First report of multidrug-resistant carbapenemase-producing Aeromonas caviae co-harboring mcr-3.43 and mcr-7.2.

Hospital sewage serves as a crucial reservoir for antibiotic resistance genes. As colistin and carbapenems are the last-resort antibiotics, the emergence of their resistance genes has become a significant concern in clinical settings. In this study, we found that two novel mcr alleles (mcr-3.43 and mcr-7.2) with two carbapenemase genes (blaNDM-1 and blaKPC-2) were encoded in a single Aeromonas caviae strain isolated from hospital sewage. Our phylogenetic analysis revealed that the mcr-3.43 gene clustered with mcr-3.17 (with 95.55% amino acid identity), while the mcr-7.2 gene clustered with mcr-7.1 (with 68.68% amino acid identity). BLAST search against GenBank showed that mcr-7.2 was exclusively detected in Aeromonas spp. Mobile genetic elements were not found in the genetic context of mcr-7.2, suggesting that the dissemination of mcr-7.2 in Aeromonas spp. may be dependent on vertical transfer or recombination. The blaNDM-1 was adjacent to a recombinase gene and flanked by two IS91 elements, indicating a potential mobilization mechanism mediated by recombination and/or ISs. The blaKPC-2 gene was located on an IncU plasmid and adjacent to an ISKpn6. In summary, our study provides evidence for Aeromonas spp. as one of the potential reservoirs of colistin and carbapenem resistance genes.IMPORTANCEThe study discovered two novel mcr genes (mcr-3.43 and mcr-7.2) and two carbapenemase genes (blaNDM-1 and blaKPC-2) in a single Aeromonas caviae strain retrieved from hospital sewage. Using phylogenetic analysis and comparative data evaluation, the study revealed the genetic relatedness and dissemination potential of the detected resistance genes. With the exclusive discovery that mcr-7.2 is only present in Aeromonas spp. and the lack of mobile genetic elements in its genetic context, there is a strong indication of limited dissemination. The identification of these four resistance genes in a single strain of Aeromonas provided valuable insights into their potential presence in this genus. This study revealed that hospital sewage functions as a significant reservoir for antibiotic resistance genes, including colistin and carbapenem resistance genes.

Virulence and antimicrobial resistance potential of Aeromonas spp. associated with shellfish.

Aeromonas spp. are associated with seafood-related outbreaks worldwide. In seafood industry, shellfish play a major role in global seafood production. With this emerging trend of shellfish consumption, shellfish-related bacterial infections are being reported frequently. Aeromonas spp. are natural contaminants found in shellfish. Although 36 species have been identified, some species including Aeromonas hydrophila, Aeromonas caviae and Aeromonas veronii biotype sobria have dragged major attention as foodborne pathogenic bacteria. The ability to elaborate a variety of virulence factors of Aeromonas spp. contributes to the pathogenic activities. Also, emerging antimicrobial resistance in Aeromonas spp. has become a huge challenge in seafood industry. Furthermore, multidrug resistance increases the risk of consumer health. Studies have supplied pieces of evidence about the emerging health risk of Aeromonas spp. isolated from seafood. Therefore, the present review was intended to highlight the prevalence, virulence and antimicrobial resistance of Aeromonas spp. isolated from various types of shellfish.

Pharmacological properties of some mangrove sediment-associated bacillus isolates.

Mangrove sediment-associated bacteria are of significantly important in the field of medicine and pharmaceuticals as new promising sources of biologically active pharmacophores due to the extreme conditions, such as high salt concentration and soil anoxia. The sediment bacteria associated with Acanthus ilicifolius and Avicennia officinalis collected from the Mangalavanam mangrove ecosystem of the Kerala State of India were evaluated using various in vitro models for the assessment of their pharmacological properties. The bacteria exhibiting significant antioxidant and antimicrobial activities were isolated, identified, and characterized by the integrated microbiological, biochemical, and 16S rRNA sequencing. Among the varied bacteria isolated from mangrove sediments, Bacillus amyloliquefaciens MBMS5 (GenBank accession number MK765025) exhibited significant antimicrobial activities against various pathogenic bacteria, such as Aeromonas caviae, Vibrio parahemolyticus, and methicillin-resistant Staphylococcus aureus. The extracellular extracts of B. amyloliquefaciens MBMS5 exhibited potential antioxidant activity against free radical species coupled with anti-inflammatory property as displayed by the attenuation activity against pro-inflammatory 5-lipoxygenase.

