The dominant role of extracellular polymeric substances produced by Achromobacter xylosoxidans BP1 in Cr(VI) microbial reduction.

Extracellular polymeric substances (EPS) have demonstrated significant benefits for reducing multivalent metal contamination. Using Achromobacter xylosoxidans BP1 isolated from a coal chemical site in China, this study elucidated the contribution of EPS production to Cr (VI) reduction and revealed its biological removal mechanism. BP1 grew at an optimum pH of 8 and the lowest inhibitory concentration of Cr(VI) was 300 mg/L. The spent medium completely removed Cr(VI), whereas resting cells were only able to remove 10.47 % and inactivated cells were nearly incapable of Cr(VI) removal. S-EPS and B-EPS reduced Cr(VI) by 98.59 % and 11.64 %, respectively. SEM-EDS analysis showed that the BP1 cells were stimulated to produce EPS under Cr stress. The XPS results showed that 29.63 % of Cr(VI) was enriched by intracellular bioaccumulation or biosorption and 70.37 % of Cr(VI) was reduced by extracellular enzymes to produce Cr(OH)3 and organic Cr(III) complexes. According to FTIR, EPS with -OH, COO-, and amide groups supplied binding sites and electrons for the reductive adsorption of Cr(VI). Genomic studies showed that BP1 primarily produces extracellular polysaccharides, metabolises sulphur and nitrogen, and reduces reactive oxygen species damage as a result of DNA repair proteases.

Peanut Rhizosphere Achromobacter xylosoxidans Inhibits Aspergillus flavus Development and Aflatoxin Synthesis by Inducing Apoptosis through Targeting the Cell Membrane.

Contamination of crop seeds and feed with Aspergillus flavus and its associated aflatoxins presents a significant threat to human and animal health due to their hepatotoxic and carcinogenic properties. To address this challenge, researchers have screened for potential biological control agents in peanut soil and pods. This study identified a promising candidate, a strain of the nonpigmented bacterium, Achromobacter xylosoxidans ZJS2-1, isolated from the peanut rhizosphere in Zhejiang Province, China, exhibiting notable antifungal and antiaflatoxin activities. Further investigations demonstrated that ZJS2-1 active substances (ZAS) effectively inhibited growth at a MIC of 60 µL/mL and nearly suppressed AFB1 production by 99%. Metabolomic analysis revealed that ZAS significantly affected metabolites involved in cell wall and membrane biosynthesis, leading to compromised cellular integrity and induced apoptosis in A. flavus through the release of cytochrome c. Notably, ZAS targeted SrbA, a key transcription factor involved in ergosterol biosynthesis and cell membrane integrity, highlighting its crucial role in ZJS2-1's biocontrol mechanism. Moreover, infection of crop seeds and plant wilt caused by A. flavus can be efficiently alleviated by ZAS. Additionally, ZJS2-1 and ZAS demonstrated significant inhibitory effects on various Aspergillus species, with inhibition rates ranging from 80 to 99%. These findings highlight the potential of ZJS2-1 as a biocontrol agent against Aspergillus species, offering a promising solution to enhance food safety and protect human health.

Rare Pathogens in Peritoneal Dialysis-Associated Peritonitis: A Comprehensive Case Study and Guideline Review.

BACKGROUND Peritoneal dialysis (PD) serves as a critical renal replacement therapy for individuals with end-stage renal disease (ESRD), leveraging the peritoneum for fluid and substance exchange. Despite its effectiveness, PD is marred by complications such as peritonitis, which significantly impacts patient outcomes. The novelty of our report lies in the presentation of a rare case of PD-associated peritonitis caused by 2 unusual pathogens, emphasizing the importance of rigorous infection control measures. CASE REPORT We report on an 80-year-old African-American female patient with ESRD undergoing PD, who was admitted twice within 8 months for non-recurring episodes of peritonitis. These episodes were attributed to the rare pathogens Achromobacter denitrificans/xylosoxidans and Carbapenem-resistant Acinetobacter baumannii. Despite presenting with similar symptoms during each episode, such as abdominal pain and turbid dialysis effluent, the presence of these uncommon bacteria highlights the intricate challenges in managing infections associated with PD. The treatment strategy encompassed targeted antibiotic therapy, determined through susceptibility testing. Notably, the decision to remove the PD catheter followed extensive patient education, ensuring the patient comprehended the rationale behind this approach. This crucial step, along with the subsequent shift to hemodialysis, was pivotal in resolving the infection, illustrating the importance of patient involvement in the management of complex PD-related infections. CONCLUSIONS This case underscores the complexities of managing PD-associated peritonitis, particularly with uncommon and resistant bacteria. It emphasizes the importance of rigorous infection control measures, the need to consider atypical pathogens, and the critical role of patient involvement in treatment decisions. Our insights advocate for a more informed approach to handling such infections, aiming to reduce morbidity and improve patient outcomes. The examination of the literature on recurrent peritonitis and treatment strategies provides key perspectives for navigating these challenging cases effectively.

