Microbiology of airway disease in patients with cystic fibrosis

Cystic fibrosis: a polymicrobial infectious disease

Cystic fibrosis (CF) is the most common lethal genetic disease in the Caucasian population, and should be considered an infectious disease because of the basic pathophysiology. Chronic lower airway infections cause a progressive pathologic deterioration of lung tissue, a decline in pulmonary function and, ultimately, respiratory failure and death in 90% of CF patients. Historically, very few bacterial species have been implicated as principal CF pathogens. However, molecular evidence suggests the presence of a diverse mosaic of bacteria in CF lungs, and infections can be defined as polymicrobial. Here we review the work that supports this concept and we discuss the potential significance of the polymicrobial community in lung pathology. Understanding the dynamics of polymicrobial infections, the interplay between pathogen(s), normal oropharyngeal flora and the host immune system may lead to future advances in the therapeutic management of chronic lung infections.

The ArcA regulon and oxidative stress resistance in Haemophilus influenzae

Haemophilus influenzae transits between niches within the human host that are predicted to differ in oxygen levels. The ArcAB two-component signal transduction system controls gene expression in response to respiratory conditions of growth and has been implicated in bacterial pathogenesis, yet the mechanism is not understood. We undertook a genome-scale study to identify genes of the H. influenzae ArcA regulon. Deletion of arcA resulted in increased anaerobic expression of genes of the respiratory chain and of H. influenzae's partial tricarboxylic acid cycle, and decreased anaerobic expression levels of genes of polyamine metabolism, and iron sequestration. Deletion of arcA also conferred a susceptibility to transient exposure to hydrogen peroxide that was greater following anaerobic growth than after aerobic growth. Array data revealed that the dps gene, not previously assigned to the ArcA modulon in bacteria, exhibited decreased expression in the arcA mutant. Deletion of dps resulted in hydrogen peroxide sensitivity and complementation restored resistance, providing insight into the previously uncharacterized mechanism of arcA-mediated H(2)O(2) resistance. The results indicate a role for H. influenzae arcA and dps in pre-emptive defence against transitions from growth in low oxygen environments to aerobic exposure to hydrogen peroxide, an antibacterial oxidant produced by phagocytes during infection.

Evaluation of the E test for the assessment of synergy of antibiotic combinations against multiresistant Pseudomonas aeruginosa isolates from cystic fibrosis patients

The determination of synergistic effects of antimicrobial drug combinations can lead to improved therapeutic options in the antibiotic treatment of cystic fibrosis patients who are chronically infected with multiresistant Pseudomonas aeruginosa isolates. The aim of this study was to evaluate the performance of the E test versus the standard agar dilution checkerboard susceptibility test in the assessment of synergy and, in addition, to determine the activity of two antimicrobial combinations against 163 multiresistant P. aeruginosa isolates from cystic fibrosis patients. The agreement between the checkerboard method and the E test was excellent (>90%) for nonmucoid as well as mucoid isolates from cystic fibrosis patients. The rate of synergy was higher for the antibiotic combination of ceftazidime and tobramycin (28.8% of the cystic fibrosis strains) than for the combination of meropenem and tobramycin (19.0%). However, the probability of synergy for the second antibiotic combination increased significantly when the synergy of the first antibiotic combination had already been demonstrated (Fischer's exact test, p=0.049). The results show that the E test is a valuable and practical method for routine microbiological diagnostics and can aid in the selection of improved antibiotic options in the treatment of cystic fibrosis patients chronically infected with P. aeruginosa.

16S rRNA gene microbial analysis of the skin of fleece rot resistant and susceptible sheep

Fleece rot is a bacterial dermatitis that follows prolonged wetting of the sheep’s skin, and a major pre-disposing condition to body strike in the Australian Merino. Several studies have examined bacterial load of the fleece in relation to fleece rot using traditional culture-based techniques focussing on only a few bacterial species. We examined the natural bacterial diversity of the healthy sheep skin and changes that occurred in fleece-rot resistant and susceptible animals during fleece rot development. Presented is a preliminary molecular genetic analysis of the bacterial ecology of the sheep skin. Eight 16S rRNA gene libraries were constructed from susceptible and resistant sheep both before and after onset of the disease following induction by simulated rainfall. Approximately 75% of the sequences obtained in this study have not been previously identified in fleece-rot studies. Four operational taxonomic units (OTU; groups of >97% sequence similarity) of major interest were present on susceptible animals and absent from resistant animals. Data on these OTU expand current knowledge of bacteria involved in inflammation and wounding of sheep skin tissue, and provide direction for future research that may lead to new treatment options for fleece rot and body strike.

Evaluation of pyrrolidonyl arylamidase for the identification of nonfermenting Gram-negative rods

To evaluate the activity of pyrrolidonyl arylamidase (PYR) for the differentiation and identification of nonfermenting gram negative rods (NFGNR), 293 isolates were tested. A 24 h culture of each test organism was prepared. From this a 108-109 cfu/mL suspension was added to 0.25 mL of sterile physiologic solution. A PYR disk was then added and the test was incubated for 30 minutes at 35-37 degrees C, at environmental atmosphere. Reading was done by adding 1 drop of cinnamaldehyde reagent. Strains of Acinetobacter baumannii, Acinetobacter haemolyticus, Alcaligenes faecalis, Bergeyella zoohelcum, Bordetella bronchiseptica, Bordetella hinzii, Brevundimonas diminuta, Brevundimonas vesicularis, Brucella ovis, Brucella spp., Brucella suis, Burkholderia cepacia complex, Moraxella catarrhalis, Moraxella lacunata, Moraxella nonliquefaciens, Moraxella osloensis, Oligella ureolytica, Pseudomonas alcaligenes, Pseudomonas mendocina, Pseudomonas pseudoalcaligenes, Pseudomonas putida, Pseudomonas stutzeri, Pseudomonas Vb3, Psychrobacter phenylpyruvicus, and Stenotrophomonas maltophilia were PYR negative. On the other hand Achromobacter piechaudii, Achromobacter denitrificans, Achromobacter xylosoxidans, Burkholderia gladioli, Chryseobacterium gleum-indologenes, Comamonas testosroni, Cupriavidus pauculus, Delftia acidovorans, Elizabethkingia meningoseptica, Myroides spp., Ochrobactrum anthropi, Pseudomonas oryzihabitans, Ralstonia pickettii, Rhizobium radiobacter, Shewanella spp., Sphingobacterium multivorum, Sphingobacterium spiritivorum, and Weeksella virosa were PYR positive. Finally, Acinetobacter lwoffii, Pseudomonas aeruginosa, Pseudomonas fluorescens, Roseomonas spp., and Sphingomonas paucimobilis-parapaucimobilis were PYR variable. PYR testing should be considered as a useful tool to facilitate the identification of NFGNR.

Clonal analysis of Inquilinus limosus isolates from six cystic fibrosis patients and specific serum antibody response

Inquilinus limosus is a novel Gram-negative bacterium of the subdivision alpha-Proteobacteria recently found in the airways of patients with cystic fibrosis (CF). Here, the authors report on the clinical courses of six CF patients colonized with I. limosus. Five patients suffered from either an acute respiratory exacerbation or a progressive loss of pulmonary function, whereas one patient was in a stable clinical situation. This study focused on two aims: (i) the clonal analysis of I. limosus isolates by random amplified polymorphic DNA (RAPD)-PCR, and (ii) the clarification of whether the presence of I. limosus in the respiratory tract is associated with a specific serum antibody response. Serum IgG was detected by immunoblotting using I. limosus whole-cell-lysate proteins as antigens. Sera from healthy blood donors (n=10) and from CF patients colonized with Pseudomonas aeruginosa (n=10) were found to be immunoblot negative. All six Inquilinus-positive patients raised serum IgG antibodies against various I. limosus antigens. Surprisingly, in one patient, a specific I. limosus serum antibody response was already detected 1 year prior to Inquilinus-positive sputum cultures. Two prominent antigens were characterized by MALDI-MS: a 23 kDa protein revealed homology to the outer membrane lipoprotein OmlA of Actinobacillus pleuropneumoniae, and an 18 kDa protein to a protein-tyrosine phosphatase of Burkholderia cepacia. In conclusion, detection of I. limosus is accompanied by a specific serum antibody response and may reflect the infectious/pathogenic potential of I. limosus. Moreover, IgG immunoblotting may be useful to detect early infection with I. limosus and may support the selective cultivation of this novel emerging pathogen.

