Clinical and laboratory characteristics of Achromobacter xylosoxidans infection

Identification and classification of the genomes of novel microviruses in poultry slaughterhouse

Microviridae is a family of phages with circular ssDNA genomes and they are widely found in various environments and organisms. In this study, virome techniques were employed to explore potential members of Microviridae in a poultry slaughterhouse, leading to the identification of 98 novel and complete microvirus genomes. Using a similarity clustering network classification approach, these viruses were found to belong to at least 6 new subfamilies within Microviridae and 3 higher-level taxonomic units. Genome size, GC content and genome structure of these new taxa showed evident regularities, validating the rationality of our classification method. Our method can divide microviruses into about 45 additional detailed clusters, which may serve as a new standard for classifying Microviridae members. Furthermore, by addressing the scarcity of host information for microviruses, the current study significantly broadened their host range and discovered over 20 possible new hosts, including important pathogenic bacteria such as Helicobacter pylori and Vibrio cholerae, as well as different taxa demonstrated different host specificities. The findings of this study effectively expand the diversity of the Microviridae family, providing new insights for their classification and identification. Additionally, it offers a novel perspective for monitoring and controlling pathogenic microorganisms in poultry slaughterhouse environments.

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.

One year experience of Achromobacter bacteremia at a tertiary care hospital in Northern India

Introduction

Achromobacter is a Gram-negative, motile, obligate aerobic and non-fermentative bacterium. It is an emerging pathogen in the hospital environment as it is frequently found in various solutions.

Hypothesis/Gap Statement

Information about the incidence and risk factors of Achromobacter bacteremia from India is limited.

Aim

We conducted this study to identify the risk factors and underlying conditions predisposing to bacteremia by Achromobacter spp. and analyse the antibiotic resistance pattern of the isolates.

Methodology

We performed a retrospective observational study where automated blood cultures positive for Achromobacter spp. were assessed for clinical characteristics and antibiotic susceptibility patterns from January 2022 to December 2022 in the microbiology laboratory of a tertiary care centre in Northern India.

Results

A total of 14 cases (14/2435, 0.57 %) of Achromobacter spp. were identified from bloodstream infections in one year. The mean age of the patients was 37.59±23.17 years with a male predominance (8/14, 57.1 %). All patients were managed on intravenous antibiotics and intravenous access as peripheral line catheters and only 5(5/14, 35.7 %) patients were managed on central line catheters. The isolates were found highly susceptible to ticarcillin-clavulanic acid (14/14, 100.0 %) followed by fluoroquinolones (12/14, 85.72 %) and trimethoprim-sulphamethoxazole (12/14, 85.72 %). Only 57.14 % (8/14, 57.14 %) of the patients were susceptible to piperacillin-tazobactam. The all-cause 40 day mortality was observed in 35.7 % (5/14, 35.7 %) with two deaths that were directly attributable to sepsis.

Conclusion

This study provides insight into the incidence of Achromobacter bacteremia at our centre and the necessary antibiotic therapy to combat it.

Pathogenesis of Achromobacter xylosoxidans respiratory infections: colonization and persistence of airway epithelia and differential gene expression 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 respiratory mucosal infections caused by a diverse array of opportunists, and these infections are a leading cause of morbidity and mortality for pwCF. In recent years, there has been increased appreciation for the range and diversity of microbes in CF-related respiratory infections. 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 that is widely distributed in the environment and has been increasingly observed in sputa and other samples from pwCF; typically Ax infections occur 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 involved in flagellar synthesis, antibiotic resistance, and toxin secretion systems. Ax isolates adhered to polarized CFBE14o- human immortalized CF bronchial epithelial cells and caused significant cytotoxicity and depolarization. Ax colonized and persisted in mouse lung for up to 72 hours post infection, with inflammatory consequences that include increased neutrophilia, lung damage, cytokine production, and mortality. Transcript profiling reveled differential expression of Ax genes during growth in SCFM2 synthetic CF sputum media. Based on these results, we conclude that Ax is an opportunistic pathogen of significance in CF.

Atypical microbial keratitis

Atypical microbial keratitis refers to corneal infections caused by micro-organisms not commonly encountered in clinical practice. Unlike infections caused by common bacteria, cases of atypical microbial keratitis are often associated with worse clinical outcomes and visual prognosis. This is due to the challenges in the identification of causative organisms with standard diagnostic techniques, resulting in delays in the initiation of appropriate therapies. Furthermore, due to the comparatively lower incidence of atypical microbial keratitis, there is limited literature on effective management strategies for some of these difficult to manage corneal infections. This review highlights the current management and available evidence of atypical microbial keratitis, focusing on atypical mycobacteria keratitis, nocardia keratitis, achromobacter keratitis, and pythium keratitis. It will also describe the management of two uncommonly encountered conditions, infectious crystalline keratopathy and post-refractive infectious keratitis. This review can be used as a guide for clinicians managing patients with such challenging corneal infections.

Polymyxin Resistance and Heteroresistance Are Common in Clinical Isolates of Achromobacter Species and Correlate with Modifications of the Lipid A Moiety of Lipopolysaccharide