Marine bacteria associated with shallow hydrothermal systems in the Gulf of California with the capacity to produce biofilm inhibiting compounds.

Shallow hydrothermal systems are extreme environments. The sediments and fluids emitted from the vents present unusual physical and chemical conditions compared to other marine areas, which promotes unique biodiversity that has been of great interest for biotechnology for some years. In this work, a bioprospective study was carried out to evaluate the capacity of bacteria associated with shallow hydrothermal vents to produce biofilm-inhibiting compounds. Degradation assays of N-acyl homoserine lactone (AHL) autoinducers (C6HSL) involved in the quorum sensing process were carried out on 161 strains of bacteria isolated from three shallow hydrothermal systems located in Baja California Sur (BCS), Mexico. The biosensor Chromobacterium violaceum CV026 was used. Twenty-three strains showed activity, and organic extracts were obtained with ethyl acetate. The potential of the extracts to inhibit the formation of biofilms was tested against two human pathogenic strains (Pseudomonas aeruginosa PAO1 and Aeromonas caviae ScH3), a shrimp pathogen (Vibrio parahaemolyticus M8), and two marine strains identified as producing biofilms on submerged surfaces (Virgibacillus sp C29 and Vibrio alginolyticus C96). The results showed that Vibrio alginolyticus and Brevibacillus thermoruber, as well as some thermotolerant strains (mostly Bacillus), produce compounds that inhibit bacterial biofilms (B. licheniformis, B. paralicheniformis, B. firmus, B. oceanizedimenis, B. aerius and B. sonorensis).

A potential alternative to traditional antibiotics in aquaculture: Yeast glycoprotein exhibits antimicrobial effect in vivo and in vitro on Aeromonas caviae isolated from Carassius auratus gibelio.

In aquaculture, antibiotics are commonly used to provide protection against pathogens; however, this practice has become controversial due to increased occurrences of microbial resistance, and alternatives are needed. This study aimed to investigate the antimicrobial activity of yeast glycoprotein (YG) against Aeromonas caviae. Pathogens were isolated from liver of diseased Carassius auratus gibelio. Based on morphological and biochemical analysis, together with 16S rRNA gene sequencing, the isolated strains were identified as A. caviae and concluded as clones of a single strain and named L2. Further pathogenicity analysis revealed that A. caviae possessed ß-haemolysis, and its median lethal dose for C. gibelio was 1.33 × 106  CFU/ml. Hepatic adenylate kinase and pyruvate kinase activities of C. gibelio were inhibited post-A. caviae infection. Antimicrobial drug test suggested that A. caviae was a multidrug-resistant organism but could be inhibited by YG in vitro. Minimum inhibitory and bactericidal concentration of YG was 83.3 mg/ml and 166.7 mg/ml, respectively. Microbiota sequencing results showed that YG supplement could obviously decrease the relative abundance of Aeromonas and increase the microbial diversity. Our study revealed that A. caviae from C. gibelio was a multidrug-resistant bacteria strain, and could be significantly inhibited by YG in vivo and in vitro, thus providing important insights into ecological control and pathogenesis of A. caviae in aquaculture.

Potential KPC-2 carbapenemase reservoir of environmental Aeromonas hydrophila and Aeromonas caviae isolates from the effluent of an urban wastewater treatment plant in Japan.

Aeromonas hydrophila and Aeromonas caviae adapt to saline water environments and are the most predominant Aeromonas species isolated from estuaries. Here, we isolated antimicrobial-resistant (AMR) Aeromonas strains (A. hydrophila GSH8-2 and A. caviae GSH8M-1) carrying the carabapenemase blaKPC-2 gene from a wastewater treatment plant (WWTP) effluent in Tokyo Bay (Japan) and determined their complete genome sequences. GSH8-2 and GSH8M-1 were classified as newly assigned sequence types ST558 and ST13, suggesting no supportive evidence of clonal dissemination. The strains appear to have acquired blaKPC-2 -positive IncP-6-relative plasmids (pGSH8-2 and pGSH8M-1-2) that share a common backbone with plasmids in Aeromonas sp. ASNIH3 isolated from hospital wastewater in the United States, A. hydrophila WCHAH045096 isolated from sewage in China, other clinical isolates (Klebsiella, Enterobacter and Escherichia coli), and wastewater isolates (Citrobacter, Pseudomonas and other Aeromonas spp.). In addition to blaKPC-2 , pGSH8M-1-2 carries an IS26-mediated composite transposon including a macrolide resistance gene, mph(A). Although Aeromonas species are opportunistic pathogens, they could serve as potential environmental reservoir bacteria for carbapenemase and AMR genes. AMR monitoring from WWTP effluents will contribute to the detection of ongoing AMR dissemination in the environment and might provide an early warning of potential dissemination in clinical settings and communities.

