Association between glucose intolerance and bacterial colonisation in an adult population with cystic fibrosis, emergence of Stenotrophomonas maltophilia

ESPEN-ESPGHAN-ECFS guideline on nutrition care for cystic fibrosis

BACKGROUND

Nutritional status is paramount in Cystic Fibrosis (CF) and is directly correlated with morbidity and mortality. The first ESPEN-ESPGHAN-ECFS guidelines on nutrition care for infants, children, and adults with CF were published in 2016. An update to these guidelines is presented.

METHODS

The study was developed by an international multidisciplinary working group in accordance with officially accepted standards. Literature since 2016 was reviewed, PICO questions were discussed and the GRADE system was utilized. Statements were discussed and submitted for on-line voting by the Working Group and by all ESPEN members.

RESULTS

The Working Group updated the nutritional guidelines including assessment and management at all ages. Supplementation of vitamins and pancreatic enzymes remains largely the same. There are expanded chapters on pregnancy, CF-related liver disease, and CF-related diabetes, bone disease, nutritional and mineral supplements, and probiotics. There are new chapters on nutrition with highly effective modulator therapies and nutrition after organ transplantation.

Continuous glucose monitoring versus self-monitoring of blood glucose in the management of cystic fibrosis related diabetes: A systematic review and meta-analysis

BACKGROUND

Treatment of cystic fibrosis related diabetes (CFRD) can improve outcomes and use of continuous glucose monitoring (CGM) can positively impact glycemic control. We conducted a systematic review to assess current evidence on CGM compared to self-monitoring of blood glucose (SMBG) in the management of CFRD to determine its effect on glycemic, pulmonary, non-pulmonary and quality of life outcomes.

METHODS

Using pre-defined selection criteria, we searched MEDLINE, Embase, CENTRAL, Evidence-Based Medicine Reviews, grey literature and six relevant journals for studies using CGM and/or SMBG in CFRD with greater than 6 weeks of follow-up and reported change in HbA1c. The primary outcome was weighted mean difference (WMD) in plasma HbA1c between CGM and SMBG groups. Secondary outcomes included exploring interrelationships between CGM metrics and effects on disease-specific pulmonary, non-pulmonary and quality of life outcomes.

RESULTS

A total of 1671 references were retrieved, 862 studies screened and 124 full-texts assessed for eligibility. No studies directly compared CGM to SMBG. A meta-analysis of seventeen studies of 416 individuals (CGM = 138, SMBG = 278) found CGM group had 4.1 mmol/mol (95% CI -7.9 to -0.30, p = 0.034) lower HbA1c compared to SMBG group. Most studies demonstrated moderate-to-high risk of bias. Publication bias was also present. Heterogeneity was high and meta-regression identified duration of follow-up in SMBG group as main contributor.

CONCLUSION

Our findings suggest use of CGM may be associated with improved glycemic control compared to SMBG in CFRD, however evidence of benefit on pulmonary, non-pulmonary and psychosocial outcomes are lacking.

Mediation of the total effect of cystic fibrosis-related diabetes on mortality: A UK Cystic Fibrosis Registry cohort study

AIM

To investigate whether the effect of cystic fibrosis-related diabetes (CFRD) on the composite outcome of mortality or transplant could act through lung function, pulmonary exacerbations and/or nutritional status.

METHODS

A retrospective cohort of adult cystic fibrosis (CF) patients who had not been diagnosed with CFRD were identified from the UK Cystic Fibrosis Registry (n = 2750). Rate of death or transplant was compared between patients who did and did not develop CFRD (with insulin use) during follow-up using Poisson regression, separately by sex. Causal mediation methods were used to investigate whether lung function, pulmonary exacerbations and nutritional status lie on the causal pathway between insulin-treated CFRD and mortality/transplant.

RESULTS

At all ages, the mortality/transplant rate was higher in both men and women diagnosed with CFRD. Pulmonary exacerbations were the strongest mediator of the effect of CFRD on mortality/transplant, with an estimated 15% [95% CI: 7%, 28%] of the effect at 2 years post-CFRD diagnosis attributed to exacerbations, growing to 24% [95% CI: 9%, 46%] at 4 years post-diagnosis. Neither lung function nor nutritional status were found to be significant mediators of this effect. Estimates were similar but with wider confidence intervals in a cohort that additionally included people with CFRD but not using insulin.

