportion of antimicrobial resistance among hospital isolates of Pseudomonas aeruginosa in the Czech Republic is associated with the spread of multidrug-resistant clones, we investigated 108 bloodstream isolates collected prospectively in 2007. The isolates originated from 48 hospitals in 36 cities and were serotyped, tested for susceptibility to 10 anti-Pseudomonas agents and studied by multilocus sequence typing, macrorestriction analysis and class 1 integron typing. Forty-five isolates were fully susceptible, while 14 and 49 isolates were resistant to 1-2 and 3-9 agents, respectively. A total of 42 multilocus sequence types (ST) were identified, of which ST235 (serotype O11), ST175 (O4) and ST132 (O6) included 19, 16 and 5 isolates, respectively. These three STs encompassed 40 (82%) of 49 isolates resistant to more than two agents and originated from 29 hospitals in 22 cities. Isolates of the same ST had highly similar macrorestriction patterns. Twelve ST235 isolates harbored an integron variable region with the gene cassette array of aacA7-aadA6-orfD, while 15 ST175 isolates shared a region with the aadB-aadA13 array and all ST132 isolates carried a region with aacA4. A carbapenemase-encoding gene (bla(IMP-7)) was detected in a single strain (ST357). In conclusion, the multidrug resistance of Czech P. aeruginosa bloodstream isolates in 2007 was predominantly associated with three epidemic clones, one of which belongs to international clonal complex CC235.

Small Heat Shock Proteins Produced by Pseudomonas Aeruginosa Clonal Variants Isolated from Diverse Niches

Genomic islands interspersed in the chromosome of P. aeruginosa led to inter- and intraclonal diversity. Recently, a particular clone of P. aeruginosa called clone C was isolated from cystic fibrosis (CF) patients, clinical and non-clinical habitats throughout Europe and in Canada. P. aeruginosa clone C strains harbour up to several hundred acquired genes involved in the adaptation of bacteria to diverse niches. Two genes ( hp25 and hp18) from one of the hypervariable regions in the chromosome of clone C strains were highly expressed under standard culture conditions as well as under conditions that mimicked CF sputum environment. Protein sequence analysis revealed that Hp25 and Hp18 belonged to small heat shock protein (sHSP) family. Hp25 protein possessed α-crystallin domain, which is a conserved region among heat shock proteins involved in diverse functions. Sequence homology search revealed that in the Methylobacillus flagellatus genome both genes were situated close to each other and the hp25 gene is found among a few other members of Proteobacteria. Expression of hp25 and hp18 by inter- and intraclonal strains of P. aeruginosa suggested that both genes were present in the stable part of the hypervariable region at the toxR locus and might play a role in their adaptation to diverse niches including the CF lung environment.

Prevalence and transmission of antimicrobial resistance among Aeromonas populations from a duckweed aquaculture based hospital sewage water recycling system in Bangladesh

In order to investigate the influence of a duckweed aquaculture based hospital sewage water recycling plant on the prevalence and dissemination of antibiotic resistance, we made use of an existing collection of 1,315 Aeromonas isolates that were previously typed by the biochemical fingerprinting PhP-AE system. In these treatment plant, hospital raw sewage water is first collected in a settlement pond (referred to as sewage water in this study) and is then transferred to a lagoon, where the duckweed (Lemnaceae) is grown (referred to as lagoon). The duckweed is harvested and used as feed for the fish in a separate pond (referred to as fish pond). From this collection, representatives of 288 PhP types were subjected to antibiotic susceptibility testing for eight antimicrobials by broth microdilution method. The overall resistance rates among Aeromonas isolates from the treatment plant were highest for ampicillin (87%) and erythromycin (79%) followed by cephalothin (58%), nalidixic acid (52%), streptomycin (51%), tetracycline (31%), chloramphenicol (13%) and gentamicin (8%). A significantly lower prevalence of antibiotic resistance was found in Aeromonas from environmental control water, patient stool samples, duckweed and fish compared to sewage water isolates. The prevalence of resistance in the sewage water was not significantly reduced compared to the lagoon water and fish pond. Throughout the treatment system, the frequencies of resistant strains were found to diminish during the sewage water purification process, i.e. in the lagoon where sewage water is used to grow the duckweed. However, the frequency of resistant strains again increased in the fish pond where sewage grown duckweed is used for aquaculture. Among the selected isolates, two multiresistant clonal groups of Aeromonas caviae HG4 were identified that exhibited indistinguishable PhP and amplified fragment length polymorphism fingerprints and shared a common plasmid of approximately 5 kb. Representatives of both groups were recovered from almost every part of the sewage treatment plant but not in the control ponds nor in human samples, which suggests that specific multiresistant Aeromonas clones are able to persist and spread throughout the entire purification process.

