Detection and Pulsed-Field Gel Electrophoresis Typing of Listeria monocytogenes Isolates from Milk Vending Machines in Croatia

Abstract

The aim of the present study was to evaluate the persistence of Listeria monocytogenes in raw milk from vending machines, based on culture and molecular detection of pathogen and Pulsed-Field Gel Electrophoresis typing. From December 2015 to January 2017, a total of 319 milk samples from 36 vending machines were examined for the presence and count of L. monocytogenes by reference methods ISO 11290:1 and ISO 11290:2. Molecular detection of pathogens was performed by loop-mediated isothermal DNA amplification (LAMP) coupled with bioluminescence (Molecular Detection Assay). L. monocytogenes was detected by MDA in 14 milk samples (4.38%) from four farms, compared to eight positive samples (2.5%) retrieved by a reference ISO method. Cultivable L. monocytogenes isolates were subjected to Pulsed-Field Gel Electrophoresis typing and pulsotypes were compared with those obtained during the previous survey in Croatia (2014‒2015). It was found that identical PFGE patterns of L. monocytogenes occur in milk samples of the same producer over a three-year period, indicating the persistence of pathogens in raw milk vending machines. The results obtained support the need for more effective control of milk in the entire food chain.

Biogenic Amine Content in Retailed Cheese Varieties Produced with Commercial Bacterial or Mold Cultures

“…The microbiological properties of cheese depend on the type of cheese, i.e., hygiene and production technology, especially heat treatment of milk and the use of dairy cultures [4,11]. The microbiota of raw milk under poor hygiene conditions may contain pathogenic bacteria, such as Listeria monocytogenes and Staphylococcus aureus, but also fecal or environmental contaminating bacteria, such as coliforms or enterococci [12][13][14]. In this context, coliform bacteria and lactic acid bacteria (LAB), mainly enterococci, are responsible for the formation of biogenic amines in unprocessed dairy products [15,16].…”

Challenging Sustainable and Innovative Technologies in Cheese Production: A Review

“…From the public health point of view, the microbiological safety of milk should be always discussed through a tight connection with animal health and environmental hygiene. Our recent findings showed that raw milk from vending machines may be contaminated, although rarely, with foodborne pathogens, such as L. monocytogenes [191,192], or multi-resistant Staphylococcus aureus [193].…”

The role of vending channels in marketing: A systematic review and taxonomy of studies

“…The selling of raw milk through vending machines has been discussed in the context of related risks of milk contamination with various pathogenic bacteria that can cause foodborne diseases (Giacometti et al ., 2015). Some of the identified articles reported vending samples with relatively low levels of milk contamination (Bianchi et al ., 2013; Dalzini et al ., 2016) corresponding to well‐established national and international standards for microbiological quality (Angelidis et al ., 2016; Vietoris et al ., 2016; Torkar et al ., 2017; Zdolec et al ., 2019). However, the level of microbiological quality varies according to the methodological approach used to test the milk samples (Giacometti et al ., 2012; Mikulec et al ., 2019; Zdolec et al ., 2019).…”