Identification of new amoebae strains in rainbow trout (Oncorhynchus mykiss, Walbaum) farms affected by nodular gill disease (NGD) in Northeastern Italy

Nodular gill disease (NGD) is an emerging condition associated with amoeba trophozoites in freshwater salmonid farms. However, unambiguous identification of the pathogens still must be achieved. This study aimed to identify the amoeba species involved in periodic NGD outbreaks in two rainbow trout (Oncorhynchus mykiss) farms in Northeastern Italy. During four episodes (February-April 2023), 88 fish were euthanized, and their gills were evaluated by macroscopic, microscopic and histopathological examination. The macroscopic and microscopic severity of the lesions and the degree of amoebae infestation were scored and statistically evaluated. One gill arch from each animal was put on non-nutrient agar (NNA) Petri dishes for amoeba isolation, cultivation and subsequent identification with SSU rDNA sequencing. Histopathology confirmed moderate to severe lesions consistent with NGD and mild to moderate amoeba infestation. The presence of amoebae was significantly correlated with lesion severity. Light microscopy of cultured amoebae strains and SSU rDNA analysis revealed the presence of a previously characterized amoeba Naegleria sp. strain GERK and several new strains: two strains from Hartmannelidae, three vannelid amoebae from the genus Ripella and cercozoan amoeba Rosculus. Despite the uncertainty in NGD etiopathogenesis and amoebae pathogenic role, identifying known and new amoebae leans towards a possible multi-aetiological origin.

Microplastics in Fish and Fishery Products and Risks for Human Health: A Review

In recent years, plastic waste has become a universally significant environmental problem. Ingestion of food and water contaminated with microplastics is the main route of human exposure. Fishery products are an important source of microplastics in the human diet. Once ingested, microplastics reach the gastrointestinal tract and can be absorbed causing oxidative stress, cytotoxicity, and translocation to other tissues. Furthermore, microplastics can release chemical substances (organic and inorganic) present in their matrix or previously absorbed from the environment and act as carriers of microorganisms. Additives present in microplastics such as polybrominated diphenyl ethers (PBDE), bisphenol A (BPA), nonylphenol (NP), octylphenol (OP), and potentially toxic elements can be harmful for humans. However, to date, the data we have are not sufficient to perform a reliable assessment of the risks to human health. Further studies on the toxicokinetics and toxicity of microplastics in humans are needed.

Comparative susceptibilities of Klebsiella species, Enterobacter species, and Pseudomonas aeruginosa to 11 antimicrobial agents in a tertiary-care university hospital

The in vitro activity of cefepime was compared versus that of 10 antimicrobial agents commonly used in the treatment of serious infections caused by common aerobic gram-negative bacteria: aztreonam, cefoperazone, ceftazidime, ceftriaxone, ciprofloxacin, gentamicin, imipenem, piperacillin, ticarcillin-clavulanic acid, and tobramycin. We tested 30 clinical isolates representing a cross section of Klebsiella and Enterobacter species and Pseudomonas aeruginosa collected at our tertiary-care university hospital. The most potent beta-lactams were imipenem and cefepime, which demonstrated significant activity against the majority of strains in all 3 genera of bacteria tested, as did ciprofloxacin and tobramycin. Ceftazidime was active against Pseudomonas aeruginosa but was less potent against Klebsiella and Enterobacter spp. Cefoperazone and ceftriaxone were less active than ceftazidime against Pseudomonas aeruginosa. Cefepime was found to be highly active against many resistant organisms that traditionally have been difficult to treat.

Investigation of a pseudo-outbreak of orthopedic infections caused by Pseudomonas aeruginosa

OBJECTIVE

To report a pseudoepidemic of Pseudomonas aeruginosa infections discovered during an investigation of postoperative joint infections.

DESIGN

A retrospective review of case patients' hospital charts, operative reports, and laboratory data, as well as environmental culturing, polymerase chain reaction (PCR) ribotyping of outbreak isolates, and in vitro analysis of P aeruginosa growth characteristics.

SETTING

A 510-bed, university-affiliated adult tertiary care hospital.

RESULTS

Between October 1 and December 1, 1992, seven postsurgical joint infections were diagnosed, including four caused by P aeruginosa. A bottle of "sterile" saline used to process tissue specimens was found to be contaminated with P aeruginosa. Further investigation revealed that P aeruginosa had grown from seven additional tissue cultures, all of which had been processed with the contaminated saline. PCR ribotypes of the contaminant matched those of the clinical isolates. In vitro, P aeruginosa strains were viable in commercial nonbacteriostatic saline, but never caused visible turbidity. Six patients received antibiotics for their presumed infections; four patients had peripherally inserted central catheters placed, and one experienced severe anaphylactic reactions to several antibiotics.

CONCLUSIONS

Pseudoepidemics due to common organisms are often difficult to detect, and delayed recognition can result in substantial morbidity. This outbreak investigation illustrates the potential for contamination of diluents in the microbiology laboratory and emphasizes the need for meticulous quality control.

A comparison of serial plate agar dilution, Bauer-Kirby disk diffusion, and the Vitek AutoMicrobic system for the determination of susceptibilities of Klebsiella spp., Enterobacter spp., and Pseudomonas aeruginosa to ten antimicrobial agents

The use of rapid, automated technologies for assessment of antimicrobial susceptibility and determination of minimum inhibitory concentrations has been evolving for over a decade. We compared the Vitek AutoMicrobic system and Bauer-Kirby disk diffusion with the National Committee for Clinical Laboratory Standards methods of serial plate agar dilution for qualitative and quantitative susceptibilities of 301 hospital isolates of Klebsiella spp., Enterobacter spp., and Pseudomonas aeruginosa. Antibiotics tested were aztreonam, cefoperazone, ceftazidime, ceftriaxone, ciprofloxacin, gentamicin, imipenem, piperacillin, ticarcillin-clavulanic acid, and tobramycin. Agar dilution and Bauer-Kirby results were more strongly correlated for all three genera than were the results for agar dilution and Vitek. If agar dilution is presumed to be the "gold standard," Bauer-Kirby disk diffusion had only half the number of false susceptibles as did the Vitek. Thus, the Vitek AutoMicrobic system seems to be somewhat less reliable for both qualitative and quantitative measurement of susceptibility and resistance than is Bauer-Kirby disk diffusion.