Epidemiologic characterization of Pseudomonas aeruginosa in patients with cystic fibrosis

Predictive modeling of antibiotic eradication therapy success for new-onset Pseudomonas aeruginosa pulmonary infections in children with cystic fibrosis

Chronic Pseudomonas aeruginosa (Pa) lung infections are the leading cause of mortality among cystic fibrosis (CF) patients; therefore, the eradication of new-onset Pa lung infections is an important therapeutic goal that can have long-term health benefits. The use of early antibiotic eradication therapy (AET) has been shown to clear the majority of new-onset Pa infections, and it is hoped that identifying the underlying basis for AET failure will further improve treatment outcomes. Here we generated machine learning models to predict AET outcomes based on pathogen genomic data. We used a nested cross validation design, population structure control, and recursive feature selection to improve model performance and showed that incorporating population structure control was crucial for improving model interpretation and generalizability. Our best model, controlling for population structure and using only 30 recursively selected features, had an area under the curve of 0.87 for a holdout test dataset. The top-ranked features were generally associated with motility, adhesion, and biofilm formation.

Epidemiology of Clonal Pseudomonas aeruginosa Infection in a Canadian Cystic Fibrosis Population

RATIONALE

The extent of the genetic relatedness among Pseudomonas aeruginosa isolates and its impact on clinical outcomes in the cystic fibrosis (CF) population is poorly understood.

OBJECTIVES

The objectives of this study were to determine the prevalence of clonal P. aeruginosa infection in Canada and to associate P. aeruginosa genotypes with clinical outcomes.

METHODS

This was an observational study of adult and pediatric patients with CF across Canada. Isolates were typed using multilocus sequence typing. A clone was defined as sharing at least six of seven alleles. Genotyping results were associated with clinical outcomes, including forced expiratory volume in 1 second, body mass index, rate of pulmonary exacerbation, and death/transplant.

RESULTS

A total of 1,537 P. aeruginosa isolates were genotyped to 403 unique sequence types (STs) in 402 individuals with CF. Although 39% of STs were shared, most were shared only among a small number of subjects, and the majority (79%) of the genetic diversity in P. aeruginosa isolates was observed between patients. There were no significant differences in clinical outcomes according to genotype. However, patients with a dynamic, changing ST infection pattern had both a steeper decline in forced expiratory volume in 1 second (-2.9% predicted change/yr, 95% confidence interval [CI] = -3.8 to -1.9 compared with 0.4, 95% CI = -0.3 to 1.0; P < 0.001) and body mass index (-1.0 percentile change/yr, 95% CI = -1.6 to -0.3 compared with -0.1, 95% CI = -0.7 to 0.5; P = 0.047) than those with a stable infection with the same ST.

CONCLUSIONS

There was no widespread sharing of dominant clones in our CF population, and the majority of the genetic diversity in P. aeruginosa was observed between patients. Changing genotypes over time within an individual was associated with worse clinical outcomes.

UVC LED Irradiation Effectively Inactivates Aerosolized Viruses, Bacteria, and Fungi in a Chamber-Type Air Disinfection System

In this study, the possibility of inactivating viral, bacterial, and fungal aerosols in a chamber-type air disinfection system by using a UVC light-emitting-diode (LED) array was investigated and inactivation rate constants of each microorganism were calculated in fitting curves of surviving populations. UVC LED array treatment effectively inactivated viral infectivity, achieving 5-log reductions within 45 mJ/cm² for MS2, Qβ, and ϕX174 viruses. UVC LED array effectiveness in inactivating Escherichia coli O157:H7, Salmonella enterica serovar Typhimurium, Listeria monocytogenes, and Staphylococcus aureus aerosols achieved 2.5- to 4-log reductions within 1.5 to 4.6 mJ/cm² Also, 4-log reductions of Aspergillus flavus and Alternaria japonica were achieved at a dosage of 23 mJ/cm² using UVC LED array irradiation. The highest UV susceptibility, represented by the inactivation rate constant, was calculated for bacteria, followed by fungi and viruses. UVC LED, an innovative technology, can effectively inactivate microorganisms regardless of taxonomic classification and can sufficiently substitute for conventional mercury UV lamps.IMPORTANCE The United Nations Environment Programme (UNEP) convened the Minamata Convention on Mercury in 2013 to ban mercury-containing products in order to ensure human and environmental health. It will be effectuated in 2020 to discontinue use of low-pressure mercury lamps and new UV-emitting sources have to replace this conventional technology. However, the UV germicidal irradiation (UVGI) system still uses conventional UV lamps, and no research has been conducted for air disinfection using UVC LEDs. The research reported here investigated the inactivation effect of aerosolized microorganisms, including viruses, bacteria, and fungi, with an UVC LED module. The results can be utilized as a primary database to replace conventional UV lamps with UVC LEDs, a novel type of UV emitter. Implementation of UVC LED technology is truly expected to significantly reduce the extent of global mercury contamination, and this study provides important baseline data to help ensure a healthier environment and increased health for humanity.