Proteomic characterization and discrimination of Aeromonas species recovered from meat and water samples with a spotlight on the antimicrobial resistance of Aeromonas hydrophila.

Aeromonas is recognized as a human pathogen following ingestion of contaminated food and water. One major problem in Aeromonas identification is that certain species are phenotypically very similar. The antimicrobial resistance is another significant challenge worldwide. We therefore aimed to use mass spectrometry technology for identification and discrimination of Aeromonas species and to screen the antimicrobial resistance of Aeromonas hydrophila (A. hydrophila). A total of 150 chicken meat and water samples were cultured, and then, the isolates were identified biochemically by the Vitek® 2 Compact system. Proteomic identification was performed by MALDI-TOF MS and confirmed by a microchannel fluidics electrophoresis assay. Principal component analysis (PCA) and single-peak analysis created by MALDI were also used to discriminate the Aeromonas species. The antimicrobial resistance of the A. hydrophila isolates was determined by Vitek® 2 AST cards. In total, 43 samples were positive for Aeromonas and comprised 22 A. hydrophila, 12 Aeromonas caviae (A. caviae), and 9 Aeromonas sobria (A. sobria) isolates. Thirty-nine out of 43 (90.69%) Aeromonas isolates were identified by the Vitek® 2 Compact system, whereas 100% of the Aeromonas isolates were correctly identified by MALDI-TOF MS with a score value ≥2.00. PCA successfully separated A. hydrophila, A. caviae and A. sobria isolates into two groups. Single-peak analysis revealed four discriminating peaks that separated A. hydrophila from A. caviae and A. sobria isolates. The resistance of A. hydrophila to antibiotics was 95.46% for ampicillin, 50% for cefotaxime, 45.45% for norfloxacin and pefloxacin, 36.36% for ceftazidime and ciprofloxacin, 31.81% for ofloxacin and 27.27% for nalidixic acid and tobramycin. In conclusion, chicken meat and water were tainted with Aeromonas spp., with a high occurrence of A. hydrophila. MALDI-TOF MS is a powerful technique for characterizing aeromonads at the genus and species levels. Future studies should investigate the resistance of A. hydrophila to various antimicrobial agents.

Síndrome hemolítico-urémico causado por Aeromona caviae en un paciente pediátrico / Hemolytic uremic syndrome caused by Aeromona caviae in a pediatric patient

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Genetic characterization and potential molecular dissemination mechanism of tet(31) gene in Aeromonas caviae from an oxytetracycline wastewater treatment system.

Recently, the rarely reported tet(31) tetracycline resistance determinant was commonly found in Aeromonas salmonicida, Gallibacterium anatis, and Oblitimonas alkaliphila isolated from farming animals and related environment. However, its distribution in other bacteria and potential molecular dissemination mechanism in environment are still unknown. The purpose of this study was to investigate the potential mechanism underlying dissemination of tet(31) by analysing the tet(31)-carrying fragments in A. caviae strains isolated from an aerobic biofilm reactor treating oxytetracycline bearing wastewater. Twenty-three A. caviae strains were screened for the tet(31) gene by polymerase chain reaction (PCR). Three strains (two harbouring tet(31), one not) were subjected to whole genome sequencing using the PacBio RSII platform. Seventeen A. caviae strains carried the tet(31) gene and exhibited high resistance levels to oxytetracycline with minimum inhibitory concentrations (MICs) ranging from 256 to 512 mg/L. tet(31) was comprised of the transposon Tn6432 on the chromosome of A. caviae, and Tn6432 was also found in 15 additional tet(31)-positive A. caviae isolates by PCR. More important, Tn6432 was located on an integrative conjugative element (ICE)-like element, which could mediate the dissemination of the tet(31)-carrying transposon Tn6432 between bacteria. Comparative analysis demonstrated that Tn6432 homologs with the structure ISCR2-∆phzF-tetR(31)-tet(31)-∆glmM-sul2 were also carried by A. salmonicida, G. anatis, and O. alkaliphila, suggesting that this transposon can be transferred between species and even genera. This work provides the first report on the identification of the tet(31) gene in A. caviae, and will be helpful in exploring the dissemination mechanisms of tet(31) in water environment.

