%0 Journal Article
%T Role of subtyping in detecting Salmonella cross contamination in the laboratory
%A Niall De Lappe
%A Jean O Connor
%A Geraldine Doran
%A Genevieve Devane
%A Martin Cormican
%J BMC Microbiology
%D 2009
%I BioMed Central
%R 10.1186/1471-2180-9-155
%X Serotyping and antimicrobial susceptibility testing was performed on all Salmonella isolates received in the NSRL. Phage typing was performed on all S. Typhimurium and S. Enteritidis isolates while multi-locus variance analysis (MLVA) was performed on selected S. Typhimurium isolates. Pulsed field gel electrophoresis (PFGE) using the PulseNet standard protocol was performed on selected isolates of various serovars.Twenty-three incidents involving fifty-six isolates were identified as likely to represent cross contamination. The probable sources of contamination identified were the laboratory positive control isolate (n = 13), other test isolates (n = 9) or proficiency test samples (n = 1).The scale of laboratory cross-contamination in bacteriology is most likely under recognized. Testing laboratories should be aware of the potential for cross-contamination, regularly review protocols to minimize its occurrence and consider it as a possibility when unexpected results are obtained.Laboratory contamination can be defined as the inadvertent addition of analytes to test samples during sample collection, transportation or analysis. There is a high level of awareness of the potential for cross contamination when using nucleic acid amplification methods [1]. Although conventional microbial culture also represents amplification of signal to detectable levels there is relatively little systematic data on the frequency of cross contamination in conventional microbiology. In clinical laboratories cross contamination can lead to misdiagnosis of patients, inappropriate treatment or isolation of patients and investigation of pseudo-outbreaks. Detection of pathogens in food items can lead to very significant economic loss [2] therefore it is important to ensure that positive results reflect true product contamination.Sources of microbial laboratory contamination may include positive control strains, cultures of recent isolates, laboratory workers and airborne exogenous material suc
%U http://www.biomedcentral.com/1471-2180/9/155