The Achromobacter genus includes opportunistic pathogens that can cause chronic infections in immunocompromised patients, especially in people with cystic fibrosis (CF). Treatment of Achromobacter infections is complicated by antimicrobial resistance. In this study, a collection of Achromobacter clinical isolates, from CF and non-CF sources, was investigated for polymyxin B (PmB) resistance. Additionally, the effect of PmB challenge in a subset of isolates was examined and the presence of PmB-resistant subpopulations within the isolates was described. Further, chemical and mass spectrometry analyses of the lipid A of Achromobacter clinical isolates enabled the determination of the most common structures and showed that PmB challenge was associated with lipid A modifications that included the addition of glucosamine and palmitoylation and the concomitant loss of the free phosphate at the C-1 position. This study demonstrates that lipid A modifications associated with PmB resistance are prevalent in Achromobacter and that subresistant populations displaying the addition of positively charged residues and additional acyl chains to lipid A can be selected for and isolated from PmB-sensitive Achromobacter clinical isolates. IMPORTANCE Achromobacter species can cause chronic and potentially severe infections in immunocompromised patients, especially in those with cystic fibrosis. Bacteria cannot be eradicated due to Achromobacter's intrinsic multidrug resistance. We report that intrinsic resistance to polymyxin B (PmB), a last-resort antimicrobial peptide used to treat infections by multiresistant bacteria, is prevalent in Achromobacter clinical isolates; many isolates also display increased resistance upon PmB challenge. Analysis of the lipopolysaccharide lipid A moiety of several Achromobacter species reveals a penta-acylated lipid A, which in the PmB-resistant isolates was modified by the incorporation of glucosamine residues, an additional acyl chain, loss of phosphates, and hydroxylation of acyl chains, all of which can enhance PmB resistance in other bacteria. We conclude that PmB resistance, particularly in Achromobacter isolates from chronic respiratory infections, is a common phenomenon, and that Achromobacter lipid A displays modifications that may confer increased resistance to polymyxins and potentially other antimicrobial peptides.

Case Report: Septic Pericarditis With Achromobacter xyloxidans in an Immunosuppressed Dog

A 5-year-old female spayed French Bulldog presented for anorexia and increased respiratory rate. On presentation, she was dyspneic with stridor and increased bronchovesicular sounds. Point-of-care ultrasound identified pericardial effusion. Thoracic radiographs identified pleural effusion, a wide cranial mediastinum, and multifocal unstructured interstitial pulmonary opacities. Bloodwork revealed a moderate leukocytosis characterized by a mature neutrophilia with a left shift, hypoalbuminemia, mildly increased alkaline phosphatase activity, and moderate hypokalemia. Thoracic CT findings revealed moderate pericardial and bilateral pleural effusion, mediastinal effusion, and moderate cranial mediastinal lymphadenopathy. Diagnostic thoracocentesis and pericardiocentesis revealed septic exudates with bacilli. Two days later, a median sternotomy and pericardiectomy were performed. Aerobic cultures of the effusions grew Achromobacter xylosoxidans ss deitrificans. The patient was treated with Amoxicillin-clavulanate and enrofloxacin for 12 weeks and clinically fully recovered. Achromobacter xylosoxidans has not been reported as a cause of purulent pericarditis and pyothorax in a dog. Uniquely, this patient is suspected of developing this infection secondary to immunosuppression.

Case of recurrent Achromobacter xylosoxidans bacteraemia and PICC (peripherally-inserted central catheter) line infection in an immunocompromised patient

Background

Presentation of Case

Discussion

Conclusion

Chronic osteomyelitis caused by Achromobacter xylosoxidans following orthopaedic trauma: A case report and review of the literature

Background

Achromobacter xylosoxidans is an opportunistic environmental aerobe. In cases where A. xylosoxidans infects humans, it most commonly manifests as bacteraemia in the immunosuppressed. A. xylosoxidans causing chronic osteomyelitis is rare, particularly in the immunocompetent and young.

Case

We present the case of a 23-year-old man with chronic osteomyelitis of the right femur caused by co-infection of A. xylosoxidans and Staphylococcus aureus. Five years earlier, he had sustained a right femur fracture and was treated with intramedullary fixation at a peripheral hospital in a developing nation. Past medical history was otherwise unremarkable. Management comprised of surgical debridement and culture-directed antibiotic therapy, resulting in clinical cure.

Conclusion

In the context of local trauma and previous surgery, osteomyelitis caused by atypical pathogens must be considered. A multidisciplinary approach commensurate with duration and severity of infection and tailored to the causative organism is paramount.

Pulmonary biofilm-based chronic infections and inhaled treatment strategies

Certain pulmonary diseases, such as cystic fibrosis (CF), non-CF bronchiectasis, chronic obstructive pulmonary disease, and ventilator-associated pneumonia, are usually accompanied by respiratory tract infections due to the physiological alteration of the lung immunological defenses. Recurrent infections may lead to chronic infection through the formation of biofilms. Chronic biofilm-based infections are challenging to treat using antimicrobial agents. Therefore, effective ways to eradicate biofilms and thus relieve respiratory tract infection require the development of efficacious agents for biofilm destruction, the design of delivery carriers with biofilm-targeting and/or penetrating abilities for these agents, and the direct delivery of them into the lung. This review provides an in-depth description of biofilm-based infections caused by pulmonary diseases and focuses on current existing agents that are administered by inhalation into the lung to treat biofilm, which include i) inhalable antimicrobial agents and their combinations, ii) non-antimicrobial adjuvants such as matrix-targeting enzymes, mannitol, glutathione, cyclosporin A, and iii) liposomal formulations of anti-biofilm agents. Finally, novel agents that have shown promise against pulmonary biofilms as well as traditional and new devices for pulmonary delivery of anti-biofilm agents into the lung are also discussed.

A Rare Case of Non-Prosthetic Aortic Valve Infectious Endocarditis Caused by Achromobacter xylosoxidans

Patient: Male, 19-year-old

Final Diagnosis: Endocarditis

Symptoms: Fever • weigh loss

Medication: —

Clinical Procedure: —

Specialty: Cardiology

Analysis of bacterial community using pyrosequencing in semen from patients with chronic pelvic pain syndrome: a pilot study

Background

Although empirical antibacterial treatments are currently recommended for inflammatory chronic prostatitis/chronic pelvic pain syndrome (CP/CPPS), physicians cannot verify infections in most cases. Therefore, in this study, the microbiota of semen was investigated via pyrosequencing to obtain evidence underlying infectious disease.

Methods

Patients diagnosed with CP/CPPS (n=17) and healthy volunteers (n=4) participated in the study. Whole DNA was purified from the participants' semen. The DNA was amplified by polymerase chain reaction (PCR) using universal bacterial primers. All semen samples were also cultured using conventional methods. Pyrosequencing analysis of the PCR-amplified DNA was performed.

