Immunohistochemical detection of EGFR in paraffin-embedded tumor tissues: variation in staining intensity due to choice of fixative and storage time of tissue sections.

The epidermal growth factor receptor (EGFR) is highly expressed in a variety of solid malignant tumors and its expression has been correlated with disease progression and poor survival. With the advent of targeted therapies, especially IMC-C225 (Cetuximab), a monoclonal antibody (MAb) directed against the EGFR, there is an increasing interest in immunohistochemistry (IHC)-based EGFR screening methods using paraffin-embedded tumor specimens to select cancer patients eligible for treatment with Cetuximab. With the EGFRpharmDX kit, a complete assay for demonstration of EGFR is now available. Because no information about the preservation of the EGFR under various conditions of fixation is available, we performed a prospective study on a panel of commonly used fixatives to determine optimal tissue preservation protocols. The stability of the epitope on cut tissue sections stored for a period up to 24 month was also tested using material originating from patients with head and neck cancer, non-small-cell lung carcinomas, and colorectal adenocarcinomas. Depending on the fixative used and the time of storage of cut tissue sections, a variation in the determined level of EGFR expression was demonstrated compared with the most optimal fixation procedure.

Influence of age, sex and herd characteristics on the occurrence of Verocytotoxin-producing Escherichia coli O157 in Danish dairy farms.

Verocytotoxin-producing Escherichia coli (VTEC) O157 is an important emerging human pathogen. Cattle are considered to be the main reservoir for VTEC O157. The objectives of this study were to determine the prevalence of VTEC O157 in Danish dairy herds and to investigate the relationship between shedding of VTEC O157 and a number of animal and herd characteristics. Sixty dairy farms were visited once in August-October, and from each herd faecal samples from up to 50 animals were analysed for VTEC O157 by enrichment, immunomagnetic separation (IMS), and plating on selective agar. In total, 2419 animals were sampled, and 3.6% of these excreted VTEC O157. These animals were located on 10 farms (17%). On average, 21% of the sampled animals in the positive herds excreted VTEC O157. Register data, including age, sex, breed, housing conditions and herd composition, were extracted from a database. No influence of herd size or housing conditions was found. A strong effect of age was seen with 2-6-month-old calves as the high-risk age group (8.6% positive) in contrast to calves <2 months (0.7%) and cows (2.4%). There was a non-significant tendency of bull calves to have a higher prevalence than heifers within the age group of 2-6 months. Significantly, more of the herds characterised by having relatively many bull calves or many animals bought into the herd were positive for VTEC O157. Despite the low incidence of human VTEC O157 infections in Denmark, the prevalence in Danish dairy herds was found to be at a similar level as in many other countries.