Genotypic and phenotypic relatedness of Pseudomonas aeruginosa isolates among the major cystic fibrosis patient cohort in Italy

Background

Pseudomonas aeruginosa is the predominant pathogen associated with the decline of pulmonary function in cystic fibrosis (CF) patients. Both environment-to-host acquisition and patient-to-patient transmission have been described for P. aeruginosa infection. Epidemic clones and bacterial phenotypic adaptation to the CF lung have been recognised as independent risk factors for disease progression. So far, there is no established link between genotypic prevalence and phenotypic traits. Here, we look at the major CF patient cohort in Italy to identify shared P. aeruginosa clones and associated common phenotypic traits.

Results

A comprehensive analysis of P. aeruginosa genotypes to determine the presence of high-risk shared clones and their association to specific phenotypic traits has been performed in a major Italian CF centre. Pulsed-field gel electrophoresis (PFGE) of P. aeruginosa isolates from 338 CF subjects identified 43 profiles shared by two or more patients and 214 profiles exclusive to individual patients. There was no evidence of a P. aeruginosa outbreak, but four most prevalent pulsotypes were detected. Common phenotypic traits were recorded intra-pulsotypes, but we detected heterogeneity inter-pulsotypes. Two of the four major pulsotypes included P. aeruginosa isolates with hallmarks of adaptation to the CF airways, including loss of motility, low production of siderophore, pyocyanin and proteases, and antibiotic resistance. One of these pulsotypes grouped a high percentage of hypermutable isolates. No clear correlation between epidemiological and clinical data was found.

Conclusions

We conclude that CF patients of this cohort shared common pulsotypes, but their phenotypic heterogeneity indicates an absence of specific traits associated to P. aeruginosa genotypic prevalence.

Electronic supplementary material

The online version of this article (doi:10.1186/s12866-016-0760-1) contains supplementary material, which is available to authorized users.

Recurrent Pseudomonas aeruginosa Infection in Chronic Lung Diseases: Relapse or Reinfection?

Background

Pseudomonas aeruginosa infection is particularly associated with progressive and ultimately chronic recurrent respiratory infections in chronic obstructive pulmonary disease, bronchiectasis, chronic destroyed lung disease, and cystic fibrosis. Its treatment is also very complex because of drug resistance and recurrence.

Methods

Forty eight cultures from 18 patients with recurrent P. aeruginosa pneumonia from 1998 to 2002 were included in this study. Two or more pairs of sputum cultures were performed during 2 or more different periods of recurrences. The comparison of strains was made according to the phenotypic patterns of antibiotic resistance and chromosomal fingerprinting by pulsed field gel electrophoresis (PFGE) using the genomic DNA of P. aeruginosa from the sputum culture.

Results

Phenotypic patterns of antibiotic resistance of P. aeruginosa were not correlated with their prior antibiotic exposition. Fifteen of 18 patients (83.3%) had recurrent P. aeruginosa pneumonia caused by the strains with same PFGE pattern.

Conclusion

These data suggest that the most of the recurrent P. aeruginosa infections in chronic lung disease occurred due to the relapse of prior infections. Further investigations should be performed for assessing the molecular mechanisms of the persistent colonization and for determining how to eradicate clonal persistence of P. aeruginosa.

Unusual diversity of acquired β-lactamases in multidrug-resistant Pseudomonas aeruginosa isolates in a Mexican hospital

AIMS

To investigate the presence of extended spectrum and metallo β-lactamases (MBLs) in Pseudomonas aeruginosa isolates which are resistant to imipenem and ceftazidime that were isolated in a hospital in Mexico.

