Pseudomonas aeruginosa cross-colonization and persistence in patients with cystic fibrosis. Use of a DNA probe

Minimising the risk of cross infection between siblings with cystic fibrosis (CF) within the home: Successful domestic steam disinfection of CF bacterial and foodborne pathogens on common household cutlery and crockery utensils

Avoidance of cross infection is important between CF siblings living in the same household. In this study, we examined the ability of domestic steam disinfection to eradicate 16 species of CF bacterial and foodborne pathogens from the surface of contaminated crockery and cutlery. Domestic steam disinfection employing baby bottle disinfector devices, when performed properly under manufacturer's instructions, eradicated all organisms tested and offers a relatively inexpensive, simple, versatile and widely available technology for the elimination of common CF bacterial and foodborne pathogens from contaminated crockery and cutlery utensils. Most CF households may already have a baby bottle disinfector device, in order to disinfect nebulizers, respiratory equipment and toothbrushes and therefore employment of this device to disinfect crockery and cutlery would be easily achieved. We therefore advocate the employment of such devices to disinfect such common household utensils, as a critical control in the elimination of these organisms from these sources, thereby enhancing CF sibling safety.

Pseudomonas aeruginosa: An Audacious Pathogen with an Adaptable Arsenal of Virulence Factors

Pseudomonas aeruginosa is a dominant pathogen in people with cystic fibrosis (CF) contributing to morbidity and mortality. Its tremendous ability to adapt greatly facilitates its capacity to cause chronic infections. The adaptability and flexibility of the pathogen are afforded by the extensive number of virulence factors it has at its disposal, providing P. aeruginosa with the facility to tailor its response against the different stressors in the environment. A deep understanding of these virulence mechanisms is crucial for the design of therapeutic strategies and vaccines against this multi-resistant pathogen. Therefore, this review describes the main virulence factors of P. aeruginosa and the adaptations it undergoes to persist in hostile environments such as the CF respiratory tract. The very large P. aeruginosa genome (5 to 7 MB) contributes considerably to its adaptive capacity; consequently, genomic studies have provided significant insights into elucidating P. aeruginosa evolution and its interactions with the host throughout the course of infection.

Pseudomonas aeruginosa Volatilome Characteristics and Adaptations in Chronic Cystic Fibrosis Lung Infections

Pseudomonas aeruginosa is a leading cause of chronic lung infections in cystic fibrosis (CF), which are correlated with lung function decline. Significant clinical efforts are therefore aimed at detecting infections and tracking them for phenotypic changes, such as mucoidy and antibiotic resistance. Both the detection and tracking of lung infections rely on sputum cultures, but due to improvements in CF therapies, sputum production is declining, although risks for lung infections persist. Therefore, we are working toward the development of breath-based diagnostics for CF lung infections. In this study, we characterized of the volatile metabolomes of 81 P. aeruginosa clinical isolates collected from 17 CF patients over a duration of at least 5 years of a chronic lung infection. We found that the volatilome of P. aeruginosa adapts over time and is correlated with infection phenotype changes, suggesting that it may be possible to track chronic CF lung infections with a breath test.

Pseudomonas aeruginosa chronic lung infections in individuals with cystic fibrosis (CF) significantly reduce quality of life and increase morbidity and mortality. Tracking these infections is critical for monitoring patient health and informing treatments. We are working toward the development of novel breath-based biomarkers to track chronic P. aeruginosa lung infections in situ. Using comprehensive two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (GC×GC–TOF-MS), we characterized the in vitro volatile metabolomes (“volatilomes”) of 81 P. aeruginosa isolates collected from 17 CF patients over at least a 5-year period of their chronic lung infections. We detected 539 volatiles produced by the P. aeruginosa isolates, 69 of which were core volatiles that were highly conserved. We found that each early infection isolate has a unique volatilome, and as infection progresses, the volatilomes of isolates from the same patient become increasingly dissimilar, to the point that these intrapatient isolates are no more similar to one another than to isolates from other patients. We observed that the size and chemical diversity of P. aeruginosa volatilomes do not change over the course of chronic infections; however, the relative abundances of core hydrocarbons, alcohols, and aldehydes do change and are correlated with changes in phenotypes associated with chronic infections. This study indicates that it may be feasible to track P. aeruginosa chronic lung infections by measuring changes to the infection volatilome and lays the groundwork for exploring the translatability of this approach to direct measurement using patient breath.

IMPORTANCEPseudomonas aeruginosa is a leading cause of chronic lung infections in cystic fibrosis (CF), which are correlated with lung function decline. Significant clinical efforts are therefore aimed at detecting infections and tracking them for phenotypic changes, such as mucoidy and antibiotic resistance. Both the detection and tracking of lung infections rely on sputum cultures, but due to improvements in CF therapies, sputum production is declining, although risks for lung infections persist. Therefore, we are working toward the development of breath-based diagnostics for CF lung infections. In this study, we characterized of the volatile metabolomes of 81 P. aeruginosa clinical isolates collected from 17 CF patients over a duration of at least 5 years of a chronic lung infection. We found that the volatilome of P. aeruginosa adapts over time and is correlated with infection phenotype changes, suggesting that it may be possible to track chronic CF lung infections with a breath test.

Epidemiology, Biology, and Impact of Clonal Pseudomonas aeruginosa Infections in Cystic Fibrosis

Chronic lower airway infection with Pseudomonas aeruginosa is a major contributor to morbidity and mortality in individuals suffering from the genetic disease cystic fibrosis (CF). Whereas it was long presumed that each patient independently acquired unique strains of P. aeruginosa present in their living environment, multiple studies have since demonstrated that shared strains of P. aeruginosa exist among individuals with CF. Many of these shared strains, often referred to as clonal or epidemic strains, can be transmitted from one CF individual to another, potentially reaching epidemic status. Numerous epidemic P. aeruginosa strains have been described from different parts of the world and are often associated with an antibiotic-resistant phenotype. Importantly, infection with these strains often portends a worse prognosis than for infection with nonclonal strains, including an increased pulmonary exacerbation rate, exaggerated lung function decline, and progression to end-stage lung disease. This review describes the global epidemiology of clonal P. aeruginosa strains in CF and summarizes the current literature regarding the underlying biology and clinical impact of globally important CF clones. Mechanisms associated with patient-to-patient transmission are discussed, and best-evidence practices to prevent infections are highlighted. Preventing new infections with epidemic P. aeruginosa strains is of paramount importance in mitigating CF disease progression.

How to manage Pseudomonas aeruginosa infections

Infections with Pseudomonas aeruginosa have become a real concern in hospital-acquired infections, especially in critically ill and immunocompromised patients. The major problem leading to high mortality lies in the appearance of drug-resistant strains. Therefore, a vast number of approaches to develop novel anti-infectives is currently pursued. Diverse strategies range from killing (new antibiotics) to disarming (antivirulence) the pathogen. In this review, selected aspects of P. aeruginosa antimicrobial resistance and infection management will be addressed. Many studies have been performed to evaluate the risk factors for resistance and the potential consequences on mortality and attributable mortality. The review also looks at the mechanisms associated with resistance – P. aeruginosa is a pathogen presenting a large genome, and it can develop a large number of factors associated with antibiotic resistance involving almost all classes of antibiotics. Clinical approaches to patients with bacteremia, ventilator-associated pneumonia, urinary tract infections and skin soft tissue infections are discussed. Antibiotic combinations are reviewed as well as an analysis of pharmacokinetic and pharmacodynamic parameters to optimize P. aeruginosa treatment. Limitations of current therapies, the potential for alternative drugs and new therapeutic options are also discussed.

