Differential expression of InlB and ActA in Listeria monocytogenes in selective and nonselective enrichment broths.
OBJECTIVE
To investigate the effect of selective and nonselective media on the expression of ActA and InlB proteins in Listeria monocytogenes.


RESULTS
Polyclonal antibodies to InlB and ActA were used in western blotting to determine the effect of selective (BLEB, UVM, and FB) or nonselective (BHI and LB) enrichment broths or hotdog exudates. Of the 13 L. monocytogenes serotypes tested, 11 and 12 serotypes showed a strong InlB expression in brain heart infusion (BHI) and Luria-Bertani (LB), respectively, while only seven and one serotypes showed a strong ActA expression in these two respective broths, and others showed a weaker or no expression. On the contrary, in selective broths, expression of InlB was either very weak or undetectable. However, ActA expression was stronger in 12 serotypes when grown in buffered Listeria enrichment broth (BLEB), 11 in University of Vermont medium (UVM), and 10 in Fraser broth (FB). When tested in hotdog exudates, InlB and ActA were detected in serotypes grown at 37 degrees C but not at 4 degrees C. Transmission electron microscopy, enzyme-linked immunosorbent assay, and mRNA analysis further supported these observations.


CONCLUSIONS
Overall, selective enrichment broths promote ActA while nonselective broths promote InlB expression.


CONCLUSIONS
As commonly recommended enrichment broths show differential InlB and ActA expression, proper media must be selected to avoid false results during antibody-based detection of L. monocytogenes.
Lathrop
A A
AA
Molecular Food Microbiology Laboratory, Department of Food Science, Purdue University, West Lafayette, Indiana 47907-2009, USA.
Banada
P P
PP
Bhunia
A K
AK
D001426:Bacterial Proteins / Q000235:genetics*; D001431:Bacteriological Techniques; D015153:Blotting, Western / Q000379:methods; D003470:Culture Media; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D005516:Food Microbiology; D008089:Listeria monocytogenes / Q000145:classification / Q000378:metabolism*; D008565:Membrane Proteins / Q000235:genetics*; D046529:Microscopy, Electron, Transmission; D012333:RNA, Messenger / Q000032:analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012703:Serotyping; D013045:Species Specificity; D013696:Temperature
D001426:Bacterial Proteins; D003470:Culture Media; D008565:Membrane Proteins; D012333:RNA, Messenger; C095768:inlB protein, Listeria monocytogenes; C072980:actA protein, Listeria monocytogenes