RESULTS

Pulsed-field gel electrophoresis (PFGE) revealed the presence of four clonal types among the 14 isolates. All these genes were found either alone or simultaneously in the P. aeruginosa strains in the following five different arrangements: <bla(GES-5)>; <bla(GES-5), bla(VIM-11)>; <bla(GES-5), bla(VIM-2), bla(VIM-11)>; <bla(GES-5), bla(OXA-2)>; and <bla(GES-5), bla(VIM-2), bla(VIM-11), and bla(OXA-2)>. Class 1 integrons were detected and contained the cassettes bla(GES-5) and bla(OXA-2), but not that of bla(VIM). bla(VIM) genes occurred only in the chromosome, while bla(GES-5) was located in the chromosome and in the plasmids.

CONCLUSIONS

To our knowledge, this is the first description of P. aeruginosa strains simultaneously producing the VIM-2 and VIM-11 variants, and the combination of GES-5 and MBL carbapenemases, which determines a major challenge for the clinical microbiology laboratory and a remarkable epidemiological risk for the nosocomial spread of multidrug-resistant determinants.

Post‒cataract surgery endophthalmitis outbreak caused by multidrug-resistant Pseudomonas aeruginosa

In June 2010, a severe outbreak of 13 cases of post-cataract surgery endophthalmitis caused by multidrug-resistant Pseudomonas aeruginosa occurred. Pulse-field gel electrophoresis in eye isolates found 95% genetic similarity; however, extensive environmental and carriage investigation revealed no source of infection.

Rapid single-nucleotide polymorphism-based identification of clonal Pseudomonas aeruginosa isolates from patients with cystic fibrosis by the use of real-time PCR and high-resolution melting curve analysis

Pseudomonas aeruginosa genotyping relies mainly upon DNA fingerprinting methods, which can be subjective, expensive and time-consuming. The detection of at least three different clonal P. aeruginosa strains in patients attending two cystic fibrosis (CF) centres in a single Australian city prompted the design of a non-gel-based PCR method to enable clinical microbiology laboratories to readily identify these clonal strains. We designed a detection method utilizing heat-denatured P. aeruginosa isolates and a ten-single-nucleotide polymorphism (SNP) profile. Strain differences were detected by SYBR Green-based real-time PCR and high-resolution melting curve analysis (HRM10SNP assay). Overall, 106 P. aeruginosa sputum isolates collected from 74 patients with CF, as well as five reference strains, were analysed with the HRM10SNP assay, and the results were compared with those obtained by pulsed-field gel electrophoresis (PFGE). The HRM10SNP assay accurately identified all 45 isolates as members of one of the three major clonal strains characterized by PFGE in two Brisbane CF centres (Australian epidemic strain-1, Australian epidemic strain-2 and P42) from 61 other P. aeruginosa strains from Australian CF patients and two representative overseas epidemic strain isolates. The HRM10SNP method is simple, is relatively inexpensive and can be completed in <3 h. In our setting, it could be made easily available for clinical microbiology laboratories to screen for local P. aeruginosa strains and to guide infection control policies. Further studies are needed to determine whether the HRM10SNP assay can also be modified to detect additional clonal strains that are prevalent in other CF centres.

The mutL Mutation in Pseudomonas aeruginosa Isolates Reveals Multidrug-resistant Traits and Possible Evolutionary Trends

To evaluate the genetic differences and possible evolutionary trends of clinical multidrug-resistant (MDR) strains, Pseudomonas aeruginosa isolates were characterized by pulsed-field gel electrophoresis (PFGE) and evolutionary distances were estimated. A total of 85.7% of the P. aeruginosa isolates were MDR strains. Strains with the PFGE pattern A predominated; all were susceptible to amikacin and cefepime but resistant to levofloxacin and meropenem (except strain PA45 which was sensitive to meropenem). PFGE pattern H or P strains exhibited resistance to six to eight different antibiotics. PFGE pattern I or J strains were susceptible to all antibiotics tested. Two imperfect six base-pair tandem repeats, CTGGCG and CTGGCC, were found in the mutL gene. In conclusion, MDR characteristics and PFGE profiles were clearly correlated with the mutL phylogenetic tree. This indicates that mutations in mutL might contribute to genetic stability in adaptation by changing the MDR traits. Phylogenetic analysis of mutL revealed the MDR relatedness of P. aeruginosa strains.

