Rifampicin and sodium fusidate reduces the frequency of methicillin-resistant Staphylococcus aureus (MRSA) isolation in adults with cystic fibrosis and chronic MRSA infection

Nosocomial transmission of methicillin-resistant Staphylococcus aureus (MRSA) to patients with cystic fibrosis (CF) frequently results in chronic respiratory tract carriage. This is an increasing problem, adds to the burden of glycopeptide antibiotic use in hospitals, and represents a relative contraindication to lung transplantation. The aim of this study was to determine whether it is possible to eradicate MRSA with prolonged oral combination antibiotics, and whether this treatment is associated with improved clinical status. Adult CF patients (six mate, one female) with chronic MRSA infection were treated for six months with rifampicin and sodium fusidate. Outcome data were examined for six months before treatment, on treatment and after treatment. The patients had a mean age of 29.3 (standard deviation = 6.3) years and FEV1 of 36.1% (standard deviation = 12.7) predicted. The mean duration of MRSA isolation was 31 months. MRSA isolates identified in these patients was of the same lineage as the known endemic strain at the hospital when assessed by pulsed-field get electrophoresis. Five of the seven had no evidence of MRSA during and for at [east six months after rifampicin and sodium fusidate. The proportion of sputum samples positive for MRSA was lower during the six months of treatment (0.13) and after treatment (0.19) compared with before treatment (0.85) (P < 0.0001). There was a reduction in the number of days of intravenous antibiotics per six months with 20.3 +/- 17.6 on treatment compared with 50.7 before treatment and 33.0 after treatment (P = 0.02). There was no change in lung function. Gastrointestinal side effects occurred in three, but led to therapy cessation in only one patient. Despite the use of antibiotics with anti-staphylococcal activity for treatment of respiratory exacerbation, MRSA infection persists. MRSA can be eradicated from the sputum of patients with CF and chronic MRSA carriage by using rifampicin and sodium fusidate for six months. This finding was associated with a significant reduction in the duration of intravenous antibiotic treatment during therapy. (C) 2003 The Hospital Infection Society. Published by Elsevier Ltd. All rights reserved.

S100A8 chemotactic protein is abundantly increased, but only a minor contributor to LPS-induced, steroid resistant neutrophilic lung inflammation in vivo

Neutrophilic lung inflammation is an essential component of host defense against diverse eukaryotic and prokaryotic pathogens, but in chronic inflammatory lung diseases, such as chronic obstructive lung disease (COPD), severe asthma, cystic fibrosis, and bronchiolitis, it may damage the host. Glucocorticosteroids are widely used in these conditions and in their infectious exacerbations; however, the clinical efficacy of steroids is disputed. In this study, we used a proteomic approach to identify molecules contributing to neutrophilic inflammation induced by transnasal administration of lipopolysaccharide (LPS) that were also resistant to the potent glucocorticosteroid dexamethasone (Dex). We confirmed that Dex was biologically active at both the transcript (suppression of GM-CSF and TNFalpha transcripts) and protein levels (induction of lipocortin) and used 2D-PAGE/MALDI-TOF to generate global expression profiles, identifying six LPS-induced proteins that were Dex resistant. Of these, S100A8, a candidate neutrophil chemotactic factor, was profiled in detail. Steroid refractory S100A8 expression was highly abundant, transcriptionally regulated, secreted into lung lavage fluid and immunohistochemically localized to tissue infiltrating neutrophils. However, in marked contrast to other vascular beds, neutralizing antibodies to S100A8 had only a weak anti-neutrophil recruitment effect and antibodies against the related S100A9 were ineffective. These data highlight the need for extensive in vivo profiling of proteomically identified candidate molecules and demonstrates that S100A8, despite its abundance, resistance to steroids and known chemotactic activity, is unlikely to be an important determinant of LPS-induced neutrophilic lung inflammation in vivo.