Antibiotic susceptibility patterns and clones of Pseudomonas aeruginosa in Swedish ICUs

Pseudomonas aeruginosa is 1 of the bacteria most adaptive to anti-bacterial treatment. Previous studies have shown nosocomial spread and transmission of clonal strains of P. aeruginosa in European hospitals. In this study we investigated antibiotic susceptibility and clonality in 101 P. aeruginosa isolates from 88 patients admitted to 8 Swedish ICUs during 2002. We also compared phenotypes and genotypes of P. aeruginosa and carried out cluster analysis to determine if phenotypic data can be used for surveillance of clonal spread. All isolates were collected on clinical indication as part of the NPRS II study in Sweden and were subjected to AFLP analysis for genotyping. 68 isolates with unique genotypes were found. Phenotyping was performed using MIC values for 5 anti-pseudomonal agents. Almost 6% of the isolates were multi-drug resistant (MDR), and this figure rose to almost 8% when intermediate isolates were also included. We found probable clonal spread in 9 cases, but none of them was found to be an MDR strain. Phenotypical cluster analysis produced 40 clusters. Comparing partitions did not demonstrate any significant concordance between the typing methods. The conclusion of our study is that cross-transmission and clonal spread of MDR P. aeruginosa does not present a clinical problem in Swedish ICUs, but probable cross-transmission of non-MDR clones indicate a need for improved hygiene routines bedside. The phenotype clusters were not concordant with genotype clusters, and genotyping is still recommended for epidemiological tracking.

Pseudomonas aeruginosa diversity in distinct paediatric patient groups

Pseudomonas aeruginosa is a pathogen that often infects patients who are either immunocompromised or have local defects in host defences. It is known that cystic fibrosis (CF) patients are sometimes infected with certain clonal isolates. It is not clear whether these clonal isolates also infect non-CF patients and whether clonality of isolates occurs in other patient groups. The aim of this study was to investigate P. aeruginosa diversity and the occurrence of clones within five distinct paediatric patient groups susceptible to P. aeruginosa infection. P. aeruginosa isolates were cultured from 157 patients (CF first infection (CF-1 group) (29); CF chronic infection (CF-chronic group) (27); urinary tract infection (34); chronic suppurative otitis media (43); and intensive-care hospitalization/immunodeficiency (24)). All 202 phenotypically different isolates were tested for antimicrobial resistance and further typed by pulsed-field gel electrophoresis. Simpson's diversity index was calculated for the five groups. CF-chronic patients carried the highest number of distinct P. aeruginosa phenotypes and genotypes per culture. Isolates from the CF-chronic group were significantly less diverse than those from the other groups. A group of clonal isolates was observed among patients from the CF-chronic and CF-1 groups. These or different clonal isolates were not encountered among the three other patient groups. No characteristic resistance pattern could be identified among isolates from the distinct patient groups and among the clonal isolates. In conclusion, isolates of the CF-chronic group were less diverse than those in the other patient groups with P. aeruginosa infection; clonal isolates were not encountered in non-CF patients. Transmission of clonal CF isolates to other patient groups was not observed.