Prevalence and analysis of Pseudomonas aeruginosa in chinchillas

Background

Chinchillas (Chinchilla laniger) are popular as pets and are often used as laboratory animals for various studies. Pseudomonas aeruginosa is a major infectious agent that causes otitis media, pneumonia, septicaemia enteritis, and sudden death in chinchillas. This bacterium is also a leading cause of nosocomial infections in humans. To prevent propagation of P. aeruginosa infection among humans and animals, detailed characteristics of the isolates, including antibiotic susceptibility and genetic features, are needed. In this study, we surveyed P. aeruginosa distribution in chinchillas bred as pets or laboratory animals. We also characterized the isolates from these chinchillas by testing for antibiotic susceptibility and by gene analysis.

Results

P. aeruginosa was isolated from 41.8% of the 67 chinchillas included in the study. Slide agglutination and pulsed-field gel electrophoresis discriminated 5 serotypes and 7 unique patterns, respectively. For the antibiotic susceptibility test, 40.9% of isolates were susceptible to gentamicin, 77.3% to ciprofloxacin, 77.3% to imipenem, and 72.7% to ceftazidime. DNA analyses confirmed that none of the isolates contained the gene encoding extended-spectrum β-lactamases; however, 2 of the total 23 isolates were found to have a gene similar to the pilL gene that has been identified in the pathogenicity island of a clinical isolate of P. aeruginosa.

Conclusions

P. aeruginosa is widely spread in chinchillas, including strains with reduced susceptibility to the antibiotics and highly virulent strains. The periodic monitoring should be performed to help prevent the propagation of this pathogen and reduce the risk of infection from chinchillas to humans.

Effect of mutator P. aeruginosa on antibiotic resistance acquisition and respiratory function in cystic fibrosis

BACKGROUND

Cystic fibrosis patients suffer from recurrent bacterial infections that result in progressive deterioration of their respiratory function. Despite intensive antibiotic treatment, Pseudomonas aeruginosa is the main cause of such infections, with clones progressively developing multiple antibiotic resistance. We determined the relationship between the presence of P. aeruginosa mutator strains and cystic fibrosis clinical characteristics.

METHODS

We analyzed 136 strains of P. aeruginosa isolated from the expectorations of 36 CF patients. On all strains, mutation frequencies were determined by the mutation rate to rifampicin, and antibiotic susceptibility was determined by the disk diffusion method. The epidemiological relatedness of these 136 P. aeruginosa strains was studied by pulsed-field gel electrophoresis. The appearance of new antibiotic resistance by sequential analysis of genotypically identical strains was determined. Lung function test results, that is, forced expiratory volume in 1 sec and vital capacity, were also recorded from these patients.

RESULTS

We showed that bacteria with an enhanced mutation rate increase the rate of acquisition of new antibiotic resistance threefold and are associated with the deterioration of lung function.

CONCLUSIONS

This study demonstrates the effect of mutator bacteria on the efficiency of patient treatment and on their respiratory function. Given the consequence of antibiotic treatment failure and lung deterioration on the prognosis of CF patients, antibiotic treatment strategies may need to be optimized to prevent the emergence of mutator clones.

Epidemiology of metalloenzyme-producing Pseudomonas aeruginosa in a tertiary hospital in Greece

A total of 132 infections of Pseudomonas aeruginosa (including 112 imipenem resistant, 32 of them producing VIM-2 beta-lactamase) were identified during a one-year period (June 2002-June 2003). PFGE molecular typing revealed that P. aeruginosa clinical isolates sensitive to imipenem, P. aeruginosa isolates resistant to imipenem but VIM-negative, and P. aeruginosa-resistant and VIM-positive isolates could be allocated to three different clusters with approximately 70% similarity. A case control study of patients infected with an MBL-producing imipenem-resistant P. aeruginosa isolate and controls (patients hospitalized in the same time period with no infection), revealed that only the number of catheters present at the time of the infection was strongly associated with the development of infection due to VIM-producing P. aeruginosa (OR 4.83, 95% CI: 1.94-12.0). In conclusion, the results of the molecular typing combined with the results of the case control study indicate that in the specific hospital setting, infection control, addressed specifically to critically ill patients, is an important part of any strategy to reduce imipenem-resistant infections.