CONCLUSION

There is evidence that pulmonary exacerbations mediate the effect of CFRD on mortality but, as they are estimated to mediate less than one-quarter of the total effect, the mechanism through which CFRD influences survival may involve other factors.

Continuous glucose monitoring indices predict poor FEV1 recovery following cystic fibrosis pulmonary exacerbations

BACKGROUND

Little is known about the effect of dysglycemia during cystic fibrosis pulmonary exacerbation (PEx) on recovery of FEV₁ percentage predicted (ppFEV₁) METHODS: Continuous glucose monitoring (CGM) was commenced at the time of admission to hospital for PEx and continued for 6 weeks. The CGM indices, percentage of time glucose greater than 7.8 mmol/L (%T>7.8) and mean glucose were evaluated as predictors of absolute ppFEV₁ change following treatment of PEx.

RESULTS

Of the 20 participants who completed the study 13 (65%) had cystic fibrosis related diabetes (CFRD). The mean of both CGM indices were highest during the first week of pulmonary exacerbation and continued to decline over the first 4 weeks at which point they plateaued. Using multivariate regression models, factors which were predictive of maximum attained ppFEV₁ change over 6 weeks were %T>7.8, mean glucose, HbA1c and preadmission ppFEV₁ change from baseline. These relationships were independent of a diagnosis of CFRD, which was not associated with ppFEV₁ recovery. In a longitudinal model of ppFEV₁ change at weeks 1, 2 and 6, the CGM index %T>7.8 approached significance as a predictive variable.

CONCLUSIONS

Hyperglycemia during PEx in adult CF patients is associated with poorer ppFEV₁ recovery. Conversely, there was no association observed between CFRD diagnosis and ppFEV₁ improvement, suggesting that optimization of glycemic control in CFRD patients may positively influence recovery of lung function. Further clinical trials are required to evaluate the merits of intensive glycemic control in CFRD during PEx.

Stenotrophomonas maltophilia Differential Gene Expression in Synthetic Cystic Fibrosis Sputum Reveals Shared and Cystic Fibrosis Strain-Specific Responses to the Sputum Environment

Stenotrophomonas maltophilia is a Gram-negative opportunistic pathogen that can infect the lungs of people with cystic fibrosis (CF). The highly viscous mucus in the CF lung, expectorated as sputum, serves as the primary nutrient source for microbes colonizing this site and induces virulence-associated phenotypes and gene expression in several CF pathogens. Here, we characterized the transcriptional responses of three S. maltophilia strains during exposure to synthetic CF sputum medium (SCFM2) to gain insight into how this organism interacts with the host in the CF lung. These efforts led to the identification of 881 transcripts differentially expressed by all three strains, many of which reflect the metabolic pathways used by S. maltophilia in sputum, as well as altered stress responses. The latter correlated with increased resistance to peroxide exposure after pregrowth in SCFM2 for two of the strains. We also compared the SCFM2 transcriptomes of two S. maltophilia CF isolates to that of the acute infection strain, S. maltophilia K279a, allowing us to identify CF isolate-specific signatures in differential gene expression. The expression of genes from the accessory genomes was also differentially altered in response to SCFM2. Finally, a number of biofilm-associated genes were differentially induced in SCFM2, particularly in K279a, which corresponded to increased aggregation and biofilm formation in this strain relative to both CF strains. Collectively, this work details the response of S. maltophilia to an environment that mimics important aspects of the CF lung, identifying potential survival strategies and metabolic pathways used by S. maltophilia during infections.IMPORTANCE Stenotrophomonas maltophilia is an important infecting bacterium in the airways of people with cystic fibrosis (CF). However, compared to the other CF pathogens, S. maltophilia has been relatively understudied. The significance of our research is to provide insight into the global transcriptomic changes of S. maltophilia in response to a medium that was designed to mimic important aspects of the CF lung. This study elucidates the overall metabolic changes that occur when S. maltophilia encounters the CF lung and generates a road map of candidate genes to test using in vitro and in vivo models of CF.

