RESUMO
AIMS: This study evaluated the efficacy of essential oil from Origanum vulgare L. (oregano; OVEO) and Rosmarinus officinalis L. (rosemary; ROEO) to inactivate sessile cells of Salmonella enterica serovar Enteritidis 86 (SE86) in young and mature biofilms formed on stainless steel. METHODS AND RESULTS: Ultrastructural alterations and damage in different physiological functions caused by OVEO and ROEO in noncultivable sessile cells of SE86 were investigated using scanning electron microscopy and flow cytometry. OVEO (2·5 µl ml-1 ) and ROEO (40 µl ml-1 ) were effective to eradicate young and mature biofilms formed by SE86 sessile cells on stainless steel surfaces; however, the efficacy varied with exposure time. OVEO and ROEO caused alterations in morphology of SE86 sessile cells, inducing the occurrence of bubbles or spots on cell surface. OVEO and ROEO compromised membrane polarization, permeability and efflux activity in noncultivable SE86 sessile cells. These findings show that OVEO and ROEO act by a multitarget mechanism on SE86 membrane functions. CONCLUSIONS: ROEO and OVEO showed efficacy to eradicate SE86 sessile cells in preformed biofilms on stainless steel, displaying a time-dependent effect and multitarget action mode on bacterial cell membrane. SIGNIFICANCE AND IMPACT OF THE STUDY: The study provides for the first time the effects of OVEO and ROEO on morphology and physiological functions of noncultivable sessile cells of S. Enteritidis biofilms preformed on stainless steel surfaces.
Assuntos
Biofilmes/efeitos dos fármacos , Óleos Voláteis/farmacologia , Origanum/química , Óleos de Plantas/farmacologia , Rosmarinus/química , Salmonella enteritidis/efeitos dos fármacos , Salmonella enteritidis/crescimento & desenvolvimento , Salmonella enteritidis/fisiologia , Aço Inoxidável/análiseRESUMO
UNLABELLED: This study evaluated the impact of sodium dichloroisocyanurate (5, 10, 20, 30, 40, 50 and 250 mg l(-1) ) in wash water on transfer of Salmonella Typhimurium from contaminated lettuce to wash water and then to other noncontaminated lettuces washed sequentially in the same water. Experiments were designed mimicking the conditions commonly seen in minimally processed vegetable (MPV) processing plants in Brazil. The scenarios were as follows: (1) Washing one inoculated lettuce portion in nonchlorinated water, followed by washing 10 noninoculated portions sequentially. (2) Washing one inoculated lettuce portion in chlorinated water followed by washing five noninoculated portions sequentially. (3) Washing five inoculated lettuce portions in chlorinated water sequentially, followed by washing five noninoculated portions sequentially. (4) Washing five noninoculated lettuce portions in chlorinated water sequentially, followed by washing five inoculated portions sequentially and then by washing five noninoculated portions sequentially in the same water. Salm. Typhimurium transfer from inoculated lettuce to wash water and further dissemination to noninoculated lettuces occurred when nonchlorinated water was used (scenario 1). When chlorinated water was used (scenarios 2, 3 and 4), no measurable Salm. Typhimurium transfer occurred if the sanitizer was ≥10 mg l(-1) . Use of sanitizers in correct concentrations is important to minimize the risk of microbial transfer during MPV washing. SIGNIFICANCE AND IMPACT OF THE STUDY: In this study, the impact of sodium dichloroisocyanurate in the wash water on transfer of Salmonella Typhimurium from inoculated lettuce to wash water and then to other noninoculated lettuces washed sequentially in the same water was evaluated. The use of chlorinated water, at concentration above 10 mg l(-1) , effectively prevented Salm. Typhimurium transfer under several different washing scenarios. Conversely, when nonchlorinated water was used, Salm. Typhimurium transfer occurred in up to at least 10 noninoculated batches of lettuce washed sequentially in the same water.
Assuntos
Desinfetantes/farmacologia , Manipulação de Alimentos/métodos , Lactuca/microbiologia , Salmonella typhimurium/efeitos dos fármacos , Triazinas/farmacologia , Verduras/microbiologia , Brasil , Contagem de Colônia Microbiana , Escherichia coli O157/efeitos dos fármacos , Contaminação de Alimentos/análise , Microbiologia de Alimentos , Sorogrupo , Água , Microbiologia da ÁguaRESUMO
The kinetic inactivation parameters of four wild strains and two enterotoxigenic strains of Escherichia coli exposed to commercial calcium hypochlorite were determined. The four wild strains (1A, 3C, 4D and 8H) were isolated from lettuce bought in Sao Paulo (Brazil), and the two enterotoxigenic strains (TR69 and TR101) were originally isolated from human patients. Decimal reduction time 'D', for 10 mg L-1 available chlorine at pH 6.8, varied between 71.4 s for the wild strain 4D and 31.3 s for the toxigenic strain. The 'D' values obtained for wild strain 1A exposed to 5.0 mg L-1 available chlorine at pH 6.8 varied between 111.1 s and 41.7 s. The 'D' values obtained for E. coli strain TR69 exposed to 10 mg L-1 available chlorine varied from 15.2 s at pH 5.4 up to 83.3 s at pH 8.2. The use of the most resistant wild strain of E. coli as a biological standard assures maximal effectiveness in controlling water contamination by chlorination.