A novel bacterium Achromobacter xylosoxidans as a cause of liver abscess: three case reports

Opportunistic Pathogens in Cystic Fibrosis: Epidemiology and Pathogenesis of Lung Infection

Cystic fibrosis (CF) is one of the most common life-shortening genetic diseases in Caucasians. Due to abnormal accumulation of mucus, respiratory failure caused by chronic infections is the leading cause of mortality in this patient population. The microbiology of these respiratory infections includes a distinct set of opportunistic pathogens, including Pseudomonas aeruginosa, Burkholderia spp., Achromobacter spp., Stenotrophomonas maltophilia, anaerobes, nontuberculous mycobacteria, and fungi. In recent years, culture-independent methods have shown the polymicrobial nature of lung infections, and the dynamics of microbial communities. The unique environment of the CF airway predisposes to infections caused by opportunistic pathogens. In this review, we will highlight how the epidemiology and role in disease of these pathogens in CF differ from that in individuals with other medical conditions. Infectious diseases (ID) physicians should be aware of these differences and the specific characteristics of infections associated with CF.

Immunoinformatic Approach to Contrive a Next Generation Multi-Epitope Vaccine Against Achromobacter xylosoxidans Infections

Achromobacter xylosoxidans, previously identified as Alcaligenes xylosoxidans, is a rod-shaped, flagellated, non-fermenting Gram-negative bacterium that has the ability to cause diverse infections in humans. As a part of its intrinsic resistance to different antibiotics, Achromobacter spp. is also increasingly becoming resistant to Carbapenems. Lack of knowledge regarding the pathogen’s clinical features has led to limited efforts to develop countermeasures against infection. The current study utilized an immunoinformatic method to map antigenic epitopes (Helper T cells, B-cell and Cytotoxic-T cells) to design a vaccine construct. We found that 20 different epitopes contribute significantly to immune response instigation that was further supported by physicochemical analysis and experimental viability. The safety profile of our vaccine was tested for antigenicity, allergenicity, and toxicity against all the identified epitopes before they were used as vaccine candidates. The disulfide engineering was carried out in an area of high mobility to increase the stability of vaccine proteins. In order to determine if the constructed vaccine is compatible with toll-like receptor, the binding affinity of vaccine was investigated via molecular docking approach. With the in silico expression in host cells and subsequent immune simulations, we were able to detect the induction of both arms of the immune response, i.e., humoral response and cytokine induced response. To demonstrate its safety and efficacy, further experimental research is necessary.

Achromobacter spp. Surgical Site Infections: A Systematic Review of Case Reports and Case Series

Achromobacter species are isolated from rare but severe healthcare-associated infections, including surgical site infections. They are considered to preferentially infect immunocompromised patients but so far with limited evidence. We conducted a systematic review on Achromobacter spp. surgical site infections (SSIs) to determine if such infections were indeed more commonly associated with immunocompromised patients. The secondary objective was to describe the characteristics of infected patients. Eligible articles had to be published before 30 September 2020 and to report Achromobacter spp. SSIs across all surgical specialties excluding ophthalmology. Analyses were performed on individual data without meta-analysis. Cases were divided into 2 subgroups: one group which had either prosthesis or implant and the other group which did not. A first selection led to a review of 94 articles, of which 37 were analyzed. All were case reports or case series and corresponded to 49 infected patients. Most of the patients were under 65 years of age and had undergone a heart or digestive surgery followed by deep infection with no co-infecting pathogens. Nine out of the 49 cases were immunocompromised, with similar distribution between the two subgroups (16.6% and 20%, respectively). This review suggests that Achromobacter spp. SSIs do not preferentially target immunocompromised patients.

Achromobacter Infections and Treatment Options

Achromobacter is a genus of nonfermenting Gram-negative bacteria under order Burkholderiales Although primarily isolated from respiratory tract of people with cystic fibrosis, Achromobacter spp. can cause a broad range of infections in hosts with other underlying conditions. Their rare occurrence and ever-changing taxonomy hinder defining their clinical features, risk factors for acquisition and adverse outcomes, and optimal treatment. Achromobacter spp. are intrinsically resistant to several antibiotics (e.g., most cephalosporins, aztreonam, and aminoglycosides), and are increasingly acquiring resistance to carbapenems. Carbapenem resistance is mainly caused by multidrug efflux pumps and metallo-β-lactamases, which are not expected to be overcome by new β-lactamase inhibitors. Among the other new antibiotics, cefiderocol, and eravacycline were used as salvage therapy for a limited number of patients with Achromobacter infections. In this article, we aim to give an overview of the antimicrobial resistance in Achromobacter species, highlighting the possible place of new antibiotics in their treatment.

Identification of Gram negative non-fermentative bacteria: How hard can it be?

INTRODUCTION

The prevalence of bacteremia caused by Gram negative non-fermentative (GNNF) bacteria has been increasing globally over the past decade. Many studies have investigated their epidemiology but focus on the common GNNF including Pseudomonas aeruginosa and Acinetobacter baumannii. Knowledge of the uncommon GNNF bacteremias is very limited. This study explores invasive bloodstream infection GNNF isolates that were initially unidentified after testing with standard microbiological techniques. All isolations were made during laboratory-based surveillance activities in two rural provinces of Thailand between 2006 and 2014.