Results

None of the semen samples showed colony formation in conventional bacterial cultures. However, pyrosequencing revealed multiple bacterial genera in all samples, including an abundance of fastidious bacteria. Corynebacterium, Pseudomonas, Sphingomonas, Staphylococcus, and Streptococcus were frequently detected nonspecifically in both the patient and control groups. However, Achromobacter, Stenotrophomonas, and Brevibacillus were more frequently found in the CP/CPPS patients.

Conclusions

The identification of various dominant species in the CP/CPPS group other than those reported in previous studies might be helpful for future etiological analysis of CP/CPPS.

Azithromycin Exerts Bactericidal Activity and Enhances Innate Immune Mediated Killing of MDR Achromobacter xylosoxidans

Azithromycin (AZM), the most commonly prescribed antibiotic in the United States, is thought to have no activity against multidrug-resistant Gram-negative pathogens such as Achromobacter xylosoxidans (AX) per standard minimum inhibitory concentration testing in cation-adjusted Mueller Hinton Broth. Here we provide the first report of AZM bactericidal activity against carbapenem-resistant isolates of AX, with a multifold decrease in minimum inhibitory concentration across 12 clinical isolates when examined under physiologic testing conditions that better recapitulate the in vivo human environment. This pharmaceutical activity, evident in eukaryotic tissue culture media, is associated with enhanced AZM intracellular penetration and synergistic killing with human whole blood, serum, and neutrophils. Additionally, AZM monotherapy inhibited preformed AX biofilm growth in a dose-dependent manner together with a reduction in viable bacteria. In an illustrative case, AZM in combination with piperacillin-tazobactam exerted clear therapeutic effects in a patient with carbapenem-resistant AX mediastinitis, sternal osteomyelitis, and aortic graft infection. Our study reinforces how current antimicrobial testing practices fail to recapitulate the host environment or host-pathogen interactions and may misleadingly declare complete resistance to useful agents, adversely affecting patient outcomes. We conclude that AZM merits further exploration in the treatment of drug-resistant AX infections. Novel approaches to antimicrobial susceptibility testing that better recapitulate the host environment should be considered, especially as infections caused by multidrug-resistant Gram-negative bacterial pathogens are expanding globally with high morbidity and mortality.

Achromobacter veterisilvae sp. nov., from a mixed hydrogen-oxidizing bacteria enrichment reactor for microbial protein production

Strain LMG 30378^T was isolated from a hydrogen-oxidizing bacteria enrichment reactor inoculated with forest soil. Phylogenetic analysis based on the 16S rRNA gene sequence indicated that this strain belonged to the genus Achromobacter. Multilocus sequence analysis combined with sequence analysis of a 765 bp nrd A gene fragment both showed Achromobacter agilis LMG 3411^T and Achromobacter denitrificans LMG 1231^T to be the closest-related neighbours to strain LMG 30378^T. Genome sequence analysis revealed a draft genome of 6.81 Mb with a G+C content of 67.2 mol%. In silico DNA-DNA hybridization with A. denitrificans LMG 1231^T and A. agilis LMG 3411^T showed 42.7 and 42.5% similarity, respectively, confirming that strain LMG 30378^T represented a novel Achromobacter species. Phenotypic and metabolic characterization revealed acid phosphatase activity and the absence of phosphoamidase activity as distinctive features. The draft genome composes all necessary metabolic components to fix carbon dioxide and to oxidize molecular hydrogen, suggesting that strain LMG 30378^T is a key organism in the enrichment reactor. Together, these data demonstrate that strain LMG 30378^T represents a novel species of the genus Achromobacter, for which the name Achromobacter veterisilvae sp. nov. is proposed. The type strain is LMG 30378^T (=CCUG 71558^T).

First Documented Case of Percutaneous Endoscopic Gastrostomy (PEG) Tube-Associated Bacterial Peritonitis due to Achromobacter Species with Literature Review

Introduction. Achromobacter species (spp.) peritonitis has seldom been identified in medical literature. Scarce cases of Achromobacter peritonitis described previously have been correlated with peritoneal dialysis and more sparingly with spontaneous bacterial peritonitis. Achromobacter exhibits intrinsic and acquired resistance, especially in chronic infections, to most antibiotics. This article conducts a literature review of all previously reported Achromobacter spp. peritonitis and describes the first reported case of Achromobacter peritonitis as a complication of percutaneous endoscopic gastrostomy (PEG) tube placement. Discussion. Achromobacter peritonitis as a complication of PEG-tube placement has not been previously reported. In our patients' case, the recently placed PEG-tube with ascitic fluid leakage was identified as the most plausible infection source. Although a rare bacterial peritonitis pathogen, Achromobacter may be associated with wide antimicrobial resistance and unfavorable outcomes. Conclusion. No current guidelines provide significant guidance on treatment of PEG-tube peritonitis regardless of microbial etiology. Infectious Disease Society of America identifies various broad-spectrum antibiotics targeting nosocomial intra-abdominal coverage; some of these antimicrobial selections (such as cefepime and metronidazole combination) may yet be inadequate for widely resistant Achromobacter spp. Recognizably, the common antibiotics utilized for spontaneous bacterial peritonitis, i.e., third generation cephalosporins and fluoroquinolones, to which Achromobacter is resistant and variably susceptible, respectively, would be extensively insufficient. Piperacillin/tazobactam (P/T) and carbapenem were identified to provide the most reliable coverage in vitro; clinically, 5 out of the 8 patients who received either P/T or a carbapenem, or both, eventually experienced clinical improvement.

Adhesion of Pseudomonas aeruginosa, Achromobacter xylosoxidans, Delftia acidovorans, Stenotrophomonas maltophilia to contact lenses under the influence of an artificial tear solution

Corneal infection is a devastating sight-threatening complication that is associated with contact lens (CL) wear, commonly caused by Pseudomonas aeruginosa. Lately, Achromobacter xylosoxidans, Delftia acidovorans, and Stenotrophomonas maltophilia have been associated with corneal infection. This study investigated the adhesion of these emerging pathogens to CLs, under the influence of an artificial tear solution (ATS) containing a variety of components commonly found in human tears. Two different CL materials, etafilcon A and senofilcon A, either soaked in an ATS or phosphate buffered saline, were exposed to the bacteria. Bacterial adhesion was investigated using a radio-labeling technique (total counts) and plate count method (viable counts). The findings from this study revealed that in addition to P. aeruginosa, among the emerging pathogens evaluated, A. xylosoxidans showed an increased propensity for adherence to both CL materials and S. maltophilia showed lower viability. ATS influenced the viable counts more than the total counts on CLs.