Delivery of photosensitisers and light through mucus: investigations into the potential use of photodynamic therapy for treatment of Pseudomonas aeruginosa cystic fibrosis pulmonary infection

Respiratory disease is the main cause of morbidity and mortality in patients with cystic fibrosis (CF). In such patients chronic Pseudomonas aeruginosa infection is virtually impossible to eradicate using antibiotic therapy. Photodynamic antimicrobial chemotherapy (PACT) could be one potential alternative antimicrobial method. As photosensitisers could be delivered to the lungs of CF patients via inhalation, the current in vitro study investigated the potential use of PACT in the treatment of P. aeruginosa CF pulmonary infection. Delivery of red light (635 nm) and two photosensitisers (toluidine blue O (TBO) and meso-tetra (N-methyl-4-pyridyl) porphine tetra tosylate (TMP)) across artificial CF mucus was successfully achieved. Artificial CF mucus reduced the measured fluence of incident light in an almost exponential manner with increasing depth. The presence of dissolved photosensitisers also reduced light fluence. TMP diffused more efficiently across artificial CF mucus than TBO. However, receiver compartment concentrations of both drugs after 6 h were of the same order as those required to achieve high rates of kill (>99%) of P. aeruginosa isolates growing both planktonically and in biofilms. TMP required significantly higher concentrations (2.5 mg ml(-1)) than TBO to achieve high rates of kill (>99%) of P. aeruginosa isolates growing planktonically. Higher concentrations (5.0 mg ml(-1)) of both photosensitisers were required to achieve high rates of kill (>99%) of P. aeruginosa isolates growing in biofilms. When photosensitisers were prepared in artificial mucus, higher concentrations were required to achieve reasonably high kill rates (>80%) of P. aeruginosa (PAO1) growing both planktonically and in biofilm.

Bacterial diversity in aortic aneurysms determined by 16S ribosomal RNA gene analysis

BACKGROUND

Aortic aneurysms are common vascular conditions that cause considerable morbidity and mortality. Understanding of the mechanisms involved in the pathogenesis of the condition remains limited. Recently, infection has been suggested as possible contributor in the development of the disease. The aim of the present study was to examine aortic aneurysms for the presence of bacterial DNA using polymerase chain reaction (PCR) targeting the 16S ribosomal RNA (rRNA) gene, followed by cloning and sequencing.

METHODS

Universal eubacterial primers were used to amplify 16S rRNA bacterial genes in 10 specimens from arterial walls of aortic aneurysms. Subsequently, PCR amplicons were cloned into Escherichia coli and sequencing of the cloned inserts was used to determine species identity or closest relatives by comparison with known sequences in GenBank.

RESULTS

Sequences of Stenotrophomonas spp., including S. maltophilia (formerly Pseudomonas homology group V) were detected in six aneurysm samples. Propionibacterium acnes was identified in five samples, and Brevundimonas diminuta (formerly P. diminuta) in four samples. Other species previously assigned to the Pseudomonas genus such as Comamonas testosteroni, Delftia acidovorans, Burkholderia cepacia, Herbaspirillum sp., and Acidovorax sp. were also detected. Some clones fell into other environmental species, including Methylobacterium sp. and Bradyrhizobium elkanii, and others represented bacteria that have not yet been cultivated. DNA sequences from oral bacteria, including Streptococcus sanguinis, Tannerella forsythia, and Leptotrichia buccalis were detected. Sequences from Prevotella melaninogenica and Lactobacillus delbrueckii, which are commonly found in both mouth and gastrointestinal tract, were also detected. Additional species included Dermacoccus spp. and Corynebacterium vitaeruminis.

CONCLUSIONS

A wide variety of bacteria, including oral bacteria, was found to colonize aortic aneurysms and may play a role in their development. Several of these microorganisms have not yet been cultivated.

CLINICAL RELEVANCE

Although Chlamydophila pneumoniae has been detected in aneurysmal walls, its exact role in the condition remains inconclusive. Overall, there is scarce information about the role of microorganisms in aneurysmal disease. In the present study, we used molecular genetics to detect a diversity of bacteria in arterial walls of aortic aneurysms. The presence of multiple microorganisms in aneurysmal disease may have implications for chemoprophylaxis and antibiotic treatment if directed only at C.pneumoniae.

Rational treatment of pulmonary infections in patients with cystic fibrosis

The life expectancy of patients with cystic fibrosis has increased markedly during the past two decades due in large part to improved clinical care, including the use of more effective antimicrobial agents for Pseudomonas. However, the chronic lung disease of CF remains the principal cause of mortality. A growing understanding of the complex interactions between infection and inflammation has led to new approaches for treatment, including chronic use of aerosolized antibiotics, particularly tobramycin, in patients known to be colonized/infected with P. aeruginosa and anti-inflammatory treatments to slow the progression of lung disease.

A napkin-associated outbreak of Burkholderia cenocepacia bacteraemia in haemodialysis patients

This article reports a catheter-related outbreak of bacteraemia involving 38 patients in two haemodialysis units in Verona. Burkholderia cepacia complex strains were isolated from human blood and from an individually wrapped disinfection napkin that was contained in a commercially available, sterile dressing kit used to handle central venous catheters. Micro-organisms isolated from blood cultures and from the napkin were identified by standard procedures and confirmed as B. cenocepacia (genomovar III) by molecular analysis. Using pulsed-field gel electrophoresis analysis, the clinical isolates were indistinguishable or closely related to the B. cenocepacia isolated from the napkin. In conclusion, this study found that a contaminated commercial napkin soaked in quaternary ammonium, even when quality certified, was the source of infection.

Pseudomonas putida KT2440 responds specifically to chlorophenoxy herbicides and their initial metabolites

Pseudomonas putida KT2440 is often used as a model to investigate toxicity mechanisms and adaptation to hazardous chemicals in bacteria. The objective of this paper was to test the impact of the chlorophenoxy herbicides 2,4-dichlorophenoxyacetic acid (2,4-D) and 2-(2,4-dichlorophenoxy)propanoic acid (DCPP) and their metabolites 2,4-dichlorophenol (DCP) and 3,5-dichlorocatechol (DCC), on protein expression patterns and physiological parameters. Both approaches showed that DCC has a different mode of action and induces different responses than DCPP, 2,4-D and DCP. DCC was the most toxic compound and was active as an uncoupler of oxidative phosphorylation. It repressed the synthesis of ferric uptake regulator (Fur)-dependent proteins, e.g. fumarase C and L-ornithine N5-oxygenase, which are involved in oxidative stress response and iron uptake. DCPP, 2,4-D and DCP were less toxic than DCC. They disturbed oxidative phosphorylation to a lesser extent by a yet unknown mechanism. Furthermore, they repressed enzymes of energy-consuming biosynthetic pathways and induced membrane transporters for organic substrates. A TolC homologue component of multidrug resistance transporters was found to be induced, which is probably involved in the removal of lipophilic compounds from membranes.