Integrating 16S rRNA profiling and in-silico analysis for an epitope-based vaccine strategy against Achromobacter xylosoxidans infection.

Achromobacter xylosoxidans is an aerobic, catalase-positive, non-pigment-forming, Gram-negative, and motile bacterium. It potentially causes a wide range of human infections in cystic fibrosis and non-cystic fibrosis patients. However, developing a safe preventive or therapeutic solution against A. xylosoxidans remains challenging. This study aimed to construct an epitope-based vaccine candidate using immunoinformatic techniques. A. xylosoxidans was isolated from an auto workshop in Lahore, and its identification was confirmed through 16S rRNA amplification and bioinformatic analysis. Two protein targets with GenBank accession numbers AKP90890.1 and AKP90355.1 were selected for the vaccine construct. Both proteins exhibited antigenicity, with scores of 0.757 and 0.580, respectively and the epitopes were selected based on the IC50 value using the ANN 4.0 and NN-align 2.3 epitope prediction method for MHC I and MHC II epitopes respectively and predicted epitopes were analyzed for antigenicity, allergenicity and pathogenicity. The vaccine construct demonstrated structural stability, thermostability, solubility, and hydrophilicity. The vaccine produced 250 B-memory cells per mm3 and approximately 16,000 IgM + IgG counts, indicating an effective immune response against A. xylosoxidans. Moreover, the vaccine candidate interacted stably with toll-like receptor 5, a pattern recognition receptor, with a confidence score of 0.98. These results highlight the potency of the designed vaccine candidate, suggesting its potential to withstand rigorous in vitro and in vivo clinical trials. This epitope-based vaccine could serve as the first preventive immunotherapy against A. xylosoxidans infections, addressing this bacterium's health and financial burdens. The findings demonstrate the value of employing immunoinformatic tools in vaccine development, paving the way for more precise and tailored approaches to combating microbial threats.

Biodegradation of polystyrene nanoplastics by Achromobacter xylosoxidans M9 offers a mealworm gut-derived solution for plastic pollution.

Nanoplastics pose significant environmental problems due to their high mobility and increased toxicity. These particles can cause infertility and inflammation in aquatic organisms, disrupt microbial signaling and act as pollutants carrier. Despite extensive studies on their harmful impact on living organisms, the microbial degradation of nanoplastics is still under research. This study investigated the degradation of nanoplastics by isolating bacteria from the gut microbiome of Tenebrio molitor larvae fed various plastic diets. Five bacterial strains capable of degrading polystyrene were identified, with Achromobacter xylosoxidans M9 showing significant nanoplastic degradation abilities. Within 6 days, this strain reduced nanoplastic particle size by 92.3%, as confirmed by SEM and TEM analyses, and altered the chemical composition of the nanoplastics, indicating a potential for enhanced bioremediation strategies. The strain also caused a 7% weight loss in polystyrene film over 30 days, demonstrating its efficiency in degrading nanoplastics faster than polystyrene film. These findings might enhance plastic bioremediation strategies.

Achromobacter xylosoxidans keratitis in a LASIK flap treated with intrastromal antibiotics: a case report.

