In vitro antimicrobial activity of ceftolozane/tazobactam against Pseudomonas aeruginosa and other non-fermenting Gram-negative bacteria in adults with cystic fibrosis

OBJECTIVES

Pulmonary exacerbations in patients with cystic fibrosis (CF) caused by chronic Gram-negative bacterial infections are associated with reduced survival. These pathogens are usually treated with repeated courses of systemic antimicrobial agents. However, there is associated emergence of multidrug-resistant (MDR) pathogens. Ceftolozane/tazobactam (C/T) is a novel cephalosporin/β-lactamase inhibitor combination that has been demonstrated to have good activity against MDR Pseudomonas aeruginosa.

METHODS

In this study, C/T was compared with other commonly used intravenous antimicrobial agents against 193 non-fermenting Gram-negative bacteria isolated from CF sputum specimens, including P. aeruginosa, Achromobacter xylosoxidans, Stenotrophomonas maltophilia and Burkholderia cenocepacia. Minimum inhibitory concentrations (MICs) to C/T were determined by standard Etest assay and were interpreted according to current European Committee on Antimicrobial Susceptibility Testing (EUCAST) guidelines.

RESULTS

C/T had good in vitro antimicrobial activity against CF clinical isolates of P. aeruginosa in comparison with other antimicrobial agents, with the exception of colistin. C/T also had activity against S. maltophilia but was not active against B. cenocepacia or A. xylosoxidans.

CONCLUSION

C/T showed excellent in vitro activity against P. aeruginosa CF clinical isolates. This antimicrobial agent is a potential therapeutic option when presented with challenging MDR P. aeruginosa and S. maltophilia exacerbations. Further clinical experience and trials in CF are required to determine the place of C/T in clinical practice.

Muddy puddles - the microbiology of puddles located outside tertiary university teaching hospitals

In the British Isles, the frequency of rain results in the formation of puddles on footpaths and roads in/around hospitals. No data are available demonstrating the microbiological composition of such puddles and therefore a study was undertaken to examine the microbiology of puddles in the grounds of two tertiary university-teaching hospitals (18 sites) and compared with control puddles from non-hospital rural environments (eight sites), estimating (i) total viable count; (ii) identification of organisms in puddles; (iii) enumeration of Escherichia coli: (iv) detection of Extended Spectrum β-Lactamase producing organisms and (v) direct antimicrobial susceptibility testing. A mean count of 2·3 × 10³  CFU per ml and 1·0 × 10⁹  CFU per ml was obtained for hospital and non-hospital puddles respectively. Isolates (n = 77; 54 hospital and 23 non-hospital) were isolated comprising of 23 species among 17 genera (hospital sites), where the majority (10/16; 62·5%) of genera identified were Gram-negative approximately, a fifth (20·6%) were shared by hospital and non-hospital rural samples. Escherichia coli was detected in half of the hospital puddles and under-half (37·5%) of the rural puddles extended spectrum β-lactamase organisms were not detected in any samples examined. Rainwater puddles from the hospital and non-hospital environments contain a diverse range of bacteria, which are capable of causing infections.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study demonstrated the presence of a wide diversity of bacterial taxa associated with rainwater puddles around hospitals, many of which are capable of causing human disease. Of clinical significance is the presence of Pseudomonas aeruginosa isolated from a hospital puddle, particularly for patients with cystic fibrosis. The presence of potentially disease-causing bacteria in puddles in and around hospitals identifies a new potential environmental reservoir of bacteria. Furthermore work is now needed to define their potential of entering or exiting hospital wards by contaminated footwear.