Chronic colonization with Pandoraea apista in cystic fibrosis patients determined by repetitive-element-sequence PCR

Pandoraea apista is recovered with increasing frequency from the lungs of patients with cystic fibrosis (CF) and may represent an emerging pathogen (I. M. Jorgensen et al., Pediatr. Pulmonol. 36:439-446, 2003). We identified two CF patients from our hospital whose sputum specimens were culture positive for P. apista over the course of several years. Repetitive-element-sequence PCR was employed to determine whether sequential isolates that were recovered from these patients represented a single clone and whether each patient had been chronically colonized with the same strain. Banding patterns generated with ERIC primers, REP primers, and BOX primers showed that individual patient isolates had a high degree of similarity (>97%) and were considered identical. However, only the banding patterns from the ERIC primers and BOX primers were able to show that the strains from patients I and II were unique (similarity indices of 79.8% and 70.0%, respectively). We concluded that all strains of P. apista from patient I were identical, as were all strains from patient II, establishing chronic colonization. Only two of the three methods employed indicate that the strains from the two patients are distinct. This implied that the organism was not transferred from one patient to the other, suggesting that the choice of methodology could generate misleading results when examining person-to-person transmission regarding this organism.

Airway mucus: From production to secretion

Mucus hypersecretion is a phenotype associated with multiple obstructive lung diseases. However, in spite of its nefarious reputation under pathologic conditions, there are significant benefits to having low levels of mucus present in the airways at baseline, such as the ability to trap and eliminate inhaled particles and to prevent desiccation of airway surfaces. Mucins are high-molecular-weight glycoproteins that are the chief components that render viscoelastic and gel-forming properties to mucus. Recent advances in animal models and in vitro systems have provided a wealth of information regarding the identification of the mucin genes that are expressed in the lungs, the signal transduction pathways that regulate the expression of these mucins, and the secretory pathways that mediate their release into the airways. In addition, the clinical and pathologic literature has corroborated many of the basic laboratory findings. As a result, mucin overproduction and hypersecretion are moving away from being markers of disease and toward being testable as functional components of lung disease processes.

Distribution and expression of the ZmpA metalloprotease in the Burkholderia cepacia complex

The distribution of the metalloprotease gene zmpA was determined among strains of the Burkholderia cepacia complex (Bcc). The zmpA gene was present in B. cepacia, B. cenocepacia, B. stabilis, B. ambifaria and B. pyrrocinia but absent from B. multivorans, B. vietnamiensis, B. dolosa, and B. anthina. The presence of zmpA generally correlated with extracellular proteolytic activity with the exception of five strains, which had zmpA but had no detectable proteolytic activity when skim milk agar was used as a substrate (zmpA protease deficient). Western immunoblot experiments with anti-ZmpA antibodies suggest that the zmpA protease-deficient strains do not secrete or accumulate detectable ZmpA. Transcriptional zmpA::lacZ fusions were introduced in selected strains of the Bcc. zmpA::lacZ was expressed in all strains, but expression was generally lower in the zmpA protease-deficient strains than in the zmpA protease-proficient strains. Quantitative reverse transcriptase real-time PCR demonstrated that zmpA protease-deficient strains did express zmpA mRNA, although at various levels. ZmpA has previously been shown to be positively regulated by the CepIR quorum-sensing system. Addition of exogenous AHLs did not restore extracellular protease production to any of the zmpA protease-deficient strains; however, introduction of cepR in trans complemented protease activity in two of five strains. Extracellular proteolytic activity was restored by the presence of zmpA in trans in two of the five strains. These studies suggest that although some strains of the Bcc contain the zmpA gene, multiple factors may influence its expression.

Mucin-Pseudomonas aeruginosa interactions promote biofilm formation and antibiotic resistance

Pseudomonas aeruginosa is an opportunistic pathogen that causes chronic lung infections in people suffering from cystic fibrosis (CF). In CF airways, P. aeruginosa forms surface-associated communities called biofilms. Compared with free-swimming cultures, biofilms resist clearance by the host immune system and display increased resistance to antimicrobial agents. In this study we developed a technique to coat surfaces with molecules that are abundant in CF airways in order to investigate their impact on P. aeruginosa biofilm development. We found that P. aeruginosa biofilm development proceeds differently on surfaces coated with the glycoprotein mucin compared with biofilm development on glass and surfaces coated with actin or DNA. Biofilms formed on mucin-coated surfaces developed large cellular aggregates and had increased tolerance to the antibiotic tobramycin compared with biofilms grown on glass. Analysis of selected mutant backgrounds in conjunction with time-lapse microscopy revealed that surface-associated motility was blocked on the mucin surface. Furthermore, our data suggest that a specific adhesin-mucin interaction immobilizes the bacterium on the surface. Together, these experiments suggest that mucin, which may serve as an attachment surface in CF airways, impacts P. aeruginosa biofilm development and function.

Overrepresentation of immunostimulatory CpG motifs in Burkholderia genomes

Pulmonary infections with Burkholderia cepacia complex organisms contribute significantly to morbidity and mortality in patients with cystic fibrosis (CF), partially due to the intense inflammatory response of the host to the presence of bacteria and their byproducts. In the present study we show that Burkholderia genomes contain a large number of immunostimulatory CpG motifs. This is mainly because of their large genome size. This suggests that DNA from Burkholderia sp. has the potential to cause significant inflammatory response. Whether this contributes significantly to the airway inflammation often observed in infected CF patients remains to be determined.

A novel strategy for the isolation and identification of environmental Burkholderia cepacia complex bacteria

The purpose of this study was to develop a novel strategy for the isolation and identification of Burkholderia cepacia complex bacteria from the home environment of cystic fibrosis (CF) patients. Water and soil samples were enriched in a broth containing 0.1% l-arabinose, 0.1% l-threonine, and a mixture of selective agents including 1 microgml(-1) C-390, 600U ml(-1) polymyxin B sulfate, 10 microgml(-1) gentamycin, 2 microgml(-1) vancomycin and 10 microgml(-1) cycloheximide. On selective media (consisting of the same components as above plus 1.8% agar), several dilutions of the enrichment broth were inoculated and incubated for 5 days at 28 degrees C. Isolates with different randomly amplified polymorphic DNA patterns were inoculated in Stewart's medium. Putative B. cepacia complex bacteria were confirmed by means of recA PCR and further identified by HaeIII-recA restriction fragment length polymorphism analysis. Our results suggest that these organisms may be more widespread in the home environment than previously assumed and that plant associated soil and pond water may be reservoirs of B. cepacia complex infection in CF patients.

Pyocyanin and its precursor phenazine-1-carboxylic acid increase IL-8 and intercellular adhesion molecule-1 expression in human airway epithelial cells by oxidant-dependent mechanisms

Pseudomonas aeruginosa secretes numerous factors that alter host cell function and may contribute to disease pathogenesis. Among recognized virulence factors is the redox-active phenazine pyocyanin. We have recently demonstrated that the precursor for pyocyanin, phenazine-1-carboxylic acid (PCA), increases oxidant formation and alters gene expression in human airway epithelial cells. We report in this work that PCA and pyocyanin increase expression of ICAM-1 both in vivo and in vitro. Moreover, phenazines enhanced cytokine-dependent increases in IL-8 and ICAM-1. Antioxidant intervention studies indicated both similarities and differences between PCA and pyocyanin. The thiol antioxidant N-acetyl cysteine, extracellular catalase, and inducible NO synthase inhibitors inhibited ICAM-1 and IL-8 increases in response to both phenazines. However, pyocyanin was significantly more sensitive to N-acetylcysteine inhibition. Interestingly, hydroxyl radical scavengers inhibited the response to pyocyanin, but not to PCA. These studies suggest that P. aeruginosa phenazines coordinately up-regulate chemokines (IL-8) and adhesion molecules (ICAM-1) by mechanisms that are, at least in part, oxidant dependent. However, results indicate that the mechanisms by which PCA and pyocyanin exert their effects are not identical, and not all antioxidant interventions are equally effective in inhibiting phenazine-mediated proinflammatory effects.

