Highly Diversified Pandoraea pulmonicola Population during Chronic Colonization in Cystic Fibrosis

Achromobacter xylosoxidans and Stenotrophomonas maltophilia: Emerging Pathogens Well-Armed for Life in the Cystic Fibrosis Patients' Lung

In patients with cystic fibrosis (CF), the lung is a remarkable ecological niche in which the microbiome is subjected to important selective pressures. An inexorable colonization by bacteria of both endogenous and environmental origin is observed in most patients, leading to a vicious cycle of infection–inflammation. In this context, long-term colonization together with competitive interactions among bacteria can lead to over-inflammation. While Pseudomonas aeruginosa and Staphylococcus aureus, the two pathogens most frequently identified in CF, have been largely studied for adaptation to the CF lung, in the last few years, there has been a growing interest in emerging pathogens of environmental origin, namely Achromobacter xylosoxidans and Stenotrophomonas maltophilia. The aim of this review is to gather all the current knowledge on the major pathophysiological traits, their supporting mechanisms, regulation and evolutionary modifications involved in colonization, virulence, and competitive interactions with other members of the lung microbiota for these emerging pathogens, with all these mechanisms being major drivers of persistence in the CF lung. Currently available research on A. xylosoxidans complex and S. maltophilia shows that these emerging pathogens share important pathophysiological features with well-known CF pathogens, making them important members of the complex bacterial community living in the CF lung.

Fatal Pandoraea nosoerga infection after combined liver-lung transplantation for cystic fibrosis: a recontamination by the pre-transplantation strain

A 26-year-old girl with a longstanding colonization by Pandoraea nosoerga underwent liver-lung transplantation for cystic fibrosis (CF) in 2018. Her brother also suffering from CF was also colonized by P. nosoerga. Despite appropriate perioperative antibiotic therapy, she had post-transplant bacteremic pneumonia caused by extensively drug-resistant P. nosoerga. Drug repurposing was used to optimize treatment options. The cause of post-transplant contamination was studied by comparative whole-genome sequencing including pre- and post-transplant strains and her brother's strains. Post-transplant contamination appeared to be due to her own pre-transplant strain, emphasizing the urgent need to study and implement effective decontamination protocols before transplantation.

High Occurrence of Bacterial Competition Among Clinically Documented Opportunistic Pathogens Including Achromobacter xylosoxidans in Cystic Fibrosis

Cystic Fibrosis (CF) airways favor abnormal microbial development. Infections are considered as polymicrobial and competition can be observed between microorganisms. The current literature on bacterial competition in CF mostly consists of studies with limited numbers of strains, mainly focused on the major pathogens Pseudomonas aeruginosa (Pa) and Staphylococcus aureus (Sa) and does not give a comprehensive overview of the overall importance of bacterial interactions or the behavior of less often encountered emerging bacteria such as Achromobacter. In this context, we screened a panel of 39 strains from six CF patients, of either clinical or domestic environmental origin, distinguished according to genotype and belonging to four opportunistic pathogens, Pa (n = 15), Sa (n = 3), Stenotrophomonas maltophilia (Sm, n = 10) and Achromobacter xylosoxidans (Ax, n = 11). We investigated their capacity to compete in terms of growth, motility, and pigment production on agar media through 203 crossing experiments. Eleven strains selected via the initial screening results were further studied for competitive growth in liquid medium and biofilm formation. Competition was noted for 33% (67/203) of the pairs of strains with 85 modifications observed between monocultures and co-cultures, impacting growth (23.6%), motility (13.8%), and/or pigment production (6.1%). Under all conditions of the study (clinical, environmental strains; intra-, inter-patients; intra-, inter-species levels), competition was significantly more frequent among pairs of strains with at least one clinical strain. While Pa mainly outcompeted other species, in one patient with chronic colonization by Ax and sporadic colonization by Pa, we showed that some Ax inhibited the growth and pigmentation of Pa whereas biofilm formation was drastically reduced. Enlarging the panel of strains tested in competition assays gave new perspectives on the complex interactions taking place among the CF airway community. Indeed, the frequent occurrence of varied, strain-dependent interactions is revealed here. We report the first results of competition assays for Ax with the ability of certain strains to outcompete Pa. Our results are linked to the patient’s colonization history and question the importance of bacterial competitiveness in the colonization pattern of CF airways.

[Emerging bacteria in cystic fibrosis and non-cystic fibrosis bronchiectasis from a microbiologist's perspective]

INTRODUCTION

Common major pathogens like Pseudomonas aeruginosa are identified in the airways of patients with cystic fibrosis (CF) and non-CF bronchiectasis. However, other opportunistic bacterial pathogens like Achromobacter xylosoxidans complex, Stenotrophomonas maltophilia and non-tuberculous mycobacteria are currently emerging in CF and are also reported in non-CF bronchiectasis.

BACKGROUND

The emergence of opportunistic bacterial pathogens has been recognized in CF through annual national reports of sputum microbiology data. Despite common factors driving the emergence of bacteria identified in CF and non-CF bronchiectasis patients, bronchiectasis registries have been created more recently and no longitudinal analysis of recorded microbiological data is currently available in the literature, thereby preventing the recognition of emerging bacteria in patients with non-CF bronchiectasis.

