PubMed · 2798147
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D M Heery, L K Dunican. 1989-10-11. Improved efficiency M13 cloning using electroporation.. https://doi.org/10.1093/nar%2F17.19.8006
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BACKGROUND: Aeromonas species are ubiquitous aquatic bacteria that have emerged as significant foodborne enteric pathogens worldwide, yet their genomic landscape in clinical settings remains poorly delineated, particularly in Beijing. METHODS: To address this gap, we performed active surveillance for Aeromonas among 691 consecutive diarrheal outpatients in a Beijing district from January to December 2024. Isolates were recovered using enrichment culture coupled with PCR screening and identified by MALDI-TOF MS. Antimicrobial susceptibility was tested against 17 agents. Whole-genome sequencing was conducted on all isolates, enabling average nucleotide identity (ANI) analysis, comprehensive annotation of antimicrobial resistance and virulence genes, multilocus sequence typing (MLST), and core-genome SNP (cgSNP)-based phylogenetics. RESULTS: Aeromonas was detected in 3.3% (23/691) of patients, with Aeromonas veronii (56.52%, 13/23) and Aeromonas caviae (26.09%, 6/23) predominating. Co-infections with other enteric pathogens occurred in 65.2% of positive cases. Resistance rates were notably high for ampicillin/ampicillin-sulbactam (78.26%), nalidixic acid (56.52%), and ertapenem (21.73%), and 65.21% of isolates were multidrug-resistant. Genotypic-phenotypic concordance was robust, with β-lactamase genes ampS (60.87%) and blaCEPH-A3 (47.83%) being most prevalent. Strikingly, mcr-3.25 and mcr-3.3, which belong to the mcr family (originally described as mobile colistin resistance genes), were identified in 8.70% of isolates, exhibiting perfect correlation with phenotypic resistance. Plasmer analysis suggested both mcr genes to be chromosomally encoded. Comparative genomic analysis of virulence-associated genes revealed striking species-specific specialization: A. veronii predominantly carried complete T3SS clusters (61.5%), A. caviae and Aeromonas enteropelogenes were enriched in T6SS genes, and a single A. dhakensis isolate possessed an extensive arsenal including T3SS, T6SS, and a full RTX toxin cluster. MLST resolved the 23 isolates into 22 sequence types, 18 of which were novel. Phylogenetic reconstruction identified a tight monophyletic cluster of three A. veronii isolates (9-27 SNP differences) recovered within a 96-h window, suggestive of a potential cluster that warrants further epidemiological investigation. Comparative genomic analysis of the rare species Aeromonas allosaccharophila demonstrated that the Beijing clinical isolate S14 differs from the U.S. clinical strain ATCC 35942 by 42,099 SNPs, confirming its distinct genetic lineage. CONCLUSION: Collectively, this study delineates high genetic diversity, emerging chromosomal colistin resistance, and species-specific virulence specialization among Aeromonas isolates from diarrheal patients in Beijing. The detection of a potential outbreak cluster and a rare clinical isolate underscores the power of genomics-based surveillance for detecting and mitigating foodborne pathogen threats.
Aeromonas is an opportunistic pathogen, which, although in low numbers, may be present on minimally processed vegetables. Although the intrinsic and extrinsic factors of minimally processed prepacked vegetable mixes are not inhibitory to the growth of Aeromonas species, multiplication to high numbers during processing and storage of naturally contaminated grated carrots, mixed lettuce, and chopped bell peppers was not observed. Aeromonas was shown to be resistant towards chlorination of water, but was susceptible to 1% and 2% lactic acid and 0.5% and 1.0% thyme essential oil treatment, although the latter provoked adverse sensory properties when applied for decontamination of chopped bell peppers. Integration of a decontamination step with 2% lactic acid in the processing line of grated carrots was shown to have the potential to control the overall microbial quality of the grated carrots and was particularly effective towards Aeromonas.
Single crystals of purified homodimeric controller protein from Aeromonas hydrophilia (C.AhdI) have been grown under several different conditions using vapour diffusion. X-ray diffraction data have been collected using synchrotron radiation from crystals of both the native and a selenomethionine (SeMet) derivative of the protein. The native crystal form belongs to space group P2(1) and data were collected to a resolution of 2.2 A. Two crystal forms of the SeMet protein have been obtained and were found to belong to space groups P1 and P2(1); data have been recorded to 2.0 and 1.7 A resolution, respectively, for the two crystal forms. Three-wavelength MAD data were collected to 1.7 A for the SeMet derivative crystal, which is isomorphous with the native P2(1) crystal.