Effect of oxygen limitation on the in vitro antimicrobial susceptibility of clinical isolates of Pseudomonas aeruginosa grown planktonically and as biofilms

Pseudomonas aeruginosa, the predominant causative pathogen of chronic lung infection in patients with cystic fibrosis, may grow under anaerobic conditions as biofilms in the lungs of cystic fibrosis patients. To determine if growth under anaerobic conditions affects the antimicrobial susceptibility of P. aeruginosa, the susceptibility of clinical isolates of P. aeruginosa grown planktonically and as biofilms to a range of antibiotics was determined. Growth under anaerobic conditions did not reduce the ability of ceftazidime, meropenem, aztreonam, piperacillin, or piperacillin/tazobactam to inhibit planktonic growth, with MIC50 values for these antibiotics remaining unchanged or decreasing. However, tobramycin was less effective at inhibiting planktonic bacterial growth under anaerobic conditions, with the MIC50 of tobramycin increasing twofold. Growth under anaerobic conditions also decreased the bactericidal activity of tobramycin, with the MBC50 of tobramycin increasing fourfold. The killing kinetics of tobramycin was also examined under aerobic and anaerobic conditions for selected isolates. When isolates 6A and 12A were grown aerobically, concentration-dependent decreases in total viable count were apparent with tobramycin. In contrast, when these isolates were grown anaerobically, tobramycin at the same concentrations did not decrease the total viable count. When isolates were grown as biofilms under both aerobic and anaerobic conditions, isolate- and concentration-dependent differences in killing of the biofilms by tobramycin were apparent. However, tobramycin at concentrations up to 128 mg/l was unable to eradicate biofilms of any of the isolates tested, whether biofilms were grown aerobically or anaerobically. These results show that oxygen limitation may reduce, in a strain-dependent manner, the susceptibility to tobramycin of P. aeruginosa grown planktonically and as biofilms.

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.

Age-related prevalence and distribution of nontuberculous mycobacterial species among patients with cystic fibrosis

We studied the prevalence and species distribution of nontuberculous mycobacteria (NTM) in relation to age in 385 patients with cystic fibrosis (CF) (mean age +/- standard deviation [range], 12.0 +/- 6.1 [1 to 24] years; sex ratio, 0.53) attending three Parisian centers. The overall prevalence of NTM in sputum was 8.1% (31 out of 385). The following NTM were isolated (n = 33): Mycobacterium abscessus (n = 13, 39.4%), Mycobacterium avium complex (MAC) (n = 7, 21.2%), Mycobacterium gordonae (n = 6, 18.2%), and other (n = 7, 21.2%). Sixteen patients met the American Thoracic Society microbiological criteria for NTM infection, including 11 patients positive for M. abscessus, 4 for MAC, and 1 for MAC and Mycobacterium kansasii. The overall prevalence of NTM was significantly lower in patients under 15 years old than for patients equal to or more than 15 years old (4.8 versus 14.9%, respectively; P = 0.001). M. abscessus was isolated at all ages, while MAC was not recovered before 15 years (prevalence of 0.0 and 5.2% in patients aged 1 to 14 and 15 to 24, respectively; P = 0.001).

Use of PCR analyses to define the distribution of Ralstonia species recovered from patients with cystic fibrosis

Two new PCR assays (for Ralstonia species and Ralstonia respiraculi), together with previously published PCR assays, were used to assess Ralstonia isolates recovered from 111 cystic fibrosis patients. Ralstonia mannitolilytica accounted for 46% of isolates, while R. respiraculi and Ralstonia pickettii accounted for 19% and 18%, respectively. Ralstonia basilensis and Ralstonia metallidurans, species not previously recovered from human samples, were also identified.

Characterization of Pseudomonas aeruginosa isolated from chronically infected children with cystic fibrosis in India

BACKGROUND

Pseudomonas aeruginosa is the leading cause of morbidity and mortality in patients with cystic fibrosis (CF). With chronicity of infection, the organism resides as a biofilm, shows multi-drug resistance, diversifies its colony morphology and becomes auxotrophic. The patients have been found to be colonized with multiple genotypes. The present work was carried out to characterize P. aeruginosa isolated from children with cystic fibrosis using phenotypic and genotypic methods.

RESULTS

We studied 56 patients with CF attending the Pediatric Chest clinic at All India Institute of Medical Sciences, New Delhi, India during August 1998-August 2001. These patients were regularly followed up at the clinic. Out of 56 patients, 27 were culture positive for P. aeruginosa where 8 were chronically infected (Group1) and 19 were intermittently colonized with the organism (Group2). Patients under Group1 had significantly higher rates of hospitalization, death and colonization with different colony morphotypes (p < 0.05). The isolates from Group1 patients were the positive producers of extended spectrum beta lactamase. A total of 5 auxotrophs were recovered from 2 patients where one was chronically infected with P. aeruginosa and the other was a recently enrolled patient. The auxotrophs had the specific requirement for methionine and arginine. Molecular typing revealed 33 ERIC-PCR (E1-E33) and 5 PCR-ribotyping (P1-P5) patterns. By ERIC-PCR, 4 patients were colonized with 2-4 genotypes and the remaining 23 patients were colonized with the single genotype.

CONCLUSION

With chronicity of infection, P. aeruginosa becomes multidrug resistant, diversifies its colony morphology, acquires mucoidity and shows auxotrophy for amino acids. The chronically infected patients can be colonized with multiple genotypes. Thus in a particular clinical set up, high index of suspicion should be there for diagnosis of CF patients so as to prevent the delay in diagnosis and management of CF patients.

Genome-wide transcriptional profiling of the steady-state response of Pseudomonas aeruginosa to hydrogen peroxide

The steady-state response of Pseudomonas aeruginosa to the oxidative-stress-generating agent hydrogen peroxide was analyzed by PAO1 transcriptome profiling. In total, 694, 411, and 237 genes were upregulated and 668, 576, and 468 genes were downregulated in P. aeruginosa strains TB, 892, and PAO1, respectively. The expression profiles of the two variants of the TB clone were significantly more related to each other than the expression profile of either strain was to that of PAO1. Exposure to H(2)O(2) activated by more than 10-fold the expression of the cyoABCD operon, which is key for aerobic respiration, and of oxidative-stress response elements such as the catalase KatB, the alkyl hydroperoxide reductase AhpF, and the thioredoxin reductase 2 operon. Genes for iron and sulfur homeostasis were upregulated. Most enzymes necessary for the conversion of amino acids into the citric acid cycle were globally downregulated at the transcriptional level. Nitrate respiration and arginine fermentation were shut off in the clone TB strains and attenuated in the PAO strain. The transcriptional profiles indicate that the two clone TB strains are more proficient in coping with H(2)O(2)-mediated oxidative stress than the reference strain PAO. According to this data, we recommend study of the transcriptome of strain PAO1 in parallel with those of at least two strains of another clone in order to differentiate common responses from clone- and strain-specific responses and to minimize overinterpretations of microarray data.