Design, Synthesis, and Evaluation of Alkyl-Quinoxalin-2(1H)-One Derivatives as Anti-Quorum Sensing Molecules, Inhibiting Biofilm Formation in Aeromonas caviae Sch3.

With the increasing antibiotic resistance of bacterial strains, alternative methods for infection control are in high demand. Quorum sensing (QS) is the bacterial communication system based on small molecules. QS is enables bacterial biofilm formation and pathogenic development. The interruption of QS has become a target for drug discovery, but remains in the early experimental phase. In this study, we synthesized a set of six compounds based on a scaffold (alkyl-quinoxalin-2(1H)-one), new in the anti-QS of Gram-negative bacteria Aeromonas caviae Sch3. By quantifying biofilm formation, we were able to monitor the effect of these compounds from concentrations of 1 to 100 µM. Significant reduction in biofilm formation was achieved by 3-hexylylquinoxalin-2(1H)-one (11), 3-hexylylquinoxalin-2(1H)-one-6-carboxylic acid (12), and 3-heptylylquinoxalin-2(1H)-one-6-carboxylic acid (14), ranging from 11% to 59% inhibition of the biofilm. This pilot study contributes to the development of anti-QS compounds to overcome the clinical challenge of resistant bacteria strains.

Tetrahymena promotes interactive transfer of carbapenemase gene encoded in plasmid between fecal Escherichia coli and environmental Aeromonas caviae.

Tetrahymena can facilitate plasmid transfer among Escherichia coli or from E. coli to Salmonella Enteritidis via vesicle accumulation. In this study, whether ciliates promote the interactive transfer of plasmids encoding blaIMP-1 between fecal E. coli and environmental Aeromonas caviae was investigated. Both bacteria were mixed with or without ciliates and incubated overnight at 30°C. The frequency of plasmid-acquired bacteria was estimated by colony counts using an agar plate containing ceftazidim (CAZ) followed by determination of the minimum inhibitory concentration (MIC). Cultures containing ciliates interactively transferred the plasmid between E. coli and Aeromonas with a frequency of 10-4 to 10-5 . All plasmid-acquired bacteria showed a MIC against CAZ of >128 µg/mL and the plasmid transfer was confirmed by PCR amplification of the blaIMP-1 gene. Fluorescent observation showed that both bacteria accumulated in the same vesicle and that transwell sequestering significantly decreased the transfer frequency. Although ciliates preferentially ingested E. coli rather than A. caviae, both bacteria were co-localized into the same vesicles of ciliates, indicating that their meeting is associated with the gene transfer. Thus, ciliates interactively promote plasmid transfer between E. coli and A. caviae. The results of this study will facilitate control of the spread of multiple-antibiotic resistant bacteria.

First report of blaOXA-181-mediated carbapenem resistance in Aeromonas caviae in association with pKP3-A: Threat for rapid dissemination.

OBJECTIVES: Carbapenemase-producing Aeromonas spp. are of great concern in healthcare settings and are also known to acquire clinically relevant resistance genes. In this study, carbapenem-non-susceptible Aeromonas isolates were characterised for their molecular mechanisms of resistance. METHODS: Among 180 Aeromonas isolates, 10 carbapenem-non-susceptible isolates were selected based on their antimicrobial susceptibility profile. Carbapenemase production was investigated by the CarbaNP test. ESBL-, AmpC- and carbapenemase-encoding genes were screened by PCR. Isolates VBF557 and VBF856 with high MICs for imipenem were selected for whole-genome sequencing (WGS). Conjugation experiments were performed to determine the transmissibility of resistance. RESULTS: WGS remarkably revealed the presence of class D ß-lactamases (AmpS/AmpH), class C ß-lactamases and class B2 metallo-ß-lactamase (cphA3) in VBF557. In contrast, VBF856 had multiple resistance genes coding for aminoglycoside, sulphonamide, carbapenem (blaOXA-181 class D ß-lactamase), macrolide, fluoroquinolone, rifampicin, phenicol, tetracycline and trimethoprim resistance. This is the first global report of blaOXA-181 in Aeromonas spp. Interestingly, blaOXA-181 was identified in association with transposon Tn2013 in plasmid pKP3-A. Additionally, an IncQ2 plasmid with qnrS2 was identified. Among the tested isolates, VBF1116 and VBF888 possessed blaNDM and blaVEB, respectively, by PCR. None of the other isolates harboured any tested ß-lactamase genes. The resistance gene was transmissible in the presence of imipenem. CONCLUSIONS: Presence of such resistance genes in plasmids further adds complexity for control of spread of carbapenem resistance. This study reveals the emergence of carbapenem resistance among Aeromonas spp. and the importance of mobile genetic elements such as plasmids in interchanging resistance determinants between species.