Temporal Analysis of Factors Associated with EAT-10 in Outpatients with Oropharyngeal Dysphagia from a Tertiary Care Clinic

Self-perception of disease is increasingly recognized as a determinant of health. The Eating Assessment Tool-10 (EAT-10) is a functional health status questionnaire that measures the symptomatic severity of dysphagia from the patient's perspective. The objective of this work was to identify factors (demographics, clinical variables, swallowing physiology, health-related quality of life) associated with longitudinal change in EAT-10 scores in outpatients with oropharyngeal dysphagia at a multi-disciplinary, tertiary care clinic. All patients with swallowing concerns that were included in the UW Madison Voice and Swallowing Outcomes database from 12/2012 to 04/2015 were invited to complete EAT-10 and a general health-related quality of life survey (SF-12v2) at their initial evaluation and six months later. Forty-two patients were included in analysis (n = 42). Weaning from a gastrostomy tube was significantly associated with EAT-10 improvement. Approximately 70% of the sample had mild dysphagia, and floor effects were observed for all EAT-10 items in this sample subset. Mean SF-12v2 Physical Component Summary score was substantially lower than that of the general population. Significant, weak-moderate correlations were found between EAT-10 and SF-12v2 scores for all comparisons except for Physical Health Composite at six months (rs = = 0.24 to - 0.43). Weaning from a feeding tube appears to meaningfully improve self-perceived symptoms of dysphagia. Given the floor effects observed, validity of EAT-10 for patients with mild dysphagia should be examined. Future research should address contributors to self-perceived symptom change across the range of dysphagia severity.

Pseudomonas aeruginosa in cystic fibrosis patients with c.1652G›A (G551D)-CFTR treated with ivacaftor-Changes in microbiological parameters

WHAT IS KNOWN AND OBJECTIVE

The CFTR potentiator, ivacaftor (IVA), has been widely used in the treatment of cystic fibrosis (CF) patients with the G551D mutation. To date, there has been limited information on the microbiological status of patients on this therapy and no data on the effect (if any) on the in vivo antibiotic susceptibility of Pseudomonas aeruginosa isolated from patients on therapy. Although IVA intervention is not designed per se as anti-infective, the effect (if any) of this molecule to CF patients' microbiological status merits careful monitoring. Therefore, it was the aim of this observational study to examine the effect in patients, both before and after commencement of IVA therapy, on several commonly reported microbiological markers in CF patients, including (i) bacterial density, (ii) frequency (rate) of isolation of bacterial pathogens, particularly P. aeruginosa, and (iii) antimicrobial susceptibility of these isolates to commonly prescribed oral and iv antibiotics. In addition, we wished to examine the requirements for these antibiotics in CF patients, before and after commencement of IVA therapy.

METHODS

Archived data from 15 adult cystic fibrosis patients with the c.1652G›A (G551D) mutation were followed from two years pre-IVA therapy to two years after commencement of IVA therapy. The microbiological parameters examined included (i) oral antibiotic courses taken, (ii) intravenous (iv) antibiotic courses taken, (iii) rate of isolation of non-mucoid Pseudomonas aeruginosa (NM-PA) and mucoid P. aeruginosa (M-PA), (iv) density of NM-PA and M-PA and (v) antimicrobial susceptibility of NM-PA and M-PA to 11 antibiotics [aminoglycosides, beta-lactams, polymyxin and fluoroquinolone].

RESULTS AND DISCUSSION

Following commencement of IVA therapy, patients required less iv antibiotic courses but no change in number of oral antibiotics courses. There was significant reduction in both the rate of isolation and density of M-PA (P = .02; P = .006, respectively). In contrast, there was no significant reduction in both the rate of isolation and density of NM-PA (P = .90; P = .07, respectively). Antimicrobial susceptibility in NM-PA and M-PA was not significantly reduced within any of the antibiotics classes or individual antibiotics examined. Increased susceptibility was noted in the beta-lactam class for NM-PA and M-PA, in particular with ceftazidime.

WHAT IS NEW AND CONCLUSION

Overall, (i) the requirement for less iv antibiotic therapy, (ii) a reduction in the rate and density of M-PA and (iii) no reduction in antibiotic susceptibility indicate that microbiological parameters with patients on IVA therapy were not detrimentally affected.