Intrastromal antibiotic injections are a type of treatment that can be very useful in bacterial keratitis refractory to topical antibiotics. We present the case of a 44-year-old woman with an infiltrate in a laser in situ keratomiuleusis (LASIK) flap and growth of Achromobacter xylosoxidans, who was treated with topical ceftazidime for 1 month. However, after discontinuation of the antibiotic, there was a worsening with growth of the same germ. Topical treatment was reintroduced and, due to suspicion of germ reservoir, it was decided to give three cycles of intrastromal ceftazidime injections, the last one also with moxifloxacin, with good results. After 4 months asymptomatic and without treatment at the moment, no signs of recurrence have been observed. This case supports the usefulness of intraestromal injections in refractory cases to the topical medication.

Prevalence and variability of siderophore production in the Achromobacter genus.

Achromobacter spp. are opportunistic pathogens of environmental origin increasingly isolated in patients with underlying conditions like cystic fibrosis (CF). Despite recent advances, their virulence factors remain incompletely studied, and siderophore production has not yet been investigated in this genus. The aim of this study was to evaluate the production of siderophores in a large collection of Achromobacter spp. and evaluate the variability according to the origin of the strain and species. A total of 163 strains were studied, including 128 clinical strains (CF and non-CF patients) and 35 strains of environmental origin. Siderophores were quantified by the liquid chrome azurol-sulphonate assay. Species were identified by nrdA gene-based phylogeny. Strains were assigned to 20 species, with Achromobacter xylosoxidans being the most represented (51.5% of strains). Siderophore production was observed in 72.4% of the strains, with amounts ranging from 10.1% to 90% siderophore units. A significantly higher prevalence of siderophore-producing strains and greater production of siderophores were observed for clinical strains compared with strains of environmental origin. Highly variable observations were made according to species: A. xylosoxidans presented unique characteristics (one of the highest prevalence of producing strains and highest amounts produced, particularly by CF strains). Siderophores are important factors for bacterial growth commonly produced by members of the Achromobacter genus. The significance of the observations made during this study must be further investigated. Indeed, the differences observed according to species and the origin of strains suggest that siderophores may represent important determinants of the pathophysiology of Achromobacter spp. infections and also contribute to the particular epidemiological success of A. xylosoxidans in human infections. IMPORTANCE: Achromobacter spp. are recognized as emerging opportunistic pathogens in humans with various underlying diseases, including cystic fibrosis (CF). Although their pathophysiological traits are increasingly studied, their virulence factors remain incompletely described. Particularly, siderophores that represent important factors of bacterial growth have not yet been studied in this genus. A population-based study was performed to explore the ability of members of the Achromobacter genus to produce siderophores, both overall and in relevant subgroups (Achromobacter species; strain origin, either clinical-from CF or non-CF patients-or environmental). This study provides original data showing that siderophore production is a common trait of Achromobacter strains, particularly observed among clinical strains. The major species, Achromobacter xylosoxidans, encompassed both one of the highest prevalence of siderophore-producing strains and strains producing the largest amounts of siderophores, particularly observed for CF strains. These observations may represent additional advantages accounting for the epidemiological success of this species.

Chronic otorrhea and osteomyelitis of the external auditory canal by Achromobacter xylosoxidans: an uncommon diagnosis.

PURPOSE: Achromobacter xylosoxidans is an emerging pathogen mainly associated with resistant nosocomial infections. This bacteria had been isolated in the ear together with other pathogens in cultures from patients with chronic otitis media, but it had never been reported as a cause of osteomyelitis of the external auditory canal. CASE PRESENTATION: We present a unique case of a healthy 81-year-old woman who presented with left chronic otorrhea refractory to topical and oral antibiotic treatment. Otomicroscopy revealed an erythematous and exudative external auditory canal (EAC) with scant otorrhea. The tympanic membrane was intact, but an area of bone remodeling with a small cavity anterior and inferior to the bony tympanic frame was observed. Otic culture isolated multi-drug-resistant A. xylosoxidans, only sensitive to meropenem and cotrimoxazole. Temporal bone computed tomography showed an excavation of the floor of the EAC compatible with osteomyelitis. Targeted antibiotherapy for 12 weeks was conducted, with subsequent resolution of symptoms and no progression of the bone erosion. CONCLUSIONS: Atypical pathogens such as A. xylosoxidans can be the cause of chronic otitis externa. Early diagnosis and specific antibiotherapy can prevent the development of further complications, such as osteomyelitis. In these cases, otic cultures play an essential role to identify the causal germ. This is the first case of EAC osteomyelitis due to A. xylosoxidans reported to date.