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.

Genetic relatedness and host specificity of Pseudomonas aeruginosa isolates from cystic fibrosis and non-cystic fibrosis patients

BACKGROUND

Pseudomonas aeruginosa is one of the primary pathogens isolated more frequently in cystic fibrosis (CF) and it exhibits innate resistance to a wide range of antibiotics.

PURPOSE

We sought to determine whether the highly prevalent genotypes of P. aeruginosa are specifically linked to CF patients and have any related multidrug antibiotic resistance. Isolates from hospitalized non-CF patients and from environmental sources were also genotypically analyzed.

METHODS

Collections of P. aeruginosa from lower respiratory secretions (n=45) were genotyped using pulsed-field gel electrophoresis (PFGE). Phenotypic screening for antibiotic susceptibility was performed for the common antimicrobial agents by E-test and automated Phoenix method.

RESULTS

P. aeruginosa isolates from CF (n=32), hospitalized non-CF patients (n=13), and environment sources (n=5) were analyzed. The population structure of P. aeruginosa is highly diverse and population-specific. All PFGE results of P. aeruginosa isolates fall among four major clusters. Cluster 1 contained 16 P. aeruginosa isolates from CF patients and two from environmental sources; cluster 2 contained 11 P. aeruginosa isolates from CF and one each from non-CF and environmental sources; cluster 3 contained 12 P. aeruginosa isolates from hospitalized non-CF patients and two P. aeruginosa isolates from one CF patient and one environmental source; and cluster 4 consisted of three isolates from CF patients and one from the environment. The majority of multidrug-resistant P. aeruginosa isolates were in clusters 3 and 4. P. aeruginosa isolates from CF patients were resistant to ciprofloxacin (34.4%) followed by resistance to amikacin and gentamicin (each 28%), whereas the majority of isolates from non-CF patients were resistant to meropenem (69%) and were grouped in cluster 3.

CONCLUSION

PFGE of P. aeruginosa isolates from CF patients shows a high degree of similarity, suggesting specific adaptation of these clones to CF-affected lungs. The hospitalized non-CF cluster has a different clonal origin, indicating specific clustering in a specific location, suggesting hospital-acquired P. aeruginosa infections.

Genotypic diversity of Pseudomonas aeruginosa in cystic fibrosis siblings in Qatar using AFLP fingerprinting

Pseudomonas aeruginosa is one of the primary pathogens in patients with cystic fibrosis (CF) and a major cause of morbidity and mortality. Reports of the spread of epidemic or transmissible strains of P. aeruginosa within and across CF centers raised the possibility of clonal spread among siblings with CF. This work reports the genotypic relatedness of P. aeruginosa in CF patients with the CFTR I1234V mutation, and to determine whether the genotypes are identical among CF siblings and among different families with the same CFTR mutation. Sixty-six P. aeruginosa isolates were obtained from sputa/deep-pharyngeal swabs from 27 CF patients belonging to 17 families. Genotypic relatedness was assessed using amplified fragment-length polymorphism (AFLP) fingerprinting. Twenty-three distinct genotypes of P. aeruginosa were identified. Eleven families each had one distinct genotype. In the other 6 families more than one genotype was observed; 3 families each showed two genotypes, 2 families each had three genotypes and 1 family had four genotypes of P. aeruginosa. In several cases, siblings with CF from the same family harbored the same strain of P. aeruginosa, which were different from the genotypes in other families. On the other hand, there was an overlap in P. aeruginosa between closely related families. Some patients show persistent colonization with the same genotype of P. aeruginosa over the longitudinal period. The presence of the same genotypes in siblings of the same family and closely related families suggests cross-transmission of P. aeruginosa or acquisition from common environmental exposure.

The MerR-like regulator BrlR impairs Pseudomonas aeruginosa biofilm tolerance to colistin by repressing PhoPQ

While the MerR-like transcriptional regulator BrlR has been demonstrated to contribute to Pseudomonas aeruginosa biofilm tolerance to antimicrobial agents known as multidrug efflux pump substrates, the role of BrlR in resistance to cationic antimicrobial peptides (CAP), which is based on reduced outer membrane susceptibility, is not known. Here, we demonstrate that inactivation of brlR coincided with increased resistance of P. aeruginosa to colistin, while overexpression of brlR resulted in increased susceptibility. brlR expression correlated with reduced transcript abundances of phoP, phoQ, pmrA, pmrB, and arnC. Inactivation of pmrA and pmrB had no effect on the susceptibility of P. aeruginosa biofilms to colistin, while inactivation of phoP and phoQ rendered biofilms more susceptible than the wild type. The susceptibility phenotype of ΔphoP biofilms to colistin was comparable to that of P. aeruginosa biofilms overexpressing brlR. BrlR was found to directly bind to oprH promoter DNA of the oprH-phoPQ operon. BrlR reciprocally contributed to colistin and tobramycin resistance in P. aeruginosa PAO1 and CF clinical isolates, with overexpression of brlR resulting in increased tobramycin MICs and increased tobramycin resistance but decreased colistin MICs and increased colistin susceptibility. The opposite trend was observed upon brlR inactivation. The difference in susceptibility to colistin and tobramycin was eliminated by combination treatment of biofilms with both antibiotics. Our findings establish BrlR as an unusual member of the MerR family, as it not only functions as a multidrug transport activator, but also acts as a repressor of phoPQ expression, thus suppressing colistin resistance.

The changing microbial epidemiology in cystic fibrosis

Infection of the airways remains the primary cause of morbidity and mortality in persons with cystic fibrosis (CF). This review describes salient features of the epidemiologies of microbial species that are involved in respiratory tract infection in CF. The apparently expanding spectrum of species causing infection in CF and recent changes in the incidences and prevalences of infection due to specific bacterial, fungal, and viral species are described. The challenges inherent in tracking and interpreting rates of infection in this patient population are discussed.

Infection control in cystic fibrosis: cohorting, cross-contamination, and the respiratory therapist

Cystic fibrosis (CF) is a complex genetic disease characterized by lung infections that lead to early morbidity and death. Pathogens that commonly infect the lungs of patients with CF include Staphylococcus aureus, Haemophilus influenzae, Pseudomonas aeruginosa, and Burkholderia cepacia. Aggressively treating pulmonary infection with antibiotics has contributed to improved survival in patients with CF but has also promoted multiple-drug-resistant bacteria. Other complexities include the ability of bacteria to form biofilms, which makes them more resistant to antibiotics, and emerging pathogens in CF, of which the clinical importance is not yet clear. Increasing evidence of patient-to-patient transmission of CF pathogens led the Cystic Fibrosis Foundation to produce evidence-based infection-control recommendations, which stress 4 principles: standard precautions, transmission-based precautions, hand hygiene, and care of respiratory equipment. Respiratory therapists need to know and follow these infection-control recommendations. Cohorting patients infected with B. cepacia complex is one of several interventions successful at keeping the spread of this pathogen low, but cohorting patients who are infected/colonized with other microbes is controversial, the main argument of which is not being certain of a patient's present respiratory culture status at any given patient visit.

