Terhi Ali-Vehmas

Characterization of Sphingomonas isolates from Finnish and Swedish drinking water distribution systems

Sphingomonas species were commonly isolated from biofilms in drinking water distribution systems in Finland (three water meters) and Sweden (five water taps in different buildings). The Sphingomonas isolates (n = 38) were characterized by chemotaxonomic, physiological and phylogenetic methods. Fifteen isolates were designated to species Sphingomonas aromaticivorans, seven isolates to S. subterranea, two isolates to S. xenophaga and one isolate to S. stygia. Thirteen isolates represented one or more new species of Sphingomonas. Thirty‐three isolates out of 38 grew at 5 °C on trypticase soy broth agar (TSBA) and may therefore proliferate in the Nordic drinking water pipeline where the temperature typically ranges from 2 to 12 °C. Thirty‐three isolates out of 38 grew at 37 °C on TSBA and 15 isolates also grew on blood agar at 37 °C. Considering the potentially pathogenic features of sphingomonas, their presence in drinking water distribution systems may not be desirable.

RETRACTED: Antioxidant nutrients and mycotoxins

This article has been retracted at the request of the editor. Reason: This article contained extensive text that originally appeared in the Journal of Food Protection (FABIO GALVANO, ANDREA PIVA, ALBERTO RITIENI, and GIACOMO GALVANO published by the International Association for Food Protection. Dietary Strategies to Counteract the Effects of Mycotoxins: A Review. J. Food Prot. (2001) Vol. 64 (1): 120–131). Toxicology publishes only original work, and on the occasion when brief excerpts or quotes from other sources are used, this must be clearly indicated with full acknowledgement and written permission from the copyright holder.

Comparison of variable-number tandem-repeat markers typing and IS1245 restriction fragment length polymorphism fingerprinting of Mycobacterium avium subsp. hominissuis from human and porcine origins.

BackgroundAnimal mycobacterioses are regarded as a potential zoonotic risk and cause economical losses world wide. M. avium subsp. hominissuis is a slow-growing subspecies found in mycobacterial infected humans and pigs and therefore rapid and discriminatory typing methods are needed for epidemiological studies. The genetic similarity of M. avium subsp. hominissuis from human and porcine origins using two different typing methods have not been studied earlier. The objective of this study was to compare the IS1245 RFLP pattern and MIRU-VNTR typing to study the genetic relatedness of M. avium strains isolated from slaughter pigs and humans in Finland with regard to public health aspects.MethodsA novel PCR-based genotyping method, variable number tandem repeat (VNTR) typing of eight mycobacterial interspersed repetitive units (MIRUs), was evaluated for its ability to characterize Finnish Mycobacterium avium subsp. hominissuis strains isolated from pigs (n = 16) and humans (n = 13) and the results were compared with those obtained by the conventional IS1245 RFLP method.ResultsThe MIRU-VNTR results showed a discriminatory index (DI) of 0,92 and the IS1245 RFLP resulted in DI 0,98. The combined DI for both methods was 0,98. The MIRU-VNTR test has the advantages of being simple, reproducible, non-subjective, which makes it suitable for large-scale screening of M. avium strains.ConclusionsBoth typing methods demonstrated a high degree of similarity between the strains of human and porcine origin. The parallel application of the methods adds epidemiological value to the comparison of the strains and their origins. The present approach and results support the hypothesis that there is a common source of M. avium subsp. hominissuis infection for pigs and humans or alternatively one species may be the infective source to the other.

Binding of Staphylococcus aureus to milk fat globules increases resistance to penicillin-G

The susceptibility to penicillin-G of Staphylococcus aureus strains that cause mastitis was tested in milk and in Iso-sensitest broth (ISB): The minimal inhibitory concentrations (MIC) of beta-lactamase-positive strains in milk were 10-100-fold those in ISB, whereas the MIC of beta-lactamase-negative strains in milk were some 10-fold those in ISB; beta-lactamase production was induced by milk in beta-lactamase-positive strains. Much of the increase in resistance to penicillin-G caused by milk can be attributed to milk fat globules; the increase in resistance was related to the binding capacity of the bacteria to milk fat globules as well as to capsule formation by the bacteria. It appears that the binding of the staphylococci to the fat globules and bacterial capsule formation resulted in a biofilm type of growth. In this case, the staphylococci behaved differently from the planktonic type of growth in artificial broth medium in which antibiotic susceptibility testing is usually carried out.

Quantification of Mycobacterium avium subspecies in pig tissues by real-time quantitative PCR

BackgroundMycobacterioses in animals cause economical losses and certain Mycobacterium avium subspecies are regarded as potential zoonotic agents. The evaluation of the zoonotic risk caused by M. avium subspecies requires information about the quantities of Mycobacterium strains in infected animals. Because M. avium subspecies in pig tissues are difficult or even impossible to quantify by culturing, we tested the suitability of a culture-independent real-time quantitative PCR (qPCR) assay for this purpose.MethodsMycobacterial DNA was extracted from porcine tissues by a novel method and quantified by Mycobacterium genus specific qPCR assay targeting the 16S rRNA gene.ResultsThe response of the qPCR assay to the amount of M. avium subspecies avium mixed with porcine liver was linear in the range of approximately log105 to log107Mycobacterium cells per 1 g of liver. The assay was validated with three other M. avium subspecies strains. When the assay was applied to porcine lymph nodes with or without visible lesions related to Mycobacterium avium subspecies infections, around 104–107 mycobacterial genomes per gram of lymph nodes were detected.ConclusionsThe qPCR assay was found to be suitable for the quantification of Mycobacterium avium subspecies in porcine lymph nodes and liver.

Characterization of hemolytic activity of Staphylococcus aureus strains isolated from bovine mastitic milk

Beta (beta) and delta (delta)-hemolysin of Staphylococcus aureus strains were cultured in vitro in milk lactoserum (whey) prepared from both healthy and mastitis bovine milk. Production of beta- and delta-hemolysins were detected in 12 out of 50 strains studied. The association between N-acetyl-beta-D-glucosaminidase (NAGase) activity, plasmin activity (PL) and trypsin inhibitory capacity (TIC), known as inflammatory indicators for mastitis, and hemolytic activity were also studied. Mastitic milk decreased directly the lytic effect of both beta-and delta-hemolysins of S. aureus on hemolytical blood agar plates. S. aureus in healthy milk samples produced more beta-hemolysin (3 times) and delta-hemolysin (2 times) when compared to S. aureus supernatants in milk from infected quarters. Furthermore, beta- and delta-hemolysis correlated negatively with TIC and NAGase and PL activities. Addition of reduced glutathione (GSH) or beta-mercaptoethanol into the artificial medium enhanced hemolysins activity.