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.

In the present study, 13 Salmonella Infantis strains, which have been originated from Turkey, were selected due to their clinical and industrial relevance, sufficient biofilm producing capability and multidrug resistance. Although all tested strains were built up of thin pellicle, optimum pellicle formation has occurred at 28 C. All S. Infantis biofilms were categorized as 'bdar' morphotype following the incubation at both 20 and 28 C, while they were categorized as 'saw' morphotype at 37 C. Under a certain incubation temperature (28 C), 84.62% of strains have formed strong biofilm structures. By using the disk diffusion method, high levels of resistance have been observed among tested bacteria against nalidixic acid (100%), spectinomycin (100%), streptomycin (92.3%), tetracycline (92.3%), kanamycin (76.9%) and neomycin (76.9%). Further studies were performed with S. Infantis DMC 12 strain, due to its capability to produce biofilm and multidrug resistance phenotype. Gentamycin (>64 mg/mL, 2 £ MIC) and tetracycline (>128 mg/mL, 4 £ MIC) were determined as the most effective antibiotics against biofilm formation. The biofilm forms have showed increased antimicrobial resistance when it was compared to the planktonic bacteria. The highest resistance rates of the biofilm bacteria were observed to neomycin (12 £ MIC) followed by spectinomycin (10 £ MIC) and streptomycin (10 £ MIC). Biofilm structure was induced as a result of nalidixic acid, spectinomycin, tetracycline and neomycin treatment at sub-MIC concentrations of tested antibiotics.

The objective of this study was to determine the prevalence of Listeria species, specifically Listeria monocytogenes, in raw milk, pasteurized milk, white cheese, and homemade cheese. A total of 200 food samples were collected and analyzed to examine the presence of Listeria spp. The EN ISO 11290-1 method was used for isolation of Listeria. API Listeria test kit was used for biochemically characterization. Listeria spp. were isolated in 25 of the 200 samples (12.5%). The largest number of Listeria spp. was detected in homemade cheese (24%), followed by raw milk (18%), and white cheese (8%). Listeria spp. were not isolated from the pasteurized milk. The most common species isolated were Listeria innocua (5.5%); the remaining Listeria isolates were Listeria ivanovi (3.5%), Listeria welshimeri (3%), and Listeria monocytogenes (0.5%). Listeria monocytogenes was detected in only raw milk.

No abstract

The objective of this study was to determine the prevalence of Listeria species in raw milk, and dairy products. A total of 110 samples were obtained from randomly selected retail stores and local bazaars located in Ankara. Using TS EN ISO 11290-1 method, 23 samples were found positive for Listeria spp. The overall prevalence of Listeria spp. was 20.91%, in which L. innocua was the most commonly recovered species (6.36%). The remaining isolates were identified as L ivanovii (5.45%), L. monocytogenes (4.55%), and L welshimeri (4.55%). The L monocytogenes isolates were positive for the presence of hlyA gene. The highest prevalence of Listeria spp. was found in homemade cheese (9.09%), followed by raw milk (8.19%), and white cheese (3.64%). L monocytogenes was isolated from raw milk and homemade cheese in this study. In conclusion, the low hygienic quality dairy products may lead to listeriosis surveillance in Ankara.