Cystic fibrosis-related diabetes: optimizing care with a multidisciplinary approach

Cystic fibrosis-related diabetes (CFRD) is a common complication of cystic fibrosis and can be present in over 50% of adults with the disease. CFRD is associated with poorer clinical outcomes, including accelerated pulmonary function decline and excess morbidity. The management of CFRD is complex and differs from that of type 1 and type 2 diabetes mellitus such that clinicians responsible for the care of people with CFRD must work closely with colleagues across a number of different specialities and disciplines. This review aims to discuss why a multi-disciplinary approach is important and how it can be harnessed to optimize the care of people with CFRD.

Cystic fibrosis related diabetes is not independently associated with increased Stenotrophomonas maltophilia infection: Longitudinal data from the UK CF Registry

INTRODUCTION

Stenotrophomonas maltophilia is common in the sputum of people with cystic fibrosis related diabetes (CFRD), raising the question as to whether this is a risk factor for its acquisition. We investigated this at a population level.

METHODS

We analysed national Cystic Fibrosis Registry data 2011-2015 for 8047 people with CF > age 6 years, looking at demographics, diagnosis of CFRD, lung function and sputum microbiology; using descriptive and multivariate strategies to establish independent predictors for S. maltophilia culture and associated outcomes.

RESULTS

S. maltophilia was present in 1148 (14.1%). Although univariate analysis confirmed it was more prevalent in those with CFRD, when adjusted for other clinical parameters there was no longer a relationship. Markers of more severe lung disease were independent risk-factors for S. maltophilia.

CONCLUSION

Although S. maltophilia is more common in people with CFRD, it is not an independent risk-factor for S. maltophilia acquisition.

Ventilation inhomogeneity is associated with OGTT-derived insulin secretory defects in cystic fibrosis

Progressive deterioration of β-cell function is the main mechanism underlying diabetes in cystic fibrosis (CF). Diabetes negatively impacts the clinical status of CF patients years before its onset. We aimed to evaluate if OGTT-derived indices of β-cell function are associated with early markers of lung disease. We carried out a cross-sectional study on 80 CF patients who performed OGTT, spirometry, and nitrogen-multiple breath washout test. β-cell glucose sensitivity and the insulinogenic indices were used as markers of β-cell function and first-phase insulin response to glucose stimulus. We used sex- and age-adjusted multiple linear regression models to estimate the association between OGTT-derived indices and lung function measures. An increment of β-cell glucose sensitivity equal to its interquartile range was associated with an increase in ppFEV₁ of 7.6 points (95%CI: 0.8; 14.4) as well as with a decrease in LCI of -1.96 units (95%CI: -3.40; -0.51) and in S_cond of -0.016 L^-1 (95%CI: -0.026; -0.007). The corresponding figures for insulinogenic index were: 8.6 (95%CI: 3.4; 13.9) for ppFEV₁ , -2.03 (95%CI: -3.13; -0.94) for LCI, and -0.014 L^-1 (95%CI: -0.021; -0.071) for S_cond . When adjusting also for 2-h plasma glucose, both β-cell glucose sensitivity and insulinogenic index remained inversely associated with S_cond . Deterioration of β-cell function is related to early lung disease in young patients with mild to normal pulmonary function. This relationship is independent from hyperglycemia and mainly involves conductive airways.

Draft Genome Sequences of Two Cystic Fibrosis Strains of Stenotrophomonas maltophilia, AU30115 and AU32848

Stenotrophomonas maltophilia is an opportunistic pathogen causing airway infection in people with cystic fibrosis (CF). Here, we report the draft genome sequences of two S. maltophilia strains, AU30115 and AU32848, recovered from CF patients.

Stenotrophomonas maltophilia is an opportunistic pathogen causing airway infection in people with cystic fibrosis (CF). Here, we report the draft genome sequences of two S. maltophilia strains, AU30115 and AU32848, recovered from CF patients.

Cystic Fibrosis: Emerging Understanding and Therapies

Cystic fibrosis (CF) is the most common life-limiting genetic disease in Caucasian patients. Continued advances have led to improved survival, and adults with CF now outnumber children. As our understanding of the disease improves, new therapies have emerged that improve the basic defect, enabling patient-specific treatment and improved outcomes. However, recurrent exacerbations continue to lead to morbidity and mortality, and new pathogens have been identified that may lead to worse outcomes. In addition, new complications, such as CF-related diabetes and increased risk of gastrointestinal cancers, are creating new challenges in management. For patients with end-stage disease, lung transplantation has remained one of the few treatment options, but challenges in identifying the most appropriate patients remain.