Abstract
The aim of the present study was the determination of the prevalence and antibiotic resistance of L. monocytogenes in ready-to-eat (RTE) foods in Ankara, Turkey. In order to detect and isolate L. monocytogenes from 201 RTE food samples, the EN ISO 11290:1 method was used. All isolates were identified using the polymerase chain reaction. The strains were also confirmed by the detection of the hemolysin gene (hlyA). The overall prevalence of L. monocytogenes was 8.5% among the food samples. Seventeen L. monocytogenes strains were examined by the disk diffusion assay for their resistance to 23 antibiotics. All strains were susceptible to erythromycin, clarithromycin, streptomycin, gentamicin, vancomycin, imipenem, trimethoprim, and chloramphenicol, while all strains were resistant to nalidixic acid, ampicillin, penicillin G, linezolid, and clindamycin. The higher resistance was found against oxacillin (94.1%), kanamycin (76.5%), levofloxacin (70.6%), and teicoplanin (64.7%), followed by amoxicillin/clavulanic acid (53.0%), rifampicin (47.1%), and ciprofloxacin (35.3%). A lower incidence of resistance was observed against tetracycline (5.9%), meropenem (5.9%), and trimethoprim/sulfamethoxazole (17.7%). All isolates were multidrug resistant showing resistance to at least three antibiotic classes. High L. monocytogenes prevalence among analyzed RTE foods represents a high risk for public health. Our findings show a high prevalence of L. monocytogenes in RTE foods in Turkey. More effective control strategies for L. monocytogenes are needed to reduce both prevalence and resistance of L. monocytogenes in Turkish RTE foods.
Highlights
Listeria species include Gram-positive, facultatively anaerobic, psychrotrophic, rod-shaped, non-spore-forming bacteria [1]
Detection of L. monocytogenes in RTE Foods. e presence of Listeria was identified in 41 (20.4%) of the 201 RTE food samples (Table 1). e 16S rRNA sequence analysis indicated the highest prevalence of L. monocytogenes (8.5%, 17/201) in the food samples, followed by L. innocua (7.0%, 14/201), L. welshimeri (4.5%, 9/201), and L. seeligeri (0.5%, 1/201). e analysis of the 16S rRNA sequence allowed separating the Listeria spp. isolates in six clusters
Vegetable salads were the only raw products contaminated by L. monocytogenes in our study, with a prevalence of 11.8%. e isolation rate of L. monocytogenes in the vegetable salads was reported as 5.56% in Brazil [22], 25.8% in China [37], 4.1% in Nigeria [47], 22.5% in Malaysia [48], and 4.18% in Spain [49]. e presence of L. monocytogenes in the vegetable salads could be attributed to cross contamination and may occur during harvesting from the equipment, transport containers, or human handling
Summary
Listeria species include Gram-positive, facultatively anaerobic, psychrotrophic, rod-shaped, non-spore-forming bacteria [1]. The genus Listeria contains eighteen di erent species [2], of which L. monocytogenes and L. ivanovii are pathogenic, and the former is the major causative agent of listeriosis in human and other mammals [3]. The incidence of listeriosis is rarely encountered compared to illnesses caused by other food-borne pathogens such as Salmonella spp., Escherichia coli, or Campylobacter jejuni, it can be lethal for newborns, the elderly, immunocompromised individuals, and pregnant women [4, 5]. L. monocytogenes is highly prevalent in clinical and food samples due to its ability to grow over a wide range of temperature including refrigeration temperatures and pH as low as 4.4, in high salinity (40% w/v), low water content, and hypoxic conditions [5, 6].
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