Comparative genomics reveals a novel genetic organization of the sad cluster in the sulfonamide-degrader 'Candidatus Leucobacter sulfamidivorax' strain GP

Background

Microbial communities recurrently establish metabolic associations resulting in increased fitness and ability to perform complex tasks, such as xenobiotic degradation. In a previous study, we have described a sulfonamide-degrading consortium consisting of a novel low-abundant actinobacterium, named strain GP, and Achromobacter denitrificans PR1. However, we found that strain GP was unable to grow independently and could not be further purified.

Results

Previous studies suggested that strain GP might represent a new putative species within the Leucobacter genus (16S rRNA gene similarity < 97%). In this study, we found that average nucleotide identity (ANI) with other Leucobacter spp. ranged between 76.8 and 82.1%, further corroborating the affiliation of strain GP to a new provisional species. The average amino acid identity (AAI) and percentage of conserved genes (POCP) values were near the lower edge of the genus delimitation thresholds (65 and 55%, respectively). Phylogenetic analysis of core genes between strain GP and Leucobacter spp. corroborated these findings. Comparative genomic analysis indicates that strain GP may have lost genes related to tetrapyrrole biosynthesis and thiol transporters, both crucial for the correct assembly of cytochromes and aerobic growth. However, supplying exogenous heme and catalase was insufficient to abolish the dependent phenotype. The actinobacterium harbors at least two copies of a novel genetic element containing a sulfonamide monooxygenase (sadA) flanked by a single IS1380 family transposase. Additionally, two homologs of sadB (4-aminophenol monooxygenase) were identified in the metagenome-assembled draft genome of strain GP, but these were not located in the vicinity of sadA nor of mobile or integrative elements.

Conclusions

Comparative genomics of the genus Leucobacter suggested the absence of some genes encoding for important metabolic traits in strain GP. Nevertheless, although media and culture conditions were tailored to supply its potential metabolic needs, these conditions were insufficient to isolate the PR1-dependent actinobacterium further. This study gives important insights regarding strain GP metabolism; however, gene expression and functional studies are necessary to characterize and further isolate strain GP. Based on our data, we propose to classify strain GP in a provisional new species within the genus Leucobacter, ‘Candidatus Leucobacter sulfamidivorax‘.

Keratitis Due to Achromobacter xylosoxidans in a Contact Lens User

OBJECTIVES

Ocular infections due to Achromobacter xylosoxidans are extremely uncommon; their diagnosis is a challenge and the optimal treatment remains controversial. We present a case of A. xylosoxidans in a contact lens user and a review of the literature to facilitate diagnostic suspicion and empirical therapeutic management.

METHODS

Review of the literature in PubMed and MEDLINE. We also document a case diagnosed in our department in January 2016.

SETTING

Hospital Clínico Universitario Lozano Blesa, Zaragoza, Spain.

RESULTS

According to the literature, clinical manifestations and antibiotic sensitivity of A. xylosoxidans varied greatly. Our patient with no history of keratopathy presented three risk factors that made the diagnosis suspicious. The infection was resolved with topical moxifloxacin and fluorometholone.

CONCLUSIONS

A. xylosoxidans is an uncommon cause of infection, but must be suspected in atypical keratitis, reported contact with warm or still waters, use of contact lenses, or previous corneal damage. In these cases, microbiological studies and antibiotic sensitivity testing are particularly important.

Severe Achromobacter xylosoxidans keratitis with deep corneal involvement

Purpose

To describe a case of Achromobacter xylosoxidans keratitis with deep involvement of the corneal stroma and discuss its management.

Observations

A 73 year-old monocular male with infectious keratitis of the right eye was referred to the Wilmer Eye Institute after a month of empiric treatment with besifloxacin. On presentation, slit lamp examination of the right eye demonstrated a diffusely edematous cornea with three areas of corneal infiltrates and an overlying epithelial defect and a 1.3 mm hypopyon in the anterior chamber. The corneal culture performed grew A. xylosoxidans. Empiric antibiotic regimen was adjusted once corneal culture susceptibility results were available. Seven days later, slit lamp examination demonstrated a resolving epithelial defect, stable infiltrates, and resolution of the hypopyon. After approximately two months of follow up with his primary ophthalmologist, he was noted to have recurrent hypopyon and infiltrates and was referred back to Wilmer. Slit lamp examination again demonstrated an epithelial defect, diffuse corneal haze, deep stromal infiltrates, and a 1 mm hypopyon. Corneal infiltrates were too deep to culture. Ultimately, the patient underwent a therapeutic penetrating keratoplasty with anterior chamber washout resulting in improvement of vision.

Conclusions and importance

The indolent progression of A. xylosoxidans keratitis may predispose patients to delayed presentation and treatment. This can result in deep stromal infection that complicates management due to poor antibiotic penetration. Deep stromal infections in A. xylosoxidans keratitis warrant the consideration of intrastromal antibiotic injection or early therapeutic penetrating keratoplasty.

Treatment of Achromobacter Ventilator-Associated Pneumonia in Critically Ill Trauma Patients

BACKGROUND

Achromobacter sp are nonfermenting Gram-negative bacilli (NFGNB) that rarely cause severe infections, including ventilator-associated pneumonia (VAP). Data on the treatment of Achromobacter pneumonia are very limited, and the organism has been associated with a high mortality rate. Thus, more data are needed on treating this organism.

OBJECTIVE

To evaluate the treatment of Achromobacter VAP in critically ill trauma patients.

METHODS

This retrospective, observational study evaluated critically ill trauma patients who developed Achromobacter VAP. A previously published pathway for the diagnosis and management of VAP was used according to routine patient care. This included the use of quantitative bronchoscopic bronchoalveolar lavage cultures to definitively diagnose VAP.

