UNASSIGNED: Aeromonas dhakensis is associated with soft tissue infection, bacteremia and gastroenteritis. Involvement of respiratory system in adults is extremely rare. We report a case of fulminant pneumonia and bacteremia due to A. dhakensis in a patient without underlying diseases.
UNASSIGNED: A 26-year-old man became ill suddenly with pneumonia after swimming in a river. Despite intensive support measures in the intensive care unit, he died 13 hours after admission and 4 days after his first symptoms. Autopsy showed abundant Gram-negative bacteria, massive inflammatory cell infiltration, edema, necrosis and hemorrhage in lung tissue. A. dhakensis was isolated from blood culture taken at admission and bronchoalveolar lavage fluid (BALF) after intubation. Moreover, A. dhakensis was also detected in lung tissue by metagenomic next-generation sequencing (mNGS) assay. The infection may have come from river water.
UNASSIGNED: In patients who develop a fulminant pneumonia after contacting an aquatic environment, A. dhakensis should be alerted and mNGS may aid in the detection of aquatic pathogens by being more sensitive and specific versus traditional bacterial culture.

UNASSIGNED: Aeromonas dhakensis is a gram-negative bacterium. In recent years, Aeromonas dhakensis has gradually attracted increasing attention due to its strong virulence and poor prognosis. Clinical reports of pulmonary infection caused by Aeromonas dhakensis are rare.
UNASSIGNED: A patient with acute T lymphoblastic leukemia experienced myelosuppression after chemotherapy, developed a secondary pulmonary infection with Aeromonas dhakensis and was hospitalized due to fever. The patient underwent testing for inflammatory markers, chest imaging, blood culture, bronchoalveolar lavage, pleural drainage, and metagenomic next-generation sequencing of alveolar lavage fluid and pleural fluid to obtain evidence of Aeromonas dhakensis infection, and was treated with four generations of cephalosporin combined with fluoroquinolone antibiotics. The patient\'s condition significantly improved.
UNASSIGNED: Among pulmonary infectious pathogens, Aeromonas dhakensis is relatively rare. Once an Aeromonas strain is cultured in the clinical work, pathogenic sequencing should be performed on the detected samples for early accurate diagnosis and effective anti-infection treatment.

The Macrobrachium rosenbergii industry is threatened by various Aeromonas, resulting in high mortality of adult prawns. However, there are few studies on the immune response of M. rosenbergii infected with Aeromonas dhakensis. In this study, we observed the hepatopancreas and gills histopathologically, performed a comparative transcriptome analysis of the hepatopancreas, and analyzed the candidate gene expression of immune-related genes in the hemolymph, hepatopancreas, and gills of M. rosenbergii that had been infected with A. dhakensis. Histopathology revealed the hepatopancreas was successively inflamed, followed by cellular vacuolation, lumen deformation, and finally tissue erosion; partial and severe inflammation of the gills occurred successively, and eventually the gill tissue atrophy and the gill filaments detached from the gill arch. Transcriptome analysis showed that a total of 77,742 unigenes and 8664 differentially expressed genes (DEGs), and the immune-related DEGs were mainly enriched in lysosome and phagosome pathways. In addition, 4 immune-related candidate genes (RhoA, CASP9, PKC, and DSCIGN) based on KEGG and PPI analysis were monitored at 6, 12, and 24h post injection (hpi) in hepatopancreas, hemolymph and gills. Their spatio-temporal expression results indicated that A. dhakensis have activated the immune system of M. rosenbergii. The present study may provide new information on the complex immune mechanism of M. rosenbergii.

Genetic editing has revolutionized biotechnology, but delivery of endonuclease genes as DNA can lead to aberrant integration or overexpression, leading to off-target effects. Here, we develop a mechanism to deliver Cre recombinase as a protein by engineering the bacterial type six secretion system (T6SS). Using multiple T6SS fusion proteins, Aeromonas dhakensis or attenuated Vibrio cholerae donor strains, and a gain-of-function cassette for detecting Cre recombination, we demonstrate successful delivery of active Cre directly into recipient cells. The most efficient transfer was achieved using a truncated version of PAAR2 from V. cholerae, resulting in a relatively small (118-amino-acid) delivery tag. We further demonstrate the versatility of this system by delivering an exogenous effector, TseC, enabling V. cholerae to kill Pseudomonas aeruginosa. This implies that P. aeruginosa is naturally resistant to all native effectors of V. cholerae and that the TseC chaperone protein is not required for its activity. Moreover, it demonstrates that the engineered system can improve T6SS efficacy against specific pathogens, proposing future application in microbiome manipulation or as a next-generation antimicrobial. Inexpensive and easy to produce, this protein delivery system has many potential applications, ranging from studying T6SS effectors to genetic editing. IMPORTANCE Delivery of protein-based drugs, antigens, and gene-editing agents has broad applications. The type VI protein secretion system (T6SS) can target both bacteria and eukaryotic cells and deliver proteins of diverse size and function. Here, we harness the T6SS to successfully deliver Cre recombinase to genetically edit bacteria without requiring the introduction of exogenous DNA into the recipient cells. This demonstrates a promising advantage over current genetic editing tools that require transformation or conjugation of DNA. The engineered secretion tag can also deliver a heterologous antimicrobial toxin that kills an otherwise unsusceptible pathogen, Pseudomonas aeruginosa. These results demonstrate the potential of T6SS-mediated delivery in areas including genome editing, killing drug-resistant pathogens, and studying toxin functions.

