Reduction of prevalence of persistent BVDV infection in cattle herds by long-term vaccination program (preliminary clinical study).

Effectiveness of long-term anti-BVDV vaccination program in reducing prevalence of persistent BVDV infection in cattle herds was evaluated in seven years observational study (2005-2011). Among three seropositive dairy cattle herds (within herd seroprevalence 100%, confirmed by ELISA Herd Check BVDV Ab, IDEXX, Sweden) vaccination program based on inactivated vaccine (cytopathic strain 5960) was commenced in 2007 in two herds and continued till 2010. In the years 2007-2011 all calves aged 2-12 weeks in all three herds were tested yearly with RT-PCR in order to detect persistently infected individuals. For the entire study period true prevalence of BVDV persistent infection was significantly lower in vaccinated than in non-vaccinated herd. This may imply the role of long-term vaccination program in reducing prevalence of persistent BVDV infection in cattle herds.

Resistance patterns and occurrence of virulence determinants among GRE strains in southwestern Poland.

PURPOSE: The aim of this study was to determine the antimicrobial resistance and the occurrence of virulence determinants among glycopeptide-resistant enterococci (GRE) isolated in 2007-2009 from patients hospitalized in southwestern Poland. MATERIAL AND METHODS: The minimal inhibitory concentrations (MICs) of antibiotics were determined by agar dilution method or by E-test®. The presence of vanA - vanG resistance and virulence genes (agg, esp, gelE and cylA, cylB, cylM) was investigated using PCR. The ability to form biofilm and the activity of gelatinase, hemolysins, lipase and DNase were tested. RESULTS: All the GRE strains were susceptible to linezolid, daptomycin, and tigecycline and resistant to norfloxacin. In the Enterococcus faecium group, 17 strains carried the vanA gene and 20 the vanB gene. In the Enterococcu faecalis group, 4 strains carried the vanA gene and 1 the vanB gene. There were differences in tetracycline susceptibility between the VanA (70%) and the VanB (55%) phenotypes. Only linezolid had high activity against both the VanA and the VanB phenotypes. The esp gene was present in most of the GRE strains, but only 3 E. faecalis strains produced biofilm. Lipase was produced by 10/42 examined strains, gelatinase by 4/42 and hemolysin by 3/42 isolates. CONCLUSIONS: Linezolid seems to be the optimal option in empirical therapy of infections caused by GRE strains because of the relationship between its activity (MIC value) and susceptibility breakpoint. There was no correlation between the prevalence of different virulence genes and resistance to the antibiotics tested.

Genotypic characterization of hospital Enterococcus faecalis strains using multiple-locus variable-number tandem-repeat analysis.

AIMS: The level of genetic diversity and relationships between the specific genotypes and the distribution of virulence determinants among Enterococcus faecalis strains isolated from patients hospitalized in different wards of two hospitals were investigated. METHODS AND RESULTS: Fifty-six clinical strains of E. faecalis, isolated from patients hospitalized in the period of 1999-2004 in several wards in Wroclaw (Poland), were analysed by multiple-locus variable-number tandem-repeat analysis (MLVA). Analysis of seven genomic loci identified 40 novel genotypes among the analysed E. faecalis strains, with two major genomic groups, designated I and II, distinguished at a cut-off of 35%. With a similarity cut-off of 85.7%, the genotypes could be combined into 12 clusters (C1-C12), containing at least two isolates. The remaining 18 MLVA types were represented by a single isolate. CONCLUSIONS: Based on the data obtained by MLVA, it was found that (i) many E. faecalis isolates recovered from patients from the wards whose location allowed the potential transmission of micro-organisms, belonged to closely related MLVA types and (ii) possible relationships between specific E. faecalis genotype and the virulence factors lipase, haemolysin and esp gene can exist. SIGNIFICANCE AND IMPACT OF THE STUDY: Our study confirms that MLVA is a suitable method for the epidemiological study of E. faecalis and for the first time shows possible relationships between specific genotypes and such virulence determinants, i.e. lipase, haemolysin and esp gene.

The impact of environmental stress on Listeria monocytogenes virulence.

Listeria monocytogenes, a significant food-borne pathogen, must defy a variety of conditions encountered in the food environment and during the infection process. In reaction to adverse conditions, the bacteria significantly change their metabolism, inducing a stress response which is mediated by a range of alternative sigma factors. The extent of the response to stress was shown to vary in the L. monocytogenes population. According to recent evidence a major L. monocytogenes alternative sigma factor, designated sigma B (sigma B), regulates some virulence genes in response to stress, which supports an older hypothesis that stress-resistant strains should be more pathogenic. The induction of sigma B-dependent genes may also be important from the point of view of food hygiene. It seems that stress response activation can paradoxically enhance resistance to agents used in food preservation. Therefore, monitoring the expression of sigma B-dependent genes can serve as a useful marker to assess the innate resistance of L. monocytogenes strains. This knowledge will allow the design of new methods with sequential preservation steps that could inactivate the bacteria without inducing their stress response.