Valve-related modes of pump failure in collecting lymphatics: numerical and experimental investigation

Lymph is transported along collecting lymphatic vessels by intrinsic and extrinsic pumping. The walls have muscle of a type intermediate between blood-vascular smooth muscle and myocardium; a contracting segment between two valves (a lymphangion) constitutes a pump. This intrinsic mechanism is investigated ex vivo in isolated, spontaneously contracting, perfused segments subjected to controlled external pressures. The reaction to varying afterload is probed by slowly ramping up the outlet pressure until pumping fails. Often the failure occurs when the contraction raises intra-lymphangion pressure insufficiently to overcome the outlet pressure, open the outlet valve and cause ejection, but many segments fail by other means, the mechanisms of which are not clear. We here elucidate those mechanisms by resort to a numerical model. Experimental observations are paired with comparable findings from computer simulations, using a lumped-parameter model that incorporates previously measured valve properties, plus new measurements of active contractile and passive elastic properties, and the dependence of contraction frequency on transmural pressure, all taken from isobaric twitch contraction experiments in the same vessel. Surprisingly, the model predicts seven different possible modes of pump failure, each defined by a different sequence of valve events, with their occurrence depending on the parameter values and boundary conditions. Some, but not all, modes were found experimentally. Further model investigation reveals routes by which a vessel exhibiting one mode of failure might under altered circumstances exhibit another.

Clinical implications of Pseudomonas aeruginosa location in the lungs of patients with cystic fibrosis

WHAT IS KNOWN AND OBJECTIVE

Pseudomonas aeruginosa is the leading cause of lung infection in patients with cystic fibrosis (CF) and is associated with significant morbidity and mortality. Antibiotics are regarded as the foundational pharmacological treatment for the suppressive management of chronic P. aeruginosa infections and to eradicate the first infection by P. aeruginosa. Inhalation remains a preferred route for drug administration, providing direct access to the site of infection while minimizing systemic side effects. Effective suppressive management of P. aeruginosa infections, however, requires an understanding of the location of the bacteria in the lungs and consideration of the factors that could limit access of the inhaled antibiotic to the infected area. This review provides a systematic assessment of the scientific literature to gain insight into the location of P. aeruginosa in the lungs of patients with CF and its clinical implications. The characteristics of antibiotic inhalation systems are also discussed in this context.

METHODS

We reviewed evidence-based literature from both human and animal studies in which P. aeruginosa lung location was reported. Relevant publications were identified through a screening strategy and summarized by reported P. aeruginosa location.

RESULTS AND DISCUSSION

Most areas of the conductive and respiratory zones of the lungs are susceptible to P. aeruginosa colonization. Deposition of an inhaled antibiotic is dependent on the device and formulation characteristics, as well as the ability of the patient to generate sufficient inhaled volume. As patients with CF often experience a decline in lung function, the challenge is to ensure that the inhaled antibiotic can be delivered throughout the bronchial tree.

WHAT IS NEW AND CONCLUSION

An effective drug delivery system that can target P. aeruginosa in both the respiratory and conductive zones is required. The chosen inhalation device should also offer a drug formulation that can be quickly and effectively delivered to specific lung locations, with minimal inspiratory effort from the patient.

Meningococcal disease: has the battle been won?

Meningococcal disease is a worldwide life-threatening infection associated in many cases with debilitating long-term sequelae, both within the military and civilian populations. Military recruits are at a higher risk of acquiring this infection due to numerous factors, such as young recruits in the age group 18-25 years, high carriage rates of meningococci, communal and crowed living quarters and global deployment or training in regions with different meningococcal serogroup epidemiology. Although these increased risk factors among young recruits remain, the increased incidence of disease is now historic. Numerous outbreaks have been reported among military personnel, however although the incidence of the disease continues to decrease, there are still sporadic cases. The non-specific symptoms, sudden onset and rapid progression of the infection results in a limited time frame to both diagnose and successfully treat the patient. Many developments have been made in relation to the microbiological diagnosis of the disease, particularly in the era of molecular diagnostics, which have the potential to diagnose the infection more quickly. Developments in vaccinology, and in particular with relation to biotechnology and reverse vaccinology, have led to the availability of new meningococcal vaccines, further enabling disease prevention. This paper outlines the history of meningococcal disease in relation to the military and highlights the new developments in both diagnostics and vaccination, which have the potential to diagnose, treat and control meningococcal disease in a more efficient manner.

