Title: Characterisation of L. monocytogenes strains isolated from salad vegetables

Authors: Jeyaletchumi Ponniah; Tunung Robin; Son Radu; Yoke Kqueen Cheah; Farinazleen Mohamad Ghazali; Mitsuaki Nishibuchi; Yoshitsugu Nakaguchi; Pradeep Malakar

Addresses: Public Health Department, Ministry of Health, Food Safety and Quality Division, Federal Government Administrative Centre, Level 3, Block E7, Parcel E, 62590 Putrajaya, Malaysia ' Faculty of Applied Science, University College Sedaya International University (UCSI), No. 1, Jalan Menara Gading, UCSI Heights, Cheras, 56000, Wilayah Persekutuan, Malaysia ' Food Safety Research Centre, Faculty of Food Science and Technology, Universiti Putra Malaysia, 43400, UPM, Serdang, Selangor Darul Ehsan, Malaysia ' Department of Biomedical Sciences, Faculty of Medicine and Health Sciences, University Putra Malaysia, 43300 UPM Serdang, Selangor, Malaysia ' Faculty of Food Science and Technology, Centre of Excellence for Food Safety, Universiti Putra Malaysia, 43400, UPM, Serdang, Selangor Darul Ehsan, Malaysia ' Division of Human Nature Dynamics, Center for Southeast Asian Studies, Kyoto University, 46 Shimoadachi-cho, Yoshida Sakyo-ku, Kyoto, 606-8501, Japan ' Division of Human Nature Dynamics, Center for Southeast Asian Studies, Kyoto University, 46 Shimoadachi-cho, Yoshida Sakyo-ku, Kyoto, 606-8501, Japan ' Gut Health and Food Safety, Institute of Food Research, Norwich University Park, NR4 7UA, Norwich, UK

Abstract: Seventy-one strains of L. monocytogenes isolated from raw salad vegetables consumed in the minimally processed state in Malaysia were characterised by serotyping, random amplified polymorphic DNA-polymerase chain reaction analysis (RAPD-PCR) and antimicrobial susceptibility testing. Based on serotyping, only one strain belonged to serotype 4 while the rest were from serotype 1. RAPD-PCR typing was carried out using two primers, i.e., OPAR-8 and GEN 1-50-09. Based on RAPD-PCR fingerprinting, the strains could be grouped into six composite profile groups and a solitary isolate. The isolates were also evaluated against 16 antibiotics. Excluding nalidixic acid and oxacillin for which L. monocytogenes has natural resistance, the highest prevalence of resistance was against cephalexin. None of the isolates were resistant against imipenem and kanamycin. The multiple antibiotic resistance index (MARI) ranged from 0.06 to 0.63. It was found that most (82%) isolates were susceptible to antibiotics commonly used in veterinary and human listeriosis treatment.

Keywords: L. monocytogenes; raw vegetables; salad vegetables; serotyping; RAPD; random amplified polymorphic DNA; polymerase chain reaction; PCR; antimicrobial susceptibility; Malaysia; antibiotics; antibiotic resistance.

DOI: 10.1504/IJFSNPH.2015.067562

International Journal of Food Safety, Nutrition and Public Health, 2015 Vol.5 No.2, pp.137 - 150

Accepted: 19 Jul 2014
Published online: 17 Feb 2015 *

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