Bacterial contamination in the environment of hospitalised children with cystic fibrosis

Pathogenic bacterial colonisation in Cystic Fibrosis patients is associated with a poor prognosis; thus, protective measures need to be taken to prevent their transmission. We studied the extent of contamination in the environment of hospitalised children with cystic fibrosis (CF) associated with specific activities. We assessed the levels of bacterial contamination in 432 air and surface samples collected from various locations in our CF centre over a three-month period: the bedrooms, corridor, communal showers, school, leisure centre and the respiratory functional explorations (RFE) unit. Staphylococcus aureus and Pseudomonas aeruginosa strains found in bedrooms and the RFE were compared with those found in patient expectorations using pulsed field gel electrophoresis. In all sampling locations, there were high levels of airborne contamination just after the presence of patients or nursing staff. In the bedrooms, the amount of S. aureus or P. aeruginosa in the air, at wake-up and after physiotherapy, were significantly higher than that after the bedroom had been cleaned. For P. aeruginosa, 33% of isolates were multiresistant to antibiotics; 50% of the colonised patients had the same P. aeruginosa strain in their sputum as in air taken from their bedroom. P. aeruginosa was detected in 23% of samples taken from the surfaces in the showers after patient washing. Very low levels of pathogenic bacteria were found in samples from the other locations. Overall, activities with the highest risk of contamination in the CF ward are physiotherapy and washing in the communal shower room. We therefore recommend to open windows after physiotherapy and to implement a strong decontamination after showers.

The current state of multidrug-resistant gram-negative bacilli in North America

Although much of today's media focuses on multidrug-resistant gram-positive bacteria such as methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococcus, resistance within gram-negative bacilli continues to rise, occasionally creating situations in which few or no antibiotics that retain activity are available. Extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli and Klebsiella sp are emerging threats nationally. Although carbapenems are considered the antibiotic class of choice to treat ESBL-producing Enterobacteriaceae, the ability of these organisms to produce carbapenemases has now become apparent in some regions throughout the United States. Although still rare, Klebsiella sp that produce KPC-2 retain susceptibility only to tigecycline, polymyxins, and occasionally aminoglycosides. Multidrug resistance among Pseudomonas aeruginosa and Acinetobacter sp has always been apparent across many hospitals in the United States. Recent surveillance indicates increasing resistance to all currently available antibiotics, including carbapenems, cephalosporins, penicillins, fluoroquinolones, and aminoglycosides. Against many strains, only polymyxins retain activity; however, resistance has also been reported to these agents. Fortunately, resistance mechanisms such as metallo-beta-lactamases are still rare in the United States. As no new antibiotics with novel mechanisms against many of these gram-negative bacilli are expected to be developed in the foreseeable future, careful and conservative use of agents combined with good infection control practices is required.

Molecular typing of clinical isolates of Stenotrophomonas maltophilia by pulsed-field gel electrophoresis and random primer PCR fingerprinting

During a 1-year study period, 96 strains of Stenotrophomonas maltophilia were isolated from different specimens of 59 patients admitted to a 1500 bed tertiary care university hospital. The strains were identified by commercially available API system and genotyped by pulsed-field gel electrophoresis (PFGE) and random primer PCR fingerprinting. The wide variation of the molecular profiles of the investigated S. maltophilia isolates shown by PFGE as well as PCR typing suggests that there was no outbreak situation with a particular S. maltophilia strain.

Phenotypic and genotypic characterization of Pseudomonas aeruginosa strains isolated from mastitis outbreaks in dairy herds

During 1998-2002 outbreaks of Pseudomonas sp. mastitis among more than 15 Israeli sheep and goat dairy herds were observed. The animals presented a wide spectrum of clinical signs ranging from subclinical to gangrenous udder. Ninety-five isolates of Pseudomonas sp. were isolated from clinical and subclinical mastitis of 47 sheep, 17 goats and 31 cows from 34 different farms. Biochemical and genetic analyses revealed that the all-causative organism was Ps. aeruginosa. Selections of isolates were further analysed on the bases of colony morphology, biochemical traits and capacity to form biofilm. All the strains displayed a wide heterogeneity in all the tested traits. No association between bacterial isolates, farm of origin and type of animal was found. Pulsed-field gel electrophoresis and cluster analysis showed no clonality among the tested strains. The present study revealed that a large variety of Ps. aeruginosa strains may cause mastitis outbreaks in sheep, goat and cattle in Israel.