RESULTS

A total of 37 episodes of Achromobacter VAP occurred in 34 trauma intensive care unit patients over a 15-year period. The most commonly used definitive antibiotics were imipenem/cilastatin, cefepime, or trimethoprim/sulfamethoxazole. The primary outcome of clinical success was achieved in 32 of 37 episodes (87%). This is similar to previous studies of other NFGNB VAP (eg, Pseudomonas, Acinetobacter) from the study center. Microbiological success was seen in 21 of 28 episodes (75%), and VAP-related mortality was 9% (3 of 34 patients).

CONCLUSIONS

Achromobacter is a rare but potentially serious cause of VAP in critically ill patients. In this study, there was an acceptable success rate compared with other causes of NFGNB VAP in this patient population.

Prevalence and Outcomes of Achromobacter Species Infections in Adults with Cystic Fibrosis: a North American Cohort Study

Achromobacter species are increasingly being detected in cystic fibrosis (CF) patients, with an unclear epidemiology and impact. We studied a cohort of patients attending a Canadian adult CF clinic who had positive sputum cultures for Achromobacter species in the period from 1984 to 2013. Infection was categorized as transient or persistent (≥50% positive cultures for 1 year). Those with persistent infection were matched 2:1 with age-, sex-, and time-matched controls without a history of Achromobacter infection, and mixed-effects models were used to assess pulmonary exacerbation (PEx) frequency and lung function decline. Isolates from a biobank were retrospectively assessed, identified to the species level by nrdA sequencing, and genotyped using pulsed-field gel electrophoresis (PFGE). Thirty-four patients (11% of those in our clinic), with a median age of 24 years (interquartile range [IQR], 20.3 to 29.8 years), developed Achromobacter infection. Ten patients (29%) developed persistent infection. Persistence did not denote permanence, as most patients ultimately cleared infection, often after years. Patients were more likely to experience PEx at incident isolation than at prior or subsequent visits (odds ratio [OR], 2.7 [95% confidence interval {CI}, 1.2 to 6.7]; P = 0.03). Following persistent infection, there was no difference in annual lung function decline (-1.08% [95% CI, -2.73 to 0.57%] versus -2.74% [95% CI, -4.02 to 1.46%]; P = 0.12) or the odds of PEx (OR, 1.21 [95% CI, 0.45 to 3.28]; P = 0.70). Differential virulence among Achromobacter species was not observed, and no cases of transmission occurred. We demonstrated that incident Achromobacter infection was associated with a greater risk of PEx; however, neither transient nor chronic infection was associated with a worsened long-term prognosis. Large, multicenter studies are needed to clarify the clinical impact, natural history, and transmissibility of Achromobacter.

Case report: The first case of Achromobacter xylosoxidans-related tunnel infection in a patient receiving peritoneal dialysis

RATIONALE

Achromobacter xylosoxidans infection is mostly reported in immunocompromised patients. Until now, it is still rarely reported in patients undergoing peritoneal dialysis.

PATIENT CONCERNS

This is the 1st case of A xylosoxidans infection due to tunnel infection of a Tenckhoff catheter.

DIAGNOSIS

The diagnosis was confirmed by the report of culture.

INTERVENTIONS

Risk factors for this infection in peritoneal dialysis include uremia with an immunocompromised state, contamination due to inexperienced skills, and aqueous environment of the dialysate.

OUTCOME

We believe that finding the source of A xylosoxidans contamination is the most important aspect of the overall treatment of the infection.

LESSONS

Environmental investigation of suspected source contamination is warranted in those with A xylosoxidans infection. Once the diagnosis is made, removal of the Tenckhoff catheter should not be delayed.

Clinical Features, Antibiotic Susceptibility Profiles, and Outcomes of Infectious Keratitis Caused by Achromobacter xylosoxidans

PURPOSE

Reports on Achromobacter xylosoxidans ocular infections are increasing, drawing attention to its emerging role in infectious keratitis. The purpose of this study is to report the clinical features, antibiotic sensitivities, and visual outcomes of infectious keratitis secondary to Achromobacter xylosoxidans.

METHODS

A microbiology database and clinical chart review was performed in all patients diagnosed with A. xylosoxidans keratitis at the Bascom Palmer Eye Institute between the years 1987 and 2014. Initial presentation, antimicrobial susceptibilities, minimum inhibitory concentrations (MICs), treatment course, and outcomes were recorded.

RESULTS

Twenty-eight patients were identified. The main risk factors were corneal graft (n = 8, 28.6%) and contact lens wear (n = 8, 28.6%). On presentation, visual acuity was 20/100 or worse in 20 (71.2%) patients. Hypopyon was present in 7 (25.0%) patients. In most cases, topical fluoroquinolones or tobramycin were the initial treatment, often accompanied by vancomycin. High susceptibility rates were found for piperacillin [100%, minimum inhibitory concentration for 90% of isolates (MIC90) = 8] and ticarcillin (100%, MIC90 = 16). Low susceptibility rates were documented for ciprofloxacin (46.7%, MIC90 = 8), tobramycin (26.7%, MIC90 = 16), and gentamicin (20%, MIC90 = 16). One (3.6%) patient suffered endophthalmitis. Six (21.4%) patients underwent therapeutic penetrating keratoplasty, and 2 (7.1%) patients had conjunctival flap surgery. Visual acuity at final follow-up was 20/100 or worse in 16 (57.1%) patients.

CONCLUSIONS

Infectious keratitis caused by A. xylosoxidans is associated with poor visual outcomes. Fluoroquinolones and aminoglycosides are not appropriate treatments for these ocular infections. Further studies are needed to define the clinical application of compound piperacillin and ticarcillin eye drops.