Pseudomonas aeruginosa: resistance and therapeutic options at the turn of the new millennium

Pseudomonas aeruginosa is a major cause of nosocomial infections. This organism shows a remarkable capacity to resist antibiotics, either intrinsically (because of constitutive expression of beta-lactamases and efflux pumps, combined with low permeability of the outer-membrane) or following acquisition of resistance genes (e.g., genes for beta-lactamases, or enzymes inactivating aminoglycosides or modifying their target), over-expression of efflux pumps, decreased expression of porins, or mutations in quinolone targets. Worryingly, these mechanisms are often present simultaneously, thereby conferring multiresistant phenotypes. Susceptibility testing is therefore crucial in clinical practice. Empirical treatment usually involves combination therapy, selected on the basis of known local epidemiology (usually a beta-lactam plus an aminoglycoside or a fluoroquinolone). However, therapy should be simplified as soon as possible, based on susceptibility data and the patient's clinical evolution. Alternative drugs (e.g., colistin) have proven useful against multiresistant strains, but innovative therapeutic options for the future remain scarce, while attempts to develop vaccines have been unsuccessful to date. Among broad-spectrum antibiotics in development, ceftobiprole, sitafloxacin and doripenem show interesting in-vitro activity, although the first two molecules have been evaluated in clinics only against Gram-positive organisms. Doripenem has received a fast track designation from the US Food and Drug Administration for the treatment of nosocomial pneumonia. Pump inhibitors are undergoing phase I trials in cystic fibrosis patients. Therefore, selecting appropriate antibiotics and optimising their use on the basis of pharmacodynamic concepts currently remains the best way of coping with pseudomonal infections.

Mucoviscidose : le kinésithérapeute face au risque infectieux

INTRODUCTION

Respiratory infections play a deleterious role in the progression of patients suffering from cystic fibrosis. Cross infections and epidemics have been documented in these patients, justifying a rigorous prevention regime.

BACKGROUND

This prevention regime concerns all health workers and rests on various recommendations. Segregation of patients and hand hygiene are important factors. Respiratory equipment and, more specifically, nebulisers represent a potential source of bacterial contamination requiring special attention. In the same perspective the risks related to the health care environment, particularly the lung function laboratory, should not be ignored. The modalities of prevention sometimes have a significant psychological impact that may often be reduced by careful explanation.

CONCLUSIONS

In view of the time spent in contact with these patients the physiotherapists are naturally involved in this prevention regime which is an integral part of their treatment.

Early rise of anti-Pseudomonas antibodies and a mucoid phenotype of Pseudomonas aeruginosa are risk factors for development of chronic lung infection—A case control study

P. aeruginosa is the most significant pathogen in CF lung disease. Chronic infection is preceded by a period of intermittent colonization. Early aggressive antimicrobial treatment at initial detection of P. aeruginosa in lower respiratory tract (LRT) secretions can prevent transition to chronic infection in approximately 80% of the patients, while the rest progress to chronic infection in spite of treatment. To analyze risk factors for development of chronic infection, a cohort of 89 CF patients free of chronic infection at the study period start was followed for 10 years. 28 of the patients (study group) developed chronic infection in spite of early treatment and 28 age-matched patients who did not (controls) were included in the analysis. During the 3 years period prior to onset of chronic infection, P. aeruginosa-positive cultures were more frequent in the study group than in the controls (2.2 vs. 0.5 per year, p<0.0001). Growth of mucoid strains of P. aeruginosa was more frequent in study group than in controls (11.5% vs. 0%, p<0.0001). Most important, specific anti-pseudomonal IgG serum antibodies were significantly higher in the study group than in controls (0.98 Elisa Units vs. 0.53, p=0.04) already 3 years prior to onset of chronic infection and increased 0.44 EU pr year in the study group but remained at the initial level in the control group (p<0.005). Occurrence of Aspergillus-positive cultures were significantly more frequent in the study group than in controls (p=0.01). The strongest risk factor for development of chronic P. aeruginosa infection was increasing levels of specific anti-pseudomonal antibodies, specifically of IgG1 and IgG4 subclass and total anti-Pseudomonas IgG, 3 years prior to onset of chronic infection, with odds ratio (OR) 8.9, 7.7 and 7.4, respectively (p<0.005), and growth of mucoid P. aeruginosa strains with OR of 7.4, p=0.006). Occurrence of Aspergillus was also a risk factor for developing chronic P. aeruginosa infection with the OR of 4.7 (p=0.008).

Molecular epidemiology of Pseudomonas aeruginosa, Burkholderia cepacia complex and methicillin-resistant Staphylococcus aureus in a cystic fibrosis center

Chronic pulmonary infections caused by Pseudomonas aeruginosa, Burkholderia cepacia complex and Staphylococcus aureus are responsible for most of the morbidity and mortality of patients with cystic fibrosis (CF). Little is known about the routes of transmission of these pathogens from environmental or hospital sources to the patients. We hypothesised that strains of P. aeruginosa, B. cepacia complex and methicillin-resistant S. aureus (MRSA) are nosocomially acquired by CF patients. Bacterial isolates were obtained from 164 patients attending the CF Centre of Florence and from the hospital environment and the strains typed using restriction enzymes and pulsed-field gel electrophoresis (PFGE). Seventy (43%) of patients were colonised by P. aeruginosa, 6 (3.6%) by B. cepacia complex, and 11 (7%) by MRSA. Three P. aeruginosa strains were isolated from the sinks of the ward. All the MRSA isolates differed from each other. The analysis of 83 P. aeruginosa strains showed identical genotypes in five pairs of patients, whereas from the six patients infected with B. cepacia complex strains, two patients harboured identical genotypes. These pairs of patients had no contact with each other outside the CF centre and P. aeruginosa genotypes from the hospital environment differed from these clinical isolates, suggesting a possible common source of infection within or outside the centre. The study showed that, despite isolation precautions, a minimal risk of cross-infection still existed in the CF centre and that hygienic standards should be increased to further reduce this risk.

Early intervention and prevention of lung disease in cystic fibrosis: a European consensus

In patients with cystic fibrosis (CF), early intervention and prevention of lung disease is of paramount importance. Principles to achieve this aim include early diagnosis of CF, regular monitoring of the clinical status, various hygienic measures to prevent infection and cross-infection, early use of antibiotic courses in patients with recurrent or continuous bacterial colonisation and appropriate use of chest physiotherapy.

