Isolation, Purification, Characterization and Direct Conjugation of the Lipid†A-Free Lipopolysaccharide of Vibrio cholerae O139.

The lipopolysaccharide (LPS) of Vibrio cholerae O139, strain CIRS245, was isolated conventionally, and the lipid A was removed by mild acid hydrolysis (0.1 m NaOAc buffer containing 1 % SDS, pH 4.2, 95 °C, 8 h). The crude product was a complex mixture consisting mainly of constituent fragments of the O-specific polysaccharide-core (OSPc). The OSPc was only a minor component in the mixture. Two-stage purification of the crude OSPc by HPLC gave pure OSPc fragment of the LPS, as shown by NMR spectroscopy, analytical HPLC and ESI-MS. This material is the purest OSPc fragment of the LPS from Vibrio cholerae O139 reported to date. The purified OSPc was readily converted to the corresponding methyl squarate derivative and the latter was conjugated to BSA. The conjugate, when examined by ELISA, showed immunoreactivity with sera from patients in Bangladesh recovering from cholera caused by V. cholerae O139, but not O1.

Anti-staphylococcal activity of quaternized mannan from the yeast Candida albicans.

Global increase of antibiotic-resistant pathogens as well as elevated content of drug residues in the foodstuffs and the environment urgently calls for new biocompatible antimicrobial biomaterials. Yeast mannans represent readily available source of biodegradable materials for tailor-made derivatives that could be effective in biomedical applications. Here, antimicrobial properties of quaternized mannans (DSQ 0.12, 0.24, 0.30, 0.62) from Candida albicans against clinical multi-resistant strains of Staphylococcus aureus are confronted with possible cytotoxicity against human cells. As expected, both effects increase with increasing degree of quaternization. However, it is possible to define the "window", at quaternized mannan with DSQ 0.30 with good anti-microbial effectiveness and low cytotoxicity. This derivative exhibit minimum inhibitory (MIC) and minimum bactericidal (MBC) concentration from 62.5 to 250 µg/mL and demonstrate good biofilm inhibition effect. Also acceptable values were obtained in hemagglutination and hemolytic activity assays and also in cytotoxicity tests on human fibroblasts.

Potential pathogenicity and antibiotic resistance of aquatic Vibrio isolates from freshwater in Slovakia.

This study aimed to evaluate the potential pathogenicity and antibiotic resistance of 31 environmental Vibrio isolates obtained from surface water in southern and eastern Slovakia. Isolates were identified as Vibrio cholerae non-O1/non-O139 and Vibrio metschnikovii by biochemical tests, MALDI biotyping, and 16S RNA gene sequencing. Analysis of the susceptibility to 13 antibacterial agents showed susceptibility of all isolates to ciprofloxacin, trimethoprim/sulfamethoxazole, chloramphenicol, gentamicin, imipenem, tetracyclin, and doxycycline. We recorded high rates of resistance to ß-lactams and streptomycin. Investigation of antibiotic resistance showed five different antibiotic profiles with resistance to antibacterials from three classes, but no multidrug resistance was observed. The investigation of the pathogenic potential of V. cholerae isolates showed that neither the cholera toxin coding gene ctxA nor the genes zot (zonula occludens toxin), ace (accessory cholera toxin), and tcpA (toxin-coregulated pilus) were present in any of 31 isolated samples. Gene ompU (outer membrane protein) was confirmed in 80% and central regulatory protein-coding gene toxR in 71% of V. cholerae isolates, respectively. A high prevalence of the hemolysin coding gene hlyA in all V. cholerae was observed. The data point toward the importance of systematic monitoring and comparative studies of potentially pathogenic vibrios in European countries.

Survival of rat cerebrocortical neurons after rickettsial infection.

Neuroinvasive microorganisms are suspected to play an important role in the etiopathogenesis of neurological diseases. However, direct evidence for the pathogenic function is still missing. The main aim of this study was to investigate biochemical and morphological changes that may occur as a result of an in vitro infection of rat cerebrocortical neurons by selected members of the genus Rickettsia. Our results showed that survival of the neurons is significantly reduced after the infection. Intracellular level of ATP is gradually decreased and inversely correlates with the load of rickettsiae. Immunofluorescence revealed that rickettsiae can enter the neurons and are localized in perinuclear space and also in neuronal processes. Data obtained in this study correspond to the idea of possible involvement of rickettsiae in the etiopathogenesis of various neuropathies.

Multiresistance of Staphylococcus xylosus and Staphylococcus equorum from Slovak Bryndza cheese.

Staphylococcus xylosus, Staphylococcus equorum, and Staphylococcus epidermidis strains were isolated from Bryndza cheese and identified using PCR method. The antimicrobial susceptibility of these strains was assessed using disc diffusion method and broth microdilution method. The highest percentage of resistance was detected for ampicillin and oxacillin, and in contrary, isolates were susceptible or intermediate resistant to ciprofloxacin and chloramphenicol. Fourteen of the S. xylosus isolates (45%) and eleven of the S. equorum isolates (41%) exhibited multidrug resistance. None of the S. epidermidis isolate was multiresistant. The phenotypic resistance to oxacillin was verified by PCR amplification of the gene mecA.