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Lactococcosis caused by Lactococcus garvieae is a bacterial infection affecting fish with a considerable economic impact. Recently, L. garvieae has established itself as an opportunistic pathogen in humans. The aim of the current study was to test classical and molecular-biological methods for the identification of L. garvieae and examine antimicrobial susceptibility and capsule production, an important virulence factor. Additionally, tests for differentiation from closely related species, as well as epidemiological typing, were performed. In a period of 18 years (2002–2019), 24 isolates presumptively identified as L. garvieae were collected from Oncorhynchus mykiss and Salmo salar fish obtained either from retail stores or fish farms. In order to confirm the species, optimized PCR-based protocols were used. As a result, 21 of the tested strains were proved to be L. garvieae (n = 21). The remaining three isolates were Lactococcus lactis, Streptococcus iniae, and Enterococcus faecalis. Epidemiological typing by randomly amplified polymorphic DNA was performed. Except for a single KG+ isolate, all other strains belonged to the European capsular serotype KG−. All L. garvieae isolates showed susceptibility to all tested antibiotics with the exception of clindamycin, which was a diagnostic sign. A thorough optimization of diagnostic methods is essential to determining the etiology of specific infections affecting the personnel at risk in fish farms, the food industry, or within the broader community. [ABSTRACT FROM AUTHOR]

Antimicrobial photodynamic therapy (aPDT) has been considered as a promising method to keep under control the multidrug resistance of pathogenic bacteria. As is well-known the PDT procedure involves a photosensitizer and application of proper light spectrum for its activation in the presence of oxygen atmosphere. In general, the produced oxygen species are toxic to the biomolecules which features mainly two mechanisms, which are appropriate to irreversible inactivation of the drug-resistant microbial pathogens. The present study evaluates two pairs of Gram-negative bacteria such as Flavobacterium hydatis (F. hydatis) and Aeromonas hydrophila (A. hydrophila) as multidrug resistant (R) and sensitive (S) strains isolated from natural sources. Two recently synthesized palladium phthalocyanine complexes (PdPcs) with substituents of four methylpyridiloxy groups on peripheral (pPdPc) and non-peripheral (nPdPc) positions were used as photosensitizers. In addition, tetra-methylpyridiloxy substituted Zn(II)-phthalocyanine (ZnPcMe) was tested as a reference photosensitizer taking into accound its high photodynamic inactivation ability towards different pathogenic microorganisms [1]. The results showed full photodynamic inactivation with 5.0 µM nPdPc towards both strains F. hydatis , R and S (6log), but a half of the inactivation value (3log) was obtained with 5.0 µM pPdPc and only for F. hydatis , S. For comparison reason, a well-known zinc phthalocyanine (ZnPcMe) was studied with high efficacy towards both F. hydatis R and S strains. The results on the second pair strains showed complete inactivation with nPdPc (0.4 µM for the both S and R strains) as compared to pPdPc (8 µM for S strain). Comparison between the both new isolates Aeromonas hydrophila (S and R) strains, suggests that PDT efficacy with the applied phthalocyanines is independent on the drug sensitivity of the tested strains [2]. This study suggested the promising base for the development of aPDT as alternative method to keep under control the farm fishes' pathogens. [ABSTRACT FROM AUTHOR]

Antibacterial photodynamic therapy is a pioneering method for the inactivation of pathogenic bacteria. Four tetra alkyl-substituted cationic phthalocyanines with different hydrocarbon chains attached to the pyridyloxy group were synthesized. These photodynamic sensitizers were studied for antibacterial inactivation of a multidrug-resistant strain of Gram-negative bacterium Aeromonas hydrophila. Aeromonas species are recognized as etiological agents of a wide spectrum of diseases in humans and animals. The uptake of phthalocyanines by the bacterial cells decreased with an increase in cell density. Following the phthalocyanine solubility from hydrophilic to hydrophobic complexes, the accumulation capacity increased. Full inactivation was achieved with phthalocyanine with (methoxy) pyridyloxy substitution following a short exposure time, low drug concentration and mild irradiation. Although the phthalocyanine with the longest hydrocarbon chain (C12) has some toxic effect in the absence of light, substantial phototoxic effect was obtained with the optimal combination of drug-irradiation parameters. [ABSTRACT FROM AUTHOR]

A pair of Yersinia enterocolitica serotype O∶3 strains — incubated in growth medium with 10% NaCl and 2 mM glycin betaine at 4 °C, were used to study the plasmid role in the infection of BALB/c mice. The isogenic plasmid-bearing strain, but not its plasmidless derivative, caused enteric infection and histological changes in intestines, stomach and liver of the mice. Two strains Y. enterocolitica and Yersinia pseudotuberculosis were incubated at different temperatures (4 and 25 °C) in media, supplemented with different concentrations of NaCl. Two concentrations of betaine as osmoprotector were tested. The initial strains and their substrains were characterised by protein profiles using sodium dodecyl sulphate-polyacrylamide gel electrophoresis. Results show that in salinity conditions, the presence of osmoprotectant (betaine) as well as the temperature of cultivation plays a great role in the expression of some bacterial proteins. The manner in which the different strains answer to the stress situations is specific for each of them. [ABSTRACT FROM AUTHOR]