Pan-genome analysis of Aeromonas hydrophila, Aeromonas veronii and Aeromonas caviae indicates phylogenomic diversity and greater pathogenic potential for Aeromonas hydrophila.

Aeromonas species are important pathogens of fishes and aquatic animals capable of infecting humans and other animals via food. Due to the paucity of pan-genomic studies on aeromonads, the present study was undertaken to analyse the pan-genome of three clinically important Aeromonas species (A. hydrophila, A. veronii, A. caviae). Results of pan-genome analysis revealed an open pan-genome for all three species with pan-genome sizes of 9181, 7214 and 6884 genes for A. hydrophila, A. veronii and A. caviae, respectively. Core-genome: pan-genome ratio (RCP) indicated greater genomic diversity for A. hydrophila and interestingly RCP emerged as an effective indicator to gauge genomic diversity which could possibly be extended to other organisms too. Phylogenomic network analysis highlighted the influence of homologous recombination and lateral gene transfer in the evolution of Aeromonas spp. Prediction of virulence factors indicated no significant difference among the three species though analysis of pathogenic potential and acquired antimicrobial resistance genes revealed greater hazards from A. hydrophila. In conclusion, the present study highlighted the usefulness of whole genome analyses to infer evolutionary cues for Aeromonas species which indicated considerable phylogenomic diversity for A. hydrophila and hitherto unknown genomic evidence for pathogenic potential of A. hydrophila compared to A. veronii and A. caviae.

Analysis of the Structure and Function of FOX-4 Cephamycinase.

Class C ß-lactamases poorly hydrolyze cephamycins (e.g., cefoxitin, cefotetan, and moxalactam). In the past 2 decades, a new family of plasmid-based AmpC ß-lactamases conferring resistance to cefoxitin, the FOX family, has grown to include nine unique members descended from the Aeromonas caviae chromosomal AmpC. To understand the basis for the unique cephamycinase activity in the FOX family, we determined the first X-ray crystal structures of FOX-4, apo enzyme and the acyl-enzyme with its namesake compound, cefoxitin, using the Y150F deacylation-deficient variant. Notably, recombinant expression of N-terminally tagged FOX-4 also yielded an inactive adenylylated enzyme form not previously observed in ß-lactamases. The posttranslational modification (PTM), which occurs on the active site Ser64, would not seem to provide a selective advantage, yet might present an opportunity for the design of novel antibacterial drugs. Substantial ligand-induced changes in the enzyme are seen in the acyl-enzyme complex, particularly the R2 loop and helix H10 (P289 to N297), with movement of F293 by 10.3 Å. Taken together, this study provides the first picture of this highly proficient class C cephamycinase, uncovers a novel PTM, and suggests a possible cephamycin resistance mechanism involving repositioning of the substrate due to the presence of S153P, N289P, and N346I substitutions in the ligand binding pocket.

On the mechanism underlying tellurite reduction by Aeromonas caviae ST dihydrolipoamide dehydrogenase.

The dihydrolipoamide dehydrogenase (LpdA) from the tellurite-resistant bacterium Aeromonas caviae ST reduces tellurite to elemental tellurium. To characterize this NADH-dependent activity, the A. caviae lpdA gene was subjected to site-directed mutagenesis and genes containing C45A, H322Y and E354K substitutions were individually transformed into Escherichia coli Δlpd. Cells expressing the modified genes exhibited decreased pyruvate dehydrogenase, dihydrolipoamide dehydrogenase and TR activity regarding that observed with the wild type A. caviae lpdA gene. In addition, cells expressing the altered lpdA genes showed increased oxidative stress levels and tellurite sensitivity than those carrying the wild type counterpart. The involvement of Cys residues in LpdA's TR activity was analyzed using specific inhibitors that interact with catalytic cysteines and/or disulfide bridges such as aurothiomalate, zinc or nickel. TR activity of purified LpdA was drastically affected by these compounds. Since LpdA belongs to the flavoprotein family, the involvement of the FAD/NAD(P)(+)-binding domain in TR activity was determined. FAD removal from purified LpdA results in loss of TR activity, which was restored with exogenously added FAD. Substitutions in E354, involved in FAD/NADH binding, resulted in low TR activity because of flavin loss. Finally, changing H322 (involved in NAD(+)/NADH binding) by tyrosine also resulted in altered TR activity.

