Submitted to: Journal of Food Protection
Publication Type: Peer reviewed journal
Publication Acceptance Date: 6/17/2011
Publication Date: 11/1/2011
Citation: Parveen, S.S., Rippen, T., Schwarz, J., Luchansky, J.B., Wiedmann, M. 2011. Comparison of automated BAX polymerase chain reaction and standard culture methods for detection of Listeria monocyogenes in blue crab meat (Callinectus sapidus) and blue crab processing plants. Journal of Food Protection. 74(11):1930-1933. Interpretive Summary: Listeria monocytogenes is both common in nature and prevalent in a variety of foods, including crab meat. Listeriosis causes serious human illness and death, particularly for higher-risk individuals. The purpose of this study was to compare two different methods for recovery of this bacterium from crab meat and facilities that process crab meat. The BAX polymerase chain reaction (BAX PCR) method relies on amplification of DNA from this bacterium as an indication of whether or not cells of L. monocytogenes were present at some point. Although highly sensitive and specific, the drawback to this method is that is does not allow for subsequent isolation of living cells from a test sample. The second method relies on standard microbiology techniques and growth media and does permit the recovery of viable cells of this pathogen from a test sample. Both methods were evaluated to detect L. monocytogenes from 960 samples obtained from raw crabs, processed crab meat, and environmental samples from within a crab-meat processing facility between May and November of 2006. In total, 43 samples tested positive using the BAX PCR method and 30 tested positive for the pathogen by the microbiology-based method. The sensitivity and specificity of the BAX PCR method was 100%, whereas it was 93.7 and 99.7% for the standard microbiology-based method. These data confirm that L. monocytogenes is prevalent in crab meat and facilities that process crab meat, and that the BAX PCR method is as sensitive as the traditional microbiology-based method for recovery of this bacterium from such samples.
Technical Abstract: This study compared the BAX Polymerase Chain Reaction method (BAX PCR) with the Standard Culture Method (SCM) for detection of L. monocytogenes in blue crab meat and crab processing plants. The aim of this study was to address this data gap. Raw crabs, finished products and environmental sponge samples were collected monthly from seven processing plants during the plant operations (May-November 2006). For detection of L. monocytogenes from raw crabs and finished product, enrichment was performed in Listeria enrichment broth (LEB), whereas for environmental samples Demifraser broth was used, followed by plating on both Oxford agar and Listeria monocytogenes Plating Medium. Enriched samples were also analyzed by BAX PCR. A total of 960 samples were examined, 43 were positive by BAX PCR and 30 by SCM. There was no significant difference (P=0.05) between the incidence of L. monocytogenes in crab meat and crab processing plants detected by both methods. However, SCM performed better for detecting L. monocytogenes in raw crabs than the BAX PCR. Twelve and 23 of environmental samples were positive for L. monocytogenes by SCM and BAX PCR, respectively, whereas only 1 and 5 finished products were positive. The overall sensitivity and specificity for BAX PCR were 100%, whereas for SCM were 93.7% and 99.7% respectively. The results of this study indicate that BAX PCR is as sensitive as SCM for detecting L. monocytogenes in crab meat and crab processing plants.