No abstract

No abstract

No abstract

RDEC-1, an Escherichia coli strain that adheres to rabbit mucosa and causes an attaching, effacing lesion, expresses the pilus adhesin AF/Rl which determines in vitro attachment to rabbit intestinal brush borders. In order to determine the role of AF/Rl pili in the pathogenesis of enteropathogenic diarrhea in rabbits, we localized the genes for AF/Rl expression, constructed an AF/R1strain, and compared the virulence of the AF/ Rl and AF/R1strains with particular attention to the development of attaching, effacing lesions. We introduced TnS into the 86-megadalton (MDa) conjugative plasmid known to mediate expression of AF/Rl pili and transferred the derivative plasmids into laboratory strain HB101. Transconjugant M5 was found to contain the 86-MDa plasmid from RDEC-1 and to express AF/Rl pili. Pilus expression on M5 was confirmed by reaction with antiserum raised against purified AF/Rl pili and allowed the bacteria to adhere to the rabbit ileum in an in vitro assay. Three Tn5 insertions in the 86-MDa plasmid were obtained which resulted in loss of AF/Rl expression. Part of the plasmid was mapped, including a region necessary for AF/Rl pilus expression. AF/R1mutant strain M34 was constructed, and its pathogenesis was investigated. M34 produced disease in rabbits but was less virulent than the parent. The characteristic effacing lesions of RDEC-1 and enteropathogenic E. coli developed in the intestine of rabbits infected with either M34 or RDEC-1, although with M34 they were much less frequent and did not involve the small bowel. We conclude that AF/Rl pilus expression is not essential for the attaching, effacing lesion but serves as an accessory virulence factor which promotes an initial interaction of RDEC-1 with normal epithelial cells. * Corresponding author. .thelial cells (M cells) over the Peyer's patch in the small intestine (13, 14). In their experiments, they used a Shigella flexneri derivative strain, D15, which contained an 85megadalton (MDa) plasmid from RDEC-1 and expressed AF/ Rl pili (10). D15 bacteria were found to adhere specifically to M cells hours after inoculation; however, they did not result in effacing lesions with elongation of microvilli characteristic of RDEC-1 (14). Hence, AF/Ri appears to mediate the attachment of bacteria to M cells early in infection but is not sufficient for attaching, effacing lesions. In the present study, we characterized the 86-MDa plasmid of RDEC-1, constructed mutants in AF/Rl pilus expression, and tested the virulence of an AF/Rl mutant with particular emphasis on its ability to promote attaching, effacing lesions of the absorptive epithelial cells of the ileum, cecum, and colon. MATERIALS AND METHODS Bacterial strains and media. E. coli RDEC-1 is 015:H-:K? and is resistant to nalidixic acid. Strains 640 and HS are commensal strains that were isolated from rabbits and humans, respectively. These were from the collection in the Department of Gastroenterology, Walter Reed Army Institute of Research. HB101 (5) and HU735, the strain containing the Tn5 donor plasmi...

Dose reductions of pegylated interferon alpha and ribavirin may be avoided by using growth factors. This phase II clinical trial assesses the dose, efficacy and safety of darbepoetin alpha and filgrastim for treatment of anaemia and neutropenia associated with combination therapy for hepatitis C virus (HCV). Chronic hepatitis C patients (n = 101) received pegylated interferon alpha-2b (1.5 mug/kg once weekly) and ribavirin (800-1400 mg once daily). Patients with anaemia [haemoglobin (Hb) /= 0.75 x 10(9)/L and <10 x 10(9)/L. During antiviral therapy, 52% of patients required darbepoetin alpha, filgrastim or both. Hb at the time of darbepoetin alpha initiation was 10.2 +/- 0.4 g/dL. After 81 days of darbepoetin alpha, Hb increased by 1.9 +/- 1.0 g/dL to 12.1 +/- 1.1 g/dL (P < 0.0001). Filgrastim resulted in a significant increase in ANC [0.75 +/- 0.16 x 109/L to 8.28 +/- 5.67 x 10(9)/L (P < 0.0001)]. In treatment-naïve patients, 48% achieved sustained virological response (SVR), whereas 27% of patients previously treated with a course of pegylated interferon alpha achieved SVR. Low viral load, nongenotype 1 and treatment with growth factors were independently associated with SVR. Mild and severe anaemia were associated with quality of life impairments. Darbepoetin alpha resulted in an improvement in the Vitality domain of Short Form-36. No significant adverse events were related to growth factors. During anti-HCV therapy, filgrastim improved neutropenia and darbepoetin alpha improved both anaemia and quality of life. Future randomized clinical trials are needed to establish the impact of growth factors in improving sustained virological response.