Differential expression of the NMDA NR2B receptor subunit in motoneuron populations susceptible and resistant to amyotrophic lateral sclerosis

We have compared the expression pattern of NMDA receptor subunits (NR1 and NR2A-D)and NRI splice variants (NR1-1a/1b,-2a/2b,-3a/3b,4a/4b) in motor neuron populations from adult Wistar rats that are vulnerable (hypoglossal, XII) or resistant (oculomotor, III) to death in amyotrophic lateral sclerosis (ALS). The major finding was higher levels of expression of the NR2B subunit in the hypoglossal nucleus. Quantitative real-time PCR showed that NR1 was expressed at a greater level than any of the NR2 subunits (> 15 fold greater, P

Effector function of leucocytes from susceptible and resistant mice against distinct isolates of Candida albicans

Neutrophils and macrophages were generated in vitro from mice that display either high or low tissue susceptibilities to Candida albicans infection and their ability to phagocytose and kill three isolates of the yeast with different virulence characteristics was evaluated. In the absence of opsonization, phagocytosis by BALB/c and CBA/CaH neutrophils was comparable, but the killing was very poor. Opsonization with normal serum slightly decreased phagocytosis, but it had markedly different effects on killing, either enhancing or inhibiting candidacidal activity, depending on the combination of yeast isolate and mouse strain. In contrast, BALB/c macrophages showed high levels of phagocytosis and killing of both unopsonized yeasts and opsonized yeasts; whereas killing of unopsonized yeasts by CBA/CaH macrophages was poor, it was markedly enhanced by opsonization.

Fate of hairpin transcript components during RNA silencing and its suppression in transgenic virus-resistant tobacco

Transgenic tobacco plants, carrying a Potato virus Y (PVY)-NIa hairpin sequence separated by a unique unrelated spacer sequence were specifically silenced and highly resistant to PVY infection. In such plants neither PVY-NIa nor spacer transgene transcripts were detectable by specific quantitative real time reverse transcriptase PCR (RT-qPCR) assays of similar relative efficiencies developed for direct comparative analysis. However, small interfering RNAs (siRNAs) specific for the PVY sequence of the transgene and none specific for the LNYV spacer sequence were detected. Following infection with Cucumber mosaic virus (CMV), which suppresses dsRNA-induced RNA silencing, transcript levels of PVY-NIa as well as spacer sequence increased manifold with the same time course. The cellular abundance of the single-stranded (ss) spacer sequence was consistently higher than that of PVY dsRNA in all cases. The results show that during RNA silencing and its suppression of a hairpin transcript in transgenic tobacco, the ssRNA spacer sequence is affected differently than the dsRNA. In PVY-silenced plants. the spacer is efficiently degraded by a mechanism not involving the accumulation of siRNAs, while following suppression of RNA silencing by CMV, the spacer appears protected from degradation. Crown Copyright (c) 2006 Published by Elsevier B.V. All rights reserved.

Long-term persistence of multi-drug-resistant Salmonella enterica serovar Newport in two dairy herds

Objective - To evaluate the association between maintaining joint hospital and maternity pens;and persistence of multi-drug-resistant (MDR) Salmonella enterica serovar Newport on 2 dairy farms. Design - Observational study. Sample Population - Feces and environmental samples from 2 dairy herds. Procedure - Herds were monitored for fecal shedding of S enterica Newport after outbreaks of clinical disease. Fecal and environmental samples were collected approximately monthly from pens housing sick cows and calving cows and from pens containing lactating cows. Cattle shedding the organism were tested serially on subsequent visits to determine carrier status. One farm was resampled after initiation of interventional procedures, including separation of hospital and maternity pens. Isolates were characterized via serotyping, determination of antimicrobial resistance phenotype, detection of the CMY-2 gene, and DNA fingerprinting. Results - The prevalence (32.4% and 33.3% on farms A and B, respectively) of isolating Salmonella from samples from joint hospital-maternity pens was significantly higher than the prevalence in samples from pens housing preparturient cows (0.8%, both farms) and postparturient cows on Farm B (8.8%). Multi-drug-resistant Salmonella Newport was isolated in high numbers from bedding material, feed refusals, lagoon slurry, and milk filters. One cow excreted the organism for 190 days. Interventional procedures yielded significant reductions in the prevalences of isolating the organism from fecal and environmental samples. Most isolates were of the C2 serogroup and were resistant to third-generation cephalosporins. Conclusions and Clinical Relevance - Management practices may be effective at reducing the persistence of MDR Salmonella spp in dairy herds, thus mitigating animal and public health risk.