Population structure, antimicrobial resistance, and mutation frequencies of Streptococcus pneumoniae isolates from cystic fibrosis patients

Forty-eight Streptococcus pneumoniae isolates recovered from sputum samples from 26 cystic fibrosis (CF) patients attending our CF unit (1995 to 2003) were studied. Mean yearly incidence of isolation was 5.5%, and all were strains recovered from young patients (< or = 12 years). The isolation was linked to clinical exacerbation in 35% of the cases, but only 27% of these were not accompanied by other CF pathogens. Fifty percent of the patients presented with two to four isolates over the studied period. Pulsed-field gel electrophoresis-SmaI digestion revealed a high heterogeneity (32 pulsotypes among 48 isolates) and the persistence over a 6-month period of a single clone (clone A) in two patients. This clone, presenting a varied multiresistance phenotype, was identified as the Spain23F-1 clone and was also recognized in six other patients, including two out of nine patients from the CF unit of Sant Joan de Deu Hospital, Barcelona, Spain. In our isolates, 16 different serotypes were recognized, the most frequent being 23F (33.3%), 19F (18.8%), 6A (6.2%), and 6B (6.2%). High overall resistance rates were observed: to penicillin, 73%; to cefotaxime, 33%; to erythromycin, 42%; to tetracycline, 58%; to chloramphenicol, 48%; and to trimethoprim-sulfamethoxazole, 67%. Resistance to fluoroquinolones was not detected. Multiresistance was a common feature (60%). The percentage of S. pneumoniae strains with increased frequencies of mutation to rifampin resistance (> or = 7.5 x 10(-8)) was significantly higher (P = 0.02) in CF (60%) than among non-CF (37%) isolates in the same institution (M. I. Morosini et al., Antimicrob. Agents Chemother. 47:1464-1467, 2003). Even though a clear association with acute exacerbations could not be observed, long-term clonal persistence and variability, high frequency of antibiotic resistance, and hypermutability indicate the plasticity for adaptation of S. pneumoniae to the CF lung environment.

In vitro activity of doripenem (S-4661) against multidrug-resistant gram-negative bacilli isolated from patients with cystic fibrosis

Doripenem 50% inhibitory concentrations (MIC50) and 90% inhibitory concentrations (MIC90) for multidrug-resistant strains of mucoid Pseudomonas aeruginosa (n=200 strains), nonmucoid P. aeruginosa (n=200), and Burkholderia cepacia complex (n=200) isolated from patients with cystic fibrosis were 8 and 32, 8 and 64, and 8 and 32 microg/ml, respectively. Doripenem had somewhat better activity than established antimicrobial agents.

How much do Pseudomonas biofilms contribute to symptoms of pulmonary exacerbation in cystic fibrosis?

Recent studies suggest that chronic Pseudomonas aeruginosa lung infections in cystic fibrosis (CF) involve anaerobic biofilms, and that these biofilms are the reason chronic infections are rarely eradicated by antibiotic therapy, regardless of the in vitro susceptibility of infecting bacteria. These observations led to the development of an in vitro method for testing antibiotic susceptibility of CF clinical isolates in biofilms (Moskowitz et al., J Clin Microbiol 2004;42:1915-1922) and unearthed an apparent paradox. Antibiotics that remain cornerstones of clinical management of CF pulmonary exacerbations (e.g., beta-lactam antibiotics) appear to have little to no activity at clinically achievable concentrations when tested in vitro against clinical P. aeruginosa isolates growing in biofilms. The proven clinical efficacy of beta-lactam antibiotics in treating exacerbations, and the selection for beta-lactam resistance in vivo, suggest that planktonic bacteria play a significant role in pulmonary exacerbations of CF. A model of infection architecture is proposed in which biofilm and planktonic compartments each play a role in infection persistence and pulmonary exacerbation, respectively. Infection architecture may partially account for the observed lack of correlation between in vitro antibiotic susceptibility testing and clinical response to antibiotic therapy.

Pseudomonas aeruginosa tolerance to tobramycin, hydrogen peroxide and polymorphonuclear leukocytes is quorum-sensing dependent

The opportunistic human pathogen Pseudomonas aeruginosa is the predominant micro-organism of chronic lung infections in cystic fibrosis (CF) patients. P. aeruginosa colonizes the CF lungs by forming biofilm structures in the alveoli. In the biofilm mode of growth the bacteria are highly tolerant to otherwise lethal doses of antibiotics and are protected from bactericidal activity of polymorphonuclear leukocytes (PMNs). P. aeruginosa controls the expression of many of its virulence factors by means of a cell-cell communication system termed quorum sensing (QS). In the present report it is demonstrated that biofilm bacteria in which QS is blocked either by mutation or by administration of QS inhibitory drugs are sensitive to treatment with tobramycin and H2O2, and are readily phagocytosed by PMNs, in contrast to bacteria with functional QS systems. In contrast to the wild-type, QS-deficient biofilms led to an immediate respiratory-burst activation of the PMNs in vitro. In vivo QS-deficient mutants provoked a higher degree of inflammation. It is suggested that quorum signals and QS-inhibitory drugs play direct and opposite roles in this process. Consequently, the faster and highly efficient clearance of QS-deficient bacteria in vivo is probably a two-sided phenomenon: down regulation of virulence and activation of the innate immune system. These data also suggest that a combination of the action of PMNs and QS inhibitors along with conventional antibiotics would eliminate the biofilm-forming bacteria before a chronic infection is established.

An in vivo inducible gene of Pseudomonas aeruginosa encodes an anti-ExsA to suppress the type III secretion system

We have previously reported on the isolation of in vivo inducible genes of Pseudomonas aeruginosa using IVET system. One of such genes isolated from burn mouse infection model encodes a short open reading frame with unknown function. In this study, we demonstrate that this gene product specifically suppresses the expression of type III secretion genes in P. aeruginosa, thus named PtrA (Pseudomonas type III repressor A). A direct interaction between the PtrA and type III transcriptional activator ExsA was demonstrated, suggesting that its repressor function is probably realized through inhibition of the ExsA protein function. Indeed, an elevated expression of the exsA compensates the repressor effect of the PtrA. Interestingly, expression of the ptrA is highly and specifically induced by copper cation. A copper- responsive two-component regulatory system, copR-copS, has also been identified and shown to be essential for the copper resistance in P. aeruginosa as well as the activation of ptrA in response to the copper signal. Elevated expression of the ptrA during the infection of mouse burn wound suggests that P. aeruginosa has evolved tight regulatory systems to shut down energy-expensive type III secretion apparatus in response to specific environmental signals, such as copper stress.

BALF nitrite as an indicator of inflammation in children with cystic fibrosis

BACKGROUND

A unique substance reflecting the degree of inflammation localized to the lower respiratory tract in patients with cystic fibrosis (CF) has been the concern of several investigators and nitric oxide has gained interest for this purpose in the last decades.

OBJECTIVES

The aim of this study was to evaluate the cytokine and nitrite levels by showing the relationship between them in serum and bronchoalveolar lavage fluid (BALF) of patients with CF and patients in which flexible fiberoptic bronchoscopy (FFB) was applied because of indications other than infection.

METHODS

20 children with CF with mean age 8.2 years and 10 children as control group with mean age 4.2 years were included in the study. Cultures for aerobes, anaerobes, fungi and mycobacteria, cell differentials, cytokine and nitrite measurements were made from BALF specimens. White blood cell (WBC) count, erythrocyte sedimentation rate (ESR), quantitative C-reactive protein (QCRP), cytokine and nitrite levels were measured from serum samples.

RESULTS

BALF neutrophil, TNF-alpha, IL-8 and nitrite levels were significantly higher in patients with CF than control patients. There was no correlation between serum and BALF cytokine and nitrite levels. However, there was a significantly positive correlation between BALF IL-8 and nitrite levels in patients with CF (r = 0.5) and also in control patients (r = 0.6).