Achromobacter pneumonia in a patient with advanced COPD, a diagnostic challenge.

Bacterial pneumonia causes significant morbidity and mortality especially in elderly and immunocompromised hosts. Achromobacter xylosoxidans denitrificans pneumonia is very rarely reported. However, the reported cases have been in patients who are either immunocompromised or have bronchiectasis. We hereby present a unique case of Achromobacter xylosoxidans denitrificans pneumonia in an immunocompetent patient with advanced chronic obstructive pulmonary disease (COPD). Our patient is a Caucasian male admitted with shortness of breath, fever and cough. Chest X-ray demonstrated right-sided infiltrates and he was treated with intravenous ceftriaxone and azithromycin. He was discharged home on oral amoxicillin-clavulanate 875-125 mg two times per day for a total of 7 days. Patient returned to emergency room after 5 weeks with persistent symptoms and chest X-ray revealed persistent right-sided infiltrate and sputum culture showed Achromobacter xylosoxidans denitrificans. The patient was started on oral levofloxacin 750 mg one time per day for 2 weeks with resolution of symptoms.

Performance evaluation of Bruker UMIC® microdilution panel and disc diffusion to determine cefiderocol susceptibility in Enterobacterales, Acinetobacter baumannii, Pseudomonas aeruginosa, Stenotrophomonas maltophilia, Achromobacter xylosoxidans and Burkolderia species.

PURPOSE: Cefiderocol susceptibility testing (AST) represents an open challenge for clinical microbiology. Herein, we evaluated the performance of the UMIC® Cefiderocol broth microdilution (BMD) test and disc diffusion on Gram-negative species. METHODS: UMIC® Cefiderocol BMD test, disc diffusion and reference BMD were in parallel performed on a collection of 256 clinical isolates. Categorical agreement (CA), essential agreement (EA), bias, major errors (MEs) and very major errors (VMEs) were calculated for both AST methods. RESULTS: The UMIC® Cefiderocol BMD strip exhibited an EA < 90% (85.5%), a CA higher than 90% (93.7%) and a low number of VMEs (n = 4, 4.2%) and MEs (n = 12, 7.4%). UMIC® Cefiderocol identified 96.2% of the resistant isolates [Enterobacterales, (39/40); P. aeruginosa (19/19); A. xylosoxidans (5/6); S. maltophilia (5/6); Burkholderia spp. (8/8)]. Disc diffusion showed a high CA (from 94.9 to 100%) regardless of disc manufacturer in Enterobacterales, P. aeuroginosa, A. baumannii and S. maltophilia. However, high rates of results falling in the area of technical uncertainty (ATU) were observed in Enterobacterales (34/90, 37.8%) and P. aeruginosa (16/40, 40%). Disc diffusion showed a poor performance in A. xylosoxidans and Burkholderia spp. if PK/PD breakpoint was used (overall, 5/9 VMEs; in contrast, the use of P. aeruginosa-specific breakpoints resulted in 100% of CA with 24.6% of results in the ATU). CONCLUSION: In conclusion, disc diffusion and UMIC® Cefiderocol are valid methods for the determination of cefiderocol susceptibility. Given the high number of results in the ATU by disc diffusion, a combined use of both AST methods may represent a solution to overcome the challenge of cefiderocol susceptibility testing in routine microbiology laboratories.

Peritoneal Dialysis-Associated Peritonitis Caused by Achromobacter xylosoxidans: A Case Report and Literature Review.

