Proceeding of Veterinary and Animal Science Days 2015, 15th- 17th July, Milan, Italy 

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ABSTRACT  

Listeria monocytogenes (LM) is a foodborne pathogen responsible of listeriosis. In the spreading of this 
pathology, milk and dairy products are key reservoir for this pathogen1. Food processing represents one of the 
major steps that could be linked to LM growth. Inhibition of LM growth through competition of Lactococcus lactis 
(LAC) could represent a solution to this problem. Exoproteome of LM and two different strains of Lactic Acid 
Bacteria in co-culture have been studied in order to highlight mechanisms of bacterial competition useful to 
improve food safety. Two different strains of LAC and one strain of LM were cultivated in appropriate medium 
cultures (BHI), also in competition. Filtrated cultures (SECRETOME) were lyophilized and resuspended for 
proteomics analysis. Shotgun analysis on each secretome was performed on nano UPLC-MS system. Obtained 
data reveal, during competition, the higher production by LM of moonlighting protein Enolase and Glucose 6 
Phosphate isomerase, of Septation ring formation regulator EzrA, involved into cell replication and the lower 
secretion of Endopeptidase P60. In parallel, L. lactis produced higher amounts of Secreted 45 kDa protein and 
switched from lantibiotic Nisin A production to Nisin Z production. In competition with LM, LAC strain 
investigated produce higher amounts of Secreted 45 kDa protein with peptidoglycan lytic activity and the 
selective secretion of Nisin Z probably to improve lantibiotic solubility in less acidic environment. Next step will 
be validation of obtained results in dairy products. These results are of interesting to design new strategies of 
fighting LM as contaminant in food from animal origin.  

Work supported by Ministry of Health-CCM “Milano EXPO 2015 Project: Garantire la sicurezza alimentare- 
Valorizzare le produzioni” 

 

 
REFERENCES  
Greenwood, M. H.; Roberts, D.; Burden, P., The occurrence of Listeria species in milk and dairy products: a national 
survey in England and Wales. International journal of food microbiology 1991, 12, (2), 197-206. 

 

 

 

 

CORRESPONDING AUTHOR 

Isabella Alloggio,  

isabella.alloggio@unimi.it 

 

 

Food Safety: Secretome of Lactococcus 

lactis and Listeria monocytogenes in 

competition. 

I. Alloggio
2
, C. Piras

2
, V. Greco

3,4
, A. Soggiu

2
, N. Losio

5
, L. Bonizzi

2
, A. 

Urbani
3,4

, P.Roncada
1,2

. 

1 
Italian Experimental Institute L. Spallanzani, Milano, Italy 

2
 Department of Veterinary Sciences and Public Health (DIVET), University of 

Milan, Milan, Italy 

3
 S. Lucia Foundation - IRCCS, Rome, Italy 

4
 Department of Internal Medicine, University of Rome Tor Vergata, Rome, 

Italy 

5 Experimental Zooprofilattico Institute of Lombardia and Emilia Romagna, 

Brescia, Italy