Lactobacillus spp. inhibit the growth of Cronobacter sakazakii ATCC 29544 by altering its membrane integrity
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The effect of the cell-free culture supernatants (CFCSs) from different Lacobacillus spp. on growth ability of Cronobacter sakazakii ATCC 29544 was investigated by time-killing studies. The antimicrobial effect was evaluated using crude and 2.5 × concentrated CFCSs. Most of the CFCSs showed a dose-dependent antimicrobial activity, with the greatest C. sakazakii growth inhibition exerted by the CFCS 2.5 × of Lactobacillus casei rhamnosus ATCC 7469. Indeed, C. sakazakii growth was completely inhibited after 4 h of incubation with the crude CFCSs of L. casei rhamnosus and Lactobacillus acidophilus and after only 2 h using the related 2.5 × CFCSs. The flow cytometric analysis revealed that CFCSs altered the permeability of C. sakazakii cell membrane, showing 55% of live cells after 30 min of treatment with 2.5 × CFCSs of L. casei rhamnosus and L. acidophilus, reaching 1% of live cells after 2 h of exposure. The CFCSs of L. casei rhamnosus and L. acidophilus have showed anti-Cronobacter activity, determining a progressively inhibition of C. sakazakii growth as result of alterations in its membrane permeability.
KeywordsLactobacilli Cell-free culture supernatants Antimicrobial activity C. sakazakii Membrane integrity Flow cytometry
WB conceive the study and RC designed the experiments; SF, EC and RC performed the experiments and analysed data; AM carried out FCM analysis; RC and WB wrote the manuscript.
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Conflict of interest
The authors declare that they have no conflict of interest.
- Commission Regulation (EC) No 1441/2007 of 5 December 2007 amending Regulation (EC) No 2073/2005 on microbiological criteria for foodstuffs (Text with EEA relevance). http://eur-lex.europa.eu/legal-content/EN/TXT/?qid=1432490174116&uri=CELEX:32007R1441. Accessed 7 Dec 2007