Infection control in cystic fibrosis

Over the past 20 years there has been a greater interest in infection control in cystic fibrosis (CF) as patient-to-patient transmission of pathogens has been increasingly demonstrated in this unique patient population. The CF Foundation sponsored a consensus conference to craft recommendations for infection control practices for CF care providers. This review provides a summary of the literature addressing infection control in CF. Burkholderia cepacia complex, Pseudomonas aeruginosa, and Staphylococcus aureus have all been shown to spread between patients with CF. Standard precautions, transmission-based precautions including contact and droplet precautions, appropriate hand hygiene for health care workers, patients, and their families, and care of respiratory tract equipment to prevent the transmission of infectious agents serve as the foundations of infection control and prevent the acquisition of potential pathogens by patients with CF. The respiratory secretions of all CF patients potentially harbor clinically and epidemiologically important microorganisms, even if they have not yet been detected in cultures from the respiratory tract. CF patients should be educated to contain their secretions and maintain a distance of >3 ft from other CF patients to avoid the transmission of potential pathogens, even if culture results are unavailable or negative. To prevent the acquisition of pathogens from respiratory therapy equipment used in health care settings as well as in the home, such equipment should be cleaned and disinfected. It will be critical to measure the dissemination, implementation, and potential impact of these guidelines to monitor changes in practice and reduction in infections.

Genotyping of Pseudomonas aeruginosa in cystic fibrosis suggests need for segregation

BACKGROUND

Emerging resistance of Pseudomonas aeruginosa within cystic fibrosis (CF) populations is attributed to antibiotic pressure and spread of transmissible strains. We describe increasing resistance of P. aeruginosa isolates, resulting in the identification of two multiresistant strains and their impact on morbidity.

METHODS

Susceptibility reports of all P. aeruginosa isolates since 1998 in our unit were reviewed. Isolates were submitted for genomic finger-printing by pulsed-field gel electrophoresis. Clinical measures and the consumption of treatment resources were compared between those harbouring resistant organisms and those with sensitive strains.

RESULTS

Analysis of 407 reports from 43 patients revealed isolation of multiresistant (MR) organisms increased during 1999. Those harbouring MR strains consumed more resources than non-MR. Strain typing showed a new 'Sheffield' strain in seven patients (100% MR), and the 'Liverpool' strain in 10 patients (40% MR). Individuals in these groups consumed significantly more resources than 23 patients with unique, susceptible strains (4% MR).

DISCUSSION

Increasing resistance in isolates of P. aeruginosa may herald the arrival of a transmissible strain in CF Units which though sometimes sensitive, may become multiply resistant and require more intensive treatment. We now segregate those with transmissible strains from each other and from those with unique strains.

Infection control recommendations for patients with cystic fibrosis: microbiology, important pathogens, and infection control practices to prevent patient-to-patient transmission

Infection Control Recommendations for Patients With Cystic Fibrosis: Microbiology, Important Pathogens, and Infection Control Practices to Prevent Patient-to-Patient Transmissionupdates, expands, and replaces the consensus statement,Microbiology and Infectious Disease in Cystic Fibrosispublished in 1994. This consensus document presents background data and evidence-based recommendations for practices that are intended to decrease the risk of transmission of respiratory pathogens among CF patients from contaminated respiratory therapy equipment or the contaminated environment and thereby reduce the burden of respiratory illness. Included are recommendations applicable in the acute care hospital, ambulatory, home care, and selected non-healthcare settings. The target audience includes all healthcare workers who provide care to CF patients. Antimicrobial management is beyond the scope of this document.

Detection of a widespread clone of Pseudomonas aeruginosa in a pediatric cystic fibrosis clinic

Cross-infection by Pseudomonas aeruginosa between unrelated patients with cystic fibrosis (CF) is believed to be uncommon. After detecting a genotypically identical strain of P. aeruginosa in five unrelated children with CF dying from severe lung disease, we determined its prevalence within a large CF clinic using pulsed-field gel electrophoresis and random amplified polymorphic DNA assays. The clinical status of P. aeruginosa-infected patients was also determined. Between September and December 1999, 152 patients, aged 3.9-20.7 years, provided sputum for culture. P. aeruginosa was detected in 118 children of mean (SD) age 13.5 (3.8) years. The genotyping techniques were concordant, showing that 65 (55%) infected patients carried an indistinguishable or closely related strain. No distinctive antibiogram or environmental reservoir was found. Patients with the clonal strain were more likely than those with unrelated isolates to have been hospitalized in the preceding 12 months for respiratory exacerbations. This study demonstrates extensive spread of a single, clonal strain of P. aeruginosa in a large pediatric CF clinic. Whether this strain is also more virulent than sporadic isolates remains to be determined. As transmissible strains could emerge elsewhere, other CF clinics may also need to consider molecular methods of surveillance for cross-infection.

Heterogeneity of Pseudomonas aeruginosa in Brazilian cystic fibrosis patients

The aim of this study was to assess the diversity and genomic variability of Pseudomonas aeruginosa isolates from cystic fibrosis (CF) patients being treated at a university hospital in Brazil. Ninety-seven isolates of P. aeruginosa from 43 CF patients were characterized by macrorestriction analysis of chromosomal DNA by pulsed-field gel electrophoresis (PFGE) and tested for susceptibility to 20 antimicrobial agents by broth microdilution. It was possible to evaluate single isolates from 20 patients and multiple isolates (two to seven) from 23 patients collected during a 22-month period. Among all of the unrelated patients, we detected only one pair of patients sharing a common strain. Among the 77 isolates from 23 patients who had multiple isolates analyzed, we identified 37 major types by PFGE, and five different colonization patterns were recognized. The isolates were susceptible to several antimicrobial agents, although consecutive isolates from the same patient may display differences in their susceptibilities. Mucoid isolates were more resistant (P < 0.001) than nonmucoid isolates to five antibiotics. Our results indicate that CF patients remain colonized by more than one strain of P. aeruginosa for long periods of time. In addition, the finding of several different genotypes in the same patient suggests that the colonizing strain may occasionally be replaced.

Typing of Pseudomonas aeruginosa strains in Norwegian cystic fibrosis patients

OBJECTIVES

Typing of Pseudomonas aeruginosa isolates from Norwegian cystic fibrosis (CF) patients with chronic Pseudomonas lung infection in order to see whether cross-infection might have occurred.

METHODS

Isolates from 60 patients were collected during the years 1994-98, and typed by pulsed field gel electrophoresis.

RESULTS

Seventy-one strains were identified. One large cluster of identical strains included 27 patients, and 13 smaller clusters of 2-4 patients were found (26 patients). Seven patients had a strain not shared by other patients (private strains). Harboring the main cluster strain was significantly associated with participation in summer camps and training courses (P = 0.004, chi-squared test). There were no associations with regular admissions to hospital (intravenous antibiotic courses) or smaller social gatherings of short duration. Small clusters and private strains were not associated with any of the risk factors. All strains were sensitive to colistin. The minimal inhibitory concentrations were generally lower in Norwegian P. aeruginosa strains compared with isolates from Danish patients.

CONCLUSIONS

Our results indicate that cross-infection with P. aeruginosa between cystic fibrosis patients has occurred.