Different clinical characteristics among Aeromonas hydrophila, Aeromonas veronii biovar sobria and Aeromonas caviae monomicrobial bacteremia.

This study aimed to compare the clinical presentations of Aeromonas hydrophila, A. veronii biovar sobria and A. caviae monomicrobial bacteremia by a retrospective method at three hospitals in Taiwan during an 8-yr period. There were 87 patients with A. hydrophila bacteremia, 45 with A. veronii biovar sobria bacteremia and 22 with A. caviae bacteremia. Compared with A. hydrophila and A. veronii biovar sobria bacteremia, A. caviae bacteremia was more healthcare-associated (45 vs 30 and 16%; P = 0.031). The patients with A. caviae bacteremias were less likely to have liver cirrhosis (27 vs 62 and 64%; P = 0.007) and severe complications such as shock (9 vs 40 and 47%; P = 0.009) and thrombocytopenia (45 vs 67 and 87%; P = 0.002). The APACHE II score was the most important risk factor of Aeromonas bacteremia-associated mortalities. The APACHE II scores of A. caviae bacteremias were lower than A. hydrophila bacteremia and A. veronii biovar sobria bacteremia (7 vs 14 and 16 points; P = 0.002). In conclusion, the clinical presentation of A. caviae bacteremia was much different from A. hydrophila and A. veronii biovar sobria bacteremia. The severity and mortality of A. caviae bacteremia were lower than A. hydrophila or A. veronii biovar sobria bacteremia.

Bacteremia due to extended-spectrum-ß-lactamase-producing Aeromonas spp. at a medical center in Southern Taiwan.

Although extended-spectrum-ß-lactamase (ESBL)-producing aeromonads have been increasingly reported in recent years, most of them were isolates from case reports or environmental isolates. To investigate the prevalence of ESBL producers among Aeromonas blood isolates and the genes encoding ESBLs, consecutive nonduplicate Aeromonas blood isolates collected at a medical center in southern Taiwan from March 2004 to December 2008 were studied. The ESBL phenotypes were examined by clavulanate combination disk test and the cefepime-clavulanate ESBL Etest. The presence of ESBL-encoding genes, including bla(TEM), bla(PER), bla(CTX-M), and bla(SHV) genes, was evaluated by PCR and sequence analysis. The results showed that 4 (2.6%) of 156 Aeromonas blood isolates, 1 Aeromonas hydrophila isolate and 3 Aeromonas caviae isolates, expressed an ESBL-producing phenotype. The ESBL gene in two A. caviae isolates was bla(PER-3), which was located in both chromosomes and plasmids, as demonstrated by Southern hybridization. Of four patients with ESBL-producing Aeromonas bacteremia, two presented with catheter-related phlebitis and the other two with primary bacteremia. Three patients had been treated with initial noncarbapenem ß-lactams for 5 to 10 days, and all survived. In conclusion, ESBL producers exist among Aeromonas blood isolates, and clinical suspicion of ESBL production should be raised in treating infections due to cefotaxime-resistant Aeromonas isolates.

Different Clinical Characteristics Among Aeromonas hydrophila, Aeromonas veronii biovar sobria and Aeromonas caviae Monomicrobial Bacteremia

This study aimed to compare the clinical presentations of Aeromonas hydrophila, A. veronii biovar sobria and A. caviae monomicrobial bacteremia by a retrospective method at three hospitals in Taiwan during an 8-yr period. There were 87 patients with A. hydrophila bacteremia, 45 with A. veronii biovar sobria bacteremia and 22 with A. caviae bacteremia. Compared with A. hydrophila and A. veronii biovar sobria bacteremia, A. caviae bacteremia was more healthcare-associated (45 vs 30 and 16%; P = 0.031). The patients with A. caviae bacteremias were less likely to have liver cirrhosis (27 vs 62 and 64%; P = 0.007) and severe complications such as shock (9 vs 40 and 47%; P = 0.009) and thrombocytopenia (45 vs 67 and 87%; P = 0.002). The APACHE II score was the most important risk factor of Aeromonas bacteremia-associated mortalities. The APACHE II scores of A. caviae bacteremias were lower than A. hydrophila bacteremia and A. veronii biovar sobria bacteremia (7 vs 14 and 16 points; P = 0.002). In conclusion, the clinical presentation of A. caviae bacteremia was much different from A. hydrophila and A. veronii biovar sobria bacteremia. The severity and mortality of A. caviae bacteremia were lower than A. hydrophila or A. veronii biovar sobria bacteremia.