Qualidade microbiológicas de ostras (Crassostrea rhizophorae) e água de cultivo e suscetibilidade de Escherichia coli a óleo essencial de Lippia origanoides

Abstract

The intake of marine bivalve molluscs, raw or lightly cooked, is a common practice in all the coastal regions of Brazil. The consumption of these foods is associated with the emergence of Food Transmitted Diseases. Among the clams, oysters stand-by feature bioaccumulate particles present in the environment, leading to contamination by pathogenic microorganisms such as Escherichia coli. Thus, the aim of this study was to evaluate the microbiological quality of Crassostrea rhizophorae and cultivation water of Reserve Marine Extractive Bay Iguape – Bahia, phenotypically characterize E. coli isolated from these samples and check the OE antimicrobial action Lippia origanoides front isolated strains of oysters and standard strains of EHEC pathotypes samples ATCC (ATCC 43895), EPEC (ATCC CD O111ab), ETEC (ATCC 11229). Four samples were taken at three different points in the period January to April 2015. For analysis of the water used is the number of technical More Likely - NMP / 100 mL with series of five tubes in three dilutions. The determination of population of total coliforms (TC) and E. coli in Oysters was performed by rapid method of count Petrifilm ™ EC plates (3M Company). The essential oil of Lippia origanoides was obtained by hydrodistillation. To evaluate the antimicrobial activity was conducted microdilution test broth proposed by the CLSI (2003) with adaptations, to obtain determining the Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) of the essential oil studied. Water samples had a mean microbial count of 1.30 log NMP/100 mL for CT and 2.45 log NMP/100 mL, for thermotolerant coliforms, ranging from 0.83 to 2.08 log NMP/100 mL and from 0.66 to 6.80 log NMP/100 mL, respectively. The Oyster microbiological analysis showed CT count values from 0.95 to 4.76 log UFC/g and E. coli from 0.95 to 6.80 log UFC/g. Genotypic characterization of isolates identify the virulence gene stx/EHEC in 36.6 % (11/30) of the samples. None of the samples showed the virulence gene bfpA/ EPEC. The chemical composition analysis has revealed as major compound carvacrol (48%) followed by p-cymene (6.27%) and thymol (4.10%).The findings showed that the essential oil of Lippia origanoides has inhibitory action across all studied strains. The MIC for the isolated strains of oysters (Crassostrea rhizophorae) was 1.09 mg.mL-1, which is considered minimal bacteriostatic concentration. CBM to isolate the pickup point D was 1.09 mg.mL-1 and E. coli isolated from the growing points A and C were 4.37 mg.mL-1. The standard strains showed MIC and MBC of 1.09 mg.mL-1. The minimum bactericidal concentration was 1.09 to ETEC mg.mL-1 and EHEC and EPEC were 0.54 mg.mL-1. Microbiological results although they are in accordance with the standards established by international law, virulence gene identified in part of the samples suggests careful about consumption of oysters grown in this location. It is recommended the production of controlled oyster pollution, highlighting the continuous monitoring of the area and the quality of the production process of oysters. It is evident that the essential oil has been studied biotechnological potential for the development of antimicrobial to be used in the control of pathogenic bacteria.