Quasi-Many-Body Localization in Translation-Invariant Systems

We examine localization phenomena associated with generic, high entropy, states of a translation-invariant, one-dimensional spin ladder. At early times, we find slow growth of entanglement entropy consistent with the known phenomenology of many-body localization in disordered, interacting systems. At intermediate times, however, anomalous diffusion sets in, leading to full spin polarization decay on an exponentially activated time scale. We identify a single length scale which parametrically controls both the spin transport times and the apparent divergence of the susceptibility to spin glass ordering. Ultimately, at the latest times, the exponentially slow anomalous diffusion gives way to diffusive thermal behavior. We dub the intermediate dynamical behavior, which persists over many orders of magnitude in time, quasi-many-body localization.

Modeling Lymph Flow and Fluid Exchange with Blood Vessels in Lymph Nodes

BACKGROUND

Lymph nodes (LNs) are positioned strategically throughout the body as critical mediators of lymph filtration and immune response. Lymph carries cytokines, antigens, and cells to the downstream LNs, and their effective delivery to the correct location within the LN directly impacts the quality and quantity of immune response. Despite the importance of this system, the flow patterns in LN have never been quantified, in part because experimental characterization is so difficult.

METHODS AND RESULTS

To achieve a more quantitative knowledge of LN flow, a computational flow model has been developed based on the mouse popliteal LN, allowing for a parameter sensitivity analysis to identify the important system characteristics. This model suggests that about 90% of the lymph takes a peripheral path via the subcapsular and medullary sinuses, while fluid perfusing deeper into the paracortex is sequestered by parenchymal blood vessels. Fluid absorption by these blood vessels under baseline conditions was driven mainly by oncotic pressure differences between lymph and blood, although the magnitude of fluid transfer is highly dependent on blood vessel surface area. We also predict that the hydraulic conductivity of the medulla, a parameter that has never been experimentally measured, should be at least three orders of magnitude larger than that of the paracortex to ensure physiologic pressures across the node.

CONCLUSIONS

These results suggest that structural changes in the LN microenvironment, as well as changes in inflow/outflow conditions, dramatically alter the distribution of lymph, cytokines, antigens, and cells within the LN, with great potential for modulating immune response.

Spaceflight-Relevant Challenges of Radiation and/or Reduced Weight Bearing Cause Arthritic Responses in Knee Articular Cartilage

There is little known about the effect of both reduced weight bearing and exposure to radiation during spaceflight on the mechanically-sensitive cartilage lining the knee joint. In this study, we characterized cartilage damage in rat knees after periods of reduced weight bearing with/without exposure to solar-flare-relevant radiation, then cartilage recovery after return to weight bearing. Male Sprague Dawley rats (n = 120) were either hindlimb unloaded (HLU) via tail suspension or remained weight bearing in cages (GROUND). On day 5, half of the HLU and GROUND rats were 1 Gy total-body X-ray irradiated during HLU, and half were sham irradiated (SHAM), yielding 4 groups: GROUND-SHAM; GROUND-IR; HLU-SHAM; and HLU-IR. Hindlimbs were collected from half of each group of rats on day 13. The remaining rats were then removed from HLU or remained weight bearing, and hindlimbs from these rats were collected on day 62. On day 13, glycosaminoglycan (GAG) content in cartilage lining the tibial plateau and femoral condyles of HLU rats was lower than that of the GROUND animals. Likewise, on day 13, immunoreactivity of the collagen type II-degrading matrix metalloproteinase-13 (MMP-13) and of a resultant metalloproteinase-generated neoepitope VDIPEN was increased in all groups versus GROUND-SHAM. Clustering of chondrocytes indicating cartilage damage was present in all HLU and IR groups versus GROUND-SHAM on day 13. On day 62, after 49 days of reloading, the loss of GAG content was attenuated in the HLU-SHAM and HLU-IR groups, and the increased VDIPEN staining in all treatment groups was attenuated. However, the increased chondrocyte clustering remained in all treatment groups on day 62. MMP-13 activity also remained elevated in the GROUND-IR and HLU-IR groups. Increased T2 relaxation times, measured on day 62 using 7T MRI, were greater in GROUND-IR and HLU-IR knees, indicating persistent cartilage damage in the irradiated groups. Both HLU and total-body irradiation resulted in acute degenerative and pre-arthritic changes in the knee articular cartilage of rats. A return to normal weight bearing resulted in some recovery from cartilage degradation. However, radiation delivered as both a single challenge and when combined with HLU resulted in chronic cartilage damage. These findings suggest that radiation exposure during spaceflight leads to and/or impairs recovery of cartilage upon return to reloading, generating long-term joint problems for astronauts.