CONCLUSIONS

The results suggest that BALF nitrite levels reflect the degree of inflammation localized to lower respiratory tract and may be a useful indicator of airway inflammation for patients with CF.

Airway colonization by Acrophialophora fusispora in patients with cystic fibrosis

Acrophialophora fusispora is a thermotolerant soil fungus which is very unusual in clinical samples. Here we report four cases of transient or chronic airway colonization by A. fusispora in patients with cystic fibrosis (CF). However, the prevalence of this fungus in CF patients may be underestimated due to the currently poor knowledge of this fungus in most of the medical mycology laboratories. In addition, its clinical importance regarding CF remains to be evaluated.

Measurement of Immunoglobulin G against Mycobacterial Antigen A60 in Patients with Cystic Fibrosis and Lung Infection Due to Mycobacterium abscessus

BACKGROUND

The diagnosis and prognosis of lung infections due to the emerging nontuberculous mycobacterium (NTM) Mycobacterium abscessus are difficult to establish in children with cystic fibrosis.

METHODS

We evaluated the usefulness of an enzyme-linked immunosorbent assay for detecting serum IgG antibodies against the ubiquitous mycobacterial antigen A60.

RESULTS

A total of 186 patients with cystic fibrosis (mean age+/-SD, 12.0+/-5.0 years) were studied, including 15 M. abscessus-positive patients who fulfilled American Thoracic Society (ATS) criteria for NTM infection (M. abscessus-infected patients), 7 M. abscessus-positive patients who did not fulfill ATS criteria, 20 patients positive for various other NTM who did not fulfill ATS criteria, and 144 NTM-negative control patients; mean IgG titers (+/-SD) for these 4 groups were 718+/-342 U, 193+/-113 U, 129+/-49 U, and 121+/-53 U, respectively (M. abscessus-infected patients vs. each of the other groups, P<.005). The A60 IgG test was both sensitive (approximately 87%) and specific (approximately 95%) if adapted cutoff values were used (150 U and 250 U for patients aged <or=10 years and patients aged >10 years, respectively) and correlated well with results of acid-fast bacilli smears.

CONCLUSION

Measurement of anti-A60 IgG may be useful for both the diagnosis and assessment of activity of M. abscessus lung infection in persons with cystic fibrosis.

Burkholderia cepacia is associated with pulmonary hypertension and increased mortality among cystic fibrosis patients

The aim of the study was to evaluate the impact of Burkholderia cepacia on cardiovascular status and mortality in cystic fibrosis. Seven patients infected with B. cepacia were matched with 31 patients not infected with this organism for gender, age, height, weight, genotype, and percent predicted forced expiratory volume in one second, partial arterial oxygen pressure, and pancreatic sufficiency status. The pulmonary artery systolic pressure, as assessed by transthoracic echocardiography, was significantly higher in patients infected with B. cepacia (61.3 +/- 17.2 mm Hg) than in controls (37.3 +/- 13.9 mm Hg; P = 0.02), and the mean acceleration time was significantly lower (77 +/- 33 ms versus 108 +/- 25 ms; P = 0.02). The 6-month mortality was significantly higher in patients infected with B. cepacia (57% versus 16%; P = 0.02). Six of the seven patients infected with B. cepacia harbored the same ribotype (genomovar II, B. multivorans). Pulmonary hypertension was significantly more frequent in patients infected by B. cepacia and could contribute to the increased mortality rate.

The use of macrolide antibiotics in patients with cystic fibrosis

PURPOSE OF REVIEW

There has been much recent interest in the use of macrolide antibiotics as chronic suppressive therapy in patients with cystic fibrosis. Three recent randomized, placebo-controlled trials have been conducted.

RECENT FINDINGS

All three trials used similar regimens of azithromycin, and lung function improved after 3 to 6 months of treatment. The relative change in forced expiratory volume in 1 second predicted improved between 3.6% and 6.2%. Furthermore, the azithromycin treatment groups had improvement in a variety of secondary outcomes related to pulmonary exacerbations, including a reduction in antibiotic use (both intravenous and oral) and hospitalization rate. Furthermore, azithromycin was well tolerated: Only nausea, diarrhea, and wheezing (described as mild to moderate) occurred more frequently in the azithromycin group compared with the placebo group. The evidence for the clinical benefit of azithromycin in cystic fibrosis has been summarized in a Cochrane review in which a meta-analysis confirmed a significant improvement in forced expiratory volume in 1 second among the 286 pooled participants.

SUMMARY

Azithromycin has entered the therapeutic armamentarium for patients with cystic fibrosis who are chronically infected with Pseudomonas aeruginosa. Improved lung function, a reduction in pulmonary exacerbations and antibiotic use, and weight gain are potential benefits of this drug. Future studies should address the use of azithromycin in other cystic fibrosis patient populations, including those patients without chronic infection with P. aeruginosa, children younger than 6 years of age, and those infected with Burkholderia cepacia complex. The mechanism of action of macrolide antibiotics in cystic fibrosis remains unknown.

Prospective study on nontuberculous mycobacteria in patients with and without cystic fibrosis

Recent reports indicated an increase of nontuberculous mycobacteria (NTM) in cystic fibrosis (CF) patients. However, it is still a matter of discussion whether criteria for diagnosis of NTM pulmonary infection established by the American Thoracic Society (ATS) are applicable for CF patients. We determined incidence and prevalence of NTM in CF patients and non-CF patients without HIV infection, and validity of ATS criteria for CF patients. Over a period of 2 years, 1,251 respiratory samples were investigated for mycobacteria from 91 CF and 162 non-CF patients. For all patients with NTM recovery, we reviewed clinical charts and determined outcome for up to 2 years. Incidence and prevalence for repeated recovery of NTM were higher in CF patients, but not significantly. CF patients with repeated recovery of NTM met clinical and bacteriological ATS criteria, but radiographic criteria were not met. Treated CF patients showed favorable clinical outcomes, as opposed to untreated patients. We propose a modified definition for diagnosis and hence treatment of NTM pulmonary infection in CF patients.

Insights into cystic fibrosis microbiology from the European tobramycin trial in cystic fibrosis

The infection of the airways of cystic fibrosis patients by Pseudomonas aeruginosa is a complex, multistaged process that is associated with a deterioration of lung function. The complexity of the formation of biofilms and their interaction with the immune system means that treatment with antibiotics has been an uncertain science. Tobramycin nebuliser solution (TNS) is a novel formulation of the antibiotic tobramycin developed specifically for inhalation. A recent large trial comparing TNS with inhaled colistin provided an opportunity to define further the effect of antibiotic treatment on microbial infection. In the TNS group, the percentage of patients with a tobramycin minimal inhibitory concentration (MIC) > or = 4 mg l(-1) increased from 38 to 49%, and the percentage of patients with a colistin MIC > or = 4 mg l(-1) remained at 55%. In the colistin group, the percentage of patients with a colistin MIC > or = 4 mg l(-1) remained at 34%, whereas the percentage of patients with a tobramycin MIC > or = 4 mg l(-1) decreased from 27 to 16%. Furthermore, clinical and bacterial response to TNS and colistin was independent of the MIC at baseline. Neither antimicrobial therapy was associated with infection by Burkholderia cepacia or other inherently resistant pathogens. We conclude that conventional measures of antimicrobial resistance may underestimate the effectiveness of tobramycin and colistin when delivered at the high concentrations achieved with the TNS formulation.