Pseudomonas aeruginosa in cystic fibrosis: cross-infection and the need for segregation

Evidence-based reasons for segregation of patients colonized with Pseudomonas aerugionsa in the outpatient setting are unclear. To clarify local decisions, Pseudomonas genotyping of the local environment, patients and patient contacts was undertaken in 1993. The hospital environment was re-swabbed in 1997. Pseudomonas genotyping of old and new patients attending the North Staffordshire cystic fibrosis clinic has subsequently been undertaken and more recently been repeated on an annual basis to assess whether the same Pseudomonas genotypes can be found in both the environment and in patients, and whether the same Pseudomonas genotype can be transferred from one patient to another. No Pseudomonas genotype found in the local environment in 1993 or in 1997 has been found in any of our patients. Nine children attending the same special school for many years and sharing the same physiotherapy facilities showed no evidence of cross-infectivity. Except for siblings living in the same household our cross-infectivity rate is very low and where cross-infection has potentially occurred the level of contact between these patients has been minimal. This study does not support the suggestion that patients with cystic fibrosis attending the North Staffordshire clinic and colonized with Pseudomonas aeruginosa should be segregated from non-colonized patients.

Epidemiologic characterization of Pseudomonas aeruginosa in patients with cystic fibrosis

OBJECTIVE

To determine persistence and variability of colonization with Pseudomonas aeruginosa in cystic fibrosis patients over long time periods, and to look for possible cross-colonization.

METHODS

In total, 469 Pseudomonas aeruginosa isolates were obtained from 30 patients during the period from April 1994 to April 1996. The sources were mainly sputum and a few deep throat swabs. All grown strains dissimilar in macromorphology were processed separately. Typing with PFGE was carried out by contour-clamped homogeneous electric field electrophoresis. Genomic DNA was subjected to the rare-cutting restriction enzyme SpeI. For pyocin typing, the procedure described by Fyfe was applied.

RESULTS

After typing with PFGE, we observed 40 restriction profiles. Eighteen different pyocin types were found. The most frequent pyocin type was type 3, followed by types 1 and 5. Twenty-two patients were persistently colonized by one clone specific and different for each patient, and four were co-colonized by a second clone also different for each of these patients. Cross-colonization had apparently been rare in the cystic fibrosis center of Leipzig.

CONCLUSIONS

Typing with PFGE is well suited for detailed investigations of colonization with Pseudomonas aeruginosa in cystic fibrosis patients. Pyocin typing can provide additional information for epidemiologic purposes.

Prospects for the prevention and control of pseudomonal infection in children with cystic fibrosis

Most patients with cystic fibrosis (CF) experience recurrent and chronic endobronchial Pseudomonas aeruginosa infections. It is possible to prevent or delay the onset of these chronic infections in most patients with CF by eliminating cross-infection and by early aggressive antibiotic treatment of the first positive sputum culture and of subsequent intermittent colonisation. Lung tissue damage is caused by activation of the immunologically specific inflammatory defence mechanisms of the lungs, which are initiated by the antibody response and dominated by polymorphonuclear neutrophil leucocytes and their proteolytic and oxidative products. This inflammation induces a phenotypic shift from nonmucoid to mucoid, alginate-producing phenotypes of P. aeruginosa which then grow, endobronchially, as a biofilm. Such biofilms are impossible to eradicate with antibiotics. By using chronic suppressive antibiotic maintenance therapy and anti-inflammatory drugs it is however, possible to maintain the lung function of these patients for a number of years.

Pseudomonas aeruginosa cross-infection among patients with cystic fibrosis during a winter camp

Twenty-seven patients with cystic fibrosis from our Danish Cystic Fibrosis Center went to a winter camp for 1 week in November of 1990. This study is based on 22 of these patients. Prior to attending camp, 17 out of 22 patients harbored Pseudomonas aeruginosa in their sputum, but 5 patients did not. After returning from camp, all 22 patients harbored P. aeruginosa in the sputum, including the 5 patients whose sputum was free of P. aeruginosa before they went. Epidemiological typing used pulsed-field gel electrophoresis of the P. aeruginosa isolates was performed. The typing results showed that the 5 cystic fibrosis patients who were free of P. aeruginosa in their sputum prior to the winter camp had acquired P. aeruginosa isolates identical to the P. aeruginosa strains isolated from the other 17 cystic fibrosis patients. This constitutes a cross-colonization rate of 100%, the highest rate ever detected among patients with cystic fibrosis. We conclude that separate holiday camps based on the infection status of the patients with cystic fibrosis are necessary to avoid cross-infection of patients not infected with P. aeruginosa.

Enzyme polymorphism in Pseudomonas aeruginosa strains recovered from cystic fibrosis patients in France

Each of 314 strains of Pseudomonas aeruginosa recovered from 87 French cystic fibrosis (CF) patients was typed by multilocus enzyme electrophoresis to investigate the genetic diversity, the relatedness and the molecular epidemiology of strains isolated from cases of chronic pulmonary colonization. Comparison of allele profiles at 18 enzyme loci identified 17 electrophoretic types (ETs). Of the 314 isolates, 290 (92%) were either ET1 (n = 127) or ET2 (n = 163), which differed only at the shikimate dehydrogenase (SKD) locus. The mean genetic diversity (H) was 0.138. These results suggest that there is cross-colonization between patients and/or that two predominant groups of strains are able to colonize French CF patients. Sequential isolates collected from 18 patients during a period of 12-28 months were analysed to assess genomic variability and its relationship to clinical outcome. Six patients were colonized by a stable strain. For the others, double infections or changes in colonization over time were observed. No relationships were detected between the clinical outcome and the persistence of stable isolates, the emergence of transient superinfecting variants, the presence of multiple ETs or the shift of ET during the monitoring.

Pseudomonas aeruginosa and Burkholderia cepacia infection in cystic fibrosis patients treated in Toronto and Copenhagen

Differences in the course of pulmonary disease in cystic fibrosis (CF) may be altered by different treatment strategies in different CF centers. The Copenhagen clinic uses scheduled, regular and very aggressive treatment of lung infection. The Toronto clinic treats pulmonary infection with oral, inhaled, or intravenous antibiotics, and has emphasized aggressive nutritional therapy. This study compared the clinical status of CF patients treated in the two centers (Toronto, Canada, n=302, and Copenhagen, Denmark, n=214) using a cross-sectional design in terms of Pseudomonas aeruginosa (PA) and Burkholderia cepacia (BC) lung infections, pulmonary function, and levels of PA and BC precipitating antibodies (precipitins). Median ages were similar, but the age distribution was significantly different, with a higher proportion of patients under 10 and > or = 25 years in Toronto, and higher proportion of patients 11-24 years of age in Copenhagen. A higher number of female patients was observed in Copenhagen than in Toronto. Seventy-nine percent of Copenhagen patients, and 52% of Toronto patients were deltaF508 homozygous. Of all the patients, 20.1% of Copenhagen patients and 38% of Toronto patients were deltaF508 heterozygous. Ten percent of Toronto patients had two uncommon mutations. Pulmonary function and nutritional status in both groups were similar despite varying treatment strategies. The prevalence of PA was lower in Danish children and higher in Danish adults than in Canada. These differences are probably due to cohort isolation, which was introduced in Copenhagen in 1981. The prevalence of BC was higher in Toronto than in Copenhagen patients at all ages. In both centers, the number of PA and BC precipitins increased with age in patients chronically infected with PA and BC, respectively, and the number of both PA and BC precipitins rose with declining lung function. This study suggests that the clinic populations had similar pulmonary and nutritional statuses despite differing clinic antibiotic treatment strategies. Microbial colonization seemed to differ, at least in part, because of differences in cohort isolation strategies. Early, aggressive anti-pseudomonal chemotherapy may have reduced pseudomonal colonization among younger patients in Copenhagen. Future studies will be required to assess the impact of this on this cohort's outcome.