OUTLOOK

A longitudinal follow-up of microbiological data is still needed in non-CF bronchiectasis to identify emerging opportunistic bacterial pathogens. Homogeneity in practice of sputum microbiological examination is also required to allow comparative analysis of data in CF and non-CF bronchiectasis.

CONCLUSION

Bacterial pathogens recognized as emerging in CF have to be more carefully monitored in non-CF bronchiectasis in view of their association with deterioration of the lung disease.

Whole-genome analysis of Pandoraea species strains from cystic fibrosis patients

Aim: Genetic characterization of Pandoraea strains recovered from cystic fibrosis patients. Materials & methods: The whole-genome sequence of 12 Pandoraea strains was determined using Illumina technology. The position of the strains within the genus Pandoraea was analyzed using selected partial gene sequences, core genome multi-locus sequence typing and average nucleotide identity analysis. Furthermore, the sequences were annotated. Results: The results show that some strains previously identified as Pandoraea pnomenusa, Pandoraea sputorum, Pandoraea oxalativorans and Pandoraea pulmonicola belong to novel species. The strains did not harbor acquired antibiotic resistance genes but encoded an OXA-type ß-lactamase. Conclusion: The taxonomy of the genus Pandoraea needs to be revised.

Comparative Genomics of Pandoraea, a Genus Enriched in Xenobiotic Biodegradation and Metabolism

Comparative analysis of partial gyrB, recA, and gltB gene sequences of 84 Pandoraea reference strains and field isolates revealed several clusters that included no taxonomic reference strains. The gyrB, recA, and gltB phylogenetic trees were used to select 27 strains for whole-genome sequence analysis and for a comparative genomics study that also included 41 publicly available Pandoraea genome sequences. The phylogenomic analyses included a Genome BLAST Distance Phylogeny approach to calculate pairwise digital DNA–DNA hybridization values and their confidence intervals, average nucleotide identity analyses using the OrthoANIu algorithm, and a whole-genome phylogeny reconstruction based on 107 single-copy core genes using bcgTree. These analyses, along with subsequent chemotaxonomic and traditional phenotypic analyses, revealed the presence of 17 novel Pandoraea species among the strains analyzed, and allowed the identification of several unclassified Pandoraea strains reported in the literature. The genus Pandoraea has an open pan genome that includes many orthogroups in the ‘Xenobiotics biodegradation and metabolism’ KEGG pathway, which likely explains the enrichment of these species in polluted soils and participation in the biodegradation of complex organic substances. We propose to formally classify the 17 novel Pandoraea species as P. anapnoica sp. nov. (type strain LMG 31117^T = CCUG 73385^T), P. anhela sp. nov. (type strain LMG 31108^T = CCUG 73386^T), P. aquatica sp. nov. (type strain LMG 31011^T = CCUG 73384^T), P. bronchicola sp. nov. (type strain LMG 20603^T = ATCC BAA-110^T), P. capi sp. nov. (type strain LMG 20602^T = ATCC BAA-109^T), P. captiosa sp. nov. (type strain LMG 31118^T = CCUG 73387^T), P. cepalis sp. nov. (type strain LMG 31106^T = CCUG 39680^T), P. commovens sp. nov. (type strain LMG 31010^T = CCUG 73378^T), P. communis sp. nov. (type strain LMG 31110^T = CCUG 73383^T), P. eparura sp. nov. (type strain LMG 31012^T = CCUG 73380^T), P. horticolens sp. nov. (type strain LMG 31112^T = CCUG 73379^T), P. iniqua sp. nov. (type strain LMG 31009^T = CCUG 73377^T), P. morbifera sp. nov. (type strain LMG 31116^T = CCUG 73389^T), P. nosoerga sp. nov. (type strain LMG 31109^T = CCUG 73390^T), P. pneumonica sp. nov. (type strain LMG 31114^T = CCUG 73388^T), P. soli sp. nov. (type strain LMG 31014^T = CCUG 73382^T), and P. terrigena sp. nov. (type strain LMG 31013^T = CCUG 73381^T).

Pneumonia due to Pandoraea Apista after evacuation of traumatic intracranial hematomas:a case report and literature review

Background

Pandoraea species is a newly described genus, which is multidrug resistant and difficult to identify. Clinical isolates are mostly cultured from cystic fibrosis (CF) patients. CF is a rare disease in China, which makes Pandoraea a total stranger to Chinese physicians. Pandoraea genus is reported as an emerging pathogen in CF patients in most cases. However, there are few pieces of evidence that confirm Pandoraea can be more virulent in non-CF patients. The pathogenicity of Pandoraea genus is poorly understood, as well as its treatment. The incidence of Pandoraea induced infection in non-CF patients may be underestimated and it’s important to identify and understand these organisms.

Case presentation

We report a 44-years-old man who suffered from pneumonia and died eventually. Before his condition deteriorated, a Gram-negative bacilli was cultured from his sputum and identified as Pandoraea Apista by matrix-assisted laser desorption ionization–time-of-flight mass spectrometry (MALDI-TOF MS).

Conclusion

Pandoraea spp. is an emerging opportunistic pathogen. The incidences of Pandoraea related infection in non-CF patients may be underestimated due to the difficulty of identification. All strains of Pandoraea show multi-drug resistance and highly variable susceptibility. To better treatment, species-level identification and antibiotic susceptibility test are necessary.