Biological cost of hypermutation in Pseudomonas aeruginosa strains from patients with cystic fibrosis

The high prevalence of hypermutable (mismatch repair-deficient) Pseudomonas aeruginosa strains in patients with cystic fibrosis (CF) is thought to be driven by their co-selection with adaptive mutations required for long-term persistence. Whether the increased mutation rate of naturally hypermutable strains is associated with a biological benefit or cost for the colonization of secondary environments is not known. Thirty-nine P. aeruginosa strains were collected from ten patients with CF during their course of chronic lung infections and screened for hypermutability. Seven hypermutable P. aeruginosa strains (18 %) isolated from six patients with CF (60 %) were identified and assigned to five different genotypes. Complementation and sequence analysis in the mutS, mutL and uvrD genes of these hypermutable P. aeruginosa strains revealed novel mutations. To understand the consequences of hypermutation for the fitness of the organisms, five pairs of clinical wild-type/hypermutable, clonally related P. aeruginosa strains and the laboratory strains PAO1/PAO1DeltamutS were subjected to competition in vitro and in the agar-beads mouse model of chronic airway infection. When tested in competition assay in vitro, the wild-type outcompeted four clinical hypermutable strains and the PAO1DeltamutS strain. In vivo, all of the hypermutable strains were less efficient at establishing lung infection than their wild-type clones. These results suggest that P. aeruginosa hypermutation is associated with a biological cost, reducing the potential for colonization of new environments and therefore strain transmissibility.

High genotypic diversity of Pseudomonas aeruginosa strains isolated from patients with cystic fibrosis in the Czech Republic

Over the last decade, epidemic and frequently multidrug-resistant Pseudomonas aeruginosa has increasingly been found among European cystic fibrosis (CF) patients. In the Czech Republic, more than half of the registered CF patients attend the Prague CF centre. At this centre, a Burkholderia cenocepacia strain was recently found to have spread among the patients. The aim of the present study was to assess whether P. aeruginosa isolates from patients at this centre were also genetically related and, if so, whether they were multidrug-resistant. We investigated a collection of 69 isolates from as many patients who represented 80% of the total number of P. aeruginosa-positive patients in 2004. The organisms were typed by AFLP and SpeI macrorestriction analyses (PFGE). Using these methods, 44 unique strains and nine groups of two to five isolates each were distinguished. Among these groups, two each had a prevalence of 7% in the patient population, while others had a prevalence of < or =3%. The diversity observed with PFGE was largely in agreement with the diversity found by AFLP analysis. All isolates were susceptible to colistin; 94-96% were susceptible to piperacillin, ceftazidime, cefepime, meropenem, amikacin or tobramycin; and 84-87% were susceptible to ciprofloxacin, gentamicin or netilmicin. In conclusion, the organisms recovered from Czech CF patients showed high genotypic diversity and good susceptibility to antipseudomonal agents. The absence of highly epidemic P. aeruginosa strains may result from infection control measures taken upon recognition of the epidemic B. cenocepacia.

Sequence diversity of the mucABD locus in Pseudomonas aeruginosa isolates from patients with cystic fibrosis

The mucA gene of the muc operon, which is instrumental in the control of the biosynthesis of the exopolysaccharide alginate, is a hotspot of mutation in Pseudomonas aeruginosa, a micro-organism that chronically colonizes the airways of individuals with cystic fibrosis (CF). The mucA, mucB and mucD genes were sequenced in nine environmental isolates from aquatic habitats, and in 37 P. aeruginosa strains isolated from 10 patients with CF, at onset or at a late stage of chronic airway colonization, in order to elucidate whether there was any association between mutation and background genotype. The 61 identified single nucleotide polymorphisms (SNPs) segregated into 18 mucABD genotypes. Acquired and de novo stop mucA mutations were present in 14 isolates (38 %) of five mucABD genotypes. DeltaG430 was the most frequent and recurrent mucA mutation detected in four genotypes. The classification of strains by mucABD genotype was generally concordant with that by genome-wide SpeI fragment pattern or multilocus SNP genotypes. The exceptions point to intragenic mosaicism and interclonal recombination as major forces for intraclonal evolution at the mucABD locus.