Deep sequencing approach for investigating infectious agents causing fever

Acute undifferentiated fever (AUF) poses a diagnostic challenge due to the variety of possible aetiologies. While the majority of AUFs resolve spontaneously, some cases become prolonged and cause significant morbidity and mortality, necessitating improved diagnostic methods. This study evaluated the utility of deep sequencing in fever investigation. DNA and RNA were isolated from plasma/sera of AUF cases being investigated at Cairns Hospital in northern Australia, including eight control samples from patients with a confirmed diagnosis. Following isolation, DNA and RNA were bulk amplified and RNA was reverse transcribed to cDNA. The resulting DNA and cDNA amplicons were subjected to deep sequencing on an Illumina HiSeq 2000 platform. Bioinformatics analysis was performed using the program Kraken and the CLC assembly-alignment pipeline. The results were compared with the outcomes of clinical tests. We generated between 4 and 20 million reads per sample. The results of Kraken and CLC analyses concurred with diagnoses obtained by other means in 87.5 % (7/8) and 25 % (2/8) of control samples, respectively. Some plausible causes of fever were identified in ten patients who remained undiagnosed following routine hospital investigations, including Escherichia coli bacteraemia and scrub typhus that eluded conventional tests. Achromobacter xylosoxidans, Alteromonas macleodii and Enterobacteria phage were prevalent in all samples. A deep sequencing approach of patient plasma/serum samples led to the identification of aetiological agents putatively implicated in AUFs and enabled the study of microbial diversity in human blood. The application of this approach in hospital practice is currently limited by sequencing input requirements and complicated data analysis.

Endophthalmitis caused by Achromobacter xylosoxidans after cataract surgery

PURPOSE

To report Achromobacter xylosoxidans as a cause of both acute-onset and delayed-onset postoperative endophthalmitis after cataract surgery.

METHODS

A noncomparative consecutive case series of patients with culture-proven A. xylosoxidans endophthalmitis between 1970 and 2012. Cataract surgery and intraocular lens placement were performed in all patients before endophthalmitis. Positive cultures were obtained from the vitreous, capsular bag, and/or the removed intraocular lens.

RESULTS

The clinical diagnosis was confirmed in four patients with positive cultures. Two patients with endophthalmitis had a preliminary culture report of Pseudomonas species. In addition to receiving intravitreal antibiotics, all patients underwent capsulectomy and intraocular lens removal at the time of pars plana vitrectomy. Visual acuity at last follow-up was 20/40 or better in 2 (50%) of the 4 patients, but the remaining 2 patients were 20/200 or worse.

CONCLUSION

A. xylosoxidans may be a cause of acute, recurrent, and delayed-onset postoperative endophthalmitis after cataract surgery. Complete capsulectomy and intraocular lens removal can be considered in recurrent and recalcitrant patients.

L5-S1 Achromobacter xylosoxidans infection secondary to oxygen-ozone therapy for the treatment of lumbosacral disc herniation: a case report and review of the literature

STUDY DESIGN

Case report and literature review.

OBJECTIVE

To present a unique case of Achromobacter xylosoxidans infection secondary to oxygen-ozone therapy for the treatment of L5-S1 disc herniation.

SUMMARY OF BACKGROUND DATA

Oxygen-ozone therapy is a minimally invasive technique for the treatment of lumbar disc herniations, with unproven efficacy and few reported complications. Achromobacter xylosoxidans is an opportunistic pathogen that inhabits aquatic environments and is a rare cause of osteomyelitis. To the best of our knowledge, this is the first report of A. xylosoxidans spondylodiscitis in the lumbar spine and the third report of spinal infection after intradiscal oxygen-ozone chemonucleolysis in the English literature.

METHODS

The medical records, operative reports, and radiographical imaging studies of a single patient were retrospectively reviewed.

RESULTS

A 29-year-old female patient who previously underwent oxygen-ozone therapy for L5-S1 disc herniation presented to our institution with a 5-month history of intractable back and leg pain. The patient's laboratory studies were within normal limits and did not indicate signs of an active infection. Her physical examination revealed globally decreased muscle strength (4/5) and hyperesthesia in the lower extremities. Magnetic resonance imaging and computed tomography revealed severe disc degeneration and vertebral body endplate changes at L5-S1, in addition to paravertebral soft tissue swelling consistent with a previous infection. Given the severity of symptoms, the patient underwent anterior lumbar interbody fusion and posterior segmental instrumentation at L5-S1. Histopathological evaluation of the disc material confirmed the diagnosis of chronic osteomyelitis and septic discitis at L5-S1. Intraoperative cultures grew A. xylosoxidans and Propionibacterium acnes. The patient had prompt improvement in her level of pain and was discharged on a 6-week course of piperacillin-tazobactam without complication.

CONCLUSION

This first report of A. xylosoxidans vertebral infection secondary to oxygen-ozone therapy illustrates the wide variety of environmental pathogens that can complicate the percutaneous treatment of degenerative vertebral disease.

Skin and soft tissue infection caused by Achromobacter xylosoxidans: report of 14 cases

BACKGROUND

Skin and soft tissue infections (SSTIs) caused by Achromobacter xylosoxidans are very infrequent. The aim of the present study was to investigate the clinical and microbiological characteristics of this infection.

METHODS

We carried out a retrospective review of 14 cases of SSTI due to A. xylosoxidans that occurred at the University Hospital of Guadalajara (Spain) from January 2007 to December 2012.

RESULTS

The infection was secondary to vascular diseases, trauma, and recent surgery in 12 patients (85.7%). The most frequent clinical presentation was infection of a vascular ulcer (5 cases). The infection was monomicrobial in 7 patients (50%) and 9 cases were community-acquired (64.2%). The clinical outcome of the patients was uniformly good after antibiotic treatment, except in 4 patients who suffered recurrence of the infection.

CONCLUSION

A. xylosoxidans should be considered a potential pathogen in patients with SSTIs, especially in patients with vascular diseases or after surgery or trauma. A history of contact with water should be investigated in all cases. Treatment can be difficult due to the high level of antibiotic resistance. Trimethoprim-sulfamethoxazole may be useful for treatment in outpatients with community-acquired infections.

