Isolation, identification and characterisation of an emerging fish pathogen, Acinetobacter pittii, from diseased loach (Misgurnus anguillicaudatus) in China

Changes of intestinal barrier in the process of intestinal inflammation induced by Aeromonas hydrophila in snakehead (Channa argus)

Bacterial intestinal inflammation frequently occurs in cultured fish. Nevertheless, research on intestinal barrier dysfunction in the process of intestinal inflammation is deficient. In this study, we explored the changes of intestinal inflammation induced by Aeromonas hydrophila (A. hydrophila) in snakehead and the relationship between intestinal barrier and inflammation. Snakehead [(13.05 ± 2.39) g] were infected via anus with A. hydrophila. Specimens were collected for analysis at 0, 1, 3, 7 and 21 d post-injection. The results showed that with the increase of exposure time, the hindgut underwent stages of normal function, damage, damage deterioration, repair and recovery. Relative to 0 d, the levels of IL-1β and TNF-α in serum, and the expression of nod1, tlr1, tlr5, nf-κb, tnf-α and il-1β in intestine were significantly increased, and showed an upward then downward pattern over time. However, the expression of tlr2 and il-10 were markedly decreased, and showed the opposite trend. In addition, with the development of intestinal inflammation, the diversity and richness of species, and the levels of phylum and genus in intestine were obviously altered. The levels of trypsin, LPS, AMS, T-SOD, CAT, GPx, AKP, LZM and C3 in intestine were markedly reduced, and displayed a trend of first decreasing and then rebounding. The ultrastructure observation showed that the microvilli and tight junction structure of intestinal epithelial cells experienced normal function initially, then damage, and finally recovery over time. The expression of claudin-3 and zo-1 in intestine were significantly decreased, and showed a trend of first decreasing and then rebounding. Conversely, the expression of mhc-i, igm, igt and pigr in intestine were markedly increased, and displayed a trend of increasing first and then decreasing. The above results revealed the changes in intestinal barrier during the occurrence and development of intestinal inflammation, which provided a theoretical basis for explaining the relationship between the two.

Acinetobacter pittii: the emergence of a hospital-acquired pathogen analyzed from the genomic perspective

Acinetobacter pittii has increasingly been associated with several types of hospital-acquired severe infections. Genes implicated in carbapenem resistance, tigecycline resistance, or genes encoding extended spectrum cephalosporinases, such as blaADC, are commonly found in isolates implicated in these infections. A. pittii strains that are pandrug resistant have occasionally been identified. Food for human consumption, animals and plants are environmental sources of this pathogen. An alarming situation is that A. pitti has been identified as responsible for outbreaks in different regions worldwide. In this study, 384 genomes of A. pittii were analyzed, comprising sequences from clinical and non-clinical origins from 32 countries. The objective was to investigate if clinical strains possess genetic traits facilitating hospital adaptation. Results indicate significant genomic variability in terms of size and gene content among A. pittii isolates. The core genome represents a small portion (25-36%) of each isolate's genome, while genes associated with antibiotic resistance and virulence predominantly belong to the accessory genome. Notably, antibiotic resistance genes are encoded by a diverse array of plasmids. As the core genome between environmental and hospital isolates is the same, we can assume that hospital isolates acquired ARGs due to a high selective pressure in these settings. The strain's phylogeographic distribution indicates that there is no geographical bias in the isolate distribution; isolates from different geographic regions are dispersed throughout a core genome phylogenetic tree. A single clade may include isolates from extremely distant geographical areas. Furthermore, strains isolated from the environment or animal, or plant sources frequently share the same clade as hospital isolates. Our analysis showed that the clinical isolates do not already possess specific genes, other than antibiotic-resistant genes, to thrive in the hospital setting.