Transmission of Burkholderia cepacia complex: evidence for new epidemic clones infecting cystic fibrosis patients in Italy

To analyze national prevalence, genomovar distribution, and epidemiology of the Burkholderia cepacia complex in Italy, 225 putative B. cepacia complex isolates were obtained from 225 cystic fibrosis (CF) patients attending 18 CF centers. The genomovar status of these isolates was determined by a polyphasic approach, which included whole-cell protein electrophoresis and recA restriction fragment length polymorphism (RFLP) analysis. Two approaches were used to genotype B. cepacia complex isolates: BOX-PCR fingerprinting and pulsed-field gel electrophoresis (PFGE) of genomic macrorestriction fragments. A total of 208 (92%) of 225 isolates belonged to the B. cepacia complex, with Burkholderia cenocepacia as the most prevalent species (61.1%). Clones delineated by PFGE were predominantly linked to a single center; in contrast, BOX-PCR clones were composed of isolates collected either from the same center or from different CF centers and comprised multiple PFGE clusters. Three BOX-PCR clones appeared of special interest. One clone was composed of 17 B. cenocepacia isolates belonging to recA RFLP type H. These isolates were collected from six centers and represented three PFGE clusters. The presence of insertion sequence IS 1363 in all isolates and the comparison with PHDC reference isolates identified this clone as PHDC, an epidemic clone prominent in North American CF patients. The second clone included 22 isolates from eight centers and belonged to recA RFLP type AT. The genomovar status of strains with the latter RFLP type is not known. Most of these isolates belonged to four different PFGE clusters. Finally, a third clone comprised nine B. pyrrocinia isolates belonging to recA RFLP type Se 13. They represented three PFGE clusters and were collected in three CF centers.

Proteome analysis reveals adaptation ofPseudomonas aeruginosa to the cystic fibrosis lung environment

Pseudomonas aeruginosa is known for the chronic lung colonization of cystic fibrosis (CF) patients in addition to eye, ear and urinary tract infections. With the underlying disease CF patients are predisposed to P. aeruginosa chronic lung infection, which leads to morbidity and mortality. In this study, we compared the protein expression profile of a CF lung-adapted P. aeruginosa strain C with that of the burn-wound isolate PAO. Differentially expressed proteins from the whole-cell, membrane, periplasmic as well as extracellular fraction were identified. The whole-cell proteome of strain C showed down-regulation of several proteins involved in amino acid metabolism, fatty acid metabolism, energy metabolism and adaptation leading to a highly distinct proteome pattern for strain C in comparison to PAO. Analysis of secreted proteins by strain C compared to PAO revealed differential expression of virulence factors under non-inducing conditions. The membrane proteome of strain C showed modulation of the expression of porins involved in nutrient and antibiotic influx. The proteome of the periplasmic space of strain C showed retention of elastase despite that the equal amounts were secreted by strain C and PAO. Altogether, our results elucidate adaptive strategies of P. aeruginosa towards the nutrient-rich CF lung habitat during the course of chronic colonization.

Global Pseudomonas aeruginosa biodiversity as reflected in a Belgian river

The biodiversity of the bacterium Pseudomonas aeruginosa in an aquatic environment (the Woluwe River, Brussels, Belgium) was analysed. Surface water was sampled bimonthly over a 1-year period (2000-2001) at seven sites evenly dispersed over the river. Total bacterial counts were performed and P. aeruginosa strains were isolated on a selective medium. A weighed out sample of 100 randomly chosen presumptive P. aeruginosa isolates was further analysed. A set of data consisting of the nucleotide sequence of the oprL gene, a DNA-based fingerprint (amplified fragment length polymorphism, AFLP), serotype, pyoverdine type and antibiogram (MICs of 21 clinically relevant antibiotics) was assembled. These data were integrated with those previously obtained for 73 P. aeruginosa clinical and environmental isolates collected across the world. The combined results were analysed and compared using biological data analysis software. Our findings indicate a positive relationship between the extent of pollution and the prevalence of P. aeruginosa. Surprisingly, the Woluwe River P. aeruginosa community was almost as diverse as the global P. aeruginosa population. Indeed, the Woluwe River harboured members of nearly all successful clonal complexes. With the exception of one multidrug-resistant (MDR) strain, belonging to a ubiquitous and clinically relevant serotype O11 clone, antibiotic resistance levels were relatively low. These findings illustrate the significance of river water as a reservoir and source of distribution of potentially pathogenic P. aeruginosa strains and could have repercussions on antinosocomial infection strategies.

