Prevalence, populations and pheno- and genotypic characteristics of Listeria monocytogenes isolated from ready-to-eat vegetables marketed in São Paulo, Brazil.
Listeria monocytogenes is a foodborne pathogen of great concern due to the high fatality rates of listeriosis. The consumption of RTE vegetables has increased in Brazil over the last two decades, but little is known about the risks associated to the consumption of these products. This study evaluated the prevalence and counts of L. monocytogenes in 512 packages of ready-to-eat vegetables marketed in São Paulo. The isolates were characterized for their serotypes, ribotypes, positivity for virulence genes inlA, inlC and inlJ, resistance to chlorine, growth rate variability and capability to form biofilm on stainless steel (AISI 304, #4) coupons. L. monocytogenes was detected in 3.1% of the samples. Only five samples presented countable levels, with counts between 1.0×10(1) and 2.6×10(2)CFU/g. Isolates belonged to serotypes 1/2b or 4b and most were positive for genes inlC and inlJ. Ribotypable isolates were grouped into four groups: 1038 (69.4%), 19175 (11.3%), 19191 (17.7%) and 18604 (one isolate). Most isolates survived to exposure to 125 ppm of a chlorine-based disinfectant for 3 min. All isolates were capable to attach to the coupons, reaching counts above 4 log(10) CFU/cm(2) and the growth rate (μ) at 25°C of the majority of the isolates varied between 0.1 and 0.2 log OD/h, but for few strains the μ was as high as 0.26 log OD/h. Results of this survey indicate that RTE vegetables may be vehicles of L. monocytogenes strains with limited variation in serotype, ribotype and virulence factors but varying significantly in resistance to chlorine disinfectants, capability of forming biofilm and growth rate. Data obtained is of foremost importance to serve as baseline for the development of scientific-based policies to control the incidence of L. monocytogenes in RTE vegetables in Brazil.
Department of Food and Experimental Nutrition, Faculty of Pharmaceutical Sciences, University of São Paulo. São Paulo, SP, Brazil. assantana@usp.br
Anderson S
AS
Sant'Ana
Maria Crystina
MC
Igarashi
Mariza
M
Landgraf
Maria Teresa
MT
Destro
Bernadette D G M
BD
Franco
D058491:Bacterial Load; D018441:Biofilms; D001938:Brazil; D004202:Disinfectants / Q000494:pharmacology; D024881:Drug Resistance, Bacterial; D057140:Fast Foods / Q000382:microbiology*; D005516:Food Microbiology; D005838:Genotype; D008089:Listeria monocytogenes / Q000187:drug effects / Q000302:isolation & purification / Q000472:pathogenicity / Q000502:physiology*; D008088:Listeriosis / Q000382:microbiology / Q000635:transmission; D015995:Prevalence; D021521:Ribotyping; D013193:Stainless Steel; D014675:Vegetables / Q000382:microbiology*; D037521:Virulence Factors / Q000235:genetics
D004202:Disinfectants; D037521:Virulence Factors; D013193:Stainless Steel