External quality assessment for molecular typing of Salmonella 2013-2015: performance of the European national public health reference laboratories.

We report the results of three consecutive External Quality Assessments (EQAs) for molecular subtyping of Salmonella to assess the performance of the European national public health reference laboratories (NPHRLs). The EQA included the molecular typing methods used for European enhanced surveillance of human Salmonella infections: pulsed field gel electrophoresis (PFGE), including gel analysis by the use of the software BioNumerics, and 5-locus multiple locus variable number of tandem repeat analysis (MLVA) for serovar Typhimurium. The participation in the PFGE laboratory part was higher (27/35) than in the gel analysis (19/35) and MLVA (15/35), suggestive of the need for capacity building in methods requiring specialized equipment (MLVA) or software (gel analysis). The majority (25/27) of the participating NPHRLs produced inter-laboratory comparable PFGE gel(s). Two laboratories continued to produce low-quality gels and should have additional technical assistance in the future. In particular, two gel quality evaluation parameters, measuring "image acquisition and running conditions" and "bands", were identified to cause gel quality problems throughout the EQAs. Despite the high number of laboratories participating in the PFGE laboratory part, the participation in gel analysis was low, although increasing. In the MLVA part, the NPHRLs correctly assigned 96% (405/420) allelic profiles according to the nomenclature. In conclusion, the EQAs identified critical parameters for unsuccessful performance and helped to offer assistance to those laboratories that needed it most. The assessments supported the development of quality in molecular typing and promoted the harmonization of subtyping methods used for EU/EEA-wide surveillance of human Salmonella infections.

Diagnosis of Clostridium difficile: real-time PCR detection of toxin genes in faecal samples is more sensitive compared to toxigenic culture.

The diagnosis of Clostridium difficile infection (CDI) requires the detection of toxigenic C. difficile or its toxins and a clinical assessment. We evaluated the performance of four nucleic acid amplification tests (NAATs) detecting toxigenic C. difficile directly from faeces compared to routine toxigenic culture. In total, 300 faecal samples from Danish hospitalised patients with diarrhoea were included consecutively. Culture was performed in duplicate (routine and 'expanded toxigenic culture': prolonged and/or re-culture) and genotypic toxin profiling by polymerase chain reaction (PCR), PCR ribotyping and toxinotyping (TT) were performed on culture-positive samples. In parallel, the samples were analysed by four NAATs; two targeting tcdA or tcdB (illumigene C. difficile and PCRFast C. difficile A/B) and two multi-target real-time (RT) PCR assays also targeting cdt and tcdC alleles characteristic of epidemic and potentially more virulent PCR ribotypes 027, 066 and 078 (GeneXpert C. difficile/Epi and an 'in-house RT PCR' two-step algorithm). The multi-target assays were significantly more sensitive compared to routine toxigenic culture (p < 0.05) and significantly more robust to inhibition compared to PCRFast (p < 0.001). Duplicate 'expanded toxigenic culture' increased the culture-positive rate by 29% compared to routine culture. The ability of the GeneXpert and in-house assays to correctly classify PCR ribotype 027 was high (>95%), and in-house PCR displayed 100% correct identification of PCR ribotypes 066 and 078. Furthermore, the presence of the PCR enhancer bovine serum albumin (BSA) was found to be related to high sensitivity and low inhibition rate. Rapid laboratory diagnosis of toxigenic C. difficile by RT PCR was accurate.

NBCn1 and NHE1 expression and activity in DeltaNErbB2 receptor-expressing MCF-7 breast cancer cells: contributions to pHi regulation and chemotherapy resistance.

Altered pH-regulatory ion transport is characteristic of many cancers; however, the mechanisms and consequences are poorly understood. Here, we investigate how a truncated, constitutively active ErbB2 receptor (DeltaNErbB2) common in breast cancer impacts on the Na(+)/H(+)-exchanger NHE1 and the Na(+),HCO(3)(-)-cotransporter NBCn1 in MCF-7 human breast cancer cells and address the roles of these transporters in chemotherapy resistance. Upon DeltaNErbB2 expression, mRNA and protein levels of NBCn1, yet not of NHE1, increased several-fold, and the localization of both transporters was altered paralleling extensive morphological changes. The rate of pH(i) recovery after acid loading increased by 50% upon DeltaNErbB2 expression. Knockdown and pharmacological inhibition confirmed the involvement of both NHE1 and NBCn1 in acid extrusion. NHE1 inhibition or knockdown sensitized DeltaNErbB2-expressing cells to cisplatin-induced programmed cell death (PCD) in a caspase-, cathepsin-, and reactive oxygen species-dependent manner. NHE1 inhibition augmented cisplatin-induced caspase activity and lysosomal membrane permeability followed by cysteine cathepsin release. In contrast, NBCn1 inhibition attenuated cathepsin release and had no net effect on viability. These findings warrant studies of NHE1 as a potential target in breast cancer and demonstrate that in spite of their similar transport functions, NHE1 and NBCn1 serve different functions in MCF-7 cells.