Identification of bla(CMY-7) and associated plasmid-mediated resistance genes in multidrug-resistant Escherichia coli isolated from dogs at a veterinary teaching hospital in Australia

Objectives: To determine clonality and identify plasmid-mediated resistance genes in 11 multidrug-resistant Escherichia coli (MDREC) isolates associated with opportunistic infections in hospitalized dogs in Australia. Methods: Phenotypic (MIC determinations, modified double-disc diffusion and isoelectric focusing) and genotypic methods (PFGE, plasmid analysis, PCR, sequencing, Southern hybridization, bacterial conjugation and transformation) were used to characterize, investigate the genetic relatedness of, and identify selected plasmid-mediated antimicrobial resistance genes, in the canine MDREC. Results: Canine MDRECs were divided into two clonal groups (CG 1 and 2) with distinct restriction endonuclease digestion and plasmid profiles. All isolates possessed bla(CMY-7) on an similar to 93 kb plasmid. In CG 1 isolates, bla(TEM), catA1 and class 1 integron-associated dfrA17-aadA5 genes were located on an similar to 170 kb plasmid. In CG 2 isolates, a second similar to 93 kb plasmid contained bla(TEM) and unidentified class 1 integron genes, although a single CG 2 strain carried dfrA5. Antimicrobial susceptibility profiling of E. coli K12 transformed with CG 2 large plasmids confirmed that the bla(CMY-7)-carrying plasmid did not carry any other antimicrobial resistance genes, whereas the bla(TEM)/class 1 integron-carrying plasmid carried genes conferring resistance to tetracycline and streptomycin also. Conclusions: This is the first report on the detection of plasmid-mediated bla(CMY-7) in animal isolates in Australia. MDREC isolated from extraintestinal infections in dogs may be an important reservoir of plasmid-mediated resistance genes.

The in vivo expression of actin/salt-resistant hyperactive DNase I inhibits the development of anti-ssDNA and anti-histone autoantibodies in a murine model of systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is characterised by the production of autoantibodies against ubiquitous antigens, especially nuclear components. Evidence makes it clear that the development of these autoantibodies is an antigen-driven process and that immune complexes involving DNA-containing antigens play a key role in the disease process. In rodents, DNase I is the major endonuclease present in saliva, urine and plasma, where it catalyses the hydrolysis of DNA, and impaired DNase function has been implicated in the pathogenesis of SLE. In this study we have evaluated the effects of transgenic overexpression of murine DNase I endonucleases in vivo in a mouse model of lupus. We generated transgenic mice having T-cells that express either wild-type DNase I (wt. DNase I) or a mutant DNase I ( ash. DNase I), engineered for three new properties - resistance to inhibition by G-actin, resistance to inhibition by physiological saline and hyperactivity compared to wild type. By crossing these transgenic mice with a murine strain that develops SLE we found that, compared to control nontransgenic littermates or wt. DNase I transgenic mice, the ash. DNase I mutant provided significant protection from the development of anti-single-stranded DNA and anti-histone antibodies, but not of renal disease. In summary, this is the first study in vivo to directly test the effects of long-term increased expression of DNase I on the development of SLE. Our results are in line with previous reports on the possible clinical benefits of recombinant DNase I treatment in SLE, and extend them further to the use of engineered DNase I variants with increased activity and resistance to physiological inhibitors.