METHODS

A subset of GNNF clinical isolates (204/947), not identified by standard manual biochemical methodologies were run on the BD Phoenix automated identification and susceptibility testing system. If an organism was not identified (12/204) DNA was extracted for whole genome sequencing (WGS) on a MiSeq platform and data analysis performed using 3 web-based platforms: Taxonomer, CGE KmerFinder and One Codex.

RESULTS

The BD Phoenix automated identification system recognized 92% (187/204) of the GNNF isolates, and because of their taxonomic complexity and high phenotypic similarity 37% (69/187) were only identified to the genus level. Five isolates grew too slowly for identification. Antimicrobial sensitivity (AST) data was not obtained for 93/187 (50%) identified isolates either because of their slow growth or their taxa were not in the AST database associated with the instrument. WGS identified the 12 remaining unknowns, four to genus level only.

CONCLUSION

The GNNF bacteria are of increasing concern in the clinical setting, and our inability to identify these organisms and determine their AST profiles will impede treatment. Databases for automated identification systems and sequencing annotation need to be improved so that opportunistic organisms are better covered.

Achromobacter respiratory infections

Achromobacteria are ubiquitous environmental organisms that may also become opportunistic pathogens in certain conditions, such as cystic fibrosis, hematologic and solid organ malignancies, renal failure, and certain immune deficiencies. Some members of this genus, such as xylosoxidans, cause primarily nosocomially acquired infections affecting multiple organ systems, including the respiratory tract, urinary tract, and, less commonly, the cardiovascular and central nervous systems. Despite an increasing number of published case reports and literature reviews suggesting a global increase in achromobacterial disease, most clinicians remain uncertain of the organism's significance when clinically isolated. Moreover, effective treatment can be challenging due to the organism's inherent and acquired multidrug resistance patterns. We reviewed all published cases to date of non-cystic fibrosis achromobacterial lung infections to better understand the organism's pathogenic potential and drug susceptibilities. We found that the majority of these cases were community acquired, typically presenting as pneumonias (88%), and were most frequent in individuals with hematologic and solid organ malignancies. Our findings also suggest that achromobacterial lung infections are difficult to treat, but respond well to extended-spectrum penicillins and cephalosporins, such as ticarcillin, piperacillin, and cefoperazone.

Achromobacter xylosoxidans mesh related infection: a case of delayed diagnosis and management

We present the first case of mesh related infection caused by Achromobacter xylosoxidans after ventral hernia repair. After repair of a small paraumbilical hernia, the postoperative course was complicated by persistent discharging sinuses despite the removal of underlying polypropylene mesh. Removal of an intrabdominal omental inflammatory mass containing pus that showed growth of A. xylosoxidans led to the resolution of all the symptoms.

Achromobacter xylosoxidans infection presenting as a pulmonary nodule mimicking cancer

Achromobacter xylosoxidans is typically isolated from pulmonary sources, presenting as pneumonia in immunosuppressed individuals. We describe a novel clinical presentation of A. xylosoxidans infection presenting as multiple spiculated, pulmonary nodules mimicking cancer for which the patient underwent a wedge resection of the lung for diagnosis and staging of presumptive cancer.

Got black swimming dots in your cell culture? Identification of Achromobacter as a novel cell culture contaminant

Cell culture model systems are utilized for their ease of use, relative inexpensiveness, and potentially limitless sample size. Reliable results cannot be obtained, however, when cultures contain contamination. This report discusses the observation and identification of mobile black specks observed in multiple cell lines. Cultures of the contamination were grown, and DNA was purified from isolated colonies. The 16S rDNA gene was PCR amplified using primers that will amplify the gene from many genera, and then sequenced. Sequencing results matched the members of the genus Achromobacter, bacteria common in the environment. Achromobacter species have been shown to be resistant to multiple antibiotics. Attempts to decontaminate the eukaryotic cell culture used multiple antibiotics at different concentrations. The contaminating Achromobacter was eventually eliminated, without permanently harming the eukaryotic cells, using a combination of the antibiotics ciprofloxacin and piperacillin.

Hepatobiliary pathology

PURPOSE OF REVIEW

Publications concerning liver histopathology in fatty liver disease and chronic hepatitis C, iron and copper overload, and liver transplantation from the past year have been surveyed to highlight useful concepts and diagnostic information.

RECENT FINDINGS

Two microscopic forms of pediatric nonalcoholic steatohepatitis have been described: type 1 in which hepatocyte ballooning and/or pericellular fibrosis accompany the steatosis; and type 2 which has portal tract inflammation and/or fibrosis as the salient accompanying feature. In chronic hepatitis C, the ductular reaction appears to be a major factor associated with fibrosis. In patients transplanted for hepatitis C virus-related cirrhosis, immunostaining of post-transplant liver biopsies for alpha-smooth muscle actin (i.e. in activated hepatic stellate cells) may identify those individuals at risk for severe recurrence. Clinicopathological papers on several forms of non-HFE hemochromatosis were published and Wilson's disease was described in individuals of 60 years or more in age. Cholestasis in childhood was expertly reviewed and histopathologic precursor lesions of hepatocellular carcinoma were also examined in a comprehensive article.

SUMMARY

Recent publications with impact on liver biopsy interpretation include a morphologic classification of nonalcoholic steatohepatitis in childhood, the differential diagnosis of childhood cholestasis and pathogenetic factors involved in fibrogenesis in chronic hepatitis C.