Microbial ecology of the cystic fibrosis lung: does microflora type influence microbial loading?

This study aims to examine the association between the numbers of culturable microbial species forming the microflora of the lung in patients with cystic fibrosis (CF) and microbial loading (i.e., type[s] versus numbers). Additionally, it examines qualitative combinations of the microflora present in a large adult CF centre (n=138) in order to ascertain ecological relationships between the taxa present. The culturable microflora of sputum from 34 adults patients with CF are enumerated using a spread plate technique on non-selective agar, and the microflora identified phenotypically employing the API 20NE scheme. Microbiological examination of the 34 adult patients demonstrated that their sputum contained between one and three taxa, with a mean cell density of 8.25 +/- 0.85 log colony-forming units (cfu)/g sputum and a range of 5.91-9.74 log cfu/g sputum. Most colonising patterns demonstrated only Gram-negative infection (22/34), followed by a mixed Gram-positive/Gram-negative infection pattern (10/34). Only 2/34 patients had a single Gram-positive infection. Most patients (53%) were colonised by only one organism, with 38% of patients colonised by two organisms, and the remainder (4%) colonised with three organisms. There was no statistical difference (P>0.05) between microbial cell density and the number of taxa present (i.e., the greater number of taxa present in sputum did not produce a higher cell density). However, there was a significantly higher cell density (log 0.59 cfu/g sputum) noted for those patients who had only Gram-negative infection, compared to those who had a mixed Gram-negative/Gram-positive infection pattern (P=0.02). Relatively little is known about the ecological interactions that exist between the microflora in the CF lung. Further work is required to explore these interactions in order to aid understanding of the succession and dominance of Gram-negatives in chronic chest infections. Ultimately, a greater understanding of such interactions may allow the opportunity to manipulate the ecology of the lung to control otherwise problematic pathogens

Cloning, sequencing and molecular characterisation of a cryptic plasmid from a urease-positive thermophilic Campylobacter (UPTC) isolate

Cloning, sequencing and molecular characterisation of a cryptic plasmid, pUPTC237, from a urease-positive thermophilic Campylobacter (UPTC) isolate obtained from the natural environment in Northern Ireland is reported in this study. Based on the determined DNA sequence, the pUPTC237 DNA was identified as a circular molecule of 3828 bp with a G+C content of 29.5%. As with other plasmid DNAs from Gram-negative bacteria, pUPTC237 contained an A+T-rich region (A+T content: 95%), followed by multiple direct tandem repeat units of 22 bp, characteristic of a replication origin and iteron sequence. A possible open reading frame (ORF)-1 was located upstream of the A+T-rich region and the iteron sequence that encoded a 460 amino acid protein similar to the mobilisation (mob) protein and two putative promoter structure sequences at the -35 and -10 regions and a possible ribosome binding site occurred upstream of the start codon for the ORF-1. Moreover, three possible ORFs (a short ORF-2 encoding 26 amino acids, similar to repA; an ORF-3 encoding 341 amino acids, similar to repB; and an ORF-4 encoding 96 amino acids with unknown function) were also identified. There are also two putative promoter structures for these three ORFs at the -35 and -10 regions upstream of the possible ORF-2. A possible transcription termination region was identified downstream of ORF-4. Northern blot hybridisation analysis suggested that these four ORFs constitute an operon and generate a messenger RNA (mRNA) transcript.