Identifying the mechanisms underlying the protective effect of tetramethylpyrazine against cisplatin‑induced in vitro ototoxicity in HEI‑OC1 auditory cells using gene expression profiling

The mobile gene cassette carrying tetracycline resistance genes in Aeromonas veronii strain Ah5S-24 isolated from catfish pond sediments shows similarity with a cassette found in other environmental and foodborne bacteria

Aeromonas veronii is a Gram-negative bacterium ubiquitously found in aquatic environments. It is a foodborne pathogen that causes diarrhea in humans and hemorrhagic septicemia in fish. In the present study, we used whole-genome sequencing (WGS) to evaluate the presence of antimicrobial resistance (AMR) and virulence genes found in A. veronii Ah5S-24 isolated from catfish pond sediments in South-East, United States. We found cphA4, dfrA3, mcr-7.1, valF, blaFOX-7, and blaOXA-12 resistance genes encoded in the chromosome of A. veronii Ah5S-24. We also found the tetracycline tet(E) and tetR genes placed next to the IS5/IS1182 transposase, integrase, and hypothetical proteins that formed as a genetic structure or transposon designated as IS5/IS1182/hp/tet(E)/tetR/hp. BLAST analysis showed that a similar mobile gene cassette (MGC) existed in chromosomes of other bacteria species such as Vibrio parahaemolyticus isolated from retail fish at markets, Aeromonas caviae from human stool and Aeromonas media from a sewage bioreactor. In addition, the IS5/IS1182/hp/tet(E)/tetR/hp cassette was also found in the plasmid of Vibrio alginolyticus isolated from shrimp. As for virulence genes, we found the tap type IV pili (tapA and tapY), polar flagellae (flgA and flgN), lateral flagellae (ifgA and IfgL), and fimbriae (pefC and pefD) genes responsible for motility and adherence. We also found the hemolysin genes (hylII, hylA, and TSH), aerA toxin, biofilm formation, and quorum sensing (LuxS, mshA, and mshQ) genes. However, there were no MGCs encoding virulence genes found in A. veronii AhS5-24. Thus, our findings show that MGCs could play a vital role in the spread of AMR genes between chromosomes and plasmids among bacteria in aquatic environments. Overall, our findings are suggesting that MGCs encoding AMR genes could play a vital role in the spread of resistance acquired from high usage of antimicrobials in aquaculture to animals and humans.

Characterization of virulence and antimicrobial resistance genes of Aeromonas media strain SD/21-15 from marine sediments in comparison with other Aeromonas spp

Aeromonas media is a Gram-negative bacterium ubiquitously found in aquatic environments. It is a foodborne pathogen associated with diarrhea in humans and skin ulceration in fish. In this study, we used whole genome sequencing to profile all antimicrobial resistance (AMR) and virulence genes found in A. media strain SD/21-15 isolated from marine sediments in Denmark. To gain a better understanding of virulence and AMR genes found in several A. media strains, we included 24 whole genomes retrieved from the public databanks whose isolates originate from different host species and environmental samples from Asia, Europe, and North America. We also compared the virulence genes of strain SD/21-15 with A. hydrophila, A. veronii, and A. salmonicida reference strains. We detected Msh pili, tap IV pili, and lateral flagella genes responsible for expression of motility and adherence proteins in all isolates. We also found hylA, hylIII, and TSH hemolysin genes in all isolates responsible for virulence in all isolates while the aerA gene was not detected in all A. media isolates but was present in A. hydrophila, A. veronii, and A. salmonicida reference strains. In addition, we detected LuxS and mshA-Q responsible for quorum sensing and biofilm formation as well as the ferric uptake regulator (Fur), heme and siderophore genes responsible for iron acquisition in all A. media isolates. As for the secretory systems, we found all genes that form the T2SS in all isolates while only the vgrG1, vrgG3, hcp, and ats genes that form parts of the T6SS were detected in some isolates. Presence of bla MOX-9 and bla OXA-427 β-lactamases as well as crp and mcr genes in all isolates is suggestive that these genes were intrinsically encoded in the genomes of all A. media isolates. Finally, the presence of various transposases, integrases, recombinases, virulence, and AMR genes in the plasmids examined in this study is suggestive that A. media has the potential to transfer virulence and AMR genes to other bacteria. Overall, we anticipate these data will pave way for further studies on virulence mechanisms and the role of A. media in the spread of AMR genes.

Aeromonas species isolated from aquatic organisms, insects, chicken, and humans in India show similar antimicrobial resistance profiles

Aeromonas species are Gram-negative bacteria that infect various living organisms and are ubiquitously found in different aquatic environments. In this study, we used whole genome sequencing (WGS) to identify and compare the antimicrobial resistance (AMR) genes, integrons, transposases and plasmids found in Aeromonas hydrophila, Aeromonas caviae and Aeromonas veronii isolated from Indian major carp (Catla catla), Indian carp (Labeo rohita), catfish (Clarias batrachus) and Nile tilapia (Oreochromis niloticus) sampled in India. To gain a wider comparison, we included 11 whole genome sequences of Aeromonas spp. from different host species in India deposited in the National Center for Biotechnology Information (NCBI). Our findings show that all 15 Aeromonas sequences examined had multiple AMR genes of which the Ambler classes B, C and D β-lactamase genes were the most dominant. The high similarity of AMR genes in the Aeromonas sequences obtained from different host species point to interspecies transmission of AMR genes. Our findings also show that all Aeromonas sequences examined encoded several multidrug efflux-pump proteins. As for genes linked to mobile genetic elements (MBE), only the class I integrase was detected from two fish isolates, while all transposases detected belonged to the insertion sequence (IS) family. Only seven of the 15 Aeromonas sequences examined had plasmids and none of the plasmids encoded AMR genes. In summary, our findings show that Aeromonas spp. isolated from different host species in India carry multiple AMR genes. Thus, we advocate that the control of AMR caused by Aeromonas spp. in India should be based on a One Health approach.

Tetramethylpyrazine: A review on its mechanisms and functions

Ligusticum chuanxiong Hort (known as Chuanxiong in China, CX) is one of the most widely used and long-standing medicinal herbs in China. Tetramethylpyrazine (TMP) is an alkaloid and one of the active components of CX. Over the past few decades, TMP has been proven to possess several pharmacological properties. It has been used to treat a variety of diseases with excellent therapeutic effects. Here, the pharmacological characteristics and molecular mechanism of TMP in recent years are reviewed, with an emphasis on the signal-regulation mechanism of TMP. This review shows that TMP has many physiological functions, including anti-oxidant, anti-inflammatory, and anti-apoptosis properties; autophagy regulation; vasodilation; angiogenesis regulation; mitochondrial damage suppression; endothelial protection; reduction of proliferation and migration of vascular smooth muscle cells; and neuroprotection. At present, TMP is used in treating cardiovascular, nervous, and digestive system conditions, cancer, and other conditions and has achieved good curative effects. The therapeutic mechanism of TMP involves multiple targets, multiple pathways, and bidirectional regulation. TMP is, thus, a promising drug with great research potential.