Reducing time in detection of Listeria monocytogenes from food by MALDI-TOF mass spectrometry
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ORIGINAL ARTICLE
Reducing time in detection of Listeria monocytogenes from food by MALDI-TOF mass spectrometry Seda Karasu-Yalcin1
· Nursel Soylemez-Milli2 · Omer Eren1 · Kubra Eryasar-Orer1
Revised: 28 August 2020 / Accepted: 16 October 2020 © Association of Food Scientists & Technologists (India) 2020
Abstract In this study, direct detection of L. monocytogenes from liquid culture and enrichment broths containing foods was investigated by using MALDI-TOF MS. For determining the sole effect of food constituents on detection and accuracy of identification in enrichment broths, sterile foods were used before the experiments with food. L. monocytogenes could be detected in BHI broth after 24 h of incubation. Detection period was determined as 18 h for 39101 cfu/mL initial bacterial count in BHI broth containing sterile food. The period extended in ONE broth containing sterile garnish, which was 24 and 30 h for 39 101 and 1 cfu/mL inoculum, respectively. It was found that identification times in UHT milk were longer than that of canned garnish. In the experiments performed with foods having a specific microbiota; White cheese, iceberg lettuce, parsley and watermelon were used. Although no reliable identification was obtained by using White cheese, iceberg lettuce and parsley, L. monocytogenes could be detected in 24 h in the enrichment broth containing watermelon.
& Seda Karasu-Yalcin [email protected] Nursel Soylemez-Milli [email protected] Omer Eren [email protected] Kubra Eryasar-Orer [email protected] 1
Faculty of Engineering, Food Engineering Department, Bolu Abant Izzet Baysal University, Golkoy, Bolu 14030, Turkey
2
Scientific Industrial and Technological Application and Research Center, Bolu Abant Izzet Baysal University, Golkoy, Bolu 14030, Turkey
Detection was achieved during a single step enrichment in a reduced time of 24 h for even 1 cfu/mL initial inoculum. Keywords Foodborne pathogen · Rapid detection · MALDI-TOF MS · Listeria monocytogenes · Enrichment
Introduction Listeria monocytogenes is a Gram-positive, non-spore forming, aerobic to facultative anaerobic psychrotrophic bacteria. It is a foodborne pathogen that causes listeriosis and has high mortality rate (Churchill et al. 2006; Jamali et al. 2013). In the environment, the pathogen is most commonly isolated from soil and silage. In foods, it has been found in raw or processed foods including dairy products, meat, fruits and vegetables and seafood. L. monocytogenes is transmitted to susceptible individuals via consumption of contaminated foods (Churchill et al. 2006; Jamali et al. 2013; Vӓ̇limaa et al. 2015). Its ability to grow at low temperatures and both under aerobic and anaerobic conditions and in modified athmosphere packaging makes its control a great concern for the food industry (Vӓ̇limaa et al. 2015). Many countries have a zero tolerance policy towards the presence of L. monocytogenes in certain high risk foods (Jadhav et al. 2015). In addition to food safety risk, the release and subsequent recall of contamin
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