Identification of AlgR-regulated genes in Pseudomonas aeruginosa by use of microarray analysis

The Pseudomonas aeruginosa transcriptional regulator AlgR controls a variety of different processes, including alginate production, type IV pilus function, and virulence, indicating that AlgR plays a pivotal role in the regulation of gene expression. In order to characterize the AlgR regulon, Pseudomonas Affymetrix GeneChips were used to generate the transcriptional profiles of (i) P. aeruginosa PAO1 versus its algR mutant in mid-logarithmic phase, (ii) P. aeruginosa PAO1 versus its algR mutant in stationary growth phase, and (iii) PAO1 versus PAO1 harboring an algR overexpression plasmid. Expression analysis revealed that, during mid-logarithmic growth, AlgR activated the expression of 58 genes while it repressed the expression of 37 others, while during stationary phase, it activated expression of 45 genes and repression of 14 genes. Confirmatory experiments were performed on two genes found to be AlgR repressed (hcnA and PA1557) and one AlgR-activated operon (fimU-pilVWXY1Y2). An S1 nuclease protection assay demonstrated that AlgR repressed both known hcnA promoters in PAO1. Additionally, direct measurement of hydrogen cyanide (HCN) production showed that P. aeruginosa PAO1 produced threefold-less HCN than did its algR deletion strain. AlgR also repressed transcription of two promoters of the uncharacterized open reading frame PA1557. Further, the twitching motility defect of an algR mutant was complemented by the fimTU-pilVWXY1Y2E operon, thus identifying the AlgR-controlled genes responsible for this defect in an algR mutant. This study identified four new roles for AlgR: (i) AlgR can repress gene transcription, (ii) AlgR activates the fimTU-pilVWXY1Y2E operon, (iii) AlgR regulates HCN production, and (iv) AlgR controls transcription of the putative cbb3-type cytochrome PA1557.

[Pharyngitis due to Burkholderia cepacia. Person-to-person transmission]

Burkholderia cepacia is a Gram-negative bacillus that is widely distributed in nature; it is isolated from the ground, water, plants and vegetables. Generally, it produces nosocomial infection due to contamination of disinfectants, medical equipment, prosthetic material and drugs, such as anesthetics or liquids used in urological irrigation. The most probable mechanism of transmission is through hospital material or through fomites among people after contact for several weeks or months. Recently, it has been considered as an important pathogen in immunocompromised patients, or in those with significant underlying diseases, such as chronic granulomastosis or cystic fibrosis. We present a case of pharyngitis due to B. cepacia and its transmission within a few days in two immunocompetent twin siblings without previous underlying diseases. The infection disappeared after specific treatment for this microorganism was started. We believe that samples should be taken from the pharynx and nasal pits in patients with acute upper respiratory tract processes that do not respond to empiric antibiotic treatment, before classifying them as viral infection without etiologic diagnosis.

Isolation and identification of Burkholderia cepacia by participants in an external Quality Assurance Program (QAP) between 1994 and 1999

AIM

External quality assurance programs (QAPs) provide an opportunity to benchmark laboratory performance according to the profile of specimens received. Participant confidentiality is maintained within each group of laboratories whose performance is measured using similar, repetitive exercises. Isolation and identification of Burkholderia cepacia from simulated cystic fibrosis (CF) sputa was a clinically relevant exercise that provided a model for this analytical approach.

METHODS

Between 1994 and 1999, six Royal College of Pathologists of Australasia (RCPA) Microbiology QAPs included four simulated CF sputa and two panels of oxidative Gram-negative bacilli. Laboratories were grouped according to experience with CF sputa disclosed by two questionnaires. Data were analysed by laboratory group for ability to isolate and identify B. cepacia.

RESULTS

Three laboratory groups annually received >100 CF sputa (CF>100), 100 CF sputa or fewer, or did not regularly receive CF sputa. CF>100 laboratories inoculated more isolation media, were more likely to use selective media and were less likely to misidentify B. cepacia than the other groups. Improved performance by CF>100 laboratories was marked after the first exercise and remained at a high level compared with the other two groups. This trend in performance was also apparent for Pseudomonas aeruginosa although the numbers of errors were less than for B. cepacia.

CONCLUSIONS

These exercises demonstrated consistently improved performance only among CF>100 laboratories. The future criteria for laboratory accreditation may include performance as well as participation in QAPs, placing additional burdens on organisers and participants.

Cloning, overexpression, and characterization of a novel thermostable penicillin G acylase from Achromobacter xylosoxidans: probing the molecular basis for its high thermostability

The gene encoding a novel penicillin G acylase (PGA), designated pgaW, was cloned from Achromobacter xylosoxidans and overexpressed in Escherichia coli. The pgaW gene contains an open reading frame of 2586 nucleotides. The deduced protein sequence encoded by pgaW has about 50% amino acid identity to several well-characterized PGAs, including those of Providencia rettgeri, Kluyvera cryocrescens, and Escherichia coli. Biochemical studies showed that the optimal temperature for this novel PGA (PGA650) activity is greater than 60 degrees C and its half-life of inactivation at 55 degrees C is four times longer than that of another previously reported thermostable PGA from Alcaligenes faecalis (R. M. D. Verhaert, A. M. Riemens, J. V. R. Laan, J. V. Duin, and W. J. Quax, Appl. Environ. Microbiol. 63:3412-3418, 1997). To our knowledge, this is the most thermostable PGA ever characterized. To explore the molecular basis of the higher thermostability of PGA650, homology structural modeling and amino acid composition analyses were performed. The results suggested that the increased number of buried ion pair networks, lower N and Q contents, excessive arginine residues, and remarkably high content of proline residues in the structure of PGA650 could contribute to its high thermostability. The unique characteristic of higher thermostability of this novel PGA provides some advantages for its potential application in industry.

Biofilm formation by the small colony variant phenotype of Pseudomonas aeruginosa

Pseudomonas aeruginosa is an ubiquitous environmental bacterium and an opportunistic human pathogen. Not only in most natural habitats but also within the human host, e.g. within the chronically infected cystic fibrosis lung, P. aeruginosa is associated with surfaces in structures known as biofilms. These functional communities represent a unique mode of bacterial growth where bacteria display particular phenotypes that are fundamentally different from planktonic cells. In this review the issue of the molecular mechanisms underlying the emergence of small colony variant (SCV) P. aeruginosa morphotypes that are especially capable of forming biofilms is addressed. It is assumed that the expression of the chaperone usher pathway (cup) genes encoding putative fimbrial adhesins is responsible for the phenotypic switch to an autoaggregative SCV phenotype. The elucidation of phenotypic switching in response to environmental stimuli will significantly increase our understanding of regulatory processes during bacterial adaptation and might be the basis for the initiation of the development of new antimicrobial treatment strategies.

Cloning and expression of a novel esterase gene cpoA from Burkholderia cepacia

AIMS

To screen and clone a novel enzyme with specific activity for the resolution of (R)-beta-acetylmercaptoisobutyrate (RAM) from (R,S)-beta-acetylmercaptoisobutyrate [(R,S)-ester].

METHODS AND RESULTS

A micro-organism that produces a novel esterase was isolated and identified as the bacterium Burkholderia cepacia by using the analysis of cellular fatty acids, Biolog automated microbial identification/characterization system, and 16S rRNA gene sequence analysis. A novel esterase gene was cloned from the chromosomal DNA of B. cepacia and was designated as cpoA. The cpoA encodes a polypeptide of 273 amino acids which shows a strong sequence homology with many bacterial nonhaeme chloroperoxidases. In addition, a typical serine-hydrolase motif, Gly-X-Ser-X-Gly, and the highly conserved catalytic triad, Ser95, Asp224, and His253, were identified in the deduced amino acid sequence of cpoA by multiple sequence alignment.

CONCLUSION

The cpoA cloned from B. cepacia encodes a novel esterase which is highly related to the nonhaeme chloroperoxidases.

