Delftia acidovorans: An Unusual Pathogen from an Adenocarcinoma Lung Patient with Pleural Effusion

Delftia acidovorans (D. acidovorans) is an aerobic, nonfermentative Gram-negative bacillus infrequently isolated from clinical specimens. The pathogenicity and clinical significance of the organism has not been ascertained due to uncommon clinical isolation and suspected low virulence. The organism has been reported to be inherently resistant to aminoglycoside group of drugs which remain as a widely used first-line drug of choice for febrile neutropenic patients. Hereby, we report a case of D. acidovorans-associated pleural effusion in a patient of metastatic adenocarcinoma diagnosed and treated timely and successfully with appropriate antibiotics.

Drinking-water isolated Delftia acidovorans selectively coaggregates with partner bacteria and facilitates multispecies biofilm development

Coaggregation plays an important role in the development of multispecies biofilms in different environments, often serving as an active bridge between biofilm members and other organisms that, in their absence, would not integrate the sessile structure. The ability of bacteria to coaggregate has been reported for a limited number of species and strains. In this study, 38 bacterial strains isolated from drinking water (DW) were investigated for their ability to coaggregate, in a total of 115 pairs of combinations. Among these isolates, only Delftia acidovorans (strain 005P) showed coaggregating ability. Coaggregation inhibition studies have shown that the interactions mediating D. acidovorans 005P coaggregation were both polysaccharide-protein and protein-protein, depending on the interacting partner bacteria. Dual-species biofilms of D. acidovorans 005P and other DW bacteria were developed to understand the role of coaggregation on biofilm formation. Biofilm formation by Citrobacter freundii and Pseudomonas putida strains highly benefited from the presence of D. acidovorans 005P, apparently due to the production of extracellular molecules/public goods favouring microbial cooperation. This was the first time that the coaggregation capacity of D. acidovorans was demonstrated, highlighting its role in providing a metabolic opportunity for partner bacteria.

Endophthalmitis due to Delftia acidovorans: An unusual ocular pathogen

Endophthalmitis is a dreaded postoperative complication of cataract surgery. Delftia acidovorans is usually nonpathogenic and an unusual ocular pathogen. Isolated reports of delftia-associated sepsis, otitis media, endocarditis, keratitis, etc. exist in literature. We report a rare and unique case of delftia-related endophthalmitis in a 67-year-old male diagnosed 2 weeks after uneventful cataract surgery. He was treated successfully with core vitrectomy and intravitreal antibiotics. Microbiological evaluation of vitreous sample identified the causative organism as Delftia acidovorans. Post-vitrectomy fundus evaluation at 1 week revealed the presence of retinal vascular sheathing and sclerosis along with few retinal hemorrhages. Final visual recovery was poor due to the presence of macular edema, epiretinal membrane, and temporal disc pallor.

Delftia acidovorans pneumonia with lung cavities formation

Case Description

A 52-year-old female patient was admitted to our clinic with complaints of cough, sputum, fever and fatigue. The patient has been receiving immunosuppressive therapy for thrombocytopenic purpura for 5 years.

Clinical Finding

Inspiratory crackles were heard on both hemithorax. Oxygen saturation measured with the pulse oximeter was 97%. Chest X-ray showed diffuse reticular opacities that were more prominent in the upper zones of both lungs. WBC counts were 17,600 mm³ and Platelet counts were 29,000 mm³. Thorax CT showed that there were many thin-walled cavities and millimetric nodules accompanied by ground-glass infiltrates in the upper and middle lobes. Gram staining of bronchial fluid, taken by bronchoscopy, revealed Gram-negative bacilli and intense polymorphonuclear leukocytes. The bacteria were defined as Delftia acidovorans by BD Phoenix automated system.

Treatment and outcomes

The patient was hospitalized with suspicion of opportunistic pulmonary infections and cavitary lung disease. After the empirical treatment of intravenous piperacillin-tazobactam and oral clarithromycin, her clinical and radiological findings significantly regressed, and she was discharged with outpatient follow-up.

Clinical Relevance

This is the first example of cavitary pneumonia due to Delftia acidovorans in an immunocompromised patient. We would like to emphasize that Delftia pneumonia should be considered in the differential diagnosis of pulmonary cavitary involvement in such patients.

