Interferon expression in feline Borna disease

Borna disease is caused by Borna disease virus (BDV). This disease is characterised as a neurogical illness of the central nervous system (CNS), known to occur in several vertebrates like horses, cats and sheep. Cats mainly at the age of 1 to 4 years, living outdoors, have also been shown to subtract the BDV infection. A typical sign in cats of BDV infection is a change in behaviour, i.e. some cats get increased affection and meow more than usually. In addition, a lot of cats get ataxic and their balance is adversely affected. The route of infection is still not fully known. One theory is that the virus spreads and infects through saliva and the respiratory tract, respectively. Some studies have shown that the infection is not commonly transmitted between cats. Thus, it seems more likely that another species, such as rodents or birds, are the carrier of the disease. This hypothesis seems more likely since the cats that have been diagnosed as carriers of BDV have been living outdoors. There are no sufficient diagnostic methods for BDV. Therefore necropsy and histopathologic examination of the brain tissue is the method for diagnosis and confirmation of BDV infection. The aim of this study was to investigate whether the gene expression, measured by quantitative RT-PCR, of IFN-α , -β and -γ in the brain tissues of Borna disease diagnosed cats is induced. To normalize the IFN gene expression, the reference genes, HPRT, RPS7 and YWHAZ, were used. In addition, PCR-products were confirmed by gel electrophoresis. With the use of different PCR measurements for the expression of reference genes it was studied whether Borna disease was associated with gene expression of cytokines in the brain. When comparing the Ct-values of IFN- with the histopathological finding it was clearly evident that Borna disease diagnosed cats had a much higher gene expression than the other cats. However, a majority of non virus diagnosed cats showed higher Ct-values or no Ct-values at all. Consequently, results showed clear association between Borna disease diagnosis and increased IFN-γ gene expression.Vingelsjuka hos katt orsakas av bornavirus (BDV), som även orsakar neurologisk sjukdom hos bl.a. får och häst. Vad man vet så drabbas främst utomhuskatter, i åldern 1 till 4 år, av bornavirus. Vanliga symtom som förekommer hos katter med bornavirusinfektion är förändringar i beteendet. Vissa katter blir mer sociala och jamar mer än vanligt, ibland förekommer det även att de blir aggressiva. Ett annat typiskt symtom är förlamning i bakbenen och att de tappar balansen. Idag vet man inte säkert hur viruset sprider sig. En teori är att viruset sprider sig och infekterar genom saliv och luftvägarna. Studier har visat att viruset vanligtvis inte smittar katter emellan. Det verkar mer troligt att smittobäraren är av en annan art som t.ex. gnagare eller fåglar. Dessa hypoteser verkar mer troliga eftersom de katter som blivit diagnostiserade med bornavirus vistats utomhus. Idag finns det inte tillräckligt bra diagnostiska tester för BDV. Därför används obduktion och histopatologiska undersökningar av hjärnvävnaden för att diagnostisera och fastställa om det är en bornavirusinfektion. Syftet med denna studie var att undersöka genuttrycket av IFN-α, -β och -γ i hjärnvävnaden hos vingelsjuka katter. För att normalisera variationen i genuttrycket användes referensgenerna HPRT, RPS7 och YWHAZ. Gelelektrofores användes sedan för att påvisa PCR-produkter. Genom att använda sig av olika PCR-mätningar för uttrycket av referensgenerna så studerades det om vingelsjuka associerade med genuttrycket av cytokiner i hjärnan. När Ct-värdena från IFN-γ och de histopatologiska undersökningarna jämfördes kunde man konstatera att de katter som diagnostiserats med vingelsjuka hade ett mycket högre genuttryck än de andra katterna. Hursomhelst, majoriteten av icke-diagnostiserade vingelsjuka katter visade högre eller inga Ct-värden överhuvudtaget. Resultaten visade klara samband mellan vingelsjuka katter och ökat IFN-γ uttryck

De novo resistance mutations at sub-MIC levels

Antibiotic resistance is a kind of achievable drug resistance meaning that microorganisms are able to sustain and survive exposure to antibiotics. A major contribution to development of antibiotic resistance is the abuse of antibiotics in human and in veterinary medicine. Antibiotics have been used for many decades but only during recent years studies have been published that have increased the understanding in the area of antibiotic input and consequences thereof on bacterial resistance. Thus, it was just recently published that bacterial strains can undergo rapid selection of resistant mutants at antibiotic concentrations far below MIC (Minimal Inhibitory Concentration). However, presently there are no studies at low antibiotic concentrations that have been able to show whether growth and development of de novo resistant mutants competitively can out grow the normal bacterial population. Therefore, the aim of this project was to investigate whether de novo resistant mutants of Salmonella typhimurium and Escherichia coli can appear and take over the normal bacterial population, and if this occurs also to isolate the resistant mutations for characterization. These are closely related bacteria but they differ in their target sites for antibiotic resistance i.e. S. typhimurium carries a cryptic aminoglycoside resistance gene, aadA, that can be up-regulated and thereby causing streptomycin resistance, while the most common low-cost mutations conferring resistance to ciprofloxacin in E. coli are in the gyrase gene gyrA. The results showed that concentrations of antibiotics far below MIC can select for de novo mutants with high antibiotic resistance both in S. typhimurium and E. coli. The novel findings regarding these resistant mutants are that they are likely to have lower fitness cost than previously studied resistance mutations (such as rpsL mutants for streptomycin) which means that these mutations may be new and different from those previously described

Selection of Resistant Bacteria at Very Low Antibiotic Concentrations

The widespread use of antibiotics is selecting for a variety of resistance mechanisms that seriously challenge our ability to treat bacterial infections. Resistant bacteria can be selected at the high concentrations of antibiotics used therapeutically, but what role the much lower antibiotic concentrations present in many environments plays in selection remains largely unclear. Here we show using highly sensitive competition experiments that selection of resistant bacteria occurs at extremely low antibiotic concentrations. Thus, for three clinically important antibiotics, drug concentrations up to several hundred-fold below the minimal inhibitory concentration of susceptible bacteria could enrich for resistant bacteria, even when present at a very low initial fraction. We also show that de novo mutants can be selected at sub-MIC concentrations of antibiotics, and we provide a mathematical model predicting how rapidly such mutants would take over in a susceptible population. These results add another dimension to the evolution of resistance and suggest that the low antibiotic concentrations found in many natural environments are important for enrichment and maintenance of resistance in bacterial populations