Achromobacter xylosoxidans is a gram-negative bacterium that is responsible for rare peritonitis associated with peritoneal dialysis (PD). We present a case of a 64-year-old woman with a medical history of end-stage renal disease undergoing PD who was admitted to the emergency department with abdominal pain and nausea. Physical examination and laboratory studies revealed peritoneal signs and laboratory abnormalities consistent with peritonitis. Intraperitoneal catheter dysfunction was identified and subsequently resolved via laparoscopy. Following a peritoneal fluid culture, A xylosoxidans was identified, leading to the initiation of intraperitoneal meropenem treatment. After an initial improvement, the patient developed an ileus and recurrent abdominal symptoms, and further peritoneal cultures remained positive for A xylosoxidans. Subsequent treatment included intravenous meropenem and vancomycin for Clostridium difficile colitis. Owing to the high likelihood of biofilm formation on the PD catheter by A xylosoxidans, the catheter was removed, and the patient transitioned to hemodialysis. Intravenous meropenem was continued for 2 weeks post-catheter removal. This case highlights the challenges in managing recurrent peritonitis in PD patients caused by multidrug-resistant A xylosoxidans. A high index of suspicion, appropriate microbiological identification, and targeted intraperitoneal and systemic antibiotic treatment, along with catheter management, are crucial in achieving a favorable outcome in such cases.

Pathogenesis of Achromobacter xylosoxidans respiratory infections: colonization, persistence, and transcriptome profiling in synthetic cystic fibrosis sputum medium.

Cystic fibrosis (CF) is a genetic disease affecting epithelial ion transport, resulting in thickened mucus and impaired mucociliary clearance. Persons with CF (pwCF) experience life-long infections of the respiratory mucosa caused by a diverse array of opportunists, which are leading causes of morbidity and mortality. In recent years, there has been increased appreciation for the range and diversity of microbes causing CF-related respiratory infections. The introduction of new therapeutics and improved detection methodology has revealed CF-related opportunists such as Achromobacter xylosoxidans (Ax). Ax is a Gram-negative bacterial species which is widely distributed in environmental sources and has been increasingly observed in sputa and other samples from pwCF, typically in patients in later stages of CF disease. In this study, we characterized CF clinical isolates of Ax and tested colonization and persistence of Ax in respiratory infection using immortalized human CF respiratory epithelial cells and BALB/c mice. Genomic analyses of clinical Ax isolates showed homologs for factors including flagellar synthesis, antibiotic resistance, and toxin secretion systems. Ax isolates adhered to polarized cultures of CFBE41o- human immortalized CF bronchial epithelial cells and caused significant cytotoxicity and depolarization of cell layers. Ax colonized and persisted in mouse lungs for up to 72 h post infection, with inflammatory consequences that include increased neutrophil influx in the lung, lung damage, cytokine production, and mortality. We also identified genes that are differentially expressed in synthetic CF sputum media. Based on these results, we conclude that Ax is an opportunistic pathogen of significance in CF.

New report of endophytic bacterium Achromobacter xylosoxidans from root tissue of Musa spp.

BACKGROUND: Cavendish (AAA) banana plant (Musa spp.) worldwide cultivated crop harbors many endophytic bacteria. Endophytic bacteria are those that live inside plant tissues without producing any visible symptoms of infection. RESULTS: Endophytic bacterium (MRH 11), isolated from root tissue of Musa spp.was identified as Achromobacter xylosoxidans (ON955872) which showed positive effects in IAA production, phosphate solubilization, catalase production. A. xylosoxidans also showed in vitro antagonism against Curvularia lunata causing leaf spot disease of Cavendish (AAA) banana (G-9 variety). The GC-MS analysis of culture filtrate of A. xylosoxidans (ON955872) confirmed this finding. GC-MS analysis was carried by using two solvent etheyl acetate and chloroform and it showed several antifungal compounds. The identification of these bioactive secondary metabolites compounds was based on the peak area, retention time, molecular weight, molecular formula and antimicrobial actions. GC-MS analysis result revealed the presence of major components including Cyclododecane, 1-Octanol, Cetene, Diethyl phthalate. In vivo test to banana plants was carried out in separate field as well as in potted conditions. Appearance of leaf spots after foliar spray of spore of pathogen and reduction in leaf spots after application of bacterial suspension was found. CONCLUSION: The present study has highlighted the role of endophytic bacterium as antagonist to the pathogen Curvularia lunata.