Pathogenicity and inactivated vaccine treatment of Aeromonas veronii JW-4 on crucian carp

Aeromonas veronii is a common bacterium found in a variety of aquatic environments, capable of causing a diverse array of diseases in both aquatic animals and humans. Therefore, evaluating the pathogenicity of A. veronii and implementing measures to control its spread are essential. In this study, a strain JW-4, identified as A. veronii, was isolated from diseased Scaphesthes macrolepis, a grade Ⅱ protected animal in China. To investigate the pathogenicity of the strain, fish were fed with serial levels JW-4 supplemented diet or basal diet (control group 1, CG1) for 28 days (d). Results showed that JW-4 stimulated an immune response, evidenced by an increase in immune-related enzyme activities (GOT and GPT) of serum and liver and an upregulation of genes expression levels (TNF-α and IFN-γ) of liver and spleen, and these effects gradually decreased over time. Histopathological examination revealed that JW-4 could alter the tissue structure of immune organs, such as liver and kidney. These changes were accompanied by vacuolar degeneration, nuclear dissolution, and an increased lymphocyte count. To assess protective effects of a vaccine against this strain, fish were injected with an inactivated vaccine (immunization group, IG) or 0.85% sterile saline (control group 2, CG2) for 28-day observation period, then challenged with JW-4 on the 28th day. The inactivated vaccine enhanced total and specific IgM to A. veronii levels of the fish, resulting in a relative percentage survival of 75% in IG. These findings provide a foundation for identifying pathogenic bacteria and developing more effective prophylactic strategies in aquaculture.

Incorporation of zinc sulfide nanoparticles, Acinetobacter pittii and Bacillus velezensis to improve tomato plant growth, biochemical attributes and resistance against Rhizoctoniasolani

Green nanobiotechnology and beneficial bacterial strains as biofertilizers are crucial in agriculture to achieve food security. Both these strategies have been individually studied in improving plant resistance against phytopathogens along with enhancing plant productivity. Therefore, objective of this study was to explore the eco-friendly and cost-effective approach of utilizing plant growth promoting and disease suppressing bacterial strains and nanoparticles, individually as well as in combination, as bio-stimulants to improve plant growth, antioxidant defense system, nutrition and yield of tomato. A pot experiment was conducted to investigate the zinc sulfide nanoparticles (ZnS NPs) synthesized by using Jacaranda mimosifolia flower extracts (JFE), Acinetobacter pittii and Bacillus velezensis either individually or in combinations to check their potential against Rhizoctonia solani in tomato to suppress root rot infection and improve growth and yield. Among all the combinations the JFE-ZnS NPs + B. velezensis compared to untreated infected plants showed minimum disease incidence and maximum significant protection (66%) against R. solani instigated root rot that was followed by JFE-ZnS NPs + A. pittii and individual application of JFE-ZnS NPs by 58%. The same treatment showed maximum significant increase in plant fresh and dry biomass. B. velezensis significantly increased the photosynthetic pigments when applied individually. However, JFE-ZnS NPs alone and in mixed treatments with B. velezensis efficiently improved total soluble protein, sugar and phenolic contents. The same interactive application of JFE-ZnS NPs + B. velezensis improved the tomato plant nutrition (silicon (Si), magnesium (Mg), calcium (Ca) and potassium (K)) and redox quenching status by improving the activity of antioxidant defense enzymes. Overall, the interactive use of JFE-ZnS NPs with A. pittii and B. velezensis very appropriately prepared the host plant to fight against the negative effects of root rot pathogen in tomato. Advancements in interactively investigating the nanoparticles with beneficial plant growth promoting bacterial strains importantly can contribute in resolving the challenges of food security. According to our information, this is a pioneer report for implying JFE-ZnS NPs in synergism with A. pittii and B. velezensis to hinder the root rot in tomatoes.