The study aimed to elucidate the species taxonomy, clinical manifestations, virulence gene profiles and antimicrobial susceptibilities of Aeromonas strains isolated from life-threatening bacteremia in southeastern China.
Clinical samples of Aeromonas causing bacteremia were isolated from a teaching hospital in Wenzhou from 2013 to 2018 and a retrospective cohort study was performed. Aeromonas strains were identified at species level by housekeeping gene gyrB. Virulence and drug resistance-associated genes were screened by polymerase chain reaction (PCR) and antimicrobial susceptibility testing (AST) was performed by the VITEK 2 Compact system.
A total of 58 Aeromonas isolated from patients with bacteremia were collected during 6 years (2013-2018). 58 isolates were identified to five different species, where Aeromonas dhakensis appeared to be the predominant species (26/58), followed by Aeromonas veronii (13/58), Aeromonas caviae (10/58), Aeromonas hydrophila (7/58) and Aeromonas jandaei (2/58). 16 of 58 patients had poor prognosis. Poor prognosis was significantly associated with liver cirrhosis and inappropriate empirical antimicrobials therapy. The progression of bacteremia caused by Aeromonas was extremely fast, especially in A. dhakensis infections. Virulence genes aer, lip, hlyA, alt, ast, and act, were detected at ratios of 24.1% (14/58), 62.1% (36/58), 65.5% (38/58), 58.6% (34/58), 15.5% (9/58) and 65.5% (38/58), respectively. Antimicrobial susceptibility testing exhibited that 9 out of 58 isolates were identified as multi-drug resistant (MDR) organism. The blaTEM gene was identified in all 9 MDR isolates. blaSHV, blaAQU-1, blaMOX, blaCepH, blaCphA and aac(6\')-Ib-cr were detected in 4 isolates, 2 isolates, 1 isolate, 3 isolates, 8 isolates, and 3 isolates, respectively. The majority of Aeromonas strains maintained susceptible to 3rd generation cephalosporins, aminoglycosides, fluoroquinolones and furantoin.
The prevalence and dangerousness of Aeromonas infections, especially A. dhakensis, are underestimated in clinic. Continuous monitoring is essential to keep track of MDR Aeromonas due to the increasing prevalence recently and a more effective measure is required to control the spread of resistance determinants.

Aeromonas dhakensis is an important ubiquitous Gram-negative and freshwater bacterium detected in different reservoirs. It can cause invasive diseases in humans. Herein, we report the first case in Mainland China of a fulminant death of a 29-year-old man as a result of a new, unexpected association between septicemic A. dhakensis and hepatitis B viral infection (HBV). Herein, the patient died from multiple organ failure 5 d postadmission after the ingestion of Snakehead Fish meal. The isolated bacterium was initially misidentified as Aeromonas hydrophila using VITEK-2, while whole-genome sequencing (WGS) revealed that the isolate is A. dhakensis. WGS revealed the occurrence of three antimicrobial genes of resistance: imiH, cphA2, and blaOXA-12; besides, major virulence factors were detected. In silico, multilocus sequence typing (MLST) showed that our A. dhakensis 17FW001 belonged to a novel sequence type (ST557). A comparative genomic analysis of our isolate with nine selected Aeromonas species was done, which elucidated the pathogenicity of our A. dhakensis. In conclusion, we reported for the first time the association between A. dhakensis and HBV in Mainland China. We revealed that septicemic A. dhakensis could result in severe adverse clinical outcomes that end up with unexpected fulminant death especially when it is accompanied with HBV and sheds light on the virulence of A. dhakensis and the high rate of its misdiagnosis that requires to urgently consider screening of all cases of A. dhakensis for HBV in the future. Besides, caution should be taken while dealing with snakeheads which act as a vector for A. dhakensis.