Development of a plastic waste treatment process by combining deep eutectic solvent (DES) pretreatment and bioaugmentation with a plastic-degrading bacterial consortium.

Polyethylene terephthalate (PET), a petroleum-based plastic, and polylactic acid (PLA), a biobased plastic, have a similar visual appearance thus they usually end up in municipal waste treatment facilities. The objective of this project was to develop an effective PET and PLA waste treatment process that involves pretreatment with deep eutectic solvent (DES) followed by biodegradation with a plastic-degrading bacterial consortium in a composting system. The DES used was a mixture of choline chloride and glycerol, while the bacterial strains (Chitinophaga jiangningensis EA02, Nocardioides zeae EA12, Stenotrophomonas pavanii EA33, Gordonia desulfuricans EA63, Achromobacter xylosoxidans A9 and Mycolicibacterium parafortuitum J101) used to prepare the bacterial consortium were selected based on their ability to biodegrade PET, PLA, and plasticizer. The plastic samples (a PET bottle, PLA cup, and PLA film) were pretreated with DES through a dip-coating method. The DES-coated plastic samples exhibited higher surface wettability and biofilm formation, indicating that DES increases the hydrophilicity of the plastic and facilitates bacterial attachment to the plastic surface. The combined action of DES pretreatment and bioaugmentation with a plastic-degrading bacterial consortium led to improved degradation of PET and PLA samples in various environments, including aqueous media at ambient temperature, lab-scale traditional composting, and pilot-scale composting.

Compounding Achromobacter Phages for Therapeutic Applications.

Achromobacter species colonization of Cystic Fibrosis respiratory airways is an increasing concern. Two adult patients with Cystic Fibrosis colonized by Achromobacter xylosoxidans CF418 or Achromobacter ruhlandii CF116 experienced fatal exacerbations. Achromobacter spp. are naturally resistant to several antibiotics. Therefore, phages could be valuable as therapeutics for the control of Achromobacter. In this study, thirteen lytic phages were isolated and characterized at the morphological and genomic levels for potential future use in phage therapy. They are presented here as the Achromobacter Kumeyaay phage collection. Six distinct Achromobacter phage genome clusters were identified based on a comprehensive phylogenetic analysis of the Kumeyaay collection as well as the publicly available Achromobacter phages. The infectivity of all phages in the Kumeyaay collection was tested in 23 Achromobacter clinical isolates; 78% of these isolates were lysed by at least one phage. A cryptic prophage was induced in Achromobacter xylosoxidans CF418 when infected with some of the lytic phages. This prophage genome was characterized and is presented as Achromobacter phage CF418-P1. Prophage induction during lytic phage preparation for therapy interventions require further exploration. Large-scale production of phages and removal of endotoxins using an octanol-based procedure resulted in a phage concentrate of 1 × 109 plaque-forming units per milliliter with an endotoxin concentration of 65 endotoxin units per milliliter, which is below the Food and Drugs Administration recommended maximum threshold for human administration. This study provides a comprehensive framework for the isolation, bioinformatic characterization, and safe production of phages to kill Achromobacter spp. in order to potentially manage Cystic Fibrosis (CF) pulmonary infections.

Biochar-assisted degradation of oxytetracycline by Achromobacter denitrificans and underlying mechanisms.

Contamination of the environment with large amounts of residual oxytetracycline (OTC) and the corresponding resistance genes poses a potential threat to natural ecosystems and human health. In this study, an effective OTC-degrading strain, identified as Achromobacter denitrificans OTC-F, was isolated from activated sludge. In the degradation experiment, the degradation rates of OTC in the degradation systems with and without biochar addition were 95.01-100% and 73.72-99.66%, respectively. Biochar promotes the biodegradation of OTC, particularly under extreme environmental conditions. Toxicity evaluation experiments showed that biochar reduced biotoxicity and increased the proportion of living cells by 17.36%. Additionally, biochar increased the activity of antioxidant enzymes by 34.1-91.0%. Metabolomic analysis revealed that biochar promoted the secretion of antioxidant substances such as glutathione and tetrahydrofolate, which effectively reduced oxidative stress induced by OTC. This study revealed the mechanism at the molecular level and provided new strategies for the bioremediation of OTC in the environment.