Experimental gingivitis in periodontitis-susceptible subjects

The purpose of this study was to evaluate clinical, microbiological, and gingival crevicular fluid (GCF) profiles in periodontitis-resistant and periodontitis-susceptible subjects during 4 weeks of experimental gingivitis. Experimental groups of similar ages were defined as gingivitis controls (GC; n = 10) and history of rapidly progressive periodontitis (RPP; n = 10), respectively. Prior to baseline, all subjects achieved good plaque control (plaque index (P1I) approximately 0) and gingival health (gingival index (GI) = 0), and had probing depths < or = 4 mm on experimental teeth. For 4 weeks after baseline, oral hygiene around maxillary 2nd premolar and 1st molar teeth was inhibited by a plaque guard. The plaque guard was removed weekly for GCF sampling to determine interleukin (IL)-1 beta and prostaglandin (PG)E2 amounts by ELISAs. In addition, P1I, GI, probing depth, and gingival recession measurements were made. Subgingival plaque darkfield microscopy and DNA probe analysis also were performed. Results indicated that clinical signs of inflammation, microbiological patterns and GCF profiles progressed similarly in both groups. However, plaque accumulated more rapidly in the susceptible subjects. P1I in RPP at 4 weeks was 2.1 +/- 0.1 compared to 1.5 +/- 0.2 in GC, with an incidence of P1I > of 100% versus 50%, respectively (logistic regression; p < 0.0001). Hence, the clinical, microbiological and host factors selected for this study were unrelated to previous susceptibility to periodontitis when evaluated in the experimental gingivitis model. However, the increased rate of plaque accumulation, following thorough plaque removal, in RPP patients suggests a potential factor in disease recurrence in these susceptible subjects.

Spread of beta-lactam-resistant Pseudomonas aeruginosa in a cystic fibrosis clinic

BACKGROUND

Pseudomonas aeruginosa colonisation of the airways of patients with cystic fibrosis (CF) is associated with considerable respiratory morbidity. Although segregation of colonised patients from non-colonised patients to prevent cross-infection has been recommended, there is little evidence that such cross-infection is widespread. We observed that a high proportion of children attending our CF clinic were colonised with P aeruginosa that was resistant to ceftazidime and other beta-lactam antibiotics. We used two genomic fingerprinting techniques to see whether this may have arisen from epidemic spread of a single strain.

METHODS

The prevalence of P aeruginosa colonisation and the antibiotic susceptibility of the organisms was determined from review of laboratory reports in the case-notes of 120 children with CF. Isolates were cultured from the sputum of 65 children colonised with ceftazidime-resistant P aeruginosa. Polymorphisms in total bacterial DNA from 92 isolates were analysed with two molecular fingerprinting techniques--pulsed-field gel electrophoresis after restriction enzyme digestion and assessment of flagellin gene polymorphisms by amplification of the whole gene and restriction enzyme digestion.

RESULTS

92 (76.7%) of 120 children were colonised with P aeruginosa, and 65 of the 92 harboured isolates that were resistant to ceftazidime. Only three of the 92 children had never been treated with ceftazidime. The results of the two molecular-fingerprinting techniques were concordant and showed that 55 of 65 children harboured the same epidemic strain. This strain was resistant to ceftazidime, azlocillin, and imipenem, and sensitive to tobramycin and ciprofloxacin.

INTERPRETATION

This study provides the first molecular evidence of a long-term outbreak of P aeruginosa in a CF centre. We suggest that careful surveillance of the prevalence of antibiotic resistance in CF centres should be instituted with measures to prevent cross-infection. We believe that antipseudomonal monotherapy should be considered with caution.

Typing of Pseudomonas aeruginosa strains from patients with cystic fibrosis: phenotyping versus genotyping

OBJECTIVE: To assess the discriminatory power of two genotypic and two phenotypic techniques by analysis of Pseudomonas aeruginosa sputum isolates obtained with long term intervals from 29 independent cystic fibrosis (CF) patients. METHODS: Fifty-eight strains of P. aeruginosa were subjected to serotyping and pyocin production was assessed. Arbitrarily primed polymerase chain reaction (AP PCR) and pulsed-field gel electrophoresis (PFGE) were applied in order to detect genetic polymorphisms. RESULTS: From the results of different typing techniques, it appeared that the numbers of separate types varied between 11 and 43, and the percentage of identical P. aeruginosa pairs from individual patients varied between 51% and 72%, depending on the test system used. AP PCR and PFGE displayed enhanced resolution when compared to serotyping and pyocin typing; both DNA typing techniques generated concordant results, although differences in resolution are apparent. This results in 15% discordance, which may be the result of differences in the definitions of (sub)clonal relatedness as applied for AP PCR and PFGE, respectively. CONCLUSIONS: Molecular typing techniques are superior to phenotyping where P. aeruginosa is concerned. AP PCR is a fast and useful technique for determining clonality among P. aeruginosa strains from chronically colonized CF patients. It is clear, however, that the interpretation of data and comparative analysis of PFGE and AP PCR results necessitates additional (international) standardization and the development of practical guidelines.

Source of suspected periodontal pathogens re-emerging after periodontal treatment

To clarify the source of re-emerging periodontal pathogens after treatment, we compared the ribotypes of Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, Prevotella intermedia/Prevotella nigrescens group and Campylobacter rectus before and after treatment in 7 periodontitis patients and in 6 of the spouses. The patients harbored A. actinomycetemcomitans, P. gingivalis, P. intermedia/P. nigrescens group or C. rectus in their subgingival or salivary samples before treatment. The respective bacterial species were not detected 1 month after treatment, but reappeared by 6 months later. When available, 4 random colonies of each of the 4 species were isolated from both subgingival and salivary samples at each sampling occasion, the isolates were subcultured, identified and typed applying pheno- and genotypic intraspecies characterization methods. Altogether 90 strains of A. actinomycetemcomitans, P. gingivalis, P. intermedia/P. nigrescens group and C. rectus were available from 2, 3, 2 and 4 patients, respectively. The pre- and post-treatment ribotypes of A. actinomycetemcomitans-, P. gingivalis- and P. intermedia/P. nigrescens group-isolates were identical in all respective patients. The pre- and post-treatment ribotypes of C. rectus were identical in 1 of 4 patients, whereas 2 patients harbored a previously not detected post-treatment ribotype and 1 patient harbored the initial and a previously not detected post-treatment ribotype. To study the possibility that periodontitis patients may acquire strains from the spouse after treatment, isolates of A. actinomycetemcomitans, P. gingivalis, P. intermedia/P. nigrescens group and C. rectus (n = 95) from the patients' spouses were ribotyped and compared with those of the patients. The patient exhibited his own post-treatment ribotypes, different from those of the spouse, of A. actinomycetemcomitans and P. gingivalis in 1 couple and of P. intermedia/P. nigrescens group and C. rectus in 1 couple. In the 2 patients who harbored a previously not detected post-treatment ribotype of C. rectus, one patient shared the new ribotype with the spouse, whereas the other one did not. Although an exogenous source cannot be fully ruled out, the patient's own oral flora seems to be the main source of re-emerging periodontal pathogens after treatment.