Antibody response to Achromobacter xylosoxidans during HIV infection is associated with lower CD4 levels and increased lymphocyte activation

Inflammation during HIV infection is associated with worse disease outcomes and progression. Many mechanisms have been indicted, including HIV itself, coinfections, and gut microbial translocation. Concerning microbial translocation, we hypothesized that adaptive immune responses to a specific bacterial species known to be present in gut-associated lymphoid tissue are higher among HIV-infected individuals than among HIV-uninfected controls and are associated with T cell activation and lower CD4 T cell counts. By characterizing the IgG response to Achromobacter xylosoxidans, we found that HIV-infected participants who were immunoresponsive (n = 48) had significantly lower CD4 percentages (P = 0.01), greater CD4 activation (percentages of RA(-) CD38(+)) (P = 0.03), and higher soluble CD14 (P = 0.01). HIV-positive individuals had higher anti-A. xylosoxidans IgG titers than HIV-uninfected individuals (P = 0.04). The results suggest an abnormal adaptive immune activation to gut microflora during HIV infection.

Calcaneal osteomyelitis due to Achromobacter xylosoxidans: a case report

Achromobacter xylosoxidans (A. xylosoxidans) has been described as an opportunistic pathogen causing infection. The case we describe is that of an elderly man who had osteomyelitis of calcaneal bone caused by A. xylosoxidans. As far as we are aware there are only 5 cases of osteomyelitis with A. xylosoxidans in the literature. Impaired defensive mechanism of the foot in direct contact with this waterborne bacterium can cause this disease. Because of the high level of antibiotic resistance of this bacterium, clinically more attention should be paid to patients who have impaired defensive mechanisms in their extremities, for example free flaps.

Complete genome sequence of the cystic fibrosis pathogen Achromobacter xylosoxidans NH44784-1996 complies with important pathogenic phenotypes

Achromobacter xylosoxidans is an environmental opportunistic pathogen, which infects an increasing number of immunocompromised patients. In this study we combined genomic analysis of a clinical isolated A. xylosoxidans strain with phenotypic investigations of its important pathogenic features. We present a complete assembly of the genome of A. xylosoxidans NH44784-1996, an isolate from a cystic fibrosis patient obtained in 1996. The genome of A. xylosoxidans NH44784-1996 contains approximately 7 million base pairs with 6390 potential protein-coding sequences. We identified several features that render it an opportunistic human pathogen, We found genes involved in anaerobic growth and the pgaABCD operon encoding the biofilm adhesin poly-β-1,6-N-acetyl-D-glucosamin. Furthermore, the genome contains a range of antibiotic resistance genes coding efflux pump systems and antibiotic modifying enzymes. In vitro studies of A. xylosoxidans NH44784-1996 confirmed the genomic evidence for its ability to form biofilms, anaerobic growth via denitrification, and resistance to a broad range of antibiotics. Our investigation enables further studies of the functionality of important identified genes contributing to the pathogenicity of A. xylosoxidans and thereby improves our understanding and ability to treat this emerging pathogen.

Bacteremia due to Achromobacter xylosoxidans in neonates: clinical features and outcome

Objective

We report an outbreak of Achromobacter xylosoxidans at a neonatal intensive care unit. We aimed to present clinical, laboratory and treatment data of the patients.

Materials and methods

All consecutive episodes of bacteremia due to A. xylosoxidans at our neonatal intensive care unit, beginning with the index case detected at November 2009 until cessation of the outbreak in April 2010, were evaluated retrospectively.

Results

Thirty-four episodes of bacteremia occurred in 22 neonates during a 6-month period. Among the affected, 90% were preterm newborns with gestational age of 32 weeks or less and 60% had birth weight of 1000 g or less. Endotracheal intubation, intravenous catheter use, total parenteral nutrition and prolonged antibiotic therapy were the predisposing conditions. Presenting features were abdominal distention, thrombocytopenia and neutropenia. The mortality rate was 13.6% and the majority of isolates were susceptible to piperacillin-tazobactam, carbapenems and trimethoprim-sulfametoxazole, and resistant to gentamycin. More than half were breakthrough infections. Despite intensive efforts to control the outbreak by standard methods of hand hygiene, patient screening and isolation, containment could be achieved only after the neonatal intensive care unit was relocated. The investigation was not able to single out the source of the outbreak.

Conclusion

A. xylosoxidans has the potential to cause serious infections in premature babies. More studies are needed to determine the importance of different sources of infection in hospital units.

Achromobacter species endocarditis: A case report and literature review

Endocarditis due to Achromobacter species is a rare, yet serious, endovascular infection. Achromobacter species infective endocarditis is associated with underlying immunodeficiencies or prosthetic heart valves and devices. A case of prosthetic pulmonary valve endocarditis secondary to Achromobacter xylosoxidans subspecies denitrificans is described in the present report. This life-threatening infection was successfully treated with combined valve replacement and prolonged antibiotic therapy. A Medline/PubMed literature review of Achromobacter endocarditis was also performed. Achromobacter species are an uncommon, yet important, cause of nosocomial endocarditis. Given the significant associated morbidity and mortality, along with a high degree of intrinsic antibiotic resistance, Achromobacter species infective endocarditis remains a clinical treatment challenge.

Genetic and symbiotic diversity of nitrogen-fixing bacteria isolated from agricultural soils in the western Amazon by using cowpea as the trap plant

Cowpea is a legume of great agronomic importance that establishes symbiotic relationships with nitrogen-fixing bacteria. However, little is known about the genetic and symbiotic diversity of these bacteria in distinct ecosystems. Our study evaluated the genetic diversity and symbiotic efficiencies of 119 bacterial strains isolated from agriculture soils in the western Amazon using cowpea as a trap plant. These strains were clustered into 11 cultural groups according to growth rate and pH. The 57 nonnodulating strains were predominantly fast growing and acidifying, indicating a high incidence of endophytic strains in the nodules. The other 62 strains, authenticated as nodulating bacteria, exhibited various symbiotic efficiencies, with 68% of strains promoting a significant increase in shoot dry matter of cowpea compared with the control with no inoculation and low levels of mineral nitrogen. Fifty genotypes with 70% similarity and 21 genotypes with 30% similarity were obtained through repetitive DNA sequence (BOX element)-based PCR (BOX-PCR) clustering. The 16S rRNA gene sequencing of strains representative of BOX-PCR clusters showed a predominance of bacteria from the genus Bradyrhizobium but with high species diversity. Rhizobium, Burkholderia, and Achromobacter species were also identified. These results support observations of cowpea promiscuity and demonstrate the high symbiotic and genetic diversity of rhizobia species in areas under cultivation in the western Amazon.