Exoproducts of the Most Common Achromobacter Species in Cystic Fibrosis Evoke Similar Inflammatory Responses In Vitro.

Achromobacter is a genus of Gram-negative rods, which can cause persistent airway infections in people with cystic fibrosis (CF). The knowledge about virulence and clinical implications of Achromobacter is still limited, and it is not fully established whether Achromobacter infections contribute to disease progression or if it is a marker of poor lung function. The most commonly reported Achromobacter species in CF is A. xylosoxidans. While other Achromobacter spp. are also identified in CF airways, the currently used Matrix-Assisted Laser Desorption/Ionization Time Of Flight Mass Spectrometry (MALDI-TOF MS) method in routine diagnostics cannot distinguish between species. Differences in virulence between Achromobacter species have consequently not been well studied. In this study, we compare phenotypes and proinflammatory properties of A. xylosoxidans, A. dolens, A. insuavis, and A. ruhlandii using in vitro models. Bacterial supernatants were used to stimulate CF bronchial epithelial cells and whole blood from healthy individuals. Supernatants from the well-characterized CF-pathogen Pseudomonas aeruginosa were included for comparison. Inflammatory mediators were analyzed with ELISA and leukocyte activation was assessed using flow cytometry. The four Achromobacter species differed in morphology seen in scanning electron microscopy (SEM), but there were no observed differences in swimming motility or biofilm formation. Exoproducts from all Achromobacter species except A. insuavis caused significant IL-6 and IL-8 secretion from CF lung epithelium. The cytokine release was equivalent or stronger than the response induced by P. aeruginosa. All Achromobacter species activated neutrophils and monocytes ex vivo in a lipopolysaccharide (LPS)-independent manner. Our results indicate that exoproducts of the four included Achromobacter species do not differ consistently in causing inflammatory responses, but they are equally or even more capable of inducing inflammation compared with the classical CF pathogen P. aeruginosa. IMPORTANCE Achromobacter xylosoxidans is an emerging pathogen among people with cystic fibrosis (CF). Current routine diagnostic methods are often unable to distinguish A. xylosoxidans from other Achromobacter species, and the clinical relevance of different species is still unknown. In this work, we show that four different Achromobacter species relevant to CF evoke similar inflammatory responses from airway epithelium and leukocytes in vitro, but they are all equally or even more proinflammatory compared to the classic CF-pathogen Pseudomonas aeruginosa. The results suggest that Achromobacter species are important airway pathogens in CF, and that all Achromobacter species are relevant to treat.

Identification of Virulence Factors Involved in a Murine Model of Severe Achromobacter xylosoxidans Infection.

Achromobacter xylosoxidans (Ax) is an opportunistic pathogen and causative agent of numerous infections particularly in immunocompromised individuals with increasing prevalence in cystic fibrosis (CF). To date, investigations have focused on the clinical epidemiology and genomic comparisons of Ax isolates, yet little is known about disease pathology or the role that specific virulence factors play in tissue invasion or damage. Here, we model an acute Ax lung infection in immunocompetent C57BL/6 mice and immunocompromised CF mice, revealing a link between in vitro cytotoxicity and disease in an intact host. Mice were intratracheally challenged with sublethal doses of a cytotoxic (GN050) or invasive (GN008) strain of Ax. Bacterial burden, immune cell populations, and inflammatory markers in bronchoalveolar lavage fluid and lung homogenates were measured at different time points to assess disease severity. CF mice had a similar but delayed immune response toward both Ax strains compared to C57BL/6J mice. GN050 caused more severe disease and higher mortality which correlated with greater bacterial burden and increased proinflammatory responses in both mouse models. In agreement with the cytotoxicity of GN050 toward macrophages in vitro, mice challenged with GN050 had fewer macrophages. Mutants with transposon insertions in predicted virulence factors of GN050 showed that disease severity depended on the type III secretion system, Vi capsule, antisigma-E factor, and partially on the ArtA adhesin. The development of an acute infection model provides an essential tool to better understand the infectivity of diverse Ax isolates and enable improved identification of virulence factors important to bacterial persistence and disease.