Random amplified polymorphic DNA typing of Pseudomonas aeruginosa isolates recovered from patients with cystic fibrosis

Pseudomonas aeruginosa isolates recovered from chronically colonized patients with cystic fibrosis (CF) are phenotypically different from those collected from other patients or from the environment. To assess whether alterations in motility, mucoidy, and serum susceptibility represented an adaptation to chronic infection or replacement by a new strain, sequential P. aeruginosa isolates of known phenotype collected from 20 CF patients were typed by random amplified polymorphic DNA (RAPD) analysis. A total of 35 RAPD strain types were found among 385 isolates from 20 patients, and only two patients had P. aeruginosa strains of the same RAPD fingerprint. Eight strain pairs representative of the first eight RAPD types were also analyzed by SpeI macrorestriction followed by pulsed-field gel electrophoresis (PFGE); the strain types found by both fingerprinting techniques correlated exactly. In 11 of 20 patients, the RAPD types of serial P. aeruginosa isolates remained stable despite alterations in isolate motility, colonial morphology, and lipopolysaccharide phenotype. However, in isolates collected from one CF patient, a single band change in RAPD fingerprint and CeuI PFGE profile correlated with the appearance of an RpoN mutant phenotype, suggesting that the altered phenotype may have been due to a stable genomic rearrangement. Secretion of mucoid exopolysaccharide, loss of expression of RpoN-dependent surface factors, and acquisition of a serum-susceptible phenotype in P. aeruginosa appear to evolve during chronic colonization in CF patients from specific adaptation to infection rather than from acquisition of new bacterial strains.

Genome macrorestriction analysis of sequential Pseudomonas aeruginosa isolates from bronchiectasis patients without cystic fibrosis

The respiratory tracts of bronchiectasis patients may be persistently colonized with Pseudomonas aeruginosa, despite intensive chemotherapy. The organism may undergo phenotypic changes in these patients, providing misleading typing results by conventional methods. We prospectively studied eight bronchiectasis patients without cystic fibrosis over a period of 1 year. A high microbial load of P. aeruginosa was found in 70% of sputum samples collected. Of these, 55 sequential P. aeruginosa isolates were characterized by a genotyping method, pulsed-field gel electrophoresis, to overcome the problem of differentiating the P. aeruginosa strains during chemotherapy. Genome macrorestriction fingerprinting patterns were analyzed after digestion with XbaI restriction endonuclease. Of the eight patients, six harbored a single dominant strain of P. aeruginosa, with an intrapatient macrorestriction similarity pattern range of 96 to 100%. The other two patients were infected with mixed bacterial isolates including P. aeruginosa. However, diversity was observed in the P. aeruginosa isolates from all eight patients, with a relatedness of only 55 to 65%. The study further strengthens the fact that pulsed-field gel electrophoresis can be used efficiently and effectively to differentiate P. aeruginosa strains in bronchiectasis patients without cystic fibrosis.

Distribution and transmission of Pseudomonas aeruginosa and Burkholderia cepacia in a hospital ward

Genotyping and antibiotic susceptibility testing were used to analyze Pseudomonas aeruginosa and Burkholderia cepacia strains from sink drain from 14 pediatric patients with cystic fibrosis (CF) and from hospital personnel as part of a 4 week prospective study of strain transmission in a pediatric ward. A total of 87.5% of all washbasin drains were contaminated with P. aeruginosa [10(2) to 10(5) colony forming units (CFU)/ml sink fluid], whereas B. cepacia was found only once in a sink drain. From the eight CF patients already infected with P. aeruginosa upon entering the ward, we isolated six genotypes that were identical with strains found in sink drains of the ward. Four of the 16 members of the personnel had one positive P. aeruginosa hand culture. B. cepacia was never found in patients or on personnel hands. Hand washing in contaminated sinks (> or = 10(3) CFU/ml) led to positive P. aeruginosa or B. cepacia hand cultures. P. aeruginosa or B. cepacia embedded in sputum were transmissable by hand shaking for up to 180 min, whereas both pathogens suspended in physiological saline were transmissable to other hands only up to 30 min. Genotyping of P. aeruginosa revealed strain transmission from CF patients or the environment to other patients or the personnel, as well as one transmission from the environment to a CF patient. The ability of CF sputum to prolong survival of P. aeruginosa and B. cepacia may be important for strain transmission. The results suggest that improved hygienic measures are required to prevent routes of bacterial transmission via the hands and sink drains.

Outer membrane proteins of Pseudomonas aeruginosa as vaccine candidates

We tested the ability of the recombinant outer membrane proteins of Pseudomonas aeruginosa to serve as a protective vaccine against this Gram-negative pathogen in the presence of two main pathophysiological events leading to P. aeruginosa sepsis: (i) systemic infection during immunosuppression; and (ii) bacterial translocation. A hybrid vaccine was cloned which combined the protective epitopes of outer membrane protein F (OprF) and outer membrane protein I (OprI). This vaccine proved to be highly protective against an intraperitoneal challenge with P. aeruginosa in immunosuppressed mice. Oral immunization of mice with recombinant OprI expressing Salmonella dublin, induced s-IgA antibodies in the gut mucosa against OprI. These provided protection against translocation of P. aeruginosa in an immunosuppressed mouse model. To test whether OprI is effective in man, recombinant OprI was purified and used for the immunization of human volunteers. Immunization was tolerated well, and no side effects were observed. Antibody titers against OprI were measured in 90% of the volunteers after immunization.