Worldwide distribution of Pseudomonas aeruginosa clone C strains in the aquatic environment and cystic fibrosis patients

Highly successful bacterial clones have the ability to effectively colonize environmental niches and patients. However, the factors which determine the complex interplay between the colonization of environmental niches and patients are mainly unknown. In this study we show that Pseudomonas aeruginosa clone C strains are distributed worldwide and highly prone to infect cystic fibrosis (CF) patients in Canada, England, France and Germany. In Hanover, Germany and Vancouver, Canada, clone C strains are highly prevalent in the CF patient community, although the mechanisms of acquisition may have been different. All clone C strains showed highly related macrorestriction fragment pattern of the whole genome as visualized by pulsed-field gel electrophoresis and harboured the 102 kbp plasmid pKLC102. Comparison of three prevalent P. aeruginosa clones with different distribution between the environment and patients revealed that neither enhanced biofilm formation nor antibiotic resistance was responsible for the spread of clone C. Clone M, which was highly prevalent in the clinical environment such as sanitary facilities, lacked motility, which could explain its relatively low prevalence in CF patients. Elucidation of the mechanisms which lead to the prevalence of clone C strain in patients and the environment requires the investigation of additional phenotypes.

Development of a multilocus sequence typing scheme for the opportunistic pathogen Pseudomonas aeruginosa

A multilocus sequence typing (MLST) scheme has been developed for Pseudomonas aeruginosa which provides molecular typing data that are highly discriminatory and electronically portable between laboratories. MLST data confirm the data from previous studies that suggest that P. aeruginosa is best described as nonclonal but as having an epidemic population. The index of association was 0.17, indicating a freely recombining population; however, there was evidence of clusters of closely related strains or clonal complexes among the members of this population. It is apparent that the sequence types (STs) from single isolates, representing each of the present epidemic clones in the United Kingdom from Liverpool, Manchester, and the West Midlands, are not closely related to each other. This suggests distinct evolutionary origins for each of these epidemic clones in the United Kingdom. Furthermore, these clones are distinct from European clone C. Comparison of the results of MLST with those of toxA typing and serotyping revealed that strains with identical STs may possess different toxA types and diverse serotypes. Given that recombination is important in the population of P. aeruginosa, the lack of a linkage between toxA type and serotype is not surprising and reveals the strength of the MLST approach for obtaining a better understanding of the epidemiology of P. aeruginosa.

Identification and characterization of transmissible Pseudomonas aeruginosa strains in cystic fibrosis patients in England and Wales

Most past studies of cross-infection with Pseudomonas aeruginosa among cystic fibrosis (CF) patients in the UK suggest that it is a rare occurrence. However, two recent reports of highly transmissible strains in patients in regional centres in England (Liverpool and Manchester) have raised questions as to the extent of the problem and prompted a nationwide survey to establish the distribution of P. aeruginosa strain genotypes among these patients. Isolates of P. aeruginosa were requested from over 120 hospitals in England and Wales and a sample size of approximately 20% of the CF patient population in each centre was recommended. In total, 1225 isolates were received from 31 centres (range 1 to 330). Single patient isolates were typed by SpeI macrorestriction and PFGE. A panel of strains of the common genotypes including representatives of reported transmissible strains was assembled and further characterized by fluorescent amplified fragment length polymorphism (FAFLP) genotyping. At least 72% of all patients harboured strains with unique genotypes. Small clusters of related strains were evident in some centres, presumably indicating limited transmission of local strains. The most prevalent strain was indistinguishable from that previously described as the 'Liverpool' genotype, and accounted for approximately 11% of patient isolates from 15 centres in England and Wales. The second most common genotype (termed Midlands 1) was recovered from 86 patients in nine centres and the third genotype, which matched closely the PFGE profile of Clone C, a genotype originally described in Germany, was found in eight centres and was isolated from 15 patients. A fourth genotype, identical to the published Manchester strain, was found in three centres. FAFLP analysis revealed some microheterogeneity among strains of the Liverpool genotype but all isolates of this genotype were positive by PCR for a strain-specific marker. These data suggest that cross-infection with P. aeruginosa has occurred both within and widely between CF centres in England and Wales. The two most common genotypes accounted for more than one-fifth of patients' isolates examined and transmissible genotypes were found in all but three centres studied. These results emphasize the need for continued surveillance of P. aeruginosa genotypes in CF patients to provide informed infection control policy in treatment centres.