Inquilinus limosus isolated from a cystic fibrosis patient: first UK report

Rarely Encountered Gram-Negative Rods and Lung Transplant Recipients: A Narrative Review

The respiratory tract of lung transplant recipients (LTR) is likely to be colonized with non-fermentative Gram-negative rods. As a consequence of the improvements in molecular sequencing and taxonomy, an increasing number of bacterial species have been described. We performed a review of the literature of bacterial infections in LTR involving non-fermentative Gram-negative rods with exclusion of Pseudomonas aeruginosa, Stenotrophomonas maltophilia, Achromobacter spp. and Burkholderia spp. Overall, non-fermenting GNR were recovered from 17 LTR involving the following genera: Acetobacter, Bordetella, Chryseobacterium, Elizabethkinga, Inquilinus, and Pandoraea. We then discuss the issues raised by these bacteria, including detection and identification, antimicrobial resistance, pathogenesis, and cross-transmission.

Inquilinus limosus isolated from a patient with chronic cystic fibrosis. First report in Mexico and evidence that co-infection with Pseudomonas aeruginosa promotes the accelerated and increased formation of extracellular neutrophil traps

Cystic fibrosis is characterized by abnormal mucous secretions in the lungs that favor the proliferation of colonizing bacteria, with Pseudomonas aeruginosa and Staphylococcus aureus being the most isolated, however, other less known species could also have an impact on the health of the patient. Here we demonstrate the isolation and antibiotic resistance profiles of Inquilinus limosus, a rarely reported multidrug resistant bacterium, and compare them to a co-infectant strain of Pseudomonas aeruginosa. Likewise, we found that co-infection with both bacteria promotes increased formation of neutrophil extracellular traps, which can have an impact on the disease severity and make treatment difficult.

Clinical characteristics and outcomes associated with Inquilinus infection in cystic fibrosis

BACKGROUND

Molecular diagnostics have led to the identification of a broad range of bacterial species in cystic fibrosis (CF) including Inquilinus. The clinical significance of Inquilinus in CF has not been thoroughly characterized.

METHODS

Retrospective, case-control study of persons with CF from two CF centers with at least one respiratory culture positive for Inquilinus spp. compared with age-matched CF controls with chronic Pseudomonas aeruginosa. Percent predicted forced expiratory volume in one second (ppFEV1) and body mass index percentile (BMI) were modeled from time of first positive culture up to 5 years later. Rates of pulmonary exacerbations were compared. Inquilinus isolates were genotyped to evaluate strain diversity.

RESULTS

Seventeen patients with Inquilinus infection were identified with a mean age of 13 years at first positive culture. Most cases had multiple cultures positive for Inquilinus. ppFEV1 was not different between cases versus controls (80.2% vs 81.6%, p = 0.97 at baseline, 67.5% vs. 73.3%, p = 0.82 at 5 years). Patients were undernourished and BMI percentiles did not differ between groups (30.7% vs 43.4%, p = 0.32 at baseline, 37.9% vs. 37.6%, p = 0.98 at 5 years). There was no difference in the pulmonary exacerbation rate (3.0/year vs 2.5/year, p = 0.34). Genotyping showed diverse genetic strains between patients.

CONCLUSIONS

Inquilinus can present in childhood and is often associated with chronic infection in CF. Lung function and nutrition status at time of detection, lung function decline, and pulmonary exacerbation rates in Inquilinus cases were similar to those with chronic P. aeruginosa, a well-established CF pathogen.

Discriminating typical and atypical cystic fibrosis-related bacteria by multiplex PNA-FISH

This study aims to report the development of peptide nucleic acid (PNA) probes to specifically detect the cystic fibrosis (CF)-associated traditional and atypical species Pseudomonas aeruginosa and Inquilinus limosus, respectively. PNA probes were designed in silico, developed and tested in smears prepared in phosphate-buffer saline (PBS), and in artificial sputum medium (ASM). A multiplex fluorescent in situ hybridization (FISH) approach using the designed probes was further validated in artificially contaminated clinical sputum samples and also applied in polymicrobial 24 h-old biofilms involving P. aeruginosa, I. limosus, and other CF-related bacteria. Both probes showed high predictive and experimental specificities and sensitivities. The multiplex PNA-FISH assay, associated with non-specific staining, was successfully adapted in the clinical samples and in biofilms of CF-related bacteria, allowing differentiating the community members and inferring about microbial-microbial interactions within the consortia. This study revealed the great potential of PNA-FISH as a diagnostic tool to discriminate between classical and less common CF-associated bacteria, being suitable to further describe species-dependent prevention strategies and deliver more effective target control therapeutics. Biotechnol. Bioeng. 2017;114: 355-367. © 2016 Wiley Periodicals, Inc.

Mucoid Inquilinus limosus in a young adult with cystic fibrosis

Inquilinus limosus is a alpha-proteobacterium that has been recently isolate in the airways of cystic fibrosis (CF) patients. We report the isolation of a mucoid strain of I. limosus from the sputum of a 20-year-old male patient with CF over 1 year that was associated with the clinical, spirometric, and radiographic decline in a previously healthy patient.

Molecular detection of multiple emerging pathogens in sputa from cystic fibrosis patients

Background

There is strong evidence that culture-based methods detect only a small proportion of bacteria present in the respiratory tracts of cystic fibrosis (CF) patients.

Methodology/Principal Findings

Standard microbiological culture and phenotypic identification of bacteria in sputa from CF patients have been compared to molecular methods by the use of 16S rDNA amplification, cloning and sequencing. Twenty-five sputa from CF patients were cultured that yield 33 isolates (13 species) known to be pathogens during CF. For molecular cloning, 760 clones were sequenced (7.2±3.9 species/sputum), and 53 different bacterial species were identified including 16 species of anaerobes (30%). Discrepancies between culture and molecular data were numerous and demonstrate that accurate identification remains challenging. New or emerging bacteria not or rarely reported in CF patients were detected including Dolosigranulum pigrum, Dialister pneumosintes, and Inquilinus limosus.

Conclusions/Significance

Our results demonstrate the complex microbial community in sputa from CF patients, especially anaerobic bacteria that are probably an underestimated cause of CF lung pathology. Metagenomic analysis is urgently needed to better understand those complex communities in CF pulmonary infections.