Comparative hygienic surveillance of contamination with pseudomonads in a cystic fibrosis ward over a 4-year period

In order to study the long-term distribution and population dynamics of Pseudomonas aeruginosa strains in a highly contaminated hospital environment, two 4-week epidemiological studies, with an interval of 4 years, were carried out in the cystic fibrosis (CF) ward of the Paediatric Clinic of the Medical School of Hannover. Out of the 1948 specimens taken, P. aeruginosa was mainly identified in those from moist, inanimate sources (200 isolates) and hospitalized CF patients (168 isolates). A correlation was established between the frequency with which P. aeruginosa-positive patients came into contact with hospital facilities and the rate of contamination of these facilities. Rooms reserved for colonized patients were more frequently contaminated with P. aeruginosa in contrast to function rooms in the same ward and the outpatient clinic. However, no direct exchange between patients' strains and the inanimate hospital environment was detected. Out of the 11 genotypes of P. aeruginosa found in 1989 and the 13 genotypes found in 1993, four genotypes were present on both occasions. The most predominant clone was found in tap-water, sinks, wash-basins and creams with an incidence of 34 and 68% in the environmental isolates. The strains seemed to have spread into the adjacent control ward during the 4-year interval. Thus, the separation of colonized and non-colonized patients was undermined through the transfer of strains from a highly contaminated environment without additional hygiene precautions.

Auxotrophic variants of Pseudomonas aeruginosa are selected from prototrophic wild-type strains in respiratory infections in patients with cystic fibrosis

Twenty-four nutritionally dependent (auxotrophic) Pseudomonas aeruginosa strains were isolated from 20 cystic fibrosis (CF) patients and tested for their amino acid requirements. Two different methods were necessary to identify the nutritional status of all isolates. Methionine was the most common single amino acid required (9 of 24 isolates), followed by leucine and arginine or ornithine. In total, a requirement for 12 different compounds or combination of compounds was demonstrated. Auxotrophic and prototrophic pairs of isolates from the same patient were compared by macrorestriction analysis of DNA in pulsed-field gel electrophoresis. Thirteen of 18 pairs analyzed presented identical restriction fragment length polymorphism profiles following digestion of DNA with XbaI. Three of the remaining pairs showed percentage similarities of 77, 91, and 98%, and the profiles of two pairs could not be compared because of the excessive degradation of their DNA. These results suggest that auxotrophic and prototrophic P. aeruginosa isolates colonizing the same CF patient constitute an isogenic group and raise the possibility that auxotrophs are selected from the prototrophic population during the course of pulmonary infection in CF patients.

Epidemiology of Pseudomonas aeruginosa infection and the role of contamination of the environment in the Danish Cystic Fibrosis Centre

In order to identify the possible reservoirs and routes of cross-infection with Pseudomonas aeruginosa, samples were collected during a six-week period in autumn 1992 from patients, their visiting parents, staff and the inanimate environment of the Danish Cystic Fibrosis (CF) Centre and from a control ward with common paediatric diseases. All the P. aeruginosa strains were phage typed and serotyped. From 240 CF patients, 310 strains of P. aeruginosa were isolated, and of these 283 (91.3%) belonged to the polyagglutinable phenotype, most often with a short phage type (31/188 or 109). P. aeruginosa was isolated from only six (0.6%) of 1000 swabs taken from the environment. These six environmental strains and 20 P. aeruginosa strains from CF patients with identical serotype and phage type were examined with pulsed field gel electrophoresis. None of the patients harboured strains similar to the environmental strains, indicating the present isolation procedure and hygienic precautions were effective in our CF centre, and prevented contamination of the environment with P. aeruginosa.

Use of ribotyping in epidemiological surveillance of nosocomial outbreaks

Over the past few years, genotypic methods based on the study of bacterial DNA polymorphism have shown high discriminatory power for strain differentiation and superiority over most phenotypic methods commonly available in the clinical microbiology laboratory. Some of the methods used, however, required either a high level of technology and sophisticated equipment (e.g., pulsed-field gel electrophoresis) or species-specific reagents of restricted availability (randomly cloned DNA probes or gene-specific probes). Because ribotyping uses a universal probe (rRNA) and is a rather simple technology, particularly since the advent of nonradioactive labelling systems, it has been widely used for strain differentiation of most bacterial species involved in nosocomial outbreaks. In vitro and in vivo stability of the markers studied has been demonstrated. Although there may be limitation to this approach, ribotyping was found to be highly discriminative, particularly for typing members of the family Enterobacteriaceae, Pseudomonas cepacia, and Xanthomonas maltophilia. In many cases, it has improved the understanding of the mechanism of nosocomial acquisition of organisms by allowing a distinction between endogenous and exogenous infections. Among exogenous infections, it has distinguished between individual and epidemic strains, thus differentiating cross-infection from independent acquisition.

Genome macrorestriction analysis of diversity and variability of Pseudomonas aeruginosa strains infecting cystic fibrosis patients

Genome macrorestriction fingerprinting with XbaI and DraI was used to analyze the relatedness of 166 Pseudomonas aeruginosa isolates collected from 31 cystic fibrosis patients over a 1- to 20-month period and to correlate their genotype with patterns of resistance to 14 antimicrobial agents. Quantitative comparison of intra- and interpatient similarities of P. aeruginosa macrorestriction patterns disclosed two discrete ranges that clearly discriminated subclonal variation (> 80% relatedness) and clonal diversity (10 to 70% relatedness). Cloning-derived mutants exhibited up to 20% divergence of genomic macrorestriction patterns during the course of chronic colonization of individual patients. Change of susceptibility to multiple antimicrobial agents developed in 50% of sequential pairs of isolates from individual patients. Only 19% of these susceptibility changes were attributable to strain substitution, while the majority (56%) of resistance changes were associated with minor genomic variations of a persistent strain. Sixty-six percent of patients harbored one strain, and 33% carried two strains. Three common strains colonized 5 (28%) of 18 patients attending a cystic fibrosis clinic, and another two strains colonized two patient pairs (31%) of 13 patients staying at a rehabilitation center, suggesting potential cross-infection in these settings. By indexing regional polymorphisms throughout the chromosome structure, macrorestriction analysis can monitor subclonal evolution of P. aeruginosa and identify isogenic resistance mutants. Quantitative macrorestriction fingerprinting enables discrimination between clonal variants and clones of distinct origins and should therefore provide a reliable tool for investigating the mode of acquisition of P. aeruginosa in cystic fibrosis patients.

Cystic fibrosis: the impact of analytical technology for genotype-phenotype studies

The generalized exocrinopathy cystic fibrosis (CF) is the most common severe genetic disease in Caucasian populations. A panel of more than 700 chromosomes from German and Turkish CF patients was screened for disease-causing mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene by chemical cleavage of mismatch, single strand conformation polymorphism, restriction analysis and direct sequencing of genomic DNA amplified by polymerase chain reaction. Besides the major 3-bp deletion, delta F508 that was found on 73% of German CF chromosomes, more than 50 other missense, nonsense, frame-shift, and splice-site mutations have already been identified. In general, a CFTR mutation is linked with a single 10-marker haplotype which indicates that in most cases a particular mutation spread from a common ancestor. The comparison of mutation genotypes with the disease phenotype emphasized the causative role of the type and localization of the CFTR mutation for clinical course and prognosis. Pancreatic status and the risk of colonization of airways with opportunistic pathogens are genetically determined. Most patients who are harbouring mutations in the nucleotide binding folds were suffering from severe CF disease. Mild or even aberrant forms of CF were observed for many missense mutations located in the putative transmembrane domains or for mutations that are expected to result in a truncated protein of half of wild-type CFTR.