Bacteriological quality of drinking water from dispensers (coolers) and possible control measures

Three water dispensers (coolers) were bacteriologically monitored over a period of 3 months to evaluate their hygienic status. For this purpose, 174 samples of chilled and unchilled water were analyzed for levels of mesophilic aerobic bacteria and the presence of Escherichia coli and enterococci in 100-ml samples, and the presence of Pseudomonas aeruginosa in 10- and 100-ml samples. Additionally, 12 samples from 20-liter plastic bottles of spring water used to supply the coolers and 36 samples of 12 different brands of noncarbonated bottled mineral water were similarly analyzed. Water from the coolers yielded aerobic plate counts of 3 to 5 log CFU/ml with a geometric mean of 3.86 log CFU/ml, whereas water from the 20-liter bottles had a mean aerobic plate count of 3.3 log CFU/ml. Aerobic plate counts for noncarbonated mineral waters were generally lower (13 samples, < 10 CFU/ml; 6 samples, 10 to 10(2) CFU/ml; 13 samples, 10(2) to 10(3) CFU/ml; 3 samples, 10(3) to 10(4) CFU/ ml; 1 sample, 2 x 10(4) CFU/ml). Although occasional professional cleaning of the coolers did not affect the aerobic plate count, P. aeruginosa was successfully eliminated 2 weeks after cleaning, with only one cooler becoming recolonized. Neither E. coli nor enterococci was found in any of the water samples tested. However, P. aeruginosa was identified in three (25%) of twelve 100-ml samples from 20-liter bottles of spring water; a similar frequency of 24.1% was seen for water samples from coolers. Overall, 35 (21.6%) of 162 water samples (10 ml) from coolers also yielded P. aeruginosa, suggesting potential growth of P. aeruginosa in the dispensers. Pulsed-field gel electrophoresis typing and antibiotic susceptibility testing found 19 P. aeruginosa isolates from the coolers and bottles to be identical, indicating that a single strain originated from the bottled water rather than the surroundings of the coolers. Because P. aeruginosa can cause serious nosocomial infections, its spread should be strictly controlled in institutions caring for vulnerable people such as hospitals and nursing homes. Consequently, in keeping with legal requirement for bottled spring and mineral water in Switzerland, it is also advisable that P. aeruginosa be absent in 100-ml samples of cooler water.

Molecular epidemiology of metallo-beta-lactamase-producing Pseudomonas aeruginosa in the Calgary Health Region: emergence of VIM-2-producing isolates

A study was designed to describe the molecular epidemiology of carbapenem-resistant (CR) Pseudomonas aeruginosa in a large well-defined geographical region with a centralized laboratory system serving one pediatric and three large adult hospitals (acute care centers I, II, and III). Molecular characterization was done using PCR with sequencing of the integron-associated gene cassettes. Pulsed-field gel electrophoresis (PFGE) using a modified combined Stenotrophomas maltophilia and Streptococcus pneumoniae protocol with SpeI was performed on CR P. aeruginosa strains isolated in the Calgary Health Region during 2002-2006. The majority (96%) of metallo-beta-lactamase (MBL)-producing isolates produced VIM-2 with gene cassettes aacC1 and aacA4, while 4% produced IMP-7 with gene cassettes aacC4 and aacC1. Eighty-six percent of VIM-2 producers belonged to a cluster (MBLV) that was responsible for nosocomial outbreaks during 2003 (intensive care unit) and 2004 (bone marrow transplant unit) at acute care center I. Environmental isolates from these units also belonged to MBLV. The majority of strains from cluster MBLVR (related to MBLV) were present in acute care center III. Isolates producing IMP-7 belonged to a different cluster (MBLI) and were related to strains described during the 1990 s. PFGE of the MBL-negative CR strains showed that 37% belonged to a closely related cluster, NMBL, whose members were predominantly isolated from acute care center II. Our findings suggest that CR and dissemination of MBL clusters among P. aeruginosa populations in large geographic healthcare regions are dynamic processes that require continuous molecular surveillance.

Antimicrobial therapy for pulmonary pathogenic colonisation and infection by Pseudomonas aeruginosa in cystic fibrosis patients