Proteomic Analyses of Chlorhexidine Tolerance Mechanisms in Delftia acidovorans Biofilms

Protein expression and fatty acid profiles of biofilm cells of chlorhexidine-tolerant Delftia acidovorans (MIC = 15 µg/ml) and its chlorhexidine-susceptible mutant (MIC = 1 µg/ml) were investigated. The chlorhexidine-susceptible mutant (MT51) was derived from the parental strain (WT15) using Tn5 transposon mutagenesis. The disrupted gene was identified as tolQ, a component of the tolQRAB gene cluster known to be involved in outer membrane stability. Proteomic responses of biofilm cells were compared by differential in-gel electrophoresis following exposure to chlorhexidine at sub-MIC (10 µg/ml) and above-MIC (30 µg/ml) concentrations. Numerous changes in protein abundance were observed in biofilm cells following chlorhexidine exposure, suggesting that molecular changes occurred during adaptation to chlorhexidine. Forty proteins showing significant differences (≥1.5-fold; P < 0.05) were identified by mass spectrometry and were associated with various functions, including amino acid and lipid biosynthesis, protein translation, energy metabolism, and stress-related functions (e.g., GroEL, aspartyl/glutamyl-tRNA amidotransferase, elongation factor Tu, Clp protease, and hydroxymyristoyl-ACP dehydratase). Several proteins involved in fatty acid synthesis were affected by chlorhexidine, in agreement with fatty acid analysis, wherein chlorhexidine-induced shifts in the fatty acid profile were observed in the chlorhexidine-tolerant cells, primarily the cyclic fatty acids. Transmission electron microscopy revealed more prominent changes in the cell envelope of chlorhexidine-susceptible MT51 cells. This study suggests that multiple mechanisms involving both the cell envelope (and likely TolQ) and panmetabolic regulation play roles in chlorhexidine tolerance in D. acidovorans. IMPORTANCE Delftia acidovorans has been associated with a number of serious infections, including bacteremia, empyema, bacterial endocarditis, and ocular and urinary tract infections. It has also been linked with a variety of surface-associated nosocomial infections. Biofilm-forming antimicrobial-resistant D. acidovorans strains have also been isolated, including ones displaying resistance to the common broad-spectrum agent chlorhexidine. The mechanisms of chlorhexidine resistance in D. acidovorans are not known; hence, a chlorhexidine-susceptible mutant of the tolerant wild-type strain was obtained using transposon mutagenesis, and the proteome and ultrastructural changes of both strains were compared under chlorhexidine challenge.

Delftia acidovorans: A rare pathogen in immunocompetent and immunocompromised patients

Delftia acidovorans is an aerobic, nonfermenting Gram-negative bacillus. It is usually a nonpathogenic environmental organism and is rarely clinically significant. Although D acidovorans infection most commonly occurs in hospitalized or immunocompromised patients, there are also several reports documenting the infection in immunocompetent patients. The present article describes a B cell lymphoblastic leukemia patient with D acidovorans pneumonia who was successfully treated with antibiotic therapy. The present report indicates that unusual pathogens may be clinically significant in both immunocompromised and immunocompetent patients. D acidovorans is often resistant to aminoglycosides; therefore, rapid detection of this microorganism is important.

Fatal Delftia acidovorans infection in an immunocompetent patient with empyema

Delftia acidovorans (earlier known as Comamonas acidovorans) is an aerobic, non-fermentative, Gram negative rod, classified in the Pseudomonas rRNA homology Group III. Reports of isolation of the organism from serious infections like central venous catheter associated bacteremia, corneal ulcers, otitis media exist. The microbiologists can identify this organism based on an orange indole reaction. This reaction demonstrates the organism's ability to produce anthranilic acid from tryptophan on addition of Kovac's reagent; which gives the media its characteristic "pumpkin orange" colour. Here we report the isolation of this organism from the Endotracheal tube aspirate of a 4 year old child. With the increasing use of invasive devices, it has become important to recognize these non fermentative gram negative bacilli as emerging source of infection even in immunocompetent individuals.

Delftia acidovorans as an Unusual Causative Organism in Line-Related Sepsis

The problem of line-related sepsis in patients undergoing chemotherapy for malignant disease remains a major problem in cancer-care even into the third millennium. We report a highly unusual pathogen which represented both a diagnostic and treatment challenge and highlights important issues around patient education as well as laboratory capability in the identification of causative organisms in line-related infections to facilitate clinical management.