“Biofilm Formationand Antibiotic Resistance Profiles of Water-borne Pathogens

Water sources (surface water, drinking water, rivers, and ponds) are significant reservoirs for transmitting antibiotic-resistant bacteria. In addition, these waters are an important public health problem because they are suitable environments for transferring antibiotic resistance genes between bacterial species. Our study aimed to assess the prevalence of Extended-spectrum beta-lactamase (ESBL) producing isolates in water samples, the susceptibility of the isolates to the specified antibiotics, the determination of biofilm ability, antibiotic resistance genes, and the molecular typing of the isolates. For this purpose, Polymerase chain reaction (PCR) and Matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) analyses were used. Out of 70 isolates, 15 (21%) were ESBL producing, and sent for the MALDI-TOF analysis, where Escherichia coli, Acinetobacter calcoaceticus, Enterobacter bugandensis, Acinetobacter pittii, Pseudomonas aeruginosa, Acinetobacter junii, Pseudomonas oleovorans, and Enterobacter ludwigigii were identified. Moreover, colistin resistance genes (mcr1/2/6, mcr 4, mcr 5, mcr 3/7, and mcr 8), ESBL-encoding genes(bla_SHV, bla_TEM, and bla_CTX-M) and carbapenemase genes (bla_NDM, bla_OXA-48, and bla_KPC) using molecular analysis (PCR) were confirmed. The colistin resistance gene was detected at 80% (12/15) in the isolates obtained. The distribution of these isolates according to resistance genes was found as mcr 1/2/6 4 (20%), mcr3/7 3 (13%), and mcr 5 (40%). Additionally, the isolates harbored bla_SHV(6.6%) and bla_TEM (6.6%) genes. However, bla_NDM, bla_OXA-48, bla_KPC, and bla_CTX-M genes were not detected in any isolates. According to the Congo red agar method, seven (46.6%) isolates showed negative biofilm ability, and eight (53.3%) showed moderate biofilm ability. However, the microplate method detected weak biofilm in 53.3% of the isolates.In conclusion, this study provides evidence for the existence of multidrug-resistant bacteria that co-exist with mcr and ESBL genes in water sources. These bacteria can migrate to other environments and pose increasing threats to public health.

Threats to UK freshwaters under climate change: Commonly traded aquatic ornamental species and their potential pathogens and parasites

The aquatic ornamental industry, whilst providing socio-economic benefits, is a known introduction pathway for non-native species, which if invasive, can cause direct impacts to native species and ecosystems and also drive disease emergence by extending the geographic range of associated parasites and pathogens and by facilitating host-switching, spillover and spill-back. Although current UK temperatures are typically below those necessary for the survival and establishment of commonly-traded tropical, and some sub-tropical, non-native ornamental species, the higher water temperatures predicted under climate-change scenarios are likely to increase the probability of survival and establishment. Our study aimed primarily to identify which of the commonly-traded non-native ornamental aquatic species (fish and invertebrates), and their pathogens and parasites, are likely to benefit in terms of survival and establishment in UK waters under predicted future climate conditions. Out of 233 ornamental species identified as traded in the UK, 24 were screened, via literature search, for potential parasites and pathogens (PPPs) due to their increased risk of survival and establishment under climate change. We found a total of 155 PPPs, the majority of which were platyhelminths, viruses and bacteria. While many of the identified PPPs were already known to occur in UK waters, PPPs currently absent from UK waters and with zoonotic potential were also identified. Results are discussed in the context of understanding potential impact, in addition to provision of evidence to inform risk assessment and mitigation approaches.

Expression profiles of cdca9 related to ovarian development in loach (Misgurnus anguillicaudatus)

The function of borealin proteins has been widely reported in the cell division of animals. Nonetheless, there is little research about their only known paralogue (cell division cycle associated 9, cdca9). In this study, cdca9 was investigated in loach (Misgurnus anguillicaudatus) for the first time. cdca9 was highly expressed in the embryo before the gastrula stage, and it was predominantly expressed in the ovary, especially in the oocytes of stage II. In conclusion, this study reveals a potential function of cdca9 in the early embryogenesis and ovarian development of fish.