Pseudomonas aeruginosa colonisation has a negative effect on pulmonary function in cystic fibrosis patients. The organism can only be eradicated in the early stage of colonisation, while reduction of bacterial density is desirable during chronic colonisation or exacerbations. Monthly, or at least 3-monthly, microbiological culture is advisable for patients without previous evidence of P. aeruginosa colonisation. Cultures should be performed at least every 2-3 months in patients with well-established colonisation, and always during exacerbations or hospitalisations. Treatment of patients following the first isolation of P. aeruginosa, but with no clinical signs of colonisation, should be with oral ciprofloxacin (15-20 mg/kg twice-daily for 3-4 weeks) plus inhaled tobramycin or colistin (intravenous treatment with or without inhaled treatment can be used as an alternative), while patients with acute infection should be treated for 14-21 days with high doses of two intravenous antimicrobial agents, with or without an inhaled treatment during or at the end of the intravenous treatment. Maintenance treatment after development of chronic P. aeruginosa infection/colonisation (pathogenic colonisation) in stable patients (aged>6 years) should be with inhaled tobramycin (300 mg twice-daily) in 28-day cycles (on-off) or, as an alternative, colistin (1-3 million units twice-daily). Colistin is also a possible choice for patients aged<6 years. Treatment can be completed with oral ciprofloxacin (3-4 weeks every 3-4 months) for patients with mild pulmonary symptoms, or intravenously (every 3-4 months) for those with severe symptoms or isolates with ciprofloxacin resistance. Moderate and serious exacerbations can be treated with intravenous ceftazidime (50-70 mg/kg three-times-daily) or cefepime (50 mg/kg three-times-daily) plus tobramycin (5-10 mg/kg every 24 h) or amikacin (20-30 mg/kg every 24 h) for 2-3 weeks. Oral ciprofloxacin is recommended for patients with mild pulmonary disease. If multiresistant P. aeruginosa is isolated, antimicrobial agents that retain activity are recommended and epidemiological control measures should be established.

Prevalence of Pseudomonas aeruginosa in households of patients with cystic fibrosis

Colonization of airways with Pseudomonas aeruginosa (PA) is known to be a risk factor for infection and adverse clinical outcome in patients with cystic fibrosis (CF). Whereas infections with PA have been linked to contaminated medical devices in hospitals, sources of colonization and infection with PA in households of patients with CF remain to be identified. Using a standardized sampling protocol, we prospectively examined the presence of PA in 102 households of patients with CF in Germany. PA was detected in 73 (71.6%) of 102 households. PA was detected most frequently in drains of showers (39.6%), drainpipes of hand-basins in kitchens (35.0%) and bathrooms (34.7%), and drainpipes of toilets (26.5%). Toilet seats and dish-clothes did not show PA in any household. The frequency and intensity of cleaning measures did not impact the detection rate of PA. Results of the present study for the first time determinate the rate of contamination with PA in households of patients with CF. Future studies will determine the risk of transmission of PA from households locations to patients with CF.

Genetic and biochemical characterization of PrtA, an RTX-like metalloprotease from Photorhabdus

Proteases play a key role in the interaction between pathogens and their hosts. The bacterial entomopathogen Photorhabdus lives in symbiosis with nematodes that invade insects. Following entry into the insect, the bacteria are released from the nematode gut into the open blood system of the insect. Here they secrete factors which kill the host and also convert the host tissues into food for the replicating bacteria and nematodes. One of the secreted proteins is PrtA, which is shown here to be a repeats-in-toxin (RTX) alkaline zinc metalloprotease. PrtA has high affinity for artificial substrates such as casein and gelatin and can be inhibited by zinc metalloprotease inhibitors. The metalloprotease also shows a calcium- and temperature-dependent autolysis. The prtA gene carries the characteristic RTX repeated motifs and predicts high similarity to proteases from Erwinia chrysanthemi, Pseudomonas aeruginosa and Serratia marcescens. The prtA gene resides in a locus encoding both the protease ABC transporter (prtBCD) and an intervening ORF encoding a protease inhibitor (inh). PrtA activity is detectable 24 h after artificial bacterial infection of an insect, suggesting that the protease may play a key role in degrading insect tissues rather than in overcoming the insect immune system. Purified PrtA also shows cytotoxicity to mammalian cell cultures, supporting its proposed role in bioconversion of the insect cadaver into food for bacterial and nematode development.

Development of resistance in Pseudomonas aeruginosa obtained from patients with cystic fibrosis at different times

OBJECTIVE

Determination of the extent of changes in quantitative resistance in Pseudomonas aeruginosa isolates from patients with cystic fibrosis over a period of approximately 2 years.