SIGNIFICANCE AND IMPACT OF THE STUDY

This is the first report that describes the isolation and cloning of a serine esterase gene from B. cepacia, which is useful in the chiral resolution of (R,S)-ester. The cloned gene will allow additional research on the bifunctionality of the enzyme with esterase and chloroperoxidase activity at the structural and functional levels.

Antimicrobial susceptibility and synergistic activity of meropenem against Gram-negative non-fermentative bacteria isolated from cystic fibrosis patients

The objective of the present study was to evaluate the activity of meropenem (a beta-lactam carbapenem with good bactericidal potency and a very wide spectrum of activity) and of ticarcillin, ceftazidime ciprofloxacin, tobramycin, cefepime, which are the most commonly used antimicrobial agents for treatment of pulmonary infections associated with CF. The effect of these antibiotics was tested on 27 multiresistant strains isolated from 24 CF patients during 2000 and 2001. Furthermore, the in vitro synergistic effect of meropenem in association with the other antibiotics was evaluated. Ciprofloxacin, ticarcillin, meropenem and ceftazidime had the most activity and inhibited 66%, 37%, 36% and 33% of strains respectively. The addition of a second antibiotic to meropenem resulted in a synergistic effect on 5 (18.5%) isolates; on average 2.8 synergistic combinations where determined per strain. Of these 27 isolates, antagonism was observed in 3 (11%) strains (1 antagonistic combination per strain). Our study suggests that selecting effective double antibiotic therapy cannot be made empirically for CF patients infected with Gram-negative multiresistant bacilli. Therefore in vitro methods for testing double antibiotic combinations are mandatory.

Pathogenicity islands in bacterial pathogenesis

In this review, we focus on a group of mobile genetic elements designated pathogenicity islands (PAI). These elements play a pivotal role in the virulence of bacterial pathogens of humans and are also essential for virulence in pathogens of animals and plants. Characteristic molecular features of PAI of important human pathogens and their role in pathogenesis are described. The availability of a large number of genome sequences of pathogenic bacteria and their benign relatives currently offers a unique opportunity for the identification of novel pathogen-specific genomic islands. However, this knowledge has to be complemented by improved model systems for the analysis of virulence functions of bacterial pathogens. PAI apparently have been acquired during the speciation of pathogens from their nonpathogenic or environmental ancestors. The acquisition of PAI not only is an ancient evolutionary event that led to the appearance of bacterial pathogens on a timescale of millions of years but also may represent a mechanism that contributes to the appearance of new pathogens within a human life span. The acquisition of knowledge about PAI, their structure, their mobility, and the pathogenicity factors they encode not only is helpful in gaining a better understanding of bacterial evolution and interactions of pathogens with eukaryotic host cells but also may have important practical implications such as providing delivery systems for vaccination, tools for cell biology, and tools for the development of new strategies for therapy of bacterial infections.

Cystic fibrosis airway epithelial cell polarity and bacterial flagellin determine host response toPseudomonas aeruginosa

The role of epithelial polarity and bacterial factors in the control of the innate immune response of airway epithelial cells to Pseudomonas aeruginosa PAK was investigated using a human, nasal cystic fibrosis (DeltaF508/DeltaF508) epithelial cell line CF15 grown as confluent layers on permeable supports. Addition of PAK to the basal surface of CF15 layers caused significant expression changes in 1525 different genes (out of 12 625 examined), including the cytokines IL-6, IL-8, IL-1beta and TNF-alpha, as well as genes associated with leucocyte adhesion, antibacterial factors, and NF-kappaB signalling. Confocal microscopy showed that nuclear migration of NF-kappaB in all CF15 cells was preceded by PAK binding to the basal and lateral surfaces of some cells. Addition of PAK to the apical surface of CF15 monolayers elicited changes in expression of only 602 genes, including 256 not affected during basolateral PAK exposure. Over time, cytokine expression during apical PAK was similar to that exhibited by basal PAK, but the magnitudes during apical treatment were much smaller with little/no nuclear migration of NF-kappaB in CF15 cells. Furthermore, these responses depended on the presence of flagellin, but not pili on the bacteria. Thus, P. aeruginosa triggered a strong innate immune response that depended on the apical versus basolateral polarity of CF15 cells and the presence of flagellin on the bacteria.

Primary ciliary dyskinesia: diagnostic and phenotypic features

Primary ciliary dyskinesia (PCD) is a genetic disease characterized by abnormalities in ciliary structure/function. We hypothesized that the major clinical and biologic phenotypic markers of the disease could be evaluated by studying a cohort of subjects suspected of having PCD. Of 110 subjects evaluated, PCD was diagnosed in 78 subjects using a combination of compatible clinical features coupled with tests of ciliary ultrastructure and function. Chronic rhinitis/sinusitis (n = 78; 100%), recurrent otitis media (n = 74; 95%), neonatal respiratory symptoms (n = 57; 73%), and situs inversus (n = 43; 55%) are strong phenotypic markers of the disease. Mucoid Pseudomonas aeruginosa (n = 12; 15%) and nontuberculous mycobacteria (n = 8; 10%) were present in older (> 30 years) patients with PCD. All subjects had defects in ciliary structure, 66% in the outer dynein arm. Nasal nitric oxide production was very low in PCD (nl/minute; 19 +/- 17 vs. 376 +/- 124 in normal control subjects). Rigorous clinical and ciliary phenotyping and measures of nasal nitric oxide are useful for the diagnosis of PCD. An increased awareness of the clinical presentation and diagnostic criteria for PCD will help lead to better diagnosis and care for this orphan disease.

Identification of bacteria recovered from clinical specimens by 16S rRNA gene sequencing

The sequence of the 16S rRNA gene has been used extensively for phylogenetic classification, identification, and genotypic typing of bacteria. Identification of bacterial isolates by 16S rRNA gene sequencing, though generally performed in reference laboratories, has been recently introduced for routine use in clinical laboratories to identify isolates that cannot be identified by conventional methods. Described in this report is the use of 16S rRNA gene sequencing to identify uncommon bacteria, or bacteria with unusual phenotypic properties, with four brief case presentations to illustrate its clinical application. The feasibility, usefulness and limitations of performing this approach in the clinical laboratory are also discussed.

Gammadelta T lymphocytes from cystic fibrosis patients and healthy donors are high TNF-alpha and IFN-gamma-producers in response to Pseudomonas aeruginosa

BACKGROUND

Gammadelta T cells have an important immunoregulatory and effector function through cytokine release. They are involved in the responses to Gram-negative bacterium and in protection of lung epithelium integrity. On the other hand, they have been implicated in airway inflammation.

METHODS

The aim of the present work was to study intracytoplasmic IL-2, IL-4, IFN-gamma and TNF-alpha production by gammadelta and alphabeta T lymphocytes from cystic fibrosis patients and healthy donors in response to Pseudomonas aeruginosa (PA). Flow cytometric detection was performed after peripheral blood mononuclear cells (PBMC) culture with a cytosolic extract from PA and restimulation with phorbol ester plus ionomycine. Proliferative responses, activation markers and receptor usage of gammadelta T cells were also evaluated.

RESULTS

The highest production of cytokine was of TNF-alpha and IFN-gamma, gammadelta being better producers than alphabeta. No differences were found between patients and controls. The Vgamma9delta2 subset of gammadelta T cells was preferentially expanded. CD25 and CD45RO expression by the alphabeta T subset and PBMC proliferative response to PA were defective in cystic fibrosis lymphocytes.

CONCLUSION

Our results support the hypothesis that gammadelta T lymphocytes play an important role in the immune response to PA and in the chronic inflammatory lung reaction in cystic fibrosis patients. They do not confirm the involvement of a supressed Th1 cytokine response in the pathogenesis of this disease.