Heterotrophic nitrification by Achromobacter xylosoxidans S18 isolated from a small-scale slaughterhouse wastewater

Heterotrophic carbon utilizing microbes were acclimatized in the laboratory by inoculating sludge collected from the waste discharge pond of a small-scale rural abattoir in India in a nutrient solution intermittently fed with glucose and ammonium chloride. Cultures of 10 well-developed isolates were selected and grown in a basal medium containing glucose and ammonium chloride. Culture supernatants were periodically analyzed for ammonium nitrogen (NH(4)(+)-N) and chemical oxygen demand (COD). Polyphasic taxonomic study of the most active nitrifier (S18) was done. Half saturation concentration (K(s)), maximum rate of substrate utilization (k), yield coefficient (Y) and decay coefficient (K(d)) were determined from the Lineweaver-Burk plot using the modified Monod equation. S18 was able to remove 97 ± 2% of (NH(4)(+)-N) and 88 ± 3% of COD. Molecular phylogenetic study supported by physiological and biochemical characteristics assigned S18 as Achromobacter xylosoxidans. Nitrification activity of A. xylosoxidans was demonstrated for the first time, while interestingly, the distinctive anaerobic denitrification property was preserved in S18. K (s) values were determined as 232.13 ± 1.5 mg/l for COD reduction and 2.131 ± 1.9 mg/l for NH(4)(+)-N utilization. Yield coefficients obtained were 0.4423 ± 0.1134 mg of MLVSS/mg of COD and 0.2461 ± 0.0793 mg of MLVSS/mg of NH(4)(+)-N while the decay coefficients were 0.0627 ± 0.0013 per day and 0.0514 ± 0.0008 per day, respectively. After a contact period of 24 h, 650 ± 5 mg/l solids were produced when the initial concentration of COD and NH(4)(+)-N were 1820 ± 10 mg/l and 120 ± 5.5 mg/l, respectively. This is the first report on the kinetic coefficients for carbon oxidation and nitrification by a single bacterium isolated from slaughterhouse wastewater.

CAPD peritonitis caused by Alcaligenes xylosoxidans in a diabetic cirrhosis patient

Despite the advancement of disconnecting system, peritonitis remains one of the most common causes in patients treated with continuous ambulatory peritoneal dialysis (CAPD). We report a cirrhosis patient undergoing CAPD who suffered from an episode of peritonitis caused by a rare pathogen, Alcaligenes xylosoxidans (AX). This organism rarely induces CAPD peritonitis and only nine cases were reported in the literature. This is the first case of AX-related CAPD peritonitis in cirrhosis patient. Infection with AX is more common in immunocompromised patients and is associated with a high mortality rate. Appropriate antibiotics and early removal of CAPD catheter may be life-saving in such rare infection.

Clinical, microbiological profile and treatment outcome of ocular infections caused by Achromobacter xylosoxidans

PURPOSE

To study the microbiological profile and outcome of ocular infections caused by Achromobacter xylosoxidans.

METHODS

Medical and microbiology records of patients with A. xylosoxidans ocular infections managed between May 2007 and December 2007 were reviewed.

RESULTS

The authors identified 10 patients whose eyes were infected by A. xylosoxidans during the study period. Of 10 patients, 8 had microbial keratitis, of whom 6 developed an infection after penetrating keratoplasty. The remaining 2 patients had endophthalmitis. The Gram-stained smear did not reveal any organism in 6 of 10 cases. In the 4 remaining cases, Gram-negative bacilli were reported. Out of 10 isolates, 9 were sensitive to ceftazidime, 7 to amikacin, 5 to ciprofloxacin, and 3 to ofloxacin, gatifloxacin, and chloramphenicol. Only one isolate was sensitive to moxifloxacin. Of the 6 patients with graft infection, 2 patients were lost to follow-up, infection was resolved in 3 patients, and the infection remained active in 1 patient. The two patients with endophthalmitis responded to antibacterial therapy and showed improved visual acuity. Infection was resolved in 2 patients with keratitis.

CONCLUSION

Although A. xylosoxidans ocular infections are rare, one should retain a high index of clinical suspicion in patients who present with slowly progressive disease characterized by a localized infiltration and show Gram-negative bacilli on smear examination.

Urinary tract infection due toAchromobacter xylosoxidans: Report of 9 cases

Urinary tract infection (UTI) due to Achromobacter xylosoxidans is rare. The aims were to know the frequency and clinical characteristics of this infection in our area. We performed a retrospective analysis of 9 patients with UTI caused by this organism diagnosed over a period of 13 y. The mean age was 63.1 y. All patients had underlying diseases or urological abnormalities. The most frequent underlying diseases were solid or hematological malignancies (3 cases). Seven patients (77.7%) had urological abnormalities. Eight patients had symptoms of cystitis and 1 remained asymptomatic. Seven patients had community acquired UTIs. Clinical outcome was favourable in 5 patients after antibiotic treatment and recurrence occurred in 3 patients who had urological abnormalities. All isolates were susceptible to imipenem and piperacillin-tazobactam, 88.8% were susceptible to ceftazidime and 77.7% were susceptible to trimethoprim-sulfamethoxazole. High frequencies of resistance to ampicillin (100%), amoxicillin/clavulanic acid (78%), cefuroxime (100%), cefotaxime (67%), norfloxacin (89%), ciprofloxacin (78%), nitrofurantoin (89%) and gentamicin (67%) were observed. UTI due to A. xylosoxidans was predominantly observed in elderly patients with predisposing factors, especially urological abnormalities, malignancies and immunosuppression. Treatment can be difficult due to the high level of antibiotic resistance. Trimethoprim-sulfamethoxazole may be useful for treatment, particularly in outpatients with community acquired infections.