METHODS

Three hundred and ninety nine isolates of P. aeruginosa collected from 34 pediatric patients in the period between April 1994 and April 1996 were investigated. During the 2 years the children were treated with a combination of a betalactam and an aminoglycoside, approximately every 3 months. In between they received ciprofloxacin orally, when required. The minimal inhibitory concentrations (MICs) of 38 clones of P. aeruginosa defined by different patterns in macrorestriction analysis (pulse field gel electrophoresis, PFGE) were established for 12 antibiotics: gentamicin, amikacin, tobramycin, ciprofloxacin, levofloxacin, moxifloxacin, trovafloxacin, imipenem, meropenem, ceftazidime, cefepime, and piperacillin by means of broth microdilution tests according to DIN 58940.

RESULTS

Twenty-four of the 38 clones developed increased MIC values during the time of observation especially for aminoglycosides and quinolones. Comparatively less affected were ceftazidime, imipenem and meropenem. An association between the number of the intravenous treatment courses and the increase of the MIC values could not be verified.

CONCLUSIONS

A trend towards an increase of the MICs against antipseudomonal agents was observed over a limited period of time. It is necessary to prevent this development possibly by employing suitable combinations of antibiotics and the introduction of new substances.

Plant lectin-like bacteriocin from a rhizosphere-colonizing Pseudomonas isolate

Rhizosphere isolate Pseudomonas sp. strain BW11M1, which belongs to the Pseudomonas putida cluster, secretes a heat- and protease-sensitive bacteriocin which kills P. putida GR12-2R3. The production of this bacteriocin is enhanced by DNA-damaging treatment of producer cells. We isolated a TnMod mutant of strain BW11M1 that had lost the capacity to inhibit the growth of strain GR12-2R3. A wild-type genomic fragment encompassing the transposon insertion site was shown to confer the bacteriocin phenotype when it was introduced into Escherichia coli cells. The bacteriocin structural gene was identified by defining the minimal region required for expression in E. coli. This gene was designated llpA (lectin-like putidacin) on the basis of significant homology of its 276-amino-acid product with mannose-binding lectins from monocotyledonous plants. LlpA is composed of two monocot mannose-binding lectin (MMBL) domains. Several uncharacterized bacterial genes encoding diverse proteins containing one or two MMBL domains were identified. A phylogenetic analysis of the MMBL domains present in eukaryotic and prokaryotic proteins assigned the putidacin domains to a new bacterial clade within the MMBL-containing protein family. Heterologous expression of the llpA gene also conveyed bacteriocin production to several Pseudomonas fluorescens strains. In addition, we demonstrated that strain BW11M1 and heterologous hosts secrete LlpA into the growth medium without requiring a cleavable signal sequence. Most likely, the mode of action of this lectin-like bacteriocin is different from the modes of action of previously described Pseudomonas bacteriocins.

Epidemiology of Pseudomonas aeruginosa in cystic fibrosis in British Columbia, Canada

Pseudomonas aeruginosa is the most common respiratory pathogen in patients with cystic fibrosis (CF), but the predominant mechanism by which it is acquired is controversial. To determine the frequency of patient-to-patient spread, we evaluated P. aeruginosa isolates from 174 patients treated at the CF clinics in Vancouver, BC, Canada, since 1981. Multiple isolates were obtained from each patient and genetically typed by random amplified polymorphic DNA and pulsed field gel electrophoresis analyses. A total of 157 genetic types of P. aeruginosa was identified, 123 of which were unique to individual patients. A total of 34 types was shared by more than one patient; epidemiologic evidence linked these individuals only in the cases of 10 sibships and 1 pair of unrelated patients. We conclude that there is an extremely low risk in Vancouver for patients with CF to acquire P. aeruginosa from other patients. It appears that prolonged close contact, such as occurs between siblings, is necessary for patient-to-patient spread. The major source of acquisition of P. aeruginosa in CF appears to be from the environment. Considering these observations, we do not recommend segregation of patients with CF on the basis of their colonization status with P. aeruginosa.

Spread of a multiresistant strain of Pseudomonas aeruginosa in an adult cystic fibrosis clinic

We initiated a prospective surveillance study to investigate possible Pseudomonas aeruginosa cross-infection in our cystic fibrosis centre. We characterised isolates by pyocin typing and pulsed-field gel electrophoresis. 22 (14%) of 154 patients with chronic P aeruginosa had isolates with similar and new pyocin and pulsed-field gel electrophoresis types. The shared isolates showed unusual phenotypic features: they were non-pigmented, non-motile, and resistant to a number of antipseudomonal antibiotics. Cross-infection by a multiresistant P aeruginosa strain has therefore occurred in patients attending our cystic fibrosis centre. We recommend microbiological surveillance in other cystic fibrosis centres.