Acinetobacter baumannii Infections in Times of COVID-19 Pandemic

The COVID-19 pandemic has generated an overuse of antimicrobials in critically ill patients. Acinetobacter baumannii frequently causes nosocomial infections, particularly in intensive care units (ICUs), where the incidence has increased over time. Since the WHO declared the COVID-19 pandemic on 12 March 2020, the disease has spread rapidly, and many of the patients infected with SARS-CoV-2 needed to be admitted to the ICU. Bacterial co-pathogens are commonly identified in viral respiratory infections and are important causes of morbidity and mortality. However, we cannot neglect the increased incidence of antimicrobial resistance, which may be attributed to the excess use of antimicrobial agents during the COVID-19 pandemic. Patients with COVID-19 could be vulnerable to other infections owing to multiple comorbidities with severe COVID-19, prolonged hospitalization, and SARS-CoV-2-associated immune dysfunction. These patients have acquired secondary bacterial infections or superinfections, mainly bacteremia and urinary tract infections. This review will summarize the prevalence of A. baumannii coinfection and secondary infection in patients with COVID-19.

Acinetobacter Strain KUO11TH, a Unique Organism Related to Acinetobacter pittii and Isolated from the Skin Mucus of Healthy Bighead Catfish and Its Efficacy Against Several Fish Pathogens

The bacterial strain KU011TH was isolated from the skin mucus of healthy bighead catfish. The strain is a Gram-negative coccobacillus that is nonmotile, aerobic, catalase positive, oxidase negative, and nonhemolytic. Sequence analyses of the housekeeping genes 16S rRNA, gyrB and rpoB indicate that this strain is a new member of the Acb complex of the genus Acinetobacter and is closely related to Acinetobacter pittii and Acinetobacter lactucae. In addition, the genome relatedness-associated ANIb (<95–96%) and in silico DDH (<70%) values clearly supported the new member of the genus Acinetobacter and the Acb complex. The genome of the strain KU011TH was approximately 3.79 Mbp in size, comprising 3619 predicted genes, and the DNA G+C content was 38.56 mol%. The major cellular fatty acids were C18:1ω9c, C16:0, C16:1, C20:2, C18:2ω6c and C18:1ω9t. The whole-genome sequences and phenotypic, phylogenetic, and chemotaxonomic data clearly support the classification of the strain KU011TH as a new member in the genus Acinetobacter which is closest to A. pittii. Additionally, the new bacterial strain exhibited strong activity against a broad range of freshwater fish pathogens in vitro.

Characterization of co-metabolic biodegradation of methyl tert-butyl ether by a Acinetobacter sp. strain

Co-metabolic bioremediation is a promising approach for the elimination of methyl tert-butyl ether (MTBE), which is a common pollutant found worldwide in ground water. In this paper, a bacterial strain able to co-metabolically degrade MTBE was isolated and named as Acinetobacter sp. SL3 based on 16S rRNA gene sequencing analysis. Strain SL3 could grow on n-alkanes (C₅–C₈) accompanied with the co-metabolic degradation of MTBE. The number of carbons present in the n-alkane substrate significantly influenced the degradation rate of MTBE and accumulation of tert-butyl alcohol (TBA), with n-octane resulting in a higher MTBE degradation rate (V_max = 36.7 nmol min⁻¹ mg_protein⁻¹, K_s = 6.4 mmol L⁻¹) and lower TBA accumulation rate. A degradation experiment in a fed-batch reactor revealed that the efficiency of MTBE degradation by Acinetobacter sp. strain SL3 did not show an obvious decrease after nine rounds of MTBE replenishment ranging from 0.1–0.5 mmol L⁻¹. The results of this paper reveal the preferable properties of Acinetobacter sp. SL3 for the bioremediation of MTBE via co-metabolism and leads towards the development of new MTBE elimination technologies.

Acinetobacter sp. SL3 could co-metabolically degrade MTBE when grown on n-alkanes. An extremely low TBA accumulation were achieved on n-octane. The fed-batch reactor degradation revealed continuous MTBE degradation capacity by Acinetobacter sp. SL3.